Experimental strategies to promote spinal cord regeneration--an integrative perspective

Biomarkers for severity of spinal cord injury in the cerebrospinal fluid of rats

One of the major challenges in management of spinal cord injury (SCI) is that the assessment of injury severity is often imprecise. Identification of reliable, easily quantifiable biomarkers that delineate the severity of the initial injury and that have prognostic value for the degree of functional recovery would significantly aid the clinician in the choice of potential treatments. To find such biomarkers we performed quantitative liquid chromatography-mass spectrometry (LC-MS/MS) analyses of cerebrospinal fluid (CSF) collected from rats 24 h after either a moderate or severe SCI. We identified a panel of 42 putative biomarkers of SCI, 10 of which represent potential biomarkers of SCI severity. Three of the candidate biomarkers, Ywhaz, Itih4, and Gpx3 were also validated by Western blot in a biological replicate of the injury. The putative biomarkers identified in this study may potentially be a valuable tool in the assessment of the extent of spinal cord damage.

Cell cycle activation and spinal cord injury

Traumatic spinal cord injury (SCI) evokes a complex cascade of events with initial mechanical damage leading to secondary injury processes that contribute to further tissue loss and functional impairment. Growing evidence suggests that the cell cycle is activated following SCI. Up-regulation of cell cycle proteins after injury appears to contribute not only to apoptotic cell death of postmitotic cells, including neurons and oligodendrocytes, but also to post-traumatic gliosis and microglial activation. Inhibition of key cell cycle regulatory pathways reduces injury-induced cell death, as well as microglial and astroglial proliferation both in vitro and in vivo. Treatment with cell cycle inhibitors in rodent SCI models prevents neuronal cell death and reduces inflammation, as well as the surrounding glial scar, resulting in markedly reduced lesion volumes and improved motor recovery. Here we review the effects of SCI on cell cycle pathways, as well as the therapeutic potential and mechanism of action of cell cycle inhibitors for this disorder.

The effect of minocycline on motor neuron recovery and neuropathic pain in a rat model of spinal cord injury

OBJECTIVE

Minocycline, a second-generation tetracycline-class antibiotic, has been well established to exert a neuroprotective effect in animal models and neurodegenerative disease through the inhibition of microglia. Here, we investigated the effects of minocycline on motor recovery and neuropathic pain in a rat model of spinal cord injury.

METHODS

To simulate spinal cord injury, the rats' spinal cords were hemisected at the 10th thoracic level (T10). Minocycline was injected intraperitoneally, and was administered 30 minutes prior surgery and every second postoperative day until sacrifice 28 days after surgery. Motor recovery was assessed via the Basso-Beattie-Bresnahan test. Mechanical hyperalgesia was measured throughout the 28-day post-operative course via the von Frey test. Microglial and astrocyte activation was assessed by immunohistochemical staining for ionized calcium binding adaptor molecule 1 (Iba1) and glial fibrillary acidic protein (GFAP) at two sites: at the level of hemisection and at the 5th lumbar level (L5).

RESULTS

In rats, spinal cord hemisection reduced locomotor function and induced a mechanical hyperalgesia of the ipsilateral hind limb. The expression of Iba1 and GFAP was also increased in the dorsal and ventral horns of the spinal cord at the site of hemisection and at the L5 level. Intraperitoneal injection of minocycline facilitated overall motor recovery and attenuated mechanical hyperalgesia. The expression of Iba1 and GFAP in the spinal cord was also reduced in rats treated with minocycline.

CONCLUSION

By inhibiting microglia and astrocyte activation, minocycline may facilitate motor recovery and attenuate mechanical hyperalgesia in individuals with spinal cord injuries.

Implantation of adult bone marrow-derived mesenchymal stem cells transfected with the neurotrophin-3 gene and pretreated with retinoic acid in completely transected spinal cord

Implantation of marrow-derived mesenchymal stem cells (MSCs) is the most promising therapeutic strategy for the treatment of spinal cord injury (SCI), especially because of their potential for clinical application, such as the avoidance of immunologic rejection, their strong secretory properties, and their plasticity for developing into neural cells. However, the recovery from SCI after MSC implantation is minimal due to their limited capacity for the reduction of cystic cavitation, for the axonal regeneration and their uncertain neural plasticity in the spinal cord. We previously pretreated MSCs with all-trans retinoic acid (RA) in vitro. Then we genetically modified them to overexpress neurotrophin-3 (NT-3) via a recombinant adenoviral vector (Adv). This combined treatment not only permitted more neuronal differentiation of MSCs, but stimulated more NT-3 secretion prior to grafting, according to our previous and present results. When these cells were implanted into the transected spinal cord of rats, the animals had some improvement (both functionally and structurally), including the recovery of hindlimb locomotor function, shown by the highest Basso, Beattie, and Bresnahan (BBB) scores, as well as dramatically reduced cavity volume, clear axonal regeneration and more neuronal survival. In contrast, simple MSC implantation is not a very effective therapy for spinal transection. However, the neuronal differentiation of MSCs after treatment with a combination of Adv-mediated NT-3 gene transfer and RA was only mildly improved in vivo.

