Effects of asiaticoside on the expression of Smad protein by normal skin fibroblasts and hypertrophic scar fibroblasts

BACKGROUND: The precise mechanism of asiaticoside in molecular and gene expression levels of Smad protein and mRNA still remains unknown. We hypothesised that asiaticoside might inhibit the formation of hypertrophic scarring by affecting the expression of Smad protein and interfering with the Smad signalling pathway. AIMS: To investigate the effects of asiaticoside on the expression of Smad protein by hypertrophic scar fibroblasts (HSFs) and to clarify the mechanism of asiaticoside in scar treatment. METHODS: Normal skin fibroblasts and HSFs were exposed to various concentrations of asiaticoside in serum-free medium for 72 h, then immunocytochemistry was used to examine the localization and expression of phosphorylated Smad2 and Smad7. The expression of Smad protein was studied both at the transcriptional and post-transcriptional levels, using conventional reverse transcription PCR and Western blotting. RESULTS: Asiaticoside markedly enhanced the expression of inhibitory Smad7, but it had no effect on the expression of Smad2. Further study revealed that asiaticoside could induce Smad7 to enter the cytoplasm from the nucleus. CONCLUSIONS: Asiaticoside inhibits scarring probably by enhancing the expression of inhibitory Smad7, and is a potential treatment for scarring.