Posttraumatic hypothermia reduces polymorphonuclear leukocyte accumulation following spinal cord injury in rats

The present study addresses the effects of moderate posttraumatic hypothermia (32 degrees C) on the temporal and regional profile of polymorphonuclear leukocyte (PMNL) accumulation after traumatic spinal cord injury (SCI). We hypothesized that posttraumatic hypothermia would reduce the degree of inflammation by reducing PMNL infiltration. Rats underwent moderate spinal cord injury at T10 using the NYU impactor device. In the first study, the temporal profile of myeloperoxidase (MPO) activity (a marker of neutrophil accumulation) under normothermic (37 degrees C) conditions was determined. The animals were allowed to survive for 3 or 24 h, or 3 or 7 days after SCI. Spinal cords were dissected into five segments rostral and caudal to the injury site. Additional animals were studied for the immunocytochemical visualization of MPO. In the second study, rats were sacrificed at 24 h after a monitoring period of normothermia (36.5 degrees C/3 h) or hypothermia (32.4 degrees C/3 h) with their controls. In the time course studies, MPO enzymatic activity was significantly increased at 3 and 24 h within the traumatized T10 segment compared to controls. MPO activity was also increased at 3 h within the rostral T8 and T9 segments and caudal T11 and T12 segments compared to controls. At 24 h after trauma, MPO activity remained elevated within both the rostral and caudal segments compared to control. By 3 days, the levels of MPO activity were reduced compared to the 24-h values but remained significantly different from control. Neutrophils that exhibited MPO immunoreactivity were seen at 6 and 24 h, with a higher number at 3 days. PMNLs were located within the white and gray matter of the lesion and both rostral and caudal to the injury site. Posttraumatic hypothermia reduced MPO activity at 24 h in the injured spinal cord segment, compared to normothermic values. The results of this study indicate that a potential mechanism by which hypothermia improves outcome following SCI is by attenuating posttraumatic inflammation.     

Behavioral and histological characterization of unilateral cervical spinal cord contusion injury in rats

Most experimental studies of spinal cord injury (SCI) in rats damage the thoracic cord, with the consequent functional loss being due to interruption of long tracts connecting the caudal spinal cord to the rostral nervous system. Less work has been done evaluating injury to the cervical cord, even though it is the most common level of human SCI. In addition to the long tracts, the cervical spinal cord contains the sensory and motor neurons responsible for upper extremity function. The purpose of this study was to further develop a rat model of cervical spinal cord contusion injury using a modified NYU/MASCIS weight drop device. Mild (6.25 mm) and moderate (12.5 mm) C5 unilateral injuries were produced. Behavioral recovery was examined using a grooming test, a paw preference test, a walkway test (The Catwalk), and a horizontal ladder test. Histological outcome measures included sparing at the lesion epicenter, sparing throughout the extent of the lesion, quantification of myelin loss rostral and caudal to the lesion, and motor neuron counts. Compared to controls, animals receiving SCI exhibited injury severity-specific deficits in forelimb, locomotor, and hindlimb function persisting for 6-weeks post-SCI. Histological analysis revealed ipsilateral containment of the injury, and differentiation between groups on all measures except motor neuron counts. This model has many advantages: (1) minimal animal care requirements post-SCI, (2) within subject controls, (3) functional loss involves primarily the ipsilateral forelimb, and (4) it is a behavioral and histological model for both gray and white matter damage caused by contusive SCI.     

Neuroprotective assessment of prolonged local hypothermia post contusive spinal cord injury in rodent model

Background Context

Although general hypothermia is recognized as a clinically applicable neuroprotective intervention, acute moderate local hypothermia post contusive spinal cord injury (SCI) is being considered a more effective approach. Previously, we have investigated the feasibility and safety of inducing prolonged local hypothermia in the central nervous system of a rodent model.

