Hematopoietic stem cell regulation by the Notch signaling-including hematopoietic stem cell induction from human embryonic stem cells-

Notch信号使造血干细胞（HSC）在体外扩增的同时保持其不成熟。然而，Notch信号是否在造血干细胞自我更新的骨髓生态位中起重要作用还有待确定。在这个项目中，我们的目标是通过使用缺乏Notch1和/或Notch2基因的小鼠或使用YO01027（一种Notch信号抑制剂）的野生型小鼠来解决这个问题。首先，我们比较了Notchl+/- notch2 +/-小鼠在给予5-FU后骨髓中恢复的Lin-Scal+cKit+ (LSK)细胞或CD34-LSK细胞的绝对数量，或野生型小鼠在给予5-FU后再给予YO01027。然而，与我们的预期相反，我们无法在两种实验中发现与对照小鼠的差异，因此，没有证据支持Notch信号在骨髓HSC维持中起生理作用的假设。从人类胚胎干细胞（ES）成功诱导造血干细胞使我们能够考虑这些造血干细胞的各种应用，例如临床使用导向的血细胞的工业化生产。在本项目中，基于我们之前发现Notch信号在胚胎发生过程中对HSC的产生起重要作用，我们研究了人类胚胎干细胞是否可以产生HSC。我们从人类胚胎干细胞系KhES-3诱导分化，并使用可能代表HSC的各种表面标记（如CD34、CD133、KDR、CD90、CD150、CD105、PCLP-1、PECAM1和VE-Cadherin）组合对胚胎干细胞来源的细胞进行分类。然而，那些被分类的细胞显示出分化为内皮细胞和巨噬细胞的潜力，但我们无法识别出具有显着造血活性的细胞。

Notch signaling enables the hematopoietic stem cells (HSC) to expand ex vivo while maintaining their immaturity. It is, however, to be determined whether the Notch signaling plays an important role in the bone marrow niche for the self HSC renewal. In this project, we aimed at approaching this question by using mice variably lacking Notch1 and/or Notch2 genes or wild-type mice administered with YO01027, a Notch signaling inhibitor. First, we compared the absolute number of recovering Lin-Scal+cKit+ (LSK) cells or CD34-LSK cells in the bone marrow of Notchl+/-Notch2+/- mice after administration with 5-FU, or wild-type mice administered with 5-FU followed by the YO01027 administration. Contrary to our expectation, however, we were unable to find the difference in either kind of experiment, compared with the control mice, and thus, no proof was obtained supporting the hypothesis that Notch signaling plays a physiological role in the HSC maintenance in the bone marrow.The successful induction of HSC from human embryonic stem (ES) cells allows us to consider various applications of those HSC, such as the industrialized production of clinical use-oriented blood cells. In this project, we investigated whether the HSC could be generated from human ES cells, based on our previous finding that Notch signaling plays an important role in HSC generation during embryogenesis. We induced differentiation from a human ES cell line, KhES-3, and sorted ES cell-derived cells using various combinations of surface markers that potentially represent HSC, such as CD34, CD133, KDR, CD90, CD150, CD105, PCLP-1, PECAM1, and VE-Cadherin. Those that were sorted as such, however, showed the potential to differentiate into endothelial cells and macrophages, but we were unable to identify the cells showing remarkable hematopoietic actiity.