Methods for behavioral testing of spinal cord injured rats

Custom-engineered hydrogels for delivery of human iPSC-derived neurons into the injured cervical spinal cord

Cervical damage is the most prevalent type of spinal cord injury clinically, although few preclinical research studies focus on this anatomical region of injury. Here we present a combinatorial therapy composed of a custom-engineered, injectable hydrogel and human induced pluripotent stem cell (iPSC)-derived deep cortical neurons. The biomimetic hydrogel has a modular design that includes a protein-engineered component to allow customization of the cell-adhesive peptide sequence and a synthetic polymer component to allow customization of the gel mechanical properties. In vitro studies with encapsulated iPSC-neurons were used to select a bespoke hydrogel formulation that maintains cell viability and promotes neurite extension. Following injection into the injured cervical spinal cord in a rat contusion model, the hydrogel biodegraded over six weeks without causing any adverse reaction. Compared to cell delivery using saline, the hydrogel significantly improved the reproducibility of cell transplantation and integration into the host tissue. Across three metrics of animal behavior, this combinatorial therapy significantly improved sensorimotor function by six weeks post transplantation. Taken together, these findings demonstrate that design of a combinatorial therapy that includes a gel customized for a specific fate-restricted cell type can induce regeneration in the injured cervical spinal cord.

Coordination function index: A novel indicator for assessing hindlimb locomotor recovery in spinal cord injury rats based on catwalk gait parameters

In preclinical studies of spinal cord injury (SCI), behavioral assessments are crucial for evaluating treatment effectiveness. Commonly used methods include Basso, Beattie, Bresnahan (BBB) score and the Louisville swim scale (LSS), relying on subjective observations. The CatWalk automated gait analysis system is also widely used in SCI studies, providing extensive gait parameters from footprints. However, these parameters are often used independently or combined simply without utilizing the vast amount of data provided by CatWalk. Therefore, it is necessary to develop a novel approach encompassing multiple CatWalk parameters for a comprehensive and objective assessment of locomotor function. In this work, we screened 208 CatWalk XT gait parameters and identified 38 suitable for assessing hindlimb motor function recovery in a rat thoracic contusion SCI model. Exploratory factor analysis was used to reveal structural relationships among these parameters. Weighted scores for Coordination effectively differentiated hindlimb motor function levels, termed as the Coordinated Function Index (CFI). CFI showed high reliability, exhibiting high correlations with BBB scores, LSS, and T2WI lesion area. Finally, we simplified CFI based on factor loadings and correlation analysis, obtaining a streamlined version with reliable assessment efficacy. In conclusion, we developed a systematic assessment indicator utilizing multiple CatWalk parameters to objectively evaluate hindlimb motor function recovery in rats after thoracic contusion SCI.

Krishnan L, Abelson KSP. Refinement of the motorised laminectomy-assisted rat spinal cord injury model by analgesic treatment

Usage and reporting of analgesia in animal models of spinal cord injury (SCI) have been sparse and requires proper attention. The majority of experimental SCI research uses rats as an animal model. This study aimed to probe into the effects of some commonly used regimens with NSAIDs and opioids on well-being of the rats as well as on the functional outcome of the model. This eight-week study used forty-two female Wistar rats (Crl: WI), randomly and equally divided into 6 treatment groups, viz. I) tramadol (5mg/kg) and buprenorphine (0.05mg/kg); II) carprofen (5mg/kg) and buprenorphine (0.05mg/kg); III) carprofen (5mg/kg); IV) meloxicam (1mg/kg) and buprenorphine (0.05mg/kg); V) meloxicam (1mg/kg); and VI) no analgesia (0.5 ml sterile saline). Buprenorphine was administered twice daily whereas other treatments were given once daily for five days post-operatively. Injections were given subcutaneously. All animals underwent dental burr-assisted laminectomy at the T10-T11 vertebra level. A custom-built calibrated spring-loaded 200 kilodynes force deliverer was used to induce severe SCI. Weekly body weight scores, Rat Grimace Scale (RGS), and dark-phase home cage activity were used as markers for well-being. Weekly Basso Beattie and Bresnahan (BBB) scores served as markers for functionality together with Novel Object Recognition test (NOR) at week 8 and terminal histopathology using area of vacuolisation and live neuronal count from the ventral horns of spinal cord. It was concluded that the usage of analgesia improved animal wellbeing while having no effects on the functional aspects of the animal model in comparison to the animals that received no analgesics.

