Wnt-5a is involved in TGF-beta3-stimulated chondrogenic differentiation of chick wing bud mesenchymal cells.

In this study we investigated whether signalling by TGF-beta3 and Wnt-5a cross-talk during chondrogenic differentiation of chick wing mesenchyme. Using differential display polymerase chain reaction screening, we found the expression of Wnt-5a to be significantly increased during transforming growth factor-beta3 (TGF-beta3)-induced precartilage condensation in mesenchyme micromass cultures. Transfection of cells with a Wnt-5a expression construct promoted precartilage condensation and chondrogenesis in micromass cultures, similar to that observed when chondrogenic-competent cells were exposed to TGF-beta3. Overexpression of Wnt-5a or treatment with TGF-beta3 stimulated the activation of protein kinase C-alpha (PKC-alpha) and p38 mitogen-activated protein kinase (MAPK), both positive regulators of chondrogenic differentiation. Inactivation of PKC-alpha and p38 MAPK by specific inhibitors abrogated chondrogenesis stimulated by both TGF-beta3 and Wnt-5a. Similarly, partial reduction in TGF-beta3-induced Wnt-5a expression by small interfering RNA resulted in decreased activities of PKC-alpha and p38 MAPK, and abolished the chondro-stimulatory effect of TGF-beta3. Collectively, these findings indicate that Wnt-5a, a non-canonical Wnt, can mediate the chondro-stimulatory effect of TGF-beta3 through upregulation of PKC-alpha and p38MAPK signaling.