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Blast exposure can injure brain by multiple mechanisms, and injury attributable to direct effects of the blast wave itself have been difficult to distinguish from that caused by rapid head displacement and other secondary processes. To resolve this issue, we used a rat model of blast exposure in which head movement was either strictly prevented or permitted in the lateral plane. Blast was found to produce axonal injury even with strict prevention of head movement. This axonal injury was restricted to the cerebellum, with the exception of injury in visual tracts secondary to ocular trauma. The cerebellar axonal injury was increased in rats in which blast-induced head movement was permitted, but the pattern of injury was unchanged. These findings support the contentions that blast per se, independent of head movement, is sufficient to induce axonal injury, and that axons in cerebellar white matter are particularly vulnerable to direct blast - induced injury.

High rates of acute and chronic pain are associated with traumatic brain injury (TBI), but mechanisms responsible for the association remain elusive. Recent data suggest dysregulated descending pain modulation circuitry could be involved. Based on these and other observations, we hypothesized that serotonin (5-HT)-dependent activation of spinal CXC Motif Chemokine Receptor 2 (CXCR2) may support TBI-related nociceptive sensitization in a mouse model of mild TBI (mTBI). We observed that systemic 5-HT depletion with p-chlorophenylalanine attenuated mechanical hypersensitivity seen after mTBI. Likewise, selective spinal 5-HT fiber depletion with 5,7-dihydroxytryptamine (5,7-DHT) reduced hypersensitivity after mTBI. Consistent with a role for spinal 5-HT3 serotonin receptors, intrathecal ondansetron administration after TBI dose-dependently attenuated nociceptive sensitization. Also, selective CXCR2 antagonist SCH527123 treatment attenuated mechanical hypersensitivity after mTBI. Furthermore, spinal CXCL1 and CXCL2 mRNA and protein levels were increased after mTBI as were GFAP and IBA-1 markers. Spinal 5,7-DHT application reduced both chemokine expression and glial activation. Our results suggest dual pathways for nociceptive sensitization after mTBI, direct 5-HT effect through 5-HT3 receptors and indirectly through upregulation of chemokine signaling. Designing novel clinical interventions against either the 5-HT3 mediated component or chemokine pathway may be beneficial in treating pain frequently seen in patients after mTBI.

SUMMARYTraumatic spinal cord injury (SCI) produces a complex syndrome that is expressed across multiple endpoints ranging from molecular and cellular changes to functional behavioral deficits. Effective therapeutic strategies for CNS injury are therefore likely to manifest multi-factorial effects across a broad range of biological and functional outcome measures. Thus, multivariate analytic approaches are needed to capture the linkage between biological and neurobehavioral outcomes. Injury-induced neuroinflammation (NI) presents a particularly challenging therapeutic target, since NI is involved in both degeneration and repair1,2. Here, we used big-data integration and large-scale analytics to examine a large dataset of preclinical efficacy tests combining 5 different blinded, fully counter-balanced treatment trials for different acute anti-inflammatory treatments for cervical spinal cord injury in rats. Multi-dimensional discovery, using topological data analysis3 (TDA) and principal components analysis (PCA) revealed that only one showed consistent multidimensional syndromic benefit: intrathecal application of recombinant soluble TNFα receptor 1 (sTNFR1), which showed an inverse-U dose response efficacy. Using the optimal acute dose, we showed that clinically-relevant 90 min delayed treatment profoundly affected multiple biological indices of NI in the first 48 hrs after injury, including reduction in pro-inflammatory cytokines and gene expression of a coherent complex of acute inflammatory mediators and receptors. Further, a 90 min delayed bolus dose of sTNFR1 reduced the expression of NI markers in the chronic perilesional spinal cord, and consistently improved neurological function over 6 weeks post SCI. These results provide validation of a novel strategy for precision preclinical drug discovery that is likely to improve translation in the difficult landscape of CNS trauma, and confirm the importance of TNFα signaling as a therapeutic target.

