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The effects of gender affirming hormone therapy (GAHT) on bone microarchitecture and fracture risk in adult transgender women is unclear. To investigate the concept that skeletal integrity and strength in trans women may be improved by treatment with a higher dose of GAHT than commonly prescribed, we treated adult male mice with a sustained, high dose of estradiol. Adult male mice at 16 weeks of age were administered ~1.3 mg estradiol by silastic implant, implanted intraperitoneally, for 12 weeks. Controls included vehicle treated intact females and males. High-dose estradiol treatment in males stimulated the endocortical deposition of bone at the femoral mid-diaphysis, increasing cortical thickness and bone area. This led to higher stiffness, maximum force, and the work required to fracture the bone compared to male controls, while post-yield displacement was unaffected. Assessment of the material properties of the bone showed an increase in both elastic modulus and ultimate stress in the estradiol treated males. Treatment of male mice with high dose estradiol was also anabolic for trabecular bone, markedly increasing trabecular bone volume, number and thickness in the distal metaphysis which was accompanied by an increase in the histomorphometric markers of bone remodelling, mineralizing surface/bone surface, bone formation rate and osteoclast number. In conclusion, a high dose of estradiol is anabolic for cortical and trabecular bone in a male to female transgender mouse model, increasing both stiffness and strength. These findings suggest that increasing the current dose of GAHT administered to trans women, while considering other potential adverse effects, may be beneficial to preserving their bone microstructure and strength., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Rachel A Davey reports financial support was provided by Sir Edward Dunlop Medical Research Foundation. Rachel A Davey reports financial support was provided by Austin Health Medical Research Foundation. Rachel A Davey and Jeffrey D Zajac reports financial support was provided by Les and Eva Erdi Research Grant. Tian Nie reports financial support was provided by Endocrine Society of Australia. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)

Objective: Traditional quantitative analysis of bone microstructure in micro-computed tomography (microCT) is dependent on animal scale and requires parametric tuning in new implementations. This study aims to develop an automated and resolution-invariant 3D image processing workflow for quantitative assessment of osteophytes., Methods: In this workflow, cortical bone was segmented from microCT scans, and a 3D sphere-fitting transform was performed to obtain a thickness map, for which each voxel is assigned a thickness value corresponding to the size of the largest sphere containing the voxel that fits entirely within the cortical bone. From the thickness map, a 1-voxel thick outer surface was extracted to model surface roughness. The thickness values of the outer surface were empirically estimated by a series of known statistical distributions. Resulting parameters describing best-fit distributions, along with other cortical bone metrics, were analysed to determine sensitivity to osteoarthritis and the presence of osteophytes., Results: The workflow was validated using microCT scans and histological gradings of rabbit and rat tibiofemoral joints. Visual inspection shows that samples with osteoarthritis and the presence of osteophytes have more surface voxels assigned small thickness values. The distribution of surface thickness values for each animal is best described by Gamma distributions, whose shape parameter is consistently sensitive to osteoarthritis and the presence of osteophytes., Conclusion: Combining traditional image processing with empirical distribution fitting provides an automated, objective, and resolution-invariant workflow for osteophyte assessment., Significance: The proposed method is simple, yet elegant in its implementation, and can be readily used in new implementations.

Objectives: The Outcome Measures in Rheumatology Clinical Trials (OMERACT) Emerging Leaders Program (ELP) aims to cultivate a cohort of skilled leaders within the OMERACT community empowering them with expertise and knowledge to help shape and steer the organization into the future. This publication highlights the significance of the ELP in driving leadership excellence, its impact on OMERACT's evolution, and the outcomes and learnings from the OMERACT 2023 ELP., Methods: Insights from the 2018 ELP report informed 2023 program improvements. Engagement was measured by attendance and WhatsApp interactions. Positive program aspects, areas for improvement and ideas for enhancing future ELPs were captured via anonymous survey and participant focus groups., Results: Engagement with the ELP was high with 9 participants, 96 % attendance at all workshops, 154 WhatsApp interactions. All program components were highly rated, with the highest being the 'Psychological Safety' and 'Methodology/Process/Politics' workshops. Future enhancements included creating further networking, connection and support activities, practical leadership and methodological skill development opportunities, and a new stream focussing on organisational advancement., Conclusions: The 2023 OMERACT ELP was well received and successfully addressed areas previously identified as requiring improvement. New educational enhancements were valued, and the importance of fostering psychological safety at all levels was highlighted. The ELP fortifies OMERACT by nurturing a diverse array of skilled leaders who embody OMERACTs core values. Continuing to refine and evolve the ELP over time will help OMERACT sustain its global influence in patient-centered outcome research., Competing Interests: Declaration of competing interest None of the authors has any competing interests to declare., (Copyright © 2024. Published by Elsevier Inc.)

