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控制机制。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才能形成，并且可能具有共同的前体，即成血管细胞。据报道，小鼠血细胞在体外直接由卵黄囊内皮细胞产生，然而，尚未进行内皮细胞衍生血细胞的体内试验。我们已经确定了一种内脏卵黄囊细胞群，在移植到条件成熟的新生小鼠体内时具有HSC活性，我们已经在初步研究中确定，这种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，在移植到血液学受损的宿主后促进HSC的植入，并增强HSC在体外的扩增。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，提供内皮细胞同质群体的分离，以确定内皮细胞和血细胞的克隆关系。2. 目的探讨卵黄囊内皮细胞对造血干细胞移植的促进作用。将来自造血缺陷小鼠的供体内皮细胞注射不同浓度的造血干细胞，并测量其再生活性。3. 确定内皮细胞和/或内皮丝裂原单独或与选定的造血生长因子联合是否刺激内脏卵黄囊源性HSC体外扩增。这些实验的结果将为胚胎发生过程中造血和内皮细胞的发育提供新的见解，阐明内皮-HSC在HSC移植过程中的相互作用，并提供调节HSC增殖行为的新方法。

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.