Effects of transplanted myoblasts transfected with human growth hormone gene on improvement of ventricular function of rats

Background Cell transplantation for myocardial repair is limited by early cell death. Gene therapy with human growth hormone （hGH） has been shown to promote angiogensis and attenuate apoptosis in the experimental animal. This study was conducted to explore the effects of myoblast-based hGH gene therapy on heart function restoration and angiogenesis after myocardial infarction, and to compare the differences between myoblast-based hGH gene therapy and myoblast therapy. Methods Myoblasts were isolated from several SD rats, cultured, purified, and transfected with plasmid pLghGHSN and pLgGFPSN. Radioimmunoassay （RIA） was used to detect the expression of hGH in these myoblasts. SD rats underwent the ligation of the left anterior descending coronary artery so as to establish a heart ischemia model. Thirty surviving rats that underwent ligation were randomly divided into 3 equal groups 2 weeks after left coronary artery occlusion： pLghGHSN group received myoblast infected with hGH gene transplantation; pLgGFPSN group received myoblast infected with GFP gene transplantation; control group： received cultured medium only. Four weeks after the injection the surviving rat underwent evaluation of cardiac function by echocardiography. The rats were killed and ventricular samples were undergone immunohistochemistry with hematoxylin-eosin and factor Ⅷ. Cryosection was analyzed by fluorescence microscopy to examine the expression of green fluorescent protein. Reverse transcriptase-polymerase chain reaction （RT-PCR） was used to examine the mRNA expression of vascular endothelial growth factor （VEGF）, bax and Bcl-2. hGH expression in myocardium was examined by Western blot. Results Myoblast can be successfully isolated, cultured and transfected. The expression of hGH in transfected myoblast was demonstrated with RIA. Four weeks after therapy, the cardiac function was improved significantly in pLghGHSN group and pLgGFPSN group. Fractional shortening （FS） and ejection fraction （EF） in pLghGHSN group were elevated significantly compared with pLgGFPSN group and control group after therapy （FS： 36.9±5.3 vs 29.5±3.5, 21.8±2.9; EF： 56.9±4.3 vs 47.1±3.6, 38.4±4.8, P〈0.05）. Left ventricular end-diastolic dimension （LVEDD） and heart infracted size in pLghGHSN group were decreased significantly compared with pLgGFPSN group and control group after therapy （LVEDD： 5.9±0.3 vs 6.8±0.2, 8.6±0.3; heart infracted size： （34.5±4.2）% vs （40.0±3.9）%, （46.1±3.8）%, P〈0.05）; Green fluorescence was