Nat Med：揭秘压力过大致早生华发的机制

多情应笑我，早生华发。

日前，一项研究显示：压力过大的确会令人早生华发。但不要妄想着到海边晒晒太阳放松一下就能挽救，因为过多紫外线同样会令头发变白。

美国宾夕法尼亚大学等机构的研究人员在老鼠试验中发现，当老鼠皮肤受到紫外线照射而受损时，它们毛囊中的黑色素干细胞会“迁徙”至皮肤。黑色素干细胞能产生黑色素，它是皮肤和头发颜色的来源，能保护皮肤少受阳光侵害。

研究人员表示，黑色素干细胞“转移”至皮肤是为帮助皮肤弥补紫外线照射造成的损伤。研究人员同时发现，压力激素水平高的老鼠，从毛囊向皮肤“转移”的黑色素干细胞数量更多。

研究人员指出，人们认为压力会催生白发，研究显示，压力的确会让毛囊中的黑色素干细胞“跑”到皮肤里；压力越大，“迁徙”的黑色素干细胞数量越多。这项研究结果或许揭示了压力激素和头发变白的关系，这也就解释了为何压力大的人皮肤色素沉着会更多，也解释了为何极端情况下，有人会“一夜白头”。

人在接受阳光照射时，皮肤会产生更多的黑色素。这项研究显示，人接受紫外线照射时，皮肤变黑也许不单是新生黑色素的作用，很可能有毛囊内的黑色素干细胞在起作用。也就是说，皮肤会“偷走”藏在毛囊里的黑色素干细胞。令人沮丧的是，这些头发中的黑色素干细胞消失后，不会有新的干细胞来替代。

大部分人25岁开始出现第一根白发，遗传、酒精、吸烟以及生活环境等都对头发变白产生一定影响。研究人员希望，这项结果可以帮助他们研制出针对压力引发白发的药物。

上述研究结果发表在了近期出版的《自然-医学》杂志上。

Fgf9 from dermal γδ T cells induces hair follicle neogenesis after wounding
Abstract
Understanding molecular mechanisms for regeneration of hair follicles provides new opportunities for developing treatments for hair loss and other skin disorders. Here we show that fibroblast growth factor 9 (Fgf9), initially secreted by γδ T cells, modulates hair follicle regeneration after wounding the skin of adult mice. Reducing Fgf9 expression decreases this wound-induced hair neogenesis (WIHN). Conversely, overexpression of Fgf9 results in a two- to threefold increase in the number of neogenic hair follicles. We found that Fgf9 from γδ T cells triggers Wnt expression and subsequent Wnt activation in wound fibroblasts. Through a unique feedback mechanism, activated fibroblasts then express Fgf9, thus amplifying Wnt activity throughout the wound dermis during a crucial phase of skin regeneration. Notably, humans lack a robust population of resident dermal γδ T cells, potentially explaining their inability to regenerate hair after wounding. These findings highlight the essential relationship between the immune system and tissue regeneration. The importance of Fgf9 in hair follicle regeneration suggests that it could be used therapeutically in humans.