背景:心脏纤维化是所有形式的慢性心脏病的标志。心脏成纤维细胞的激活和增殖是心脏纤维化的主要介质。现有研究表明,纤维化过程中产生的ROS和炎性细胞因子不仅传递增殖刺激信号,而且有助于DNA损伤。因此,作为维持成纤维细胞持续增殖的先决条件,激活不同的DNA修复机制是必不可少的。
结果:在这项研究中,我们报道了TET3,一种DNA去甲基化酶,已被证明在心脏纤维化中减少并发挥抗纤维化作用不仅通过其去甲基化活性,而且通过促进DNA损伤的无错误同源重组(HR)修复来维持基因组完整性。使用心脏纤维化的体外和体内模型以及来自人类心脏组织的数据,我们证明,心脏成纤维细胞中TET3的缺失导致自发性DNA损伤,并且在TGF-β的存在下,导致从HR向快速但更容易出错的非同源末端连接修复途径的转变.这种转变有助于在纤维化环境中增加成纤维细胞增殖。体外实验显示TET3在小鼠心脏成纤维细胞中募集H2O2诱导的DNA双链断裂(DSBs),促进HR修复。过表达TET3可抵消TGF-β诱导的成纤维细胞增殖并恢复HR修复效率。将这些发现扩展到人类心脏纤维化,我们证实了TET3在纤维化心脏中的表达缺失,并确定了TET3水平之间的负相关,纤维化标志物,和DNA修复途径改变。
结论:总的来说,我们的研究结果证明了TET3在调节心脏纤维化中的DDR和成纤维细胞增殖方面的关键作用,并进一步强调了TET3是一个潜在的治疗靶点.
BACKGROUND: Cardiac fibrosis is the hallmark of all forms of chronic heart disease. Activation and proliferation of cardiac fibroblasts are the prime mediators of cardiac fibrosis. Existing studies show that ROS and inflammatory cytokines produced during fibrosis not only signal proliferative stimuli but also contribute to DNA damage. Therefore, as a prerequisite to maintain sustained proliferation in fibroblasts, activation of distinct DNA repair mechanism is essential.
RESULTS: In this study, we report that TET3, a DNA demethylating enzyme, which has been shown to be reduced in cardiac fibrosis and to exert antifibrotic effects does so not only through its demethylating activity but also through maintaining genomic integrity by facilitating error-free homologous recombination (HR) repair of DNA damage. Using both in vitro and in vivo models of cardiac fibrosis as well as data from human heart tissue, we demonstrate that the loss of TET3 in cardiac fibroblasts leads to spontaneous DNA damage and in the presence of TGF-β to a shift from HR to the fast but more error-prone non-homologous end joining repair pathway. This shift contributes to increased fibroblast proliferation in a fibrotic environment. In vitro experiments showed TET3\'s recruitment to H2O2-induced DNA double-strand breaks (DSBs) in mouse cardiac fibroblasts, promoting HR repair. Overexpressing TET3 counteracted TGF-β-induced fibroblast proliferation and restored HR repair efficiency. Extending these findings to human cardiac fibrosis, we confirmed TET3 expression loss in fibrotic hearts and identified a negative correlation between TET3 levels, fibrosis markers, and DNA repair pathway alteration.
CONCLUSIONS: Collectively, our findings demonstrate TET3\'s pivotal role in modulating DDR and fibroblast proliferation in cardiac fibrosis and further highlight TET3 as a potential therapeutic target.