Local Gene Transfer with Nerve Growth Factor Promotes Reparative Neovascularisation in a Mouse Model of Myocardial Infarction

Abstract

Although neurotrophins (NTs) were initially considered for their important actions on neuronal regeneration and survival, recent studies showed their involvement in reparative neovascularisation. Our group previously demonstrated that the NT Nerve Growth Factor (NGF) stimulates angiogenesis and arteriogenesis in a murine model of peripheral ischemia and diabetic skin wounds. The aim of my PhD studies was to evaluate the possible therapeutic effect of NGF in a mouse model of myocardial infarction (MI). We investigated whether NGF induces reparative neovascularisation after MI and promotes the survival of cardiomyocytes (CM) and endothelial cells (EC). We also examined the impact of NGF on EPC migration and proliferation, two relevant mechanism for vasculogenesis. Anaesthetized CD1 mice underwent MI by permanent occlusion of left descending coronary artery and were injected into the MI border zone with a plasmid carrying the human NGF gene (p.NGF). Control animals were treated with an empty vector (p.Null). RT-PCR documented the presence of transgenic NGF mRNA into the infarcted heart at 3 days after MI. Histologic analyses indicated that NGF over-expression stimulated capillary growth in the peri-infarct area at two weeks after MI (P<0.05 vs. p.Null) and in addition decreased the number of TUNEL-positive apoptotic EC and CM (P<0.05 vs. p.Null). The pro-survival action of NGF was also demonstrated in rat neonatal CM (RNCM). NGF over-expression reduced RNCM apoptosis after hypoxia/reoxygenation and Angiotensin II apoptosis assays. Finally, since bone marrow-derived EPC have been shown to regenerate the myocardium by enhancing neovascularisation, we also investigated the influence of NGF on cultured EPC migration and proliferation. We found that both migration and proliferation of EPC were improved after NGF stimulation, thus favouring the hypothesis that NGF may positively impact on vasculogenesis. In conclusion, our results suggest that intra-myocardial NGF induces reparative neovascularisation by promoting both angiogenesis and vasculogenesis and by inhibiting the apoptotic death of resident EC. In perspective, NGF may represent a potential tool to induce therapeutic angiogenesis in the setting of MI.