iPS technology as a tool to investigate atrial fibrillation.

Atrial fibrillation (AF) is the most common arrhythmic disorder in adults, with a prevalence ranging around 0.5-2% in the general population. Atrial fibrillation is characterized by rapid and irregular activation of the atria, loss of coordinated atrial contraction thus resulting in reduced ventricular filling and blood stasis in the atria, and finally leading to heart failure and thromboembolic stroke. Several therapeutic strategies are currently available, either pharmacological or ablative, albeit the rate of success in terms of sinus rhythm restoration may consistently vary among patients. AF has traditionally been described as a multifactorial sporadic disease; however some hints about AF hereditability have recently been issued from epidemiological studies.Therefore in vitro AF models to identify the genetic basis, to examine cell differentiation, to characterize interactions of cells belonging to cardiovascular lineage, are urgently needed in order to improve the comprehension of the pathophysiological basis of AF. We began to characterize a familial group with continuous AF who were scheduled to undergo surgical ablation following failed pharmacological treatment. Screening for mutation of the most common genes associated to AF (KCNQ1,KCNH2, KCNE1, KCNE2, and SCN5A) did not show any modification. We are now in process of sequencing some other recently identified putative candidate (MiRP1, CAV3, and HCN4), but a more extensive analysis needs to be carried out. In order to provide a valuable experimental platform to model AF disease, primary cultures of dermal fibroblasts were established from all individuals. At low passage number, cells were induced to pluripotency by retroviral infection with the classical set of factors (OCT4, KLF4, SOX2 and c-MYC). Then, we isolated 2-4 independent lines per individual of AF-specific induced pluripotent stem cells (iPSC). We have begun to characterize the pluripotency state of our colonies, by colony morphology and growth dynamics, alkaline phosphatase staining, expression of pluripotency associated transcription factors (OCT4, SOX2, NANOG, REX1), surface markers (SSEA3, SSEA4, TRA1-60, TRA1-81), and silencing of retroviral transgenes. Following the assessment of pluripotency, we aim to differentiate AF-derived iPSC into cells of the cardiovascular lineage, such as cardiomyocytes and endothelial cells. We believe that the model we are developing will help us in clarifying the molecular basis of AF.