Neuroprotection of spinal motoneurons following targeted transduction with an adenoviral vector carrying the gene for glial cell line-derived neurotrophic factor.

Application of neurotrophic factors (NFs) to the cut stump of peripheral nerves confers transient (1- to 2-week) neuroprotection of motoneurons from axotomy-induced death in neonates. We tested whether lumbar spinal motoneurons would be protected from axotomy-induced death when they were genetically modified to produce NFs in situ. Adenoviral (Adv) vectors carrying neurotrophic factor genes under control of the Rous sarcoma virus long terminal repeat promoter (Adv.RSV-nf) or a control vector containing the beta-galactosidase (beta-gal) gene (Adv.RSV-betagal) was injected into the hindlimb muscles of neonatal rats. The Adv were taken up by peripheral nerves and transported to lumbar spinal cord motoneurons where the transgenes were expressed. A fraction (18%) of the motoneurons that projected through the sciatic nerve were transduced with Adv.RSV-betagal. Expression of Adv.RSV-betagal was detected in motoneurons after 7 days and 3 weeks, with no evidence of vector- or beta-gal-induced toxicity or inflammation. PCR, immunocytochemistry, and RT-PCR demonstrated transport of the Adv.RSV-nf vectors to motoneurons and their expression. After retrograde transport of an Adv.RSV-nf vector carrying the gene for glial cell line-derived neurotrophic factor, a substantial proportion of the sciatic nerve motoneurons were resistant to axotomy-induced death 7 days and 3 weeks after sciatic nerve transection (56 and 44%, respectively), compared to Adv.RSV-betagal controls (2.5 and 0%, respectively).