Cardiomyocytes

Conventional ways of introducing genes into cells, such as calcium phosphate transfections and liposome or lipofectamine-mediated methods, work poorly in cardiomyocytes. They can be useful for gene reporter studies, but are of little value when a gene needs to be introduced into a large number of cardiac cells. Therefore, viral vectors are used to achieve this goal. Type 5 adenoviruses work well in cardiomyocytes, but they are hard to produce, and moreover, their immunogenicity prevents their use in long-term in vivo experiments (1 ). The adeno-associated virus is suitable for in vivo myocardial gene transduction because of its low or absent immunogenic potential (1 ), but its use for in vitro studies is limited by the low gene expression achieved (less then 10% in cardiomyocytes) (2 ). The classical retroviral systems are of no practical value either for studies of growth-arrested cardiomyocytes owing to the requirement of M phase for integration with host genomic DNA. Lentiviruses, however, can enter the nucleus even without mitosis (3 ), and recently, a new variant of third generation lentivirus (“advanced” generation) has been described (4 ) in which sequences of the pol gene of human immunodeficiency virus type 1 (HIV-1), central polypurine tract (cPPT) and of the posttranscriptional regulatory element of woodchuck hepatitis virus (WPRE) have been inserted. The cPPT is a cis element that has been associated with increased gene expression in growth-arrested human hematopoietic progenitor cells (4 ).