Surgically induced degenerative changes in the femorotibial joints by total medial meniscectomy in minipigs closely resemble late-stage osteoarthritis

Animal models of osteoarthritis (OA) have played a key role in understanding the etiology of OA and in the development of new therapeutic strategies. Although pigs have an advantage as an animal disease model due to their similarity to humans, there are few studies on the induction of OA in minipigs. Therefore, this study aimed to characterize disease progression of OA in total medial meniscectomy (TMM)-operated skeletally mature minipigs, up to day 180 postoperatively. There were no significant alterations in vital signs or hematological indices throughout the observation period. However, clinical manifestations of OA in the medial femoral condyles of TMM-operated minipigs were progressive, depending on postoperative duration, with respect to osteophytes formation and roughened surfaces on radiological observation, cartilage erosion under macroscopic examination, and severe cartilage defects including fibrillation, vertical fissures, and cartilage denuding on histopathological observation, with the highest score indicating late-stage OA on day 180 and without indicating apparent variation between subjects. In particular, the lateral femoral condyles were also degenerated, possibly due to localization of weight-bearing from both menisci to the lateral meniscus. Therefore, TMM in minipigs is suitable for reproducible induction of degenerative changes in the femorotibial joints that closely resemble late-stage OA, and is suitable for use in further research.