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细胞增殖和分化的调控机制。 在胚胎发生过程中，造血细胞和内皮细胞需要共同的生长因子来形成，并且可以共享共同的前体成血管细胞。 据报道，鼠血细胞在体外直接来源于卵黄囊内皮细胞，然而，尚未进行血细胞来源于内皮细胞的体内试验。 我们已经确定了一个内脏卵黄囊细胞群，具有HSC活性移植到条件新生小鼠后，我们已经确定，在初步研究中，这个人口是由造血和内皮细胞。 我们将使用我们独特的新生小鼠移植模型来测试胚胎卵黄囊内形成的内皮细胞在体内产生HSC，在移植到血液学受损的宿主后促进HSC植入，并增强HSC体外扩增的假设。 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，提供内皮细胞的同质群体的分离，以确定内皮细胞和血细胞的克隆关系。 2. 确定卵黄囊内皮细胞在移植入骨髓清除宿主后促进HSC植入的能力。 将来自造血缺陷小鼠的供体内皮细胞以不同浓度与HSC一起注射，并测量再增殖活性。 3.确定内皮细胞和/或内皮有丝分裂原单独或与选定的造血生长因子组合是否刺激内脏卵黄囊来源的HSC离体扩增。这些实验的结果将提供新的见解造血和内皮细胞发育在胚胎发育过程中，澄清的作用，内皮细胞-HSC相互作用在HSC移植，并提供新的方法来调节HSC增殖行为。

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.