DEVELOPING VISION--THE MECHANISM OF TISSUE REMODELING

了解发育程序性毛细血管消退的机制是我们的长期目标。 作为一个模型系统，我们使用瞳孔膜（PM），一个短暂的毛细血管网络位于眼前房。 其优点在于，可通过经角膜注射进行操作，当从眼睛解剖时易于在整体封片中进行检查，并且在出生后消退。 我们先前已经表明，（1）巨噬细胞是毛细血管消退所必需的，（2）巨噬细胞诱导内皮细胞和周细胞的程序性细胞死亡以驱动毛细血管消退，以及（3）内皮细胞和周细胞死亡是细胞周期G1期接收到的巨噬细胞信号的结果。 在本申请中，我们将追求巨噬细胞如何介导毛细血管消退的广泛问题，目的如下。目的8：确定周细胞是否在调节PM消退中起作用。 周细胞被认为可能通过营养支持在维持毛细血管中起作用。 因此，我们将测试巨噬细胞诱导的周细胞死亡是否是PM回归的一个独特和必要的步骤。 目的9：确定巨噬细胞是否影响细胞周期独立的诱导凋亡。 巨噬细胞是内皮细胞有丝分裂原和细胞周期抑制剂的来源。 这增加了它们可能调节内皮细胞周期而不依赖于它们诱导细胞死亡的作用的可能性。 目的10：确定巨噬细胞诱导的细胞周期依赖性程序性细胞死亡是否需要TGF β信号转导。TGF β可以对内皮细胞具有促凋亡活性，并且是公认的细胞周期调节剂。 我们已经表明，有活跃的TGF β在沐浴PM的水，并将确定，使用多种策略，这是否是PCD或调节细胞周期所需的。 目的11：确定巨噬细胞诱导的PCD是否依赖于基质蛋白酶的作用。 细胞周期状态依赖性细胞死亡表明，在细胞周期的限制点的基本信号的抑制可能是原因。 我们将研究巨噬细胞产生的基质蛋白酶可能通过降解必需的基质配体引起PCD的可能性。很少有系统可以详细研究毛细管回归的机制。 通过我们开发的方法和本提案中概述的策略，我们有很好的机会了解这一临床重要过程。我们对发育程序性毛细血管退化的了解很有可能适用于支持肿瘤生长的毛细血管或某些血管疾病的核心特征。

It is our long-term goal to understand the mechanism of developmentally programmed capillary regression. As a model system we use the pupillary membrane (PM), a transient capillary network situated in the anterior chamber of the eye. It has the advantage that it is accessible to manipulation through trans- corneal injection, is easily examined in whole-mount when dissected from the eye and regresses postnatally. We have previously shown, (1) that macrophages are required for capillary regression, (2) that macrophages induce programmed cell death in endothelial cells and pericytes to drive capillary regression, and (3) that endothelial cells and pericytes die as a consequence of a macrophage signal received in G1-phase of cell cycle. In the current application, we will pursue the broad question of how macrophages mediate capillary regression with the following aims. Aim 8: To determine whether pericytes have a role in regulating PM regression. Pericytes are thought to have a role in maintaining capillaries, perhaps through trophic support. Thus, we will test whether macrophage-induced pericyte death is a distinct and essential step in PM regression. Aim 9: To determine whether macrophages influence cell-cycling independent of the induction of apoptosis. Macrophages are a source of endothelial cell mitogens and suppressors of cell-cycle. This raises the possibility that they may regulate endothelial cell- cycle independent of their role in inducing cell death. Aim 10: To determine whether TGFbeta signaling is required for macrophage-induced cell-cycle dependent programmed cell death. TGFbeta can have a pro-apoptotic activity on endothelial cells and is a recognized regulator of cell-cycle. We have shown that there is active TGFbeta in the aqueous that bathes the PM and will determine, using a multiple strategies, whether this is required for PCD or regulation of cell-cycle. Aim 11: To determine whether macrophage-induced PCD is dependent upon the action of matrix proteases. A cell-cycle state dependent cell death suggests that inhibition of essential signaling at the restriction point of cell-cycle may be the cause. We will investigate the possibility that matrix proteases produced by macrophages may cause PCD by degrading essential matrix ligands. There are few systems where the mechanism of capillary regression can be studied in detail. With the methods we have developed and the strategies outlined in this proposal, we have an excellent opportunity to understand this clinically important process. There is every possibility that what we learn about developmentally programmed capillary regression will be applicable to the capillaries that support the growth of tumors or those that are the central feature of some vascular diseases.