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Objective: Diminish interleukin-1β (IL-1β) signaling in a model of primary osteoarthritis by RNA interference-based transcript reduction or receptor blockade, and quantify changes incurred on transcript expression of additional mediators.Methods: Knees of Hartley guinea pigs were collected at 120 and 180 days of age following injection with viral vectors (N = 4/treatment group/date) at 60 days. Two groups received either adeno-associated viral serotype 5 vector containing a knockdown sequence (TV), or adenoviral vector encoding for IL-1 receptor antagonist protein (Ad-IRAP); treatments were contrasted with opposite knees administered corresponding vector controls. A third group evaluated TV relative to saline-only injected knees. Chondropathy and immunohistochemistry findings were compared to untreated guinea pigs. Transcript expression levels in cartilage were calculated using the comparative CT (2(-ΔΔCT)) method and analyzed by one-way analysis of variance (ANOVA) with pairwise comparisons using Tukey 95% confidence intervals.Results: Vector transduction was confirmed at both harvest dates. TV and Ad-IRAP, relative to vector controls, significantly decreased IL-1β. Inflammatory mediators [tumor necrosis factor-α (TNF-α), IL-8, interferon-γ (IFN-γ)], and catabolic matrix metalloproteinase 13 (MMP13) were also decreased, while anabolic transforming growth factor-β1 (TGF-β1) was increased. IL-1β was also decreased by TV vs saline, with a decrease in MMP13 and increase TGF-β1; TNF-α, IL-8, and IFN-γ were transiently increased.Conclusions: This work confirmed that a reduction in IL-1β signaling was accomplished by either method, resulting in decreased expression of three inflammatory mediators and one catabolic agent, and increased expression of an anabolic molecule. Thus, evidence is provided that IL-1β serves a role in vivo in spontaneous osteoarthritis and that these translational tools may provide beneficial disease modification. [ABSTRACT FROM AUTHOR]

Objective: To ascertain a viral vector-based short hairpin RNA (shRNA) capable of reducing the interleukin-1β (IL-1β) transcript in osteoarthritis (OA)-prone chondrocytes and detect corresponding changes in the expression patterns of several critical disease mediators.Methods: Cultured chondrocytes from 2-month-old Hartley guinea pigs were screened for reduction of the IL-1β transcript following plasmid-based delivery of U6-driven shRNA sequences. A successful plasmid/shRNA knockdown combination was identified and used to construct an adeno-associated virus serotype 5 (AAV5) vector for further evaluation. Relative real-time reverse transcription polymerase chain reaction (RT-PCR) was used to quantify in vitro transcript changes of IL-1β and an additional nine genes following transduction with this targeting knockdown vector. To validate in vitro findings, this AAV5 vector was injected into one knee, while either an equivalent volume of saline vehicle (three animals) or non-targeting control vector (three animals) were injected into opposite knees. Fold differences and subsequent percent gene expression levels relative to control groups were calculated using the comparative CT (2(-ΔΔCT)) method.Results: Statistically significant decreases in IL-1β expression were achieved by the targeting knockdown vector relative to both the mock-transduced control and non-targeting vector control groups in vitro. Transcript levels of anabolic transforming growth factor-β (TGF-β) were significantly increased by use of this targeting knockdown vector. Transduction with this targeting AAV5 vector also significantly decreased the transcript levels of key inflammatory cytokines [tumor necrosis factor-α (TNF-α), IL-2, IL-8, and IL-12] and catabolic agents [matrix metalloproteinase (MMP)13, MMP2, interferon-γ (IFN-γ), and inducible nitrous oxide synthase (iNOS)] relative to both mock-transduced and non-targeting vector control groups. In vivo application of this targeting knockdown vector resulted in a >50% reduction (P=0.0045) or >90% (P=0.0001) of the IL-1β transcript relative to vehicle-only or non-targeting vector control exposed cartilage, respectively.Conclusions: Successful reduction of the IL-1β transcript was achieved via RNA interference (RNAi) techniques. Importantly, this alteration significantly influenced the transcript levels of several major players involved in OA pathogenesis in the direction of disease modification. Investigations to characterize additional gene expression changes influenced by targeting knockdown AAV5 vector-based diminution of the IL-1β transcript in vivo are warranted. [ABSTRACT FROM AUTHOR]

Objective: To provide a comprehensive immunohistochemical (IHC) map of the temporal expression and tissue distribution of interleukin-1β (IL-1β) through progression of osteoarthritis (OA) in two strains of guinea pigs with varying propensity for spontaneous knee joint disease.Methods: OA-prone Hartley and OA-resistant Strain 13 guinea pigs were collected at 60, 120, 180, 240, 360, and 480 days of age (N=4 animals per strain per date). IHC was performed on whole joint preparations; the distribution of IL-1β expression on coronal sections was mapped, semi-quantitatively scored, and correlated to OA grade using Mankin criteria with guinea pig-specific modifications. OA and IHC indices were compared among times and between strains using the Kruskal-Wallis one-way analysis of variance by ranks followed by Dunn's post test.Results: OA indices for both strains increased from 60 to 480 days of age; a statistically higher score (P ≤ 0.01) was found in Hartley animals at 180, 240, 360, and 480 days. At 60 days of age, IL-1β expression was detected in cartilage, menisci, synovium, and subchondral bone in both strains. Persistent and statistically increased (P<0.05) IL-1β expression was found in these same tissues in Hartley animals at 120 and 180 days, while Strain 13 animals demonstrated a significant reduction in positive immunostaining. Statistical differences in IHC indices between strains beyond 240 days of age were restricted to synovium (days 240 and 480) and subchondral bone (days 360 and 480).Conclusions: As expected, histologic OA proceeded in an accelerated manner in Hartley animals relative to Strain 13 animals. The OA-prone strain did not demonstrate reduced IL-1β expression during adult maturity as occurred in the OA-resistant strain, and this persistent expression may have corresponded to early incidence of OA. Future interventional studies are warranted to explore whether dysregulation of IL-1β expression may contribute to premature onset of spontaneous disease in the Hartley guinea pig. [ABSTRACT FROM AUTHOR]

Background: Low load exercise training with blood flow restriction (BFR) has become increasingly used by human physical therapists to prescribe controlled exercise following orthopaedic injury; its effects on the equine superficial digital flexor tendon (SDFT), however, are unknown., Objective: To investigate outcomes of pressure specific BFR walking exercise on uninjured equine SDFT biomechanics and histomorphology., Study Design: Controlled in vivo experiment., Methods: Four forelimbs of four horses were exposed to 40 BFR-walk sessions (10-min interval walking) on a treadmill over a 56-day study period with their contralateral forelimbs serving as untreated controls. Similarly, four forelimbs of four control horses were exposed to 40 sham cuff walk sessions. On study Day 56, all horses (n = 8) were humanely euthanised and forelimb SDFTs underwent non-destructive biomechanical testing and corresponding histomorphological analysis. Significance in biomechanical parameters between treatment groups was analysed using a mixed-effects ANOVA with Tukey's post-hoc tests., Results: Statistically significant differences in SDFT stiffness for both first (p = 0.02) and last cycles (p = 0.03) were appreciated within the BFR treated group only, with BFR exposed forelimbs being significantly stiffer than the contralateral unexposed forelimbs. When normalised to cross-sectional area, no significant differences were appreciated among treatment groups in elastic modulus for the first (p = 0.5) or last cycles (p = 0.4). No histological differences were appreciated among treatment groups according to Bonar, Movin, or musculotendinous junction evaluation criteria., Main Limitations: Short-term comparisons were performed in a small sample population without correlation to performance outcome measures. Optimal occlusion percentages and walk protocols remain unknown., Conclusions: This study demonstrated no negative impact of BFR on mechanical strength of the equine SDFT; however, evidence suggests that BFR results in increased tendon stiffness based on biomechanical testing and subsequent calculations. No consistent detrimental histomorphological changes were seen., (© 2024 EVJ Ltd.)

Background: Biochemistry analyzers, which utilize indirect potentiometry, are used to determine serum electrolyte concentrations in dogs. Artifactual increases or decreases in these electrolyte concentrations can be caused by alterations in the serum water fraction (SWF). Severe hypo- and hyperproteinemia cause changes in SWF, which can then result in incorrectly reported serum sodium concentrations., Objectives: The goals of this study were to determine an average actual SWF (SWF ACTUAL ) in dogs and establish formulae to correct serum sodium concentration measured by indirect potentiometry in hypo- and hyperproteinemic patients., Methods: Serum samples from 115 canine patients were analyzed for electrolytes measured by both indirect and direct potentiometry. Total protein, albumin, triglycerides, and cholesterol were also determined. Each serum sample was then lyophilized to determine SWF ACTUAL . A canine-specific formula to estimate SWF (SWF EST-CAN ) was developed using a multivariable linear model and compared with the human-estimated formula (SWF EST-HUM )., Results: The mean SWF ACTUAL in this population of dogs was 92.7%, which was significantly different (p < .0001) than the mean (95.1%) calculated using SWF EST-HUM . The formula derived from SWF EST-CAN recapitulated SWF ACTUAL more accurately than SWF EST-HUM . Based on a slope closer to 1.0, the corrected sodium concentrations calculated using the canine formula correlated marginally better with the serum sodium measured by direct potentiometry than those calculated using the human formula., Conclusions: Applications of correction formulae are expected to limit the misinterpretation of electrolyte data from indirect potentiometry when altered SWF occurs. A case example of the potential utility of these correction formulae is presented., (© 2025 The Author(s). Veterinary Clinical Pathology published by Wiley Periodicals LLC on behalf of American Society for Veterinary Clinical Pathology.)