Glycosaminoglycans (GAGs) are ubiquitous components in the cartilage extracellular matrix (ECM). Ultrastructural arrangement of ECM and GAG-mediated interactions with collagen are known to govern the mechanics in articular cartilage, but these interactions are less clear in other cartilage types. Therefore, this article reviews the current literature on ultrastructure of articular, auricular, meniscal, and nasal septal cartilage, seeking insight into GAG-mediated interactions influencing mechanics. Ultrastructural features of these cartilages are discussed to highlight differences between them. GAG-mediated interactions are reviewed under two categories: interactions with chondrocytes and interactions with other fibrillar macromolecules of the ECM. Moreover, efforts to replicate GAG-mediated interactions to improve mechanical integrity of tissue-engineered cartilage constructs are discussed. In conclusion, studies exploring cartilage specific GAGs are poorly represented in the literature, and the ultrastructure of nasal septal and auricular cartilage is less studied compared with articular and meniscal cartilages. Understanding the contribution of GAGs in cartilage mechanics at the ultrastructural level and translating that knowledge to engineered cartilage will facilitate improvement of cartilage tissue engineering approaches.

The effects of gender-affirming hormone therapy on the skeletal integrity and fracture risk in transitioning adolescent trans girls are unknown. To address this knowledge gap, we developed a mouse model to simulate male-to-female transition in human adolescents in whom puberty is first arrested by using gonadotrophin-releasing hormone analogs with subsequent estradiol treatment. Puberty was suppressed by orchidectomy in male mice at 5 weeks of age. At 3 weeks post-surgery, male-to-female mice were treated with a high dose of estradiol (~0.85 mg) by intraperitoneal silastic implantation for 12 weeks. Controls included intact and orchidectomized males at 3 weeks post-surgery, vehicle-treated intact males, intact females and orchidectomized males at 12 weeks post-treatment. Compared to male controls, orchidectomized males exhibited decreased peak bone mass accrual and a decreased maximal force the bone could withstand prior to fracture. Estradiol treatment in orchidectomized male-to-female mice compared to mice in all control groups was associated with an increased cortical thickness in the mid-diaphysis, while the periosteal circumference increased to a level that was intermediate between intact male and female controls, resulting in increased maximal force and stiffness. In trabecular bone, estradiol treatment increased newly formed trabeculae arising from the growth plate as well as mineralizing surface/bone surface and bone formation rate, consistent with the anabolic action of estradiol on osteoblast proliferation. These data support the concept that skeletal integrity can be preserved and that long-term fractures may be prevented in trans girls treated with GnRHa and a sufficiently high dose of GAHT. Further study is needed to identify an optimal dose of estradiol that protects the bone without adverse side effects., (© 2023. The Author(s).)

Objective: To systematically review the published parameters for the assessment of subchondral bone in human osteoarthritis (OA) using computed tomography (CT) and gain an overview of current practices and standards., Design: A literature search of Medline, Embase and Cochrane Library databases was performed with search strategies tailored to each database (search from 2010 to January 2023). The search results were screened independently by two reviewers against pre-determined inclusion and exclusion criteria. Studies were deemed eligible if conducted in vivo/ex vivo in human adults (>18 years) using any type of CT to assess subchondral bone in OA. Extracted data from eligible studies were compiled in a qualitative summary and formal narrative synthesis., Results: This analysis included 202 studies. Four groups of CT modalities were identified to have been used for subchondral bone assessment in OA across nine anatomical locations. Subchondral bone parameters measuring similar features of OA were combined in six categories: (i) microstructure, (ii) bone adaptation, (iii) gross morphology (iv) mineralisation, (v) joint space, and (vi) mechanical properties., Conclusions: Clinically meaningful parameter categories were identified as well as categories with the potential to become relevant in the clinical field. Furthermore, we stress the importance of quantification of parameters to improve their sensitivity and reliability for the evaluation of OA disease progression and the need for standardised measurement methods to improve their clinical value., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