亚低温对脊髓损伤后神经细胞凋亡的影响

目的观察大鼠脊髓损伤(SCI)细胞凋亡现象及亚低温对细胞凋亡的影响。方法大鼠SCI后分别于8h、24h、7d取材，采用常规病理HE染色和末端脱氧核苷酸转移酶(TdT)介导的dutp缺口末端标记技术(TNEUL)，研究亚低温对大鼠SCI后神经细胞凋亡的影响。结果SCI后常温组8h灰质区出现较多凋亡细胞，24h时白质和灰质内均有凋亡细胞分布，7d后凋亡细胞多见于白质；亚低温组凋亡细胞明显减少(P＜0．05)。结论亚低温明显减少SCI后细胞凋亡的发生，从病理上为亚低温脊髓保护提供了可靠的依据。     

Mechanistic insights into posttraumatic syringomyelia based on a novel in vivo animal model. Laboratory investigation

OBJECT: Although posttraumatic syringomyelia (PTS) develops in up to 30% of patients after spinal cord injury (SCI), the pathophysiology of this debilitating complication is incompletely understood. To provide greater insight into the mechanisms of this degenerative sequela of SCI, the authors developed and characterized a novel model of PTS. METHODS: The spinal cords of 64 female Wistar rats were injured by 35-g modified aneurysm clip compression at the level of T6-7. Kaolin (5 microl of 500 mg/ml solution) was then injected into the subarachnoid space rostral to the site of the injury to induce inflammatory arachnoiditis in 22 rats. Control groups received SCI alone (in 21 rats), kaolin injection alone (in 15 rats), or laminectomy and durotomy alone without injury (sham surgery in 6 rats). RESULTS: The combination of SCI and subarachnoid kaolin injection resulted in a significantly greater syrinx formation and perilesional myelomalacia than SCI alone; SCI and kaolin injection significantly attenuated locomotor recovery and exacerbated neuropathic pain (mechanical allodynia) compared with SCI alone. We observed that combined SCI and kaolin injection significantly increased the number of terminal deoxytransferase-mediated deoxyuridine triphosphate nick-end labeled-positive cells at 7 days after injury (p<0.05 compared with SCI alone) and resulted in a significantly greater extent of astrogliosis and macrophage/microglial-associated inflammation at the lesion (p<0.05). CONCLUSIONS: The combination of compressive/contusive SCI with induced arachnoiditis results in severe PTS and perilesional myelomalacia, which is associated with enhanced inflammation, astrogliosis, and apoptotic cell death. The development of delayed neurobehavioral deficits and neuropathic pain in this model accurately reflects the key pathological and clinical conditions of PTS in humans.     

Changes in Properties of Spinal Dorsal Horn Neurons and Their Sensitivity to Morphine after Spinal Cord Injury in the Rat

Background: To gain a better understanding of spinal cord injury (SCI)-induced central neuropathic pain, the authors investigated changes in properties of spinal dorsal horn neurons located rostrally and caudally to the lesion and their sensitivity to morphine in rats after SCI.

Methods: The right spinal cord of Sprague-Dawley rats was hemisected at the level of L2. At 10 to 14 days after the SCI, when mechanical hyperalgesia/allodynia had fully developed, spontaneous activity and evoked responses to mechanical stimuli of wide-dynamic-range (WDR) and high-threshold neurons rostral and caudal to the lesion were recorded. Effects of cumulative doses of systemic (0.1-3 mg/kg) and spinal (0.1-5 [mu]g) administration of morphine on spontaneous activity and evoked responses to the stimuli of the neurons were evaluated.

Results: Spontaneous activity significantly increased in WDR neurons both rostral and caudal to the SCI site, but high-frequency background discharges with burst patterns were only observed in neurons rostral to the SCI site. Significant increases in responses to the mechanical stimuli were seen both in WDR and high-threshold neurons located both rostrally and caudally to the lesion. The responses to nonnoxious and noxious stimuli were significantly greater in caudal WDR neurons than in rostral WDR neurons. In contrast, the responses to pinch stimuli were significantly higher in rostral high-threshold neurons than those in caudal high-threshold neurons. Systemically administered morphine had a greater effect on responses to nonnoxious and noxious stimuli of rostral WDR neurons than those of caudal WDR neurons. Spinally administered morphine significantly suppressed responses of WDR neurons in SCI animals to nonnoxious stimuli compared with those in sham-operated control animals.     

