The effects of Wnt inhibitors on the chondrogenesis of human mesenchymal stem cells.

The purpose of this study was to test the hypothesis that the inhibition of the Wnt pathway promotes chondrogenesis of human mesenchymal stem cells (hMSCs). To investigate its effect on early chondrogenesis, in vitro pellet cultures were prepared using MSCs at passage 3 at varying concentrations of 100, 200, and 300 ng/mL of either Dickkopf (DKK)-1 or secreted frizzled-related protein (sFRP)-1, and analyzed for chondrogenic gene and protein expressions after 3 and 6 days of culture. After that to study the effects on chondrogenesis at a longer term, 200 ng of sFRP-1 was challenged either in the presence or absence of transforming growth factor (TGF)-beta(3) to pellets of MSCs at passage 3 for 7 days. Then the pellets were cultured without sFRP-1 for 14 further days. For early chondrogenesis, both DKK-1 and sFRP-1 increased glycosaminoglycan synthesis as well as the gene and protein expressions of SOX-9 and type II collagen, more prominently by sFRP-1 than by DKK-1. However, after 21 days of in vitro chondrogenic culture under TGF-beta(3), sFRP-1 treatment did not further increase the gene expression of SOX-9 and type II collagen. The overall results of this study suggest that although the inhibitors of Wnt pathway promote early chondrogenesis of MSCs, they do not provide an ultimately enhancing role in the cartilage tissue engineering of MSCs.