Objective: Osteoarthritis (OA) is a chronic degenerative disease of the joints characterized by articular cartilage degradation. While there are clear sex differences in OA development in humans, most pre-clinical research has been conducted solely in male animals thus limiting the ability of these findings to be generalized to both sexes in the context of this disease. The objective of this study was to determine if sex impacts the progression and severity of OA in the rat medial meniscal tear (MMT) preclinical animal model used to surgically induce OA. It was hypothesized that differences would be observed between males and females following MMT surgery. Design: A MMT model was employed in male and female Lewis rats to induce OA. Animals were euthanized 3 weeks post-surgery and EPIC-μCT was used to quantitatively evaluate articular cartilage structure and composition, osteophyte volumes and subchondral bone structure. Results: Quantitative analysis of the medial 1/3 articular cartilage via EPIC-μCT showed increased cartilage thickness and proteoglycan loss in the MMT of both sexes, when compared to sham. Additionally, both male and female animals in the MMT group had increased subchondral bone mineral density and larger total osteophyte volumes due to MMT. Conclusion: These data demonstrate that OA can be induced in both sexes using the rat MMT model. Moving forward, adding sex as a factor in preclinical OA studies should be standard practice in pre-clinical studies in order to elucidate more inclusive and translatable results into the clinic.

Characterization of OA development between sexes in the rat medial meniscal transection model