Objective: To investigate indicators of mobility, inflammation, and cartilage remodeling in Dunkin-Hartley guinea pigs (Cavia porcellus) treated with manual acupuncture compared to 2 different comparator acupuncture groups., Methods: 12-month-old male Hartleys were randomly assigned to 1 of 3 in vivo experimental groups that received manual acupuncture, needle sheath taps on corresponding acupoints, or off-point acupuncture. Treatments were performed under isoflurane once weekly for 3 weeks, and open-field enclosure monitoring was performed at the same frequency. After final treatments, all animals were euthanized, blood was collected for inflammatory marker analysis, and tissues were collected for histology, immunohistochemistry, and transcript expression analysis., Results: 18 animals were involved: 6 per experimental group. Serum concentrations of complement component 3 and prostaglandin E2 were significantly decreased in the acupuncture group (P < .05). Muscle from acupoint stomach-36 had 6 gene transcripts with altered expressions in the manual acupuncture group compared to comparators. From cartilage/menisci, manual acupuncture resulted in the downregulation of 13 gene transcripts. Nerve growth factor (NGF) immunostaining in all 3 layers of articular cartilage of the medial tibial plateau was greater in the manual acupuncture group relative to the comparator groups. There were no differences in enclosure monitoring parameters or histologic grading., Conclusions: Appreciable changes in voluntary mobility, behavioral or serum biochemical parameters, or stifle histological structure were not seen. Differences in serum inflammatory proteins, the gene expression of cartilage-remodeling transcripts, and NGF protein concentrations in cartilage were elucidated., Clinical Relevance: The short duration of manual acupuncture showed the initiation of beneficial regenerative and remodeling processes.

Purpose/aim: Metabolic disorders are risk factors for rotator cuff injuries, which suggests that the rotator cuff is sensitive to local metabolic fluctuations. However, the link between the metabolic microenvironment and pathologic features of acute tear versus chronic degeneration is currently unknown. The overarching goal of this study was to evaluate alterations in tendon metabolite profiles following acute tear or chronic degeneration of the rotator cuff. We hypothesized that injury types (acute tear vs. chronic degeneration) would result in distinct metabolite profiles relative to clinically unaffected tendon controls., Materials and Methods: We utilized untargeted metabolomics to identify pathways that were altered at the time of rotator cuff repair (RCR; acute tear) or reverse total shoulder arthroplasty (rTSA; chronic degeneration) relative to total shoulder arthroplasty controls (TSA; tendon clinically unaffected)., Results: Acute tears to the rotator cuff were associated with an overall decrease in tendon metabolites. This global decrease was primarily associated with glycolic acid and decreased tricarboxylic acid (TCA) cycle activity. Conversely, chronic tendon specimens from patients undergoing rTSA showed an overall increase in metabolites. Most notably, chronic injury was associated with increased levels of multiple amino acids including alanine, aspartate, lysine, and proline., Conclusions: Overall, this study demonstrates that distinct metabolite profiles are associated with injury types, and that therapeutic strategies should address both cellular and matrix components regardless of injury induction. The specific pathways identified paired with validated, established, treatment methods may serve as novel therapeutic targets for patients who suffer from rotator cuff injuries.

Aim: Alzheimer's disease (AD) is the most common form of dementia. However, while 150+ animal models of AD exist, drug translation from preclinical models to humans for treatment usually fails. One factor contributing to low translation is likely the absence of neurodegenerative models that also encompass the multi-morbidities of human aging. We previously demonstrated that, in comparison to the PigmEnTed (PET) guinea pig strain which models "typical" brain aging, the Hartley strain develops hallmarks of AD like aging humans. Hartleys also exhibit age-related impairments in cartilage and skeletal muscle. Impaired mitochondrial respiration is one driver of both cellular aging and AD. In humans with cognitive decline, diminished skeletal muscle and brain respiratory control occurs in parallel. We previously reported age-related declines in skeletal muscle mitochondrial respiration in Hartleys. It is unknown if there is concomitant mitochondrial dysfunction in the brain., Methods: Therefore, we assessed hippocampal mitochondrial respiration in 5- and 12-month Hartley and PET guinea pigs using high-resolution respirometry., Results: At 12 months, PETs had higher complex I supported mitochondrial respiration paralleling their increase in body mass compared to 5 months PETs. Hartleys were also heavier at 12 months compared to 5 months but did not have higher complex I respiration. Compared to 5 months Hartleys, 12 months Hartleys had lower complex I mitochondrial efficiency and compensatory increases in mitochondrial proteins collectively suggesting mitochondrial dysfunction with age., Conclusions: Therefore, Hartleys might be a relevant model to test promising therapies targeting mitochondria to slow brain aging and AD progression., (© 2024 The Author(s). Acta Physiologica published by John Wiley & Sons Ltd on behalf of Scandinavian Physiological Society.)

Background: Several tissues contribute to the onset and advancement of knee osteoarthritis (OA). One tissue type that is worthy of closer evaluation, particularly in the context of sex, is the infrapatellar fat pad (IFP). We previously demonstrated that removal of the IFP had short-term beneficial effects for a cohort of male Dunkin-Hartley guinea pigs. The present project was designed to elucidate the influence of IFP removal in females of this OA-prone strain. It was hypothesized that resection of the IFP would reduce the development of OA in knees of a rodent model predisposed to the disease., Methods: Female guinea pigs (n=16) were acquired at an age of 2.5 months. Surgical removal of the IFP and associated synovium complex (IFP/SC) was executed at 3 months of age. One knee had the IFP/SC resected; a comparable sham surgery was performed on the contralateral knee. All animals were subjected to voluntary enclosure monitoring and dynamic weight-bearing, as well as compulsory treadmill-based gait analysis monthly; baseline data was collected prior to surgery. Guinea pigs were euthanized at 7 months. Knees from eight animals were evaluated via histology, mRNA expression, and immunohistochemistry (IHC); knees from the remaining eight animals were allocated to microcomputed tomography (microCT), biomechanical analyses (whole joint testing and indentation relaxation testing), and atomic absorption spectroscopy (AAS)., Results: Fibrous connective tissue (FCT) replaced the IFP/SC. Mobility/gait data indicated that unilateral IFP/SC removal did not affect bilateral hindlimb movement. MicroCT demonstrated that osteophytes were not a significant feature of OA in this sex; however, trabecular thickness (TbTh) in medial femorae decreased in knees containing the FCT. Histopathology scores were predominantly influenced by changes in the lateral tibia, which demonstrated that histologic signs of OA were increased in knees containing the native IFP/SC versus those with the FCT. Similarly, indentation testing demonstrated higher instantaneous and equilibrium moduli in the lateral tibial articular cartilage of control knees with native IFPs. AAS of multiple tissue types associated with the knee revealed that zinc was the major trace element influenced by removal of the IFP/SC., Conclusions: Our data suggest that the IFP/SC is a significant component driving knee OA in female guinea pigs and that resection of this tissue prior to disease has short-term benefits. Specifically, the formation of the FCT in place of the native tissue resulted in decreased cartilage-related OA changes, as demonstrated by reduced Osteoarthritis Research Society International (OARSI) histology scores, as well as changes in transcript, protein, and cartilage indentation analyses. Importantly, this model provides evidence that sex needs to be considered when investigating responses and associated mechanisms seen with this intervention., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://atm.amegroups.com/article/view/10.21037/atm-23-1886/coif). The authors have no conflicts of interest to declare., (2024 Annals of Translational Medicine. All rights reserved.)

Age-related osteoarthritis (OA) is a degenerative joint disease characterized by pathological changes in nearly every intra- and peri-articular tissue that contributes to disability in older adults. Studying the etiology of age-related OA in humans is difficult due to an unpredictable onset and insidious nature. A barrier in developing OA modifying therapies is the lack of translational models that replicate human joint anatomy and age-related OA progression. The purpose of this study was to determine whether the common marmoset is a faithful model of human age-related knee OA. Semi-quantitative microCT scoring revealed greater radiographic OA in geriatric versus adult marmosets, and the age-related increase in OA prevalence was similar between marmosets and humans. Quantitative assessments indicate greater medial tibial cortical and trabecular bone thickness and heterogeneity in geriatric versus adult marmosets which is consistent with an age-related increase in focal subchondral bone sclerosis. Additionally, marmosets displayed an age-associated increase in synovitis and calcification of the meniscus and patella. Histological OA pathology in the medial tibial plateau was greater in geriatric versus adult marmosets driven by articular cartilage damage, proteoglycan loss, and altered chondrocyte cellularity. The age-associated increase in medial tibial cartilage OA pathology and meniscal calcification was greater in female versus male geriatric marmosets. Overall, marmosets largely replicate human OA as evident by similar 1) cartilage and skeletal morphology, 2) age-related progression in OA pathology, and 3) sex differences in OA pathology with increasing age. Collectively, these data suggest that the common marmoset is a highly translatable model of the naturally occurring, age-related OA seen in humans., (© 2024. The Author(s), under exclusive licence to American Aging Association.)

Objective: Pharmacologic inhibition of the mechanistic target of rapamycin (mTOR) can attenuate experimental osteoarthritis (OA) in young, male preclinical models. However, the potential of mTOR inhibition as a therapeutic mechanism for OA remains unknown. The goal of this study was to determine if mTOR-inhibition by oral rapamycin can modify OA pathology in the common marmoset, a translational model of age-associated OA., Methods: microCT and histopathologic assessments of the knee were performed on formalin-fixed hindlimbs obtained from common marmosets treated with oral rapamycin (n=24; 1mg/kg/day) or parallel control group (n=41). Rapamycin started at 9.2±3.0 years old and lasted until death (2.1±1.5 years). In a subset of marmosets, contralateral hind limbs were collected to determine mTOR signaling in several joint tissues., Results: Rapamycin decreased P-RPS6 Ser235/36 and increased P-Akt2 Ser473 in cartilage, meniscus, and infrapatellar fat pad, suggesting inhibition of mTORC1 but not mTORC2 signaling. Rapamycin-treated marmosets had lower lateral synovium score versus control but there was no difference in the age-related increase in microCT or cartilage OA scores. Subchondral bone thickness and thickness variability were not different with age but were lower in rapamycin-treated geriatric marmosets, which was largely driven by females. Rapamycin also tended to worsen age-related meniscus calcification in female marmosets., Conclusion: Oral rapamycin attenuated mTORC1 signaling and may have caused feedback activation of mTORC2 signaling in joint tissues. Despite modifying site-specific aspects of synovitis, rapamycin did not modify the age-associated increase in OA in geriatric marmosets. Conversely, rapamycin may have had deleterious effects on meniscus calcification and lateral tibia subchondral bone, primarily in geriatric female marmosets.

