Osteogenic protein-1 with transforming growth factor-β1: potent inducer of chondrogenesis of synovial mesenchymal stem cells in vitro

Abstract

BackgroundRecently, cells derived from synovial mesenchymal stem cells (MSCs) have been regarded as a potential source of cells to induce repair of articular cartilage. To investigate more effective methods for promoting chondrogenesis, we examined the effects of osteogenic protein (OP)-1 with or without transforming growth factor-β (TGFβ1) on chondrogenesis of human MSCs in vitro. MethodsMSCs were isolated from the synovial membrane of patients with rheumatoid arthritis undergoing knee replacement surgery. After expansion of the cells, pellet cultures were performed in chondrogenic medium with OP-1 100–200 ng/ml, TGFβ1 10 ng/ml, or both agents for 3 or 6 weeks. Chondro-genesis was evaluated histologically with safranin O staining, reverse transcription polymerase chain reaction for aggrecan and type II collagen mRNA, and quantification of glycosaminoglycan (GAG) content using a dimethylmethylene blue dye-binding assay. GAG content was normalized by DNA content measured using Hoechst 33258 dye. ResultsAt 3 weeks of culture, mRNAs for type II collagen and aggrecan were expressed by MSCs treated with either TGFβ1 or OP-1; however, substantial matrix production was not induced. At 6 weeks, OP-1 increased GAG accumulation dose-dependently in the presence or absence of TGFβ1, and the GAG content was the highest after combined treatment with 200 ng OP-1 and TGFβ1. Histological staining for safranin O was poor after treatment with OP-1 or TGFβ1 alone and slightly increased after combined treatment with TGFβ1 and OP-1 at 3 weeks. At 6 weeks, OP-1 increased the intensity of staining dose-dependently in the presence or absence of TGFβ1. However, the histological appearance of the cells treated with OP-1 alone was similar to that of hypertrophic chondrocytes, which was different from that of cells with combined treatment with OP-1 and TGFβ1. ConclusionsA high dose of OP-1 was useful for enhancing chondrogenesis from synovium-derived MSCs in combined treatment with TGFβ1.