Developmental changes of gene expression after spinal cord injury in neonatal opossums

Changes in gene expression have been measured 24h after injury to mammalian spinal cords that can and cannot regenerate. In opossums there is a critical period of development when regeneration stops being possible: at 9 days postnatal cervical spinal cords regenerate, at 12 days they do not. By the use of marsupial cDNA microarrays, we detected 158 genes that respond differentially to injury at the two ages critical for regeneration. For selected candidates additional measurements were made by real-time PCR and sites of their expression were shown by immunostaining. Candidate genes have been classified so as to select those that promote or prevent regeneration. Up-regulated by injury at 8 days and/or down-regulated by injury at 13 days were genes known to promote growth, such as Mitogen-activated protein kinase kinase 1 or transcription factor TCF7L2. By contrast, at 13 days, up-regulation occurred of inhibitory molecules, including annexins, ephrins, and genes related to apoptosis and neurodegenerative diseases. Certain genes such as calmodulin 1 and NOGO, changed expression similarly in animals that could and could not regenerate without any additional changes in response to injury. These findings confirmed and extended changes of gene expression found in earlier screens on 9 and 12 ay preparations without lesions and provide a comprehensive list of genes that serve as a basis for testing how identified molecules, singly or in combination, promote and prevent central nervous system regeneration.

Beneficial effect of the traditional chinese drug shu-xue-tong on recovery of spinal cord injury in the rat

Shu-Xue-Tong (SXT) is a traditional Chinese drug widely used to ameliorate stagnation of blood flow, such as brain or myocardial infarction. Whether SXT may have therapeutic value for spinal cord injury (SCI), during which ischemia plays an important role in its pathology, remains to be elucidated. We hypothesized that SXT may promote SCI healing by improving spinal cord blood flow (SCBF), and a study was thus designed to explore this possibility. Twenty-five male Sprague-Dawley rats were used. SCI was induced by compression, and SXT was administrated 24 h postinjury for 14 successive days. The effects of SXT were assessed by means of laser-Doppler flowmetry, motor functional analysis (open-field walking and footprint analysis), and histological analysis (hematoxylin-eosin and thionin staining and NeuN immunohistochemistry). SXT significantly promoted SCBF of the contused spinal cord and enhanced the recovery of motor function. Histological analysis indicated that the lesion size was reduced, the pathological changes were ameliorated, and more neurons were preserved. Based on these results we conclude that SXT can effectively improve SCI.

Human mesenchymal stem cell-derived Schwann cell-like cells exhibit neurotrophic effects, via distinct growth factor production, in a model of spinal cord injury

Human bone marrow-derived mesenchymal stem cells (hMSCs) are considered a desirable cell source for autologous cell transplantation therapy to treat nervous system injury due to their ability to differentiate into specific cell types and render the tissue microenvironment more favorable for tissue repair by secreting various growth factors. To potentiate their possible trophic effect, hMSCs were induced without genetic modification to adopt characteristics of Schwann cells (SCs), which provide trophic support for regenerating axons. The induced hMSCs (shMSCs) adopted a SC-like morphology and expressed SC-specific proteins including the p75 neurotrophin receptor, which correlated with cell-cycle exit. In addition, shMSCs secreted higher amounts of several growth factors, such as hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF) when compared with uninduced hMSCs. Coculture of shMSCs with Neuro2A cells significantly increased neurite outgrowth and cell proliferation but decreased cell death. Transplantation of shMSCs in an ex vivo model of spinal cord injury dramatically enhanced axonal outgrowth, which was mediated by HGF and VEGF secretion and also decreased cell death. These results demonstrate that shMSCs could serve as an endogenous source of neurotrophic growth factors to facilitate axonal regeneration while at the same time protecting the resident cells at the site of tissue injury. We propose that these induced hMSCs without genetic modification are useful for autologous cell therapy to treat nervous system injury.

Glial scar and neuroregeneration: histological, functional, and magnetic resonance imaging analysis in chronic spinal cord injury

Object

A glial scar is thought to be responsible for halting neuroregeneration following spinal cord injury (SCI). However, little quantitative evidence has been provided to show the relationship of a glial scar and axonal regrowth after injury.

Methods

In this study performed in rats and dogs, a traumatic SCI model was made using a weight-drop injury device, and tissue sections were stained with H & E for immunohistochemical analysis. The function and behavior of model animals were tested using electrophysiological recording and the Basso-Beattie-Bresnahan Locomotor Rating Scale, respectively. The cavity in the spinal cord after SCI in dogs was observed using MR imaging.

Results

The morphological results showed that the formation of an astroglial scar was defined at 4 weeks after SCI. While regenerative axons reached the vicinity of the lesion site, the glial scar blocked the extension of regrown axons. In agreement with these findings, the electrophysiological, behavioral, and in vivo MR imaging tests showed that functional recovery reached a plateau at 4 weeks after SCI. The thickness of the glial scars in the injured rat spinal cords was also measured. The mean thickness of the glial scar rostral and caudal to the lesion cavity was 107.00 ± 20.12 μm; laterally it was 69.92 ± 15.12 μm.

Conclusions

These results provide comprehensive evidence indicating that the formation of a glial scar inhibits axonal regeneration at 4 weeks after SCI. This study reveals a critical time window of postinjury recovery and a detailed spatial orientation of glial scar, which would provide an important basis for the development of therapeutic strategy for glial scar ablation.

