人类毛囊(HF)的生长和毛干的形成需要高度增殖的基质角质形成细胞的终末分化相关的细胞周期停滞。然而,这一复杂事件的调节仍然未知.CIP/KIP家族成员蛋白(p21CIP1,p27KIP1和p57KIP2)调节细胞周期进程/阻滞,内复制,分化和凋亡。由于它们尚未在人类HF中得到充分表征,我们询问CIP/KIP蛋白是否以及在何处定位于人发基质和前皮质中与细胞周期活性和HF特异性上皮细胞分化的关系,该分化以角蛋白85(K85)蛋白表达为标志。K85表达与细胞周期活性标志物的丢失或减少同时发生。包括原位DNA合成(EdU掺入),Ki-67,磷酸组蛋白H3和细胞周期蛋白A和B1,确认皮质HF前角质形成细胞的有丝分裂后状态。在增殖性毛发基质中发现了大量的CIP/KIP蛋白的表达,伴随着在细胞周期检查点控制中的作用。p21CIP1,p27KIP1和细胞周期蛋白E持续存在于前皮质的有丝分裂后角质形成细胞中,而p57KIP2蛋白减少但变成了细胞核。这些数据暗示CIP/KIP蛋白在维持增殖停滞中的支持作用,分化和抗凋亡途径,在生长期VI中促进持续的毛球生长和毛干形成。此外,有丝分裂后的毛发基质区域含有细胞核扩大的细胞,和DNA原位杂交显示细胞在前皮质中>2N。这表明CIP/KIP蛋白可能会抵消细胞周期蛋白E,以控制具有四倍体倾向的细胞群体中DNA的进一步复制。这些数据为人类毛发基质角质形成细胞在其活跃细胞周期路径上的原位传记提供了新的启示,逮捕和终端分化,并展示人类HF作为一个优秀的,临床相关模型系统,用于人类上皮细胞在其自然组织生境内的细胞周期生理学研究。
Human hair follicle (HF) growth and hair shaft formation require terminal differentiation-associated cell cycle arrest of highly proliferative matrix keratinocytes. However, the regulation of this complex event remains unknown. CIP/KIP family member proteins (p21CIP1, p27KIP1 and p57KIP2) regulate cell cycle progression/arrest, endoreplication, differentiation and apoptosis. Since they have not yet been adequately characterized in the human HF, we asked whether and where CIP/KIP proteins localise in the human hair matrix and pre-cortex in relation to cell cycle activity and HF-specific epithelial cell differentiation that is marked by keratin 85 (K85) protein expression. K85 expression coincided with loss or reduction in cell cycle activity markers, including in situ DNA synthesis (EdU incorporation), Ki-67, phospho-histone H3 and cyclins A and B1, affirming a post-mitotic state of pre-cortical HF keratinocytes. Expression of CIP/KIP proteins was found abundantly within the proliferative hair matrix, concomitant with a role in cell cycle checkpoint control. p21CIP1, p27KIP1 and cyclin E persisted within post-mitotic keratinocytes of the pre-cortex, whereas p57KIP2 protein decreased but became nuclear. These data imply a supportive role for CIP/KIP proteins in maintaining proliferative arrest, differentiation and anti-apoptotic pathways, promoting continuous hair bulb growth and hair shaft formation in anagen VI. Moreover, post-mitotic hair matrix regions contained cells with enlarged nuclei, and DNA in situ hybridisation showed cells that were >2N in the pre-cortex. This suggests that CIP/KIP proteins might counterbalance cyclin E to control further rounds of DNA replication in a cell population that has a propensity to become tetraploid. These data shed new light on the in situ-biography of human hair matrix keratinocytes on their path of active cell cycling, arrest and terminal differentiation, and showcase the human HF as an excellent, clinically relevant model system for cell cycle physiology research of human epithelial cells within their natural tissue habitat.