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 x 10(9) PFU) or beta-galactosidase (1 x 10(10) 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 x 10(5) vs. 1.1 +/- 0.2 x 10(4) RLU/mg with and without coronary occlusion, respectively, p < 0.01, and 1.0 +/- 0.1 x 10(3) 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 x 10(5) 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 x 10(6) 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-A(165) pretreatment, used to increase vascular permeability, slightly increased gene transfer efficiency (8.5 +/- 2.0 x 10(5) and 9.0 +/- 2.5 x 10(5) 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.

A minimally invasive approach for efficient gene delivery to rodent hearts

“…A cardiac arrest of 2 min (1.5 min transfection time) allowed to transfect 18% of CMs in rats, whereas an extended viral incubation time up to 4.5 min extended the positive CMs to 43%, suggesting that transfection efficiency correlates directly with viral incubation time. Similar to our results, Logeart et al 13 showed that a brief interruption of coronary flow is required to obtain significant gene transduction in vivo and the efficiency tended to increase with the time period of coronary artery occlusion. In the hamster model, Ikeda et al 3 recently demonstrated that the short incubation time (10-20 s) in single-pass manner yielded only 4-5% of myocardial gene transduction compared to a much higher efficiency when the incubation time was extended to 5 min during hypothermia together with cross-clamping of the ascending aorta and main pulmonary artery.…”

“…[12][13][14] Among the parameters tested, it was not surprising that prolongation of viral transfection time within the heart is important to elevate the efficiency of myocardial transfection. Having solved this problem by our cardiac arrest protocol, we could optimize the transfection efficiency.…”

“…Given the size of adenoviral particles (73 nm), which is too large to pass the normal endothelial barrier, disruption of the endothelial tight junction seemed to be a prerequisite to ensure access of the virus to the interstitium. 12 Therefore, factors capable of increasing endothelial permeability such as histamine, 3,13 bradykinin and serotonin 17 also improve gene transduction in the isolated hearts and in vivo. Surprisingly, pretreatment of coronary vessels with the nitric oxide (NO) donor SNAP or histamine, substances well known to elevate vascular permeability, did not increase the transfection rate in our study.…”

“…Therefore, it appears necessary to optimize multiple factors that have been previously identified by Donahue et al 12 in an isolated heart model also under in vivo conditions. 13,14 These authors have demonstrated that coronary flow, virus titer, viral exposure time and endothelial permeabilization are key factors affecting the efficiency of intracoronary gene delivery. In addition, transcoronary gene transfer is favored by high intravascular pressure as a major driving force to enhance the viral extravasation as shown in rats, 7 rabbits 13,14 and swine.…”

“…13,14 These authors have demonstrated that coronary flow, virus titer, viral exposure time and endothelial permeabilization are key factors affecting the efficiency of intracoronary gene delivery. In addition, transcoronary gene transfer is favored by high intravascular pressure as a major driving force to enhance the viral extravasation as shown in rats, 7 rabbits 13,14 and swine. 15 In view of these findings, the aim of the present study was to develop a catheter-based delivery system that permits a homogenous and efficient gene transfer in the close-chest rodent heart.…”