Methods for evaluating gait associated dynamic balance and coordination in rodents

Balance is the dynamic and unconscious control of the body's centre of mass to maintain postural equilibrium. Regulated by the vestibular system, head movement and acceleration are processed by the brain to adjust joints. Several conditions result in a loss of balance, including Alzheimer's Disease, Parkinson's Disease, Menière's Disease and cervical spondylosis, all of which are caused by damage to certain parts of the vestibular pathways. Studies about the impairment of the vestibular system are challenging to carry out in human trials due to smaller study sizes limiting applications of the results and a lacking understanding of the human balance control mechanism. In contrast, more controlled research can be performed in animal studies which have fewer confounding factors than human models and allow specific conditions that affect balance to be replicated. Balance control can be studied using rodent balance-related behavioural tests after spinal or brain lesions, such as the Basso, Beattie and Bresnahan (BBB) Locomotor Scale, Foot Fault Scoring System, Ledged Beam Test, Beam Walking Test, and Ladder Beam Test, which are discussed in this review article along with their advantages and disadvantages. These tests can be performed in preclinical rodent models of femoral nerve injury, stroke, spinal cord injury and neurodegenerative diseases.

Evaluation of the effect of intrathecal GM1 in 24, 48, and 72 hours after acute spinal cord injury in rats

OBJECTIVE

The aim of this study was to evaluate the best timing and feasibility of intrathecal application of sodium monosialoganglioside (GM1) after spinal cord contusion in Wistar rats as an experimental model.

METHODS

Forty Wistar rats were submitted to contusion spinal cord injury after laminectomy. The animals were randomized and divided into four groups: Group 1 - Intrathecal application of GM1 24 hours after contusion; Group 2 - Intrathecal application of GM1 48 hours after contusion; Group 3 - intrathecal application of GM1 72 hours after contusion; Group 4 - Sham, with laminectomy and intrathecal application of 0.5 mL of 0.9% saline solution, without contusion. The recovery of locomotor function was evaluated at seven different moments by the Basso, Beattie, and Bresnahan (BBB) test. They were also assessed by the horizontal ladder, with sensory-motor behavioral assessment criteria, pre-and postoperatively.

RESULTS

This experimental study showed better functional scores in the group submitted to the application of GM1, with statistically significant results, showing a mean increase when evaluated on known motor tests like the horizontal ladder and BBB, at all times of evaluation (p < 0.05), especially in group 2 (48 hours after spinal cord injury). Also, fewer mistakes and slips over the horizontal ladder were observed, and many points were achieved at the BBB scale analysis.

CONCLUSION

The study demonstrated that the intrathecal application of GM1 after spinal cord contusion in Wistar rats is feasible. The application 48 hours after the injury presented the best functional results.

Intrathecal minocycline does not block the adverse effects of repeated, intravenous morphine administration on recovery of function after SCI

Opioids are among the most effective analgesics for the management of pain in the acute phase of a spinal cord injury (SCI), and approximately 80% of patients are treated with morphine in the first 24 h following SCI. We have found that morphine treatment in the first 7 days after SCI increases symptoms of pain at 42 days post-injury and undermines the recovery of locomotor function in a rodent model. Prior research has implicated microglia/macrophages in opioid-induced hyperalgesia and the development of neuropathic pain. We hypothesized that glial activation may also underlie the development of morphine-induced pain and cell death after SCI. Supporting this hypothesis, our previous studies found that intrathecal and intravenous morphine increase the number of activated microglia and macrophages present at the spinal lesion site, and that the adverse effects of intrathecal morphine can be blocked with intrathecal minocycline. Recognizing that the cellular expression of opioid receptors, and the intracellular signaling pathways engaged, can change with repeated administration of opioids, the current study tested whether minocycline was also protective with repeated intravenous morphine administration, more closely simulating clinical treatment. Using a rat model of SCI, we co-administered intravenous morphine and intrathecal minocycline for the first 7 days post injury and monitored sensory and locomotor recovery. Contrary to our hypothesis and previous findings with intrathecal morphine, we found that minocycline did not prevent the negative effects of morphine. Surprisingly, we also found that intrathecal minocycline alone is detrimental for locomotor recovery after SCI. Using ex vivo cell cultures, we investigated how minocycline and morphine altered microglia/macrophage function. Commensurate with published studies, we found that minocycline blocked the effects of morphine on the release of pro-inflammatory cytokines but, like morphine, it increased glial phagocytosis. While phagocytosis is critical for the removal of cellular and extracellular debris at the spinal injury site, increased phagocytosis after injury has been linked to the clearance of stressed but viable neurons and protracted inflammation. In sum, our data suggest that both morphine and minocycline alter the acute immune response, and reduce locomotor recovery after SCI.

