Brain-derived neurotrophic factor gene transfer with adeno-associated viral and lentiviral vectors prevents rubrospinal neuronal atrophy and stimulates regeneration-associated gene expression after acute cervical spinal cord injury

Study Design. Experimental animal study. Objective. To determine if viral vectors carrying the gene for brain-derived neurotrophic factor (BDNF) could be used to promote an axonal regenerative response in rubrospinal neurons after an acute cervical spinal cord injury. Summary of Background Data. Following axotomy in the cervical spinal cord, rubrospinal neurons undergo severe atrophy and fail to up-regulate important genes for regeneration. This can be attenuated or reversed with the infusion of BDNF to the injured cell bodies. This infusion technique, however, causes substantial parenchymal damage around the red nucleus and is limited by occlusion of the infusion pumps. This study examined whether viral vectors could be used to deliver the BDNF gene in a less damaging fashion and whether this could promote a regenerative response in injured rubrospinal neurons. Methods. Following a cervical spinal cord injury, the viral vectors were injected into the vicinity of the injured red nucleus. The extent of parenchymal damage around the red nucleus was assessed, as was the immunoreactivity to BDNF and cellular transfection patterns. Rubrospinal neuronal cross-ectional area was measured to determine if atrophy had been reversed, and in situ hybridization for GAP-43 and T alpha 1 tubulin was performed to determine if there genes, which are important for axonal regeneration, were up-regulated. Results. Parenchymal damage associated with viral injection was significantly less than with previous infusion techniques. BDNF immunoreactivity around the red nucleus indicated that the BDNF transgene was expressed. Both viral vectors reversed rubrospinal neuronal atrophy and promoted the expression of GAP-43 and T alpha 1 tubulin. Conclusions. Viral-ediated transfer of the BDNF gene was successful at promoting a regenerative response in rubrospinal neurons following acute cervical spinal cord injury, with significantly less parenchymal damage than previously observed when infusing the BDNF protein.