The inflammation response induced by brain trauma can impair recovery. This response requires several hours to develop fully and thus provides a clinically relevant therapeutic window of opportunity. Poly(ADP-ribose) polymerase inhibitors suppress inflammatory responses, including brain microglial activation. We evaluated delayed treatment with veliparib, a poly(ADP-ribose) polymerase inhibitor, currently in clinical trials as a cancer therapeutic, in rats and pigs subjected to controlled cortical impact (CCI). In rats, CCI induced a robust inflammatory response at the lesion margins, scattered cell death in the dentate gyrus, and a delayed, progressive loss of corpus callosum axons. Pre-determined measures of cognitive and motor function showed evidence of attentional deficits that resolved after three weeks and motor deficits that recovered only partially over eight weeks. Veliparib was administered beginning 2 or 24 h after CCI and continued for up to 12 days. Veliparib suppressed CCI-induced microglial activation at doses of 3 mg/kg or higher and reduced reactive astrocytosis and cell death in the dentate gyrus, but had no significant effect on delayed axonal loss or functional recovery. In pigs, CCI similarly induced a perilesional microglial activation that was attenuated by veliparib. CCI in the pig did not, however, induce detectable persisting cognitive or motor impairment. Our results showed veliparib suppression of CCI-induced microglial activation with a delay-to-treatment interval of at least 24 h in both rats and pigs, but with no associated functional improvement. The lack of improvement in long-term recovery underscores the complexities in translating anti-inflammatory effects to clinically relevant outcomes.

Chronic pain after traumatic brain injury (TBI) is very common, but the mechanisms linking TBI to pain and the pain-related interactions of TBI with peripheral injuries are poorly understood. In these studies we pursued the hypothesis that TBI pain sensitization is associated with histone acetylation in the rat lateral fluid percussion model. Some animals received hindpaw incisions in addition to TBI to mimic polytrauma. Neuropathological analysis of brain tissue from sham and TBI animals revealed evidence of bleeding, breakdown of the blood brain barrier, in the cortex, hippocampus, thalamus and other structures related to pain signal processing. Mechanical allodynia was measured in these animals for up to eight weeks post-injury. Inhibitors of histone acetyltransferase (HAT) and histone deacetylase (HDAC) were used to probe the role of histone acetylation in such pain processing. We followed serum markers including glial fibrillary acidic protein (GFAP), neuron-specific enolase 2 (NSE) myelin basic protein (MBP) and S100β to gauge TBI injury severity. Our results showed that TBI caused mechanical allodynia in the hindpaws of the rats lasting several weeks. Hindpaws contralateral to TBI showed more rapid and profound sensitization than ipsilateral hindpaws. The inhibition of HAT using curcumin 50 mg/kg s.c reduced mechanical sensitization while the HDAC inhibitor suberoylanilide hydroxamic acid 50 mg/kg i.p. prolonged sensitization in the TBI rats. Immunohistochemical analyses of spinal cord tissue localized changes in the level of acetylation of the H3K9 histone mark to dorsal horn neurons. Taken together, these findings demonstrate that TBI induces sustained nociceptive sensitization, and changes in spinal neuronal histone proteins may play an important role., Highlights • Pain after traumatic brain injury (TBI) is common and often persistent. • Using the rat lateral fluid percussion model, it was observed that hindpaw allodynia is present for three weeks after TBI. • Damage to pain processing areas of the brain can be demonstrated after TBI. • Agents regulating the epigenetic acetylation of histone proteins modified the time course of TBI-induced allodynia.

A major advancement in the field of analgesic pharmacology has been the development of G-protein-biased opioid agonists that display less respiratory depression than conventional drugs. It is uncertain, however, whether these new drugs cause less tolerance, hyperalgesia, and other maladaptations when administered repeatedly.The archetypical µ-opioid receptor agonist morphine and, separately, the G-protein-biased µ-opioid receptor agonist oliceridine were administered to mice. These drugs were used in models of acute analgesia, analgesic tolerance, opioid-induced hyperalgesia, reward, and physical dependence. In addition, morphine and oliceridine were administered for 7 days after tibia fracture and pinning; mechanical allodynia and gait were followed for 3 weeks. Finally, the expression of toll-like receptor-4 and nacht domain-, leucine-rich repeat-, and pyrin domain-containing protein 3 (NALP3) and interleukin-1β mRNA were quantified in spinal tissue to measure surgical and drug effects on glia-related gene expression.We observed using the tail flick assay that oliceridine was a 4-fold more potent analgesic than morphine, but that oliceridine treatment caused less tolerance and opioid-induced hyperalgesia than morphine after 4 days of ascending-dose administration. Using similar analgesic doses, morphine caused reward behavior in the conditioned place preference assay while oliceridine did not. Physical dependence was, however, similar for the 2 drugs. Likewise, morphine appeared to more significantly impair the recovery of nociceptive sensitization and gait after tibial fracture and pinning than oliceridine. Furthermore, spinal cord toll-like receptor-4 levels 3 weeks after fracture were higher in fracture mice given morphine than those given oliceridine.Aside from reduced respiratory depression, G-protein-biased agonists such as oliceridine may reduce opioid maladaptations and enhance the quality of surgical recovery.

