GENE-TRANSFER INTO THE MAMMALIAN KIDNEY - DIRECT RETROVIRUS-TRANSDUCTION OF REGENERATING TUBULAR EPITHELIAL-CELLS

Gene transfer using retroviral vectors requires cell replication for i nsertion of the DNA provirus. Since the mitotic index of the mammalian kidney is very low, renal tubular cell replication was induced in adu lt rats as part of a regenerative response to the nephrotoxic injury i nduced by an intraperitoneal injection of folic acid. At 48 h, at the time of maximum H-3-thymidine incorporation, the left kidney was direc tly injected with a suspension of the Psi2 BAG retrovirus which transd uces the beta-galactosidase gene. At 1-7 weeks after virus administrat ion the left kidney was harvested. Using the polymerase chain reaction to amplify viral DNA, successful gene transfer was achieved in 8 of 1 5 kidneys. In 6 of 10 kidneys assessed histochemically positive staini ng for beta-galactosidase activity was detected in the cytoplasm of tu bular epithelial cells. There was no evidence of gene expression in gl omerular, vascular or endothelial cells. All analyses were negative in vehicle-injected kidneys and in the kidneys of animals which did not receive pretreatment with folic acid. These studies demonstrate the fe asibility of gene transfer into the adult kidney provided that replica tion of specific cell types can be achieved.