Li, Fan

Cardiovascular disease causes the largest number of deaths across the world. The weak regenerative ability of adult hearts originates from limited cell proliferation and polyploidization of postnatal cardiomyocytes, which severely hinders tissue repair after myocardial injury. Fetal development represents a critical window during which maternal physiological and metabolic status can shape long-term offspring cardiac structure and function. Maternal exercise represents a safe nonpharmacological prenatal intervention that confers long-term benefits to offspring health. Available evidence indicates that maternal exercise enhances placental apelin secretion and elevates α-ketoglutarate (α-KG) levels in fetal brown adipose tissue, liver, and skeletal muscle. The apelin and α-KG signaling cascade participates in epigenetic regulation and confers protective effects on offspring metabolic health. Independent animal experiments have further validated that supplementation with either apelin or α-KG alleviates myocardial infarction (MI)-induced cardiac injury in adult mice, with α-KG showing direct evidence of reactivating cardiomyocyte proliferation. Nevertheless, it remains poorly elucidated whether maternal exercise could modulate fetal cardiomyocyte proliferative capacity in offspring through apelin- or α-KG-associated signaling. This narrative review integrates current evidence and proposes a testable framework in which maternal exercise influences fetal cardiac growth and regenerative potential through placental, metabolic, and epigenetic signaling. Because direct evidence remains limited, this model should be regarded as a hypothesis that requires further experimental validation.

The regulation of the cardiomyocyte cell cycle is central to understanding heart regeneration. In adult mammals, cardiomyocytes withdraw from the cell cycle, limiting their ability to proliferate and repair heart tissue after injury. This process is controlled by intrinsic genetic programs and extrinsic signals, which together restrict the regenerative response in mature hearts. Understanding the mechanisms that regulate cardiomyocyte cell cycle activity is therefore critical for advancing cardiac regenerative medicine. In this review, we provide a comparative and integrated overview of cardiomyocyte cell cycle regulation in lower vertebrates and mammals, and discuss the major intrinsic factors that govern this process, including cyclin/CDK pathways, transcription factors and co-activators, oxygen and metabolic regulation, and epigenetic mechanisms. We also review the influence of hormones and growth factors, as well as the supportive roles of nonmyocyte populations in heart regeneration. By integrating findings across species, developmental stages, and regulatory levels, these findings highlight the complex regulatory network controlling cardiomyocyte proliferation and provide insight into potential therapeutic strategies for stimulating cardiac repair in the adult mammalian heart.

Acute atrial ischemia is a well-known cause of postoperative atrial fibrillation (POAF). However, mechanisms through which ischemia contributes to the development of POAF are not well understood. In this study, ex vivo Langendorff perfusion was used to induce acute ischemia/reperfusion in the heart to mimic POAF. Inducibility of atrial fibrillation (AF) was evaluated using programmed electrical stimulation and verified with open-atrium optical mapping. Compared with the control group without ischemia, 25 minutes of ischemia substantially increased the incidence of AF. The right atrium was more susceptible to AF than the left atrium. Administering insulin for 30 minutes before ischemia and during reperfusion with 25 minutes of ischemia greatly reduced the vulnerability to AF. However, insulin treatment during reperfusion only did not show substantial benefits against AF. Optical mapping studies showed that insulin mitigated ischemia-induced abnormal electrophysiology, including shortened action potential duration and effective refractory period, slowed conduction velocity, increased conduction heterogeneity, and altered calcium transients. In conclusion, insulin reduced the risk of acute ischemia/reperfusion–induced AF via improving the electrophysiology and calcium handling of atrial cardiomyocytes, which provides a potential therapy for POAF.