Chronic pain is a common consequence of traumatic brain injury (TBI) that can increase the suffering of a patient and pose a significant challenge to rehabilitative efforts. Unfortunately, the mechanisms linking TBI to pain are poorly understood, and specific treatments for TBI-related pain are still lacking. Our laboratory has shown that TBI causes pain sensitization in areas distant to the site of primary injury, and that changes in spinal gene expression may underlie this sensitization. The aim of this study was to examine the roles that pain modulatory pathways descending from the brainstem play in pain after TBI. Deficiencies in one type of descending inhibition, diffuse noxious inhibitory control (DNIC), have been suggested to be responsible for the development of chronic pain by allowing excess and uncontrolled afferent nociceptive inputs. Here we expand our knowledge of pain after TBI in two ways: (1) by outlining the neuropathology in pain-related centers of the brain and spinal cord involved in DNIC using the rat lateral fluid percussion (LFP) model of TBI, and (2) by evaluating the effects of a potent histone acetyl transferase inhibitor, anacardic acid (AA), on LFP-induced pain behaviors and neuropathology when administered for several days after TBI. The results revealed that TBI induces transient mechanical allodynia and a chronic persistent loss of DNIC. Further, while short-term AA treatment can block acute nociceptive sensitization and some early neuropathological changes, this treatment neither prevented the loss of DNIC nor did it alter long-term neuropathological changes in the brain or spinal cord.

Background Traumatic brain injury refers to a broad range of neurological, cognitive, and emotional factors that result from the application of an external force to the head. Individuals recovering from traumatic brain injury will frequently experience acute and chronic pain. Objective The objective of this paper is to discuss the pathophysiological changes resulting from traumatic brain injury and how these may be involved in the development and persistence of pain after injury. Methods We based our review on articles retrieved from the MEDLINE database of references and abstracts on life sciences and biomedical topics (1966 to present) using the search engine PubMed (United States National Library of Medicine). The published literature focused on traumatic brain injury and pain. Conclusions This review presents evidence that pain is common after traumatic brain injury. However, while there are many potential mechanisms explaining this problem such as neuroinflammation, excitotoxicity, and axonal degeneration, we have no clear understanding of which of them contribute in individual patients. The authors highlight the priorities for research that will expand our knowledge and that may lead to the rational design of therapies that both reduce pain and provide optimal overall outcomes after traumatic brain injury.

Acute and persistent pain are recognized consequences of TBI that can enhance suffering and significantly impair rehabilitative efforts. Both experimental models and clinical studies suggest that TBI may result in an imbalance between descending pain facilitatory and inhibitory pathways. The aim of this study was to assess the role of enhanced descending serotonin-mediated pain facilitation in a rat TBI model using selective spinal serotonergic fiber depletion with 5, 7-dihydroxytryptamine (DHT). We observed significant hindpaw allodynia in TBI rats that was reduced after DHT but not vehicle treatment. Immunohistochemical studies demonstrated profound spinal serotonin depletion in DHT-treated rats. Furthermore, lumbar intrathecal administration of the 5-HT3 receptor antagonist ondansetron at 7 days post-injury (DPI), when hindpaw allodynia was maximal, also attenuated nociceptive sensitization. Additional immunohistochemical analyses of the lumbar spinal cord at 7 DPI revealed a robust bilateral microglial response in the superficial dorsal horns that was significantly reduced with DHT treatment. Furthermore, serotonin depletion also prevented the TBI-induced bilateral increase in c-Fos positive cells within the Rexed laminae I and II of the dorsal horns. These results indicate that in the weeks following TBI, pain may be responsive to 5-HT3 receptor antagonists or other measures which rebalance descending pain modulation.

