Perturbations in risk/reward decision making and frontal cortical catecholamine regulation induced by mild traumatic brain injury.

Mild traumatic brain injury (mTBI) disrupts cognitive processes that influence risk taking behavior. Little is known regarding the effects of repetitive mild injury (rmTBI) or whether these outcomes are sex specific. Risk/reward decision making is mediated by the prefrontal cortex (PFC), which is densely innervated by catecholaminergic fibers. Aberrant PFC catecholamine activity has been documented following TBI and may underlie TBI-induced risky behavior. The present study characterized the effects of rmTBI on risk/reward decision making behavior and catecholamine transmitter regulatory proteins within the PFC. Rats were exposed to sham, single (smTBI), or three closed-head controlled cortical impact (CH-CCI) injuries and assessed for injury-induced effects on risk/reward decision making using a probabilistic discounting task (PDT). In the first week post-final surgery, mTBI increased risky choice preference. By the fourth week, males exhibited increased latencies to make risky choices following rmTBI, demonstrating a delayed effect on processing speed. When levels of tyrosine hydroxylase (TH) and the norepinephrine reuptake transporter (NET) were measured within subregions of the PFC, females exhibited dramatic increases of TH levels within the orbitofrontal cortex (OFC) following smTBI. However, both males and females demonstrated reduced levels of OFC NET following rmTBI. These results indicate the OFC is susceptible to catecholamine instability after rmTBI and suggests that not all areas of the PFC contribute equally to TBI-induced imbalances. Overall, the CH-CCI model of rmTBI has revealed time-dependent and sex-specific changes in risk/reward decision making and catecholamine regulation following repetitive mild head injuries.

Sex and estrous-phase dependent alterations in depression-like behavior following mild traumatic brain injury in adolescent rats.

Following mild traumatic brain injury (TBI), high school and collegiate-aged females tend to report more emotional symptoms than males. Adolescent male and female rats (35 days old) were subjected to mild TBI and evaluated for anxiety- and depression-like behaviors using the elevated plus maze and forced swim test (FST), respectively, and cellular alterations. Injured brains did not exhibit an overt lesion, atrophy of tissue or astrocytic reactivity underneath the impact site at 6-week post-injury, suggestive of the mild nature of trauma. Neither male nor female brain-injured rats exhibited anxiety-like behavior at 2 or 6 weeks, regardless of estrous phase at the time of behavior testing. Brain-injured male rats did not exhibit any alterations in immobility, swimming and climbing times in the FST compared to sham-injured rats at either 2- or 6-week post-injury. Brain-injured female rats did, however, exhibit an increase in immobility (in the absence of changes in swimming and climbing times) in the FST at 6 weeks post-injury only during the estrus phase of the estrous cycle, suggestive of a depression-like phenotype. Combined administration of the estrogen receptor antagonist, tamoxifen, and the progesterone receptor antagonist, mifepristone, during proestrus was able to prevent the depression-like phenotype observed during estrus. Taken together, these data suggest that female rats may be more vulnerable to exhibiting behavioral deficits following mild TBI and that estrous phase may play a role in depression-like behavior.

Stem Cell Therapy for Pediatric Traumatic Brain Injury.

There has been a growing interest in the potential of stem cell transplantation as therapy for pediatric brain injuries. Studies in pre-clinical models of pediatric brain injury such as Traumatic Brain Injury (TBI) and neonatal hypoxia-ischemia (HI) have contributed to our understanding of the roles of endogenous stem cells in repair processes and functional recovery following brain injury, and the effects of exogenous stem cell transplantation on recovery from brain injury. Although only a handful of studies have evaluated these effects in models of pediatric TBI, many studies have evaluated stem cell transplantation therapy in models of neonatal HI which has a considerable overlap of injury pathology with pediatric TBI. In this review, we have summarized data on the effects of stem cell treatments on histopathological and functional outcomes in models of pediatric brain injury. Importantly, we have outlined evidence supporting the potential for stem cell transplantation to mitigate pathology of pediatric TBI including neuroinflammation and white matter injury, and challenges that will need to be addressed to incorporate these therapies to improve functional outcomes following pediatric TBI.

Progesterone treatment following traumatic brain injury in the 11-day-old rat attenuates cognitive deficits and neuronal hyperexcitability in adolescence.

