Effects of the inhibition of Smad3 phosphorylation on wound healing

Objectives: The surgical closure of a cleft palate is considered to impair maxillary growth and dento-alveolar development. Transforming growth factor (TGF)-β/Smad3 signaling is known to play an important role in wound healing. In our previous in vivo study, Smad3-deficient mice showed the accelerated re-epithelialization and tissue remodeling in the process of palatal wound repair with downregulation of TGF-β1, monocyte chemotactic protein (MCP)-1 and macrophage inflammatory protein (MIP)-1α compared with wild-type mice. In this study, to develop a new remedy for palatal wound, we investigated the effect of a Specific Inhibitor of Smad3 (SIS3) which blocks TGF-β1/Smad3 signaling through the inhibition of Smad3 phophorylation. Methods: The primary culture was performed for epithelial cells and fibroblasts from murine newborn mice-derived epidermis. The inhibition of Smad3 phosphorylation by SIS3 was verified with western blot analysis in fibroblasts. The effect of SIS3 on epithelial cell chemotaxis was assessed by in vitro migration assay. The SIS3 effect was also examined by three-dimensional collagen gel contraction assay, then α-smooth muscle actin (SMA) expression was examined. Moreover, SIS3 was applied onto the mouse palate after creating mucoperiosteal wound. Histological analysis and immunohistochemistry were also performed for TGF-β1, MIP-1α and MCP-1 expressions. Results: Smad3 phosphorylation was inhibited by SIS3 treatment in mice fibroblasts derived from newborn epidermis. The epithelial cells treated with SIS3 showed resistance to migration restraint by TGF-β1 stimulation. Fibroblasts augmented contraction rate of collagen gels in the presence of TGF-β1, whereas the lower ratio was observed in the case of SIS3 treatment and α-SMA expression was decreased simultaneously. Scar formation in palate was reduced in the mice treated with SIS3 followed by the inhibitory effect of inflammation as seen the reduced expressions of TGF-β1, MCP-1 and MIP-1α. Conclusion: It was suggested that SIS3 treatment may be available for controlling wound repair by inhibiting TGF-β1/Smad3 signaling.