MULTIMODAL ASSESSMENT OF HEPATOCYTE GROWTH FACTOR ANGIOGENIC GENE THERAPY IN RAT MYOCARDIAL INFARCT MODEL. 

Hepatocyte growth factor (HGF) has been shown to have a potent angiogenic activity in vitro, however, the in vivo therapeutic effects of angiogenic gene therapy using HGF gene in ischemic heart disease remains controversial. The aim of this study was to investigate the effects of HGF gene therapy in rat myocardial infarct model precisely with multimodal imaging including cine MRI, SPECT/CT, and two-photon excitation fluorescent microscopy (TPEFM).Human sodium-iodide symporter (hNIS) gene was used as a radionuclide reporter gene. Recombinant adenoviruses expressing both HGF and hNIS genes comparably driven by dual constitutive cytomegalovirus promoters (Ad-CMV-HGF-CMV-hNIS; Treatment) and hNIS gene only (Ad-CMV-hNIS; Control) were constructed. Wister rats (10 week-old male) received permanent ligation of the left anterior descending artery, followed by injection of Treatment or Control vector into peri-infarct regions of the left ventricular myocardium. On Day 1, cine MRI was performed using a 7.0T MRI (Bruker Biospin BGA-1) to measure end-diastolic volume (EDV) and ejection fraction (EF). On Days 2 and 4, SPECT/CT images of therapeutic gene expression and myocardial perfusion were obtained with 99mTcO4- and 99mTc-tetrofosmin using a small animal SPECT/CT (Gamma Medica-Ideas FX). Nine (5 Treatment and 4 Control) rats showing similar infarct size and similar gene expression levels were followed for 10 weeks to repeat cine MRI and SPECT/CT. Afterwards, excised hearts were processed for immunohistochemistry with alpha-SMA and CD31 to measure small blood vessels and capillary density, and TPEFM to visualize the three-dimensional microvasculature.The repeated cine MRI demonstrated significantly increased EDV in both Treatment and Control rats without significant difference between the groups. The infarct size was similar after follow-up. Capillary density defined by immunohistochemistry was significantly higher in Treatment rats, while small blood vessels were comparable between the groups. TPEFM revealed very thin (≈2µm) irregular vessels increased at peri-infarct regions of Treated hearts.TPEFM provided direct evidence that sole HGF gene therapy could induce exclusively immature dysfunctional vessels, which explains other results that increased capillary density didn\u27t lead to cardiac functional recovery. This may contribute to solve the gap between promising results from basic researches and lack in decisive therapeutic effects in clinical researches.World Molecular Imaging Congress 201