An optimal non-viral gene transfer method for genetically modifying porcine bone marrow-derived endothelial progenitor cells for experimental therapeutics

Abstract

No currently available treatment is able to generate new contractile tissue or significantly improve cardiac function after myocardial infarction (MI), a leading cause of morbidity and mortality worldwide. Although gene transfer-enhanced endothelial progenitor cells (GTE-EPCs) show effectiveness in MI treatment in small animal models, no clinical trials using GTE-EPCs have been documented. Before the introduction of GTE-EPCs into human trials, gene-transfer-mediated augmentation of EPC function in animal models that reflect the human MI scenario should be tested. In this regard, a porcine model is the best choice since pigs have cardiac size, hemodynamics and coronary anatomy similar to that of humans. To examine GTE-EPC therapeutic efficacy in pig MI models, an efficient method for gene transfer into pig EPCs is required, which however, has been poorly documented. Pig bone marrow mononuclear cells were isolated and cultured in EGM-2 medium to obtain bone marrow-derived EPCs (BM-EPCs) that were characterized by immunostaining and the tube formation assay. Gene transfer was optimized in 6-well plates using a GFP and a VEGF plasmid, and scaled up in T75 flasks. Gene transfer efficiency was determined by fluorescence microscopy and flow cytometry. VEGF levels were measured by ELISA. Cell proliferation was assayed by the CCK-8 kit. (1) BM-EPCs expressed VEGFR2 and eNOS but not CD45 protein, and formed tube structures on Matrigel; (2) several chemical compounds were explored with the highest transfection efficiency of 41.4% ± 5.8% achieved using Lipofectamine 3000; (3) the VEGF level in culture medium after VEGF transfection was 378 ± 48 ng/106 cells; and (4) BM-EPCs overexpressing VEGF had significantly enhanced proliferation than GFP-transfected EPCs. A simple, easy and cheap method that can be applied to produce a large number of genetically-modified BM-EPCs was established, which will facilitate the study of GTE-EPC therapeutic efficacy in pig MI model.