Transmembrane Proteolytic Induction and Thoracic Aneurysms

描述（由申请人提供）：心血管系统内细胞外基质破坏导致毁灭性疾病过程的一个戏剧性临床例子是胸主动脉瘤（TAAs）。手术重建/血管内干预对TAAs是可能的，但其本身是高风险的，并且不影响导致这种毁灭性疾病的潜在途径。这个实验室和其他实验室已经证明，一种特殊的蛋白水解酶，基质金属蛋白酶（MMPs），在taa患者中增加。利用本实验室建立的小鼠TAA模型，证明了TAA进展与MMP诱导/激活状态之间的因果关系。然而，目前尚不清楚哪种MMP类型是如何导致这些ECM改变并促进TAA进展的。我们最近发现一种独特的MMP，即膜型-1 （MT1-MMP）随着TAA的进展而上调，并伴有ECM结构的丧失、间质血管纤维化和胸主动脉成纤维细胞向肌成纤维细胞表型的转变。我们的新研究结果表明，MT1-MMP可以切割潜在的转化生长因子- β (TGF)结合蛋白-1 (LTBP-1)，这反过来会增强这种有效的促纤维化信号通路的信号传导。因此，本研究的中心假设是，MT1-MMP的诱导以两阶段的方式促进了TAAs的自然历史-由于ECM蛋白水解增强而开始-以及通过改变成纤维细胞表型和异常胶原积累而进展，这是一个MT1-MMP/TGF驱动的过程。这一假设将通过以下具体目标来解决：(1)通过转基因MT1-MMP的还原和扩增，确定MT1-MMP的早期诱导主要引起局部和扩增的MMP蛋白水解反应并启动TAA，而MT1-MMP的长期诱导通过LTBP-TGF机制引起纤维化信号的增强，从而维持ECM重塑和TAA的进展。(2)利用RNA干扰（siRNA），证明在TAA进展中MT1-MMP启动子活性的早期诱导导致MMP蛋白水解活性的净扩增和ECM结构完整性的丧失。(3)证实长时间的MT1-MMP诱导导致主动脉成纤维细胞表型转换，因此选择性靶向成纤维细胞特异性MT1-MMP将直接减弱TAA进展。这些研究将确定跨膜蛋白水解途径如何促进TAA的繁殖，从而为这种隐匿性和临床毁灭性疾病的诊断和治疗策略的发展提供新的见解。

DESCRIPTION (provided by applicant): A dramatic clinical example of where disruption of the extracellular matrix within the cardiovascular system leads to a devastating disease process is thoracic aortic aneurysms (TAAs). Surgical reconstruction/endovascular interventions are possible for TAAs, but are in and of themselves high risk and do not affect the underlying pathways which drive this devastating disease. This laboratory and others have demonstrated that a specific cassette of proteolytic enzymes, the matrix metalloproteinases (MMPs), are increased in patients with TAAs. Using a murine TAA model developed by this laboratory, a cause-effect relationship was demonstrated between TAA progression and MMP induction/activational states. However, it remains unclear how and which MMP types are causative to these ECM changes and contribute to TAA progression. We have recently identified that a unique MMP, membrane type-1 (MT1-MMP) was up regulated with TAA progression and was accompanied by a loss in ECM architecture, interstitial vascular fibrosis, and a switch of thoracic aortic fibroblasts to a myofibroblast phenotype. Our new results have established that MT1-MMP cleaves the latent transforming growth factor-beta (TGF) binding protein-1 (LTBP-1), which would in turn enhance signaling of this potent profibrotic signaling pathway. Thus, the central hypothesis of this study is that the induction of MT1-MMP contributes to the natural history of TAAs in a bi-phasic manner- initiation due to enhanced ECM proteolysis, - and progression through an altered fibroblast phenotype and abnormal collagen accumulation which is an MT1-MMP/TGF driven process. This hypothesis will be addressed through the following specific aims: (1) Through transgenic reduction and amplification of MT1-MMP, establish that early induction of MT1-MMP primarily causes a localized and amplified MMP proteolytic response and initiates the TAA, whereas prolonged MT1- MMP induction causes heightened profibrotic signaling through an LTBP-TGF mechanism thereby sustaining ECM remodeling and TAA progression. (2) Using RNA interference (siRNA), demonstrate the early induction of MT1-MMP promoter activity in TAA progression results in a net amplification of MMP proteolytic activity and a loss of ECM structural integrity. (3) establish that prolonged MT1-MMP induction causes a phenotypic switch in aortic fibroblasts, whereby selective targeting of fibroblast specific MT1-MMP will directly attenuate TAA progression. These studies will establish how a transmembrane proteolytic pathway contributes to TAA propagation and thereby provide new insights for the development of diagnostic and therapeutic strategies for this insidious and clinically devastating disease. PUBLIC HEALTH RELEVANCE: A common disease of the thoracic aorta, causing a loss of its uniform structure by expansion, dilation, and possible rupture, is termed thoracic aortic aneurysm disease. This study will identify how molecules within the wall of the aorta can cause destruction of the aortic wall and induce an aneurysm formation. Because there is no cure for this disease, this study will be the first to identify how we might be able to predict and stop thoracic aortic aneurysms before the aorta ruptures, thereby saving lives of patients with this disease.