Schneider T E, Barland C, Alex A M, Mancianti M L, Lu Y, Cleaver J E, Lawrence H J, Ghadially R
Department of Dermatology, University of California, San Francisco, CA 94143, USA.
Proc Natl Acad Sci U S A. 2003 Sep 30;100(20):11412-7. doi: 10.1073/pnas.2034935100. Epub 2003 Sep 17.
Epidermal stem cells play a central role in tissue homeostasis, wound repair, tumor initiation, and gene therapy. A major impediment to the purification and molecular characterization of epidermal stem cells is the lack of a quantitative assay for cells capable of long-term repopulation in vivo, such as exists for hematopoietic cells. The tremendous strides made in the characterization and purification of hematopoietic stem cells have been critically dependent on the availability of competitive transplantation assays, because these assays permit the accurate quantitation of long-term repopulating cells in vivo. We have developed an analogous functional assay for epidermal stem cells, and have measured the frequency of functional epidermal stem cells in interfollicular epidermis. These studies indicate that cells capable of long-term reconstitution of a squamous epithelium reside in the interfollicular epidermis. We find that the frequency of these long-term repopulating cells is 1 in 35,000 total epidermal cells, or in the order of 1 in 104 basal epidermal cells, similar to that of hematopoietic stem cells in the bone marrow, and much lower than previously estimated in epidermis. Furthermore, these studies establish a novel functional assay that can be used to validate immunophenotypic markers and enrichment strategies for epidermal stem cells, and to quantify epidermal stem cells in various keratinocyte populations. Thus further studies using this type of assay for epidermis should aid in the progress of cutaneous stem cell-targeted gene therapy, and in more basic studies of epidermal stem cell regulation and differentiation.
表皮干细胞在组织稳态、伤口修复、肿瘤发生和基因治疗中发挥着核心作用。表皮干细胞纯化和分子特征鉴定的一个主要障碍是缺乏一种针对能够在体内长期重新填充的细胞的定量检测方法，而造血细胞则有这样的检测方法。造血干细胞鉴定和纯化方面取得的巨大进展严重依赖于竞争性移植检测方法的可用性，因为这些检测方法能够在体内准确量化长期重新填充细胞。我们已经开发了一种针对表皮干细胞的类似功能检测方法，并测量了毛囊间表皮中功能性表皮干细胞的频率。这些研究表明，能够长期重建鳞状上皮的细胞存在于毛囊间表皮中。我们发现，这些长期重新填充细胞的频率为每35000个表皮细胞中有1个，或约每10000个基底表皮细胞中有1个，这与骨髓中的造血干细胞频率相似，且远低于先前在表皮中的估计值。此外，这些研究建立了一种新型功能检测方法，可用于验证表皮干细胞的免疫表型标记和富集策略，并量化各种角质形成细胞群体中的表皮干细胞。因此，使用这种表皮检测方法的进一步研究应有助于皮肤干细胞靶向基因治疗的进展，以及表皮干细胞调节和分化的更基础研究。