Nuclear factor-erythroid 2-related factor-2 (Nrf2) is a transcription factor that serves as a master regulator of anti-inflammatory agents, phase I xenobiotic, and phase II antioxidant enzymes, all of which provide a cytoprotective role during disease progression. We hypothesized that oral administration of a purported phytochemical Nrf2-activator, PB125 ® , would increase long bone strength in aging Hartley guinea pigs, a model prone to musculoskeletal decline. Male (N = 56) and female (N = 56) guinea pigs were randomly assigned to receive daily oral treatment with either PB125 ® or vehicle control. Animals were treated for a consecutive 3-months (starting at 2-months of age) or 10-months (starting at 5-months of age) and sacrificed at 5-months or 15-months of age, respectively. Outcome measures included: (1) ANY-maze™ enclosure monitoring, (2) quantitative microcomputed tomography, and (3) biomechanical testing. Treatment with PB125 ® for 10 months resulted in increased long bone strength as determined by ultimate bending stress in female Hartley guinea pigs. In control groups, increasing age resulted in significant effects on geometric and structural properties of long bones, as well as a trending increase in ultimate bending stress. Furthermore, both age and sex had a significant effect on the geometric properties of both cortical and trabecular bone. Collectively, this work suggests that this nutraceutical may serve as a promising target and preventive measure in managing the decline in bone mass and quality documented in aging patients. Auxiliary to this main goal, this work also capitalized upon 5 and 15-month-old male and female animals in the control group to characterize age- and sex-specific differences on long bone geometric, structural, and material properties in this animal model., (© 2023. The Author(s) under exclusive licence to Biomedical Engineering Society.)

Objective: To define reference intervals (RIs) for arterial blood gas (aBG) measurements in healthy, nonsedated, dolichocephalic, and mesocephalic (nonbrachycephalic) dogs at approximately 1,535 m above sea level and compare these findings with healthy, nonsedated, brachycephalic dogs living at the same altitude., Animals: 120 adult nonbrachycephalic dogs and 20 adult brachycephalic dogs., Methods: Cases were prospectively enrolled from October 2021 to June 2022. Dogs were enrolled from the community or after presentation for wellness examinations or minor injuries including lacerations, nail injuries, and lameness. Physical examinations and systolic blood pressure (sBP) measurements were obtained before blood sample collection. Arterial blood was collected from the dorsal pedal artery or femoral artery. After data collection, brachycephalic dogs underwent pre- and postexercise tolerance assessments., Results: The mean and RI values for arterial pH (7.442; 7.375 to 7.515), partial pressure of oxygen in arterial blood (Pao2; 78.3; 59.2 to 92.7 mm Hg), partial pressure of carbon dioxide in arterial blood (Paco2; 28.0; 21.5 to 34.4 mm Hg), saturation of arterial oxygen (Sao2; 98.4; 84.3% to 101.4%), HCO3 (18.9; 14.9 to 22.4 mmol/L), concentration of total hemoglobin (ctHb; 17.5; 13.4 to 21.1 g/dL), and sBP (133; 94 to 180 mm Hg) were established for healthy nonbrachycephalic dogs at 1,535-m altitude. All aBG measurements were statistically and clinically different from those previously reported for dogs at sea level. Brachycephalic dogs had significantly lower Pao2 and Sao2 (P = .0150 and P = .0237, respectively) and significantly higher ctHb (P = .0396) compared to nonbrachycephalic dogs acclimatized to the same altitude; the nonbrachycephalic RIs were not transferable to the brachycephalic dogs for Pao2., Clinical Relevance: This study represents the first collation of aBG measurements for healthy nonbrachycephalic dogs acclimatized to an altitude of 1,535 m. Additionally, this study identified differences in arterial oxygenation measurements between brachycephalic and nonbrachycephalic dogs. RIs in brachycephalic dogs need to be established.

Purpose/aim: Cartilage injury and subsequent osteoarthritis (OA) are debilitating conditions affecting millions worldwide. As there are no cures for these ailments, novel therapies are needed to suppress disease pathogenesis. Given that joint injuries are known to produce damage-associated molecular patterns (DAMPs), our central premise is that the Toll-like receptor 4 (TLR4) pathway is a principal driver in the early response to cartilage damage and subsequent pathology. We postulate that TLR4 activation is initiated/perpetuated by DAMPs released following joint damage. Thus, antagonism of the TLR4 pathway immediately after injury may suppress the development of joint surface defects., Materials and Methods: Two groups were utilized: (1) 8-week-old, male C57BL6 mice treated systemically with a known TLR4 antagonist and (2) mice injected with vehicle control. A full-depth cartilage lesion on the midline of the patellofemoral groove was created in the right knee of each mouse. The left knee was used as a sham surgery control. Gait changes were evaluated over 4 weeks using a quantitative gait analysis system. At harvest, knee joints were processed for pathologic assessment, Nanostring® transcript expression, and immunohistochemistry (IHC)., Results: Short-term treatment with a TLR4 antagonist at 14-days significantly improved relevant gait parameters; improved cartilage metrics and modified Mankin scores were also seen. Additionally, mRNA expression and IHC showed reduced expression of inflammatory mediators in animals treated with the TLR4 antagonist., Conclusions: Collectively, this work demonstrates that systemic treatment with a TLR4 antagonist is protective to further cartilage damage 14-days post-injury in a murine model of induced disease.

Overhead enclosure monitoring provides objective quantitative mobility measurements for animals undergoing open-field testing. Notably, protocols for testing optimization have been minimally established for the guinea pig. It is unknown whether (a) repeated exposure, (b) time-of-day, or (c) length of testing duration influence outcome parameters. We hypothesized that guinea pigs would display decreased activity following repeated exposure to the open field; heightened activity during the earliest testing period; and that 10 min would be adequate for data collection. The study was conducted in two separate phases to distinguish between enclosure habituation and time-of-day effects, respectively. Two cohorts of male Dunkin Hartley guinea pigs were allowed voluntary movement in an open-field enclosure for 14 min to quantify mobility outcomes, including total distance traveled, total time mobile, average speed while mobile, and total time spent in the shelter. For both phases, testing occurred at four different times of day, and overhead monitoring software was programmed to divide the total testing duration into 2-min bins. Habituation phase results showed time mobile and distance traveled were influenced significantly by repeat exposure, as animals were most active during the first testing event. Time-of-day phase animals spent significantly more time mobile during the earliest testing period. Interestingly, significant differences were observed across 2-min bins for the time-of-day phase but not during the habituation phase. Specifically, progressively decreased ambulatory activity was observed as testing duration increased. Thus, habituation and time-of-day should be accounted for when possible. Finally, a trial period greater than 10 min may not yield additional data., Competing Interests: Declaration of conflicting interestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Background: Despite the high prevalence of osteoarthritis (OA), there remains a need for additional therapeutic options. Cellular therapies with minimally manipulated cells such as bone marrow aspirate concentrates (BMAC) are increasingly popular in the U.S. but clear-cut evidence of efficacy has not been established. In theory, BMAC injections provide a source of stromal cells to stimulate healing in OA and ligamentous injuries; however, BMAC injections are also often associated with inflammation, short-term pain, and mobility impairment. Given that blood is known to trigger inflammation in joints, we hypothesized that removing erythrocytes [red blood cells (RBCs)] from BMAC preparations prior to intra-articular injection would improve efficacy for OA treatment., Methods: To test this hypothesis, BMAC was collected from the bone marrow of mice. Three treatment groups were pursued: (I) untreated; (II) BMAC; or (III) BMAC depleted of RBCs by lysis. Product was injected into the femorotibial joint of mice 7 days after OA had been induced by destabilization of the medial meniscus (DMM). To assess the impact of treatment on joint function, individual cage monitoring (ANY-maze TM ) and Digigait treadmill-based analyses were performed over 4 weeks. At study completion, joint histopathology was assessed and immune transcriptomes within joint tissues were compared using a species-specific NanoString panel., Results: Significant improvements in activity, gait parameters, and histology scores were seen in animals receiving RBC-depleted BMAC compared to untreated mice; animals treated with non-depleted BMAC did not demonstrate this same extent of consistent significant improvement. Transcriptomic analysis of joint tissues revealed significant upregulation of key anti-inflammatory genes, including interleukin-1 receptor antagonist (IRAP), in mice treated with RBC-depleted BMAC compared to animals treated with non-RBC depleted BMAC., Conclusions: These findings indicate that RBC depletion in BMAC prior to intra-articular injection improves treatment efficacy and reduces joint inflammation compared to BMAC., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://atm.amegroups.com/article/view/10.21037/atm-22-4256/coif). LMP reports that support for this work was provided by Animal Health and Disease (No. 19HMFPXXXXG039150001) from the USDA National Institute of Food and Agriculture, Carolyn Quan and Porter Bennett, NIH/NCATS CTSA 5TL1TR002533-02, NIH 5T32OD010437-19, and Colorado State University Veterinary Summer Scholars Program USDA Animal Health and Disease Fellowship. LMP reports that a provisional patent has been filed covering the fractionated bone marrow aspirate product described herein. LMP serves as a member of the advisory team for EqCell Inc., and has stock options in EqCell Inc. LC reports that a provisional patent has been filed covering the fractionated bone marrow aspirate product described herein. SD reports that a provisional patent has been filed covering the fractionated bone marrow aspirate product described herein and that he is a cofounder (without revenue) of a virtual startup company developing an unrelated cellular therapeutic product for treatment of chronic wound infections. The other authors have no conflicts of interest to declare., (2023 Annals of Translational Medicine. All rights reserved.)

