Semaphorin3a结合Neuropilin1调控心房重构在房颤发病中的作用和机制研究

Atrial structural and electrical remodeling is the key process in the pathogenesis of atrial fibrillation (AF). Studies have shown that semaphorin3a (Sema3a) has been involved in the regulation of heart development and cardiac rhythm. However, the role of Sema3a in AF is currently unknown. Sema3a is one of the ligands of neuropilin1 (NRP1). The NRP1 mutant Mice carrying the amino-acids mutation locating at the a1 domain damaged the binding between Sema3a and NRP1, and led to the abnormal structure of atria which was very similar to the phenotype of Sema3a knockout mice. Our preliminary experiments showed that the serum level of sema3a in AF patients was significantly lower than that in non-AF patients. And the expression of Sema3a was also lower in the cardiac tissue of the AngiotensinII (AngII) induced atrial fibrosis model comparing with the control. For the AngII induced atrial fibrosis model, the NRP1 mutant mice had larger atrial dimension and higher incidence of AF than the wild-type (WT) mice. The mRNA level of atrial fibrosis markers, such as Collagen-I, were also higher in the mutant mice than the WT. Additionally the current density was also different between the mutant and WT atrial myocytes that the ICa-L decreased and Ito increased in the mutant ones. And the action potential duration was detected to be shortening in the mutant than the WT. Therefore, we hypothesize that Sema3a could prevent atrial fibrosis and regulate the membrane currents of atrial cells through the binding of NRP1. And our study is planned to investigate the role of Sema3a in the process of atrial structural and electrical remodeling and discuss the underlying mechanism, which might be a new target for the therapy of AF.

心房结构和电重构是房颤发生维持的重要环节。Semaphorin3a(Sema3a)与心脏结构发育、心律调节相关，其在房颤中的作用尚未明确。作为Sema3a的受体，Neuropilin1(NRP1)a1结构域氨基酸突变的小鼠中Sema3a不能与NRP1结合。我们前期研究发现房颤患者血浆Sema3a减少，小鼠心房纤维化房颤模型中心肌组织Sema3a表达减少。且NRP1突变小鼠房颤诱发率增多，心肌组织纤维化信号增多，心房肌细胞ICa-L减少，Ito增加，易诱发后除极。故我们假设Sema3a可通过结合NRP1，抑制心房纤维化过程，并影响离子通道电流，参与抑制心房结构及电重构过程。本项目拟：明确Sema3a对心房纤维化及心肌电生理特性的调控作用，研究Sema3a-NRP1调节心房结构及电重构的具体机制，从而为房颤治疗提供新作用靶点。

本项目拟研究Semaphorin3a（Sema3a）在房颤发生发展中的影响及其相关机制。我们拟首先研究Sema3a通过Neuropilin1调控心房结构重构、心房纤维化程度、电重构，离子通道电流情况，来影响房颤发生发展。这是我们近年来科研工作的逻辑延伸，对于阐明房颤发病机制中结构重构及电重构的相关具体机制具有重要的科学意义。项目组在执行该研究过程中，发现体外过表达Sema3a小鼠，在AngII诱发房颤模型中，相比于对照组其房颤发生率下降，左心房直径下降，纤维化相关指标（Collagen-I、Collagen-III、PAI-1、CTGF）mRNA水平明显下调，可以明显减轻心房纤维化程度，减少心房结构重构的发生。此外，将前期已制作完成的NRPSema-小鼠和WT小鼠，制作AngII介导的心房纤维化模型，分离成年鼠心肌细胞进行膜片钳相关研究。WT小鼠和NRPSema-小鼠分别制作AngII介导的心房纤维化模型，急性分离心肌细胞进行动作电位检测，不同组别代表性动作电位曲线，并分别测量APD25、APD50、APD90，相比于WT小鼠，NRPSema-小鼠动作电位明显缩短。间接证明Sema3a可以通过结合Neuropilin1调控心房电重构，离子通道电流情况，影响心肌细胞动作电位情况，缩短动作电位，减少DAD发生，减少心律失常事件。并进一步制作过表达Sema3a的腺病毒转染原代乳鼠心房肌细胞和心房肌成纤维细胞。并进行相关基因测序，进一步筛选下游靶分子，并将差异表达分子进行功能富集分析。综上所述，我们对本课题研究内容进一步优化，增加测序部分，及生物信息学分析，对Sema3a下游信号进一步全面分析，筛选可能的下游靶分子，为其调节房颤发生提供了更多靶点及可能的分子机制支持。

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