Abstract: Objective: To study the role of secreted factors by chondrocytes to induce chondrogenesis of synovial mesenchymal stem cells. Methods: The synovial mesenchymal stem cells (SMSCs) and chondrocytes were harvested from rat knee joints and cultured through the digestion method. The supernatant was collected from chondrocytes, centrifuged, filtered, and cryopreserved. Group1: the third passage SMSCs centrifuged as pellets were cultured in the chondrocyte supernatant for 21 days. Group2: SMSCs differentiated under the induction of transforming growth factor beta-1 in the same time. The cells morphology was examined and the type II collagen and aggrecan were detected through immunohistochemistry and RT-PCR. Results: The SMSCs induced became cartilage-like tissue after 21 days. The type II collagen was detected positively in the matrix of two groups immunohistochemically. Two groups for chondrogenic differentiation of SMSCs successfully induced the expression of multiple cartilage-specific molecules, including collagen type II and aggrecan, and resulted in a chondrocyte-like phenotype. The Group 1's cartilage gene content was higher than that of the group used transforming growth factor. Conclusion: Two groups can induce SMSCs differentiation into chondrocytes. Using supernatants can induce better results.

Key words: Supernatants , Synovial mesenchymal stem cells (SMSCs) , Chondrocyte , Transforming growth factor beta-1, Cellular microenvironment, Tissue engineering