DNA/dendrimer complexes mediate gene transfer into murine cardiac transplants ex vivo

Starburst polyamidoamine dendrimers are synthetic polymers with unique stru ctural and physical characteristics suitable for DNA gene transfer. Our pre vious studies demonstrated that Starburst dendrimers augment plasmid-mediat ed gene transfer efficiency in a nonvascularized, cardiac transplantation m odel. In this study, the fifth generation of ethylenediamine core dendrimer was investigated for its ability to enhance gene transfer and expression i n a clinically relevant murine vascularized heart transplantation model. Th e plasmid pMP6A-beta -gal, encoding beta -galactosidase (beta -cal), was in cubated with dendrimers to form complexes. The complexes were perfused via the coronary arteries during donor graft harvesting, and reporter gene expr ession was determined by quantitative evaluation of X-Gal staining. The gra fts infused with pMP6A-beta -gal/dendrimer complexes showed beta -Gal expre ssion in myocytes from 7 to 14 days. A number of variables for transfer of the DNA/dendrimer complexes were tested, including DNA:dendrimer charge rat ios, concentrations of DNA and dendrimer, preservation solutions, ischemic time, and enhancement of vascular permeability by serotonin, papaverine, an d VEGF administration. The results showed that DNA/dendrimer complexes cont aining 20 mug of DNA and 260 mug of dendrimer (1:20 charge ratio) in a tota l volume of 200 mul resulted in highest gene expression in the grafts. The results also showed that prolonged incubation (cold ischemic time) to 2 h a nd pretreatment with serotonin further enhanced gene expression.