Abstract 5135: Carbon Monoxide Promotes Neovascularization After Myocardial Infarction by Modulating the Expression of Angiogenic Cytokines and Growth Factors
Carbon monoxide is a biologically active molecule produced endogenously by heme oxygenase-1 (HO-1). Many of the beneficial properties of HO-1 are mediated by CO, but the role of CO in cardiac regeneration has not been studied earlier. Male Wistar rats were given the direct CO-donor methylene chloride (MC, 500 mg/kg, po, −3h, n=60). Control animals received no pretreatment (n=60). Rats were subjected to LAD ligation or sham-operation and sacrificed at 1 day, 3 days, 1 week and 4 weeks after ligation. Cardiac regeneration was assessed by immunohistochemistry and confocal microscopy. Stem cell and angiogenesis related gene expression was studied using real-time RT-PCR arrays. Compared to control hearts, CO significantly increased the accumulation of c-kit+/sca-1−/CD34− cells into the infarct area at weeks 1 (0.47±0.1 vs. 0.18±0.06 c-kit+ cells/mm2, p<0.05) and 4 (12.4±6.8 vs. 0.14±0.06 c-kit+ cells/mm2, p<0.001) post-MI. A substantial part of these c-kit+ cells (41%) were positive for the smooth muscle transcription factor GATA6 whereas only few Ets-1+ endothelial lineage committed cells were found. CO also increased vascular density in the infarct area at week 4 (395±24 vs. 306±25 α-SMA+ vessels/mm2, p<0.05). Interestingly, the number of large arteries was most significantly increased (7.1±0.6 vs. 4.8±0.4 α-SMA+ vessels/mm2, p<0.01). However, CO had no effect on capillary density. In the PCR array analysis, significantly increased expression of angiogenic cytokines and growth factors, including SDF-1, Hif-1α, HGF, IGF-1, IL6 and CXCL2, was found in the infarct areas of CO-donor pretreated hearts compared to control MI hearts (p<0.05). In conclusion, CO upregulates the expression of angiogenic cytokines and growth factors, thereby activating c-kit+ stem cells and promoting neovascularization in the infarcted hearts.