EX-VIVO GENE-TRANSFER INTO MYOCARDIUM USING REPLICATION-DEFECTIVE RETROVIRUS

Heart transplantation is the most effective therapy for chronic severe heart failure, but there is an extreme shortage of hearts available. We examined the possibility that cardiomyocytes can be modified geneti cally prior to being grafted to the heart. We used a replication-defec tive retrovirus carrying the beta-galactosidase (beta-gal) reporter ge ne. The beta-gal gene was transduced into murine fetal cardiac myocyte s by culturing a recombinant retrovirus-producing cell line in a Trans well plate hung into the primary cardiomyocyte culture. The cultured c ells were stained with the di-beta-D-galactopyranoside (FDG) and were sorted by fluorescence-activated cell sorting (FACS). FACS analysis sh owed that 25.5 +/- 4.3% of the cardiomyocytes in a primary culture wer e positive for beta-gal activity. These cells were transplanted into t he hearts of syngeneic adult mice. Expression of the beta-gal gene in the grafted cells was demonstrated by staining with 5-bromo-4-chloro-3 -indoyl-beta-D-galactoside (X-gal). Gene expression was recognized as long as 6 mo after cell transplantation. Histologic analysis showed ne ither inflammation nor fibrous scar tissue on the host myocardium. Thi s study demonstrated that genetically modified cardiac cells were tran splantable to the heart.