Yoneda Yuriko, Kato Hisaya, Maezawa Yoshiro, Yokote Koutaro, Nakanishi Mio
Graduate School of Medicine, Chiba University, Chiba 260-8670, Japan.
Biophys Physicobiol. 2024 Mar 22;21(Supplemental):e211015. doi: 10.2142/biophysico.bppb-v21.s015. eCollection 2024.
During embryogenesis, human hematopoietic stem cells (HSCs) first emerge in the aorta-gonad-mesonephros (AGM) region via transformation of specialized hemogenic endothelial (HE) cells into premature HSC precursors. This process is termed endothelial-to-hematopoietic transition (EHT), in which the HE cells undergo drastic functional and morphological changes from flat, anchorage-dependent endothelial cells to free-floating round hematopoietic cells. Despite its essential role in human HSC development, molecular mechanisms underlying the EHT are largely unknown. This is due to lack of methods to visualize the emergence of human HSC precursors in real time in contrast to mouse and other model organisms. In this study, by inducing HE from human pluripotent stem cells in feeder-free monolayer cultures, we achieved real-time observation of the human EHT . By continuous observation and single-cell tracking in the culture, it was possible to visualize a process that a single endothelial cell gives rise to a hematopoietic cell and subsequently form a hematopoietic-cell cluster. The EHT was also confirmed by a drastic HE-to-HSC switching in molecular marker expressions. Notably, HSC precursor emergence was not linked to asymmetric cell division, whereas the hematopoietic cell cluster was formed through proliferation and assembling of the floating cells after the EHT. These results reveal unappreciated dynamics in the human EHT, and we anticipate that our human EHT model will provide an opportunity to improve our understanding of the human HSC development.
在胚胎发生过程中，人类造血干细胞（HSCs）首先通过将特化的造血内皮（HE）细胞转化为早熟HSC前体而在主动脉-性腺-中肾（AGM）区域出现。这个过程被称为内皮-造血转化（EHT），其中HE细胞经历了从扁平的、依赖锚定的内皮细胞到自由漂浮的圆形造血细胞的剧烈功能和形态变化。尽管EHT在人类HSC发育中起着至关重要的作用，但其潜在的分子机制在很大程度上尚不清楚。这是因为与小鼠和其他模式生物相比，缺乏实时可视化人类HSC前体出现的方法。在这项研究中，通过在无饲养层单层培养中从人类多能干细胞诱导生成HE，我们实现了对人类EHT的实时观察。通过在培养物中的连续观察和单细胞追踪，可以可视化单个内皮细胞产生造血细胞并随后形成造血细胞簇的过程。EHT也通过分子标志物表达中从HE到HSC的剧烈转换得到证实。值得注意的是，HSC前体的出现与不对称细胞分裂无关，而造血细胞簇是通过EHT后漂浮细胞的增殖和聚集形成的。这些结果揭示了人类EHT中未被认识到的动态变化，我们预计我们的人类EHT模型将为增进我们对人类HSC发育的理解提供一个机会。
