Summary
We are interested in pacemaker activity in visceral smooth muscle tissues. Recently, we have concentrated our studies on specialized interstitial cells, of which there are multiple forms in smooth muscles. Recently, using a reporter strain of mice that drive expression of eGFP from the endogenous promoter for Pdgfra, that is expressed in a sub-population of interstitial cells in the GI and urinary tracts, we found a dense population of interstitial cells within cardiac tissues that occupied all areas of the heart including the SAN. A significant sub-population of these cells, labeled with eGFP, express the classical fibroblast marker, vimentin and are referred to as PDGFR+ cardiac fibroblast-like cells (CFC). The same population of CFC are labeled by PDGFR antibodies in the primate heart. Thus, these PDGFR+ cells correspond to CFCs of the heart, which form gap junctions with myocytes and have been proposed to have a role in the development of atrial fibrillation. The data from PDGFR+ cells allow us to understand the automaticity and phenotype of PDGFR+ CFCs in the SAN and atrium and develop new hypotheses and possibly novel therapeutic targets for cardiac pacemaker deficiencies.