Synovial mesenchymal stem cells effectively alleviate osteoarthritis through promoting the proliferation and differentiation of meniscus chondrocytes.

Abstract

To investigate the relationship between the meniscal defect area and OA progression and explore the effect and mechanism of SMSCs cell therapy in knee osteoarthritis (OA) rat model. For animal experiments, knee osteoarthritis (OA) model was constructed in Sprague Dawley (SD) rats by removing the medial meniscus of the right knee. Synovial mesenchymal stem cells (SMSCs) were engrafted by injecting into the right knee cavity. For in vitro experiments, CCK-8 assay was performed to evaluate the proliferation and differentiation of BMSCs and ATDC5 cells after co-cultured with SMSCs. qRT-PCR analysis was performed to detect the expressions of chondrogenic genes in BMSCs and ATDC5 cells after co-cultured with SMSCs. Western blot analysis was conducted to detect the phosphorylations of c-Jun N-terminal kinase (JNK) and extracellular regulated protein kinases (ERK) in MAPK signaling of BMSCs and ATDC5 cells. Enzyme-linked immunosorbent assay (ELISA) was performed to detect the serum levels of interleukin (IL)-1β, IL-1β, IL-6, IL-18 and C-reactive protein (CRP). Results showed that meniscus damaged area is positively correlated to serum inflammatory factor levels. In vitro study showed that the proliferation and differentiation of BMSCs and ATDC5 cells were promoted after co-cultured with SMSCs. By co-culturing with SMSCs, the MAPK signaling pathway was activated and the expression of chondrogenic markers such as aggrecan (acan), SRY-related high mobility group-box gene 9 (sox9) and Type II collagen a1 (col2a1), was up-regulated both in BMSCs and ATDC5 cells. In vivo study showed SMSCs cell therapy significantly decreased serum inflammatory factor levels and protected cartilage by upregulating the expression of chondrogenic genes of meniscus chondrocytes derived from OA rats. For the first time, we found the positive correlation between meniscal defect area and OA progression and demonstrated the effect and mechanism of SMSCs cell therapy in knee osteoarthritis (OA) treatment.