高同型半胱氨酸参与房颤发生的分子机制研究

Atrial structural remodeling plays a key role in the maintenance and recurrence of atrial fibrillation(AF), with interstitial fibrosis as its basic characteristics. Hyperhomocysteinemia is a strong independent risk factor for cardio- and cerebrovascular diseases. Recent studies demonstrate it also has a close link with the development of AF. However, the detailed mechanism behind this relationship is still unclear. Herein, based on our previous study results, the hypothesis is proposed that hyperhomocysteinemia may induce the extracellular matrix and connexin remodeling via activating MMPs, contributing to the interstitial fibrosis and the development of AF. A dog model of hyperhomocysteinemia is to be created, aiming at comparing the atrial refractory period, the ability to induce and maintain AF under different concentrations of high homocysteine, examining the mRNA and protein expressions of MMPs, TIMPs, connexins and collagens, the volume fraction of collagens and connexins, and investigating the immunofluorescence distribution of MMPs. The validation of the hypothesis will help to illustrate the molecular mechanism of high homocysteine in the development of AF, identify novel targets for intervention, and provide new theoretical basis for AF management.

心房结构重构在房颤的维持和复发中起着关键性的作用，其基本特征是心房间质纤维化。高同型半胱氨酸血症是心、脑血管疾病强大的独立危险因素，近来研究显示它与房颤的发生也密切相关。然而，高同型半胱氨酸参与房颤结构重构的可能机制，目前并不清楚。本课题在前期研究基础上提出假设，高同型半胱氨酸可能通过激活MMPs，诱导心房肌细胞外基质的重构，影响缝隙连接蛋白的重塑，促进心房间质纤维化的形成，从而参与房颤的发生。本课题拟建立高同型半胱氨酸犬模型，比较不同浓度下的心房不应期、房颤诱发率、房颤维持率，MMPs、TIMPs、缝隙连接蛋白和胶原蛋白的mRNA和蛋白表达，胶原蛋白和缝隙连接蛋白的容积分数检测，以及MMPs的免疫荧光定位检测。本假设的验证将有助于阐明高同型半胱氨酸参与房颤发生的分子机制，揭示新的干预靶点，为房颤临床防治提供新的理论依据和思路。

心房颤动(简称房颤)是临床上最常见且危害严重的持续性心律失常，其发病率随年龄增长呈持续增高的趋势，在80岁以上的人群中可达10%。高龄不仅可作为房颤发生的独立危险因素，还可作为房颤最严重的并发症脑卒中的独立危险因素。年龄>65岁在CHA2DS2-VASc评分系统中计1分，年龄>75岁在CHA2DS2-VASc评分系统中计2分。MicroRNA(miRNAs)是一类由内源基因编码的长度约为22个核苷酸的非编码单链RNA分子，参与转录后的基因表达调控。迄今已有多种miRNAs被报道与房颤的发生之间存在因果关系，调控miRNAs的表达可以增加或降低对房颤的易感性，这提示miRNAs可作为房颤的潜在治疗靶点。.鉴于此，本研究入选不具备房颤发生的危险因素的行心外科手术的患者，留取右心耳处心肌组织，窦律组分为40岁组、50岁组、60岁组和70岁组，房颤组分为60岁组、70岁组。行microRNA sequence和mRNA sequence检测，并对测序数据进行生物信息学分析，发现了62个与年龄相关的miRNA，30个与房颤相关的miRNA。将二者进行综合分析，发现了与房颤和年龄均相关的差异表达的13个miRNAs，包括hsa-miR-4421、hsa-miR-3128、hsa-miR-378b、hsa-miR-548ag、hsa-miR-548ah-5p、hsa-miR-183-5p、hsa-miR-516a-5p，以及6个既往未曾发现的novel miRNAs包括novel_miR8、novel_miR66、novel_miR223、novel_miR226、novel_miR236、novel_miR274。选取表达差异倍数最显著的miRNAs进行靶基因预测，发现下游基因在cytokine activity、calcium ion binding、growth factor activity三个Molecular Function类term富集。本课题从转录组学的层面系统探讨与房颤和年龄、衰老之间的关系，筛查了与房颤增龄性相关的miRNA，阐明了新的房颤相关的信号通路和潜在的干预靶点。