Adenoviral gene transfer to the injured spinal cord of the adult rat

We have investigated gene transfer to the injured adult rat spinal cord by the use of a recombinant adenovirus. 10(5) or 5 X 10(6) plaque-forming unit s (pfu) of a replication-defective adenoviral vector carrying the green flu orescent protein (GFP) reporter gene were injected into a dorsal hemisectio n lesion at spinal level T8. Gene expression and inflammatory responses wer e studied 4, 8 and 21 days after surgery. Numerous cells within 3 mm on eac h side of the lesion were found to express high levels of GFP at 4 days aft er infection as shown by GFP fluorescence and immunohistochemistry. At 8 da ys, expression was still strong although weaker than at 4 days. After 21 da ys, transgene expression had almost ceased. Expression was neither higher n or more prolonged in animals that had received the higher vector dose. Dela yed injection 1 week after spinal injury also did not increase transgene ex pression. Infected cell types were identified immunohistochemically. The mo st prominent transduced cells were spinal motoneurons. Additionally, we cou ld identify other neurons, astrocytes, oligodendrocytes and peripheral cell s infiltrating the lesion site. The glial and inflammatory reaction at and around the lesion was studied by cresyl violet histology, alpha-GFAP, OX42 and alpha-CD-8 immunohistochemistry. No significant differences from contro ls were found in the low virus group; in the high virus group a strong inva sion of CD-8-positive lymphocytes was found. Open-field locomotion analysis showed virus-infected animals performing as well as control animals. Adeno viral gene transfer may be an efficient way to introduce factors to the inj ured spinal cord in paradigms of research or therapy.