Synovial fluid-derived mesenchymal cells have non-inferior chondrogenic potential and can be utilized for regenerative therapy as substitute for synovium-derived cells.

Recent progress in the field of mesenchymal stem cell (MSC) biology has enabled their clinical application. In the autologous cell transplantation therapy, the source of MSCs are quite important to reduce patients' physical burden. In this study, we isolated MSCs from the synovial fluid (SF) and synovial membrane (Syn) of the same patients and compared the biological characteristics of them. In vitro and in vivo experiments indicated the non-inferior chondrocytic differentiation and articular cartilage regeneration potential of SF-MSCs compared to that of Syn-MSCs; however, SF-MSCs showed less proliferative potential than Syn-MSCs in vitro. Flow cytometry-based multiplex surface antigen expression analyses indicated that SF-MSCs exhibit fewer cells positive for CD140, which is a functional growth factor receptor for MSCs. Nevertheless, we obtained enough SF-MSCs for transplantation within several passages. Since arthrocentesis is routinely performed during outpatient care in the consultation room and is less invasive than synovial biopsy, MSC derived from synovial fluid could be considered an attractive cell source for cartilage regenerative therapy as a substitute for Syn-MSC. Developing these cells for clinical application may greatly benefit patients undergoing autologous MSC transplantation therapy.