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Osteoarthritis (OA) is a widespread disease that continues to lack approved and efficacious treatments that modify disease progression. Micronized dehydrated human amnion/chorion membrane (μ-dHACM) has been shown to be effective in reducing OA progression, but many of the engineering design parameters have not been explored. The objectives of this study were to characterize the particle size distributions of two μ-dHACM formulations and to investigate the influence of these distributions on the in vivo therapeutic efficacy of μ-dHACM. Male Lewis rats underwent medial meniscus transection (MMT) or sham surgery, and intra-articular injections of saline, μ-dHACM, or reduced particle size μ-dHACM (RPS μ-dHACM) were administered at 24 hours postsurgery ( n  = 9 per treatment group). After 3 weeks, the animals were euthanized, and left legs harvested for equilibrium partitioning of an ionic contrast agent microcomputed tomography and histological analysis. μ-dHACM and RPS μ-dHACM particles were fluorescently tagged and particle clearance was tracked in vivo for up to 42 days postsurgery. Protein elution from both formulations was quantified in vitro . Treatment with μ-HACM, but not RPS μ-dHACM, reduced lesion volume in the MMT model 3 weeks postsurgery. In contrast, RPS μ-dHACM increased cartilage surface roughness and osteophyte cartilage thickness and volume compared to saline treatment. There was no difference of in vivo fluorescently tagged particle clearance between the two μ-dHACM sizes. RPS μ-dHACM showed significantly greater protein elution in vitro over 21 days. Overall, delivery of RPS μ-dHACM did result in an increase of in vivo joint degeneration and in vitro protein elution compared to μ-dHACM, but did not result in differences in joint clearance in vivo . These results suggest that particle size and factor elution may be tailorable factors that are important to optimize for particulate amniotic membrane treatment to be an effective therapy for OA. Impact Statement Osteoarthritis (OA) is a widespread disease that continues to lack treatments that modify the progression of the disease. Micronized dehydrated human amnion/chorion membrane (μ-dHACM) has been shown to be effective in reducing OA progression, but many of the engineering design parameters have not been explored. This work investigates the effects of particle size profile of the μ-dHACM particles and lays out the methods used in these studies. The results of this work will guide engineers in designing μ-dHACM treatments specifically and disease-modifying OA therapeutics generally, and it demonstrates the utility of novel therapeutic evaluation methods such as contrast-enhanced microcomputed tomography.

Introduction: Micronized dehydrated human amnion/chorion membrane (μ-dHACM) is derived from donated human placentae and has anti-inflammatory, low immunogenic and anti-fibrotic properties. The objective of this study was to quantitatively assess the efficacy of μ-dHACM as a disease modifying intervention in a rat model of osteoarthritis (OA). It was hypothesized that intra-articular injection of μ-dHACM would attenuate OA progression., Methods: Lewis rats underwent medial meniscal transection (MMT) surgery to induce OA. Twenty four hours post-surgery, μ-dHACM or saline was injected intra-articularly into the rat joint. Naïve rats also received μ-dHACM injections. Microstructural changes in the tibial articular cartilage were assessed using equilibrium partitioning of an ionic contrast agent (EPIC-μCT) at 21 days post-surgery. The joint was also evaluated histologically and synovial fluid was analyzed for inflammatory markers at 3 and 21 days post-surgery., Results: There was no measured baseline effect of μ-dHACM on cartilage in naïve animals. Histological staining of treated joints showed presence of μ-dHACM in the synovium along with local hypercellularity at 3 and 21 days post-surgery. In MMT animals, development of cartilage lesions at 21 days was prevented and number of partial erosions was significantly reduced by treatment with μ-dHACM. EPIC-μCT analysis quantitatively showed that μ-dHACM reduced proteoglycan loss in MMT animals., Conclusions: μ-dHACM is rapidly sequestered in the synovial membrane following intra-articular injection and attenuates cartilage degradation in a rat OA model. These data suggest that intra-articular delivery of μ-dHACM may have a therapeutic effect on OA development.

The dog is the most commonly used large animal model for the study of osteoarthritis. Optimizing methods for assessing cartilage health would prove useful in reducing the number of dogs needed for a valid study of osteoarthritis and cartilage repair. Twelve beagles had critical‐sized osteochondral defects created in the medial femoral condyle of both knees. Eight dogs had T1ρ and T2 magnetic resonance imaging (MRI) performed approximately 6 months after defect creation. Following MRI evaluations, all 12 dogs were humanely euthanatized and cartilage samples were obtained from the medial and lateral femoral condyles, medial and lateral tibial plateaus, trochlear groove, and patella for proteoglycan and collagen quantification. Equilibrium partitioning of an ionic contrast (EPIC)‐µCT was then performed followed by the histologic assessment of the knees. Correlations between T1ρ, T2, EPIC‐µCT and proteoglycan, collagen, and histology scores were assessed using a multivariate analysis accounting for correlations from samples within the same knee and in the same dog. Pearson's correlation coefficients were calculated to assess the strength of significant relationships. Correlations between µCT values and biochemical or histologic assessment were weak to moderately strong (0.09–0.41; p < 0.0001–0.66). There was a weak correlation between the T2 values and cartilage proteoglycan (−0.32; p = 0.04). The correlation between T1ρ values and cartilage proteoglycan were moderately strong (−0.38; p < 0.05) while the strongest correlation was between the T1ρ values and histological assessment of cartilage with a correlation coefficient of 0.58 (p < 0.0001). These data suggest that T1ρ shows promise for possible utility in the translational study of cartilage health and warrants further development in this species. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:368‐377, 2020 [ABSTRACT FROM AUTHOR]

Objective To assess temporal changes in cartilage and bone morphology, reactive oxygen species (ROS), and vascularization in rats with monosodium iodoacetate (MIA)-induced osteoarthritis (OA), using advanced imaging methodologies. Methods Right knees of 8-week-old male Wistar rats were injected with 1 mg MIA in 50 μl saline and left knees were injected with 50 μl saline as controls. After 1, 2, and 3 weeks (n = 5 at each time point), changes in cartilage morphology and composition were quantified using equilibrium partitioning of an ionic contrast agent microfocal computed tomography (μCT), and changes in subchondral and trabecular bone were assessed by standard μCT. ROS were characterized by in vivo fluorescence imaging at 1, 11, and 21 days (n = 5 at each time point). Three weeks following fluorescence imaging, alterations in knee joint vascularity were quantified with μCT after perfusion of a vascular contrast agent. Results Femoral cartilage volume, thickness, and proteoglycan content were significantly decreased in MIA-injected knees compared with control knees, accompanied by loss of trabecular bone and erosion of subchondral bone surface. ROS quantities were significantly increased 1 day after MIA injection and subsequently decreased gradually, having returned to normal by 21 days. Vascularity in whole knees and distal femora was significantly increased at 21 days after MIA injection. Conclusion Contrast-enhanced μCT and fluorescence imaging were combined to characterize articular cartilage, subchondral bone, vascularization, and ROS, providing unprecedented 3-dimensional joint imaging and quantification in multiple tissues during OA progression. These advanced imaging techniques have the potential to become standardized methods for comprehensive evaluation of articular joint degeneration and evaluation of therapeutic efficacy. [ABSTRACT FROM AUTHOR]