Bone erosions are a pathological feature of several forms of inflammatory arthritis including rheumatoid arthritis (RA). The increased presence and size of erosions are associated with poor outcomes, joint function, and disease progression. High-resolution peripheral quantitative computed tomography (HR-pQCT) provides unparalleled in vivo visualization of bone erosions. However, at this resolution, discontinuities in the cortical shell (cortical breaks) that are associated with normal physiological processes and pathology are also visible. The Study grouP for xtrEme Computed Tomography in Rheumatoid Arthritis previously used a consensus process to develop a definition of pathological erosion in HR-pQCT: a cortical break detected in at least two consecutive slices, in at least two perpendicular planes, non-linear in shape, with underlying trabecular bone loss. However, despite the availability of a consensus definition, erosion identification is a demanding task with challenges in inter-rater variability. The purpose of this work is to introduce a training tool to provide users with guidance on identifying pathological cortical breaks on HR-pQCT images for erosion analysis. The protocol presented here uses a custom-built module (Bone Analysis Module (BAM) - Training), implemented as an extension to an open-source image processing software (3D Slicer). Using this module, users can practice identifying erosions and compare their results to erosions annotated by expert rheumatologists.

Purpose of Review: Rigid image registration is an important image processing tool for the assessment of musculoskeletal chronic disease. In this paper, we critically review applications of rigid image registration in terms of similarity measurement methods over the past three years (2019-2022) in the context of monitoring longitudinal changes to bone microstructure and mechanical properties using computed tomography. This review identifies critical assumptions and trade-offs underlying different similarity measurement methods used in image registration and demonstrates the effect of using different similarity measures on registration outcomes., Recent Findings: Image registration has been used in recent studies for: correcting positional shifts between longitudinal scans to quantify changes to bone microstructural and mechanical properties over time, developing registration-based workflows for longitudinal assessment of bone properties in pre-clinical and clinical studies, and developing and validating registration techniques for longitudinal studies. In evaluating the recent literature, it was found that the assumptions at the root of different similarity measures used in rigid image registration are not always confirmed and reported. Each similarity measurement has its advantages and disadvantages, as well as underlying assumptions. Breaking these assumptions can lead to poor and inaccurate registration results. Thus, care must be taken with regards to the choice of similarity measurement and interpretation of results. We propose that understanding and verifying the assumptions of similarity measurements will enable more accurate and efficient quantitative assessments of structural changes over time., (© 2023. The Author(s).)

Exploring the structure-function relationships of cartilage on a microstructural level is crucial for tissue engineering approaches aiming to restore function. Therefore, a combination of mechanical testing with cell and tissue-level imaging would allow for longitudinal studying loading mechanisms, biological responses and mechanoadaptation of tissues at a microstructural level. This paper describes the design and validation of FELIX, a custom-built device for non-destructive image-guided micromechanical evaluation of biological tissues and tissue-engineered constructs. It combines multiphoton microscopy with non-destructive mechanical testing of native soft tissues. Ten silicone samples of the same size were mechanically tested with FELIX by different users to assess the repeatability and reproducibility. The results indicate that FELIX can successfully substitute mechanical testing protocols with a commercial device without compromising precision. Furthermore, FELIX demonstrated consistent results across repeated measurements, with very small deviations. Therefore, FELIX can be used to accurately measure biomechanical properties by different users for separate studies. Additionally, cell nuclei and collagen of porcine articular cartilage were successfully imaged under compression. Cell viability remained high in chondrocytes cultured in agarose over 21 days. Furthermore, there were no signs of contamination indicating a cell friendly, sterile environment for longitudinal studies. In conclusion, this work demonstrates that FELIX can consistently quantify mechanical measures without compromising precision. Furthermore, it is biocompatible allowing for longitudinal measurements., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Kathryn Stok reports a relationship with RegMed XB Moonshot International Scientific Advisory Board that includes: consulting or advisory., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Chondrocytes and osteoblasts differentiated from induced pluripotent stem cells (iPSCs) will provide insights into skeletal development and genetic skeletal disorders and will generate cells for regenerative medicine applications. Here, we describe a method that directs iPSC-derived sclerotome to chondroprogenitors in 3D pellet culture then to articular chondrocytes or, alternatively, along the growth plate cartilage pathway to become hypertrophic chondrocytes that can transition to osteoblasts. Osteogenic organoids deposit and mineralize a collagen I extracellular matrix (ECM), mirroring in vivo endochondral bone formation. We have identified gene expression signatures at key developmental stages including chondrocyte maturation, hypertrophy, and transition to osteoblasts and show that this system can be used to model genetic cartilage and bone disorders.

