生长分化因子-15致心房纤维化机制在心房颤动发生发展中的作用

Atrial fibrosis is the key pathogenesis of atrial fibrillation (AF), however, the mechanism has not been fully elucidated. Transforming growth factor β1 (TGF-β1) promotes cardiac fibrosis and involves in the pathogenesis of AF. As a member of TGF-β superfamily, growth differentiation factor-15 (GDF-15) is a stress-induced secreting protein. GDF-15 and TGF-β1 proteins share a common functioning domain. However, whether GDF-15 has similar effect on atrial fibrosis has not been documented. Our previous study firstly demonstrated that GDF-15 is secreted by cardiac fibroblasts. Our data also showed that GDF-15 activates ERK phosphorylation, resulted in promoting fibroblasts proliferation and collagen synthesis. Our clinical trial revealed that the significantly elevated GDF-15 levels were positively correlated to the atrial diameter in AF patients. In this project, we hypothesize that cardiac cells perceiving abnormal electrical signals increase the synthesis and secretion of GDF-15, acting on atrial fibroblasts, increasing cell proliferation, collagen synthesis and phenotypic transformation, leading to atrial fibrosis and the occurrence and maintenance of AF. We design experiments on cell, rats and moleculars respectively, use the adeno-associated virus, siRNA and gene knock-out technology to down-regulate or up-regulate the expression of GDF-15, and observe the effects of GDF-15 on the function of atrial fibrosis, to demonstrate the potential signal transduction pathway. In this research, we focus on the role of GDF-15 and its signal regulation in atrial fibrosis, and we will lay the theoretical and experimental basis for the new strategy of prevention and treatment of AF.

心房纤维化是心房颤动（房颤）的关键致病环节，其作用机制尚未阐明。转化生长因子-β1（TGF-β1）具有明确的促纤维化作用并参与房颤发生。生长分化因子-15（GDF-15）是TGF-β超家族的一种应激蛋白，与TGF-β1拥有共同结构域，是否发挥类似的促心房纤维化作用尚无报道。我们率先发现GDF-15由心脏成纤维细胞分泌，并激活ERK促进成纤维细胞增殖和胶原合成；近期发现房颤患者血清中显著升高的GDF-15与左房前后径正相关。因此我们提出科学假说：异常电信号引起心房GDF-15应激性合成增加，诱导心房成纤维细胞增殖、胶原合成，导致心房纤维化，参与房颤发生和维持。本项目拟采用腺相关病毒、siRNA及基因敲除技术分别实现GDF-15过表达及下调，从在体、细胞和分子水平证实该假说，阐明GDF-15促心房纤维化、导致房颤发生发展的新机制，为研发以GDF-15为靶点的房颤防治新策略奠定理论和实验基础。

房颤患者心房纤维化的发生和恶化是房颤发生与维持的关键病理机制，因此心房纤维化的防治手段是本领域的研究重点。本课题组前期研究发现，生长分化因子-15（GDF-15）具有促进心室成纤维细胞增殖的作用。因此，我们开展了本项目研究，旨在探明GDF15与房颤和心房纤维化的关系，阐明GDF-15通过何种机制影响房纤维化，以期为房颤的防治提供新的线索。我们通过纤维化模型及基因敲除技术，采用原代细胞培养，流式细胞学、分子生物学和代谢组学等方法与技术，对GDF-15参与心房纤维化的分子机制进行了初步研究。首先原代细胞培养构建心房来源的成纤维细胞的纤维化模型；其次，发现了与野生型相比，GDF-15基因敲除大鼠心脏重构更为严重；GDF-15敲除能够加重交感持续激动所致大鼠心脏重构和心功能减退，GDF-15敲除亦加重升主动脉缩窄术（TAC）所致心脏重构和心功能减退。.在此基础上，进一步探讨了GDF-15与房颤类型和消融术后复发事件的相关性。入组156例房颤住院患者，38例健康人为对照。结果发现：房颤组血清GDF-15水平明显高于对照组，持续性房颤组血清GDF-15水平明显高于阵发性房颤组；升高的GDF-15与左心房重构程度、消融术后复发事件呈正相关。此外，课题组代谢组和氧化脂质定量分析显示：房颤消融术后复发者血清花生四烯酸（AA）及其代谢物12-羟基-二十碳四烯酸（12-HETE）水平高于健康对照和未复发者，提示AA及其代谢物可能参与了房颤复发的重要代谢途径，拓宽了房颤心房纤维化机制的研究领域。综上，我们的研究证实，GDF15与心脏重构密切相关，GDF15可作为房颤心房重构及消融术后复发事件的指示或预警生物标志物；干预GDF15，有望实现对房颤心房纤维化的恶性发展的遏制，GDF15是一种潜在的防治心房纤维化进展的靶标。