Background: Lactate measurements have been utilized as diagnostic and prognostic tools for a variety of veterinary species. Reference intervals for lactate have not been published or validated in guinea pigs., Methods: Whole blood from 48 anesthetized laboratory guinea pigs (46 Dunkin Hartley [38 males, eight females]; two Strain 13 [two males]) was analyzed using two point of care instruments (iSTAT and Lactate Plus). There were two consecutive timepoints on the iSTAT (iSTAT time 1 and time 2) and three consecutive timepoints on the Lactate Plus (Lactate Plus time 1, time 2, and time 3)., Results: There was agreement with no constant or proportional bias between the two instruments compared at equivalent timepoints (iSTAT time 1 and Lactate Plus time 3) as determined by Bland-Altman (bias: -0.19; 95% LoA: -0.55 to 0.16) and Deming linear regression analyses (slope: 1.092, 95% confidence intervals (CI): -0.9 to 1.29; y-intercept: 0.09, 95% CI: -0.12 to 0.30). Reference intervals for iSTAT time 1 were 0.49 to 1.83 mmol/L and Lactate Plus time 1 were 0.60 to. 2.2 mmol/L. There was a significant increase in lactate values from iSTAT time 1 to iSTAT time 2 and from Lactate Plus time 1 to Lactate Plus time 3., Conclusions and Clinical Relevance: This study found strong agreement between the point of care instruments. Reference intervals for lactate for both the iSTAT and Lactate Plus instruments were similar to canine and feline intervals. Analysis should occur within 5 minutes of sample collection. Future work should assess lactate as a prognostic indicator in guinea pigs., Competing Interests: Declaration of competing interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Impaired mitochondrial function and disrupted proteostasis contribute to musculoskeletal dysfunction. However, few interventions simultaneously target these two drivers to prevent musculoskeletal decline. Nuclear factor erythroid 2-related factor 2 (Nrf2) activates a transcriptional programme promoting cytoprotection, metabolism, and proteostasis. We hypothesized daily treatment with a purported Nrf2 activator, PB125, in Hartley guinea pigs, a model of musculoskeletal decline, would attenuate the progression of skeletal muscle mitochondrial dysfunction and impaired proteostasis and preserve musculoskeletal function. We treated 2- and 5-month-old male and female Hartley guinea pigs for 3 and 10 months, respectively, with the phytochemical compound PB125. Longitudinal assessments of voluntary mobility were measured using Any-Maze TM open-field enclosure monitoring. Cumulative skeletal muscle protein synthesis rates were measured using deuterium oxide over the final 30 days of treatment. Mitochondrial oxygen consumption in soleus muscles was measured using high resolution respirometry. In both sexes, PB125 (1) increased electron transfer system capacity; (2) attenuated the disease/age-related decline in coupled and uncoupled mitochondrial respiration; and (3) attenuated declines in protein synthesis in the myofibrillar, mitochondrial and cytosolic subfractions of the soleus. These effects were not associated with statistically significant prolonged maintenance of voluntary mobility in guinea pigs. Collectively, treatment with PB125 contributed to maintenance of skeletal muscle mitochondrial respiration and proteostasis in a pre-clinical model of musculoskeletal decline. Further investigation is necessary to determine if these documented effects of PB125 are also accompanied by slowed progression of other aspects of musculoskeletal dysfunction. KEY POINTS: Aside from exercise, there are no effective interventions for musculoskeletal decline, which begins in the fifth decade of life and contributes to disability and cardiometabolic diseases. Targeting both mitochondrial dysfunction and impaired protein homeostasis (proteostasis), which contribute to the age and disease process, may mitigate the progressive decline in overall musculoskeletal function (e.g. gait, strength). A potential intervention to target disease drivers is to stimulate nuclear factor erythroid 2-related factor 2 (Nrf2) activation, which leads to the transcription of genes responsible for redox homeostasis, proteome maintenance and mitochondrial energetics. Here, we tested a purported phytochemical Nrf2 activator, PB125, to improve mitochondrial function and proteostasis in male and female Hartley guinea pigs, which are a model for musculoskeletal ageing. PB125 improved mitochondrial respiration and attenuated disease- and age-related declines in skeletal muscle protein synthesis, a component of proteostasis, in both male and female Hartley guinea pigs., (© 2022 The Authors. The Journal of Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society.)

Objective: To advance the understanding of how alterations in exercise speed and grade (flat vs 17° incline or decline) affect the quality of tendon healing, and to determine if a biomarker relationship exists between serum levels of a ColX breakdown product (CXM) and animals exposed to treadmill running protocols., Animals: 35 male mice (C57BL/6J), 8 weeks of age., Procedures: Mice were preconditioned on a treadmill for 14 days. Tendinopathy was then induced by 2 intra-tendinous TGFβ1 injections followed by randomization into 7 exercise groups. Exercise capacity and objective gait analysis were measured weekly. Mice were euthanized and histopathologic analysis and evaluation of serum CXM levels were performed. Statistics were conducted using a 2-way ANOVA (exercise capacity), Mixed Effects Model (gait analysis, effect of preconditioning), and 1-way ANOVA (gait analysis, the effect of injury, and rehabilitation normalized to baseline; CXM serum analysis), all with Tukey post hoc tests and significance set to P < .05., Results: Exercise at a fast-flat speed demonstrated inferior tendinopathic healing at the cellular level and impaired stance braking abilities, which were compensated for by increased propulsion. Mice exposed to exercise (at any speed or grade) demonstrated higher systemic levels of CXM than those that were cage rested. However, no ColX immunostaining was observed in the Achilles tendon or calcaneal insertion., Clinical Relevance: Exercise at a fast speed and in absence of eccentric loading components (incline or decline) demonstrated inferior tendinopathic healing at the cellular level and impaired braking abilities that were compensated for by increased propulsion.

Osteoarthritis (OA) is a leading cause of morbidity among aging populations, yet symptom and/or disease-modification remains elusive. Adipose-derived mesenchymal stromal cells (adMSCs) have demonstrated immunomodulatory and anti-inflammatory properties that may alleviate clinical signs and interrupt disease onset and progression. Indeed, multiple manuscripts have evaluated intra-articular administration of adMSCs as a therapeutic; however, comparatively few evaluations of systemic delivery methods have been published. Therefore, the aim of this study was to evaluate the short-term impact of intravenous (IV) delivery of allogeneic adMSCs in an established model of spontaneous OA, the Hartley guinea pig. Animals with moderate OA received once weekly injections of 2 × 10 6 adMSCs or vehicle control for 4 weeks in peripheral veins; harvest occurred 2 weeks after the final injection. Systemic administration of adMSCs resulted in no adverse effects and was efficacious in reducing clinical signs of OA (as assessed by computer-aided gait analysis) compared to control injected animals. Further, there were significant decreases in key inflammatory mediators (including monocyte chemoattractant protein-1, tumor necrosis factor, and prostaglandin E 2 ) both systemically (liver, kidney, and serum) and locally in the knee (joint tissues and synovial fluid) in animals treated with IV adMSCs relative to controls (as per enzyme-linked immunosorbent assay and/or immunohistochemistry, dictated by tissue sample). Thus, systemic administration of adMSCs by IV injection significantly improved gait parameters and reduced both systemic and intra-articular inflammatory mediators in animals with OA. These findings demonstrate the potential utility of alternative delivery approaches for cellular therapy of OA, particularly for patients with multiple affected joints., (© 2022 The Authors. Journal of Orthopaedic Research® published by Wiley Periodicals LLC on behalf of Orthopaedic Research Society.)

The anterior cruciate ligament (ACL) is the most commonly injured knee ligament. Surgical reconstruction is the gold standard treatment for ACL ruptures, but 20-50% of patients develop post-traumatic osteoarthritis (PTOA). ACL rupture is thus a well-recognized etiology of PTOA; however, little is known about the initial relationship between ligamentous injury and subsequent PTOA. The goals of this project were to: (1) develop both partial and full models of mid-substance ACL rupture in male and female mice using non-invasive mechanical methods by means of tibial displacement; and (2) to characterize early PTOA changes in the full ACL rupture model. A custom material testing system was utilized to induce either partial or full ACL rupture by means of tibial displacement at 1.6 or 2.0 mm, respectively. Mice were euthanized either (i) immediately post-injury to determine rupture success rates or (ii) 14 days post-injury to evaluate early PTOA progression following full ACL rupture. Our models demonstrated high efficacy in inciting either full or partial ACL rupture in male and female mice within the mid-substance of the ACL. These tools can be utilized for preclinical testing of potential therapeutics and to further our understanding of PTOA following ACL rupture., (© 2022. The Author(s) under exclusive licence to Biomedical Engineering Society.)

Background: The infrapatellar fat pad (IFP) is the largest adipose deposit in the knee; however, its contributions to the homeostasis of this organ remain undefined. To determine the influence of the IFP and its associated synovium (IFP/synovium complex or IFP/SC) on joint health, this study evaluated the progression of osteoarthritis (OA) following excision of this unit in a rodent model of naturally-occurring disease., Methods: Male Dunkin-Hartley guinea pigs (n=18) received surgical removal of the IFP in one knee at 3 months of age; contralateral knees received sham surgery as matched internal controls. Mobility and gait assessments were performed prior to IFP/SC removal and monthly thereafter. Animals were harvested at 7 months of age. Ten set of these knees were processed for microcomputed tomography (microCT), histopathology, transcript expression analyses, and immunohistochemistry (IHC); 8 sets of knees were dedicated to microCT and biomechanical testing (material properties of knee joints tissues and anterior drawer laxity)., Results: Fibrous connective tissue (FCT) developed in place of the native adipose depot. Gait demonstrated no significant differences between IFP/SC removal and contralateral hindlimbs. MicroCT OA scores were improved in knees containing the FCT. Quantitatively, IFP/SC-containing knees had more osteophyte development and increased trabecular volume bone mineral density (vBMD) in femora and tibiae. Histopathology confirmed maintenance of articular cartilage structure, proteoglycan content, and chondrocyte cellularity in FCT-containing knees. Transcript analyses revealed decreased expression of adipose-related molecules and select inflammatory mediators in FCTs compared to IFP/SCs. This was verified via IHC for two key inflammatory agents. The medial articular cartilage in knees with native IFP/SCs showed an increase in equilibrium modulus, which correlated with increased amounts of magnesium and phosphorus., Discussion/conclusion: Formation of the FCT resulted in reduced OA-associated changes in both bone and cartilage. This benefit may be associated with: a decrease in inflammatory mediators at transcript and protein levels; and/or improved biomechanical properties. Thus, the IFP/SC may play a role in the pathogenesis of knee OA in this strain, with removal prior to disease onset appearing to have short-term benefits., (© 2022. The Author(s).)

Objective: Iron accumulation is emerging as a player in aging-related disorders due to its propensity for generating reactive oxygen species (ROS). Studies investigating the role of iron in the pathogenesis of primary osteoarthritis (OA) are limited. We designed a proof-of-principle study to determine the effect of systemic iron deficiency, via an iron deficient diet, on knee OA in an animal model., Methods: Twelve-week-old male Hartley guinea pigs received the standard diet (n = 6) or a diet devoid of iron (n = 6) for 19-weeks. Iron levels were determined in the serum, liver, and articular cartilage. Knees were collected to assess structural changes related to OA (microcomputed tomography, histopathology). Immunohistochemistry was performed to evaluate the presence and distribution of a disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS4) and ROS-driven 4-hydroxynonenal (4-HNE)-induced protein adducts. Transcript expression was also assessed., Results: Relative to control animals, an iron deficient diet reduced the concentration of this mineral in serum, liver, and articular cartilage. Iron deficient animals had lower histologic OA scores; decreased subchondral bone mineral density was also noted. This reduction in knee joint pathology was accompanied by a decrease in: ADAMTS4 in synovium; and 4-HNE protein adducts from lipid peroxidation in both the menisci and articular cartilage of iron deficient animals. Expression of iron-related genes in these tissues was also altered in treated animals., Conclusions: Results from this study suggest that systemic iron levels may play a role in knee OA pathogenesis, with a short-term deficit in dietary iron reducing the severity of knee cartilage lesions., (Copyright © 2022 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.)