Brain-derived neurotrophic factor suppresses delayed apoptosis of oligodendrocytes after spinal cord injury in rats

We evaluated the effect of brain-derived neurotrophic factor (BDNF) on cell death after spinal cord injury. A rat spinal cord injury model was produced by static load, and continuous intrathecal BDNF or vehicle infusion was carried out either immediately or 3 days after the injury. Cell death was examined by nuclear staining and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL). After injury, typical apoptotic cells were observed. Double staining with TUNEL and specific cell markers revealed that, soon after the injury, the apoptotic or necrotic cells at the injury site were neurons and microglia. One week after the injury, apoptotic oligodendrocytes, but not apoptotic astrocytes, were observed in the white matter rostral and caudal to the injury site, whereas few apoptotic cells were found in the gray matter. The immediate BDNF treatment significantly reduced the number of TUNEL-positive cells in the adjacent rostral site 1 and 2 weeks after the injury, and in the adjacent caudal site 3 days and 1 week after the injury, even though there was no significant difference between BDNF-treated and control rats at the injury site itself. In addition, similar antiapoptotic effects were observed in these regions 1 week after injury in rats that received BDNF treatment from the third day after injury. These findings suggest that BDNF suppresses delayed apoptosis of oligodendrocytes after spinal cord injury, for which even delayed injections are effective. BDNF administration may therefore be useful for the clinical treatment of spinal cord injury through the suppression of secondary events.     

Changes in properties of spinal dorsal horn neurons and their sensitivity to morphine after spinal cord injury in the rat

BACKGROUND: To gain a better understanding of spinal cord injury (SCI)-induced central neuropathic pain, the authors investigated changes in properties of spinal dorsal horn neurons located rostrally and caudally to the lesion and their sensitivity to morphine in rats after SCI. METHODS: The right spinal cord of Sprague-Dawley rats was hemisected at the level of L2. At 10 to 14 days after the SCI, when mechanical hyperalgesia/allodynia had fully developed, spontaneous activity and evoked responses to mechanical stimuli of wide-dynamic-range (WDR) and high-threshold neurons rostral and caudal to the lesion were recorded. Effects of cumulative doses of systemic (0.1-3 mg/kg) and spinal (0.1-5 microg) administration of morphine on spontaneous activity and evoked responses to the stimuli of the neurons were evaluated. RESULTS: Spontaneous activity significantly increased in WDR neurons both rostral and caudal to the SCI site, but high-frequency background discharges with burst patterns were only observed in neurons rostral to the SCI site. Significant increases in responses to the mechanical stimuli were seen both in WDR and high-threshold neurons located both rostrally and caudally to the lesion. The responses to nonnoxious and noxious stimuli were significantly greater in caudal WDR neurons than in rostral WDR neurons. In contrast, the responses to pinch stimuli were significantly higher in rostral high-threshold neurons than those in caudal high-threshold neurons. Systemically administered morphine had a greater effect on responses to nonnoxious and noxious stimuli of rostral WDR neurons than those of caudal WDR neurons. Spinally administered morphine significantly suppressed responses of WDR neurons in SCI animals to nonnoxious stimuli compared with those in sham-operated control animals. CONCLUSIONS: The findings suggest that changes in properties of spinal dorsal horn neurons after SCI are caused by different mechanisms, depending on the classification of the neurons and their segmental locations.     

