Cotransfection of vascular endothelial growth factor-A and platelet-derived growth factor-B via recombinant adeno-associated virus resolves chronic ischemic malperfusion: Role of vessel maturation

Objectives: We set out to investigate the ability of cardiotropic adeno-associated viral vector (AAV2.9 = recombinant adeno-associated virus [rAAV]) to induce prolonged expression of vascular endothelial growth factor (VEGF)-A and platelet-derived growth factor (PDGF)-B in a rabbit hindlimb ischemia model and a pig model of hibernating myocardium. Background: Gene therapy to induce angiogenesis and arteriogenesis has produced mixed results. However, long-acting viruses, such as rAAV, as well as combined induction of angiogenesis and vessel maturation might extend the therapeutic potential. Methods: In rabbits, 0.5 × 10¹¹ particles rAAV.VEGF-A with or without 1 × 10¹² particles rAAV.PDGF-B were retroinfused at day 7 after femoral artery excision. At days 7 and 35, collateral counts and perfusion were determined, each value given as the day 35/day 7 ratio. Capillary-to-muscle fiber ratio was determined at day 35. In pigs, implantation of a reduction stent graft into the circumflex artery led to complete occlusion at day 28. At this time point, retroinfusion of rAAV.VEGF-A (1 × 10 ¹³ particles), rAAV.VEGF-A/PDGF-B (2 × 10¹² and 4 × 10¹² particles, respectively) or mock transfection was performed. Ejection fraction and left ventricular end-diastolic pressure were assessed at days 28 and 56. Results: In rabbits, rAAV.VEGF-A strongly induced angiogenesis (capillary-to-muscle fiber ratio; 1.67 ± 0.09 vs. 1.32 ± 0.11 in rAAV.LacZ-treated limbs, p < 0.05), but not collateral growth (125 ± 7% vs. 106 ± 7%, p = NS) or perfusion (136 ± 12% vs. 107 ± 9%, p = NS). With VEGF-A/PDGF-B cotransfection, collateral growth increased to 146 ± 9%, perfusion to 163 ± 8% of the respective day 7 value (p < 0.05). In the pig model, retroinfusion of rAAV.VEGF-A/PDGF-B increased regional myocardial blood flow reserve from 101 ± 4% (rAAV.Mock) to 129 ± 8% (p < 0.05), based on collateral growth (3.2 ± 0.3 in rAAV.Mock vs. 9.0 ± 0.4 in rAAV.VEGF-A/PDGF-B, p < 0.05), whereas rAAV.VEGF-A did not alter flow reserve (112 ± 7%) or collateral count (5.2 ± 0.7). rAAV.VEGF-A/PDGF-B improved ejection fraction (55 ± 5% vs. 34 ± 3% in rAAV.Mock, p < 0.05) unlike rAAV.VEGF-A (37 ± 2%). Conclusions: Retroinfusion of rAAV.VEGF-A alone induces angiogenesis, but fails to enhance collateralization and perfusion, unless PDGF-B is cotransfected. In addition to neovascularization, rAAV.VEGF-A/PDGF-B improves regional and global myocardial function in hibernating myocardium.