Older age is the primary risk factor for most chronic diseases, including Alzheimer's disease (AD). Current preclinical models to study brain aging and AD are mainly transgenic and harbor mutations intended to mirror brain pathologies associated with human brain aging/AD (eg, by increasing production of the amyloid precursor protein, amyloid beta [Aβ], and/or phosphorylated tau, all of which are key pathological mediators of AD). Although these models may provide insight on pathophysiological processes in AD, none completely recapitulate the disease and its strong age-dependence, and there has been limited success in translating preclinical results and treatments to humans. Here, we describe 2 nontransgenic guinea pig (GP) models, a standard PigmEnTed (PET) strain, and lesser-studied Dunkin-Hartley (DH) strain, that may naturally mimic key features of brain aging and AD in humans. We show that brain aging in PET GP is transcriptomically similar to human brain aging, whereas older DH brains are transcriptomically more similar to human AD. Both strains/models also exhibit increased neurofilament light chain (NFL, a marker of neuronal damage) with aging, and DH animals display greater S100 calcium-binding protein B (S100β), ionized calcium-binding adapter molecule 1 (Iba1), and Aβ and phosphorylated tau-which are all important markers of neuroinflammation-associated AD. Collectively, our results suggest that both the PET and DH GP may be useful, nontransgenic models to study brain aging and AD, respectively., (© The Author(s) 2022. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Iron has been emerging as a key contributor to aging-associated, chronic disorders due to the propensity for generating reactive oxygen species. To date, there are a limited number of publications exploring the role of iron in the pathogenesis of primary/age-related osteoarthritis (OA). The objective of this study was to determine whether reduced iron via pharmacologic iron chelation with deferoxamine (DFO) affected the development and/or severity of cartilage lesions in a primary OA model. At 12-weeks-of-age, 15 male Dunkin-Hartley guinea pigs received either 46 mg/kg DFO (n = 8) or vehicle control (n = 7) injected subcutaneously twice daily for five days each week. Movement changes, captured via overhead enclosure monitoring, were also determined. Termination occurred at 30-weeks-of-age. Iron was quantified in serum, urine, liver, and femoral head articular cartilage. Left knees were evaluated for: structural changes using histopathology guidelines; and immunohistochemistry. Gene expression analysis was conducted on right knee articular cartilage. DFO reduced iron levels in femoral head articular cartilage (p = 0.0006) and liver (p = 0.02), and increased iron within urine (p = 0.04) and serum (p = 0.0009). Mobility of control animals declined, while the DFO group maintained activity levels similar to the first month of treatment (p = 0.05). OA-associated cartilage lesions were reduced in knees of DFO animals (p = 0.0001), with chondrocyte hypocellularity a key histologic difference between groups (p < 0.0001). DFO-receiving animals had increased immunostaining for phosphorylated adenosine monophosphate activated protein kinase alpha within knee articular cartilage; lower transcript counts of several proapoptotic genes (p = 0.04-0.0004) and matrix-degrading enzymes (p = 0.02-<0.0001), and increased expression of the anti-apoptotic gene Bcl-2 (p < 0.0001) and a tissue inhibitor of matrix-metalloproteinases (p = 0.03) were also observed. These results suggest that iron chelation delayed the progression of primary OA in an animal model and could hold potential as a translational intervention. These findings provide expanded insight into factors that may contribute to the pathogenesis of primary OA., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Objective: Faced with the frustration of chronic discomfort and restricted mobility due to osteoarthritis (OA), many individuals have turned to acupuncture for relief. However, the efficacy of acupuncture for OA is uncertain, as much of the evidence is inconclusive. The purpose of this study was to evaluate electroacupuncture (EA) in a rodent model of OA such that conclusions regarding its effectiveness for symptom or disease modification could be drawn., Methods: Ten 12-month-old male Hartley guinea pigs-which characteristically have moderate to advanced OA at this age-were randomly assigned to receive EA for knee OA (n = 5) or anesthesia only (control group, n = 5). Treatments were performed three times weekly for 3 weeks, followed by euthanasia 2 weeks later. Gait analysis and enclosure monitoring were performed weekly to evaluate changes in movement. Serum was collected for inflammatory biomarker testing. Knee joints were collected for histology and gene expression., Results: Animals receiving EA had significantly greater changes in movement parameters compared to those receiving anesthesia only. There was a tendency toward decreased serum protein concentrations of complement component 3 (C3) in the EA group compared to the control group. Structural and antioxidant gene transcripts in articular cartilage were increased by EA. There was no significant difference in total joint histology scores between groups., Conclusion: This study provides evidence that EA has a positive effect on symptom, but not disease, modification in a rodent model of OA. Further investigations into mechanistic pathways that may explain the efficacy of EA in this animal model are needed.

Cannabidiol (CBD) has gained widespread popularity as a treatment for osteoarthritis (OA) in pets; however, there is minimal scientific evidence regarding safe and effective dosing. This study determined plasma and tissue pharmacokinetics after oral CBD oil suspension administration in Hartley guinea pigs (Cavia porcellus), which spontaneously develop OA at 3 months of age. Ten, 5-month-old, male guinea pigs were randomly assigned to receive 25 (n = 5) or 50 mg/kg (n = 5) CBD oil once orally. Blood samples were collected at 0, 0.25, 0.5, 1, 2, 4, 8, 12, and 24 h timepoints. Open-field enclosure monitoring revealed no adverse effects. After euthanasia, stifle cartilage and infrapatellar fat pads were collected to quantitate CBD. CBD concentrations were determined using a validated liquid chromatography-mass spectrometry method, and pharmacokinetic parameters were calculated using noncompartmental analysis. The area under the plasma concentration-versus-time curve was 379.5 and 873.7 h*ng/mL, maximum plasma concentration was 42 and 96.8 ng/mL, time to maximum plasma concentration was 1.6 and 4.8 h, and terminal phase half-life was 8.1 and 10.8 h for the 25 and 50 mg/kg doses, respectively. CBD was detected in joint tissues of all animals. Further studies, including work in female guinea pigs, are needed to determine the efficacy of CBD for OA., (© 2021 John Wiley & Sons Ltd.)

Background: The objective of this study was to determine if mechanistic target of rapamycin (mTOR) inhibition with or without AMP-activated protein kinase (AMPK) activation can protect against primary, age-related OA., Design: Dunkin-Hartley guinea pigs develop mild primary OA pathology by 5 months of age that progresses to moderate OA by 8 months of age. At 5 months, guinea pigs served as young control (n = 3) or were fed either a control diet (n = 8), a diet enriched with the mTOR-inhibitor rapamycin (Rap, 14 ppm, n = 8), or Rap with the AMPK-activator metformin (Rap+Met, 1000 ppm, n = 8) for 12 weeks. Knee joints were evaluated by OARSI scoring, micro-computed tomography, and immunohistochemistry. Glenohumeral articular cartilage was collected for western blotting., Results: Rap- and Rap+Met-treated guinea pigs displayed lower body weight than control. Rap and Rap+Met inhibited articular cartilage mTORC1 but not mTORC2 signaling. Rap+Met, but not Rap alone, stimulated AMPK. Despite lower body weight and articular cartilage mTORC1 inhibition, Rap- and Rap+Met-treated guinea pigs had greater OA severity in the medial tibial plateau due to articular cartilage structural damage and/or proteoglycan loss. Rap and Rap+Met increased plasma glucose compared to control. Plasma glucose concentration was positively correlated with proteoglycan loss, suggesting hyperglycemic stress after Rap treatment was related to worsened OA., Conclusions: This is the first study to show that Rap induced increase in plasma glucose was associated with greater OA severity. Further, articular cartilage mTORC1 inhibition and bodyweight reduction by dietary Rap and Rap+Met did not appear to protect against primary OA during the prevailing hyperglycemia., (© 2021. The Author(s).)

Background: Animal models of muscle injury have primarily relied on methods which do not mimic the chronic scarring that typically occurs adjacent to the myotendinous junction (MTJ). The goal of this study was three-fold: (i) to create a strain-induced in vivo model of rectus femoris MTJ injury in rats; (ii) to document clinical manifestations of injury using longitudinal tracking of individual animals via voluntary and compulsory (treadmill) mobility analyses and (iii) to validate and assess the model for persistent scarring through serial histologic assessment and development of a semi-quantitative grading scheme to characterize injury response over time., Methods: Strain-induced MTJ injury was generated in male Sprague Dawley rats via needle tension directed along the transverse axis between the rectus femoris muscle and distal tendon that attaches to the patella. Animals received mobility assessments (gait analysis using a DigiGait Treadmill System and weight bearing using a Tekscan Rodent Walkway System) at days 0, 1, 3, 6, 13, 20, and 27 of the experimental protocol. Rats were euthanized at 1, 3, 7, 14, and 28 days post-injury (n = 6 rats per time-point) and hindlimbs were processed for histology., Results: Significant changes in locomotor parameters included injured and contralateral limb paw area, max dA/dt (limb deceleration/breaking time), stride time, stance time, force time impulse, and fore/hind symmetry, and injured limb maximum force. The most significant and consistent histologic finding was a pathologic fibrotic adhesive lesion at the muscle and tendon interface along the proximal aspect of the patella just distal to the injury site. This lesion was composed of reactive fibroblasts, disorganized collagen fibers, vascular profiles, and a myxomatous ground substance stroma., Conclusions: This work is the first to characterize the clinical and pathologic development of a chronic model of rectus femoris MTJ injury, which resulted in altered mobility likely caused by a strain-induced fibrotic scar along the anterior patella. Notably, both the functional and pathologic changes recapitulated the course of injury progression similar to what is described in humans. This work provides a unique model to study MTJ injury mechanisms for the identification of enhanced treatment options for patients who suffer from activity-related muscle conditions., Competing Interests: CONFLICT OF INTERESTS The authors declare that they have no conflict of interests.

