SMOOTH MUSCLE CELL PROLIFERATION IN HUMAN CORONARY ARTERY BYPASS GRAFTS

描述（由申请人提供）：冠状动脉疾病，导致心肌梗死和缺血，影响数百万人，是全球发病率和死亡率的主要原因之一。使用隐静脉（SV）或乳内动脉（IMA）的冠状动脉旁路移植术（CABG）等侵入性技术可用于缓解动脉闭塞的后遗症。不幸的是，由于移植静脉导管中血管平滑肌细胞（VSMC）的增殖，再狭窄在数月至数年内发生，伴随着通畅性的逐渐降低。令人惊讶的是，IMA管道免于纤维增生的病理影响。然而，作为这种差异基础的潜在细胞和分子机制尚不清楚。机械力在静脉移植物疾病的发病机制中起重要作用。切应力的改变导致血管活性介质的释放并调节VSMC中的基因表达。最近，我们观察到时间失活的PTEN，多功能的脂质磷酸酶，导致SV SMCs的增殖，和PTEN过表达降低IGF-1受体和细胞增殖。我们还发现，增加连接蛋白43（Cx43）的表达与血管紧张素II（Ang II）和IGF-1的刺激SMC SV的增殖显着增加比IMA。由于PTEN调节细胞信号传导和细胞生长，并且涉及Cx43的细胞之间的通信在内膜增生的发展中起关键作用，因此现在提出研究PTEN在Cx43表达和IGF-1和Ang II激活的信号传导中的调节作用，以及沿着相关的促增生途径。中心假设是，PTEN以反馈方式减少IGF-1受体，以通过控制PI 3 K-Akt/PKB促增生途径和MAPK-AP-1-Cx43表达来调节血管紧张素II-IGF-1诱导的来自人CABG导管的平滑肌细胞的增殖和存活。目标1：研究PTEN对IGF-1和Ang-II诱导的IGF-1受体表达和PI 3 K-Akt/PKB和MAPK通路在人SV和IMA的SMC中的激活以及对所得增殖的反馈作用。目标2：研究PTEN过表达对IGF-1和Ang-II刺激的人SV和IMA SMCs中MAPK-AP-1-Cx43表达和激活的影响，以及对所产生的增殖的影响。目标3：检测PTEN过表达对Ang-II和IGF-1诱导的细胞周期蛋白依赖性激酶抑制剂（CKIs; p21、p27和p53）、细胞周期蛋白D和E、Rb蛋白和E2 F在人SV和IMA的SMC中的表达和活化的影响，以及对所得增殖的影响。比较SV和IMA旁路移植物增生发生的确切机制，为制定上级治疗策略提供了机会。公共卫生相关性：冠状动脉搭桥手术的长期结果受到血管再闭合的影响，血管再闭合主要发生在隐静脉移植物中，而乳内动脉几乎仍然抵抗再闭合。在这个项目中，实验提出了在细胞和分子水平上研究潜在的精确机制。从本研究中获得的信息应提供制定上级治疗方法的机会。

DESCRIPTION (provided by applicant): Coronary artery disease, leading to myocardial infarction and ischemia, affects millions of people and is one of the leading causes of morbidity and mortality worldwide. Invasive techniques such as coronary artery bypass grafting (CABG) using the saphenous vein (SV) or internal mammary artery (IMA) are used to alleviate the sequelae of arterial occlusion. Unfortunately, restenosis, due to proliferation of vascular smooth muscle cells (VSMCs) in the grafted venous conduit, occurs within months to years with a gradual reduction in patency. Surprisingly, the IMA conduits are spared from the pathologic effects of fibroproliferation. However, the underlying cellular and molecular mechanisms, which are the basis for this difference, are unclear. Mechanical forces play an important role in the pathogenesis of vein graft disease. Alterations in shear stress result in the release of vasoactive mediators and modulate gene expression in VSMCs. Recently, we observed temporal inactivation of PTEN, a multifunctional lipid phosphatase, causing proliferation of SV SMCs, and that PTEN overexpression decreased IGF-1 receptors and cell proliferation. We also found that increased connexin43 (Cx43) expression following stimulation of SMCs with angiotensin II (Ang II) and IGF-1 significantly increases proliferation in the SMCs of SV than in the IMA. Since PTEN modulates cell signaling and cell growth, and communication between cells involving Cx43 plays a crucial role in the development of intimal hyperplasia, investigation of the regulatory role of PTEN in Cx43 expression and IGF-1 and Ang II- activated signaling, along with associated pro-hyperplasia pathways is now proposed. The central hypothesis is that PTEN decreases IGF-1 receptors in a feedback manner to regulate angiotensin II-IGF-1- induced proliferation and survival of smooth muscle cells from human CABG conduits by controlling PI3K-Akt/PKB pro-hyperplasia pathway and MAPK-AP-1-Cx43 expression. AIM 1: To examine the feedback effect of PTEN on IGF-1- and Ang-II-induced IGF-1 receptor expression and activation of the PI3K-Akt/PKB and MAPK pathways in SMCs of human SV and IMA and on the resultant proliferation. AIM 2: To investigate the effect of PTEN overexpression on the expression and activation of MAPK-AP-1-Cx43 in IGF-1- and Ang-II-stimulated SMCs of human SV and IMA, and on the resultant proliferation. AIM 3: To examine the effect of PTEN overexpression on Ang-II and IGF-1-induced expression and activation of cyclin- dependent kinase inhibitors (CKIs; p21, p27, and p53), cyclin D and E, Rb protein and E2F in SMCs of human SV and IMA, and on the resultant proliferation. The comparison of the precise mechanisms involved in the development of hyperplasia in SV and IMA bypass grafts should provide an opportunity to formulate superior therapeutic strategies. PUBLIC HEALTH RELEVANCE: Long term outcome of coronary artery bypass surgeries is compromised by re-closure of the vessels, which predominantly occurs in saphenous vein grafts while the internal mammary artery remains almost resistant to re-closure. In this project experiments are proposed to examine the underlying precise mechanisms at the cellular and molecular level. The information obtained from this study should provide an opportunity to formulate superior therapeutic approaches.