Hereditary hemochromatosis (HH) causes unbalanced iron deposition in many organs including the joints leading to severe cartilage loss and bone damage in the metacarpophalangeal joints (MCPJ). High-resolution peripheral quantitative computed tomography (HR-pQCT) and its joint space width (JSW) quantification algorithm quantifies in vivo 3D joint morphology. We therefore aimed to (i) determine feasibility and performance of the JSW algorithm in HH, (ii) quantify joint space morphology, and (iii) investigate the relationship between morphological and clinical parameters in HH. Here, we performed an exploratory study on 24 HH patients and sex- and age-matched controls using HR-pQCT imaging of MCPJ. Mineralized bone structure was automatically segmented from the grayscale image data and periosteal surface bone masks and joint space masks were generated. Mean, minimal, and maximal joint space width (JSW; JSW.MIN; JSW.MAX), JSW heterogeneity (JSW.SD), JSW asymmetry (JSW.AS), and joint space volume (JSV) were computed. Demographics and, for HH patients, disease-specific parameters were recorded. Segmentation of JS was very good with 79.7% of MCPJs successfully segmented at first attempt and 20.3% requiring semi-manual correction. HH men showed larger JSV at all MCPs (+ 25.4% < JSV <  + 41.8%, p < 0.05), larger JSW.MAX at MCP 3-4 (+ 14%, 0.006 < p < 0.062), and wider JSW (+ 13%, p = 0.043) at MCP 4 relative to HH women. Compared to controls, both HH men and HH women showed larger JSW.AS and smaller JSW.MIN at all MCP levels, reaching significance for HH men at MCP 2 and 3 (JSW.AS: + 323% < JSW.AS <  + 359%, 0.020 < p < 0.043; JSW.MIN: - 216% < JSW.MIN < - 225%, p < 0.043), and for women at MCP 3 (JSW.AS: + 180%, p = 0.025; JSW.MIN: - 41.8%, p = 0.022). Time since HH diagnosis was correlated positively with MCP 4 JSW.AS and JSW.SD (0.463 < ρ < 0.499, p < 0.040), and the number of phlebotomies since diagnosis was correlated with JSW.SD at all MCPs (0.432 < ρ < 0.535, p < 0.050). HR-pQCT-based JSW quantification in MCPJ of HH patients is feasible, performs well even in narrow JS, and allows to define the microstructural joint burden of HH., (© 2023. The Author(s).)

Osteoarthritis (OA) is a chronic joint disease that causes disability and pain. The osteochondral interface is a gradient tissue region that plays a significant role in maintaining joint health. It has been shown that during OA, increased neoangiogenesis creates porous channels at the osteochondral interface allowing the transport of molecules related to OA. Importantly, the connection between these porous channels and the early stages of OA development is still not fully understood. Microcomputed tomography (microCT) offers the ability to image the porous channels at the osteochondral interface, however, a contrast agent is necessary to delineate the different X-ray attenuations of the tissues. In this study BaYbF 5 -SiO 2 nanoparticles are synthesized and optimized as a microCT contrast agent to obtain an appropriate contrast attenuation for subsequent segmentation of structures of interest, that is, porous channels, and mouse subchondral bone. For this purpose, BaYbF 5 nanoparticles were synthesized and coated with a biocompatible silica shell (SiO 2 ). The optimized BaYbF 5 -SiO 2 27 nm nanoparticles exhibited the highest average microCT attenuation among the biocompatible nanoparticles tested. The BaYbF 5 -SiO 2 27 nm nanoparticles increased the mean X-ray attenuation of structures of interest, for example, porous channel models and mouse subchondral bone. The BaYbF 5 -SiO 2 contrast attenuation was steady after diffusion into mouse subchondral bone. In this study, we obtained for the first time, the average microCT attenuation of the BaYbF 5 -SiO 2 nanoparticles into porous channel models and mouse subchondral bone. In conclusion, BaYbF 5 -SiO 2 nanoparticles are a potential contrast agent for imaging porous channels at the osteochondral interface using microCT., (© 2022 The Authors. Journal of Orthopaedic Research® published by Wiley Periodicals LLC on behalf of Orthopaedic Research Society.)

