Abstract 5373: Potency and Mechanism of Bone Marrow Cells-Induced Cardioprotection
Previously we have shown that bone marrow cells (BMCs) have a strong cardioprotective effect. Here we have investigated the potency of this action and the underlying mechanism. BMCs and the right atrial appendage were obtained from patients undergoing elective cardiac surgery. To elucidate the cardioprotective potency of BMCs, cells at a dose of 10x106 were co-incubated with muscles for 10, 20, 30min before 90min ischemia/120min reoxygenation at 37°C and compared to the beneficial effect of ischemic preconditioning (IP), induced by 5min ischemia/5min reoxygenation. Tissue injury was assessed by creatine kinase (CK) released into the media during the reoxygenation period (IU/mg wet wt), and cell necrosis and apoptosis was determined by propidium iodide and TUNEL (% of aerobic control). Maximal reduction in CK release and cell necrosis and apoptosis was obtained with 30min co-incubation of BMCs with the muscles (0.27±0.10, 4.46±1.44% and 2.45±0.44% vs 1.37±0.22, 14.33±1.76% and 8.38±1.13% in control, respectively; p<0.05), an effect that was as potent as IP. To examine whether the cardioprotection of BMCs is induced by a paracrine effect, the media obtained from BMCs (10x106 cells) after 30min in incubation was used to condition the muscles for another 30min before ischemia. This study showed that both BMCs and the conditioned media were equally effective in the reduction of CK (0.42±0.10 and 0.48±0.06 vs 1.26±0.22 in control; p<0.05) and cell necrosis (3.70±1.24% and 2.04±1.26% vs 12.98±1.99% in control; p<0.05) and apoptosis (1.72±0.56% and 1.24±0.58% vs 8.56±0.94% in control; p<0.05). Finally, to investigate whether cardioprotection by BMCs is mediated via IGF-1R, the selective inhibitor PQ401 was used at different concentrations (0, 1.5, 15, 150ng/ml) together with the conditioned media. CK release and cell necrosis and apoptosis obtained with the conditioned media was completely abolished at the highest concentration of the IFG-1R inhibitor used (1.24±0.17, 13.19±0.84% and 7.18±1.54% vs 0.36±0.08, 1.29±0.75% and 1.49±0.63% in control; p<0.05). In conclusion, the cardioprotection induced by BMCs is as potent as IP, an action that is elicited by a secreted factor(s) present in the conditioned media and mediated via IGF-1R.