Abstract 2096: Impact of PI3/Akt Pathway on Production of Vascular Endothelial Growth Factor and Associated Myocardial Salvage by Mesenchymal Stem Cell wtih Transient Overexpression of Heme Oxygenase-1
Background: Mesenchymal stem cell (MSC) with transient overexpression of Heme Oxygenase-1 (HO-1) has a potential for salvaging ischemic myocardial injury through its anti-oxidative and -apoptotic effects. However, few data exist regarding the underlying mechanism of these effects in terms of cytokine production. Therefore, we examined the impact of Akt pathway on MSCs and HO-1 MSCs-derived cytokine production, and evaluated these effects on cell apoptosis in vivo.
Methods and Results: We engineered a protective gene modification in which human HO-1 gene was transfected into MSC using the lipofection method. When MSCs and HO-1MSCs were exposed to serum deprivation/hypoxia or H2O2, HO-1MSCs exhibited resistance to cell apoptosis in comparison with MSCs (17 ± 2% vs 30 ± 5%, mean ± SD, p<0.05), and were markedly resistant to cell death at 400μM of H2O2 (2 ± 2% vs. 32 ± 3%, p<0.05). Under the oxidative stress, VEGF production was greater in HO-1MSCs (130 ± 17 pg/ml) by 2.1 fold than that in MSCs (63 ± 10 pg/ml). Interestingly, pretreatment of PI3/Akt pathway inhibitors such as LY294002 (50μM) and wortmanin (100nM) decreased VEGF production by 78.3 ± 5.7% and 70.2 ± 1.5%, respectively (p<0.001), suggesting the fundamental codependence between HO-1 and Akt in VEGF production. In rat infarction model where MSCs and HO-1MSCs (5×106 ± 0.4 ×106 cells/rat) were transplanted to peri-infarct area, the number of TUNEL-positive cells was significantly lower in HO-1MSCs than those with MSCs (12.1 ± 3.3 cells/field vs. 26.5 ± 8.5, n=8, p<0.05) on 4th day after transplantation. Under these conditions, increased capillary density associated with decreased infarction size was observed in HO-1MSCs group (1415 ± 150/mm2 with 21.5 ± 2.3%) compared with MSCs (1215 ± 137/mm2 with 28.2 ± 2.3%, n=10, p<0.05).
Conclusion. These results demonstrate that enhanced anti-oxidative and -apoptosis effects of HO-1MSCs associated with increased VEGF production can be modulated by PI3/Akt pathway. This novel interaction between Akt and HO-1 in cytoprotective systems may provide the rationale for development of therapeutic strategies for ischemic myocardial injury.