Abstract 3980: Nanoparticle Based Delivery of Hypoxia Regulated VEGF Transgene System Combined With SkMs Engraftment: A Safer Approach to Treat Ischemic Cardiomyopathy
Objective: Regulated promoter system consented to tightly controlled gene expression is desirable for safe and efficacious overexpression of therapeutic transgenes. Combined with skeletal myoblast (SkMs) transplantation, we report the efficacy of hypoxia-regulated VEGF gene delivery for myocardial repair during acute phase cardiomyopathy.
Methods and Results. A hypoxia-regulated VEGF plasmid (pHRE-VEGF) was developed by inserting 5 copies of hypoxia response elements (HRE). At optimal transfection conditions, flowcytometry revealed that ~30% SkMs were transfected for the gene overexpression using polyethyleneimine nanoparticles. Peak VEGF expression was significantly higher in pHRE-VEGF transfected SkMs (VEGFSkMs) grown under hypoxia (151.34±8.59 ng/ml) as compared with normoxia (16.92±2.74 ng/ml). The efficacy of our hypoxia-regulated gene expression system was assessed in a rabbit model of ischemic cardiomyopathy, developed by permanent coronary artery ligation. The animals were grouped (n=16/group) to receive basal M199 without cells (group-1) or containing non-transfected SkMs (group-2) or VEGFSkMs (group-3). In group-4, VEGFSkMs 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. The number of blood vessels per high magnification field (400x) at 2-weeks after their respective treatment, using PECAM specific immunostaining, was 20.1±1.3 in group-3 which was significantly higher than any other groups (p<0.05). Improved blood flow (ml/min/g) in the left ventricle (LV) anterior wall was observed in group-3 (1.28±0.09) as compared with group-1 (0.76±0.05) and group-2 (0.96±0.06) (group-3 vs groups-1 and 2 p<0.05), and similar to group-4 (1.26±0.05). LV ejection fraction was best preserved in group-3 (58.4±1.75l%) which was insignificantly different from group-4 (61.1±1.8%), and group-2 (52.8±1.4%) but significantly changed as compared with groups-1 (44.7±2.2%, p<0.05).
Conclusion: Nanoparticle based delivery of hypoxia regulated VEGF transgene combined with SkMs during acute phase cardiomyopathy effectively preserves LV regional blood flow and contractile function of the heart.