We describe here a novel forelimb locomotor assessment scale (FLAS) that assesses forelimb use during locomotion in rats injured at the cervical level. A quantitative scale was developed that measures movements of shoulder, elbow, and wrist joints, forepaw position and digit placement, forelimb-hindlimb coordination, compensatory behaviors adopted while walking, and balance. Female Sprague-Dawley rats received graded cervical contusions ranging from 200 to 230 ("mild," n=11) and 250-290 kdyn ("moderate," n=13) between C5 and C8. Rats were videotaped post-injury as they walked along an alley to determine deficits and recovery of forelimb function. Recovery of shoulder and elbow joint movement occurred rapidly (within 1-7 days post-injury), whereas recovery of wrist joint movement was slower and more variable. Most rats in all groups displayed persistent deficits in forepaw and digit movement, but developed compensatory behaviors to allow functional forward locomotion within 1-2 weeks post-injury. Recovery of forelimb function as measured by the FLAS reached a plateau by 3 weeks post-injury in all groups. Rats with mild contusions displayed greater locomotor recovery than rats with moderate contusions, but exhibited persistent deficits compared to sham controls. Reliability was tested by having seven raters (three internal, four external) from different laboratories, independently and blindly score videos of all rats. The multivariate correlation between all raters, all animals, and all time points ranged from r(2)=0.88-0.96 (p

The progressive loss of CNS myelin in patients with multiple sclerosis (MS) has been proposed to result from the combined effects of damage to oligodendrocytes and failure of remyelination. A common feature of demyelinated lesions is the presence of oligodendrocyte precursors (OLPs) blocked at a premyelinating stage. However, the mechanistic basis for inhibition of myelin repair is incompletely understood. To identify novel regulators of OLP differentiation, potentially dysregulated during repair, we performed a genome-wide screen of 1040 transcription factor-encoding genes expressed in remyelinating rodent lesions. We report that ∼50 transcription factor-encoding genes show dynamic expression during repair and that expression of the Wnt pathway mediator Tcf4 (aka Tcf7l2) within OLPs is specific to lesioned—but not normal—adult white matter. We report that β-catenin signaling is active during oligodendrocyte development and remyelination in vivo. Moreover, we observed similar regulation of Tcf4 in the developing human CNS and lesions of MS. Data mining revealed elevated levels of Wnt pathway mRNA transcripts and proteins within MS lesions, indicating activation of the pathway in this pathological context. We show that dysregulation of Wnt–β-catenin signaling in OLPs results in profound delay of both developmental myelination and remyelination, based on (1) conditional activation of β-catenin in the oligodendrocyte lineage in vivo and (2) findings from APCMin mice, which lack one functional copy of the endogenous Wnt pathway inhibitor APC. Together, our findings indicate that dysregulated Wnt–β-catenin signaling inhibits myelination/remyelination in the mammalian CNS. Evidence of Wnt pathway activity in human MS lesions suggests that its dysregulation might contribute to inefficient myelin repair in human neurological disorders.

Multiple sclerosis (MS) represents a considerable challenge to experimentally model due to its twin pathologies of inflammatory demyelination and neurodegeneration along with its multifocal and multiphasic nature. Experimental autoimmune encephalomyelitis (EAE) in Biozzi ABH mice has previously been shown to reproduce many clinical features also found in secondary progressive MS. In this study we sought to characterise the pathology of chronic EAE in ABH mice. In addition to marked gliosis, we report substantial demyelination, remyelination and axonal and neuronal loss. Together with the clinical pattern, our findings identify chronic EAE as an excellent model of secondary progressive multiple sclerosis.