Micro-computed tomography (microCT) offers a three-dimensional (3D), high-resolution technique for the visualisation and analysis of bone microstructure. Using contrast-enhanced microCT, this capability has been expanded in recent studies to include cartilage morphometry and whole joint measures, known together as quantitative morphometric analysis (QMA). However, one of the main challenges in quantitative analysis of joint images is sensitivity to joint pose and alignment, which may influence measures related to both joint space and joint biomechanics. Thus, this study proposes a novel microCT imaging protocol for reproducible and efficient QMA of in situ mouse tibio-femoral joint. This work consists of two parts: an in situ diffusion kinetics study for a known cationic iodinated contrast agent (CA4+) for QMA of the cartilage, and a joint positioning and image processing workflow for whole joint QMA. In the diffusion kinetics study, 8 mice were injected at both of their tibio-femoral joints with distinct CA4+ concentrations and diffusion times. The mice were scanned at different time points after injection, and evaluated using attenuation and cartilage QMA measures. Results show that cartilage segmentation and QMA could be performed for CA4+ solution at a concentration of 48 mg/ml, and that reliable measurement and quantification of cartilage were achieved after 5 min of diffusion following contrast agent injection. We established the joint positioning and image processing workflow by developing a novel positioning device to control joint pose during scanning, and a spherical harmonics-based image processing workflow to ensure consistent alignment during image processing. Both legs of seven mice were scanned 10 times, 5 prior to receiving CA4+ and 5 after, and evaluated using whole joint QMA parameters. Joint QMA evaluation of the workflow showed excellent reproducibility; intraclass correlation coefficients ranged from 0.794 to 0.930, confirming that the imaging protocol enables reproducible and efficient QMA of joint structures in preclinical models, and that contrast agent injection did not cause significant alteration to the measured parameters., Competing Interests: Declaration of competing interest None of the authors has any conflict of interest., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Identification of bone erosions and quantification of erosion volume is important for rheumatoid arthritis diagnosis, and can add important information to evaluate disease progression and treatment effects. High-resolution peripheral quantitative computed tomography (HR-pQCT) is well suited for this purpose, however analysis methods are not widely available. The purpose of this study was to develop an open-source software tool for the identification and quantification of bone erosions using images acquired by HR-pQCT. The collection of modules, Bone Analysis Modules (BAM) - Erosion, implements previously published erosion analysis techniques as modules in 3D Slicer, an open-source image processing and visualization tool. BAM includes a module to automatically identify cortical interruptions, from which erosions are manually selected, and a hybrid module that combines morphological and level set operations to quantify the volume of bone erosions. HR-pQCT images of the second and third metacarpophalangeal (MCP) joints were acquired in patients with RA (XtremeCT, n = 14, XtremeCTII, n = 22). The number of cortical interruptions detected by BAM-Erosion agreed strongly with the previously published cortical interruption detection algorithm for both XtremeCT (r 2  = 0.85) and XtremeCTII (r 2  = 0.87). Erosion volume assessment by BAM-Erosion agreed strongly (r 2  = 0.95) with the Medical Image Analysis Framework. BAM-Erosion provides an open-source erosion analysis tool that produces comparable results to previously published algorithms, with improved options for visualization. The strength of the tool is that it implements multiple image processing algorithms for erosion analysis on a single, widely available, open-source platform that can accommodate future updates., Competing Interests: Declaration of competing interest Bert van Rietbergen is a consultant for Scanco Medical AG. All other authors have stated no conflicts of interest., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

The transfer of stress and strain signals between the extracellular matrix (ECM) and cells is crucial for biochemical and biomechanical cues that are required for tissue morphogenesis, differentiation, growth, and homeostasis. In cartilage tissue, the heterogeneity in spatial variation of ECM molecules leads to a depth-dependent non-uniform strain transfer and alters the magnitude of forces sensed by cells in articular and fibrocartilage, influencing chondrocyte metabolism and biochemical response. It is not fully established how these nonuniform forces ultimately influence cartilage health, maintenance, and integrity. To comprehend tissue remodelling in health and disease, it is fundamental to investigate how these forces, the ECM, and cells interrelate. However, not much is known about the relationship between applied mechanical stimulus and resulting spatial variations in magnitude and sense of mechanical stimuli within the chondrocyte's microenvironment. Investigating multiscale strain transfer and hierarchical structure-function relationships in cartilage is key to unravelling how cells receive signals and how they are transformed into biosynthetic responses. Therefore, this article first reviews different cartilage types and chondrocyte mechanosensing. Following this, multiscale strain transfer through cartilage tissue and the involvement of individual ECM components are discussed. Finally, insights to further understand multiscale strain transfer in cartilage are outlined., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Boos, Lamandé and Stok.)

