Mechanical load modulates chondrogenesis of human mesenchymal stem cells through the TGF‐β pathway

Abstract

This study investigated the effect of mechanical load on human mesenchymal stem cell (hMSC) differentiation under different exogenous transforming growth factor-beta1 (TGF-beta(1)) concentrations (0, 1 or 10 ng/ml).The role of the TGF-beta signalling pathway in this process was also studied. Human MSCs were seeded into fibrin-biodegradable polyurethane scaffolds at a cell density of 5 x 10(6) cells per scaffold and stimulated using our bioreactor. One hour of surface motion superimposed on cyclic compression was applied once a day over seven consecutive days. Scaffolds were analysed for gene expression, DNA content and glycosaminoglycan amount. Addition of TGF-beta(1) in the culture medium was sufficient to induce chondrogenesis of hMSCs. Depending on the TGF-beta(1) concentration of the culture medium, mechanical load stimulated chondrogenesis of hMSCs compared to the unloaded scaffolds, with a much stronger effect on gene expression at lower TGF-beta(1) concentrations. With TGF-beta(1) absent in the culture medium, mechanical load stimulated gene transcripts and protein synthesis of TGF-beta(1) and TGF-beta(3). TGF-beta type I receptor inhibitor LY364947 blocked the up-regulation on TGF-beta(1) and TGF-beta(3) production stimulated by mechanical load, and also blocked the chondrogenesis of hMSCs. Taken together, these findings suggest that mechanical load promotes chondrogenesis of hMSCs through TGF-beta pathway by up-regulating TGF-beta gene expression and protein synthesis.