Efficient gene delivery into adult cardiomyocytes by recombinant Sindbis virus

Somatic gene therapy as a potential strategy for the treatment of myocardial diseases relies on an efficient gene transfer into cardiac muscle cells. The difficulty of delivering genes into adult cardiomyocytes exists not only in vivo but also in primary culture systems. Therefore, possibilities for ex vivo gene transfer and the in vitro study of physiological processes by reverse genetics are limited. We investigated the potential of an alphavirus-based vector system to transduce adult rat cardiomyocytes (ARC) in culture using a replication-deficient Sindbis virus (SIN) encoding beta-galactosidase (SIN-LacZ). Transduction efficiency depended on the virus concentration used, with expression of the reporter gene being detectable in up to 80% of cultured ARC as early as 24 h after infection. We observed a remarkably lower cytotoxicity of this viral vector in ARC than in other cells such as fibroblasts and neonatal cardiomyocytes. Additionally, no perceptible changes in the morphology of the nuclei or cytoskeleton were found in ARC 48 h after infection with SIN-LacZ. We conclude that SIN vectors are useful for gene delivery into adult cardiomyocytes and believe that improved versions of this viral system may be useful for cardiovascular gene therapy in the future.