Long-term assessment of hind limb motor function and neuronal injury following spinal cord ischemia in rats

Myelotomy promotes locomotor recovery in rats subjected to spinal cord injury: A meta-analysis of six randomized controlled trials

OBJECTIVE:

To investigate the effects of myelotomy on locomotor recovery in rats subjected to spinal cord injury.

DATA SOURCES:

Electronic databases including PubMed, Science Citation Index, Cochrane Library, China National Knowledge Infrastructure, Chinese Journals Full-text Database, China Biology Medicine disc, and Wanfang Database were searched to retrieve related studies published before September 2017. The MeSH terms (the Medical Subject Headings) such as “myelotomy”, “spinal cord injuries”, “rats”, “randomized controlled trial” and all related entry terms were searched.

DATA SELECTION:

Randomized controlled trials using myelotomy for the treatment of acute spinal cord injury in rats were included. Basso, Beattie, and Bresnahan scores were adopted as the evaluation method. RevMan Software (version 5.3) was used for data processing. The χ² and I² tests were used to assess heterogeneity. Using a random-effects model, a subgroup analysis was conducted to analyze the source of the heterogeneity.

OUTCOME MEASURES:

Basso, Beattie, and Bresnahan scores were observed 1–6 weeks after spinal cord injury.

RESULTS:

Six animal trials were included, using a total of 143 lab rats. The included trials were divided into two subgroups by injury degrees (moderate or severe). The pooled results showed that, 1–6 weeks after spinal cord injury, the overall Basso, Beattie, and Bresnahan score was significantly higher in the myelotomy group than in the contusion group (weighted mean difference (WMD) = 0.60; 95% confidence interval (CI): 0.23–0.97; P = 0.001; WMD = 2.10; 95% CI: 1.56–2.64; P < 0.001; WMD = 2.65; 95% CI: 1.73–3.57; P < 0.001; WMD = 1.66; 95% CI: 0.80–2.52; P < 0.001; WMD = 2.09; 95% CI: 0.92–3.26, P < 0.001; WMD = 2.25; 95% CI: 1.06–3.44, P < 0.001). The overall heterogeneity was high (I² = 85%; I² = 95%; I² = 94%; I² = 88%; I² = 91%; I² = 89%). The results in the moderate injury subgroup showed that Basso, Beattie, and Bresnahan scores were significantly higher in the myelotomy group than in the contusion group (WMD = 0.91, 95% CI: 0.52–1.3, P < 0.001; WMD = 2.10; 95% CI: 1.56–2.64, P < 0.001; WMD = 2.65; 95% CI: 1.73–3.57, P < 0.001; WMD = 2.50, 95% CI: 1.72–3.28, P < 0.001; WMD = 3.29, 95% CI: 2.21–4.38, P < 0.001; WMD = 3.27; 95% CI: 2.31–4.23, P < 0.001). The relevant heterogeneity was low. However, there were no significant differences in Basso, Beattie, and Bresnahan scores between the myelotomy and contusion groups in the severe injury subgroup at 2 and 3 weeks after the injury (P = 0.75; P = 0.92).

CONCLUSION:

To date, this is the first attempt to summarize the potential effect of myelotomy on locomotor recovery in rats with spinal cord injury. Our findings conclude that myelotomy promotes locomotor recovery in rats with spinal cord injury, especially in those with moderate injury.

Effects of curcumin on acute spinal cord ischemia-reperfusion injury in rabbits

Object

The object of this study was to conduct a prospective, randomized, laboratory investigation of the neuroprotective effects of curcumin functionally, biochemically, and histologically in an experimental acute spinal cord ischemia-reperfusion injury on rabbits.

