Department of Dermatology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
Department of Stem Cell and Regenerative Biology, Harvard University and Harvard Stem Cell Institute, Cambridge, MA, USA.
Exp Dermatol. 2021 Apr;30(4):578-587. doi: 10.1111/exd.14309. Epub 2021 Mar 3.
Hair greying depends on the altered presence and functionality of hair follicle melanocytes. Melanocyte stem cells (MelSCs) reside in the bulge of hair follicles and give rise to migrating and differentiating progeny during the anagen phase. Ageing, genotoxic stress, redox stress and multiple behaviour-associated acute stressors have been seen to induce hair greying by depleting the MelSC pool, a phenomenon which is accompanied by ectopic pigmentation of these cells, followed by their depletion from the stem cell niche. This aberrant differentiation produces a state from which a return to stem cell-like quiescence appears to be lost. The cellular features of stress-induced hair greying have been extensively studied in murine models. Here, we describe a method to assess and quantify human hair follicle MelSC differentiation by measuring ectopically pigmented MelSCs in isolated human hair follicles exposed to specific stress signal mediators. Ionizing radiation, hydrogen peroxide and noradrenaline have been shown to cause hair greying in mice. We demonstrate here that isolated, ex vivo cultured human hair follicles exposed to these treatments display similar ectopic pigmentation within the bulge area which is accompanied by induction of differentiated melanocytic markers. This study suggests that as in murine models, stress signalling induces closely matching phenotypic changes in human hair follicles which can be monitored and studied as a surrogate model for early steps in human hair greying.
头发变白取决于毛囊黑素细胞的存在和功能改变。黑素细胞干细胞（MelSCs）存在于毛囊的隆起处，在生长期会产生迁移和分化的后代。衰老、遗传毒性应激、氧化应激和多种与行为相关的急性应激源已被发现通过耗尽 MelSC 池来诱导头发变白，这一现象伴随着这些细胞的异位色素沉着，随后它们从干细胞龛中耗尽。这种异常分化产生了一种状态，似乎失去了恢复到干细胞样静止状态的能力。在小鼠模型中，已经对应激诱导的头发变白的细胞特征进行了广泛研究。在这里，我们描述了一种通过测量暴露于特定应激信号介质的分离人毛囊中的异位色素化 MelSCs 来评估和量化人毛囊 MelSC 分化的方法。电离辐射、过氧化氢和去甲肾上腺素已被证明可导致小鼠头发变白。我们在这里证明，暴露于这些处理的分离的、离体培养的人毛囊在隆起区域显示出类似的异位色素沉着，同时伴随着分化的黑色素细胞标记物的诱导。这项研究表明，与在小鼠模型中一样，应激信号在人类毛囊中诱导出相似的表型变化，可以作为人类头发变白早期步骤的替代模型进行监测和研究。
