Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, California 92093-0380, USA.
Nature. 2010 Mar 4;464(7285):108-11. doi: 10.1038/nature08738. Epub 2010 Feb 14.
A major goal of regenerative medicine is to instruct formation of multipotent, tissue-specific stem cells from induced pluripotent stem cells (iPSCs) for cell replacement therapies. Generation of haematopoietic stem cells (HSCs) from iPSCs or embryonic stem cells (ESCs) is not currently possible, however, necessitating a better understanding of how HSCs normally arise during embryonic development. We previously showed that haematopoiesis occurs through four distinct waves during zebrafish development, with HSCs arising in the final wave in close association with the dorsal aorta. Recent reports have suggested that murine HSCs derive from haemogenic endothelial cells (ECs) lining the aortic floor. Additional in vitro studies have similarly indicated that the haematopoietic progeny of ESCs arise through intermediates with endothelial potential. Here we have used the unique strengths of the zebrafish embryo to image directly the generation of HSCs from the ventral wall of the dorsal aorta. Using combinations of fluorescent reporter transgenes, confocal time-lapse microscopy and flow cytometry, we have identified and isolated the stepwise intermediates as aortic haemogenic endothelium transitions to nascent HSCs. Finally, using a permanent lineage tracing strategy, we demonstrate that the HSCs generated from haemogenic endothelium are the lineal founders of the adult haematopoietic system.
再生医学的一个主要目标是从诱导多能干细胞（iPSCs）指导形成多能、组织特异性干细胞，用于细胞替代疗法。然而，目前还不可能从 iPS 细胞或胚胎干细胞（ESCs）中生成造血干细胞（HSCs），因此需要更好地了解 HSCs 在胚胎发育过程中是如何正常出现的。我们之前曾表明，在斑马鱼发育过程中，造血发生通过四个不同的波，HSCs 出现在最后一个波中，与背主动脉密切相关。最近的报道表明，鼠类 HSCs 源自排列在主动脉底部的造血内皮细胞（ECs）。其他体外研究同样表明，ESCs 的造血祖细胞是通过具有内皮潜能的中间产物产生的。在这里，我们利用斑马鱼胚胎的独特优势，直接从背主动脉的腹侧壁成像 HSCs 的生成。我们使用荧光报告基因转染体的组合、共聚焦延时显微镜和流式细胞术，鉴定并分离了逐步的中间产物，因为主动脉造血内皮细胞向新生 HSCs 转化。最后，我们使用永久性谱系追踪策略证明，从造血内皮细胞生成的 HSCs 是成年造血系统的直系祖细胞。