Diffusion tensor imaging predicts hyperacute spinal cord injury severity

Experimental strategies that focus on ventral white matter (VWM) preservation during the hyperacute phase hold great potential for our improved understanding of functional recovery following traumatic spinal cord injury (SCI). Critical comparisons of human SCI to rapidly accumulating data derived from rodent models are limited by a basic lack of in vivo measures of subclinical pathophysiologic changes and white matter damage in the spinal cord. Spinal cord edema and intraparenchymal hemorrhage demonstrated with routine MR sequences have limited value for predicting functional outcomes in SCI animal models and in human patients. We recently demonstrated that in vivo derived diffusion tensor imaging (DTI) parameters are sensitive and specific biomarkers for spinal cord white matter damage. In this study, non-invasive in vivo DTI was utilized to evaluate the white matter of C57BL/6 mice 3 h after mild (0.3 mm), moderate (0.6 mm), or severe (0.9 mm) contusive SCI. In the hyperacute phase, relative anisotropy maps provided excellent gray-white matter contrast in all degrees of injury. In vivo DTI-derived measurements of axial diffusion differentiated between mild, moderate, and severe contusive SCI with good histological correlation. Cross-sectional regional measurements of white matter injury severity between dorsal columns and VWM varied with increasing cord displacement in a pattern consistent with spinal cord viscoelastic properties.     

大鼠脊髓损伤中的细胞凋亡及甲基强的松龙的干预作用

目的：探讨脊髓损伤（SCI）继发损伤机制,研究损伤脊髓细胞的凋亡及其意义,观察甲基强的松龙（MP）对细胞凋亡的影响。方法：使用改良Allen法制作大鼠急性SCI模型,实验分3组,假损伤（脊髓未受打击）,损伤组及MP治疗组,采用HE,荧光Hoechst 33342,TUNEL(末端脱氧核苷转移酶介导的脱氧尿苷三磷酸生物素缺口末端标记技术）等技术观察SCI后4h,8h,3d,7d,14d,21d及28d时损伤中心及邻近节段脊髓细胞的凋亡,治疗组损伤后30min给予大剂量MP,比较MP治疗组与损伤组脊髓细胞凋亡的变化,同时平行观察大鼠神经学和组织学恢复情况及两组神经丝蛋白（NF）含量的变化。结果：假损伤组各检测方法未见脊髓细胞凋亡,损伤组大鼠急性SCI后1d开始出现脊髓细胞凋亡,3d达高峰,自损伤中心向头尾端递减分布,持续21d,MP治疗组在伤后3d及7d凋亡脊髓细胞较损伤组显著减少,神经学恢复及组织学评分较损伤组有显著性提高,结论：凋亡是SCI后脊髓神经元死亡的一种重要方式,在继发性损伤中起极为重要的作用。MP的治疗作用可能与其干预SCI后细胞凋亡有关。     

大鼠脊髓损伤后巢蛋白在脊髓组织中的表达

目的探讨大鼠脊髓损伤后巢蛋白(nestin)的表达规律及其意义。方法30只Wister成年大鼠,随机分为正常对照组(A组)、损伤组(B组)。采用Allen打击模型(25g·cm),在T10段造成急性脊髓损伤,于损伤后1d、3d、1周、4周、8周进行取材,对距离损伤中心5mm处脊髓进行nestin免疫组化检测。应用图像分析软件进行nestin阳性区域面积侧算。结果A组脊髓室管膜细胞只可见极少数细胞胞浆内nestin表达,白质中几乎无表达。B组中nestin于损伤后24h表达于室管膜以及软膜,灰质和白质亦有少量表达,1周达到高峰(P<0.05),4周明显下降,8周时很少或几乎无表达。结论脊髓组织的许多部位可能存在具有分化和更新潜能的祖细胞,脊髓损伤后这些细胞被激活,在功能恢复中可能发挥着重要的作用。     

Neural circuitry of the adult rat central nervous system after spinal cord injury: a study using fast blue and the Bartha strain of pseudorabies virus

