Angiogenesis Induced by hVEGF165 Gene Controlled by Hypoxic Response Elements in Rabbit Ischemia Myocardium

Abstract

Hypoxic response element (HRE) offers satisfactory control over expression of hVEGF(165) in cell levels. However, the characteristics of regenerated blood vessels induced by long-term expression of transferred hVEGF(165) under control of HRE in vivo remain unknown. This study aims to investigate the effect of HRE on control of long-term expression of rAAV-delivered hVEGF(165) gene to ischemic myocardium and evaluate characteristics of angiogenesis induced by hVEGF(165) in vivo. Rabbit ischemic heart models were established surgically, rAAV-9HRE-hVEGF(165) was transfected to ischemia hearts subjected to 12 week ischemia. Molecular biological and immunohistochemistry were employed to determine expressions of HIF-1alpha and hVEGF(165). Microvessel densities of CD31(+) and alpha-SMA(+) regenerated vessels were also evaluated. Expressions of both hVEGF(165) mRNA and protein were upregulated following over-expression of endogenous HIF-1alpha early after ischemia, peaked at 4-6 weeks post-MI, declined, and approached pre-ischemia level at the end of 12 weeks of ischemia (P < 0.01). The significantly upregulated CD31 in hVEGF(165)-treated hearts presented from 8 to 12 weeks of ischemia compared with the control (P < 0.01). However, alpha-SMA expression was rapidly downregulated after ischemia and remained lower than the control level by the end of 12 weeks post-MI (P < 0.01). Overexpression of hVEGF(165) controlled by HIF-1alpha-HRE system shows a stably regional angiogenic efficacy in vivo. But, VEGF, as an early angiogenic cytokine, is inadequate for mediating histologically mature vessels in ischemia myocardium.