The relative merits of endogenous and exogenous oligodendrocyte progenitor cells (OPCs) for remyelination are compared in terms of their ability to repopulate OPC-depleted tissue and generate remyelinating oligodendrocytes. Exogenous neonatal OPCs can repopulate OPC-depleted tissue 5-10 times faster than endogenous cells and as a result are capable of more extensive remyelination. Both endogenous and exogenous cells will only repopulate normal tissue if there is extensive depletion of the local OPC population and both show reduced ability to generate remyelinating cells in the absence of acute inflammation. When endogenous OPCs are depleted by X-irradiation during cuprizone intoxication, where there is a combination of astrocytosis and acute demyelination, endogenous but not exogenous embryo-derived OPCs fail to repopulate the OPC-depleted cortex.

Human embryonic stem cells (hESCs) are a potential source of defined tissue for cell-based therapies in regenerative neurology. In order for this potential to be realized, there is a need for the evaluation of the behaviour of human embryonic stem cell-derived neural stem cells (hES-NSCs) both in the normal and the injured CNS. Using normal tissue and two experimental models, we examined the response of clinically compatible hES-NSCs to physiological and pathological signals. We demonstrate that the phenotypic potential of a multipotent population of hES-NSCs is influenced by these cues both in vitro and in vivo. hES-NSCs display a temporal profile of neurogenic and gliogenic differentiation, with the generation of mature neurons and glia over 4 weeks in vitro, and 20 weeks in the uninjured rodent brain. However, transplantation into the pathological CNS accelerates maturation and polarizes hES-NSC differentiation potential. This study highlights the role of environmental signals in determining both lineage commitment and temporal maturation of human neural stem cells. Controlled manipulation of environmental signals appropriate to the pathological specificity of the targeted disease will be necessary in the design of therapeutic stem cell-based strategies.

Data-driven discovery in complex neurological disorders has potential to extract meaningful syndromic knowledge from large, heterogeneous data sets to enhance potential for precision medicine. Here we describe the application of topological data analysis (TDA) for data-driven discovery in preclinical traumatic brain injury (TBI) and spinal cord injury (SCI) data sets mined from the Visualized Syndromic Information and Outcomes for Neurotrauma-SCI (VISION-SCI) repository. Through direct visualization of inter-related histopathological, functional and health outcomes, TDA detected novel patterns across the syndromic network, uncovering interactions between SCI and co-occurring TBI, as well as detrimental drug effects in unpublished multicentre preclinical drug trial data in SCI. TDA also revealed that perioperative hypertension predicted long-term recovery better than any tested drug after thoracic SCI in rats. TDA-based data-driven discovery has great potential application for decision-support for basic research and clinical problems such as outcome assessment, neurocritical care, treatment planning and rapid, precision-diagnosis., Data-driven discovery in complex neurological disorders has potential to extract meaningful knowledge from large, heterogeneous datasets. Here the authors apply topological data analysis to assess therapeutic effects in preclinical traumatic brain injury and spinal cord injury research studies.

Clinical spinal cord injury (SCI) is accompanied by comorbid peripheral injury in 47% of patients. Human and animal modeling data have shown that painful peripheral injuries undermine long-term recovery of locomotion through unknown mechanisms. Peripheral nociceptive stimuli induce maladaptive synaptic plasticity in dorsal horn sensory systems through AMPA receptor (AMPAR) phosphorylation and trafficking to synapses. Here we test whether ventral horn motor neurons in rats demonstrate similar experience-dependent maladaptive plasticity below a complete SCIin vivo. Quantitative biochemistry demonstrated that intermittent nociceptive stimulation (INS) rapidly and selectively increases AMPAR subunit GluA1 serine 831 phosphorylation and localization to synapses in the injured spinal cord, while reducing synaptic GluA2. These changes predict motor dysfunction in the absence of cell death signaling, suggesting an opportunity for therapeutic reversal. Automated confocal time-course analysis of lumbar ventral horn motor neurons confirmed a time-dependent increase in synaptic GluA1 with concurrent decrease in synaptic GluA2. Optical fractionation of neuronal plasma membranes revealed GluA2 removal from extrasynaptic sites on motor neurons early after INS followed by removal from synapses 2 h later. As GluA2-lacking AMPARs are canonical calcium-permeable AMPARs (CP-AMPARs), their stimulus- and time-dependent insertion provides a therapeutic target for limiting calcium-dependent dynamic maladaptive plasticity after SCI. Confirming this, a selective CP-AMPAR antagonist protected against INS-induced maladaptive spinal plasticity, restoring adaptive motor responses on a sensorimotor spinal training task. These findings highlight the critical involvement of AMPARs in experience-dependent spinal cord plasticity after injury and provide a pharmacologically targetable synaptic mechanism by which early postinjury experience shapes motor plasticity.