Traumatic brain injury (TBI) in children younger than 4 years old results in cognitive and psychosocial deficits in adolescence and adulthood. At 4 weeks following closed head injury on postnatal day 11, male and female rats exhibited impairment in novel object recognition memory (NOR) along with an increase in open arm time in the elevated plus maze (EPM), suggestive of risk-taking behaviors. This was accompanied by an increase in intrinsic excitability and frequency of spontaneous excitatory post-synaptic currents (EPSCs), and a decrease in the frequency of spontaneous inhibitory post-synaptic currents in layer 2/3 neurons within the medial prefrontal cortex (PFC), a region that is implicated in both object recognition and risk-taking behaviors. Treatment with progesterone for the first week after brain injury improved NOR memory at the 4-week time point in both sham and brain-injured rats and additionally attenuated the injury-induced increase in the excitability of neurons and the frequency of spontaneous EPSCs. The effect of progesterone on cellular excitability changes after injury may be related to its ability to decrease the mRNA expression of the ß3 subunit of the voltage-gated sodium channel and increase the expression of the neuronal excitatory amino acid transporter 3 in the medial PFC in sham- and brain-injured animals and also increase glutamic acid decarboxylase mRNA expression in sham- but not brain-injured animals. Progesterone treatment did not affect injury-induced changes in the EPM test. These results demonstrate that administration of progesterone immediately after TBI in 11-day-old rats reduces cognitive deficits in adolescence, which may be mediated by progesterone-mediated regulation of excitatory signaling mechanisms within the medial PFC.

Minocycline Transiently Reduces Microglia/Macrophage Activation but Exacerbates Cognitive Deficits Following Repetitive Traumatic Brain Injury in the Neonatal Rat.

Elevated microglial/macrophage-associated biomarkers in the cerebrospinal fluid of infant victims of abusive head trauma (AHT) suggest that these cells play a role in the pathophysiology of the injury. In a model of AHT in 11-day-old rats, 3 impacts (24 hours apart) resulted in spatial learning and memory deficits and increased brain microglial/macrophage reactivity, traumatic axonal injury, neuronal degeneration, and cortical and white-matter atrophy. The antibiotic minocycline has been effective in decreasing injury-induced microglial/macrophage activation while simultaneously attenuating cellular and functional deficits in models of neonatal hypoxic ischemia, but the potential for this compound to rescue deficits after impact-based trauma to the immature brain remains unexplored. Acute minocycline administration in this model of AHT decreased microglial/macrophage reactivity in the corpus callosum of brain-injured animals at 3 days postinjury, but this effect was lost by 7 days postinjury. Additionally, minocycline treatment had no effect on traumatic axonal injury, neurodegeneration, tissue atrophy, or spatial learning deficits. Interestingly, minocycline-treated animals demonstrated exacerbated injury-induced spatial memory deficits. These results contrast with previous findings in other models of brain injury and suggest that minocycline is ineffective in reducing microglial/macrophage activation and ameliorating injury-induced deficits following repetitive neonatal traumatic brain injury.

Cathepsin L Mediates the Degradation of Novel APP C-Terminal Fragments.

Alzheimer's disease (AD) is characterized by the deposition of amyloid ß (Aß), a peptide generated from proteolytic processing of its precursor, amyloid precursor protein (APP). Canonical APP proteolysis occurs via α-, ß-, and γ-secretases. APP is also actively degraded by protein degradation systems. By pharmacologically inhibiting protein degradation with ALLN, we observed an accumulation of several novel APP C-terminal fragments (CTFs). The two major novel CTFs migrated around 15 and 25 kDa and can be observed across multiple cell types. The process was independent of cytotoxicity or protein synthesis. We further determine that the accumulation of the novel CTFs is not mediated by proteasome or calpain inhibition, but by cathepsin L inhibition. Moreover, these novel CTFs are not generated by an increased amount of BACE. Here, we name the CTF of 25 kDa as η-CTF (eta-CTF). Our data suggest that under physiological conditions, a subset of APP undergoes alternative processing and the intermediate products, the 15 kDa CTFs, and the η-CTFs aret rapidly degraded and/or processed via the protein degradation machinery, specifically, cathepsin L.

Experimental traumatic brain injury alters ethanol consumption and sensitivity.

