Efficient gene transfer into cardiac myocytes using adeno-associated virus (AAV) vectors

Adeno-associated virus (AAV) vectors, derived from a non-pathogenic parvovirus, are considered to be an appropriate gene transfer vehicle for both dividing and non-dividing cells. In the present study, we investigated whether the rat heart could be efficiently transduced with AAV vectors. Rat cardiac myocytes (CM) were infected with AAV-lacZ vector containing beta-galactosidase (beta-gal) gene in vitro, and the expression of beta-gal in CM was evaluated by X-gal staining and beta-gal ELISA. With increasing multiplicities of infection (MOI), more than 60% of CM were stained positively with X-gal, and the beta-gal expression increased to 31.1 +/- 4.6 ng/mg protein in a MOI-dependent manner (MOI: 10(4) to 10(6) particles/cell). The beta-gal expression was also increased in an incubation period-dependent manner (1-24 h). beta-gal expression was maximal at day 3 and then gradually decreased with time. However, beta-gal expression at day 14 was almost the same level as that at day 1 (45.5 +/- 5.9 v 55.2 +/- 6.2 ng/mg protein). Excised rat right ventricular papillary muscles were also infected with AAV-lacZ ex vivo. When the beta-gal expression was evaluated by X-gal staining, more than 80% of CM in the papillary muscles were stained positively, indicating efficient gene transfer into CM using AAV vectors. These findings suggest that AAV vectors are promising for cardiac gene therapy.