Telocytes express ANO ‐1‐encoded chloride channels in canine ventricular myocardium

It is unknown if ANO ‐1 is expressed in the heart, though the presence of a calcium‐activated chloride current has been proposed to mediate some cardiac dysrhythmias. Furthermore, a specific cell type termed telocytes, morphologically mimicking Cajal cells which use ANO ‐1 to modulate their pacemaker activity in the gut, have been described in the heart. We therefore sought to determine whether this channel is expressed in the canine heart. Methods Myocardium was sampled from the ventricles of five canines. Sections were labeled with anti‐Kit and anti‐ ANO ‐1 antibodies. Slides were reviewed by four investigators looking at cell morphology, distribution, and co‐localization. Identification of telocytes was based on criteria including morphology, Kit positivity (+), and ANO ‐1 positivity (+). Results Clusters of cells meeting criteria for telocytes were seen in the epicardium, sub‐epicardium, and mid‐myocardium. A small subset of cells that were morphologically similar to myocytes was ANO ‐1 (+) but Kit (−). In total, three different cell classes were found: (i) Kit (+), ANO ‐1 (+) cells with the appearance of telocytes; (ii) Kit (+), ANO ‐1 (−) cells; and (iii) Kit (−), ANO ‐1 (+) cells with the morphologic appearance of cardiac myocytes. Conclusions Telocytes are present in the canine ventricle and express ANO ‐1. These data merit further study to elucidate the functional expression of these channels in the heart and whether they may be targets for cardiac arrhythmias.