[Effects of Exogenous Nerve Growth Factor on Late Reperfusion after Myocardial Infarction]

This study demonstrates that nerve growth factor (NGF) plays a protective role in myocardial infarction and early reperfusion by reducing the myocardial cell apoptosis and by improving ventricular remodeling and seeks to assess the effects and mechanisms of NGF on late reperfusion after myocardial infarction. The models of late reperfusion were established by ligating the left main coronary artery and then cutting the suture 2 hours after coronary artery ligation. The rats in NGF treatment group were injected 10 µL Ad-NGF (by constructing the adenovirus vector Ad-NGF containing NGF gene) at four locations around infarction. The rats in adenoviral vector (Adv) group were injected 10 µL adenoviral cector as the NGF group. The late reperfusion group and the sham group were given normal saline as above, and the sham group underwent thracotomy without coronary ligation. On the 3rd, 7th, 14th and 28th day after operation, we investigated the role of NGF on late reperfusion by recording cardiac structure and function with echocardiography, by examining the expression of NGF and VIII factor with immunohistochemical method, and by evaluating the myocardial cell apoptosis with terminal dUTP nick end-labeling method (TUNEL). We found that the NGF group had higher expression of NGF protein (P < 0.01) and lower apoptosis index (AI) (P < 0.01 or P < 0.05) compared to the late reperfusion group and Adv group on all time points. The NGF group had remarkably higher level of neovascularization compared to the late reperfusion group on the 14th day (P < 0.01) and the 28th day (P < 0.05). The NGF group also had higher LVEF and FS levels compared to the late reperfusion group on the 14th day (P = 0.006, P = 0.006) and on the 28th day (P = 0.000, P = 0.000). Whereas the NGF group had lower LVEDD, LVESD (P = 0.038, P = 0.000) and lower LVEDV, LVESV (P = 0.001, P = 0.000) on the 28th day compared to late reperfusion group. In this experiment, the NGF gene carried by adenovirus vector had been transfected and obviously increased the expression of NGF protein in NGF group. NGF may help postpone the myocardial remodeling and improve the heart function by promoting the myocardial neovascularization and inhibiting myocardial apoptosis.