The accessibility of quantitative measurements of joint morphometry depends on appropriate tibial alignment and volume of interest (VOI) selection of joint compartments; often a challenging and time-consuming manual task. In this work, we developed a novel automatic, efficient, and model-invariant image preprocessing pipeline that allows for highly reproducible 3D quantitative morphometric analysis (QMA) of the joint. The pipeline addresses the problem by deploying two modules: an alignment module and a subdivision module. Alignment is achieved by representing the tibia in its basic form using lower degree spherical harmonic basis functions and aligning using principal component analysis. The second module subdivides the joint into lateral and medial VOIs via a watershedding approach based on persistence homology. Multiple repeated micro-computed tomography scans of small (rat) and medium (rabbit) animal knees were processed using the pipeline to demonstrate model invariance. Existing QMA was performed to evaluate the pipeline's ability to generate reproducible measurements. Intraclass correlation coefficient and mean-normalised root-mean-squared error of more than 0.75 and lower than 9.5%, respectively, were achieved for joint centre of mass, joint contact area under virtual loading, joint space width, and joint space volume. Processing time and technical requirements were reduced compared to manual processing in previous studies., (© 2022. The Author(s).)

Objective: To investigate GAG-ECM (glycosaminoglycan-extracellular matrix) interactions in different cartilage types. To achieve this, we first aimed to determine protocols for consistent calculation of GAG content between cartilage types., Design: Auricular cartilage containing both collagen and elastin was used to determine the effect of lyophilization on GAG depletion activity. Bovine articular, auricular, meniscal, and nasal cartilage plugs were treated using different reagents to selectively remove GAGs. Sulfated glycosaminoglycan (sGAG) remaining in the sample after treatment were measured, and sGAG loss was compared between cartilage types., Results: The results indicate that dry weight of cartilage should be measured prior to cartilage treatment in order to provide a more accurate reference for normalization. Articular, meniscal, and nasal cartilage lost significant amounts of sGAG for all reagents used. However, only hyaluronidase was able to remove significant amount of sGAG from auricular cartilage. Furthermore, hyaluronidase was able to remove over 99% of sGAG from all cartilage types except auricular cartilage where it only removed around 76% of sGAG. The results indicate GAG-specific ECM binding for different cartilage types and locations., Conclusions: In conclusion, lyophilization can be performed to determine native dry weight for normalization without affecting the degree of GAG treatment. To our knowledge, this is the first study to compare GAG-ECM interactions of different cartilage types using different GAG extraction methods. Degree of GAG depletion not only varied with cartilage type but also the same type from different anatomic locations. This suggests specific structure-function roles for GAG populations found in the tissues.

Objective: To compare CA4+-enhanced micro-computed tomography (microCT) of bovine articular, meniscal, nasal, and auricular cartilage, each of which possesses a different extracellular matrix (ECM) composition and structure., Design: The diffusion kinetics of CA4+ in different native cartilage types were assessed over 20 hours. The feasibility of CA4+-enhanced microCT to visualize and quantify glycosaminoglycans (GAGs) in these different tissues was tested using safranin-O staining and 1,9-dimethylmethylene blue assay., Results: The diffusion kinetics of CA4+ in auricular cartilage are significantly slower compared with all other cartilage types. Total GAG content per volume correlates to microCT attenuation with an R 2 value of 0.79 for all cartilage types. Three-dimensional contrast-enhanced microCT images of spatial GAG distribution reflect safranin-O staining and highlight the differences in ECM structure, with heterogeneous regions with higher GAG concentrations highlighted by the contrast agent., Conclusions: CA4+-enhanced microCT enables assessment of 3-dimensiona distribution and GAG content in different types of cartilage and has promise as an ex vivo diagnostic technique to monitor matrix development in different tissues over time as well as tissue-engineered constructs.

