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)-1, 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-1, 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.