Abstract 459: Hepatocyte Growth Factor, but not Vascular Endothelial Growth Factor, Attenuated Ang II-induced Senescence in EPC through Anti-Oxidative Stress Effect by Inhibiting Rac1 Activation.
[Background] We had demonstrated therapeutic angiogenesis by hepatocyte growth factor (HGF) in several animal models. On the other hand, bone marrow-derived circulating endothelial progenitor cells (EPC) are also used to enhance angiogenesis after tissue ischemia. However, cardiovascular risk factors significantly decreased EPC number, and promoted EPC senescence. Thus, in this study, we investigated the potential effects of HGF on Ang II-induced senescence in EPC.
[Methods and Results] EPC were isolated from human peripheral blood. Ang II (100nM) significantly decreased the number of EPC and stimulated senescence as determined by acidic beta-galactosidase staining, while HGF (100ng/ml) as well as VEGF (100ng/ml) significantly stimulated the proliferation and in-corporation of EPC into tube like structure. However, although HGF significantly attenuated the senescence of EPC induced by Ang II, but not VEGF, (C 18.4±1.4 %, AII 38.9±5.1 %, AII+VEGF 44.2±6.3 %, AII+HGF 34.1±5.2%*, *P<0.01 vs AII+VEGF). To elucidate the mechanism, we measured oxidative stress. Although Ang II increased the oxidative stress as assessed by O− by DHE staining and the expression of gp91phox mRNA by RT-PCR, the increase in oxidative stress was significantly attenuated by HGF (P<0.01), but not VEGF. Inhibitory effect of HGF on oxidative stress was due to the significant inhibition of translocation of GTP-rac1 (P<0.01). To confirm this observation, we employed hind limb ischemia model in cardiac specific over-expression of HGF-Tg mice in which blood HGF protein was significantly increased. We administered Ang II (0.7mg/kg/day) into HGF-Tg and WT mice. Blood flow ratio as evaluated by Laser Doppler Image in HGF-Tg mice was significantly increased as compared to that wild type (HGF-Tg 0.47±0.07 WT 0.33±0.09, P<0.05). Of importance, Ang II infusion significantly decreased EPC number and stimulated senescence in wild type mice, whereas these changes were attenuated in HGF-Tg mice (P<0.01).
[Conclusion] HGF, but not VEGF, attenuated Ang II-induced the decrease in number and senescence of EPC through anti-oxidative stress by inhibiting Rac1 activation. Enhancement of the number of EPC and prevention of senescence by HGF might be contributed to angiogenesis.