Methods

Eighteen rabbits were randomly assigned to 1 of 3 groups: the sham group, the ischemia-reperfusion group, or the curcumin group. Spinal cord ischemia was induced by applying an infrarenal aortic cross-clamp for 30 minutes. At 48 hours after ischemia, neurological function was evaluated with modified Tarlov criteria. Biochemical changes in the spinal cord and plasma were observed by measuring levels of malondialdehyde (MDA), advanced oxidation protein products (AOPP), glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), nitrite/nitrate, and tumor necrosis factor-α (TNF-α). Histological changes were examined with H & E staining. Immunohistochemical staining with antibodies against caspase-3 was performed to evaluate cell apoptosis after ischemia.

Results

In the curcumin group, neurological outcome scores were statistically significantly better compared with the ischemia-reperfusion group. In the ischemia-reperfusion group, MDA, AOPP, and nitrite/nitrate levels were significantly elevated in the spinal cord tissue and the plasma by the induction of ischemia-reperfusion. The curcumin treatment significantly prevented the ischemia-reperfusion–induced elevation of nitrite/nitrate and TNF-α. In addition, the spinal cord tissue and the plasma SOD, GSH, and CAT levels were found to be preserved in the curcumin group and not statistically different from those of the sham group. Histological evaluation of the tissues also demonstrated a decrease in axonal damage, neuronal degeneration, and glial cell infiltration after curcumin administration.

Conclusions

Although further studies including different dose regimens and time intervals are required, curcumin could attenuate a spinal cord ischemia-reperfusion injury in rabbits via reducing oxidative products and proinflammatory cytokines, as well as increasing activities of antioxidant enzymes and preventing apoptotic cell death.

Erythropoietin attenuates the sequels of ischaemic spinal cord injury with enhanced recruitment of CD34+ cells in mice

Erythropoietin has been shown to promote tissue regeneration after ischaemic injury in various organs. Here, we investigated whether Erythropoietin could ameliorate ischaemic spinal cord injury in the mouse and sought an underlying mechanism. Spinal cord ischaemia was developed by cross-clamping the descending thoracic aorta for 7 or 9 min. in mice. Erythropoietin (5000 IU/kg) or saline was administrated 30 min. before aortic cross-clamping. Neurological function was assessed using the paralysis score for 7 days after the operation. Spinal cords were histologically evaluated 2 and 7 days after the operation. Immunohistochemistry was used to detect CD34(+) cells and the expression of brain-derived neurotrophic factor and vascular endothelial growth factor. Each mouse exhibited either mildly impaired function or complete paralysis at day 2. Erythropoietin-treated mice with complete paralysis demonstrated significant improvement of neurological function between day 2 and 7, compared to saline-treated mice with complete paralysis. Motor neurons in erythropoietin-treated mice were more preserved at day 7 than those in saline-treated mice with complete paralysis. CD34(+) cells in the lumbar spinal cord of erythropoietin-treated mice were more abundant at day 2 than those of saline-treated mice. Brain-derived neurotrophic factor and vascular endothelial growth factor were markedly expressed in lumbar spinal cords in erythropoietin-treated mice at day 7. Erythropoietin demonstrated neuroprotective effects in the ischaemic spinal cord, improving neurological function and attenuating motor neuron loss. These effects may have been mediated by recruited CD34(+) cells, and enhanced expression of brain-derived neurotrophic factor and vascular endothelial growth factor.

Molecular Mechanisms Underlying Cell Death in Spinal Networks in Relation to Locomotor Activity After Acute Injury in vitro