Multi-scale, subject-specific quantitative methods to characterize and monitor osteoarthritis in animal models and therapeutic treatments could help reveal causal relationships in disease development and distinguish treatment strategies. In this work, we demonstrate a reproducible and sensitive quantitative image analysis to characterize bone, cartilage and joint measures describing a rat model of post-traumatic osteoarthritis. Eleven 3-month-old male Wistar rats underwent medial anterior cruciate ligament (ACL) transection and medial meniscectomy on the right knee to destabilise the right tibiofemoral joint. They were sacrificed 6 weeks post-surgery and a silicon-based micro-bead contrast agent was injected in the joint space, before scanning with micro-computed tomography (microCT). Subsequently, 3D quantitative morphometric analysis (QMA), previously developed for rabbit joints, was performed. This included cartilage, subchondral cortical and epiphyseal bone measures, as well as novel tibiofemoral joint metrics. Semi-quantitative evaluation was performed on matching two-dimensional (2D) histology and microCT images. Reproducibility of the QMA was tested on eleven age-matched additional joints. The results indicate the QMA method is accurate and reproducible and that microCT-derived cartilage measurements are valid for the analysis of rat joints. The pathologic changes caused by transection of the ACL and medial meniscectomy were reflected in measurements of bone shape, cartilage morphology, and joint alignment. Furthermore, we were able to identify model-specific predictive parameters based on morphometric parameters measured with the QMA., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Objective: The aim of this multireader exercise was to assess the reliability and change over time of erosion measurements in patients with rheumatoid arthritis (RA) using high-resolution peripheral quantitative computed tomography (HR-pQCT)., Methods: HR-pQCT scans of 23 patients with RA were assessed at baseline and 12 months. Four experienced readers examined the dorsal, palmar, radial, and ulnar surfaces of the metacarpal head (MH) and phalangeal base (PB) of the second and third digits, blinded to time order. In total, 368 surfaces (23 patients´ 16 surfaces) were evaluated per timepoint to characterize cortical breaks as pathological (erosion) or physiological, and to quantify erosion width and depth. Reliability was evaluated by intraclass correlation coefficients (ICC), percentage agreement, and Light k; change over time was defined by means ± SD of erosion numbers and dimensions., Results: ICC for the mean measurements of width and depth of the pathological breaks ranged between 0.819-0.883, and 0.771-0.907, respectively. Most physiological cortical breaks were found at the palmar PB, whereas most pathological cortical breaks were located at the radial MH. There was a significant increase in both the numbers and the dimensions of erosions between baseline and follow-up ( P = 0.0001 for erosion numbers, width, and depth in axial plane; P = 0.001 for depth in perpendicular plane)., Conclusion: This exercise confirmed good reliability of HR-pQCT erosion measurements and their ability to detect change over time., (Copyright © 2021 by the Journal of Rheumatology.)

Non-ionic, low-osmolar contrast agents (CAs) used for computed tomography, such as Optiray (ioversol) and Iomeron (iomeprol), are associated with the reduced risk of adverse reactions and toxicity in comparison with ionic CAs, such as Hexabrix. Hexabrix has previously been used for imaging articular cartilage but has been commercially discontinued. This study aimed to evaluate the efficacy of Optiray and Iomeron as alternatives for visualisation of articular cartilage in small animal joints using contrast-enhanced micro-computed tomography (CECT). For this purpose, mouse femora were immersed in different concentrations (20%-50%) of Optiray 350 or Iomeron 350 for periods of time starting at five minutes. The femoral condyles were scanned ex vivo using CECT, and regions of articular cartilage manually contoured to calculate mean attenuation at each time point and concentration. For both CAs, a 30% CA concentration produced a mean cartilage attenuation optimally distinct from both bone and background signal, whilst 5-min immersion times were sufficient for equilibration of CA absorption. Additionally, plugs of bovine articular cartilage were digested by chondroitinase ABC to produce a spectrum of glycosaminoglycan (GAG) content. These samples were immersed in CA and assessed for any correlation between mean attenuation and GAG content. No significant correlation was found between attenuation and cartilage GAG content for either CAs. In conclusion, Optiray and Iomeron enable high-resolution morphological assessment of articular cartilage in small animals using CECT; however, they are not indicative of GAG content., (© 2020 Anatomical Society.)

Articular joints are comprised of different tissues, including cartilage and bone, with distinctive structural and mechanical properties. Joint homeostasis depends on mechanical and biological integrity of these components and signaling exchanges between them. Chondrocytes and osteocytes actively sense, integrate, and convert mechanical forces into biochemical signals in cartilage and bone, respectively. The osteochondral interface between the bone and cartilage allows these tissues to communicate with each other and exchange signaling and nutritional molecules, and by that ensure an integrated response to mechanical stimuli. It is currently not well known how molecules are transported between these tissues. Measuring molecular transport in vivo is highly desirable for tracking cartilage degeneration and osteoarthritis progression. Since transport of contrast agents, which are used for joint imaging, also depend on diffusion through the cartilage extracellular matrix, contrast agent enhanced imaging may provide a high resolution, non-invasive method for investigating molecular transport in the osteochondral unit. Only a few techniques have been developed to track molecular transport at the osteochondral interface, and there appear opportunities for development in this field. This review will describe current knowledge of the molecular interactions and transport in the osteochondral interface and discuss the potential of using contrast agents for investigating molecular transport and structural changes of the joint., (Copyright © 2020 Oliveira Silva, Gregory, Ansari and Stok.)