Peripheral nerve grafts after cervical spinal cord injury in adult cats

Peripheral nerve grafts (PNG) into the rat spinal cord support axon regeneration after acute or chronic injury, with synaptic reconnection across the lesion site and some level of behavioral recovery. Here, we grafted a peripheral nerve into the injured spinal cord of cats as a preclinical treatment approach to promote regeneration for eventual translational use. Adult female cats received a partial hemisection lesion at the cervical level (C7) and immediate apposition of an autologous tibial nerve segment to the lesion site. Five weeks later, a dorsal quadrant lesion was performed caudally (T1), the lesion site treated with chondroitinase ABC 2 days later to digest growth inhibiting extracellular matrix molecules, and the distal end of the PNG apposed to the injury site. After 4-20 weeks, the grafts survived in 10/12 animals with several thousand myelinated axons present in each graft. The distal end of 9/10 grafts was well apposed to the spinal cord and numerous axons extended beyond the lesion site. Intraspinal stimulation evoked compound action potentials in the graft with an appropriate latency illustrating normal axonal conduction of the regenerated axons. Although stimulation of the PNG failed to elicit responses in the spinal cord distal to the lesion site, the presence of c-Fos immunoreactive neurons close to the distal apposition site indicates that regenerated axons formed functional synapses with host neurons. This study demonstrates the successful application of a nerve grafting approach to promote regeneration after spinal cord injury in a non-rodent, large animal model.

Predifferentiated embryonic stem cells promote functional recovery after spinal cord compressive injury

We tested the effects of mouse embryonic stem cells (mES) grafts in mice spinal cord injury (SCI). Young adult female C57/Bl6 mice were subjected to laminectomy at T9 and 1-minute compression of the spinal cord with a vascular clip. Four groups were analyzed: laminectomy (Sham), injured (SCI), vehicle (DMEM), and mES-treated (EST). mES pre-differentiated with retinoic acid were injected (8 x 10(5) cells/2 microl) into the lesion epicenter, 10 min after SCI. Basso mouse scale (BMS) and Global mobility test (GMT) were assessed weekly up to 8 weeks, when morphological analyses were performed. GMT analysis showed that EST animals moved faster (10.73+/-0.9076, +/-SEM) than SCI (5.581+/-0.2905) and DMEM (5.705+/-0.2848), but slower than Sham animals (15.80+/-0.3887, p<0.001). By BMS, EST animals reached the final phase of locomotor recovery (3.872+/-0.7112, p<0.01), while animals of the SCI and DMEM groups improved to an intermediate phase (2.037+/-0.3994 and 2.111+/-0.3889, respectively). White matter area and number of myelinated nerve fibers were greater in EST (46.80+/-1.24 and 279.4+/-16.33, respectively) than the SCI group (39.97+/-0.925 and 81.39+/-8.078, p<0.05, respectively). EST group also presented better G-ratio values when compared with SCI group (p<0.001). Immunohistochemical revealed the differentiation of transplanted cells into astrocytes, oligodendrocytes, and Schwann cells, indicating an integration of transplanted cells with host tissue. Ultrastructural analysis showed, in the EST group, better tissue preservation and more remyelination by oligodendrocytes and Schwann cells than the other groups. Our results indicate that acute transplantation of predifferentiated mES into the injured spinal cord increased the spared white matter and number of nerve fibers, improving locomotor function.

Expression of a dominant-negative Rho-kinase promotes neurite outgrowth in a microenvironment mimicking injured central nervous system

AIM

To investigate whether lentiviral vector (LV)-mediated expression of a dominant negative mutant Rho-kinase (DNROCK) could inhibit activation of the Rho/ROCK signaling pathway and promote neurite outgrowth in a hostile microenvironment mimicking the injured central nervous system (CNS) in vitro.

METHODS

Lentiviral stock was produced using the three-plasmid system by transfecting HEK293 cells. Myelin prepared from rat brain was purified by two rounds of discontinuous density gradient centrifugation and osmotic disintegration. Differentiated PC12 cells and dissociated adult rat dorsal root ganglion (DRG) neurons were transduced with either LV/DNROCK or LV/green fluorescent protein (GFP) and seeded on solubilized myelin proteins. The effect of DNROCK on growth cone morphology was tested by rhodamine-conjugated phalloidin staining. Expression of DNROCK was determined by immunoblotting. The length of the longest neurite, the percentage of neurite-bearing neurons, or the total process outgrowth for all transduced neurons were measured by using the Scion image analysis program.

RESULTS

Transduction of DNROCK inhibited serum-induced stress fiber formation in NIH 3T3 cells and induced enlargement of cell bodies and decreased the phosphorylation levels of MYPT1 in HeLa cells. LV/DNROCK blocked myelin-induced increase in ROCK translocation from cytosol to membrane in LV/GFP-treated PC12 cells. DNROCK promotes neurite outgrowth of differentiated PC12 cells and DRG neurons on myelin protein. LV/DNROCK-transduced PC12 cells had longer neurites than LV/GFP-transduced cells (39.18+/-2.19 microm vs 29.32+/-1.7 microm, P<0.01) on myelin-coated coverslips. Furthermore, a significantly higher percentage of LV/DNROCK-transduced cells had extended neurites than LV/GFP-transduced cells (63.75%+/-8.03% vs 16.3%+/-3.70%, P<0.01). LV/DNROCK-transduced DRG neurons had longer neurite length (325.22+/-10.8 microm vs 202.47+/-9.3 microm, P<0.01) and more primary neurites per cell than those in LV/GFP-transduced cells plated on myelin and laminin (7.8+/-1.25 vs 4.84+/-1.45, P<0.01) or on laminin alone (5.2+/-1.88). LV/DNROCK-transduced cells had significantly larger growth cones (33.12+/-1.06 microm(2)) than LV/GFP-pretreated cells (23.72+/-1.22 microm(2)).

