A complete heart regeneration model with inflammation as a key component

The neonatal mice myocardial infarction (MI) has been established as one of the heart regeneration models. However, the role of inflammation in this model is still unclear. We sought to systematically evaluate this model and explore the role of inflammation in it. Postnatal day 1 (P1) or day 7 (P7) mice were conducted left anterior descending coronary artery (LAD) ligation. Cardiac damage, repair, and regeneration were examined by histology and echocardiography. Inflammation was detected by heart section hematoxylin and eosin (HE) staining and tissue qPCR. Dexamethasone (Dex) was used to inhibit inflammation and its effects on heart regeneration were evaluated. Two days after P1 mice MI, cardiomyocytes in ischemia area died and heart function decreased. Then surrounding cardiomyocytes proliferated to repair the injury. At day 28 after MI, hearts were almost fully regenerated with a little fibrosis existed. In contrary, P7 mice MI resulted in thinning and fibrosis of the ventricular wall. Inflammation was induced by LAD ligation after P1 mice MI and dynamic changed during the process. Inhibition of inflammation by Dex impaired heart regeneration. These demonstrated that cardiomyocytes death and heart regeneration occurred in this model and inflammation might play a crucial role in it. Modulating inflammation may provide a promising therapeutic strategy to support heart regeneration.