Understanding the pathophysiological changes triggered by an acute spinal cord injury is a primary goal to prevent and treat chronic disability with a mechanism-based approach. After the primary phase of rapid cell death at the injury site, secondary damage occurs via autodestruction of unscathed tissue through complex cell-death mechanisms that comprise caspase-dependent and caspase-independent pathways. To devise novel neuroprotective strategies to restore locomotion, it is, therefore, necessary to focus on the death mechanisms of neurons and glia within spinal locomotor networks. To this end, the availability of in vitro preparations of the rodent spinal cord capable of expressing locomotor-like oscillatory patterns recorded electrophysiologically from motoneuron pools offers the novel opportunity to correlate locomotor network function with molecular and histological changes long after an acute experimental lesion. Distinct forms of damage to the in vitro spinal cord, namely excitotoxic stimulation or severe metabolic perturbation (with oxidative stress, hypoxia/aglycemia), can be applied with differential outcome in terms of cell types and functional loss. In either case, cell death is a delayed phenomenon developing over several hours. Neurons are more vulnerable to excitotoxicity and more resistant to metabolic perturbation, while the opposite holds true for glia. Neurons mainly die because of hyperactivation of poly(ADP-ribose) polymerase-1 (PARP-1) with subsequent DNA damage and mitochondrial energy collapse. Conversely, glial cells die predominantly by apoptosis. It is likely that early neuroprotection against acute spinal injury may require tailor-made drugs targeted to specific cell-death processes of certain cell types within the locomotor circuitry. Furthermore, comparison of network size and function before and after graded injury provides an estimate of the minimal network membership to express the locomotor program.

Reduction of spinal cord ischemia/reperfusion injury with simvastatin in rats

BACKGROUND

Surgery of the thoracic or thoracoabdominal aorta may cause spinal cord ischemia and subsequent paraplegia. However, conventional strategies for preventing paraplegia due to spinal cord ischemia provide insufficient protection and cause additional side effects. We hypothesized that simvastatin, a drug recently shown to be neuroprotective against brain ischemia/reperfusion, would be neuroprotective in a rat spinal cord ischemia/reperfusion model.

METHODS

Rats were randomly assigned to simvastatin, vehicle, or sham-surgery (sham) groups (n = 6 per group). Simvastatin (10 mg/kg) or vehicle was administered subcutaneously once daily for 7 days before aortic balloon occlusion, and once at 24 hours after reperfusion. Spinal cord ischemia was induced by balloon inflation of a 2F Fogarty catheter in the thoracic aorta, and the proximal mean arterial blood pressure was maintained at 40 mm Hg for 12 minutes. The sham group received the same operation without inflation of the balloon. Ischemic injury was assessed by hindlimb motor function using the Motor Deficit Index score at 6 to 48 hours after ischemic reperfusion, and histological assessment of the spinal cord was performed 48 hours after reperfusion.

RESULTS

The Motor Deficit Index scores at 24 and 48 hours after reperfusion were significantly improved in the simvastatin group compared with the vehicle group (P = 0.021 and P = 0.023, respectively). Furthermore, there were significantly more normal motor neurons in the simvastatin group than in the vehicle group (P = 0.037). The percentage area of white matter vacuolation was significantly smaller in the simvastatin group than in the vehicle group (P = 0.030).

CONCLUSIONS

Simvastatin treatment can attenuate hindlimb motor dysfunction and histopathological changes in spinal cord ischemia/reperfusion injury in rats.

Therapeutic Benefit of Intrathecal Injection of Marrow Stromal Cells on Ischemia-Injured Spinal Cord

BACKGROUND

Prophylactic transplantation of marrow stromal cells (MSCs) before spinal cord ischemia has been shown to attenuate neurologic injures. We sought to investigate the therapeutic effect of MSCs on ischemia-injured spinal cord.

METHODS

Marrow stromal cells were expanded in vitro and prelabeled with bromodeoxyuridine. Spinal cord ischemia was induced in rabbits by infrarenal aortic occlusion for 30 minutes. Four groups were enrolled. About 1 x 10(8) MSCs were intrathecally injected 2 hours (group MSC-2h), 24 hours (group MSC-24h), or 48 hours (group MSC-48h) after spinal cord ischemia, respectively. The control group received intrathecal injection of medium alone. Hind-limb motor function was assessed during a 28-day recovery period with Tarlov criteria, and then histologic examination was performed.

