Huang X, Cho S, Spangrude G J
Departments of Pathology and Medicine, University of Utah, Salt Lake City, UT 84132-2408, USA.
Cell Death Differ. 2007 Nov;14(11):1851-9. doi: 10.1038/sj.cdd.4402225. Epub 2007 Sep 7.
Adult stem cells hold great promise for future therapeutic applications. Hematopoietic stem cells (HSCs) are among the best-characterized adult stem cells. As such, these cells provide a conceptual framework for the study of adult stem cells from other organs. Here, we review the current knowledge of HSC generation during embryonic development and HSC maintenance in the bone marrow (BM) during adult life. Recent scientific progress has demonstrated that the development of HSCs involves many anatomical sites in the embryo, but the relative contribution of each of these sites to the adult HSC pool remains controversial. Specialized anatomical sites in the BM have been identified as stem cell niches, and these play essential roles in regulating the self-renewal and differentiation of HSCs through recently identified signaling pathways. Extracellular signaling from stem cell niches must integrate with the intracellular molecular machinery and/or genetic programs to regulate HSC fate choice. The exact cellular and/or molecular mechanisms defining stem cell niche and 'stemness' of HSC is largely unknown although substantial progress has been made recently. Hence, many questions remain to be answered even in this relatively well-defined model of stem cell biology.
成体干细胞在未来治疗应用方面极具前景。造血干细胞（HSCs）是特征最为明确的成体干细胞之一。因此，这些细胞为研究来自其他器官的成体干细胞提供了一个概念框架。在此，我们综述了胚胎发育过程中造血干细胞的生成以及成年期骨髓（BM）中造血干细胞维持的现有知识。最近的科学进展表明，造血干细胞的发育涉及胚胎中的许多解剖部位，但这些部位对成年造血干细胞库的相对贡献仍存在争议。骨髓中的特定解剖部位已被确定为干细胞微环境，它们通过最近发现的信号通路在调节造血干细胞的自我更新和分化中发挥着重要作用。来自干细胞微环境的细胞外信号必须与细胞内分子机制和/或遗传程序整合，以调节造血干细胞的命运选择。尽管最近取得了重大进展，但定义干细胞微环境和造血干细胞“干性”的确切细胞和/或分子机制在很大程度上仍然未知。因此，即使在这个相对明确的干细胞生物学模型中，仍有许多问题有待解答。
