Basic fibroblast growth factor stimulates human keratinocyte motility by Rac activation

Topical application of human recombinant basic fibroblast growth factor (bFGF) promotes wound healing. bFGF, however, has been reported to have little in vitro effects on keratinocyte compared with other cell types such as endothelial cells or fibroblasts. The aim of this study was to investigate the mechanism(s) of bFGF-stimulated keratinocyte migration. Normal human keratinocytes, seeded on coverslips that were noncoated or coated with type I collagen or fibronectin, were stimulated with bFGF to evaluate their ability to spread. Keratinocyte migration was measured using a Boyden chamber assay. The lysates of keratinocytes, which were plated on noncoated, type I collagen-coated or fibronectin-coated plastic dishes and stimulated with bFGF, were subjected to pulldown assays to detect guanine triphosphate-loaded Rac. Morphologically, keratinocytes formed lamellipodia only when they were stimulated with bFGF on the collagen-coated coverslips. Keratinocyte migration was significantly enhanced by bFGF. Guanine triphosphate-loaded Rac was detected only in the lysate of bFGF-stimulated keratinocytes on collagen-coated dishes. This in vitro study shows that bFGF exerts a stimulatory effect on keratinocyte migration in the presence of type I collagen as a scaffold, and, at least, Rac activation is involved.