Lymph vs. blood angiogenesis: functional differences in*

描述（由申请人提供）： 尽管淋巴管生成在重要的病理生理过程如肿瘤转移中具有重要性，但淋巴管再生的生理学比血管生成的生理学了解得少得多。 事实上，人们通常认为淋巴管生成的许多方面与血管生成的许多方面相似。 这项生物工程研究将解决这两个过程之间的差异，使用体外模型以及一种新的动物模型再生皮肤中的淋巴管生成，在我们的实验室开发。 我们使用该模型对淋巴发育的初步观察表明：1）流体通道形成发生在淋巴管内皮细胞（LEC）组织化之前，2）LEC在组织化成血管之前作为单细胞在间隙空间内迁移，3）蛋白酶活性、流体通道、VEGF-C蛋白表达和LEC迁移都主要发生在上游端，与淋巴液流动方向一致，和4）尽管上皮细胞迁移和血管生成相同，但间质流动减少中断了毛细淋巴管组织。 在该模型中获得的这些观察结果表明淋巴管生成和血管生成之间存在明确和根本的差异，其中发芽血管表面的MMP活性允许毛细血管进展，并且其中BEC总是与其相邻细胞连接并暴露于管腔，即使在增殖和推进时。 它们也代表了淋巴发育受间质流影响的第一个证据。 基于初步数据，我们的工作假设如下：间质液流是淋巴管生成的起始事件，通过引起MMP上调和在流动方向上的运输（“流动”），导致流体通道形成和定向LEC沿这些通道沿着迁移。 然后，LEC组织起来将原始流体通道改造成功能最佳的毛细淋巴管网络。 本研究将探讨这一假设，并连接的功能，其形成过程中的几个方面，相关的生化和生物物理/运输介质在淋巴管生成，注意流体通道，重塑细胞外基质（ECM），LEC迁移，VEGF-C的表达，和毛细淋巴管网络的形成。 蛋白酶流动在通道形成中的作用将被阐明，VEGF-C的促有丝分裂功能与形态发生功能也将被阐明。 在体外，我们将LEC的液体和生长因子的反应与淋巴管生成过程中在体内观察到的LEC行为相关联，我们将这些结果进行比较，BEC在体外的反应。

DESCRIPTION (provided by applicant): The physiology of lymphatic regeneration is much less understood than that of angiogenesis, in spite of the importance of lymphangiogenesis in important pathophysiological processes such as tumor metastasis. Indeed, it is generally assumed that many aspects of lymphangiogenesis parallel those in angiohgenesis. This bioengineering study will address the differences between these two processes, using in vitro models as well as a novel animal model of lymphangiogenesis in regenerating skin, developed in our laboratory. Our preliminary observations of lymphatic development using this model indicate that: 1) fluid channel formation occurs prior to lymphatic endothelial cell (LEC) organization, 2) LECs migrate as single cells within the interstitial space before organizing into vessels, 3) protease activity, fluid channeling, VEGF-C protein expression, and LEC migration all occur predominantly from the upstream end, consistent with the direction of lymph flow, and 4) reduction of interstitial flow interrupted lymphatic capillary organization, despite identical epithelial cell migration and angiogenesis. These observations obtained in this model suggest clear and fundamental differences between lymphangiogenesis and blood angiogenesis, where MMP activity at the surface of the sprouting vessel allow capillary progression and where BECs are always connected to their neighboring cells and exposed to a lumen, even while proliferating and advancing. They also represent the first evidence that lymphatic development is influenced by interstitial flow. Based upon preliminary data presented, our working hypothesis is as follows: Interstitial fluid flow is an initiating event in lymphangiogenesis by causing MMP upregulation and transport ("streaming") in the direction of flow, leading to fluid channel formation and directed LEC migration along those channels. The LECs then organize to remodel the crude fluid channels into a functionally optimal network of lymphatic capillaries. This investigation will explore this hypothesis and connect the function of the lymphatics to the process of their formation in several regards, correlating biochemical and biophysical/transport mediators in lymphangiogenesis, with attention to fluid channeling, remodeling of the extracellular matrix (ECM), LEC migration, VEGF-C expression, and lymphatic capillary network formation. The role of protease streaming in channel formation will be clarified, as will the mitogenic vs. morphogenetic function of VEGF-C. In vitro, we will correlate LEC responses to fluid and growth factors with LEC behavior observed in vivo during lymphangiogenesis, and we will compare those results to BEC responses in vitro.