Adenovirus-mediated glial cell line-derived neurotrophic factor gene delivery reduces motor neuron injury after transient spinal cord ischemia in rabbits

Objective: Glial cell line-derived neurotrophic factor (GDNF) has protectiv e effects on various injuries involving the central and peripheral nervous systems in vitro and vivo. However, the possible protective effect of GDNF on spinal cord ischemia and the exact mechanism involved in the ameliorativ e effect of GDNF on ischemic spinal cord injuries are not fully understood. Therefore, we investigated the possible protective effect of the adenoviru s-mediated GDNF gene delivery on transient spinal cord ischemia in rabbits. Methods: The adenoviral vector (lacZ gene as a control or GDNF gene contain ed) was injected directly into the lumbar spinal cord via a needle inserted into the dorsal spine 2 days before the animal was subjected to 15 minutes of spinal cord ischemia induced by infrarenal aortic occlusion, In situ te rminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick-end lab eling (TUNEL staining) was performed, and temporal profiles of the GDNF and caspase-3 (caspase-3 is the market of apoptotic change) immunoreactivity w ere investigated. Results: In the control rabbit, the majority of motor neurons showed select ive cell death at 7 days of reperfusion. Immunocytochemistry showed that in situ TUNEL staining was selectively detected at 2 days of Ic perfusion in motor neuron nuclei. GDNF and caspase-3 were selectively induced in the mot or neuron cells at 8 hours of reperfusion, In the GDNF-treated group, a lar ge population of motor neuron cells was still surviving at 7 days after hav ing been subjected to 15 minutes of ischemia, Unlike the control group, the GDNF-treated group expressed GDNF persistently. Induction of TUNEL stainin g and immunoreactivity for caspase-3 were greatly reduced by the GDNF treat ment. Conclusion: These results suggest that the reduction in motor neuron death by GDNF was greatly associated with a reduction in DNA fragmentation and ap optotic signals of the caspase-3 cascade; they further suggest a great pote ntial for gene therapy for paraplegic patients in the future.