Supplementary Material for: Melanogenesis markers expression in premature graying of hair- a cross-sectional study

Background: Studies on mice and aging human hair follicles provide compelling evidence that graying of hair results from premature differentiation of Melanocyte stem cells (MeSC) in the niche/bulge. Objective: To analyze whether differentiation of melanocyte stem cells is responsible for premature graying of hair (PGH). Methods: Twenty- five patients of PGH (n=25) attending dermatology department were recruited. Five unpigmented and five pigmented hairs were obtained per patient by separating individual follicles by 1 mm punch biopsies. The hairs were dissected at a distance of 2 mm from the bulb to separate the stem cells (upper segment) (US) from the melanocytes (lower segment) (LS). RNA was extracted from hair follicle segments US and LS, and expression of GP100, Tyrosinase (TYR) and Tyrosinase related protein-1 (TYRP1) genes was quantified using Qiagen one-step RT-PCR kit. Results: We found melanogenesis gene expression in both temporary (US) and permanent (LS) segments of unpigmented and pigmented hair follicles. When compared between the US and LS of white hair, the expression of TYR and GP100 was much higher in US than LS, suggestive of melanogenesis in the bulge. Similarly, when compared between white and black US, the expression of all three genes was higher in white US than black US, although not statistically significant. Limitations: Low samples size and lack of data pertaining to the expression of genes at protein level are the limitations of current study. Conclusion: Even though this pilot study data yielded key information about the expression of GP100, TYR and TYRP-1 at mRNA level, further studies quantifying the expression of these genes at protein level are needed to provide additional clues to further address the results in detail.

背景：针对小鼠及衰老人类毛囊的研究已获得确凿证据，表明头发变白源于微环境/隆突区（niche/bulge）内黑素细胞干细胞（Melanocyte stem cells, MeSC）的过早分化。
研究目的：分析黑素细胞干细胞的分化是否为头发过早变白（premature graying of hair, PGH）的致病诱因。
研究方法：招募25名就诊于皮肤科的头发过早变白（premature graying of hair, PGH）患者（n=25）。每位患者通过1mm穿刺活检分离单个毛囊，获取5根无色素毛发与5根有色素毛发。于距毛球2mm处切断毛发，将干细胞区段（上段，upper segment, US）与黑素细胞区段（下段，lower segment, LS）分离。从毛囊上段与下段提取RNA，使用Qiagen一步法逆转录聚合酶链反应（RT-PCR）试剂盒定量检测GP100、酪氨酸酶（Tyrosinase, TYR）及酪氨酸酶相关蛋白-1（Tyrosinase related protein-1, TYRP1）基因的表达水平。
研究结果：本研究在无色素与有色素毛囊的暂时性区段（上段，US）及永久性区段（下段，LS）中均检测到黑素生成相关基因的表达。对比白发毛囊的上段与下段时，酪氨酸酶（TYR）与GP100的表达在上段显著高于下段，提示隆突区存在黑素生成活动。类似地，对比白发与黑发的上段时，白发上段的三类基因表达均高于黑发上段，但差异无统计学意义。
研究局限性：样本量较小，且缺乏相关基因的蛋白水平表达数据，为本研究的局限性。
研究结论：尽管本预试验研究在mRNA水平获取了GP100、TYR及TYRP-1基因表达的关键信息，但仍需开展进一步研究以定量检测这些基因的蛋白水平表达，从而为深入阐释本研究结果提供更多依据。