A modified urokinase plasminogen activator induces liver regeneration without bleeding

Area of Science:

• Hepatology
• Gene Therapy
• Molecular Biology

Background:

• Direct retrovirus-mediated gene transfer into hepatocytes offers permanent expression but requires surgical hepatectomy, which is inefficient.
• Recombinant adenovirus vectors expressing urokinase can induce hepatocellular regeneration, improving gene transfer efficiency compared to partial hepatectomy.

Purpose of the Study:

• To develop a safer method for urokinase-mediated liver regeneration to enable efficient retrovirus-mediated gene transfer.
• To circumvent the hypocoagulation side-effect associated with secreted urokinase by retaining the protein within hepatocytes.

Main Methods:

• Recombinant adenovirus vectors were used to express urokinase in mouse hepatocytes.
• The urokinase protein was modified with endoplasmic reticulum retention signals to prevent its secretion.
• The modified urokinase's enzymatic activity and ability to induce hepatic regeneration were assessed.
• The efficacy of modified urokinase-mediated regeneration for retrovirus-mediated gene transfer was evaluated in vivo.

Main Results:

• Adenovirus-mediated urokinase expression led to five-fold more efficient retrovirus transduction than partial hepatectomy.
• Modified urokinase, retained within hepatocytes, was enzymatically active and induced hepatic regeneration at rates similar to secreted urokinase.
• This modified urokinase approach effectively enabled retrovirus-mediated gene transfer in vivo without causing hypocoagulation.

Conclusions:

• Modifying urokinase with ER retention signals creates a safer method for liver regeneration.
• This enhanced liver regeneration facilitates efficient and safer retrovirus-mediated gene transfer into hepatocytes.
• The improved technology advances the clinical relevance of direct retrovirus transduction for permanent gene expression.