Therapeutic time window of adenovirus-mediated GDNF gene transfer after transient middle cerebral artery occlusion in rat

The time dependent influence of adenovirus-mediated glial cell line-derived neurotrophic factor (GDNF) gene (Ad-GDNF) was examined after 90 min of transient middle cerebral artery occlusion (MCAO) in rats. Treatment with Ad-GDNF significantly reduced the infarct volume when immediately administered after the reperfusion, but became insignificant when administered at 1 h after the reperfusion as were the cases treated with vehicle- and adenoviral vector containing the E. coli lacZ gene (Ad-LacZ)-treated groups. The protective effect of GDNF was related to the significant reduction of the number of TUNEL positive cells as well as immunohistochemical positive cells for active caspase-3 but not -9. These results showed that exogenous GDNF gene transfer successfully reduced the infarct size in a time-dependant manner by suppressing active caspase-3 but not active caspase-9. However, the therapeutic time window was shorter than the effect of GDNF protein itself previously reported.