Axon loss is recognised as a significant contributor to the progression of the disability associated with multiple sclerosis. Although evidence of axon damage is found in areas of chronic demyelination it is more frequently seen in association with acute demyelination. This study compares the incidence of axon degeneration associated with the areas undergoing demyelination in young adult (8-10 weeks) and aged (6-7 months) C57BL/6 mice in cuprizone intoxication; a widely used model of demyelination. The incidence of axon transection, as indicated by the presence of SMI 32 positive axonal spheroids, and evidence of axon loss in the medial corpus callosum, were significantly greater in aged mice, as was the magnitude of the macrophage and astrocyte response to demyelination. Aged C57BL/6 mice are thus more prone to axon degeneration in association with demyelination than young adult mice. A retrospective study indicated that the incidence of axon degeneration was much higher in C57BL/6 mice than in the Swiss albino mice used in the early cuprizone intoxication studies which were fed much higher doses of cuprizone. These results indicate both a genetic and age susceptibility to demyelination-associated axon transection.

Efforts to understand spinal cord injury (SCI) and other complex neurotrauma disorders at the pre-clinical level have shown progress in recent years. However, successful translation of basic research into clinical practice has been slow, partly because of the large, heterogeneous data sets involved. In this sense, translational neurological research represents a "big data" problem. In an effort to expedite translation of pre-clinical knowledge into standards of patient care for SCI, we describe the development of a novel database for translational neurotrauma research known as Visualized Syndromic Information and Outcomes for Neurotrauma-SCI (VISION-SCI). We present demographics, descriptive statistics, and translational syndromic outcomes derived from our ongoing efforts to build a multi-center, multi-species pre-clinical database for SCI models. We leveraged archived surgical records, postoperative care logs, behavioral outcome measures, and histopathology from approximately 3000 mice, rats, and monkeys from pre-clinical SCI studies published between 1993 and 2013. The majority of animals in the database have measures collected for health monitoring, such as weight loss/gain, heart rate, blood pressure, postoperative monitoring of bladder function and drug/fluid administration, behavioral outcome measures of locomotion, and tissue sparing postmortem. Attempts to align these variables with currently accepted common data elements highlighted the need for more translational outcomes to be identified as clinical endpoints for therapeutic testing. Last, we use syndromic analysis to identify conserved biological mechanisms of recovery after cervical SCI between rats and monkeys that will allow for more-efficient testing of therapeutics that will need to be translated toward future clinical trials.

The primate corticospinal tract (CST), the major descending pathway mediating voluntary hand movements, comprises nine or more functional subdivisions. The role of subcomponents other than that from primary motor cortex, however, is not well understood. We have previously shown that following a cervical dorsal rhizotomy (Darian-Smith et al., 2013), CST projections originating from primary somatosensory (S1) and motor (M1) cortex responded quite differently to injury. Terminal projections from the S1 (areas 3b/1/2) shrank to 110%). Here, we asked what happens when a central lesion is added to the equation, to better simulate clinical injury. Monkeys (n= 6) received either a unilateral (1) dorsal root lesion (DRL), (2) or a combined DRL/dorsal column lesion (DRL/DCL), or (3) a DRL/DCL where the DCL was made 4 months following the initial DRL. Electrophysiological recordings were made in S1 4 months postlesion in the first two groups, and 6 weeks after the DCL in the third lesion group, to identify the reorganized region of D1–D3 (thumb, index finger, and middle finger) representation. Anterograde tracers were then injected bilaterally to assess spinal terminal labeling. Remarkably, in all DRL/DCL animals, terminal projections from the S1 and M1 extended bilaterally and caudally well beyond terminal territories in normal animals or following a DRL. These data were highly significant. Extensive sprouting from the S1 CST has not been reported previously, and these data raise important questions about S1 CST involvement in recovery following spinal injury.

