Effects of myocardial transplantation of marrow mesenchymal stem cells transfected with vascular endothelial growth factor for the improvement of heart function and angiogenesis after myocardial infarction.

OBJECTIVE: To establish the transfection method of vascular endothelial growth factor (VEGF) gene into mesenchymal stem cells (MSCs), to investigate the effect of this gene-transfected MSCs for heart function restoration and angiogenesis after myocardial infarction, and to compare the therapeutic differences among cell therapy, gene therapy, and combined therapy.

METHODS: Ischemic heart models were constructed in inbred Wistar rats by ligation of the left anterior descending coronary artery. MSCs of Wistar rats were isolated by density gradient centrifugation and purified on the basis of their ability to adhere to plastic, and identified by checking the surface markers and their differentiation capacity, and then followed by transfection of pcDNA(3.1)-hVEGF(165) using the liposome-mediated method. The expression of hVEGF(165) in the transfected cells was detected by Enzyme-Linked Immunosorbent Assay, Reverse Transcription-Polymerase Chain Reaction (RT-PCR) and Western Blot Analysis. The ligated animals were randomly divided into four groups (12 in each) and, after 2 weeks, were injected at the heart infarct zone with hVEGF(165)-transfected MSCs (Combo group), MSCs (Cell group), liposome-hVEGF gene plasmid (Gene group), or medium (Control group). And other six ligated rats (without any injection) were used as Model-assessment group for the baseline heart infarcted size evaluation, and other 12 non-ligated rats (Non-ischemic group) were used as the normal control. Four weeks after the injection, the rats' cardiac function was measured by the Buxco system. Brdu and Troponin-T double labeling and factor VIII were identified by immunohistochemical staining to demonstrate the survival and differentiation of engrafted cells or to evaluate the angiogenesis in the injured heart area; heart infarcted size was calculated by Evan's blue staining. VEGF expression was evaluated by RT-PCR.

RESULTS: MSCs can be successfully isolated and cultured by density gradient centrifugation followed by adherence-separation. The cultured MSCs were CD34-, CD45-, CD44+ and SH+. They can differentiate into osteoblasts and adipocytes successfully. The expression of hVEGF(165) in the transfected MSCs was demonstrated with Enzyme-Linked Immunosorbent Assay, RT-PCR and Western Blot Assay. Four weeks after the cells were transplanted, among all groups but the Non-ischemic group, the Combo group had the smallest heart infarcted size and the best heart function. The capillary density of the Combo group was significantly greater than those of both Cell and Control groups. The heart infarcted size, heart function and capillary density of both Cell and Gene groups were similar with each other and smaller, better and greater than those of the Control group, respectively. Brdu and Troponin-T double staining detected a varied increase in the number of survived cardiomyocytes at the heart infarcted area, some of which were double stain positive. RT-PCR showed that the hVEGF(165) gene was expressed in the Combo and Gene groups, and that the former was higher than the latter.

CONCLUSIONS: Eukaryotic expression vector pcDNA(3.1)-hVEGF(165) can effectively be expressed in MSCs. Transplantation of VEGF gene-transfected MSCs can bring better improvement in myocardial perfusion and in restoration of heart function than either cellular or gene therapy alone.