[Stem Cell Studies 2012; 2:e1] [page 1] Analysis of pro-arrhythmiceffects induced by differentroutes of administration of bone marrow stem cells

There has been repeated concern that intramyocardial (i.m.) delivery of cells could cause ventricular arrhythmias. The aim of the study was to evaluate the pro-arrhythmic effects of bone marrow stem cell (BMSC) injection and compare different routes of administration. An ischemia reperfusion injury was induced in New Zealand rabbits by temporal ligation of anterior descending coro-nary artery. Homologous BMSCs were isolated, cultured and re-suspended for injection. We compared different routes of BMSC injections, intramyocardial (i.m.) versus intravenous (i.v.) administration of cells. A control group was treated with i.m. injections of saline. The hourly number of supra- and ventricular pre-mature contractions (VPCs), QT interval time and QTc time were recorded and calculated. At Day 7 after cell injections, VPCs were more fre-quent in the groups treated with i.m. BMSCs and i.m. saline compared with i.v. BMSCs (132 ±19; 54±14 and 34±9, respectively; P<0.01 within groups), whereas at Day 21 the number of VPCs was higher in the 2 groups treated with either i.m. or i.v. BMSCs compared with saline (96±23; 52±19 and 25±20, respectively; P<0.001 within groups). QTc time interval was prolonged during ischemia, and recovered in control and in the group treated with i.v. cells, whereas it remained longer in rabbits treated with i.m. BMSCs. These findings show that i.m. BMSC injections induced a high number of pre-arrhythmic events suggesting changes in cardiac electrophysiological properties. The i.v. administration of cells resulted in lower VPC beats and in a temporary QT prolongation. These results suggest that the combination of BMS cells and i.m. injections induced an elec-trical remodeling that contributed to the devel-opment of arrhythmias