Model depicting epicardial cell reactivation and expression of transcription factors, including Tcf21, Wt1, Tbx18, Snai1, and C/EBPβ, following myocardial infarction (MI) in the adult heart. Activated epicardial cells undergo EMT and invade the subepicardial space following MI. The ultimate fate of activated EPDCs and their ability to invade the myocardium in the infarcted heart has not yet been fully characterized. In the area of the infarct scar Tcf21, Wt1, Tbx18, and Scleraxis (Scx) also are expressed, and immune cells are present in the activated epicardium and fibrotic scar. Currently, it has not been reported whether epicardial transcription factors are activated in other forms of cardiac fibrosis. See text for details and references.