Challen Grant A, Little Melissa H
Institute for Molecular Bioscience, Queensland Bioscience Precinct, 306 Carmody Road, The University of Queensland, St. Lucia, Brisbane, QLD, 4072, Australia.
Stem Cells. 2006 Jan;24(1):3-12. doi: 10.1634/stemcells.2005-0116.
A defining property of murine hematopoietic stem cells (HSCs) is low fluorescence after staining with Hoechst 33342 and Rhodamine 123. These dyes have proven to be remarkably powerful tools in the purification and characterization of HSCs when used alone or in combination with antibodies directed against stem cell epitopes. Hoechst low cells are described as side population (SP) cells by virtue of their typical profiles in Hoechst red versus Hoechst blue bivariate fluorescent-activated cell sorting dot plots. Recently, excitement has been generated by the findings that putative stem cells from solid tissues may also possess this SP phenotype. SP cells have now been isolated from a wide variety of mammalian tissues based on this same dye efflux phenomenon, and in many cases this cell population has been shown to contain apparently multipotent stem cells. What is yet to be clearly addressed is whether cell fusion accounts for this perceived SP multipotency. Indeed, if low fluorescence after Hoechst staining is a phenotype shared by hematopoietic and organ-specific stem cells, do all resident tissue SP cells have bone marrow origins or might the SP phenotype be a property common to all stem cells? Subject to further analysis, the SP phenotype may prove invaluable for the initial isolation of resident tissue stem cells in the absence of definitive cell-surface markers and may have broad-ranging applications in stem cell biology, from the purification of novel stem cell populations to the development of autologous stem cell therapies.
小鼠造血干细胞（HSCs）的一个决定性特性是在用Hoechst 33342和罗丹明123染色后荧光较低。这些染料已被证明是单独使用或与针对干细胞表位的抗体联合使用时，在HSCs纯化和表征方面非常强大的工具。Hoechst低荧光细胞因其在Hoechst红色与Hoechst蓝色双变量荧光激活细胞分选点图中的典型轮廓而被描述为侧群（SP）细胞。最近，来自实体组织的假定干细胞也可能具有这种SP表型的发现引起了人们的关注。基于相同的染料外排现象，现在已经从多种哺乳动物组织中分离出了SP细胞，并且在许多情况下，已证明该细胞群含有明显的多能干细胞。尚未明确解决的问题是细胞融合是否解释了这种感知到的SP多能性。实际上，如果Hoechst染色后低荧光是造血干细胞和器官特异性干细胞共有的表型，那么所有驻留组织SP细胞都来自骨髓吗？或者SP表型可能是所有干细胞共有的特性？经过进一步分析，SP表型可能被证明在缺乏明确的细胞表面标志物的情况下，对于驻留组织干细胞的初始分离非常有价值，并且可能在干细胞生物学中具有广泛的应用，从新型干细胞群体的纯化到自体干细胞治疗的开发。
