Peripheral nerve is capable of regenerating after injury, and after complete transection surgical repair is followed by axonal regeneration that often leads to functional recovery. However when the site of injury is in the spinal root, close to the cell body, axonal injury leads to neuron cell death and even prompt surgical anastomosis of the proximal root to the distal nerve is ineffective in restoring function. Several lines of evidence suggest that death of motor neurons, proceeding through apoptotic pathways, forestalls the possibility of successful regeneration after proximal axonal injury. We have developed genomic herpes simplex virus (HSV)-based vectors that are capable of delivering genes into neurons in an effective and efficient manner. We have demonstrated that stereotactic inoculation of HSV vectors engineered to express the anti-apoptotic peptide Bcl-2 or the glial cell derived neurotrophic factor (GDNF) into the ventral horn of the spinal cord prevents death of motor neurons following proximal spinal root avulsion. Transduction with both Bcl-2 and GDNF expressing vectors together was required to preserve the neurotransmitter phenotype of the rescued neurons measured 2 weeks after the injury. But the most important outcome is functional recovery. Therefore we will test the hypothesis that: using HSV-based vectors to deliver and express a combination of anti-apoptotic and neurotrophic factors within the motor neurons of the spinal cord will improve cell survival and enhance functional recovery after proximal spinal root injury.
Five Specific Aims are proposed.
Specific Aim 1 : To assess the functional recovery mediated by HSV-mediated gene transfer of Bcl-2, GDNF, or both transgenes in combination following proximal spinal root injury.
Specific Aim 2 : To define the anatomic basis of the functional recovery produced by HSV-mediated gene transfer of Bcl-2, GDNF, or both transgenes in combination following proximal root injury.
Specific Aim 3 : To evaluate the effect of vector injection into spinal cord on recovery of sensory function after spinal root injury.
Specific Aim 4 : To investigate the molecular mechanisms underlying the effects of transgene-mediated expression of Bcl-2 and GDNF on neuronal survival and axonal regeneration.
Specific Aim 5 : To define the temporal window following injury during which gene transfer therapy may be delivered. In clinical practice, spinal root injury is an important cause of morbidity and function. ? ?