Altered alcohol consumption patterns after traumatic brain injury (TBI) can lead to significant impairments in TBI recovery. Few preclinical models have been used to examine alcohol use across distinct phases of the post-injury period, leaving mechanistic questions unanswered. To address this, the aim of this study was to describe the histological and behavioral outcomes of a noncontusive closed-head TBI in the mouse, after which sensitivity to and consumption of alcohol were quantified, in addition to dopaminergic signaling markers. We hypothesized that TBI would alter alcohol consumption patterns and related signal transduction pathways that were congruent to clinical observations. After midline impact to the skull, latency to right after injury, motor deficits, traumatic axonal injury, and reactive astrogliosis were evaluated in C57BL/6J mice. Amyloid precursor protein (APP) accumulation was observed in white matter tracts at 6, 24, and 72 h post-TBI. Increased intensity of glial fibrillary acidic protein (GFAP) immunoreactivity was observed by 24 h, primarily under the impact site and in the nucleus accumbens, a striatal subregion, as early as 72 h, persisting to 7 days, after TBI. At 14 days post-TBI, when mice were tested for ethanol sensitivity after acute high-dose ethanol (4 g/kg, intraperitoneally), brain-injured mice exhibited increased sedation time compared with uninjured mice, which was accompanied by deficits in striatal dopamine- and cAMP-regulated neuronal phosphoprotein, 32 kDa (DARPP-32) phosphorylation. At 17 days post-TBI, ethanol intake was assessed using the Drinking-in-the-Dark paradigm. Intake across 7 days of consumption was significantly reduced in TBI mice compared with sham controls, paralleling the reduction in alcohol consumption observed clinically in the initial post-injury period. These data demonstrate that TBI increases sensitivity to ethanol-induced sedation and affects downstream signaling mediators of striatal dopaminergic neurotransmission while altering ethanol consumption. Examining TBI effects on ethanol responsitivity will improve our understanding of alcohol use post-TBI in humans.

Deletion of the p53 tumor suppressor gene improves neuromotor function but does not attenuate regional neuronal cell loss following experimental brain trauma in mice.

Deletion of the tumor suppressor gene p53 has been shown to improve the outcome in experimental models of focal cerebral ischemia and kainate-induced seizures. To evaluate the potential role of p53 in traumatic brain injury, genetically modified mice lacking a functional p53 gene (p53(-/-), n = 9) and their wild-type littermates (p53(+/+), n = 9) were anesthetized and subjected to controlled cortical impact (CCI) experimental brain trauma. After brain injury, neuromotor function was assessed by using composite neuroscore and rotarod tests. By 7 days posttrauma, p53(-/-) mice exhibited significantly improved neuromotor function, in the composite neuroscore (P = 0.002) as well as in two of three individual tests, when compared with brain-injured p53(+/+) animals. CCI resulted in the formation of a cortical cavity (mean volume = 6.1 mm(3)) 7 days postinjury in p53(+/+) as well as p53(-/-) mice. No difference in lesion volume was detected between the two genotypes (P = 0.95). Although significant cell loss was detected in the ipsilateral hippocampus and thalamus of brain-injured animals, no differences between p53(+/+) and p53(-/-) mice were detected. Although our results suggest that lack of the p53 gene results in augmented recovery of neuromotor function following experimental brain trauma, they do not support a role for p53 acting as a mediator of neuronal death in this context, underscoring the complexity of its role in the injured brain.

TrkB gene transfer does not alter hippocampal neuronal loss and cognitive deficits following traumatic brain injury in mice.

PURPOSE: The ability of brain-derived neurotrophic factor (BDNF) to attenuate secondary damage and influence behavioral outcome after experimental traumatic brain injury (TBI) remains controversial. Because TBI can result in decreased expression of the trkB receptor, thereby preventing BDNF from exerting potential neuroprotective effects, the contribution of both BDNF and its receptor trkB to hippocampal neuronal loss and cognitive dysfunction were evaluated. METHODS: Full-length trkB was overexpressed in the left hippocampus of adult C57Bl/6 mice using recombinant adeno-associated virus serotype 2/5 (rAAV 2/5). EGFP (enhanced green fluorescent protein) expression was present at two weeks after AAV-EGFP injection and remained sustained up to four weeks after the injection. At 2 weeks following gene transduction, mice were subjected to parasagittal controlled cortical impact (CCI) brain injury, followed by either BDNF or PBS infusion into the hippocampus. RESULTS: No differences were observed in learning ability at two weeks post-injury or in motor function from 48 hours to two weeks among treatment groups. The number of surviving pyramidal neurons in the CA2-CA3 region of the hippocampus was also not different among treatment groups. CONCLUSIONS: These data suggest that neither overexpression of trkB, BNDF infusion or their combination affects neuronal survival or behavioral outcome following experimental TBI in mice.

Role of the transcription factor E2F1 in CXCR4-mediated neurotoxicity and HIV neuropathology.

