Department of Pathology and Laboratory Medicine College of Medicine University of Cincinnati OH.
Department of Molecular and Cellular Physiology College of Medicine University of Cincinnati OH.
J Am Heart Assoc. 2019 Aug 6;8(15):e012089. doi: 10.1161/JAHA.119.012089. Epub 2019 Jul 18.
Background Myocardial infarction results in a large-scale cardiomyocyte loss and heart failure due to subsequent pathological remodeling. Whereas zebrafish and neonatal mice have evident cardiomyocyte expansion following injury, adult mammalian cardiomyocytes are principally nonproliferative. Despite historical presumptions of stem cell-mediated cardiac regeneration, numerous recent studies using advanced lineage-tracing methods demonstrated that the only source of cardiomyocyte renewal originates from the extant myocardium; thus, the augmented proliferation of preexisting adult cardiomyocytes remains a leading therapeutic approach toward cardiac regeneration. In the present study we investigate the significance of suppressing cell cycle inhibitors Rb1 and Meis2 to promote adult cardiomyocyte reentry to the cell cycle. Methods and Results In vitro experiments with small interfering RNA-mediated simultaneous knockdown of Rb1 and Meis2 in both adult rat cardiomyocytes, isolated from 12-week-old Fischer rats, and human induced pluripotent stem cell-derived cardiomyocytes showed a significant increase in cell number, a decrease in cell size, and an increase in mononucleated cardiomyocytes. In vivo, a hydrogel-based delivery method for small interfering RNA-mediated silencing of Rb1 and Meis2 is utilized following myocardial infarction. Immunofluorescent imaging analysis revealed a significant increase in proliferation markers 5-ethynyl-2'-deoxyuridine, PH3, KI67, and Aurora B in adult cardiomyocytes as well as improved cell survivability with the additional benefit of enhanced peri-infarct angiogenesis. Together, this intervention resulted in a reduced infarct size and improved cardiac function post-myocardial infarction. Conclusions Silencing of senescence-inducing pathways in adult cardiomyocytes via inhibition of Rb1 and Meis2 results in marked cardiomyocyte proliferation and increased protection of cardiac function in the setting of ischemic injury.
心肌梗死导致大规模心肌细胞丧失和心力衰竭，这是由于随后的病理性重构所致。虽然斑马鱼和新生小鼠在损伤后表现出明显的心肌细胞扩张，但成年哺乳动物的心肌细胞主要是无增殖能力的。尽管历史上假定干细胞介导的心脏再生，但许多最近使用先进谱系追踪方法的研究表明，心肌细胞更新的唯一来源源自现存的心肌；因此，增加现有成年心肌细胞的增殖仍然是心脏再生的主要治疗方法。在本研究中，我们研究了抑制细胞周期抑制剂 Rb1 和 Meis2 以促进成年心肌细胞重新进入细胞周期的重要性。
体外实验采用小干扰 RNA 介导的 Rb1 和 Meis2 同时敲低，作用于从 12 周龄 Fischer 大鼠分离的成年大鼠心肌细胞和人诱导多能干细胞衍生的心肌细胞，结果显示细胞数量显著增加，细胞体积减小，单核心肌细胞增多。在体内，采用水凝胶为基础的递送方法，在心肌梗死后递送小干扰 RNA 介导的 Rb1 和 Meis2 沉默。免疫荧光成像分析显示，成年心肌细胞中的增殖标志物 5-乙炔基-2'-脱氧尿苷、PH3、KI67 和 Aurora B 显著增加，细胞存活率提高，梗死周围血管生成得到额外增强。总的来说，这种干预导致心肌梗死后梗死面积减小和心功能改善。
通过抑制 Rb1 和 Meis2 抑制成年心肌细胞中的衰老诱导途径，可导致明显的心肌细胞增殖，并在缺血性损伤中增加心脏功能的保护。
