Figure 4.

Potential role of Thymosin β4 in cardiomyocyte differentiation from non- myocytes. In adult mouse hearts, Wt1 is absent or expressed at low levels in epicardial cells. Epicardial cells re-express Wt1 after infarction, proliferate, and give rise to mesenchymal cells expressing smooth muscle and fibroblast cell markers, but never differentiate into cardiomyocytes (Zhou et al 2011). With Thymosin β4 injections prior to the injury, more epicardial cells induce Wt1 expression after MI, some of which coexpress cardiac progenitor markers such as Islet1. Evidence suggests that some of these activated epicardial cells transdifferentiate to cardiomyocytes (Smart et al 2011).