The Dunkin Hartley is the most common guinea pig strain used in biomedical research, particularly for studies of asthma, allergy, infectious disease, reproduction, and osteoarthritis. Minimally invasive blood tests, such as complete blood counts and serum biochemistry profiles, are often collected for diagnostics and laboratory analyses. However, reference intervals for these assays have not yet been well-documented in this strain. The purpose of this study was to establish reference intervals for hematologic and biochemical parameters of Dunkin Hartley guinea pigs and determine age- and sex-related differences. Hematologic and biochemical parameters were retrospectively obtained from 145 male and 68 female guinea pigs between 2 and 15 months of age. All blood parameters were analyzed by a veterinary clinical pathology laboratory. Reference intervals were established according to the American Society for Veterinary Clinical Pathology guidelines. Age- and sex-related differences were determined using unpaired t-tests or nonparametric Mann-Whitney tests. Hematocrit, red blood cell distribution width, mean platelet volume, white blood cell count, heterophils, monocytes, eosinophils, glucose, blood urea nitrogen, creatinine, calcium, magnesium, total protein, albumin, globulin, cholesterol, aspartate aminotransferase, gamma glutamyl transferase, and bicarbonate increased with age. Mean corpuscular hemoglobin concentration, cellular hemoglobin concentration mean, platelets, lymphocytes, phosphorus, albumin/globulin ratio, alkaline phosphatase, anion gap, and calculated osmolality decreased with age. Males had higher hemoglobin, hematocrit, red blood cell count, mean corpuscular hemoglobin concentration, white blood cell count, heterophils, Foa-Kurloff cells, alanine aminotransferase, and bicarbonate and lower mean corpuscular volume, red blood cell distribution width, platelets, mean platelet volume, eosinophils, total protein, albumin, globulin, cholesterol, potassium, anion gap, calculated osmolality, and iron compared to females. Establishing age and sex differences in hematologic and biochemical parameters of Dunkin Hartley guinea pigs provides valuable insight into their physiology to better evaluate diagnostics and experimental results., Competing Interests: The authors have declared that no competing interests exist.

Background: Feline Infectious Peritonitis (FIP) is a fatal disease of cats that can be very difficult to definitively diagnose antemortem. Multiplex fluorescent immunocytochemical (MF-ICC) assays are emerging as useful diagnostic tests in veterinary medicine, particularly for fluid samples., Objective: We aimed to develop and optimize an MF-ICC assay to detect feline coronavirus within macrophages, with the primary goal of determining the allowable/recommended sample storage conditions for clinical use of this assay., Methods: A feline macrophage cell line was infected with the FIP virus. Following harvest into EDTA tubes (simulating typical clinical collection of effusion), cells were stored at 4℃, 22℃, and 37℃. For each temperature condition, slides for MF-ICC were made at 0, 1, 2, 3, and 5 days post-collection. To assess the stability of immunoreactivity following fixation, freshly harvested infected cells were fixed onto slides and maintained at 4℃ for 1, 2, 4, and 12 weeks. All slides were analyzed by MF-ICC for the presence of mononuclear cells with co-expression of vimentin and coronaviral antigen., Results: MF-ICC confirmed that cells tested positive for coronavirus at 4℃ through 3 days post-harvest, 22℃ through 48 hours post-harvest, and 37℃ through 24 hours post-harvest. The MF-ICC assay was successfully performed on fixed slides through the 12-week time point. This assay also demonstrated positive results on a clinical sample of abdominal fluid from a cat later confirmed to have FIP., Conclusions: The MF-ICC assay described here offers a potentially specific and relatively stable antemortem diagnostic test for feline infectious peritonitis. Evaluation of this assay in clinical samples is ongoing., (© 2021 American Society for Veterinary Clinical Pathology.)

Skeletal muscle dysfunction, articular cartilage degeneration, and bone loss occur essentially in parallel during aging. Mechanisms contributing to this systemic musculoskeletal decline remain incompletely understood, limiting progress toward developing effective therapeutics. Because the progression of human musculoskeletal aging is slow, researchers rely on rodent models to identify mechanisms and test interventions. The Dunkin Hartley guinea pig is an outbred strain that begins developing primary osteoarthritis by 4 months of age with a progression and pathology similar to aging humans. The purpose of this study was to determine if skeletal muscle remodeling during the progression of osteoarthritis in these guinea pigs resembles musculoskeletal aging in humans. We compared Dunkin Hartley guinea pigs to Strain 13 guinea pigs, which develop osteoarthritis much later in the lifespan. We measured myofiber type and size, muscle density, and long-term fractional protein synthesis rates of the gastrocnemius and soleus muscles in 5, 9, and 15-month-old guinea pigs. There was an age-related decline in skeletal muscle density, a greater proportion of smaller myofibers, and a decline in type II concomitant with a rise in type I myofibers in the gastrocnemius muscles from Dunkin Hartley guinea pigs only. These changes were accompanied by age-related declines in myofibrillar and mitochondrial protein synthesis in the gastrocnemius and soleus. Collectively, these findings suggest Dunkin Hartley guinea pigs experience myofiber remodeling alongside the progression of osteoarthritis, consistent with human musculoskeletal aging. Thus, Dunkin Hartley guinea pigs may be a model to advance discovery and therapeutic development for human musculoskeletal aging., (Copyright © 2020 Musci, Walsh, Konopka, Wolff, Peelor, Reiser, Santangelo and Hamilton.)

Objective: Iron is emerging as a key player in aging-associated diseases due to its propensity for driving free radical formation. Studies examining the role of iron in the pathogenesis of primary osteoarthritis (OA) are limited. Our objective was to establish a direct relationship between excess iron and OA by administering iron dextran to a guinea pig strain with decreased propensity for developing this disease., Design: Twenty, 12-week-old Strain 13 guinea pigs received either iron dextran or dextran control intraperitoneally once weekly for 4 weeks; termination occurred at 16 weeks of age. Iron levels were determined systemically (serum and liver) and within diarthrodial joints [femoral head articular cartilage and infrapatellar fat pads (IFPs) of knee joints]. One knee was collected to score structural changes associated with OA via microcomputed tomography (microCT) and histology using published grading schemes. Articular cartilage and IFPs were harvested from contralateral knees for gene expression analyses., Results: Iron overload was confirmed systemically via increased serum iron and liver iron concentration. Articular cartilage and IFPs in the iron dextran group also had higher levels of iron. Excess iron worsened knee OA using both microCT and histologic scoring systems. Gene analyses revealed that exogenous iron altered the expression of iron trafficking proteins, select cytokines, and structural components of cartilage., Conclusion: These results demonstrate that systemic iron overload caused cellular iron accumulation in the knee joint. This excess iron is associated with increased expression of local inflammatory mediators and early onset and progression of knee joint OA in Strain 13 animals., (Copyright © 2020 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.)

Whole transferrin receptor (TfR) is present in reticulocyte exosomes. Soluble transferrin receptor (sTfR) is cleaved from whole TfR in human plasma, with the remnant cytoplasmic domain (cTfR) remaining membrane associated. In humans, sTfR is a biomarker that can detect iron deficiency in the presence of inflammatory disease. This condition is still a diagnostic dilemma in veterinary species. We aimed to (1) confirm the presence of exosomes and exosome-associated TfR in the serum of dogs, cats, and horses; and (2) to assess and compare the proportion of cTfR to total (cTfR + whole) in exosomal membranes of healthy and diseased dogs and cats and in healthy horses to indirectly predict their anticipated levels of circulating sTfR. We used discarded serum and whole blood samples from canine and feline patients, separated into healthy and diseased groups based on the health status of each patient, and healthy equine participants from a previous study. Ultracentrifugation, followed in some experiments by OptiPrep discontinuous density gradient fractionation, was used to isolate exosomes. Exosomes and associated TfR were identified using TEM and Western blot for TfR, respectively. Densitometry tracings of Western blots of serum exosomes were used to measure the proportion of cTfR to total TfR. Extracellular vesicles compatible with exosomes were successfully isolated and expressed TfR. The proportion of cTfR in dogs was greater than 50%, indicating that a majority of the whole TfR was cleaved to produce sTfR (and remnant cTfR). There was significant interindividual variation and no significant difference between healthy and diseased animals. The proportion of cTfR in cats was very low at 11%, indicating that very little sTfR was likely produced. There was a small yet significant difference between healthy and diseased cats. Healthy horses do not appear to cleave exosome-associated TfR. Diagnosis of iron deficiency in the presence of inflammatory disease remains a challenge in veterinary medicine. Our results indicate that TfR is poorly or unpredictably cleaved in veterinary species, revealing that there are species differences in exosomal TfR handling. These data suggest that development of an assay for the detection and quantification of sTfR in the species investigated may not be warranted., (Copyright © 2020 ISEH -- Society for Hematology and Stem Cells. Published by Elsevier Inc. All rights reserved.)

Background: Biochemistry analyzers in many high-throughput laboratories use indirect potentiometry to determine serum electrolyte concentrations, which involves a pre-analytical dilution step that may be associated with artifactual increases or decreases in electrolyte concentrations under circumstances of altered serum water fraction (SWF). Severe hypo- and hyperproteinemia, conditions that cause altered SWF, are recognized but under-emphasized causes of falsely measured serum sodium concentrations., Objectives: The goals of this study were to determine the average actual SWF (SWF A ) and establish formulae to correct serum sodium concentration measured by indirect potentiometry in hypo- and hyperproteinemic cats., Methods: Serum samples from 112 feline patients were analyzed for electrolytes (measured by both indirect and direct potentiometry), total protein, albumin, triglycerides, and cholesterol. Each serum sample was also lyophilized to determine the SWF A . A feline-specific formula to estimate SWF (SWF E-FEL ) was developed and evaluated with a multivariable linear model., Results: The mean SWF A in this population of cats was 91.2%, which was significantly different (P < .0001) than the mean (93.9%) calculated using the human estimated formula (SWF E-HUM ). The formula devised for the SWF E-FEL better recapitulated the SWF A than did the SWF E-HUM , and the corrected sodium concentrations calculated using the feline formula were better correlated with serum sodium measured by direct potentiometry than those determined using the human formula., Conclusions: Application of feline-specific formulae is expected to limit the misinterpretation of electrolyte data from indirect potentiometry when altered SWF occurs. To demonstrate this, a case example of a hypoproteinemic cat is provided., (© 2020 American Society for Veterinary Clinical Pathology.)

