Inhibition of Senescence‐Associated Genes Rb1 and Meis2 in Adult Cardiomyocytes Results in Cell Cycle Reentry and Cardiac Repair Post–Myocardial Infarction

Abstract

BackgroundMyocardial 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 ResultsIn 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.ConclusionsSilencing 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.

Cardiac Stem Cell Therapy, Resident Progenitor Cells and the role of Cellular Signalling; a Review

“…Additionally, control injections of hydrogel alone without siRNAs still offered a small degree of cardio-protection, suggesting that intracardiac injection of biological materials following acute myocardial injury may have some small therapeutic benefits. The results of RT-PCR, Western Blot and immunohistochemical analysis together suggested a site-specific induction of CM cell cycle re-entry, keeping the potential low for off-site pathogenic effects such as unintended hyperplasia [23]. Previous attempts to induce re-entry of CMs into the cell cycle have resulted in heart dysfunction.…”

“…Suppressing cell cycle inhibitors may promote cardiomyocyte proliferation potential. Specifically, downregulating Retinoblastoma1 (Rb1) and Meis Homeobox 2 (Meis2), via small interfering (si)RNA's, induced proliferation of CMs in rats and human cell models and had a positive effect on heart health and improved wound healing [23].…”

Cell Senescence, Multiple Organelle Dysfunction and Atherosclerosis

“…Interestingly, Meis1, a senescence-associated gene, was shown to contribute to the regulation of hematopoietic stem cell metabolism and oxidant stress response, via the transcriptional regulation of hypoxia-inducible factors [ 41 ]. More recent studies revealed that silencing senescence-mediated pathways through inhibition of Meis2 and Rb1 in adult rat cardiomyocytes leads to cardiomyocyte proliferation and cardiac repair upon myocardial infarction [ 42 ]. In addition, FoxO3 was recently reported to mediate cardiac protection from oxidative stress, counteracting cardiac dysfunction, apoptosis and senescence in mice [ 43 ].…”

Catechin relieves hypoxia/reoxygenation‐induced myocardial cell apoptosis via down‐regulating lncRNA MIAT

“…Left ventricular ejection fraction (LVEF) = [(LVEDd 3 − LVESd 3 )/LVEDd 3 ] × 100%; Left ventricular fractional shortening (LVFS) = (LVEDd − LVESd)/LVEDd × 100% 26. LV end-systolic diameter (LVESd) and left ventricular end-diastolic diameter (LVEDd) were calculated using the PVAN analysis software (Millar Instruments).…”

“…LV end-systolic diameter (LVESd) and left ventricular end-diastolic diameter (LVEDd) were calculated using the PVAN analysis software (Millar Instruments). Left ventricular ejection fraction (LVEF) = [(LVEDd 3 − LVESd 3 )/LVEDd 3 ] × 100%; Left ventricular fractional shortening (LVFS) = (LVEDd − LVESd)/LVEDd × 100% 26.…”