RESULTS

Marrow stromal cells still could be found in the spinal cord 4 weeks after transplantation. The capillary density in the ventral gray matter was significantly increased in the three MSC-treated groups (p < 0.01 versus control group, respectively). After a 28-day recovery, marked functional improvement was detected in group MSC-2h (from day 1 to 28, p < 0.05, versus control group, respectively) and group MSC-24h (from day 14 to 28, p < 0.05, versus control group, respectively), but not in group MSC-48h. The number of intact motor neurons was much greater in group MSC-2h (p < 0.05, versus control group).

CONCLUSIONS

Intrathecal injection of MSCs enhances angiogenesis in the host spinal cord and improves the motor functional recovery after spinal cord ischemia. The therapeutic time window is critical for the therapeutic effect of MSCs.

Optimization of a mouse locomotor rating system to evaluate compression-induced spinal cord injury: correlation of locomotor and morphological injury indices

Object

Due to the usefulness of mouse genetics, there is a need to improve procedures for producing and assessing spinal cord injury (SCI) in mice. The authors describe an improved locomotor scoring system for evaluating SCI. The modified Basso-Beattie-Bresnahan (mBBB) scoring system for mice is compared with existing procedures as well as histological SCI criteria.

Methods

Mice were subjected to SCI by placing a weight on the cord at T-12 for 5 to 15 minutes after laminectomy to produce spinal cord ischemia. Injury was assessed using mBBB scoring that incorporates elements of the rat BBB and the mouse motor function scoring systems that are best suited for precisely assessing mouse SCI. The mBBB score was found to be more discriminating than the inclined plane test, and in the authors’ laboratory it had a significantly lower coefficient of variation than the Basso mouse scale score. The mBBB score is well correlated with sparing of white matter as assessed by eriochrome cyanine staining of myelin.

Conclusions

Weight placement at T-12 in the mouse causes reproducible SCI. A new mBBB scoring system is useful for accurately assessing locomotor dysfunction following SCI in mice and is well correlated with histological assessment of spinal cord white matter.

An Evaluation of White Matter Injury After Spinal Cord Ischemia in Rats: A Comparison with Gray Matter Injury

We quantitatively assessed both gray and white matter injury after spinal cord ischemia in rats, and the relationship between the magnitude of gray and white matter injury was determined. Twenty-five male rats were anesthetized with isoflurane, and spinal cord ischemia (SCI) was induced by balloon intraaortic occlusion combined with hypotension. The animals were randomly allocated to one of the following three groups: animals with SCI for 12 min (SCI-12; n = 8), 15 min (SCI-15; n = 9), or those with sham operation (n = 8). Twenty-four hours after reperfusion, hindlimb motor function was assessed using the Basso-Beattie-Bresnahan scale scoring. Gray matter damage was assessed on the basis of the number of normal neurons in the ventral horn. White matter damage was assessed on the basis of the extent of vacuolation and amyloid precursor protein immunoreactivity in the ventral and ventrolateral white matter. There were significantly less normal neurons in the SCI-15 group compared with those in the SCI-12 and sham groups (P < 0.05). There was a significant positive correlation between the Basso-Beattie-Bresnahan scores and the number of normal neurons. The percentages of vacuolation areas in the SCI-15 group were significantly larger compared with those in the SCI-12 and sham groups (30% +/- 10% versus 9% +/- 7%, 0% +/- 0%, P < 0.05). Immunohistochemical analysis revealed increased amyloid precursor protein immunoreactivity in the swollen axons, especially in the SCI-15 group. There was a significant negative correlation between the number of normal neurons and percentages of vacuolation areas. These results indicate that both gray and white matter were injured after SCI in rats and the degree of white mater injury was correlated with the severity of gray matter injury after a relatively short recovery period.

