Zouboulis Christos C, Adjaye James, Akamatsu Hirohiko, Moe-Behrens Gerd, Niemann Catherin
Department of Dermatology, Venereology, Allergology and Immunology, Dessau Medical Center, Dessau, Germany.
Exp Gerontol. 2008 Nov;43(11):986-97. doi: 10.1016/j.exger.2008.09.001. Epub 2008 Sep 9.
In healthy individuals, skin integrity is maintained by epidermal stem cells which self-renew and generate daughter cells that undergo terminal differentiation. Despite accumulation of senescence markers in aged skin, epidermal stem cells are maintained at normal levels throughout life. Therefore, skin ageing is induced by impaired stem cell mobilisation or reduced number of stem cells able to respond to proliferative signals. In the skin, existence of several distinct stem cell populations has been reported. Genetic labelling studies detected multipotent stem cells of the hair follicle bulge to support regeneration of hair follicles but not been responsible for maintaining interfollicular epidermis, which exhibits a distinct stem cell population. Hair follicle epithelial stem cells have at least a dual function: hair follicle remodelling in daily life and epidermal regeneration whenever skin integrity is severely compromised, e.g. after burns. Bulge cells, the first adult stem cells of the hair follicle been identified, are capable of forming hair follicles, interfollicular epidermis and sebaceous glands. In addition, -- at least in murine hair follicles -- they can also give rise to non-epithelial cells, indicating a lineage-independent pluripotent character. Multipotent cells (skin-derived precursor cells) are present in human dermis; dermal stem cells represent 0.3% among human dermal foreskin fibroblasts. A resident pool of progenitor cells exists within the sebaceous gland, which is able to differentiate into both sebocytes and interfollicular epidermis. The self-renewal and multi-lineage differentiation of skin stem cells make these cells attractive for ageing process studies but also for regenerative medicine, tissue repair, gene therapy and cell-based therapy with autologous adult stem cells not only in dermatology. In addition, they provide in vitro models to study epidermal lineage selection and its role in the ageing process.
在健康个体中，表皮干细胞维持皮肤的完整性，这些干细胞自我更新并产生经历终末分化的子代细胞。尽管衰老皮肤中存在衰老标志物的积累，但表皮干细胞在整个生命过程中都维持在正常水平。因此，皮肤老化是由干细胞动员受损或能够响应增殖信号的干细胞数量减少引起的。在皮肤中，已经报道了几种不同的干细胞群体的存在。基因标记研究检测到毛囊隆突部的多能干细胞可支持毛囊再生，但不负责维持毛囊间表皮，毛囊间表皮表现出独特的干细胞群体。毛囊上皮干细胞至少具有双重功能：在日常生活中进行毛囊重塑，以及在皮肤完整性严重受损时（例如烧伤后）进行表皮再生。隆突细胞是最早被鉴定出的毛囊成体干细胞，能够形成毛囊、毛囊间表皮和皮脂腺。此外，至少在小鼠毛囊中，它们还可以产生非上皮细胞，这表明其具有不依赖谱系的多能特性。多能细胞（皮肤衍生前体细胞）存在于人类真皮中；真皮干细胞在人类包皮成纤维细胞中占0.3%。皮脂腺内存在一群祖细胞，它们能够分化为皮脂腺细胞和毛囊间表皮。皮肤干细胞的自我更新和多谱系分化不仅在皮肤病学领域，而且在衰老过程研究、再生医学、组织修复、基因治疗和基于自体成体干细胞的值为疗法中，都使这些细胞具有吸引力。此外，它们还提供了体外模型来研究表皮谱系选择及其在衰老过程中的作用。