The distribution of retrogradely and transneuronally labeled neurons in the adult rat brain and spinal cord after contusive mid-thoracic spinal cord injury (SCI) was studied using Fast Blue (FB) and the Bartha strain of pseudorabies virus (PRV), respectively. When FB was injected into the distal spinal cord at 2 days after graded SCI at the 10th vertebral level, labeled neurons were consistently found 7 days later in supraspinal areas that normally project to the spinal cord. The number of FB-labeled neurons decreased as the injury severity increased. An inverse correlation between the number of FB-labeled neurons and injury severity was seen in most investigated brain nuclei with coefficient of correlations (r) ranging from -0.84 in the red nucleus to -0.92 in the raphe nuclei. The coefficient of correlation was relatively poor in the motor cortex (r = -0.63), where a mild injury (6.25 g.cm) resulted in a 99% damage of the corticospinal tract. Such a prominent difference between the corticospinal tract and other descending pathways can be related to the difference in location of these pathways within the adult rat spinal cord. When PRV was injected into the right sciatic nerve one month after the injury, labeled cells were consistently identified 5 days later in the spinal cord rostral to the injury and in certain supraspinal regions that regulate autonomic outflow. In these nuclei, the distribution and number of PRV-labeled neurons markedly decreased after SCI as compared to the control group. In contrast, PRV-labeled neurons were inconsistently found in the supraspinal nuclei that contribute to somatic motor outflow in normal controls and no labeling was observed in these nuclei after injury. These results demonstrate that (1) a proportion of neural network across the injured spinal cord has been spared after acute contusive SCI, (2) the proportion of spared axons of a particular pathway is closely correlated to the injury severity and the position of that pathway, and (3) the transneuronal labeling method using PRV may provide a unique approach to investigate multi-synaptic neural circuitry of the central autonomic control after SCI, but its application to the somatic motor system is limited.     

Histopathological and behavioral characterization of a novel cervical spinal cord displacement contusion injury in the rat

Cervical contusive trauma accounts for the majority, of human spinal cord injury (SCI), yet experimental use of cervical contusion injury models has been limited. Considering that (1) the different ways of injuring the spinal cord (compression, contusion, and transection) induce very different processes of tissue damage and (2) the architecture of the spinal cord is not uniform, it is important to use a model that is more clinically applicable to human SCI. Therefore, in the current study we have developed a rat model of contusive, cervical SCI using the Electromagnetic Spinal Cord Injury Device (ESCID) developed at Ohio State University (OSU) to induce injury by spinal cord displacement. We used the device to perform mild, moderate and severe injuries (0.80, 0.95, and 1.1 mm displacements, respectively) with a single, brief displacement of <20 msec upon the exposed dorsal surface of the C5 cervical spinal cord of female (180-200 g) Fischer rats. Characterization of the model involved the analysis of the temporal histopathological progression of the injury over 9 weeks using histochemical stains to analyze white and gray mater integrity and immunohistochemistry to examine cellular changes and physiological responses within the injured spinal cord. Accompanying the histological analysis was a comprehensive determination of the behavioral functionality of the animals using a battery of motor tests. Characterization of this novel model is presented to enable and encourage its future use in the design and experimental testing of therapeutic strategies that may be used for human SCI.     

Detrimental effects of systemic hyperthermia on locomotor function and histopathological outcome after traumatic spinal cord injury in the rat.

