Treatment of spinal cord injury (SCI) encompasses the rescue of injured neurons, the promotion of axonal regeneration and the formation of functional synapses. This project focuses on one aspect of an envisioned multi-modai therapy - the promotion of axonal regeneration. The proposed experiments are designed to test the hypothesis that local release of induced neurotrophic factors (NFs) in the spinal cord will enhance axonal regeneration after trauma. When adenoviral vectors carrying NF genes (Adv-nf) are injected into peripheral muscles they are transported to motoneurons where the genes are expressed and NFs are released. The NFs protect spinal cord motoneurons from trauma-induced death without evoking an inflammatory response. To test the hypothesis that local expression of NFs will support axonal regeneration adenoviral vectors will be delivered to the spinal cord in which the corticospinal tract (CST) has been unilaterally lesioned at the level of the pyramids. In this lesion model there is no trauma in the spinal cord so that tissue destruction, ischemia, and paralysis are not factors in determining the outcome and may allow better understanding of the effects of NFs on sprouting.
The specific aims of this proposal are to: Test whether expression of NFs by genetically modified cells in the spinal cord will induce and sustain axonal sprouting after injury (Specific aim 1). Genes for neurotrophin 3 (NT-3), nerve growth factor (NGF), ciliary neurotrophic factor (CNTF), brain-derived neurotrophic factor (BDNF) and glial cell line-derived growth factor (GDNF) will be delivered singly and in combination to the spinal cord by: (1) direct injection of Adv-nfs into spinal cord tissue, (2) transduction of ependymal cells so that they release NFs into the cerebrospinal fluid, and (3) retrograde delivery of Adv-nfs to dorsal root ganglion and motoneurons. A panel of adenoviral vectors will be generated that contain a FLAG sequence to aid in immunological detection and the Elongation Factor (EF) promoter that is more efficient in mammalian cells.
Specific aim 2 is designed to characterize the extent of expression and the pattern of sprouting.
Specific aim 3 is designed to characterize the effects of Adv-nf-induced sprouting on motor behavior. If the investigators demonstrate that this strategy is effective in inducing axonal growth it would be a basis of future studies leading to a treatment of SCI.
| Grider, M H; Park, D; Spencer, D M et al. (2009) Lipid raft-targeted Akt promotes axonal branching and growth cone expansion via mTOR and Rac1, respectively. J Neurosci Res 87:3033-42 |
