Supplementary Material for: Topical Treatment with Basic Fibroblast Growth Factor Promotes Wound Healing and Barrier Recovery Induced by Skin Abrasion

It has been reported that basic fibroblast growth factor (bFGF) promotes the healing of skin ulceration by inducing fibroblast proliferation, yet the role of bFGF on epidermal barrier function, especially from the perspective of scratch-induced skin abrasion, remains unknown. To this end, we initially developed an epidermal abrasion mouse model induced by scratching with a stainless-steel wire brush, and examined the effects of bFGF on the wound healing induced by skin abrasion. This procedure induced a significant elevation of transepidermal water loss (TEWL) in a scratch-count-dependent manner. This elevated TEWL was significantly decreased following topical application of bFGF to the skin. In addition, bFGF increased the expression of Ki67 in keratinocytes following mechanical scratching. These results suggest that bFGF enhances keratinocyte proliferation, which, in turn, repairs the skin barrier disruption and wounds caused by scratching in mice. Consistently, bFGF stimulated proliferation of normal human epidermal keratinocytes (NHEK). Intriguingly, the effect of bFGF and other growth factors on NHEK proliferation was additive. However, high cell density diminished the effect of bFGF on NHEK proliferation. This particular result can be explained by our observation that FGF receptor mRNA expression in NHEK was low under conditions of high cell density. Our findings suggest that bFGF stimulates keratinocyte proliferation, especially in a lower cell density environment, to repair skin wound in accord with skin barrier recovery.

已有研究表明，碱性成纤维细胞生长因子（basic fibroblast growth factor, bFGF）可通过诱导成纤维细胞增殖促进皮肤溃疡愈合，但bFGF对皮肤屏障功能的调控作用，尤其是在刮擦诱导的皮肤擦伤这一场景下，仍未明确。为此，我们首先构建了采用不锈钢丝刷刮擦诱导的表皮擦伤小鼠模型，并探究了bFGF对皮肤擦伤所致创面愈合的影响。该造模方式可呈刮擦次数依赖性显著升高经皮水分流失（transepidermal water loss, TEWL）水平；而于皮肤局部外用bFGF后，升高的TEWL水平可被显著降低。此外，机械刮擦刺激后，bFGF可上调角质形成细胞中Ki67的表达。上述结果提示，bFGF可增强角质形成细胞增殖，进而修复小鼠因刮擦导致的皮肤屏障破坏与创面损伤。与之相符的是，bFGF可刺激正常人表皮角质形成细胞（normal human epidermal keratinocytes, NHEK）增殖。有趣的是，bFGF与其他生长因子对NHEK增殖的促进作用具有叠加效应；然而，高细胞密度会削弱bFGF对NHEK增殖的调控效果。这一现象可通过本研究的观测结果得到解释：高细胞密度条件下，NHEK内的成纤维细胞生长因子受体（FGF receptor）mRNA表达水平较低。本研究结果表明，bFGF可在低细胞密度环境下特异性刺激角质形成细胞增殖，从而促进皮肤创面修复并同步恢复皮肤屏障功能。