How to Optimize In Vivo Gene Transfer to Cardiac Myocytes: Mechanical or Pharmacological Procedures?

Abstract

An efficient gene delivery system is a prerequisite for myocardial gene therapy. Among the various procedures studied so far, catheter-based percutaneous gene delivery to the myocardium through the coronary vessels seems the most relevant to routine clinical practice; however, the optimal conditions remain to be determined. We selectively infused adenoviral vectors encoding luciferase (1 × 10⁹ PFU) or β-galactosidase (1 × 10¹⁰ PFU) into coronary arteries of adult rabbits in various experimental conditions. Coronary artery occlusion for 30 sec, during and after adenovirus delivery, was required to observe luciferase activity in the target area of the circumflex artery (4.0 ± 1.0 × 10⁵ vs. 1.1 ± 0.2 × 10⁴ RLU/mg with and without coronary occlusion, respectively, p < 0.01, and 1.0 ± 0.1 × 10³ RLU/mg using nonselective infusion). When adenoviruses were delivered using high-pressure infusion (82 ± 12 vs. 415 ± 25 mmHg before and during infusion, respectively, p < 0.01), luciferase activity increased to 8.5 ± 2.5 × 10⁵ RLU/mg (p < 0.05 vs coronary occlusion alone). Coronary venous sinus occlusion with saline buffer retroinfusion starting before and during anterograde adenovirus delivery resulted in a further 4.7-fold increase in luciferase activity(4.4 ± 0.8 × 10⁶ RLU/mg, p < 0.01) with 5-25% blue-stained myocytes in the target area, compared with 0-5% with the other procedures. Histamine or VEGF-A₁₆₅ pretreatment, used to increase vascular permeability, slightly increased gene transfer efficiency (8.5 ± 2.0 × 10⁵ and 9.0 ± 2.5 × 10⁵ RLU/mg respectively,p < 0.05 vs. coronary occlusion alone). We conclude that catheter-mediated adenoviral gene transfer to cardiac myocytes through coronary vessels can be a very efficient procedure for myocardial gene therapy, particularly when the vector residence time and perfusion pressure in the vessels are increased.