[Effects of adenovirus-mediated HSV-tk/GCV system on lens epithelium].

OBJECTIVE: To investigate the efficiency of adenovirus-mediated herpes simplex virus thymidine kinase/ganciclovir (HSV-tk/GCV) suicide gene therapy system on calf lens epithelial cells and analyze the mechanism of cell death.

METHODS: Calf lens epithelial cells were infected in vitro by the recombinant adenoviral vector containing HSV-tk gene (suicide gene) and followed by the treatment of GCV. Finally the efficiency was observed. In addition, the E(1) deleted empty adenoviral vector was used as the control. The conditions of cell necrosis and apoptosis were detected by electron microscope and staining with TUNEL and AO-EB (acridine orange-ethidium bromide) methods.

RESULTS: Calf lens epithelial cells trans-infected by adenoviral vector containing HSV-tk gene were significantly inhibited in vitro by GCV treatment. And the phenomenon of bystander effect was confirmed. By comparison, there was no obvious toxin on the cells infected by empty adenoviral vector. Under the treatment of various dosages of GCV, a significant difference of the cell survival rate existed between the ADV/HSV-tk group and the ADV/Empty group (t = 4.94, P < 0.01). The killing efficiency of GCV increased with the prolongation of time. And the cell survival rate of the ADV/HSV-tk group was much lower than that of the ADV/Empty group (t = 11.28, P < 0.001). Many lens epithelial cells were found in the group of ADV/HSV-tk. The levels of necrosis (t = 14.72, P < 0.001) and apoptosis (t = 7.28, P < 0.01) of lens epithelial cells in the ADV/HSV-tk group were greatly higher than those in the group of ADV/Empty.

CONCLUSIONS: Adenoviral vector may successfully transduct HSV-tk gene (suicide gene) into calf lens epithelial cells. The lens epithelium expressing HSV-tk gene can be effectively killed by GCV. The mechanism of cell death caused by HSV-tk/GCV is probably necrosis and apoptosis. Therefore, adenovirus-mediated HSV-tk/GCV suicide gene therapy system may provide an effective approach to the treatment of posterior capsule opacification (PCO).