Spinal cord injury (SCI) and other neurological disorders involve complex biological and functional changes. Well-characterized preclinical models provide a powerful tool for understanding mechanisms of disease; however managing information produced by experimental models represents a significant challenge for translating findings across research projects and presents a substantial hurdle for translation of novel therapies to humans. In the present work we demonstrate a novel ‘syndromic’ information-processing approach for capitalizing on heterogeneous data from diverse preclinical models of SCI to discover translational outcomes for therapeutic testing. We first built a large, detailed repository of preclinical outcome data from 10 years of basic research on cervical SCI in rats, and then applied multivariate pattern detection techniques to extract features that are conserved across different injury models. We then applied this translational knowledge to derive a data-driven multivariate metric that provides a common ‘ruler’ for comparisons of outcomes across different types of injury (NYU/MASCIS weight drop injuries, Infinite Horizons (IH) injuries, and hemisection injuries). The findings revealed that each individual endpoint provides a different view of the SCI syndrome, and that considering any single outcome measure in isolation provides a misleading, incomplete view of the SCI syndrome. This limitation was overcome by taking a novel multivariate integrative approach for leveraging complex data from preclinical models of neurological disease to identify therapies that target multiple outcomes. We suggest that applying this syndromic approach provides a roadmap for translating therapies for SCI and other complex neurological diseases.

Several experimental models of cervical spinal cord injury (SCI) have been developed recently to assess the consequences of damage to this level of the spinal cord (Pearse et al., 2005, Gensel et al., 2006, Anderson et al., 2009), as the majority of human SCI occur here (Young, 2010; www.sci-info-pages.com). Behavioral deficits include loss of forelimb function due to damage to the white matter affecting both descending motor and ascending sensory systems, and to the gray matter containing the segmental circuitry for processing sensory input and motor output for the forelimb. Additionally, a key priority for human patients with cervical SCI is restoration of hand/arm function (Anderson, 2004). Thus, outcome measures that assess both proximal and distal forelimb function are needed. Although there are several behavioral assays that are sensitive to different aspects of forelimb recovery in experimental models of cervical SCI (Girgis et al., 2007, Gensel et al., 2006, Ballerman et al., 2001, Metz and Whishaw, 2000, Bertelli and Mira, 1993, Montoya et al., 1991, Whishaw and Pellis, 1990), few techniques provide detailed information on the recovery of fine motor control and digit movement. The current measurement technique, the Irvine, Beatties and Bresnahan forelimb scale (IBB), can detect recovery of both proximal and distal forelimb function including digit movements during a naturally occurring behavior that does not require extensive training or deprivation to enhance motivation. The IBB was generated by observing recovery after a unilateral C6 SCI, and involves video recording of animals eating two differently shaped cereals (spherical and doughnut) of a consistent size. These videos were then used to assess features of forelimb use, such as joint position, object support, digit movement and grasping technique. The IBB, like other forelimb behavioral tasks, shows a consistent pattern of recovery that is sensitive to injury severity. Furthermore, the IBB scale could be used to assess recovery following other types of injury that impact normal forelimb function.

PURPOSE: Glaucoma is a common neurodegenerative disease for which current therapies are often insufficient; thus, new neuroprotective strategies are an important goal. Stem cells are attracting increasing attention as mediators of neuroprotection, often conferred via the trophic support of injured neurons. The purpose of our investigation was to determine whether oligodendrocyte precursor cells (OPCs), a type of neural stem cell, can protect retinal ganglion cells (RGCs) from glaucomatous damage in vivo. METHODS: Intraocular pressure was chronically increased by trabecular laser treatment delivered unilaterally to adult rat eyes. OPCs were isolated in vitro and then transplanted intravitreally either before, or concurrent with, injury induction. Survival, migration, differentiation, and integration of grafted cells were assessed by immunohistochemistry. RGC survival was assessed by optic nerve axon quantification. RESULTS: Transplanted OPCs were found to survive within the eye for at least 12 weeks and to localize close to the RGCs. Moreover, OPCs significantly enhanced the survival of RGCs in the glaucomatous eye, but only when concomitantly activated by inflammation. Axonal loss relative to the untreated fellow eye was 28.34% +/- 11.51% in eyes that received activated OPCs, compared with 60.34% +/- 8.28% in control eyes (mean +/- SEM; P = 0.05). Amelioration of RGC death was not attributable to inflammation but relied on an interaction between inflammatory cells and OPCs. Engrafted cells also displayed multipotentiality in vivo. CONCLUSIONS: The impressive neuroprotection conferred by OPCs in this model suggests stem cell-based therapies should be explored further as a potential treatment for glaucoma.

