A MODIFIED UROKINASE PLASMINOGEN-ACTIVATOR INDUCES LIVER-REGENERATIONWITHOUT BLEEDING

Direct retrovirus-mediated hepatic gene transfer results in permanent gene expression; however, gene transfer requires surgical hepatectomy (to stimulate cell division) and has been inefficient, We recently use d recombinant adenovirus vectors that transiently expressed urokinase from mouse hepatocytes to induce hepatocellular regeneration in place of a partial hepatectomy, The adenovirus method allowed for five-fold more efficient retrovirus transduction in vivo compared to the convent ional partial hepatectomy approach, The major problem with the urokina se-mediated hepatic regeneration was the transient secretion of urokin ase into the bloodstream that led to hypocoagulation, To circumvent th is side-effect, the urokinase protein was modified by adding amino-ter minal and carboxy-terminal endoplasmic reticulum retention signals. Th e recombinant urokinase molecules expressed from adenoviral vectors re mained in hepatocytes, were enzymatically active, and resulted in simi lar rates of hepatic regeneration as found with the secreted urokinase . Modified urokinase-mediated liver regeneration was equally capable o f allowing retrovirus-mediated gene transfer in vivo. Thus, the method of direct retrovirus transduction of hepatocytes becomes clinically r elevant as the technology becomes safer.