Marrow Hematopoietic Stem Cells Revisited: They Exist in a Continuum and are Not Defined by Standard Purification Approaches; Then There are the Microvesicles.
Marrow Hematopoietic Stem Cells Revisited: They Exist in a Continuum and are Not Defined by Standard Purification Approaches; Then There are the Microvesicles.
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DOI：
10.3389/fonc.2014.00056
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发表时间：
2014
影响因子：
4.7
通讯作者：
Dooner M
中科院分区：
文献类型：
--
作者：
Quesenberry PJ;Goldberg L;Aliotta J;Dooner M
造血的当前概念包含在分层干细胞模型中。这最初是从对脾脏集落形成单位和不同细胞谱系的体外祖细胞的研究发展起来的，但后来演变成具有不同体内分化和增殖潜力的细胞的综合模型。这些细胞的特点和纯化主要基于各种谱系特异性和干细胞特异性表面表位的表达。将单克隆抗体与这些表位结合，然后用于物理和荧光分离这些细胞的不同类别。最原始的骨髓干细胞的金标准是在致死辐射小鼠中的长期多谱系再增殖和更新。逐步的工作似乎已经克隆地定义了谱系阴性（Lin-）、Sca-1+、c-kit+、CD 150+干细胞，其具有巨大的增殖、分化和更新潜力。该细胞稳定，处于细胞周期的G 0期。然而，我们实验室的持续工作表明，小鼠骨髓干细胞的植入、分化、归巢和基因表达表型随着细胞周期的推移而持续可逆地变化。最近，使用周期定义的超活性染料和荧光激活细胞分选和S期特异性氚化胸苷自杀，我们已经建立了长期的再生造血干细胞是一个快速增殖，因此不断变化的细胞，作为一个必然的结果，它不能被纯化或定义的克隆单细胞的基础上。使用注射和摄入的5-溴脱氧尿苷（BrdU）进行的进一步体内研究表明，G 0 Lin-Sca-1，c-kit+ Flt 3 −细胞快速通过细胞周期。这些数据通过考虑分离过程来解释：通过选择性分离去除增殖的干细胞，留下非代表性的休眠的G 0干细胞。换句话说，他们把真实的干细胞和纯化的干细胞一起扔掉了。该系统中，骨髓干细胞连续和可逆地改变专性细胞周期的过渡，进一步复杂的组织微泡对细胞表型的影响的考虑。已经发现组织微泡可以改变骨髓细胞的表型，这可能解释了“干细胞可塑性”的观察结果。这些短期的改变是由于原始细胞mRNA的转移和尚未确定的转录因子。长期表型变化是由于转录调节;一种稳定的表观遗传变化。因此，干细胞系统的特征在于连续的周期和微泡相关的变化。未来的挑战是定义干细胞群体。
Current concepts of hematopoiesis are encompassed in a hierarchical stem cell model. This developed initially from studies of colony-forming unit spleen and in vitro progenitors for different cell lineages, but then evolved into a comprehensive model of cells with different in vivo differentiative and proliferative potential. These cells were characterized and purified based largely on expression of a variety of lineage-specific and stem cell-specific surface epitopes. Monoclonal antibodies were bound to these epitopes and then used to physically and fluorescently separate different classes of these cells. The gold standard for the most primitive marrow stem cells was long-term multilineage repopulation and renewal in lethally irradiated mice. Progressive work seemed to have clonally defined a Lineage negative (Lin−), Sca-1+, c-kit+, CD150+ stem cell with great proliferative, differentiative, and renewal potential. This cell was stable and in the G0 phase of cell cycle. However, continued work in our laboratory indicated that the engraftment, differentiation, homing, and gene expression phenotype of the murine marrow stem cells continuously and reversibly changes with passage through cell cycle. Most recently, using cycle-defining supravital dyes and fluorescent-activated cell sorting and S-phase-specific tritiated thymidine suicide, we have established that the long-term repopulating hematopoietic stem cell is a rapidly proliferating, and thus a continually changing cell; as a corollary it cannot be purified or defined on a clonal single cell basis. Further in vivo studies employing injected and ingested 5-Bromodeoxyuridine (BrdU), showed that the G0 Lin-Sca-1, c-kit+ Flt3− cell was rapidly passing through cell cycle. These data are explained by considering the separative process: the proliferating stem cells are eliminated through the selective separations leaving non-representative dormant G0 stem cells. In other words, they throw out the real stem cells with the purification. This system, where the marrow stem cell continuously and reversibly changes with obligate cell cycle transit, is further complicated by the consideration of the impact of tissue microvesicles on the cell phenotypes. Tissue microvesicles have been found to alter the phenotype of marrow cells, possibly explaining the observations of “stem cell plasticity.” These alterations, short-term, are due to transfer of originator cell mRNA and as yet undefined transcription factors. Long-term phenotype change is due to transcriptional modulation; a stable epigenetic change. Thus, the stem cell system is characterized by continuous cycle and microvesicle-related change. The challenge of the future is to define the stem cell population.