OBJECTIVE: Posttraumatic hyperthermia has been demonstrated to worsen neurological outcome in models of brain injury. The purpose of this study was to examine the effects of systemic hyperthermia on locomotor and morphological outcome measures after traumatic spinal cord injury (SCI) in the rat. METHODS: After a T10 laminectomy, spinal cord contusions were produced from a height of 12.5 mm onto exposed cords (NYU Impactor; New York University Neurosurgery Laboratory, New York, NY) in adult rats that were divided into three groups. Group 1 (n = 9) underwent whole body hyperthermia (rectal temperature, 39.5 degrees C) 30 minutes postinjury for 4 hours, Group 2 (n = 8) underwent normothermia (rectal temperature, 37 degrees C) 30 minutes postinjury for 4 hours, and Group 3 (n = 10) underwent traumatic SCI with no postinjury thermal treatment. Twice-weekly assessments of locomotor function were made during a 6-week survival period using the Basso-Beattie-Breshnahan locomotor rating scale. Forty-four days after injury, animals were perfused, and their spinal cords serially sectioned. Sections were stained with hematoxylin, eosin, and Luxol fast blue for histopathological analysis. The percentage of tissue damage was quantitatively determined by using computer-aided image analysis. RESULTS: The results showed that 4 hours of postinjury hyperthermia significantly worsened locomotor outcome (final Basso-Beattie-Breshnahan scores were 9.7 +/- 0.3 [Group 1] versus 10.8 +/- 0.4 [Group 2] versus 11.3 +/- 0.3 [Group 3]) and led to an increase in the percentage of tissue damage (32.9 + 3.2% [Group 1] versus 22.3 +/- 2.8% [Group 3]). CONCLUSION: These data suggest that complications of SCI (e.g., fever, infection) leading to an elevation of systemic temperature may add to the severity of secondary injury associated with traumatic SCI and significantly affect neurological outcome.     

Sildenafil improves epicenter vascular perfusion but not hindlimb functional recovery after contusive spinal cord injury in mice

Nitric oxide (NO) is an important regulator of vasodilation and angiogenesis in the central nervous system (CNS). Signaling initiated by the membrane receptor CD47 antagonizes vasodilation and angiogenesis by inhibiting synthesis of cyclic guanosine monophosphate (cGMP). We recently found that deletion of CD47 led to significant functional locomotor improvements, enhanced angiogenesis, and increased epicenter microvascular perfusion in mice after moderate contusive spinal cord injury (SCI). We tested the hypothesis that improving NO/cGMP signaling within the spinal cord immediately after injury would increase microvascular perfusion, angiogenesis, and functional recovery, with an acute, 7-day administration of the cGMP phosphodiesterase 5 (PDE5) inhibitor sildenafil. PDE5 expression is localized within spinal cord microvascular endothelial cells and smooth muscle cells. While PDE5 antagonism has been shown to increase angiogenesis in a rat embolic stroke model, sildenafil had no significant effect on angiogenesis at 7 days post-injury after murine contusive SCI. Sildenafil treatment increased cGMP concentrations within the spinal cord and improved epicenter microvascular perfusion. Basso Mouse Scale (BMS) and Treadscan analyses revealed that sildenafil treatment had no functional consequence on hindlimb locomotor recovery. These data support the hypothesis that acutely improving microvascular perfusion within the injury epicenter by itself is an insufficient strategy for improving functional deficits following contusive SCI.     

Correlation between spinal cord blood flow and arterial diameter following acute spinal cord injury in rats

Summary Simultaneous measurements of spinal cord blood flow and arterial diameter at areas adjacent to a site of spinal cord injury were carried out to determine changes in CO₂ reactivity and autoregulation. The spinal cord injury was made at T10 level by the epidural clip compression method. A spinal window was drilled at an area either 7 mm caudal or 7 mm rostral to the injury site for the measurement of spinal cord blood flow and arterial diameter at the same time. Spinal cord blood flow was decreased at both spinal windows, especially at the rostral window. Arterial diameter was also decreased significantly at both sites. The ischaemic zone evaluated histologically tended to expand more diffusely in the rostral direction than in the caudal direction.In the pre-injury stage, both CO₂ reactivity and autoregulation were present in the spinal cord. Following the clip injury, CO₂ reactivity and autoregulation were both impaired in the areas 7 mm adjacent to the impact site. Correlation coefficients suggested that the rostral spinal cord tended to sustain more injury than the caudal spinal cord.The histologically proven spinal cord ischaemia following the injury may have resulted from the decreased arterial diameter and impaired CO₂ reactivity and dysautoregulation of the spinal cord.     

