High sensitivity of neonatal rat hepatocytes to retroviral-mediated gene transfer and their transplantation into the spleen of adult rat.

To optimize conditions for retroviral-mediated transfer of a recombinant gene to hepatocytes, the pMNSM-Tk-lacZ vector, which we had constructed to express the bacterial beta-galactosidase gene, was transduced to rat hepatocytes under various conditions, and the expression of beta-galactosidase activity was examined by cytochemical staining. Compared to the hepatocytes of adult rats, those of newborns were about 50-100 times more sensitive to transduction with the beta-galactosidase gene in vitro. The sensitivity was high in the newborn hepatocytes when the virus was infected on days 1 and 2 after initiation of culture. However, the sensitivity to infection did not correlate with the DNA synthetic activity. The gene transfer was feasible not only to hepatocytes in monolayer culture but also to those in spheroid culture. The spheroidal aggregates containing hepatocytes transduced with the beta-galactosidase gene could be transplanted into the spleen of syngenic adult rat, although the expression was very low.