AGT and atrial fibrillation: Biologically active compounds, namely, angiotensin II, retinoic acid, EGCG, vitamin C, and their combinations with angiotensin II, are able to induce alterations in AF-MSCs at the phenotypic, genetic, protein, metabolic, and epigenetic levels to a different extent leading to the formation of cardiomyocyte progenitors that may become functional heart cells upon maturation in vitro or in vivo.