Selection of in vivo retrovirally transduced hepatocytes leads to efficient and predictable mouse liver repopulation

Stable liver gene transfer is generally limited by the low efficiency of co mmonly used vectors. One way to circumvent this difficulty is to confer a s elective advantage on transduced hepatocytes, allowing them to progressivel y repopulate the liver. We have used a strategy for in vivo selection and c ontrolled amplification of a small percentage of retrovirally engineered he patocytes. Using a bicistronic retroviral vector encoding a reporter gene a nd Bcl2, which confers on liver cells a survival advantage against the Fas apoptotic pathway, we demonstrate that 1.5% of initially transduced hepatoc ytes repopulate up to 85% of the liver after 10 injections of a Fas agonist antibody. Moreover, we show that the kinetics of liver repopulation is hig hly predictable. This system provides a general means of expanding at will engineered hepatocytes in vivo and offering the possibility to obtain a gen etically modified liver expressing a gene of interest in a desired proporti on of hepatocytes.