TNF-α信号通路调控MMP-9等关键基因DNA甲基化在衰老过程中心肌纤维化的机制

Aging is a major risk factor for the development of cardiac fibrosis and atrial fibrillation (AF). During the process of aging, one of the landmarks is DNA methylation. Thus it is of great value to investigate the role of DNA methylation in the genesis of aging-associated cardiac fibrosis. We have performed genomic analysis on subjects with and without AF in various ages. In the elderly, abnormal modifications of DNA methylation were found in specific chromosome segments. Among them, MMP-9, TRAF1, SOCS3, and TNFAIP3 were the genes with the most significant changes and greater changes occurred in AF patients compared to healthy subjects. These findings indicate that abnormal modifications of the DNA methylation of the four genes are the common signaling pathways for aging and fibrosis. We further confirmed these findings in larger samples and also found that the abnormal modifications of DNA methylation affected gene expression of MMP-9. MMP-9, TRAF1, SOCS3, and TNFAIP3 are the target genes of TNF-α signaling pathway, a key mediator in the fibrosis. We hypothesize that TNF-α signaling pathway has a significant role in cardiac fibrosis during aging via modulating the DNA methylation of MMP-9, TRAF1, SOCS3, and TNFAIP3. We plan to conduct further studies to test this hypothesis. These studies will improve our current understanding of the mechanisms underlying cardiac fibrosis during aging and hopefully facilitate the emergence of novel preventative and therapeutic strategies.

衰老是致纤维化和心房颤动(房颤)的高危因素，DNA甲基化改变是衰老过程中的标志性事件，故DNA甲基化参与衰老和心肌纤维化的分子机制是研究房颤的重大科学问题。申请人对不同年龄房颤患者和正常对照进行基因组水平DNA甲基化谱分析，发现一些染色体片段DNA甲基化修饰在衰老过程中出现改变，以MMP-9、TRAF1、SOCS3和TNFAIP3基因改变最为显著，且在房颤患者中更为明显，提示这些区域的DNA甲基化修饰异常可能是衰老和纤维化共同的分子基础。本项目大样本验证了该发现，功能学研究表明MMP-9DNA甲基化修饰异常可影响该基因表达。上述基因是TNF-α信号通路的靶基因，而该通路是参与心肌纤维化的重要通路之一。故申请人推测：TNF-α信号通路参与调控上述基因DNA甲基化异常改变在衰老纤维化中发挥关键作用，并拟从分子水平阐明该信号通路调控上述基因DNA甲基化的机制，为干预衰老进程中心肌纤维化奠定基础。

衰老过程中心肌纤维化是致心房颤动发生发展的重要基础，全基因组DNA甲基化水平改变是衰老进程中的标志性事件，但目前尚缺乏针对DNA甲基化水平改变对衰老相关心肌纤维化的具体影响的深入研究。我们前期对不同年龄房颤患者和正常对照进行的基因组水平DNA甲基化谱分析，已发现一些染色体片段如MMP-9、TRAF1、SOCS3和TNFAIP3基因甲基化表达趋势在两者的不同分布。本研究立足于前期工作基础，以房颤心房纤维化的自然病程和基因甲基化致心房纤维化为切入点，通过临床水平扩大年龄层段和样本总数对比房颤患者和健康个体的心房生理结构、心房电压特征、心房舒缩功能、心肌纤维化程度；动物水平对比衰老心脏与年轻心脏的电生理特性、四腔室生理结构以及离体心肌间质胶原蛋白沉积量；细胞水平检测不同年龄层段的房颤患者和非房颤个体的外周血有核细胞DNA甲基化水平；辅以动物的衰老心脏和年轻心脏的DNA甲基化水平变化，综合验证“DNA甲基化水平改变-心肌纤维化-心房颤动”的科学假设，从而揭示相关基因集合与通路，为探讨增龄性房颤的致病基因及其在衰老进程中表达活性改变致心肌纤维化发生机制和房颤的相应防治提供科学依据。