TY - JOUR AU - Koivumäki, Jussi T. AU - Clark, Robert B. AU - Belke, Darrell AU - Kondo, Colleen AU - Fedak, Paul W. M. AU - Maleckar, Mary M. C. AU - Giles, Wayne R. PY - 2014 M3 - Original Research TI - Na+ current expression in human atrial myofibroblasts: identity and functional roles JO - Frontiers in Physiology UR - https://www.frontiersin.org/articles/10.3389/fphys.2014.00275 VL - 5 SN - 1664-042X N2 - In the mammalian heart fibroblasts have important functional roles in both healthy conditions and diseased states. During pathophysiological challenges, a closely related myofibroblast cell population emerges, and can have distinct, significant roles. Recently, it has been reported that human atrial myofibroblasts can express a Na+ current, INa. Some of the biophysical properties and molecular features suggest that this INa is due to expression of Nav 1.5, the same Na+ channel α subunit that generates the predominant INa in myocytes from adult mammalian heart. In principle, expression of Nav 1.5 could give rise to regenerative action potentials in the fibroblasts/myofibroblasts. This would suggest an active as opposed to passive role for fibroblasts/myofibroblasts in both the “trigger” and the “substrate” components of cardiac rhythm disturbances. Our goals in this preliminary study were: (i) to confirm and extend the electrophysiological characterization of INa in a human atrial fibroblast/myofibroblast cell population maintained in conventional 2-D tissue culture; (ii) to identify key molecular properties of the α and β subunits of these Na+ channel(s); (iii) to define the biophysical and pharmacological properties of this INa; (iv) to integrate the available multi-disciplinary data, and attempt to illustrate its functional consequences, using a mathematical model in which the human atrial myocyte is coupled via connexins to fixed numbers of fibroblasts/myofibroblasts in a syncytial arrangement. Our experimental findings confirm that a significant fraction (approximately 40–50%) of these human atrial myofibroblasts can express INa. However, our data suggest that INa may be generated by a combination of Nav 1.9, Nav 1.2, and Nav 1.5. Our results, when complemented with mathematical modeling, provide a background for re-evaluating pharmacological management of supraventricular rhythm disorders, e.g., persistent atrial fibrillation. ER -