Blood collection methods in guinea pigs are limited due to the animals' compact neck, short limbs, and lack of a tail. Gingival venipuncture is a recently described blood sampling technique that is minimally traumatic with no significant alterations in hematologic parameters when multiple blood samples were collected weekly for 6 wk. The purpose of this study was to determine whether the gingival vein can be used as an alternative blood collection site in guinea pigs, such that: (1) hematologic parameters would be consistent with samples collected from the cranial vena cava; and (2) no contaminants from the oral cavity would be introduced into the sample. Blood samples were obtained from both the gingival vein and cranial vena cava of anesthetized Dunkin Hartley guinea pigs for CBC ( n = 9) and aerobic blood cultures ( n = 10). Only MCV was significantly different between sampling sites. Bland-Altman analyses calculated a small mean bias for all hematologic parameters, indicating clinical interpretation is unlikely to be affected by the sampling site. Bacterial growth occurred in all 5 gingival vein blood samples prepared by using saline and 2 of the 5 prepared with dilute chlorhexidine. Bacteria did not grow from any cranial vena caval blood samples prepared with dilute chlorhexidine. No clinical signs of hemorrhage or trauma were detected at either site. These results provide evidence that gingival venipuncture can be used as an alternative blood collection method for guinea pigs for hematologic analysis but should not be used for blood culture.

Background: Obesity is a leading risk factor for osteoarthritis (OA). In contrast, calorie restriction (CR) may lessen OA due to improved systemic inflammatory status and reduced weight-bearing. The aim of this study was to determine how CR with regular chow versus a high-fat diet (HFD) alters OA progression using the Hartley guinea pig model of disease., Methods: Twenty-four male guinea pigs were allocated to four groups at 2 months of age: (1) ad libitum regular chow (obese), (2) CR regular chow (lean), (3) ad libitum HFD, and (4) CR HFD. Animals in both HFD groups ate identical amounts and were combined into one HFD group for analyses. At 5 months, hind limbs were harvested for microcomputed tomography (microCT) and histopathologic evaluation of knee OA. Total body, gonad fat, and infrapatellar fat pad (IFP) masses were recorded. IFPs were collected for gene expression analysis. Immunohistochemistry for monocyte chemoattractant protein-1 (MCP-1) was performed on intact joints. Serum was utilized for protein C3 measurement. All data were compared using ordinary one-way ANOVA analyses with Tukey's post-hoc tests., Results: Body mass in the lean and HFD groups were similar and lower than the obese group. Despite this, gonad fat pads in the HFD group were comparable to the obese group. MicroCT and histologic OA scores were similar in obese and HFD groups; both scores were significantly lower in the lean group. Obese and HFD groups displayed increased gene expression of pro-inflammatory and catabolic mediators in IFPs relative to lean animals. Consistent with this, immunohistochemistry for MCP-1 in knee joints demonstrated strong positive staining in obese and HFD groups but was minimally detected in lean animals. Serum protein C3 levels were also statistically higher., Conclusions: This study demonstrated that CR with a regular chow diet lessened knee OA in the Hartley guinea pig and was associated with decreased local and systemic inflammation compared to obese animals. HFD animals, although under CR conditions, had OA scores and inflammatory markers similar to obese animals. Thus, diet composition, and not solely body weight, may be a key factor in development of OA.

Objectives:  The aim of this study was to evaluate the safety and collect pilot data measuring clinical effects of intravenously administered, adipose-derived, culture-expanded, allogeneic mesenchymal stem cells in dogs with elbow osteoarthritis., Materials and Methods:  Dogs ( n  = 13) with naturally occurring elbow osteoarthritis received three intravenous doses of allogeneic canine mesenchymal stem cells via an open-label clinical trial. Primary outcome measures collected over a 6-month study period included objective gait analysis, accelerometry, owner questionnaires and joint fluid analysis., Results:  No acute adverse events were observed following repeated intravenous treatment with allogeneic mesenchymal stem cells. A significant improvement in mean client-specific outcome measure (CSOM) activity score and CSOM behaviour score was observed when pre-treatment values were compared with post-treatment values (day >28). In contrast, mean peak vertical force significantly decreased from baseline to post-treatment (>day 28). Weekly activity counts did not show a significant difference between baseline to post-treatment time points. Synovial fluid biomarkers did not change during treatment, and labelled mesenchymal stem cells were rarely detected in synovial fluid samples collected after mesenchymal stem cell administration., Clinical Significance:  For dogs with naturally occurring elbow osteoarthritis, intravenous administration of mesenchymal stem cells was clinically well tolerated. While some subjective outcome measures showed significant improvements, objective outcome measures did not confirm similar changes. Further research is needed before intravenous mesenchymal stem cells can be recommended as a treatment for elbow osteoarthritis in dogs., Competing Interests: Dr. Olsen reports grants from the Shipley Foundation and Eldred Foundation during the conduct of the study. Dr. Webb reports grants from the Shipley Foundation during the conduct of the study; personal fees and non-financial support from ReCellerate, Inc., outside the submitted work. Dr. Dow reports grants from Shipley Foundation, during the conduct of the study. Dr. Duerr reports grants from the Shipley Foundation and the Eldred Foundation during the conduct of the study. Dr. Johnson reports grants from Shipley Foundation, grants from Eldred Foundation, during the conduct of the study. Dr. Santangelo has nothing to disclose., (Georg Thieme Verlag KG Stuttgart · New York.)

Aim: There is potential discrepancy between human and laboratory animal studies of osteoarthritis (OA), as radiographic assessment is the hallmark of the former and histopathology the standard for the latter. This suggests a need to evaluate OA in animal models in a manner similar to that utilized in people. Our study aimed to develop a whole joint grading scheme for microcomputed tomography (microCT) images in Hartley guinea pigs, a strain that recapitulates joint changes highlighted in human spontaneous OA., Materials and Methods: Knees from animals aged 2, 3, 5, 9, and 15 months were evaluated via whole joint microCT and standard histologic scoring. Quantitative microCT parameters, such as bone volume/total volume were also collected., Results: Both whole joint microCT and histologic scores increased with advancing age and showed strong correlation (r = 0.89. p < 0.0001). Histologic scores, which focus on cartilage changes, increased progressively with age. Whole joint microCT scores, which characterize bony changes, followed a stepwise pattern: scores increased between 3 and 5 months of age, stayed consistent between 5 and 9 months, and worsened again between 9 and 15 months., Conclusions: This work provides data that advocates the use of a whole joint microCT scoring system in guinea pig studies of OA, as it provides important information regarding bony changes that occur at a different rate than articular cartilage changes. This grading scheme, in conjunction with histology and quantitative microCT measurements, may enhance the translational value of this animal model as it pertains to human work.

Background: Obesity is a global disease, affecting nearly half a billion people. Unfortunately, this trend is mirrored in our canine population., Objectives: As obesity is a complex inflammatory disease, there is a need to determine whether routine medical screening tests may indicate, or be influenced by, its presence. The objective of the current study was to determine if significant differences exist between CBC and biochemical profile values from control vs overweight/obese, client-owned dogs considered clinically healthy., Methods: Dogs presented for routine health examinations, including minor dental or elective surgical procedures, were retrospectively identified from a hospital population. Animals were allocated to 2 categories based on body condition score (BCS), and data were analyzed by Mann-Whitney nonparametric analysis with statistical significance at a P ≤ .05., Results: After exclusions, 116 dogs were assigned to the overweight/obese group (BCS ≥ 7) and 240 dogs to the control group (BCS = 4-6). Overweight/obese dogs had higher total leukocyte counts and higher plasma protein and globulin concentrations. Other differences were attributed to decreased serum water fraction (increased sodium, albumin, calcium, and anion gap) in the overweight/obese group. Interestingly, chloride concentration was decreased (in the face of increased sodium) in the obese group., Conclusions: There is CBC and biochemical evidence to support the concern that obesity influences laboratory values, even in dogs considered clinically healthy. Prospective studies aimed at characterizing these changes are needed to provide insight into the connection between obesity and its comorbidities., (© 2017 American Society for Veterinary Clinical Pathology.)

Background: Meniscal root tears cause menisci and their insertions to inadequately distribute loads and potentially leave underlying articular cartilage unprotected. Untreated meniscal root tears are becoming increasingly recognized to induce joint degradation; however, little information is known about anterior meniscal root tears and how they affect joint tissue., Purpose: To observe the early degenerative changes within the synovial fluid, menisci, tibial articular cartilage, and subchondral bone after arthroscopic creation of untreated anterior meniscal root tears., Study Design: Controlled laboratory study., Methods: Anterolateral meniscal root tears were created in 1 knee joint of 5 adult Flemish Giant rabbits, and anteromedial meniscal root tears were created in 4 additional rabbits. The contralateral limbs were used as nonoperated controls. The animals were euthanized at 8 weeks postoperatively; synovial fluid was aspirated, and tissue samples of menisci and tibial articular cartilage were collected and processed for multiple analyses to detect signs of early degeneration., Results: Significant changes were found within the synovial fluid, meniscal tissue, and tibial subchondral bone of the knees with anterior meniscal root tears when compared with controls. There were no significant changes identified in the tibial articular cartilage when comparing the tear groups with controls., Conclusion: This study demonstrated early degenerative changes within the synovial fluid, menisci, and tibial subchondral bone when leaving anterior meniscal root tears untreated for 8 weeks. The results suggest that meniscal tissue presents measurable, degenerative changes prior to changes within the articular cartilage after anterior meniscal root tears. Anterior destabilization of the meniscus arthroscopically may lead to measurable degenerative changes and be useful for future in vivo natural history and animal repair studies., Clinical Relevance: The present study is the first to investigate various tissue changes after anterior meniscal root tears of both the medial and lateral menisci. The results from this study suggest that degenerative changes occur within the synovial fluid, meniscus, and tibial subchondral bone prior to any measurable changes to the tibial articular cartilage. Further studies should expand on this study to evaluate how these components continue to progress when left untreated for long periods., Competing Interests: One or more of the authors has declared the following potential conflict of interest or source of funding: R.F.L. receives royalties from Arthrex, Ossur, and Smith & Nephew; is a paid consultant for Arthrex, Ossur, and Smith & Nephew; and receives research support from Arthrex, Smith & Nephew, Ossur, and Linvatec. Funding for this project was provided by the Steadman Philippon Research Institute in Vail, Colorado.