The effects of the delta-opioid agonist SNC80 on hind-limb motor function and neuronal injury after spinal cord ischemia in rats

Recent investigation suggested neuroprotective efficacy of a delta-opioid agonist in the brain. We investigated the effects of intrathecal treatment with a delta-opioid agonist (SNC80) on spinal cord ischemia (SCI) in rats. SCI was induced with an intraaortic balloon catheter. The animals were randomly allocated to one of the following five groups: 1) SNC80 before 9 min of SCI (SNC-9; n = 12), 2) vehicle before 9 min of SCI (V-9; n = 12), 3) SNC80 before 11 min of SCI (SNC-11; n = 10), 4) vehicle before 11 min of SCI (V-11; n = 12), or 5) sham (n = 12). SNC80 (400 nmol) or vehicle was administered 15 min before SCI. Forty-eight hours after reperfusion, hind-limb motor function was assessed by using the Basso, Beattie, Bresnahan (BBB) scale (0 = paraplegia; 21 = normal) and histological assessment of the L4 and L5 spinal segments was performed. BBB scores in the SNC-9 group were higher compared with those in the V-9 group (P < 0.05), whereas there were no differences in BBB scores between the SNC-11 and V-11 groups. There were significantly more normal neurons in the SNC-9 and SNC-11 groups than in the V-9 and V-11 groups (P < 0.05). The results indicate that intrathecal treatment with the delta-opioid agonist SNC80 can attenuate hind-limb motor dysfunction and neuronal injury after SCI in rats.

Experimental spinal cord ischemia: Model characterization and improved outcome with arterial hypertension*

OBJECTIVE

Paraplegia from spinal cord ischemia is a devastating complication of thoracoabdominal aortic aneurysm repair. Perioperative hypoperfusion of the spinal cord is a critical determinant of residual neurologic deficits. We determined if functional and histologic outcome is dependent on systemic blood pressure in a rat model of spinal cord ischemia.

DESIGN

Randomized, controlled, prospective study.

SETTING

Research laboratory at a university teaching hospital.

SUBJECTS

Adult male Wistar rats.

INTERVENTIONS

Endotracheally intubated adult male Wistar rats (300-450 g) anesthetized with halothane underwent a thoracotomy and placement of a clip across the descending aorta for 27 mins. Mean proximal arterial blood pressure (MPABP) was monitored with a cannula placed in the left common carotid artery. Halothane was adjusted (1.25-1.5%) to maintain MPABP between 70 and 90 mm Hg (n = 20) or 140 and 150 mm Hg (n = 20). Shamoperated rats (n = 10) had a thoracotomy without aortic clamping at an MPABP of 70-90 mm Hg. Following 1, 24, 48, and 72 hrs of recovery from anesthesia, motor function of the hind paws was scored as follows: 0, no evidence of deficit; 1, toes flat under body when walking but with ataxia; 2, knuckle walks; 3, movements in hind limbs but unable to knuckle walk; 4, no movement, drags hind limbs. Body temperature was maintained between 37 and 38 degrees C throughout the experiment.

MEASUREMENTS AND MAIN RESULTS

All sham operated rats with MPABP 70-90 mm Hg recovered without neurologic deficits, whereas those that underwent aortic occlusion with MPABP between 70 and 90 mm Hg emerged from anesthesia with grade 3 and 4 deficits and remained in this condition without improvement at 72 hrs. Histopathology at 72 hrs demonstrated moderate to severe neuronal loss with involvement of dorsal, intermediate, and ventral horns. Only eight of 20 rats that underwent aortic occlusion with MPABP between 140 and 150 mm Hg had grade 1 and 2 deficits on emergence but had no neurologic deficit after 1 hr. Most of the surviving neurons in these animals appeared normal histologically, particularly motor neurons around the periphery of the ventral horn.

CONCLUSIONS

Systemic blood pressure is a critical determinant of outcome following spinal cord ischemia, and controlled peri-operative blood pressure augmentation may ameliorate neurologic deficits in patients who undergo thoracoabdominal vascular procedures and are at risk for spinal cord hypoperfusion.