This study sought to determine the role of the transcription factor E2F1 in CXCR4-mediated neurotoxicity and HIV neuropathology. We studied the effect of the HIV envelope protein gp120 on the expression of E2F1-dependent apoptotic proteins in human and rodent neurons and examined the expression pattern of E2F1 in the brain of HIV-infected individuals. Our findings suggest that in cultured neurons gp120 increased E2F1 levels in the nucleus, stimulated its transcriptional activity and enhanced the expression of the E2F1 target proteins Cdc2 and Puma. Studies with neuronal cultures from E2F1 deficient mice demonstrated that the transcription factor is required for gp120-induced neurotoxicity and up-regulation of Cdc2 and Puma. Levels of E2F1 protein were greater in the nucleus of neurons in brains of HIV-infected patients exhibiting dementia when compared to HIV-negative subjects or HIV-positive neurologically normal patients. Overall, these studies indicate that E2F1 is primarily involved in CXCR4-mediated neurotoxicity and HIV neuropathogenesis.

Common patterns of bcl-2 family gene expression in two traumatic brain injury models.

Cell death/survival following traumatic brain injury (TBI) may be a result of alterations in the intracellular ratio of death and survival factors. Bcl-2 family genes mediate both cell survival and the initiation of cell death. Using lysate RNase protection assays, mRNA expression of the anti-cell death genes Bcl-2 and Bcl-xL, and the pro-cell death gene Bax, was evaluated following experimental brain injuries in adult male Sprague-Dawley rats. Both the lateral fluid-percussion (LFP) and the lateral controlled cortical impact (LCI) models of TBI showed similar patterns of gene expression. Anti-cell death bcl-2 and bcl-xL mRNAs were attenuated early and tended to remain depressed for at least 3 days after injury in the cortex and hippocampus ipsilateral to injury. Pro-cell death bax mRNA was elevated in these areas, usually following the decrease in anti-cell death genes. These common patterns of gene expression suggest an important role for Bcl-2 genes in cell death and survival in the injured brain. Understanding the regulation of these genes may facilitate the development of new therapeutic strategies for a condition that currently has no proven pharmacologic treatments.

Inhibition of vascular endothelial growth factor receptor (VEGFR) signaling by BSF476921 attenuates regional cerebral edema following traumatic brain injury in rats.

PURPOSE: In the present study we assessed the ability of BSF476921, an inhibitor of vascular endothelial growth factor receptor (VEGFR) kinase signal transduction, to reduce edema formation and neurologic motor dysfunction following lateral fluid percussion (FP) brain injury in rats. METHODS: Anesthetized adult male rats were subjected to either lateral FP brain injury of moderate severity (n = 37) or sham injury (n = 22, surgery without brain injury). Animals were randomized to receive i.p. injections of either BSF476921 (30 mg/kg bw; injured n = 15, sham n = 11) or sterile water (injured n = 14, sham n = 11) at 1, 11 and 22 hours post-injury. After assessment of motor function using a standard 28-point neuroscore, animals were sacrificed 24 hours following trauma and their brains evaluated for regional water content using the wet-weight/dry-weight technique. RESULTS: Although brain-injured animals showed a significant motor deficit compared to uninjured animals, no differences were detected between BSF476921- and vehicle-treated animals at the acute 24 hour post-injury time point. However, BSF476921 significantly attenuated regional edema formation in brain-injured animals in the ipsilateral hippocampus (p < 0.05) and in the cortex adjacent to the injury (p < 0.05) when compared to vehicle treatment. CONCLUSIONS: To our knowledge, this is the first report of a small molecule VEGFR kinase inhibitor reducing cerebral edema in a widely accepted model of brain injury.

Cell death mechanisms following traumatic brain injury.

