mTORC1信号通路在毛囊生长期启动时特异促进毛囊干细胞增殖

mTORC1 signaling specifically promotes proliferation of hair follicle stem cells during the telogen-to-anagen transition

目的探讨哺乳动物西罗莫司靶蛋白复合物1(mTORC1)信号在毛囊生长期启动中发挥关键作用的窗口期,及其是否特异性促进毛囊干细胞的增殖.方法将36只新生ICR小鼠随机等分为对照组、RAPA-P19组和RAPA-P21组,RAPA-P19组小鼠于出生后第19~24天、RAPA-P21组第21~24天每天腹腔注射西罗莫司,剂量为5 mg·kg^-1·d^-1,对照组在第19~24天腹腔注射同等体积的溶剂.分别于第22、23、24天各处死4只小鼠,取背部皮肤组织,采用HE染色结合毛囊形态学观察评价小鼠毛囊于第24天是否进入生长期;采用免疫荧光共染色技术检测第22和23天时mTORC1下游标志分子pS6和细胞增殖标志物Ki67的表达及定位情况.结果HE染色表明,第24天时对照组毛囊已经呈现明显生长期形态,RAPA-P19组毛囊仍呈静止期形态,而RAPA-P21组毛囊却呈现明显生长期形态.免疫荧光染色结果表明,在第22和23天时,对照组毛囊干细胞pS6与Ki67均阳性,RAPA-P19组两者均阴性,RAPA-P21组pS6阴性、Ki67阳性.在第23天时,3组毛囊隆突部上端的表皮细胞和皮脂腺细胞Ki67均阳性.结论mTORC1信号通路在毛囊从静止期向生长期转变阶段特异性促进毛囊干细胞的增殖,但不影响毛囊其他细胞的增殖.

Objective To identify the time window during which the mammalian target of rapamycin complex 1(mTORC1)signaling pathway plays a key role in telogen-to-anagen transition of hair follicles,and to explore whether the pathway specifically promotes the proliferation of hair follicle stem cells(HFSCs).Methods Totally,36 newborn ICR mice were randomly and equally divided into 3 groups:RAPA-P19 group intraperitoneally injected with 5 mg·kg^-1·d^-1 sirolimus on days 19-24 after birth,RAPA-P21 group intraperitoneally injected with 5 mg·kg^-1·d^-1 sirolimus on days 21-24 after birth,and control group intraperitoneally injected with the same volume of solvent on days 19-24 after birth.Four mice were sacrificed in each group on days 22,23 and 24 separately.Skin tissues were resected from the back,and hematoxylin-eosin staining of the skin tissues were performed followed by observation of hair follicle morphology to evaluate whether murine hair follicles progressed into the anagen phase on day 24.Immunofluorescence costaining was conducted to determine the expression and localization of mTORC1 downstream molecular marker pS6 and cell proliferation marker Ki67 on days 22 and 23.Results On day 24,hematoxylin-eosin staining showed anagen hair follicles in the control group and RAPA-P21 group,but telogen hair follicles in the RAPA-P19 group.On days 22 and 23,immunofluorescence costaining revealed positive staining for both pS6 and Ki67 in HFSCs in the control group,negative staining for both pS6 and Ki67 in the RAPA-P19 group,negative staining for pS6 and positive staining for Ki67 in the RAPA-P21 group.On day 23,epidermal cells and sebaceous gland cells in the upper hair follicle bulge were stained positively for Ki67 in all the 3 groups.Conclusion mTORC1 signaling specifically promotes the proliferation of HFSCs during telogen-to-anagen transition,but not affects proliferation of other cells in hair follicles.