Targeting the Calcitonin-BMP1 Pathway in Atrial Cardiofibroblasts to Ameliorate Atrial Fibrillation

最常见的疾病之一是心房纤颤（AF），其每年导致至少18万人死亡 预计到2030年将影响到美国1200万人。过度心房纤维化增加阻力 通过形成房性折返性心律失常的基质，降低AF患者的无AF生存率。 增加的间质纤维化是由功能障碍的心房心脏成纤维细胞（ACF）引起的， 胶原进入细胞外基质。然而，信号通路的详细分子机制 调节活性碳纤维尚未被发现，这可能使开发一种新的治疗AF。 Wehrens实验室与Reilly博士（牛津大学）合作，最近发现降钙素（CT）是一种旁分泌 从心肌细胞释放并抑制心房纤维化的信号分子。研究表明 CT过表达改善了一种新型自发性AF小鼠模型中的AF进展。 用CT处理人培养的ACF抑制BMP 1切割活性并减少胶原沉积。 BMP 1是一种锌依赖性蛋白酶，其切割并激活几种促纤维化底物，包括TGF-β 1。 β大潜伏复合物（LLC）释放分泌的TGF-β，一种促纤维化信号蛋白。然而，BMP 1的作用 受CT监管的产品尚未确定。虽然之前的研究表明CT治疗 改善了小鼠AF的发展，还发现AF患者的ACF对CT治疗有抵抗力 因为CT受体（CTR）随着AF进展而下调。假设CT的减少 ACF上的受体活化导致BMP 1活性增强，更多的TGF-β LLC裂解，从而更多的 心房纤维化和AF进展。为了验证这一假设，Aim 1将确定BMP 1活性是否介导 CT对人ACFs中TGF-β的调节，目的2将确定Bmp1敲除是否能防止 小鼠心房纤维化和房颤的发展。这些研究将提供更详细的了解， 心房纤维化和AF中CT下游信号通路，并为新的基因治疗提供了候选者 方法，以减少心房纤维化的治疗房颤。为了实现这些目标，提出的培训计划， 包括学习相关的研究技能，如光学测绘，遥测心电图记录和分析， 和用于分析纤维化的组织学。培训计划的另一个方面涉及跟踪心脏病专家 在整个德克萨斯医疗中心，他们照顾AF和其他心律失常患者， 在圣何塞诊所读研究生期间获得临床技能。研究环境也非常适合 该项目和培训目标，包括专门的实验室空间的分子生物学研究，小鼠 电生理学和遥测记录，小鼠手术，光学测绘以及导师， 致力于确保项目成功的博士后同事。除了帮助实现 拟议的研究目标，培训计划和环境也将使职业目标成为一个 医生-科学家和整合基础科学研究与病人护理要实现。

One of the most prevalent diseases is atrial fibrillation (AF), which contributes to at least 180,000 deaths annually and is expected to affect twelve million people in the U.S. by 2030. Excessive atrial fibrosis increases resistance to therapy and decreases AF-free survival in AF patients by creating a substrate for atrial reentrant arrhythmias. Increased interstitial fibrosis is caused by dysfunctional atrial cardio-fibroblasts (ACFs) that secrete excessive collagen into the extracellular matrix. However, detailed molecular mechanisms of the signaling pathways regulating ACFs are yet to be uncovered, which could enable the development of a novel treatment for AF. The Wehrens Lab in collaboration with Dr. Reilly (Univ. of Oxford) has recently identified calcitonin (CT) as a paracrine signaling molecule that is released from cardiomyocytes and suppresses atrial fibrosis. The study showed that CT overexpression ameliorates AF progression in a novel murine model of spontaneous AF. Moreover, it found that treating human cultured ACFs with CT inhibited BMP1 cleavage activity and reduced collagen deposition. BMP1 is a zinc-dependent protease that cleaves and activates several profibrotic substrates, including the TGF- β large latent complex (LLC) to release secreted TGF-β, a profibrotic signal protein. However, the roles of BMP1 that are regulated by CT have yet to determined. While the previous study suggests that CT treatment ameliorates AF development in mice, it also found that ACFs from AF patients are resistant to CT treatment because the CT receptor (CTR) is downregulated as AF progresses. The hypothesis is that a reduction in CT receptor activation on ACFs leads to enhancement of BMP1 activity, more TGF-β LLC cleavage, and thus more atrial fibrosis and AF progression. To test this hypothesis, Aim 1 will determine whether BMP1 activity mediates the regulation of TGF-β by CT in human ACFs, and Aim 2 will determine whether Bmp1 knockout protects against the development of atrial fibrosis and AF in mice. These studies will provide a more detailed understanding of the signaling pathway downstream of CT in atrial fibrosis and AF and offer a candidate for a novel gene therapy approach to reduce atrial fibrosis for the treatment of AF. To accomplish these goals, the proposed training plan includes learning the relevant research skills such as optical mapping, telemetry ECG recording and analysis, and histology for analyzing fibrosis. An additional aspect of the training plan involves shadowing cardiologists throughout the Texas Medical Center as they care for patients with AF and other arrhythmias and practicing clinical skills during graduate school at the San José Clinic. The research environment is likewise well suited to the project and training goals and includes dedicated lab spaces for molecular biology studies, mouse electrophysiology and telemetry recording, mouse surgery, and optical mapping as well as a mentor and postdoctoral associates who are committed to ensuring the project is successful. In addition to helping to achieve the proposed research goals, the training plan and environment will also enable career goals of becoming a physician-scientist and integrating basic science research with patient care to be achieved.