Up-regulation of fibroblast growth factor (FGF) 9 expression and FGF-WNT/β-catenin signaling in laser-induced wound healing

Fibroblast growth factor (FGF) 9 is secreted by both mesothelial and epithelial cells, and plays important roles in organ development and wound healing via WNT/β-catenin signaling. The aim of this study was to evaluate FGF9 expression and FGF-WNT/β-catenin signaling during wound healing of the skin. We investigated FGF9 expression and FGF-WNT/β-catenin signaling after laser ablation of mouse skin and adult human skin, as well as in cultured normal human epidermal keratinocytes (NHEKs) upon stimulation with recombinant human (rh) FGF9 and rh-transforming growth factor (TGF)-β1. Our results showed that laser ablation of both mouse skin and human skin leads to marked overexpression of FGF9 and FGF9 mRNA. Control NHEKs constitutively expressed FGF9, WNT7b, WNT2, and β-catenin, but did not show Snail or FGF receptor (FGFR) 2 expression. We also found that FGFR2 was significantly induced in NHEKs by rhFGF9 stimulation, and observed that FGFR2 expression was slightly up-regulated on particular days during the wound healing process after ablative laser therapy. Both WNT7b and WNT2 showed up-regulated protein expression during the laser-induced wound healing process in mouse skin; moreover, we discerned that the stimulatory effect of rhFGF9 and rhTGF-β1 activates WNT/β-catenin signaling via WNT7b in cultured NHEKs. Our data indicated that rhFGF9 and/or rhTGF-β1 up-regulate FGFR2, WNT7b, and β-catenin, but not FGF9 and Snail; pretreatment with rh dickkopf-1 significantly inhibited the up-regulation of FGFR2, WNT7b, and β-catenin. Our results suggested that FGF9 and FGF-WNT/β-catenin signaling may play important roles in ablative laser-induced wound healing processes.