Liver Regeneration as a Model for Angiogenesis

描述(由申请人提供)：血管生成是指新血管从现有血管中萌发出来的过程，需要排列在血管系统内的特殊驻留细胞--内皮细胞(ECs)--对特定信号做出反应，在空间和时间上进行增殖、迁移和分化。另一方面，血管生成只是最近才出现在成人组织中的一种血管生长的替代机制，是骨髓来源的循环内皮细胞前体(ECP)归巢并植入新生血管区域的结果。众所周知，这两个事件都发生在生长、损伤和修复的不同条件下的肝血管内，但每个事件的程度和进行机制完全不清楚。这项建议的总体目标是确定在肝脏中诱导血管生成与血管生成血管生长的特定生长因子信号事件，并确定随后诱导肝特异性肝窦内皮细胞(SEC)开窗形态的EPC募集和/或分化的微环境。两种与临床相关的肝修复范例使我们能够在空间和时间上详细描述生长因子信号事件，并评估大鼠的正弦状超微结构和肝脏特异性SEC功能。目的I：70%肝部分切除(PHX)后肝窦表面生长因子和微环境的相互作用将被检测，因为最初有广泛的肝细胞增殖而无EC增殖，直到PHX后96小时，导致无血管肝灶。随后SEC的增殖和渗透到这些无血管实质簇中，并重建正常的肝脏结构，为评估生理性血管生成提供了一个良好的模型。目的II：采用同种异体肝移植模型同时检测血管生成和血管生成事件(双交叉品系和雌性到雄性移植，非GFP到GFP大鼠)，以确定SEC(宿主与移植物)的来源，并确定受体和供体在SEC植入和/或增殖中的参与程度。在移植前，肝脏在冷、缺血条件下保存18小时，移植后(热再灌流)，大部分SEC立即从肝窦表面脱落。值得注意的是，在24小时内，SEC衬里几乎完全重新填充了至少部分ECP，但在接下来的几天里发生了微血管重构、形态和功能修改。对这两个系统的比较分析将阐明相似和不同的生长因子信号机制以及控制这些事件的微环境的作用，并可能导致反映基于损伤的肝脏新生血管的特定要求的治疗方案的优化。

DESCRIPTION (provided by applicant): Angiogenesis is the process whereby new blood vessels sprout from existing vessels and requires that the specialized resident cells lining the vasculature, the endothelial cells (ECs), proliferate, migrate and differentiate spatially and temporally in response to specific signals. Vasculogenesis, on the other hand, has only recently emerged as an alternative mechanism of blood vessel growth in adult tissues and is the result of homing and engraftment of circulating EC precursors (ECPs) of bone marrow origin to areas of neovascularization. Both events are known to occur within the liver vasculature under very different conditions of growth, injury and repair, but the extent of each and the mechanisms by which they proceed in each case is completely unknown. The overall goal of this proposal is to determine the specific growth factor signaling events that induce angiogenic versus vasculogenic blood vessel growth in the context of liver and determine the subsequent microenvironmental milieu that induces EPC recruitment and/or differentiation of the liver-specific sinusoidal endothelial cell (SEC) fenestrated morphotype. Two paradigms of clinically-relevant liver repair allow us to spatially and temporally detail the growth factor signaling events and evaluate sinusoidal ultrastructure and liver-specific SEC function in the rat. AIM I: Growth factor and microenvironmental interactions will be examined at the sinusoidal surface following 70% partial hepatectomy (PHx) since there is initially extensive hepatocyte proliferation in the absence of EC proliferation until 96 hr post-PHx, resulting in avascular hepatic foci. Subsequent proliferation and infiltration of the SEC into these avascular parenchymal clusters and reestablishment of the normal hepatic architecture provides a well-timed model for evaluating physiological angiogenesis. AIM II: Angiogenic and vasculogenic events will be examined concurrently using an allogeneic liver transplant model (dual cross strain and female to male transplants, non-GFP to GFP rats) to ascertain the source of SEC (host vs. graft) and determine extent of recipient and donor involvement in SEC engraftment and/or proliferation. Prior to transplantation, livers are stored under cold, ischemic conditions for 18 h, and upon transplantation (warm reperfusion), a majority of the SEC slough off immediately from the sinusoidal surface. Remarkably, within 24 hr, the SEC lining has nearly completely repopulated at least partially from ECPs, but microvascular remodeling, morphological and functional modification occurs over subsequent days. Comparative analysis of these two systems will elucidate both similar and dissimilar growth factor signaling mechanisms and the role of the microenvironment that control these events and potentially lead to optimization of therapies that will reflect the specific requirements for injury based liver neovascularization.