Muscle Injection of Aav-Nt3 Promotes Anatomical Reorganization of CST Axons and Improves Behavioral Outcome Following Sci

Abstract

Here we propose the use of adeno-associated virus (AAV) vectors as a non-invasive vehicle for the nervous system to deliver genes to spinal motoneurons, based on their retrograde transport from muscle. Long-term protein expression in lower cervical motoneurons was achieved after injections of AAV into the triceps, independently of serotypes 1, 2, or 5. Muscle injections of AAV5-neurotrophin 3 (NT3) resulted in a significant increase in the levels of NT3 in the cervical enlargement, compared to those obtained after injections of AAV5-GFP. Following a dorsal lesion at C4/C5, animals injected with AAV5-NT3 made fewer errors (footslips) in the horizontal ladder test compared to those injected with AAV5-GFP. In parallel, the number and length of corticospinal tract (CST) fibers circumventing the injury site were significantly increased in rats injected with AAV5-NT3. Compared to controls, we observed less astrogliosis and less CST axonal retraction and/or enhanced sprouting in animals injected with AAV5-NT3. In sum, we demonstrate here that the delivery of nt3 via retrograde transport of AAV from triceps to cervical motoneurons leads to reduced functional loss and anatomical reorganization of the CST following injury, without introducing additional injury to the spinal cord.

Spinal electro-magnetic stimulation combined with transgene delivery of neurotrophin NT-3 and exercise: novel combination therapy for spinal contusion injury

“…AAV serotype rh10 encoding the neurotrophin NT3 gene and coexpressing GFP under the cytomegalovirus (CMV) promoter (AAVrh10.CMV.bGHint.NT3.IRES.eGFP.WPRE.bGH) using a 1.17 ϫ 10 13 genomic copy (GC)/ml dosage or control AAV vector encoding the GFP gene under the CMV promoter (AAVrh10.CMV.PI.eGFP.WPRE.bGH) using a 3.99 ϫ 10 13 GC/ml dosage was used for this study. AAV-mediated gene transfer has been used for safe and prolonged delivery of NT3 in injured spinal cord (Blits et al 2003;Boyce et al 2012;Fortun et al 2009;. The procedure for intraspinal injections of AAV-NT3 has been described before Petrosyan et al 2014a).…”

“…The major goal was to examine whether chronic administration of repetitive sEMS (every other day for 5 wk) and exercise training applied alone, together, and in combination with NT3 would improve transmission and recovery of function following thoracic contusion SCI. Based on our recent results, demonstrating robust transduction of both neuronal and glial cell populations in injured spinal cord (Petrosyan et al 2014a), we used recombinant human adeno-associated viral 10 (AAV-rh10) vector for transgene delivery of NT3, which is an improved strategy from our previous study to increase levels of neurotrophins in the spinal cord of animals with SCI (Blits et al 2003;Boyce et al 2012;Fortun et al 2009;Hunanyan et al 2013). Furthermore, we systematically compared the motor-evoked potentials (MEPs) and synaptic responses recorded from individual motoneurons following contusive SCI and above-mentioned interventions.…”

Plasticity After Spinal Cord Injury: Relevance to Recovery and Approaches to Facilitate It

“…It has the added advantage of being endocytosed at nerve terminals, so it is less invasive than adenovirus for inducing transgene expression in spinal cord motoneurons [112,113]. Using this method, NT-3 motoneuron expression induced sprouting of corticospinal tract axons after cervical dorsal column lesions and limited functional recovery of foot placement [114].…”

Transduction efficiency of neurons and glial cells by AAV-1, -5, -9, -rh10 and -hu11 serotypes in rat spinal cord following contusion injury

“…[30][31][32][33][34][35][36] Among several animal models of SCI, adult rat contusion models have been established as exhibiting a striking similarity to most human spinal trauma. 37 However, transduction efficacy and cellular tropism of different AAV vectors in the damaged spinal cord have not been systematically examined following contusion SCI.…”