Co‑culture of fibroblast‑like synoviocytes with umbilical cord‑mesenchymal stem cells inhibits expression of pro‑inflammatory proteins, induces apoptosis and promotes chondrogenesis.

The present study aimed to investigate the effect of co‑culture of fibroblast‑like synoviocytes (FLS) with human umbilical cord‑mesenchymal stem cells (UC‑MSCs) on rheumatoid arthritis (RA) and to understand the mechanisms that mediate the induced changes. FLS and UC‑MSCs were isolated and cultured individually, FLS were then cultured with or without UC‑MSCs. The phenotype of UC‑MSCs was analyzed prior to co‑culture. The UC‑MSCs were successfully isolated and expanded, and exhibited a fibroblast‑like morphology. Enzyme‑linked immunosorbent assay (ELISA) and reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) were performed to determine the expression levels of interleukin (IL)‑1β, IL‑6, and chemokine (C‑C motif) ligand (CCL)‑2. The cell apoptosis rate was determined by flow cytometry. Furthermore, the RNAs of aggrecan and collagen type II were isolated and assessed in a chondrogenesis assay following co‑culture for 7, 14, 21 and 28 days. Protein expression levels of apoptosis‑related proteins, including B‑cell lymphoma (Bcl‑2), Bcl‑2‑associated X protein, p53 and phospho (p)‑AKT, and growth differentiation factor‑5 were analyzed by western blotting. ELISA and qRT‑PCR demonstrated that compared with FLS cultured alone, co‑culture with UC‑MSCs significantly downregulates the expression levels of IL‑1β, IL‑6 and CCL‑2. Additionally, the percentage of apoptotic cells was significantly increased in the co‑cultured cells (P<0.05), and the relative RNAs levels of aggrecan and collagen type II were increased compared with FLS alone. Furthermore, the expression levels of Bcl‑2 (P<0.05) and p‑AKT (P<0.05) were significantly decreased, whereas, p53 (P=0.001), Bax (P<0.01) and GDF‑5 (P<0.01) were increased by co‑culture of FLS with UC‑MSCs compared with FLS alone. In conclusion, co‑culture of FLS with UC‑MSCs may be important and clinically useful for the treatment of RA by inhibiting the expression of pro‑inflammatory mediators, inducing apoptosis and promoting chondrogenesis.