Ex Vivo Adenoviral Vector-Mediated Neurotrophin Gene Transfer to Olfactory Ensheathing Glia: Effects on Rubrospinal Tract Regeneration, Lesion Size, and Functional Recovery after Implantation in the Injured Rat Spinal Cord

Abstract

The present study uniquely combines olfactory ensheathing glia (OEG) implantation with ex vivo adenoviral (AdV) vector-based neurotrophin gene therapy in an attempt to enhance regeneration after cervical spinal cord injury. Primary OEG were transduced with AdV vectors encoding rat brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), or bacterial marker protein beta-galactosidase (LacZ) and subsequently implanted into adult Fischer rats directly after unilateral transection of the dorsolateral funiculus. Implanted animals received a total of 2 x 105 OEG that were subjected to transduction with neurotrophin-encoding AdV vector, AdV-LacZ, or no vector, respectively. At 4 months after injury, lesion volumes were smaller in all OEG implanted rats and significantly reduced in size after implantation of neurotrophin-encoding AdV vector-transduced OEG. All OEG grafts were filled with neurofilament-positive axons, and AdV vector-mediated expression of BDNF by implanted cells significantly enhanced regenerative sprouting of the rubrospinal tract. Behavioral analysis revealed that OEG-implanted rats displayed better locomotion during horizontal rope walking than unimplanted lesioned controls. Recovery of hind limb function was also improved after implantation of OEG that were transduced with a BDNF- or NT-3-encoding AdV vector. Hind limb performance during horizontal rope locomotion did directly correlate with lesion size, suggesting that neuroprotective effects of OEG implants contributed to the level of functional recovery. Thus, our results demonstrate that genetic engineering of OEG not only resulted in a cell that was more effective in promoting axonal outgrowth but could also lead to enhanced recovery after injury, possibly by sparing of spinal tissue.

A Systematic Review of Cellular Transplantation Therapies for Spinal Cord Injury

“…or corticospinal axons across and beyond the lesion site was also not found in the studies using olfactory bulb derived OECs from adult rats (Deumens et al, 2006;Ruitenberg et al, 2003) or with OECs from the mucosa of newborn mice (Bretzner et al, 2008;. Behavioral benefits were seen when the adult bulb-derived OECs were transfected to express BDNF=NT-3 (Ruitenberg et al, 2003).…”

Targeting Sensory Axon Regeneration in Adult Spinal Cord

“…The administration of neurotrophin alone or in combination with other proregenerative compounds has been shown to dramatically improve regeneration after spinal cord injury (Coumans et al, 2001;Romero et al, 2001;Ruitenberg et al, 2003;Lu et al, 2004); however, these molecules are not effective at targeting axon. Any strategy to promote regeneration at best only supports the regeneration of a small percentage of lesioned axons and show little functional recovery.…”

Rapid recovery of segmental neurological function in a tetraplegic patient following transplantation of fetal olfactory bulb-derived cells

“…37 Neonatal rodent OECs release nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) into culture media 38 but adult rodent OECs release negligible quantities of BNDF into culture media. 39 Exogenous NGF and BDNF have been shown to enhance glutamatergic neurotransmission in the brain 40 by both pre-and postsynaptic mechanisms 41 and to induce formation of new synapses. 42 In addition, NGF can influence expression of Na þ and Ca 2 þ channels on neurons in culture.…”