CONCLUSION

These results indicate that blocking the RhoA/ROCK signaling pathway by expression of DNROCK is effective in facilitating neurite outgrowth in a microenvironment mimicking injury of central nervous system.

PEGylated interferon-beta modulates the acute inflammatory response and recovery when combined with forced exercise following cervical spinal contusion injury

Secondary degeneration leads to an expansion of the initial tissue damage sustained during a spinal cord injury (SCI). Dampening the cellular inflammatory response that contributes to this progressive tissue damage is one possible strategy for neuroprotection after acute SCI. We initially examined whether treatment with a PEGylated form of rat interferon-beta (IFN-beta) would modulate the expression of several markers of inflammation and neuroprotection at the site of a unilateral cervical level 5 contusion injury. Adult female Sprague-Dawley rats were injured using the Infinite Horizon Impactor at a force of 200 kdyn (equivalent to a severe injury) and a mean displacement of 1600-1800 mum. A single dose (5x10(6) units) of PEGylated IFN-beta or vehicle was administered 30 min following SCI. Here we demonstrate temporal changes in pro- and anti-inflammatory cytokine levels and the expression of heat shock proteins and iNOS (involved in neuroprotection) at the lesion epicenter and one segment caudally after SCI and PEG IFN-beta treatment. The results suggested a potential therapeutic treatment strategy for modulation of secondary damage after acute SCI. Therefore, we examined whether acute treatment with PEG IFN-beta would improve forelimb function alone or when combined with forced exercise (Ex). Animals began the Ex paradigm 5 days post SCI and continued for 5 days/week over 8 weeks. Locomotion (forelimb locomotor scale [FLS], hindlimb BBB, and TreadScan) and sensorimotor function (grid walking) was tested weekly. Additional outcome measures included lesion size and glial cell reactivity. Significant FLS improvements occurred at 1 week post SCI in the PEGylated IFN-beta-treated group but not at any other time point or with any other treatment approaches. These results suggest that this acute neuroprotective treatment strategy does not translate into long term behavioral recovery even when combined with forced exercise.

Selected combination of neurotrophins potentiate neuroprotection and functional recovery following spinal cord injury in the rat

The possibility that a combination of neurotrophins induces long-lasting neuroprotection of the cord following spinal cord injury (SCI) was examined in a rat model. The SCI was performed by making a unilateral incision into the right dorsal horn of the T10-11 segments and the animals were allowed to survive 5 h after trauma. Different combination of neurotrophins, i.e., BDNF in combination with GDNF, NT-3, or NGF was applied topically over the traumatized spinal cord and motor dysfunction, blood-spinal cord barrier (BSCB) breakdown, edema formation, and cell injury were examined. Topical application of BDNF in combination with GDNF and NGF 30 min (but not 60 or 90 min) at high concentrations (0.5 microg each) after SCI significantly improved motor function and reduced BSCB breakdown, edema formation, and cell injury at 5 h. However, concurrent application of BDNF, IGF-1, and GDNF (but not with NT-3 or NGF) even 60 or 90 min after trauma induced a significant reduction in motor dysfunction and spinal cord pathology. These observations suggest that a combination of neurotrophins may have added therapeutic value in the treatment of SCI, not reported earlier.

Dynamics of early locomotor network dysfunction following a focal lesion in an in vitro model of spinal injury

It is unclear how a localized spinal cord injury may acutely affect locomotor networks of segments initially spared by the lesion. To investigate the process of secondary damage following spinal injury, we used the in vitro model of the neonatal rat isolated spinal cord with transverse barriers at the low thoracic-upper lumbar region to allow focal application of kainate in hypoxic and aglycemic solution (with reactive oxygen species). The time-course and nature of changes in spinal locomotor networks downstream of the lesion site were investigated over the first 24 h, with electrophysiological recordings monitoring fictive locomotion (alternating oscillations between flexor and extensor motor pools on either side) and correlating any deficit with histological alterations. The toxic solution irreversibly suppressed synaptic transmission within barriers without blocking spinal reflexes outside. This effect was focally associated with extensive white matter damage and ventral gray neuronal loss. Although cell losses were < 10% outside barriers, microglial activation with neuronal phagocytosis was detected. Downstream motor networks still generated locomotor activity 24 h later when stimulated with N-methyl-d-aspartate (NMDA) and serotonin, but not with repeated dorsal root stimuli. In the latter case, cumulative depolarization was recorded from ventral roots at a slower rate of rise, suggesting failure to recruit network premotoneurons. Our data indicate that, within the first 24 h of injury, locomotor networks below the lesion remained morphologically intact and functional when stimulated by NMDA and serotonin. Nevertheless, microglial activation and inability to produce locomotor patterns by dorsal afferent stimuli suggest important challenges to long-term network operation.

O trauma raquimedular

A medula espinhal dos mamíferos adultos não permite a regeneração de axônios. Por razões ainda desconhecidas, as fibras neurais falham em cruzar o sítio da lesão, como se não houvesse crescimento, desde a primeira tentativa. Quais mecanismos poderiam explicar a perda da capacidade de regeneração? As cicatrizes formadas pelas células da glia seriam uma consequência da falha na regeneração ou a causa? Diversas linhas de evidência sugerem que a regeneração da medula espinhal seria impedida no sistema nervoso central pela ação de fatores locais no sítio da lesão, e que o sistema nervoso central não-lesado é um meio permissivo para o crescimento axonal, na direção de alvos específicos. Uma vez que os axônios são induzidos adequadamente a cruzar a lesão com o auxílio de implantes, fármacos ou células indiferenciadas, as fibras em regeneração podem encontrar a via específica e estabelecer conexões corretas. O que ainda não se sabe é que combinação de moléculas induz/inibe o potencial de regeneração do tecido e que mecanismos permitem aos neurônios formarem conexões específicas com os alvos com os quais são programados a fazer.

