It is well established that haematopoietic stem and progenitor cells (HSPCs) are generated from a transient subset of specialized endothelial cells termed haemogenic, present in the yolk sac, placenta and aorta, through an endothelial-to-haematopoietic transition (EHT). HSPC generation via EHT is thought to be restricted to the early stages of development. By using experimental embryology and genetic approaches in birds and mice, respectively, we document here the discovery of a bone marrow haemogenic endothelium in the late fetus/young adult. These cells are capable of de novo producing a cohort of HSPCs in situ that harbour a very specific molecular signature close to that of aortic endothelial cells undergoing EHT or their immediate progenies, i.e., recently emerged HSPCs. Taken together, our results reveal that HSPCs can be generated de novo past embryonic stages. Understanding the molecular events controlling this production will be critical for devising innovative therapies.

中文翻译：

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从骨髓来源的造血内皮体内产生造血干/祖细胞。

众所周知，造血干细胞和祖细胞 (HSPC) 是通过内皮到造血转化 (EHT) 由存在于卵黄囊、胎盘和主动脉中的称为造血的特化内皮细胞的瞬时亚群产生的。通过 EHT 生成 HSPC 被认为仅限于开发的早期阶段。通过分别在鸟类和小鼠中使用实验胚胎学和遗传方法，我们在此记录了在晚期胎儿/年轻成人中发现的骨髓造血内皮。这些细胞能够原位从头产生一组HSPC，这些HSPC具有非常特殊的分子特征，接近于经历EHT的主动脉内皮细胞或其直接后代，即最近出现的HSPC。综合起来，我们的结果表明，HSPCs 可以在胚胎阶段之后从头产生。了解控制这种生产的分子事件对于设计创新疗法至关重要。