Neuronal and glial cell death and traumatic axonal injury contribute to the overall pathology of traumatic brain injury (TBI) in both humans and animals. In both head-injured humans and following experimental brain injury, dying neural cells exhibit either an apoptotic or a necrotic morphology. Apoptotic and necrotic neurons have been identified within contusions in the acute post-traumatic period, and in regions remote from the site of impact in the days and weeks after trauma, while degenerating oligodendrocytes and astrocytes have been observed within injured white matter tracts. We review and compare the regional and temporal patterns of apoptotic and necrotic cell death following TBI and the possible mechanisms underlying trauma-induced cell death. While excitatory amino acids, increases in intracellular calcium and free radicals can all cause cells to undergo apoptosis, in vitro studies have determined that neural cells can undergo apoptosis via many other pathways. It is generally accepted that a shift in the balance between pro- and anti-apoptotic protein factors towards the expression of proteins that promote death may be one mechanism underlying apoptotic cell death. The effect of TBI on cellular expression of survival promoting-proteins such as Bcl-2, Bcl-xL, and extracellular signal-regulated kinases, and death-inducing proteins such as Bax, c-Jun N-terminal kinase, tumor-suppressor gene, p53, and the calpain and caspase families of proteases are reviewed. In light of pharmacologic strategies that have been devised to reduce the extent of apoptotic cell death in animal models of TBI, our review also considers whether apoptosis may serve a protective role in the injured brain. Together, these observations suggest that cell death mechanisms may be representative of a continuum between apoptotic and necrotic pathways.

Continued in situ DNA fragmentation of microglia/macrophages in white matter weeks and months after traumatic brain injury.

Paraffin-embedded material from the pons of head-injured patients whose disability could be attributed to diffuse traumatic axonal injury, and controls, was identified from the department's archive. The cases were divided into three groups based on survival, viz Group 1 (n = 5) who survived for between 4 and 8 weeks, Group 2 (n = 5) for between 3 and 9 months, and Group 3 (n = 5) who survived for more that 12 months. Sections were stained by the TUNEL (TdT-mediated UTP nick end labelling) technique, and by H&E, LFB/CV and immunohistochemically for astrocytes (GFAP) and microglia/macrophages (CD68). Microscopic abnormalities were mapped onto line diagrams of two levels of the pons and quantitation of the response determined by an eye-piece graticule placed over the medial lemmisci, cortico-spinal and transverse fiber tracts. Data were pooled by region of interest. In the H&E and LFB/CV stained sections, there was variable pallor of staining in ascending and descending fiber tracts due to loss of myelin: within these same tracts there was an astrocytosis and increased numbers of microglia/macrophages compared with controls. In the white matter tracts of the controls, there was on average 1-2 TUNEL+ cells per unit area. In contrast, there were on average 2-16 TUNEL+ cells in the cortico-spinal tracts and in the medial lemnisci of all groups of head-injured patients. CD68+ cells co-located with the TUNEL+, and their number mirrored the TUNEL + staining with on average 16-30 cells per unit area in Group 1, 14-27 cells per unit area in Group 2, and 12-14 cells per unit area in Group 3. There was a statistical association between the TUNEL+ and CD68+ cells. Few changes were seen in the transverse fiber tracts of the pons. These findings indicate that most of the in situ DNA fragmentation occurred in microglia/macrophages in ascending and descending fiber tracts of the brain stem in which by conventional light microscopy there is Wallerian degeneration. However, in addition, a few TUNEL+ oligodendrocyte-like cells were also seen.

Temporal alterations in cellular Bax:Bcl-2 ratio following traumatic brain injury in the rat.

Cell death/survival following CNS injury may be a result of alterations in the intracellular ratio of death and survival factors. Using immunohistochemistry, Western analysis and in situ hybridization, the expression of the anti-cell death protein, Bcl-2, and the pro-cell death protein, Bax, was evaluated following lateral fluid-percussion (FP) brain injury of moderate severity (2.3-2.6 atm) in adult male Sprague-Dawley rats. By 2 h post-injury, a marked reduction of cellular Bcl-2-immunoreactivity (IR) and a mild decrease in cellular Bax IR were observed in the temporal and occipital cortices, and in the hippocampal CA3 ipsilateral to the site of impact. These decreases in Bcl-2 and Bax IR appeared to precede the overt cell loss in these regions that was evident at 24 h. Immunoblot analysis supported the immunohistochemical data, with a modest but significant reduction in the intensities of both the Bcl-2 and Bax protein bands at 2 h (p < 0.05 compared to sham levels). However, the Bax:Bcl-2 ratio increased significantly at 2 h (2.28 +/- 0.13) and remained elevated up to 7 days (2.05 +/- 0.13) post-injury compared to sham-injured control tissue (1.62 +/- 0.10, p < 0.05). Furthermore, cortical, but not hippocampal, levels of Bax protein increased by 25% (p < 0.05 compared to sham-injured controls) at 24 h post-injury, and returned to control levels by 7 days. In situ hybridization analysis of Bax mRNA revealed increased cellular grain density in the injured cortex (p < 0.05 compared to sham-injured brains), but not in the CA3 region of the injured hippocampus. No injury-induced changes in the expression of Bcl-2 mRNA were observed in any brain region. Taken together, these data suggest that the association between regional post-traumatic cell death and alterations in the cellular ratio of Bcl-2 and Bax may be, in part, due to alterations in mRNA and/or protein expression of the Bcl-2 family of proteins.

