Combining Peripheral Nerve Grafting and Matrix Modulation to Repair the Injured Rat Spinal Cord

Abstract

Traumatic injury to the spinal cord (SCI) causes death of neurons, disruption of motor and sensory nerve fiber (axon) pathways and disruption of communication with the brain. One of the goals of our research is to promote axon regeneration to restore connectivity across the lesion site. To accomplish this we developed a peripheral nerve (PN) grafting technique where segments of sciatic nerve are either placed directly between the damaged ends of the spinal cord or are used to form a bridge across the lesion. There are several advantages to this approach compared to transplantation of other neural tissues; regenerating axons can be directed towards a specific target area, the number and source of regenerating axons is easily determined by tracing techniques, the graft can be used for electrophysiological experiments to measure functional recovery associated with axons in the graft, and it is possible to use an autologous nerve to reduce the possibility of graft rejection. In our lab we have performed both autologous (donor and recipient are the same animal) and heterologous (donor and recipient are different animals) grafts with comparable results. This approach has been used successfully in both acute and chronic injury situations. Regenerated axons that reach the distal end of the PN graft often fail to extend back into the spinal cord, so we use microinjections of chondroitinase to degrade inhibitory molecules associated with the scar tissue surrounding the area of SCI. At the same time we have found that providing exogenous growth and trophic molecules encourages longer distance axonal regrowth into the spinal cord. Several months after transplantation we perform a variety of anatomical, behavioral and electrophysiological tests to evaluate the recovery of function in our spinal cord injured animals. This experimental approach has been used successfully in several spinal cord injury models, at different levels of injury and in different species (mouse, rat and cat). Importantly, the peripheral nerve grafting approach is effective in promoting regeneration by acute and chronically injured neurons. The surgical station needs to be clean and sanitized with a dilute bleach solution prior to setting out instruments and accessory materials. Instruments will be autoclaved 1 day prior to surgery and stored in a sterile container. Turn on the Hot Bead Sterilizer (Fine Science Tools) used to remove pathogens and microbial contaminants from instruments between procedures on different animals. 2. Plug in the thermal barrier used to maintain body temperature during the surgical procedure. Set out cotton swabs and gauze pads used to control bleeding. Prepare small (< 2mm 3 ) pieces of Gel Foam to be used for micro-hemostasis and immerse in a sterile saline solution. 3. Place rat in an induction chamber and anesthetize with Isoflurane (5% vaporized in oxygen, flow rate 2.0 L/min). Remove animal from chamber to preparation table and shave a wide area of fur from the intended surgical field. Wipe with 70% isopropyl al...

Intraspinal AAV Injections Immediately Rostral to a Thoracic Spinal Cord Injury Site Efficiently Transduces Neurons in Spinal Cord and Brain

“…Our labuses a well-established grafting model in which segments of peripheral nerve are transplanted to fill the lesion cavity with a growth-supportive environment. 42 Some axonal tracts, including the populations that we found to be well-transduced in this study (e.g., reticulospinal, vestibulospinal, rubrospinal, and propriospinal pathways) regenerate fairly well into these peripheral nerve grafts. 43 A significant challenge has proven to be getting axons to emerge from the graft to reinnervate spinal cord tissue.…”

Cell Transplantation for Spinal Cord Injury: A Systematic Review

“…When transplanted these injured neurons from the spinal cord lesion site are transplanted into a peripheral neural environment, they can completely recover as normal neurons electrophysiologically and morphologically [183]. The Grafted peripheral nerve segments in the spinal cord were reported to be capable of improving the recovery of behavioral and electrophysiological function in vivo , via axons regeneration, reformation of functional synapses with host neurons, neurotrophic molecule secretion, and by providing a permissive PNS-like environment providing [184, 185] (Table 5). Schwann cells (SCs), the myelinating cells of the PNS, play important roles in postinjury nerve regeneration by contributing to the axon regeneration and remyelination and forming guidance bands, bands of Büngner, for regenerating axons [186].…”

Injured mice at the gym: Review, results and considerations for combining chondroitinase and locomotor exercise to enhance recovery after spinal cord injury

“…A wide range of promising therapies directed at preventing secondary injury and repairing the spinal cord at the site of injury have been shown to exert improvements in neuroprotection, regeneration, and/or recovery of function in animal models of SCI (rev. in [2–6]). These include single therapies, such as cell transplantation [7–10], neurotrophic factor infusion or overexpression [11–13], anti-inflammatory therapies [14–20] or administration of anti-growth inhibitory antibodies [21–23].…”