Anatomical and functional outcomes following a precise, graded, dorsal laceration spinal cord injury in C57BL/6 mice

To study the pathophysiology of spinal cord injury (SCI), we used the LISA-Vibraknife to generate a precise and reproducible dorsal laceration SCI in the mouse. The surgical procedure involved a T9 laminectomy, dural resection, and a spinal cord laceration to a precisely controlled depth. Four dorsal hemisection injuries with lesion depths of 0.5, 0.8, 1.1, and 1.4 mm, as well as normal, sham (laminectomy and dural removal only), and transection controls were examined. Assessments including the Basso Mouse Scale (BMS), footprint analysis, beam walk, toe spread reflex, Hargreaves' test, and transcranial magnetic motor-evoked potential (tcMMEP) analysis were performed to assess motor, sensorimotor, and sensory function. These outcome measures demonstrated significant increases in functional deficits as the depth of the lesion increased, and significant behavioral recovery was observed in the groups over time. Quantitative histological examination showed significant differences between the injury groups and insignificant lesion depth variance within each of the groups. Statistically significant differences were additionally found in the amount of ventral spared tissue at the lesion site between the injury groups. This novel, graded, reproducible laceration SCI model can be used in future studies to look more closely at underlying mechanisms that lead to functional deficits following SCI, as well as to determine the efficacy of therapeutic intervention strategies in the injury and recovery processes following SCI.

Chemokines as possible targets in modulation of the secondary damage after acute spinal cord injury: a review

In spite of many promising experimental studies, an effective treatment dramatically eliminating the secondary damage after spinal cord injury (SCI) is still missing. Since clinical data on the therapeutical effect after methylprednisolone treatment are not conclusive, new therapeutical modalities targeting specific components of secondary spinal cord damage needs to be developed. It is known that immune cells are recruited to injury sites by chemokines, which are small, structurally similar proteins released locally at the site of inflammation. Hence, this review was aimed to summarize possible roles of chemokines in the inflammation following SCI as well as to identify possible new therapeutical targets which can potentially be effective in ameliorating individual components of this inflammatory response. Data concerning inflammation reduction together with techniques improving axonal growth, cell replacement and remyelinization, may be crucial to move a small step forward in an attempt to make paraplegic and quadriplegic patients to walk.

Targeting a dominant negative rho kinase to neurons promotes axonal outgrowth and partial functional recovery after rat rubrospinal tract lesion

Many axonal growth inhibitors that contribute to the usual failure of axon regeneration in the central nervous system (CNS) exert their effects via the RhoA-Rho kinase (ROCK) signal pathway. In this study, we investigated whether lentiviral vector (LV)-mediated neuron-specific expression of a dominant negative mutant of ROCK (DNROCK) could promote axon outgrowth in vitro and in vivo. Dissociated adult rat dorsal root ganglion (DRG) neurons were seeded on solubilized myelin proteins and transduced with either LV/DNROCK or LV/green fluorescent protein (GFP). DNROCK-expressing neurons were shown to have a greater chance of generating neurites and a longer mean length of neurite than GFP-expressing neurons. In the in vivo studies, lentiviruses were injected into the adult rat red nucleus followed by unilateral rubrospinal tract (RST) transection at the fourth cervical level. Rats in the DNROCK group showed better functional recovery in the affected hindlimbs and forelimbs than those in the GFP group. Examination of the spinal cord sections revealed more rubrospinal axonal profiles growing to the spinal cord caudal to the lesion in the DNROCK group than in the GFP group. These results indicate that blocking the RhoA-ROCK signal pathway by expressing DNROCK can enhance regenerative axonal sprouting and lead to partial recovery of limb function.

Acute rolipram/thalidomide treatment improves tissue sparing and locomotion after experimental spinal cord injury

Traumatic spinal cord injury (SCI) causes severe and permanent functional deficits due to the primary mechanical insult followed by secondary tissue degeneration. The cascade of secondary degenerative events constitutes a range of therapeutic targets which, if successfully treated, could significantly ameliorate functional loss after traumatic SCI. During the early hours after injury, potent pro-inflammatory cytokines, including tumor necrosis factor alpha (TNF-alpha) and interleukin-1 beta (IL-1beta) are synthesized and released, playing key roles in secondary tissue degeneration. In the present investigation, the ability of rolipram and thalidomide (FDA approved drugs) to reduce secondary tissue degeneration and improve motor function was assessed in an experimental model of spinal cord contusion injury. The combined acute single intraperitoneal administration of both drugs attenuated TNF-alpha and IL-1beta production and improved white matter sparing at the lesion epicenter. This was accompanied by a significant (2.6 point) improvement in the BBB locomotor score by 6 weeks. There is, at present, no widely accepted intervention strategy that is appropriate for the early treatment of human SCI. The present data suggest that clinical trials for the acute combined application of rolipram and thalidomide may be warranted. The use of such "established drugs" could facilitate the early initiation of trials.

