Uchida N, Aguila H L, Fleming W H, Jerabek L, Weissman I L
Department of Pathology, Stanford University School of Medicine, CA 94305.
Blood. 1994 Jun 15;83(12):3758-79.
Hematopoietic stem cells (HSCs) are believed to play a critical role in the sustained repopulation of all blood cells after bone marrow transplantation (BMT). However, understanding the role of HSCs versus other hematopoietic cells in the quantitative reconstitution of various blood cell types has awaited methods to isolate HSCs. A candidate population of mouse HSCs, Thy-1.1lo Lin-Sca-1+ cells, was isolated several years ago and, recently, this population has been shown to be the only population of BM cells that contains HSCs in C57BL/Ka-Thy-1.1 mice. As few as 100 of these cells can radioprotect 95% to 100% of irradiated mice, resulting long-term multilineage reconstitution. In this study, we examined the reconstitution potential of irradiated mice transplanted with purified Thy-1.1lo Lin-Sca-1+ BM cells. Donor-derived peripheral blood (PB) white blood cells were detected as early as day 9 or 10 when 100 to 1,000 Thy-1.1lo Lin-Sca-1+ cells were used, with minor dose-dependent differences. The reappearance of platelets by day 14 and thereafter was also seen at all HSC doses (100 to 1,000 cells), with a slight dose-dependence. All studied HSC doses also allowed RBC levels to recover, although at the 100 cell dose a delay in hematocrit recovery was observed at day 14. When irradiated mice were transplanted with 500 Thy-1.1lo Lin-Sca-1+ cells compared with 1 x 10(6) BM cells (the equivalent amount of cells that contain 500 Thy-1.1lo Lin-Sca-1+ cells as well as progenitor and mature cells), very little difference in the kinetics of recovery of PB, white blood cells, platelets, and hematocrit was observed. Surprisingly, even when 200 Thy1.1lo Lin-Sca-1+ cells were mixed with 4 x 10(5) Sca-1- BM cells in a competitive repopulation assay, most of the early (days 11 and 14) PB myeloid cells were derived from the HSC genotype, indicating the superiority of the Thy-1.1lo Lin-Sca-1+ cells over Sca-1- cells even in the early phases of myeloid reconstitution. Within the Thy-1.1lo Lin-Sca-1+ population, the Rhodamine 123 (Rh123)hi subset dominates in PB myeloid reconstitution at 10 to 14 days, only to be overtaken by the Rh123lo subset at 3 weeks and thereafter. These findings indicate that HSCs can account for the early phase of hematopoietic recovery, as well as sustained hematopoiesis, and raise questions about the role of non-HSC BM populations in the setting of BMT.
造血干细胞（HSCs）被认为在骨髓移植（BMT）后所有血细胞的持续重建中起着关键作用。然而，要了解HSCs与其他造血细胞在各种血细胞类型定量重建中的作用，还需等待分离HSCs的方法。几年前分离出了小鼠HSCs的一个候选群体，即Thy-1.1lo Lin-Sca-1+细胞，最近已证明该群体是C57BL/Ka-Thy-1.1小鼠中唯一含有HSCs的骨髓细胞群体。仅100个这样的细胞就能对95%至100%的受辐照小鼠起到辐射防护作用，实现长期多谱系重建。在本研究中，我们检测了用纯化的Thy-1.1lo Lin-Sca-1+骨髓细胞移植的受辐照小鼠的重建潜力。当使用100至1000个Thy-1.1lo Lin-Sca-1+细胞时，早在第9天或第10天就能检测到供体来源的外周血（PB）白细胞，且存在轻微的剂量依赖性差异。在所有HSC剂量（100至1000个细胞）下，第14天及之后血小板也会重新出现，且有轻微的剂量依赖性。所有研究的HSC剂量也能使红细胞水平恢复，不过在100个细胞剂量时，第14天观察到血细胞比容恢复延迟。与1×10(6)个骨髓细胞（相当于含有500个Thy-1.1lo Lin-Sca-1+细胞以及祖细胞和成熟细胞的等量细胞）相比，当用500个Thy-1.1lo Lin-Sca-1+细胞移植受辐照小鼠时，在PB、白细胞、血小板和血细胞比容恢复动力学方面观察到的差异非常小。令人惊讶的是，即使在竞争性重建试验中将200个Thy1.1lo Lin-Sca-1+细胞与4×10(5)个Sca-1-骨髓细胞混合，大多数早期（第11天和第14天）PB髓系细胞也源自HSC基因型，这表明即使在髓系重建的早期阶段，Thy-1.1lo Lin-Sca-1+细胞也优于Sca-1-细胞。在Thy-1.1lo Lin-Sca-1+群体中，罗丹明123（Rh123）高表达亚群在第10至14天主导PB髓系重建，但在3周及之后被Rh123低表达亚群取代。这些发现表明，HSCs可解释造血恢复的早期阶段以及持续造血，并引发了关于非HSC骨髓群体在BMT情况下作用的问题。
