The incorporation of growth factor and chondroitinase ABC into an electrospun scaffold to promote axon regrowth following spinal cord injury.

Spinal cord injury results in tissue necrosis in and around the lesion site, commonly leading to the formation of a fluid-filled cyst. This pathological end point represents a physical gap that impedes axonal regeneration. To overcome the obstacle of the cavity, we have explored the extent to which axonal substrates can be bioengineered through electrospinning, a process that uses an electrical field to produce fine fibres of synthetic or biological molecules. Recently, we demonstrated the potential of electrospinning to generate an aligned matrix that can influence the directionality and growth of axons. Here, we show that this matrix can be supplemented with nerve growth factor and chondroitinase ABC to provide trophic support and neutralize glial-derived inhibitory proteins. Moreover, we show how air-gap electrospinning can be used to generate a cylindrical matrix that matches the shape of the cord. Upon implantation in a completely transected rat spinal cord, matrices supplemented with NGF and chondroitinase ABC promote significant functional recovery. An examination of these matrices post-implantation shows that electrospun aligned monofilaments induce a more robust cellular infiltration than unaligned monofilaments. Further, a vascular network is generated in these matrices, with some endothelial cells using the electrospun fibres as a growth substrate. The presence of axons within these implanted matrices demonstrates that they facilitate axon regeneration following spinal cord injury. Collectively, these results demonstrate the potential of electrospinning to generate an aligned substrate that can provide trophic support, directional guidance cues and regeneration-inhibitory neutralizing compounds to regenerating axons following spinal cord injury. Copyright © 2016 John Wiley & Sons, Ltd.

Neuroprotective effects of perflurocarbon (oxycyte) after contusive spinal cord injury.

Spinal cord injury (SCI) often results in irreversible and permanent neurological deficits and long-term disability. Vasospasm, hemorrhage, and loss of microvessels create an ischemic environment at the site of contusive or compressive SCI and initiate the secondary injury cascades leading to progressive tissue damage and severely decreased functional outcome. Although the initial mechanical destructive events cannot be reversed, secondary injury damage occurs over several hours to weeks, a time frame during which therapeutic intervention could be achieved. One essential component of secondary injury cascade is the reduction in spinal cord blood flow with resultant decrease in oxygen delivery. Our group has recently shown that administration of fluorocarbon (Oxycyte) significantly increased parenchymal tissue oxygen levels during the usual postinjury hypoxic phase, and fluorocarbon has been shown to be effective in stroke and head injury. In the current study, we assessed the beneficial effects of Oxycyte after a moderate-to-severe contusion SCI was simulated in adult Long-Evans hooded rats. Histopathology and immunohistochemical analysis showed that the administration of 5 mL/kg of Oxycyte perfluorocarbon (60% emulsion) after SCI dramatically reduced destruction of spinal cord anatomy and resulted in a marked decrease of lesion area, less cell death, and greater white matter sparing at 7 and 42 days postinjury. Terminal deoxynucleotidyl transferase dUTP nick end labeling staining showed a significant reduced number of apoptotic cells in Oxycyte-treated animals, compared to the saline group. Collectively, these results demonstrate the potential neuroprotective effect of Oxycyte treatment after SCI, and its beneficial effects may be, in part, a result of reducing apoptotic cell death and tissue sparing. Further studies to determine the most efficacious Oxycyte dose and its mechanisms of protection are warranted.

Two pole air gap electrospinning: Fabrication of highly aligned, three-dimensional scaffolds for nerve reconstruction.

We describe the structural and functional properties of three-dimensional (3D) nerve guides fabricated from poly-ε-caprolactone (PCL) using the air gap electrospinning process. This process makes it possible to deposit nano-to-micron diameter fibers into linear bundles that are aligned in parallel with the long axis of a cylindrical construct. By varying starting electrospinning conditions it is possible to modulate scaffold material properties and void space volume. The architecture of these constructs provides thousands of potential channels to direct axon growth. In cell culture functional assays, scaffolds composed of individual PCL fibers ranging from 400 to 1500 nm supported the penetration and growth of axons from rat dorsal root ganglion. To test the efficacy of our guide design we reconstructed 10mm lesions in the rodent sciatic nerve with scaffolds that had fibers 1 µm in average diameter and void volumes >90%. Seven weeks post implantation, microscopic examination of the regenerating tissue revealed dense, parallel arrays of myelinated and non-myelinated axons. Functional blood vessels were scattered throughout the implant. We speculate that end organ targeting might be improved in nerve injuries if axons can be directed to regenerate along specific tissue planes by a guide composed of 3D fiber arrays.

FTY720 reduces inflammation and promotes functional recovery after spinal cord injury.

