Abstract 5138: Secretoneurin Therapy Improves Cardiac Function in a Model of Myocardial Infarction in-vivo and Induces Angiogenesis and VEGF Expression in Cardiac Cells in-vitro
Introduction The angiogenic neuropeptide Secretoneurin (SN) is upregulated by hypoxia in several tissues like neurones and skeletal muscle cells and SN gene therapy restores tissue integrity, function and perfusion in the mouse hind-limb ischemia model by induction of angiogenesis, arteriogenesis and vasculogenesis. We therefore hypothesized that this cytokine might also affect function of cardiac cells and exert beneficial effects in a rat model of myocardial infarction (MI).
Results To investigate the effect of SN in vitro, a matrigel assay using human coronary artery endothelial cells (HCAEC) in the absence or presence of different concentrations of SN was performed. SN dose dependently induced angiogenesis in vitro with a maximum effect at 1ng/ml (rel. capillary tube formation 2.06+/−0.15; n=4; p<0.001 vs. Ctr.). A specific SN antibody abolished the observed effect (rel. cap. tube form. 1.05+/−0.14; n=4; p<0.01 vs. SN). Western Blot analysis of HCAEC extracts revealed stimulation of ERK1/2 by SN 10ng/ml indicating activation of this signal transduction pathway. PCR analysis of hypoxic human cardiac myocytes showed no effect on the expression of SN (in contrast to skeletal myocytes) but stimulation of this cell line with SN 100ng/ml lead to an upregulation of VEGF mRNA after 12 hours. In an acute MI model in rats, SN gene therapy was performed by injecting 500ug plasmid intramyocardially 10 min after LAD ligation. GFP plasmid was used as control. Left ventricular function was evaluated post-operatively and on day 14 and 28 after LAD ligation by echocardiography (ejection fraction, EF) and fractional area change (FAC) was measured using magnetic resonance imaging. On day 28 SN treated rats showed a significant better outcome with improved EF (75% for SN vs. 44% for Ctr, n=5; p<0.05) and improved FAC (0.59 for SN and 0.46 for Ctr, n=5; p<0.05).
Conclusion In vitro data for SN on cardiac cells suggest induction of angiogenesis and upregulation of VEGF. In vivo, SN gene therapy significantly improved left ventricular function in the rat MI model. Future studies will have to clarify if beneficial effects of SN in vivo are mediated by VEGF. These findings suggest that SN gene therapy might be a promising new therapeutic agent to improve ischemic cardiac dysfunction.