了解在胚胎发生过程中促进造血干细胞(HSC)规范的调节机制对于体外生成HSC很重要。巨核细胞从卵黄囊出现并产生血小板,参与多种生物过程,比如防止出血。然而,巨核细胞是否调节胚胎主动脉-性腺-中肾(AGM)区域的HSC发育尚不清楚.这里,我们使用血小板因子4(PF4)-Cre;Rosa-tdTomato细胞报告HSC发育小生境中巨核细胞的存在。Further,我们使用PF4-Cre;Rosa-DTA(DTA)耗竭模型来揭示巨核细胞控制小鼠胚胎中的HSC规格。巨核细胞缺乏阻断前HSC的生成和成熟并改变AGM处的HSC活性。此外,巨核细胞在OP9-DL1共培养系统中促进内皮到造血的转变。单细胞RNA测序将细胞表面标记CD226阳性的巨核细胞鉴定为通过分泌TNFSF14促进内皮细胞血源性命运的最高潜力亚群。在一条线上,TNFSF14治疗在巨核细胞耗尽的共培养物中拯救造血细胞功能。一起来看,巨核细胞促进前造血干细胞的产生和成熟,在胚胎造血过程中充当关键的微环境控制因子。
Understanding the regulatory mechanisms facilitating hematopoietic stem cell (HSC) specification during embryogenesis is important for the generation of HSCs in vitro. Megakaryocyte emerged from the yolk sac and produce platelets, which are involved in multiple biological processes, such as preventing hemorrhage. However, whether megakaryocytes regulate HSC development in the embryonic aorta-gonad-
mesonephros (AGM) region is unclear. Here, we use platelet factor 4 (PF4)-Cre;Rosa-tdTomato+ cells to report presence of megakaryocytes in the HSC developmental niche. Further, we use the PF4-Cre;Rosa-DTA (DTA) depletion model to reveal that megakaryocytes control HSC specification in the mouse embryos. Megakaryocyte deficiency blocks the generation and maturation of pre-HSCs and alters HSC activity at the AGM. Furthermore, megakaryocytes promote endothelial-to-hematopoietic transition in a OP9-DL1 coculture system. Single-cell RNA-sequencing identifies megakaryocytes positive for the cell surface marker CD226 as the subpopulation with highest potential in promoting the hemogenic fate of endothelial cells by secreting TNFSF14. In line, TNFSF14 treatment rescues hematopoietic cell function in megakaryocyte-depleted cocultures. Taken together, megakaryocytes promote production and maturation of pre-HSCs, acting as a critical microenvironmental control factor during embryonic hematopoiesis.