Nadin Brian M, Goodell Margaret A, Hirschi Karen K
Center for Cell and Gene Therapy, Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA.
Blood. 2003 Oct 1;102(7):2436-43. doi: 10.1182/blood-2003-01-0118. Epub 2003 Jun 12.
Adult murine bone marrow hematopoietic stem cells (HSCs) can be purified by sorting Hoechst 33342-extruding side population (SP) cells. Herein we investigated whether SP cells reside within embryonic tissues and exhibit hematopoietic progenitor activity. We isolated yolk sac (YS) and embryonic tissues 7.5 to 11.5 days after coitus (dpc), resolved an SP in each, and demonstrated that these SP cells exhibit distinct phenotypic and functional characteristics throughout development. YS and embryonic SP isolated 8.0 dpc expressed vascular endothelial-cadherin (VE-cadherin) and vascular endothelial receptor 2 (Flk-1), markers not expressed by bone marrow SP but expressed by endothelial cells and progenitors. SP at this stage did not express CD45 or produce hematopoietic colonies in vitro. In contrast, SP isolated 9.5 to 11.5 dpc contained a significantly higher proportion of cells expressing cKit and CD45, markers highly expressed by bone marrow SP. Furthermore, YS SP isolated 9.5 to 11.5 dpc demonstrated 40- to 90-fold enrichment for hematopoietic progenitor activity over unfractionated tissue. Our data indicate that YS and embryonic SP cells detected prior to the onset of circulation express the highest levels of endothelial markers and do not generate blood cells in vitro; however, as development progresses, they acquire hematopoietic potential and phenotypic characteristics similar to those of bone marrow SP.
成年小鼠骨髓造血干细胞（HSCs）可通过分选排出Hoechst 33342的侧群（SP）细胞来纯化。在此，我们研究了SP细胞是否存在于胚胎组织中并表现出造血祖细胞活性。我们在交配后7.5至11.5天（dpc）分离了卵黄囊（YS）和胚胎组织，在每个组织中解析出一个SP，并证明这些SP细胞在整个发育过程中表现出不同的表型和功能特征。在8.0 dpc分离的YS和胚胎SP表达血管内皮钙黏蛋白（VE-钙黏蛋白）和血管内皮受体2（Flk-1），这些标志物骨髓SP不表达，但内皮细胞和祖细胞表达。此阶段的SP不表达CD45，也不在体外产生造血集落。相比之下，在9.5至11.5 dpc分离的SP含有显著更高比例表达cKit和CD45的细胞，这两种标志物在骨髓SP中高度表达。此外，在9.5至11.5 dpc分离的YS SP显示，其造血祖细胞活性比未分级组织富集40至90倍。我们的数据表明，在循环开始前检测到的YS和胚胎SP细胞表达最高水平的内皮标志物，且不在体外产生血细胞；然而，随着发育的进行，它们获得了与骨髓SP相似的造血潜能和表型特征。
