ENDOTHELIAL CELL ROLE IN YOLK SAC STEM CELL DEVELOPMENT

我们的长期研究目标是了解胚胎血管中控制细胞增殖和分化的机制。在胚胎发育过程中，造血细胞和内皮细胞需要共同的生长因子才能形成，并且可能共享共同的前体--血管母细胞。据报道，小鼠血细胞在体外直接来源于卵黄囊内皮细胞，然而，还没有进行体内血细胞来源于内皮细胞的试验。我们已经鉴定出一个内脏卵黄囊细胞群，在移植到有条件的新生小鼠后具有HSC活性，我们在初步研究中确定这个细胞群由造血细胞和内皮细胞组成。我们将使用我们独特的新生小鼠移植模型来验证胚胎卵黄囊内形成的内皮细胞在体内产生HSC的假设，促进HSC移植到血液学受损的宿主中，并增强HSC的体外扩增。我们的具体目标是：1.确定内皮细胞在体内产生HSC的潜力。我们将使用逆转录病毒标记策略和试剂来分离同质内皮细胞群，以确定内皮细胞和血细胞的克隆关系。2.检测卵黄囊内皮细胞移植到去髓宿主体内后促进HSC植入的能力。来自造血缺陷小鼠的供体内皮细胞将被注射不同浓度的HSC并测量其再生活性。3.确定内皮细胞和/或内皮细胞有丝分裂原是否单独或与特定的造血生长因子联合刺激内脏卵黄囊来源的HSC体外扩增。这些实验结果将为胚胎发育中的造血和内皮细胞发育提供新的见解，阐明内皮-HSC相互作用在HSC移植中的作用，并为调节HSC的增殖行为提供新的途径。

Our long term research goals are to understand the mechanisms controlling cellular proliferation and differentiation in embryonic blood forming vessels. During embryogenesis, hematopoietic and endothelial cells require common growth factors for formation and may share a common precursor, the hemangioblast. Murine blood cells reportedly arise directly from yolk sac endothelial cells in vitro, however, no in vivo tests of blood cell derivation from endothelium have been performed. We have identified a visceral yolk sac cell population that possesses HSC activity upon transplantation into conditioned newborn mice and we have determined in preliminary studies that this population is comprised of both hematopoietic and endothelial cells. We will use our unique newborn mouse transplantation model to test the hypothesis that endothelial cells formed within the embryonic yolk sac give rise to HSC in vivo, facilitate HSC engraftment upon transplantation into hematologically compromised hosts, and augment HSC expansion ex vivo. Our specific aims are: 1. To determine the potential of endothelial cells to give rise to HSC in vivo. We will use a retroviral marking strategy and reagents that provide isolation of a homogenous population of endothelial cells to determine the clonal relationship of endothelium and blood cells. 2. To determine the capacity of yolk sac endothelial cells to facilitate HSC engraftment upon transplantation into myeloablated hosts. Donor endothelial cells from hematopoietic deficient mice will be injected in varying concentrations with the HSC and repopulating activity measured. 3. To determine if endothelial cells and/or endothelial mitogens alone or in combination with selected hematopoietic growth factors stimulate visceral yolk sac-derived HSC expansion ex vivo. The results of these experiments will provide novel insight into hematopoietic and endothelial cell development during embryogenesis, clarify the role of endothelial-HSC interactions during HSC transplantation, and provide new approaches to modulate HSC proliferative behavior.