Ex vivo VEGF delivery by neural stem cells enhances proliferation of glial progenitors, angiogenesis, and tissue sparing after spinal cord injury

The present study was undertaken to examine multifaceted therapeutic effects of vascular endothelial growth factor (VEGF) in a rat spinal cord injury (SCI) model, focusing on its capability to stimulate proliferation of endogenous glial progenitor cells. Neural stem cells (NSCs) can be genetically modified to efficiently transfer therapeutic genes to diseased CNS. We adopted an ex vivo approach using immortalized human NSC line (F3 cells) to achieve stable and robust expression of VEGF in the injured spinal cord. Transplantation of NSCs retrovirally transduced to overexpress VEGF (F3.VEGF cells) at 7 days after contusive SCI markedly elevated the amount of VEGF in the injured spinal cord tissue compared to injection of PBS or F3 cells without VEGF. Concomitantly, phosphorylation of VEGF receptor flk-1 increased in F3.VEGF group. Stereological counting of BrdU+ cells revealed that transplantation of F3.VEGF significantly enhanced cellular proliferation at 2 weeks after SCI. The number of proliferating NG2+ glial progenitor cells (NG2+/BrdU+) was also increased by F3.VEGF. Furthermore, transplantation of F3.VEGF increased the number of early proliferating cells that differentiated into mature oligodendrocytes, but not astrocytes, at 6 weeks after SCI. F3.VEGF treatment also increased the density of blood vessels in the injured spinal cord and enhanced tissue sparing. These anatomical results were accompanied by improved BBB locomotor scores. The multifaceted effects of VEGF on endogenous gliogenesis, angiogenesis, and tissue sparing could be utilized to improve functional outcomes following SCI.

Spinal cord contusion based on precise vertebral stabilization and tissue displacement measured by combined assessment to discriminate small functional differences

Contusive spinal cord injury (SCI) is the most common type of spinal injury seen clinically. Several rat contusion SCI models have been described, and all have strengths and weaknesses with respect to sensitivity, reproducibility, and clinical relevance. We developed the Louisville Injury System Apparatus (LISA), which contains a novel spine-stabilizing device that enables precise and stable spine fixation, and is based on tissue displacement to determine the severity of injury. Injuries graded from mild to moderately severe were produced using 0.2-, 0.4-, 0.6-, 0.8-, 1.0-, and 1.2-mm spinal cord displacement in rats. Basso, Beattie, and Bresnahan (BBB) and Louisville Swim Score (LSS) could not significantly distinguish between 0.2-mm lesion severities, except those of 0.6- and 0.8-mm BBB scores, but could between 0.4-mm injury differences or if the data were grouped (0.2-0.4, 0.6-0.8, and 1.0-1.2). Transcranial magnetic motor evoked potential (tcMMEP) response amplitudes were decreased 10-fold at 0.2-mm displacement, barely detected at 0.4-mm displacement, and absent with greater displacement injuries. In contrast, somatosensory evoked potentials (SSEPs) were recorded at 0.2- and 0.4-mm displacements with normal amplitudes and latencies but were detected at lower amplitudes at 0.6-mm displacement and absent with more severe injuries. Analyzing combined BBB, tcMMEP, and SSEP results enabled statistically significant discrimination between 0.2-, 0.4-, 0.6-, and 0.8-mm displacement injuries but not the more severe injuries. Present data document that the LISA produces reliable and reproducible SCI whose parameters of injury can be adjusted to more accurately reflect clinical SCI. Moreover, multiple outcome measures are necessary to accurately detect small differences in functional deficits and/or recovery. This is of crucial importance when trying to detect functional improvement after therapeutic intervention to treat SCI.

Macro-architectures in spinal cord scaffold implants influence regeneration

Biomaterial scaffold architecture has not been investigated as a tunable source of influence on spinal cord regeneration. This study compared regeneration in a transected spinal cord within various designed-macro-architecture scaffolds to determine if these architectures alone could enhance regeneration. Three-dimensional (3-D) designs were created and molds were built on a 3-D printer. Salt-leached porous poly(epsilon-caprolactone) was cast in five different macro-architectures: cylinder, tube, channel, open-path with core, and open-path without core. The two open-path designs were created in this experiment to compare different supportive aspects of architecture provided by scaffolds and their influence on regeneration. Rats received T8 transections and implanted scaffolds for 1 and 3 months. Overall morphology and orientation of sections were characterized by H&E, luxol fast blue, and cresyl violet staining. Borders between intact gray matter and non-regenerated defect were observed from GFAP immunolabeling. Nerve fibers and regenerating axons were identified with Tuj-1 immunolabeling. The open-path designs allowed extension of myelinated fibers along the length of the defect both exterior to and inside the scaffolds and maintained their original defect length up to 3 months. In contrast, the cylinder, tube, and channel implants had a doubling of defect length from secondary damage and large scar and cyst formation with no neural tissue bridging. The open-path scaffold architectures enhanced spinal cord regeneration compared to the three other designs without the use of biological factors.

Ephedra sinica inhibits complement activation and improves the motor functions after spinal cord injury in rats

The activation of complement system has been known as an important and significant reaction against the secondary injury after spinal cord injury (SCI). In the present study, we investigated the effect of Ephedra sinica to the inflammation or complement system of injured spinal cord and the influence to the functional recovery after spinal cord injury in rats. We prepared the complement-inhibiting component from E. sinica. Contusive spinal cord injury was induced to Sprague-Dawley rats. We administrated the product from E. sinica to E. sinica group, while distilled water was administered to the control group by gavage after SCI. Complement hemolytic activity (CH50), expression of C3 and C9, myeloperoxidase activity, and motor function were evaluated in E. sinica group and control group. The CH50, complement depositions, and myeloperoxidase activity in the E. sinica group were significantly reduced as compared to the control group. The motor function of E. sinica group was significantly improved from the 7th day as compared with the control group. The results demonstrated that E. sinica might reduce inflammation and improve motor function in rats after spinal cord injury by inhibiting complement activation. The present study has shown that complement system is playing an important role in spinal cord injury, and the possibility of a new therapy strategy, inhibiting or controlling the complement activation and inflammation, for spinal cord injury.