Background: Effects of aging on hematologic and biochemical variables are well described in people. Anemia of the elderly is attributed to iron deficiency, anemia of chronic disease, chronic kidney disease, myelodysplasia, or idiopathic causes. Limited studies have examined these variables in aging dogs, but they have typically examined single breeds in research settings., Objective: The objective of this study was to identify differences in CBC and biochemistry values between adult and aged dogs of many breeds., Methods: Dogs presenting for wellness examinations and minor dental/elective surgeries that were otherwise clinically healthy were retrospectively identified. Dogs were categorized by age: adult (1-7.9 years), senior (8-11.9 years), and geriatric (12+ years). Standard CBC and biochemistry data were collated. Asian breeds, Greyhounds, and dogs with data indicating overt underlying disease were excluded. The Kruskal-Wallis test was used to compare groups with statistical significance set at P ≤ .05., Results: Hematocrit, MCV, and serum iron decreased with age, indicating possible iron-restricted erythropoiesis (IRE), due to iron deficiency or low-grade chronic inflammation. Total proteins, globulins, and platelet counts increased with age while albumin decreased, suggesting low-grade inflammation. Urea was increased in older dogs without a concurrent increase in creatinine, which points toward gastrointestinal bleeding or dehydration., Conclusion: Clinically healthy, aging dogs have changes in laboratory variables that indicate altered physiologies compared to younger adult animals, including evidence of IRE, inflammation, and potential gastrointestinal bleeding, suggesting a similar trend to that of elderly human beings. Future studies will examine markers of iron metabolism and inflammation in aging dogs., (© 2017 American Society for Veterinary Clinical Pathology.)

Synovial fluid analysis is a key component of the minimum database needed to diagnose and manage primary and secondary articular joint disorders. Unfortunately, preanalytical variables can drastically alter samples submitted for evaluation to veterinary laboratories and it is considered the stage at which most laboratory error occurs. This article addresses common sources of preanalytical variability and error that are seen in veterinary medicine. With consistent quality control and reporting of specimens, downstream clinical decision making and management of patients can be accelerated and improved., (Copyright © 2016 Elsevier Inc. All rights reserved.)

A 6-year-old, male castrated, mixed-breed dog was referred to the James L. Voss Veterinary Teaching Hospital at Colorado State University for bicavitary effusion. On examination, the dog was tachycardic and tachypneic with bilaterally decreased lung sounds. Thoracic and abdominal ultrasonic examination revealed pleural and peritoneal effusions, which were aspirated and submitted for fluid analysis and cytology. Both cavity fluids were classified as exudates with a large population of vacuolated mononuclear cells. Multiplex immunocytochemistry (ICC) for cytokeratin and vimentin demonstrated exclusively cytokeratin expression, indicating these cells were of epithelial origin. A full diagnostic evaluation was performed, including CBC, clinical chemistry, a pet-side test for heartworm disease, ehrlichiosis, Lyme disease, and anaplasmosis, imaging modalities of thorax, abdomen, and heart, urinalysis, and fine-needle aspirations of spleen, liver, and popliteal lymph nodes. The dog was diagnosed with pleural and peritoneal carcinoma with presumed carcinomatosis. A single dose of intracavitary carboplatin was administered before discharge, and over a period of 2 weeks, 5 thoracocenteses were performed. A subcutaneous mass was noted at a thoracocentesis site one week after initial presentation. Cytology of the mass was consistent with carcinoma, and neoplastic seeding of the tumor cells from the thoracocentesis was suspected. The dog was euthanized 15 days after the first visit, and a necropsy was performed. Findings were consistent with carcinomatosis secondary to anaplastic pulmonary carcinoma with transient subcutaneous seeding of neoplastic cells during routine thoracocentesis. This case demonstrates the utility of multiplex ICC in the clinical setting., (© 2016 American Society for Veterinary Clinical Pathology.)

Osteoarthritis (OA) is a debilitating condition characterized by inflammation, breakdown, and consequent loss of cartilage of the joints. Epidemiological studies indicate obesity is an important risk factor involved in OA initiation and progression. Traditional views propose OA to be a biomechanical consequence of excess weight on weight-bearing joints; however, emerging data demonstrates that systemic and local factors released from white adipose depots play a role. Hence, current views characterize OA as a condition exacerbated by a metabolic link related to adipose tissue, and not solely related to redistributed/altered weight load. Factors demonstrated to influence cartilage and bone homeostasis include adipocyte-derived hormones ("adipokines") and adipose depot released cytokines. Epidemiological studies demonstrate a positive relation between systemic circulating cytokines, leptin, and resistin with OA types, while the association with adiponectin is controversial. Local factors in joints have also been shown to play a role in OA. In particular, this includes the knee, a weight-bearing joint that encloses a relatively large adipose depot, the infrapatellar fat pad (IFP), which serves as a source of local inflammatory factors. This review summarizes the relation of obesity and OA as it specifically relates to the IFP and other integral supporting structures. Overall, studies support the concept that metabolic effects associated with systemic obesity also extend to the IFP, which promotes inflammation, pain, and cartilage destruction within the local knee joint environment, thus contributing to development and progression of OA.

Background: True and functional iron deficiency can result in anemia. Current tests to assess iron status often do not allow differentiation between these entities, which can affect optimal treatment. Previous work suggested low reticulocyte hemoglobin content (CHr) may be an early indicator of iron deficiency., Objective: This study aimed to correlate several inflammation markers with CHr values in dogs. We hypothesize that dogs with low CHr values have hematologic and biochemical evidence of inflammation., Methods: Animals with CHr values below the reference interval were included in the low CHr group, while dogs with normal or increased CHr were included in the control group. HCT, MCV, CHr, reticulocyte mean cell volume (MCVr), concentrations of serum iron, C-reactive protein (CRP), ferritin, and ceruloplasmin, and total iron-binding capacity (TIBC), percent transferrin saturation (% sat), and total WBC, neutrophil, and monocyte counts were determined. Nonparametric tests were performed; median values and percentage of abnormalities between each group were compared., Results: Relative to control dogs, animals in the low CHr group had higher median values for CRP, ferritin, ceruloplasmin, and WBC concentration (P ≤ .05), and lower median values for HCT and MCV (P ≤ .0001). Higher frequencies of abnormalities for CRP, ferritin, WBC, neutrophil, and monocyte concentrations (P ≤ .02) were present in the low CHr group., Conclusions: Dogs with low CHr values often have evidence of inflammation, but low CHr did not reliably predict Fe deficiency. Additional diagnostic tests are needed to differentiate true and functional iron deficiency., (© 2015 American Society for Veterinary Clinical Pathology.)

An 11-year-old male castrated mixed-breed dog was presented for exercise intolerance, tetraparesis, and persistent hypoglycemia. Abdominal ultrasound examination revealed 2 nodules within the right limb of the pancreas. Cytology from one nodule was consistent with a carcinoma of neuroendocrine origin, with a primary differential diagnosis of insulinoma. Histologic evaluation and immunohistochemistry for synaptophysin and insulin confirmed the diagnosis of insulinoma. Additionally, there was a solitary nodule of mineralized compact bone composing approximately 60% of the mass. To the authors' knowledge, this is the first report of osseous metaplasia within an insulinoma (islet cell carcinoma)., (© 2014 American Society for Veterinary Clinical Pathology and European Society for Veterinary Clinical Pathology.)

A computer-aided gait analysis system was used to contrast two guinea pig strains with differing propensity for osteoarthritis (OA), with/without administration of a nonsteroidal anti-inflammatory drug. Walking speed and static/dynamic gait parameters were determined at baseline. Flunixin meglumine was given and animals were evaluated 4, 24, and 72 hours after treatment. Body weight was compared using unpaired t-tests. Knee joints were histologically evaluated using species-specific criteria; indices were analyzed using one-way ANOVA, Kruskal-Wallis test, followed by Dunn's multiple comparisons. A generalized linear model followed by Tukey's posttests juxtaposed gait parameters; walking speed was a covariate for other outcome measures. Body weight was not different between strains; OA-prone animals demonstrated more progressive chondropathy. At baseline, OA-prone animals had slower walking speeds, narrower hind limb bases of support, shorter stride lengths, and slower limb swing speeds relative to OA-resistant animals. These differences were not detected 4 or 24 hours after treatment. By 72 hours, OA-prone animals had returned to baseline values. These findings indicate a distinct voluntary gait pattern in a rodent model of bilateral primary OA, modification of which may allow rapid screening of novel therapies. Flunixin meglumine temporarily permitted OA-prone animals to move in a manner that was analogous to OA-resistant animals.

Background: Current cartilage transplantation techniques achieve suboptimal restoration and rely on patient donor cells or living grafts of chondrocytes., Purpose: We sought to enhance allogeneic grafts by testing mosaics of genetically engineered and naïve juvenile human chondrocytes (jCh)., Methods: We obtained specimens from three humans and performed three experiments (two in vitro, one in vivo). We compared neocartilage with and without (1) supplemented serum-free medium (chondrocyte differentiation medium [CDM]), (2) adenoviral BMP-2 (AdBMP-2) transduction, and (3) varying ratios (0.1-1) of transduced and naïve jCh. We compared (4) healing with mosaic grafts with naïve neocartilage or marrow stimulation in immunosuppressed rats. For each of 10 in vitro treatment groups, we had six replicates for each human, and for each of three in vivo treatment groups, we had four replicates for one human. We scored the histology with the semiquantitative Bern score., Results: AdBMP-2 and naïve neocartilage growth in CDM were histologically superior (Bern score, 5.2 versus 3.7; 8.0 versus 1.8) and size (8.0 versus 6.1; 7.9 versus 2.2 mg) to standard medium. In CDM, AdBMP-2 decreased viability (76% versus 90%), but increased BMP-2 production (619 ng/mL versus 43 pg/mL). Ten percent and 25% AdBMP-2 transduction had Bern scores of 6.8 and 6.5 and viability of 84% and 83%, respectively. Twenty-five percent mosaic grafts provided better healing histologically than marrow stimulation or naive neocartilage., Conclusions: Low-level AdBMP-2 and CDM augment neocartilage parameters in vitro and vivo., Clinical Relevance: Genetic augmentation of jCh and creation of mosaic neocartilage may improve graft viability and articular healing compared with naïve neocartilage.