Structural and functional damage sustained by mitochondria after traumatic brain injury in the rat: evidence for differentially sensitive populations in the cortex and hippocampus.

The cellular and molecular pathways initiated by traumatic brain injury (TBI) may compromise the function and structural integrity of mitochondria, thereby contributing to cerebral metabolic dysfunction and cell death. The extent to which TBI affects regional mitochondrial populations with respect to structure, function, and swelling was assessed 3 hours and 24 hours after lateral fluid-percussion brain injury in the rat. Significantly less mitochondrial protein was isolated from the injured compared with uninjured parietotemporal cortex, whereas comparable yields were obtained from the hippocampus. After injury, cortical and hippocampal tissue ATP concentrations declined significantly to 60% and 40% of control, respectively, in the absence of respiratory deficits in isolated mitochondria. Mitochondria with ultrastructural morphologic damage comprised a significantly greater percent of the population isolated from injured than uninjured brain. As determined by photon correlation spectroscopy, the mean mitochondrial radius decreased significantly in injured cortical populations (361 +/- 40 nm at 24 hours) and increased significantly in injured hippocampal populations (442 +/- 36 at 3 hours) compared with uninjured populations (Ctx: 418 +/- 44; Hipp: 393 +/- 24). Calcium-induced deenergized swelling rates of isolated mitochondrial populations were significantly slower in injured compared with uninjured samples, suggesting that injury alters the kinetics of mitochondrial permeability transition (MPT) pore activation. Cyclosporin A (CsA)-insensitive swelling was reduced in the cortex, and CsA-sensitive and CsA-insensitive swelling both were reduced in the hippocampus, demonstrating that regulated MPT pores remain in mitochondria isolated from injured brain. A proposed mitochondrial population model synthesizes these data and suggests that cortical mitochondria may be depleted after TBI, with a physically smaller, MPT-regulated population remaining. Hippocampal mitochondria may sustain damage associated with ballooned membranes and reduced MPT pore calcium sensitivity. The heterogeneous mitochondrial response to TBI may underlie posttraumatic metabolic dysfunction and contribute to the pathophysiology of TBI.

Transplanted neural stem cells survive, differentiate, and improve neurological motor function after experimental traumatic brain injury.

OBJECTIVE: Using the neural stem cell (NSC) clone C17.2, we evaluated the ability of transplanted murine NSCs to attenuate cognitive and neurological motor deficits after traumatic brain injury. METHODS: Nonimmunosuppressed C57BL/6 mice (n = 65) were anesthetized and subjected to lateral controlled cortical impact brain injury (n = 52) or surgery without injury (sham operation group, n = 13). At 3 days postinjury, all brain-injured animals were reanesthetized and randomized to receive stereotactic injection of NSCs or control cells (human embryonic kidney cells) into the cortex-hippocampus interface in either the ipsilateral or the contralateral hemisphere. One group of animals (n = 7) was killed at either 1 or 3 weeks postinjury to assess NSC survival in the acute posttraumatic period. Motor function was evaluated at weekly intervals for 12 weeks in the remaining animals, and cognitive (i.e., learning) deficits were assessed at 3 and 12 weeks after transplantation. RESULTS: Brain-injured animals that received either ipsilateral or contralateral NSC transplants showed significantly improved motor function in selected tests as compared with human embryonic kidney cell-transplanted animals during the 12-week observation period. Cognitive dysfunction was unaffected by transplantation at either 3 or 12 weeks postinjury. Histological analyses showed that NSCs survive for as long as 13 weeks after transplantation and were detected in the hippocampus and/or cortical areas adjacent to the injury cavity. At 13 weeks, the NSCs transplanted ipsilateral to the impact site expressed neuronal (NeuN) or astrocytic (glial fibrillary acidic protein) markers but not markers of oligodendrocytes (2'3'cyclic nucleotide 3'-phosphodiesterase), whereas the contralaterally transplanted NSCs expressed neuronal but not glial markers (double-labeled immunofluorescence and confocal microscopy). CONCLUSION: These data suggest that transplanted NSCs can survive in the traumatically injured brain, differentiate into neurons and/or glia, and attenuate motor dysfunction after traumatic brain injury.