Intracellular signals and smooth muscle cell migration

中膜平滑肌细胞（SMC）在血管损伤后向内膜迁移是动脉粥样硬化和再狭窄病变发展过程中发生的重塑的主要组成部分。生长因子如PDGF和神经营养因子，分别激活PDGF和trk受体酪氨酸激酶，是血管SMC的有效趋化剂。细胞迁移受到高度调节，首先需要细胞从细胞外基质中脱离，然后是细胞骨架的重组，最后是基质金属蛋白酶的释放，以降解基底膜并允许SMC从中膜进入内膜。协调细胞脱离、细胞骨架重组和MMP释放的复杂过程的信号传导机制尚不清楚。本提案的总体目标是剖析调节SMC迁移的下游途径，以响应神经营养因子和PDGF，从而确定这两种不同的受体酪氨酸激酶是否利用细胞或互补信号传导机制来诱导定向细胞迁移。具体而言，我们计划：识别由生长因子和粘附分子激活的信号通路，这些信号通路启动细胞脱离、细胞骨架重组和对迁移刺激的局部粘附的转换。二. 确定金属蛋白酶在生长因子启动SMC迁移中的作用。三.直接评估神经营养因子BDNF在明确定义的血管损伤模型中对病变发展的作用。将在维持高脂饮食的小鼠中长期研究BDNF或BDNF受体trk B缺陷的Apo E（-/-）小鼠中的病变发展，并使用无血管损伤的流动依赖性颈动脉结扎模型进行急性研究。这些研究将使我们能够测试受损的BDNF：trk B信号传导是否减少新生内膜形成。这些研究涉及与Roy Silverstein博士（项目III）、Kathy Hajjar博士（项目II）和大卫Hajjar博士（项目VI）的关键互动。

Migration of medial smooth muscle cells (SMC) into the intima in response to vascular injury is a major component of the remodeling which occurs in the development of atherosclerotic and restonotic lesions. Growth factors such as PDGF and the neurotrophins, which activate the PDGF and trk receptor tyrosine kinases, respectively, are potent chemotactic agents for vascular SMC. Cellular migration is highly regulated, requiring first, the detachment of cells from the extracellular matrix, followed by the reorganization of the cytoskeleton, and finally, the release of matrix, metalloproteinases, to degrade the basement membrane and permit SMC to egress from the media into the intima. The signaling mechanisms which coordinate the complex processes of cellular detachment, cytoskeletal reorganization and MMP release are poorly defined. The overall aim of this proposal is to dissect the downstream pathways regulating SMC migration in response to the neurotrophins and PDGF, and thus, determine if cellular or complementary signaling mechanisms are utilized by these two different receptor tyrosine kinases to induce directed cell migration. Specifically, we plan to: I. Identify signaling pathways activated by growth factors and adhesion molecules which initiate cellular detachment, cytoskeletal reorganization and turnover t focal adhesions in response to migratory stimuli. II. Identify the contributions of metalloproteinases in growth factor-initiate SMC migration. III. Directly evaluate the role of the neurotrophin, BDNF, on lesion development in well defined models of vascular injury. Lesion development in Apo E (-/-) mice deficient in either BDNF or the BDNF receptor, trk B, will be studied chronically in mice maintained on a high fat diet and acutely using the flow dependent-carotid artery ligation model off vascular injury. These studies will allow us to test whether impaired BDNF:trk B signaling reduces neointimal formation. These studies involve critical interactions with Dr. Roy Silverstein (Project III), Dr. Kathy Hajjar (Project II) and Dr. David Hajjar (Project VI).