Thymosin beta 4 treatment after myocardial infarction does not reprogram epicardial cells into cardiomyocytes

► Unlike TB4 treatment prior to MI, TB4 treatment after MI does not reprogram epicardial cells into cardiomyocytes. ► Epicardial cells treated with TB4 after MI adopt mesenchymal fibroblast fate. ► TB4 stimulates epicardial cells proliferation in vivo.