Calpain inhibitors prevent neuronal cell death and ameliorate motor disturbances after compression-induced spinal cord injury in rats

Traumatic spinal cord injury (SCI) results in widespread neuronal cell death. Recent studies have suggested that activated calpain mediates neuronal cell death in the central nervous system. We conducted a study to determine whether calpain mediates neuronal cell death in the motor neurons of the spinal cord after SCI, and whether postinjury administration of the calpain inhibitors N-acetyl- Leu-Leu-Met-CHO (ALLM) and calpain inhibitor III (CI III) (MDL28170) reduces the motor disturbances in rats with a model of SCI. Adult male Wistar rats were subjected to SCI by application of a 20-g weight impactor probe to the spinal cord at T12 for 20 min. The rats were divided into three groups according to whether they were injected intravenously with 0.05-2.5 mg/kg ALLM, 10 mg/kg CI III, or 0.1% DMSO as a control every 24 h for 1 week after SCI. Calpain was activated in the spinal cord at 8 h, 24 h, and 5 days after SCI, and administration of ALLM inhibited its activation. ALLM, as compared to the DMSO vehicle alone, also significantly reduced the number of motor neurons in spinal-cord lesions that were positively labeled at 24 h after SCI with the terminal deoxynucleotidyl transferase-uridine nucleotide end-labeling (TUNEL) technique. Additionally, both the inclined plane test and footprint analysis showed markedly better motor activity after 4 weeks in rats injected with ALLM or CI III than in rats given vehicle only. These results suggest that activation of calpain plays a critical role in the neuronal cell death that follows SCI, and that calpain inhibitors may have benefit in treating the motor disturbances that follow SCI.     

Augmented locomotor recovery after spinal cord injury in the athymic nude rat

The immune response contributes to ongoing secondary tissue destruction following spinal cord injury (SCI). Although infiltrating neutrophils and monocytes have been well studied in this process, T-cells have received less attention. The objective of this study was to assess locomotor recovery and tissue morphology after SCI in athymic (nude) rats, in which T-cell numbers are reduced. Results in athymic rats were compared with heterozygote littermates with normal T-cell profiles and with Sprague-Dawley rats from previous studies in our lab. Following transection of rat spinal cords at T10, we assessed the animals' locomotor recovery on a weekly basis for up to 11 weeks, using the Basso-Beattie-Bresnahan locomotor rating scale. Nude rats showed better locomotor recovery than did heterozygote or Sprague-Dawley rats, achieving scores of 5.6 +/- 0.8 versus 1.0 +/- 0.0, respectively (p = 0.002), at 4 weeks postinjury. The improved recovery of nude rats persisted for the 11-week postinjury assessment period, and was consistent with improved spinal reflexes rather than with recovery of descending motor pathways. Anatomical evaluation at 11 weeks indicated no difference in nude versus heterozygote rats in the size or distribution of cavities caudal to the transection site, but secondary damage was more severe rostral to the transection site in heterozygote rats. In neither group did cavities extend beyond 4 mm caudal to the transection site, and were therefore not directly responsible for the functional differences between the two groups. Cellular expression of the microglia/macrophage antigen ectodysplasin A (ED1) was reduced in nude rats as compared to heterozygotes, but no difference was observed in expression levels of 5-hydroxytryptamine, the 200-kDa neurofilament, or glial fibrillary acidic protein. The findings of the study show that a reduction in T-cell numbers significantly improves locomotor recovery after spinal cord transection, indicating a deleterious role for these immune cells in neural repair after trauma.     