Ipsilateral actions from the feline red nucleus on hindlimb motoneurones

The main aim of the study was to investigate whether neurones in the ipsilateral red nucleus (NR) affect hindlimb motoneurones. Intracellular records from motoneurones revealed that both EPSPs and IPSPs were evoked in them via ipsilaterally located premotor interneurones by stimulation of the ipsilateral NR in deeply anaesthetized cats in which only ipsilaterally descending tract fibres were left intact. When only contralaterally descending tract fibres were left intact, EPSPs mediated by excitatory commissural interneurones were evoked by NR stimuli alone while IPSPs mediated by inhibitory commissural interneurones required joint stimulation of the ipsilateral NR and of the medial longitudinal fascicle (MLF, i.e. reticulospinal tract fibres). Control experiments led to the conclusion that if any inadvertently coactivated axons of neurones from the contralateral NR contributed to these PSPs, their effect was minor. Another aim of the study was to investigate whether ipsilateral actions of NR neurones, pyramidal tract (PT) neurones and reticulospinal tract neurones descending in the MLF on hindlimb motoneurones are evoked via common spinal relay neurones. Mutual facilitation of these synaptic actions as well as of synaptic actions from the contralateral NR and contralateral PT neurones showed that they are to a great extent mediated via the same spinal neurones. A more effective activation of these neurones by not only ipsilateral corticospinal and reticulospinal but also rubrospinal tract neurones may thus contribute to the recovery of motor functions after injuries of the contralateral corticospinal tract neurones. No evidence was found for mediation of early PT actions via NR neurones.

Sustained intraspinal delivery of neurotrophic factor encapsulated in biodegradable nanoparticles following contusive spinal cord injury

Glial cell line derived neurotrophic factor (GDNF) induces neuronal survival and tissue repair after spinal cord injury (SCI). A continuous GDNF supply is believed to gain greater efficacy in the neural restoration of the injured spinal cord. Accordingly, nanovehicle formulation for their efficient delivery and sustained release in injured spinal cord was examined. We first used fluorescence-labeled bovine serum albumin (FBSA) loaded in biodegradable poly(lactic acid-co-glycolic acid) (PLGA) for intraspinal administration after SCI and for in vitro study. Our results showed that the preservation of PLGA-FBSA was observed in the injured spinal cord at 24h, and PLGA-FBSA nanoparticles were well absorbed by neurons and glia, indicating that PLGA as a considerable nanovehicle for the delivery of neuroprotective polypeptide into injured spinal cord. Furthermore, intraspinal injection of GDNF encapsulated in PLGA (PLGA-GDNF) nanoparticles into the injured spinal cord proximal to the lesion center had no effect on gliosis when compared to that observed in SCI rats receiving PLGA injection. However, local administration of PLGA-GDNF effectively preserved neuronal fibers and led to the hindlimb locomotor recovery in rats with SCI, providing a potential strategy for the use of PLGA-GDNF in the treatment of SCI.

Regenerative growth of corticospinal tract axons via the ventral column after spinal cord injury in mice

Studies that have assessed regeneration of corticospinal tract (CST) axons in mice after genetic modifications or other treatments have tacitly assumed that there is little if any regeneration of CST axons in normal mice in the absence of some intervention. Here, we document a previously unrecognized capability for regenerative growth of CST axons in normal mice that involves growth past the lesion via the ventral column. Mice received dorsal hemisection injuries at thoracic level 6-7, which completely transect descending CST axons in the dorsal and dorsolateral column. Corticospinal projections were traced by injecting biotinylated dextran amine (BDA) into the sensorimotor cortex of one hemisphere either at the time of the injury or 4 weeks after injury, and mice were killed at 20-23 or 46 d after injury. At 20-23 d after injury, BDA-labeled CST axons did not extend past the lesion except in one animal. By 46 d after injury, however, a novel population of BDA-labeled CST axons could be seen extending from the gray matter rostral to the injury into the ventral column, past the lesion, and then back into the gray matter caudal to the injury in which they formed elaborate terminal arbors. The number of axons with this highly unusual trajectory was small ( approximately 1% of the total number of labeled CST axons rostral to the injury). The BDA-labeled axons in the ventral column were on the same side as the main tract and thus are not spared ventral CST axons (which would be contralateral to the main tract). These results indicate that normal mice have a capacity for CST regeneration that has not been appreciated previously, which has important implications in studying the effect of genetic or pharmacological manipulations on CST regeneration in mice.

The combination of human neuronal serotonergic cell implants and environmental enrichment after contusive SCI improves motor recovery over each individual strategy

A human neuronal cell line, hNT2.19, which secretes serotonin (5-HT) after differentiation, was used as a transplant source to improve motor dysfunction following severe contusive spinal cord injury (SCI). Also, environmental enrichment (EE) was added to the interspinal transplant treatment paradigm. Motor testing was performed weekly before and following SCI, with and without EE and/or cell transplant conditions. Motor recovery was maximal when both cell transplant and EE were used. Individual treatment paradigms also significantly improved foot rotation and reduced footfall errors but not stride length or base of support dysfunction. This recovery of motor function after SCI suggests that the combinatory use of serotonergic hNT2.19 cell grafts plus EE is a meaningful strategy to modestly improve motor dysfunction that accompanies contusive SCI.

