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

房颤是最常见的疾病之一，每年导致至少18万人死亡 预计到2030年，美国将有1200万人受到影响。过度的心房纤维化增加了阻力 通过为房性折返性心律失常创造底物来治疗和降低房颤患者的无房颤存活率。 间质纤维化增加是由分泌过量的功能障碍的心房成纤维细胞(ACF)引起的 胶原蛋白进入细胞外基质。然而，信号通路的详细分子机制 对ACF的调控尚未被发现，这可能使开发一种新的治疗房颤的方法成为可能。这个 Wehrens Lab与Reilly博士合作(大学)最近发现降钙素(CT)是一种旁分泌物质 心肌细胞释放的抑制心房纤维化的信号分子。研究表明， 在一种新的自发性房颤小鼠模型中，CT过表达改善了房颤的进展。此外，它还发现 CT处理人ACF可抑制BMP1的切割活性，减少胶原沉积。 BMP1是一种锌依赖的蛋白水解酶，能裂解和激活几种促纤维化底物，包括转化生长因子-1。 转化生长因子大潜伏复合体(β)释放分泌的促纤维化信号蛋白转化生长因子-β。然而，BMP1的作用 哪些是由CT监管的，还没有确定。虽然之前的研究表明CT治疗 改善小鼠房颤的发展，它还发现房颤患者的ACF对CT治疗有抵抗力 因为CT受体(CTR)随着房颤的进展而下调。假设是CT的降低 活化ACF上的受体导致BMP1活性增强，更多的转化生长因子-βLLC切割，从而更多 心房纤维化和房颤进展。为了验证这一假设，目标1将确定BMP1的活性是否在 CT对人ACF转化生长因子-β的调节作用，目的2将决定BMP1基因敲除是否具有保护作用。 小鼠心房纤维化和房颤的发生发展。这些研究将提供更详细的了解 CT下游信号通路在心房纤维化和房颤中的作用并为新的基因治疗提供候选 减少心房纤维化治疗房颤的途径。为实现这些目标，拟议的培训计划 包括学习光学测绘、遥测心电记录和分析等相关研究技能， 以及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，他们护理房颤和其他心律失常的患者并进行练习 在圣何塞诊所研究生院学习临床技能。研究环境同样非常适合于 项目和培训目标，包括专门用于分子生物学研究的实验室空间，小鼠 电生理学和遥测记录、小鼠手术和光学标测以及导师和 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成为一名 医生-科学家，并将基础科学研究与病人护理相结合。

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.