A robust and complex inflammatory cascade is known to be a prominent component of secondary injury following spinal cord injury (SCI). Specifically, the concept of trauma-induced autoimmunity has linked the lymphocyte population with neural tissue injury and neurologic deficit. FTY720, a sphingosine receptor modulator that sequesters lymphocytes in secondary lymphoid organs, has been shown to be effective in the treatment of a variety of experimental autoimmune disorders. Accordingly, by reducing lymphocyte infiltration into the spinal cord following SCI, this novel immunomodulator may enhance tissue preservation and functional recovery. In the present study, a moderate to severe contusion SCI was simulated in adult Long-Evans hooded rats. Using flow cytometry we showed that daily FTY720 treatment dramatically reduced T-cell infiltration into the SCI lesion site at 4 and 7 days post-injury, while other inflammatory cell populations were relatively unaltered. To assess functional recovery, three groups of injured animals (treated, vehicle, and injury only) were evaluated weekly for hindlimb recovery. Animals in the treated group consistently exhibited higher functional scores than animals in the control groups after 2 weeks post-injury. This finding was associated with a greater degree of white matter sparing at the lesion epicenter when cords were later sectioned and stained. Furthermore, treated animals were found to exhibit improved bladder function and a reduced incidence of hemorrhagic cystitis compared to control counterparts. Collectively these results demonstrate the neuroprotective potential of FTY720 treatment after experimental SCI.

Reduction of hypoxia by perfluorocarbon emulsion in a traumatic spinal cord injury model.

OBJECT: Few therapies have consistently demonstrated effectiveness in preserving O2 delivery after spinal cord injury (SCI). Perfluorocarbons (PFCs) offer great promise to carry and deliver O2 more efficiently than conventional measures. The authors investigated the use of Clark-type microelectrodes to monitor spinal cord oxygenation directly (intraparenchymal [IP] recording) and indirectly (cerebrospinal fluid [CSF] recording) in the context of SCI, O2 therapy, and PFC treatment. METHODS: After placement of a subdural/CSF Licox probe in rats, incremental increases in the fraction of inspired O2 (FiO2) up to 100% were administered to establish a dose-response curve. The probe was then placed in the parenchyma of the same animals for a second dose-response curve. In a second study, rats with CSF or IP probes underwent SCI with the NYU Impactor and treatment with O2, followed by administration of PFC, or saline in the control group. RESULTS: All animals in the first experiment responded to the FiO2 dose increase, with changes in PO2 evident in both CSF and IP levels. The SCI in the second experiment caused a marked drop in PO2 from a mean of 21.4 to 10.4 mm Hg, with most animals dropping to less than half their preinjury value. All animals responded to 100% O2 treatment. Every animal that received PFCs showed significant improvement, with a mean increase in PO2 of 23.3 mm Hg. Only 1 saline-treated animal showed any benefit. Oxygen values in the PFC treatment group reached up to 6 times the normal level. CONCLUSIONS: Oxygen levels in SCI show a profound drop almost immediately postinjury. Administration of PFCs combined with 100% O2 therapy can reverse tissue hypoxia and holds promise for reducing ischemic injury.

Titanium miniplates or stainless steel wire for cranial fixation: a prospective randomized comparison.

OBJECT: The authors designed a study to compare low-profile titanium miniplate fixation to that in which stainless steel wire is used. METHODS: Before undergoing craniotomy, 40 patients gave informed consent and were randomized to receive either wire or miniplate fixation. After dural closure, bone flap fixation was timed. The bone flap was measured for inward or outward offset and mobility to manual pressure on its margin. Three months postoperatively the bone flap margins were graded for appearance or palpation of an offset and for the presence of burr hole depressions. Twenty-four patients were randomized to receive miniplate fixation and 16 to receive stainless steel wire fixation. The time required for wire fixation was approximately 40% longer than that for miniplates (11.8 +/- 5.1 minutes compared with 8.3 +/- 5 minutes, p = 0.02). The offset of bone flaps after wire fixation was significantly greater than that with miniplates (1.6 +/- 1 mm compared with 0.3 +/- 0.6 mm, p < 0.001), as was the mobility of the bone flap on digital pressure (1.2 +/- 0.9 mm compared with 0.2 +/- 0.5 mm, p < 0.001). At the 3-month follow-up review, two of 12 patients had suboptimal results after wire fixation, whereas none of 14 patients had suboptimal results after miniplate fixation. When dichotomized for excellent or less-than-excellent postoperative results, the data were significantly better for patients who underwent miniplate fixation (p < 0.05). CONCLUSIONS: Titanium miniplate cranial fixation provides more accurate and rigid reapproximation of the bone edges, with results that are significantly better on close inspection or palpation. The additional cost of miniplate fixation may thus be justified in many cases.