A select combination of neurotrophins enhances neuroprotection and functional recovery following spinal cord injury

Previously, we have shown that topical application of brain-derived neurotrophic factor (BDNF) or insulin-like growth factor 1 (IGF-1) given within 5 to 30 min after a focal trauma to the rat spinal cord attenuates spinal cord injury (SCI)-induced breakdown of the blood-spinal cord barrier (BSCB), edema formation, motor dysfunction, and cell injury. This investigation was undertaken to find out whether a combination of select neurotrophins (BDNF, glial cell line-derived neurotrophic factor [GDNF], neurotrophin 3 [NT-3], or nerve growth factor [NGF]) will further enhance the neuroprotective efficacy of growth factors in SCI. The neurotrophins (0.1-1 microg/10 microL in phosphate-buffered saline) were applied 30, 60, or 90 min after injury topically over the traumatized spinal cord either alone or in combination. The SCI was performed by making a unilateral incision into the right dorsal horn of the T10-T11 segment under Equithesin anesthesia. The rats were allowed to survive 5 h after trauma. Topical application of BDNF, GDNF, or NGF 30 min after SCI in high concentration (0.5 microg and 1 microg) significantly improved the motor functions and reduced the BSCB breakdown, edema formation, and cell injury seen at 5 h. These beneficial effects of neurotropins were absent when administered separately either 60 or 90 min after SCI. However, a combination of BDNF and GDNF (but not with NT-3 or NGF) given either 60 or 90 min after SCI significantly reduced the motor dysfunction and spinal cord pathology at 5 h. These novel observations suggest that a select group of neurotrophins in combination have potential therapeutic value for the treatment of SCI in clinical situations.

Treatments for spinal cord injury: is there hope in neurosteroids?

In this review, we describe the current therapeutic strategies to find a cure for paralysis. We use the example of DHEA, a neurosteroid normally produced in the developing neural tube, to raise the hypothesis that such a class of molecules, capable of modulating proliferation of committed neural precursors, could serve as an environmental cue in the adult injured spinal cord to promote re-population of CNS lesion with endogenous dormant precursor cells. Such mechanism may be a part of the natural response to heal the injured CNS and promote recovery of function, suggesting that neurosteroid-treatment could be a promising and novel therapeutic avenue for SCI. We will review pertinent biological activities of DHEA supporting this hypothesis, demonstrate that such activities, dependent on an intact sonic-hedgehog pathway, are responsible for the motor and bladder functional recovery observed after DHEA-treatment in the adult injured spinal cord. We will also raise the current limitations to further development of DHEA- or other neurosteroid-treatments as drug candidates, including the urgent need to further document DHEA long-term safety in CNS indications.

Spinal cord injury: emerging beneficial role of reactive astrocytes' migration

Spinal cord injury (SCI), despite considerable progress in palliative care, has currently no satisfying therapeutic leading to functional recovery. Inability of central nervous system severed axons to regenerate after injury is considered to originate from both limited intrinsic capabilities of neurons and inhibitory effect of the local environment. Precisely, the so-called "glial scar" formed by reactive astrocytes in response to injury exerts a well-known axon-outgrowth inhibitory effect. However, recent studies revealed that role of reactive astrocytes after SCI is more complex. During the first weeks after injury, reactive astrocytes indeed protect the tissue and contribute to a spontaneous relative functional recovery. Compaction of the lesion center and seclusion of inflammatory cells by migrating reactive astrocytes seem to underlie this beneficial effect. Stimulation of reactive astrocytes migration in the sub-acute phase of SCI might thus represent a new approach to improve the functional outcome of patients.

Social and environmental enrichment improves sensory and motor recovery after severe contusive spinal cord injury in the rat

Neuropathic pain and motor dysfunction are difficult problems following spinal cord injury (SCI). Social and environmental enrichment (SEE), which models much of the clinical rehabilitation environment for post-SCI persons, is the focus of the current investigation which examines the effects of multiple-housing and the addition of climbing spaces, improved bedding and crawl toys on the sensory and motor recovery following a severe contusive SCI. Efficacy was determined with sensory testing, open-field motor behavioral testing, lesion volume analysis and quantification of brain-derived neurotrophic factor (BDNF) in the lumbar spinal cord with and without SEE provided during the recovery period. Sensory and motor testing were performed weekly for 12 weeks following SCI. SEE significantly and permanently reversed cutaneous allodynia, but not thermal hyperalgesia, to near normal levels. The gross locomotor performance (BBB [Basso, Beattie, and Bresnahan] motor scores) significantly improved about two points. In addition, the BBB subscale scores were significantly improved nearly seven points by the end of the study. SEE also significantly improved foot rotation to normal levels and reduced gridwalk footfall errors nearly 50%, but had no effect on stride length or base of support dysfunctions. SEE significantly increased the total volume of a thoracic segment of cord encompassing the injury site at 12 weeks, by reducing cavitation and increasing both the volume of grey and white matter spared, compared to SCI alone. When BDNF levels were examined in the injured lumbar spinal cord, SEE significantly returned BDNF levels to near-normal. These data suggest that immediate use of SEE after contusive SCI is able to improve overall spinal cell survival and prevent much of the sensory and motor dysfunction that accompanies contusive SCI.