Recently, Gambini et al. analyzed the differentiation properties of cardiac mesenchymal progenitor cells (CMPCs, stromal cells positive for c-kit) deriving from patients with Atrial Fibrillation (AF), in order to establish the pro-fibrotic contribution of these cells in the pathogenesis of the disease, where atrial fibrosis has a critical role. This evidence concerns the gene KIT and atrial fibrillation.