Background: Joint space assessment for rheumatoid arthritis (RA) by ordinal conventional radiographic scales is susceptible to floor and ceiling effects. High-resolution peripheral quantitative computed tomography (HR-pQCT) provides superior resolution, and may detect earlier changes. The goal of this work was to compare existing 3D methods to calculate joint space width (JSW) metrics in human metacarpophalangeal (MCP) joints with HR-pQCT and reach consensus for future studies. Using the consensus method, we established reproducibility with repositioning as well as feasibility for use in second-generation HR-pQCT scanners., Methods: Three published JSW methods were compared using datasets from individuals with RA from three research centers. A SPECTRA consensus method was developed to take advantage of strengths of the individual methods. Using the SPECTRA method, reproducibility after repositioning was tested and agreement between scanner generations was also established., Results: When comparing existing JSW methods, excellent agreement was shown for JSW minimum and mean (ICC 0.987-0.996) but not maximum and volume (ICC 0.000-0.897). Differences were identified as variations in volume definitions and algorithmic differences that generated high sensitivity to boundary conditions. The SPECTRA consensus method reduced this sensitivity, demonstrating good scan-rescan reliability (ICC >0.911) except for minimum JSW (ICC 0.656). There was strong agreement between results from first- and second-generation HR-pQCT (ICC >0.833)., Conclusions: The SPECTRA consensus method combines unique strengths of three independently-developed algorithms and leverages underlying software updates to provide a mature analysis to measure 3D JSW. This method is robust with respect to repositioning and scanner generations, suggesting its suitability for detecting change., Competing Interests: Conflicts of Interest: KS Stok and V Stadelmann are former employees of Scanco Medical AG. N Vilayphiou is a current employee of Scanco Medical AG. The other authors have no conflicts of interest to declare., (2020 Quantitative Imaging in Medicine and Surgery. All rights reserved.)

Objective: We assessed construct validity of high-resolution peripheral quantitative computed tomography (HR-pQCT) joint space outcomes by comparison with radiographs in patients with rheumatoid arthritis., Methods: In 43 patients, quantitative, volumetric, HR-pQCT measurements were compared with ordinal Sharp/van der Heijde scoring (SvdH) in the 2nd and 3rd metacarpophalangeal joints., Results: Generalized estimating equations showed that joint space minimum, SD, and asymmetry by HR-pQCT were associated with SvdH scores (p < 0.05). There was a considerable range in HR-pQCT measurements at SvdH equal to 0., Conclusion: HR-pQCT demonstrated construct validity outcomes and provides improved 3-D visualization of joint space.

Objective: To describe the experience of the first OMERACT Emerging Leaders Program (ELP)., Methods: A Delphi process identified positive aspects, areas for improvement, and future directions. Core items were defined as essential if they received ≥ 70% ratings., Results: Participants valued relatable/accessible mentors (100%), including an OMERACT Executive mentor (100%), and a support network of peers (90%). Key items for future development were funding support (100%) and developing knowledge about OMERACT processes (90%) and politics (80%)., Conclusion: The ELP has the potential to provide targeted training for early career researchers to develop relevant skills for future leadership roles within OMERACT.

Decellularized tissue matrices are promising substrates for tissue generation by stem cells to replace poorly regenerating tissues such as cartilage. However, the dense matrix of decellularized cartilage impedes colonisation by stem cells. Here, we show that digestion of elastin fibre bundles traversing auricular cartilage creates channels through which cells can migrate into the matrix. Human chondrocytes and bone marrow-derived mesenchymal stromal cells efficiently colonise elastin-treated scaffolds through these channels, restoring a glycosaminoglycan-rich matrix and improving mechanical properties while maintaining size and shape of the restored tissue. The scaffolds are also rapidly colonised by endogenous cartilage-forming cells in a subcutaneously implanted osteochondral biopsy model. Creating channels for cells in tissue matrices may be a broadly applicable strategy for recellularization and restoration of tissue function.

Hair cells are specialized mechanosensitive cells responsible for mediating balance and hearing within the inner ear. In mammals, hair cells are limited in number and do not regenerate. Human pluripotent stem cells (hPSCs) provide a valuable source for deriving human hair cells to study their development and design therapies to treat and/or prevent their degeneration. In this study we used a dynamic 3D Rotary Cell Culture System (RCCS) for deriving inner ear organoids from hPSCs. We show RCCS-derived organoids recapitulate stages of inner ear development and give rise to an enriched population of hair cells displaying vestibular-like morphological and physiological phenotypes, which resemble developing human fetal inner ear hair cells as well as the presence of accessory otoconia-like structures. These results show that hPSC-derived organoids can generate complex inner ear structural features and be a resource to study inner ear development.