The adult bone marrow contains a population of multipotent mesenchymal stromal cells (MSCs), defined by plastic adherence, expression of stromal cell surface markers, and differentiation into mesenchymal lineages. There has been much interest in the possible therapeutic use of MSCs in the treatment of demyelinating diseases of the central nervous system. One therapeutic possibility is that these cells may be able to remyelinate when directly injected into the demyelinated spinal cord. Here we examine the effects of direct transplantation of green fluorescent protein (GFP)-labeled MSCs into a model of focal spinal cord demyelination induced by ethidium bromide. We demonstrate that direct intralesional injection of undifferentiated MSCs does not lead to remyelination. Furthermore, we report that transplanted MSCs migrate into areas of normal tissue, deposit collagen, and are associated with axonal damage. These findings support the need for further experimental evaluation of the safety and efficacy of direct parenchymal injection of MSCs into demyelinated lesions and highlight an important issue regarding potential clinical consequences of culture heterogeneity of MSCs between centers.

In multiple sclerosis, demyelination of the CNS axons is associated with axonal injury and degeneration, which is now accepted as the major cause of neurological disability in the disease. Although the kinetics and the extent of axonal damage have been described in detail, the mechanisms by which it occurs are as yet unclear; one suggestion is failure of remyelination. The goal of this study was to test the hypothesis that failure of prompt remyelination contributes to axonal degeneration following demyelination. Remyelination was inhibited by exposing the brain to 40 Gy of X-irradiation prior to cuprizone intoxication and this resulted in a significant increase in the extent of axonal degeneration and loss compared to non-irradiated cuprizone-fed mice. To exclude the possibility that this increase was a consequence of the X-irradiation and to highlight the significance of remyelination, we restored remyelinating capacity to the X-irradiated mouse brain by transplanting of GFP-expressing embryo-derived neural progenitors. Restoring the remyelinating capacity in these mice resulted in a significant increase in axon survival compared to non-transplanted, X-irradiated cuprizone-intoxicated mice. Our results support the concept that prompt remyelination protects axons from demyelination-associated axonal loss and that remyelination failure contributes to the axon loss that occurs in multiple sclerosis.

This study was designed to investigate whether the residual, dysfunctional oligodendrocyte progenitor cells (OPCs) observed following X-irradiation of the mouse spinal cord [D. M. Chari et al. (2003) Exp. Neurol., 198, 145-153], the presence of which prevented the endogenous repopulation of these areas from normal tissue, reflects a general response of OPCs in the mouse central nervous system (CNS) to X-irradiation. The brains of adult mice were exposed to 40 Gy of X-irradiation and the effect of X-irradiation on the OPCs was assessed up to 4 weeks post-irradiation using anti-NG2 antibodies. X-irradiation resulted in almost complete depletion of OPCs within the telencephalon (cortex, corpus callosum and hippocampus) by 7 days post-irradiation, which was followed by progressive repopulation of OPCs from non-irradiated areas of the cortex. By contrast, within the lower brain centres (the diencephalon and mesencephalon) OPC loss occurred much more slowly so that 26% of the OPCs still remained 4 weeks after X-irradiation. The consequence of this heterogeneous response to X-irradiation was that whereas transplanted and endogenous OPCs rapidly established themselves in the OPC-depleted telencephalon this did not occur in the areas where there was incomplete depletion of endogenous OPCs. Our findings confirm not only the requirement for almost complete OPC depletion in order to establish transplanted OPCs in normal tissue but also highlight a heterogeneity of progenitor populations in different areas of the mouse CNS.