Novel mechanisms of vasculogenesis

项目摘要 多种血管疾病，包括高血压、糖尿病、动脉粥样硬化等， 血管内皮功能障碍。但是，目前还没有有效的方法来纳入 新的内皮细胞进入体内受损的血管，这可能有助于血管再生和修复。 新血管的形成有两种不同的机制，血管发生，即分化， 新生血管内皮细胞和血管生成，通过从现有血管分支形成新血管 船舶.目前认为，血管发生在很大程度上限于初始血管网络， 胚胎发生，而大多数后期血管通过现有血管系统的血管生成形成。 虽然很难研究哺乳动物胚胎中的血管发生，但斑马鱼已经成为一种 有利的模型系统来研究血管发育。控制血管的分子机制 在包括斑马鱼和人类在内的所有脊椎动物中，发育是高度保守的。 在这里，我们发现了一个新的人口假定血管祖细胞在斑马鱼胚胎。 这些细胞显示ETS转录因子etv 2的高表达，etv 2是已知的血管发生的关键调节因子， 并且位于邻近原肾（原肾相关细胞，PAC）。我们的初步数据显示 PAC是器官特异性血管的主要来源，它们有助于胚胎血管的形成， 通过一种新的机制将细胞嵌入功能性血管。我们的数据进一步表明，PAC 很可能在哺乳动物胚胎中保存下来。此外，我们还鉴定了连接粘附分子， Jam 2b是PAC形成所需的关键调节剂之一。我们假设PAC是一组新的 多能血管祖细胞为血管生长提供重要贡献。 提出了以下具体目标：1）确定PAC对不同血型的贡献 2）确定PAC在血管发育中的功能作用; 3）确定Jam 2b和其他 上游调节因子在PAC形成和血管发育中的作用。血统追踪方法将是 用于确定PAC对斑马鱼胚胎中不同类型血管的贡献。PAC消融 和etv 2条件抑制策略将用于测试PAC在斑马鱼中的功能作用，以及它们的 还将在鼠胚胎中研究形成。jam 2b在PAC形成中的作用，其与 VEGF信号通路，以及其他PAC富集基因的功能作用将在斑马鱼中进行分析。 本提案中获得的数据将回答关于下列方面的特性和职能作用的关键问题： PACs，并可能揭示一种新的血管生长机制。血管发生的机制 是高度保守的，我们的初步数据表明，类似的祖细胞也存在于 哺乳动物胚胎了解PAC如何形成并融入现有 脉管系统可能导致修复受损血管用于治疗目的的新方向。

Project Summary Multiple vascular diseases including hypertension, diabetes, atherosclerosis, and others are associated with the dysfunction of vascular endothelium. However, there are currently no effective methods to incorporate new endothelial cells into damaged vessels in vivo which could contribute to vascular regeneration and repair. New blood vessels form by two distinct mechanisms, vasculogenesis, which is differentiation of vascular endothelial cells de novo, and angiogenesis, formation of new vessels by branching from the existing vessels. It is currently thought that vasculogenesis is largely limited to the initial vascular network during embryogenesis, while the majority of the later vessels form by angiogenesis from the existing vasculature. While it is difficult to study vasculogenesis in the mammalian embryos, zebrafish has emerged as an advantageous model system to study vascular development. Molecular mechanisms that control vascular development are highly conserved between all vertebrates including zebrafish and humans. Here we have discovered a novel population of putative vascular progenitors in the zebrafish embryos. These cells show high expression of ETS transcription factor etv2, a known key regulator of vasculogenesis, and are located adjacent to the pronephros (pronephros-associated cells, PACs). Our preliminary data indicate that PACs are the major source of organ specific vasculature, and they contribute to the embryonic vasculature by a novel mechanism of cell intercalation into functional blood vessels. Our data further suggest that PACs are likely conserved in mammalian embryos. In addition, we have identified Junctional Adhesion Molecule Jam2b as one of key regulators required for PAC formation. We hypothesize that PACs are a novel group of multipotent vascular progenitors which provide important contribution for vascular growth. The following specific aims are proposed: 1) Define contribution of PACs to different types of blood vessels; 2) Identify functional role for PACs in vascular development; 3) Identify the role of Jam2b and other upstream regulators in the formation of PACs and vascular development. Lineage tracing approaches will be employed to determine contribution of PACs to different types of vessels in zebrafish embryos. PAC ablation and etv2 conditional inhibition strategies will be used to test the functional role of PACs in zebrafish, and their formation will also be investigated in murine embryos. The role of jam2b in PAC formation, its interaction with Vegf signaling pathway, and functional roles of other PAC-enriched genes will be analyzed in zebrafish. Data obtained in this proposal will answer the key questions regarding the identity and functional role of PACs, and are likely to uncover a novel mechanism of vascular growth. The mechanisms of vasculogenesis are highly conserved, and our preliminary data suggest that similar progenitors are also present in the mammalian embryos. Understanding the mechanism of how PACs form and incorporate into existing vasculature may lead to a new direction to repair damaged vessels for therapeutic purposes.