Stem cell therapy is a promising therapeutic option to treat patients after myocardial infarction. However, the intramyocardial administration of large amounts of stem cells might generate a proarrhythmic substrate. Proarrhythmic effects can be explained by electrotonic and/or paracrine mechanisms. The narrow therapeutic time window for cell therapy and the presence of comorbidities limit the application of autologous cell therapy. The use of allogeneic or xenogeneic stem cells is a potential alternative to autologous cells, but differences in the proarrhythmic effects of adipose-derived stromal cells (ADSCs) across species are unknown. Using microelectrode arrays and microelectrode recordings, we obtained local unipolar electrograms and action potentials from monolayers of neonatal rat ventricular myocytes (NRVMs) that were cocultured with rat, human, or pig ADSCs (rADSCs, hADSCs, pADSCs, respectively). Monolayers of NRVMs were cultured in the respective conditioned medium to investigate paracrine effects. We observed significant conduction slowing in all cardiomyocyte cultures containing ADSCs, independent of species used (p < .01). All cocultures were depolarized compared with controls (p < .01). Only conditioned medium taken from cocultures with pADSCs and applied to NRVM monolayers demonstrated similar electrophysiological changes as the corresponding cocultures. We have shown that independent of species used, ADSCs cause conduction slowing in monolayers of NRVMs. In addition, pADSCs exert conduction slowing mainly by a paracrine effect, whereas the influence on conduction by hADSCs and rADSCs is preferentially by electrotonic interaction.
SIGNIFICANCE: Cell-based therapy is a promising option to treat patients after myocardial infarction. Although cell-based therapy may help replace infarcted heart tissue by functional tissue, it has some limitations. First, it may cause life-threatening arrhythmias. Slow conduction facilitates arrhythmias induction. Second, cells derived from and administered to the same patients may be affected by age and disease. Therefore, cells from other patients or other species may be used. This study shows that application of stromal cells caused conduction slowing in cardiomyocyte monolayers, irrespective of the specific origin of the cells, but that the conduction slowing is conferred through soluble factors or through coupling between fat-derived cells and cardiac myocytes in a species-dependent manner.