Increased protein oxidation and decreased creatine kinase BB expression and activity after spinal cord contusion injury

Traumatic injury to the spinal cord triggers several secondary effects, including oxidative stress and compromised energy metabolism, which play a major role in biochemical and pathological changes in spinal cord tissue. Free radical generation and lipid peroxidation have been shown to be early events subsequent to spinal cord injury. In the present study, we demonstrated that protein oxidation increases in rat spinal cord tissue after experimental injury. As early as h after injury, the level of protein carbonyls at the injury epicenter was significantly higher than in control (169%, p < 0.05) and increased gradually over the next 4 weeks to 1260% of control level. Both caudal and rostral parts of the injured spinal cord demonstrated a mild increase of protein carbonyls by 4 weeks postinjury (135-138%, p < 0.05). Immunocytochemical analysis of protein carbonyls in the spinal cord cross-sections showed increased protein carbonyl immunoreactivity in the epicenter section compared to rostral and caudal sections of the same animal or control laminectomy animals. Increased protein carbonyl formation in damaged spinal cord tissue was associated with changes in activity and expression of an oxidative sensitive enzyme, creatine kinase BB, which plays an important role in the maintenance of ATP level in the CNS tissue. Damage to CK function in the CNS may severely aggravate the impairment of energy metabolism. The results of our study indicate that events associated with oxidative damage are triggered immediately after spinal cord trauma but continue to occur over the subsequent 4 weeks. These results suggest that antioxidant therapeutic strategies may be beneficial to lessen the consequences of the injury and potentially improve the restoration of neurological function.     

The role of directly applied hypothermia in spinal cord injury

STUDY DESIGN: The effect of intense local hypothermia was evaluated in a precision model of spinal canal narrowing and spinal cord injury in rats. The spinal cord injury was cooled with a custom cooling well used over the epidural surface. Basso, Beattie, and Bresnahan (BBB) motor scores and transcranial magnetic motor-evoked potential (tcMMEP) responses were used after injury to accurately evaluate neurologic recovery. OBJECTIVE: This study was undertaken to determine whether the prognosis for neurologic recovery in a standardized rat spinal cord injury model is altered by the direct application of precisely controlled hypothermia to the area of injury. SUMMARY OF BACKGROUND DATA: The role of hypothermia in the treatment of spinal cord injuries with neurologic deficits remains undefined. Hypothermia may decrease an area of spinal cord injury and limit secondary damage, therefore improving neurologic recovery. However, it has been difficult to consistently apply localized cooling to an area of spinal cord injury, and the use of systemic hypothermia is fraught with complications. This fact, along with the unavailability of a precise spinal cord injury model, has resulted in inconsistent results, both clinically and in the laboratory. In a rat model of spinal cord injury, 37 C and 19 C temperatures were used to study the role of hypothermia on neurologic recovery. METHODS: Male Spraque-Dawley rats (n = 52; weight, 277.7 g) were anesthetized with pentobarbital and subjected to laminectomy at T10. The rats were divided into three groups: 1) placement of a 50% spacer in the epidural space (16 rats), 2) severe (25 g/cm) spinal cord injury (16 rats), 3) 50% spacer in combination with spinal cord injury (16 rats). Eight rats in each group were tested at two temperatures: normothermic (37 C) and hypothermic (19 C). With the use of a specially designed hypothermic pool placed directly over the spinal cord for 2 hours, epidural heating to 37 C, and epidural cooling to 19 C was accomplished. Simultaneous measurements of spinal cord and body temperatures were performed. The rats underwent behavior testing using the BBB motor scores and serial tcMMEPs for 5 weeks. Statistical methods consisted of Student's t tests, one-way analysis of variance, Tukey post hoc t tests and chi2 tests. RESULTS: There was a significant improvement in motor scores in rats subjected to hypothermia compared with those that were normothermic after insertion of a 50% spacer. This improvement was observed during the 5-week duration of follow-up. In the severe spinal cord injury group and the spinal cord injury-spacer groups, no significant improvement in motor scores were obtained when the spinal cord was exposed to hypothermia. CONCLUSION: The results demonstrate that there is a statistically significant (P < 0.05) improvement in neurologic function in rats subjected to hypothermia (19 C) after insertion of a spacer that induced an ischemic spinal cord injury. This indicates that directly applied hypothermia may be beneficial in preventing injury secondary to ischemic cellular damage. The data demonstrated minimal therapeutic benefit of hypothermia (19 C) after a severe spinal cord injury.