Abstract

A regulated promoter system to control gene expression is desirable for safe and efficacious over-expression of therapeutic transgene. Combined with skeletal myoblast (SkMs), we report the efficacy of hypoxia-regulated VEGF gene delivery for myocardial repair during acute myocardial infarction (AMI). A hypoxia-regulated VEGF plasmid (pHRE-VEGF) was developed. After optimization, ∼30% SkMs were transfected using polyethyleneimine (PEI) nanoparticles. The peak VEGF expression was higher in pHRE-VEGF transfected SkMs ((VEGF)SkMs) under hypoxia (151.34 ± 8.59 ng/ml) than that with normoxia (16.92 ± 2.74 ng/ml). The efficacy of hypoxia-regulated gene expression system was assessed in a rabbit model of AMI. The animals were grouped to receive basal M199 without cells (group-1) or containing non-transfected SkMs (group-2) or (VEGF)SkMs (group-3). In group-4, (VEGF)SkMs were injected into normal heart to serve as normoxia control. Improved SkM survival was observed in group-3 and -4 (p < 0.05 vs group-2) at day-3 and 7 after transplantation. Blood vessel density was 20.1 ± 1.3 in group-3 which was significantly higher than any other groups (p < 0.05) at 2 weeks after treatment. Improved blood flow (ml/min/g) in the left ventricle (LV) anterior wall was observed in group-3 (1.28 ± 0.09, p < 0.05) as compared with group-1 (0.76 ± 0.05) and group-2 (0.96 ± 0.06), and similar to group-4 (1.26 ± 0.05). LV ejection fraction was best preserved in group-3 (58.4 ± 1.75%) which was insignificantly different from group-4 (61.1 ± 1.8%), and group-2 (52.8 ± 1.4%), but significantly improved compared with group-1 (44.7 ± 2.2%, p < 0.05). The study demonstrates that nanoparticle based delivery of hypoxia-regulated VEGF transgene combined with SkMs during AMI effectively preserves LV regional blood flow and contractile function of the heart.

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