Transmembrane Proteolytic Induction and Thoracic Aneurysms

描述(由申请人提供)：胸主动脉瘤(TAA)是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的临床例子。外科重建/血管内介入对于TAA是可能的，但本身风险很高，并且不影响导致这种毁灭性疾病的潜在途径。该实验室和其他实验室已经证明，在TAAS患者中，一种特定的蛋白水解酶--基质金属蛋白酶(MMPs)--增加。利用本实验室建立的小鼠TAA模型，证实了TAA进展与基质金属蛋白酶诱导/激活状态之间的因果关系。然而，目前尚不清楚这些ECM改变和TAA进展是如何以及哪些类型的MMPs引起的。我们最近发现，随着TAA的进展，一种独特的MMP1膜类型(MT1-MMPs)表达上调，并伴随着ECM结构的丧失、间质血管纤维化以及胸主动脉成纤维细胞向肌成纤维细胞表型的转变。我们的新结果证实，MT1-MMP裂解潜在的转化生长因子-β(TGF)结合蛋白-1(LTBP-1)，进而增强这一潜在的促纤维化信号通路的信号。因此，本研究的中心假设是MT1-MMP的诱导以一种双相的方式参与了TAAS的自然发展--起始于增强的ECM蛋白分解，以及通过改变的成纤维细胞表型和异常的胶原堆积而进展，这是一个MT1-MMP/TGF驱动的过程。这一假说将通过以下特定目的来解决：(1)通过转基因减少和扩增MT1-MMPs，建立早期诱导MT1-MMP主要引起局部和放大的MMP蛋白水解性反应并启动TAA，而延长MT1-MMPs诱导通过LTBP-TGF机制导致促纤维化信号增强，从而维持ECM重塑和TAA进展。(2)利用RNA干扰(SiRNA)，证明在TAA进展过程中早期诱导MT1-MMP启动子活性导致MMP蛋白水解酶活性的净放大和ECM结构完整性的丧失。(3)证实长时间的MT1-MMPs诱导可引起主动脉成纤维细胞表型转换，从而选择性靶向成纤维细胞特异性MT1-MMP会直接抑制TAA的进展。这些研究将确定跨膜蛋白分解途径如何促进TAA的传播，从而为这种隐匿和临床破坏性疾病的诊断和治疗策略的发展提供新的见解。 公共卫生相关性：胸主动脉的一种常见疾病，由于扩张、扩张和可能的破裂而导致其均匀结构的丧失，称为胸主动脉瘤病。这项研究将确定主动脉壁内的分子如何导致主动脉壁的破坏并导致动脉瘤的形成。由于这种疾病没有治愈的方法，这项研究将第一次确定我们如何能够在主动脉破裂之前预测和阻止胸主动脉瘤，从而挽救这种疾病患者的生命。

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.