Adverse Effects of Repeated, Intravenous Morphine on Recovery after Spinal Cord Injury in Young, Male Rats Are Blocked by a Kappa Opioid Receptor Antagonist

Immediately following spinal cord injury (SCI) patients experience pain associated with injury to the spinal cord and nerves as well as with accompanying peripheral injuries. This pain is usually treated with opioids, and most commonly with morphine. However, in a rodent model we have shown that, irrespective of the route of administration, morphine administered in the acute phase of SCI undermines long-term locomotor recovery. Our previous data suggest that activation of kappa opioid receptors (KORs) mediates these negative effects. Blocking KORs with norbinaltorphimine (norBNI), prior to a single dose of epidural morphine, prevented the morphine-induced attenuation of locomotor recovery. Because numerous cellular changes occur with chronic opioid administration compared with a single dose, the current study tested whether norBNI was also effective in a more clinically relevant paradigm of repeated, intravenous morphine administration after SCI. We hypothesized that blocking KOR activation during repeated, intravenous morphine administration would also protect recovery. Supporting this hypothesis, we found that blocking KOR activation in young, male rats prevented the negative effects of morphine on locomotor recovery, although neither norBNI nor morphine had an effect on long-term pain at the doses used. We also found that norBNI treatment blocked the adverse effects of morphine on lesion size. These data suggest that a KOR antagonist given in conjunction with morphine may provide a clinical strategy for effective analgesia without compromising locomotor recovery after SCI.

Inflammaging and bone loss in a rat model of spinal cord injury

Spinal cord injury (SCI) results in significant loss of sublesional bone, adding to the comorbidity of SCI with an increased risk of fracture and post-fracture complications. Unfortunately, the effect of SCI on skeletal health is also likely to rise as the average age of SCI has increased and there are well-known negative effects of age on bone. To date, however, the impact of age and age-associated inflammation (inflammaging) on skeletal health after SCI remains largely unknown. To address this, we compared bone parameters in young (3 month) and middle-aged (9 month) male and female rats with a moderate thoracic contusion injury, to age and sex matched sham-operated controls. Skeletal parameters, locomotor function and serum cytokine levels were assessed at both subchronic (30 days) and chronic (180 days) time points post injury. We hypothesized that SCI would lead to a dramatic loss of bone immediately after injury in all SCI-groups, with inflammaging leading to greater loss in middle-aged SCI rats. We also predicted that while younger rats may re-establish bone properties in more chronic phases of SCI, middle-aged rats would not. Supporting these hypothesis, trabecular bone volume was significantly lower in male and young female SCI rats early after injury. Contrary to our hypothesis, however, there was greater loss of trabecular bone volume, relative to age-matched shams, in young compared to middle-aged SCI rats with no effects of SCI on trabecular bone volume in middle-aged female rats. Moreover, despite recovery of weight-supported locomotor activity, bone loss persisted into the chronic phase of injury for the young rats. Bone formation rates were lower in young male SCI rats, regardless of the time since injury, while both young and middle-aged female SCI rats had lower bone formation in the subchronic but not chronic phase of SCI. In middle-aged rats, SCI-induced higher osteoclast surfaces, which also persisted into the chronic phase of SCI in middle-aged females. Neither age nor SCI-induced increases in inflammation seemed to be associated with bone loss. In fact, SCI had more dramatic and persistent effects on bone in male rats, while aging and SCI elevated serum cytokines only in female rats. Overall, this study demonstrates SCI-induced loss of bone and altered bone turnover in male and female rats that persists into the chronic phase post-injury. The sex and age dependent variations in bone turnover and serum cytokines, however, underscore the need to further explore both mechanisms and potential therapeutics in multiple demographics.

Morphine-induced changes in the function of microglia and macrophages after acute spinal cord injury

Background

Opioids are among the most effective and commonly prescribed analgesics for the treatment of acute pain after spinal cord injury (SCI). However, morphine administration in the early phase of SCI undermines locomotor recovery, increases cell death, and decreases overall health in a rodent contusion model. Based on our previous studies we hypothesize that morphine acts on classic opioid receptors to alter the immune response. Indeed, we found that a single dose of intrathecal morphine increases the expression of activated microglia and macrophages at the injury site. Whether similar effects of morphine would be seen with repeated intravenous administration, more closely simulating clinical treatment, is not known.

Methods

To address this, we used flow cytometry to examine changes in the temporal expression of microglia and macrophages after SCI and intravenous morphine. Next, we explored whether morphine changed the function of these cells through the engagement of cell-signaling pathways linked to neurotoxicity using Western blot analysis.

Results

Our flow cytometry studies showed that 3 consecutive days of morphine administration after an SCI significantly increased the number of microglia and macrophages around the lesion. Using Western blot analysis, we also found that repeated administration of morphine increases β-arrestin, ERK-1 and dynorphin (an endogenous kappa opioid receptor agonist) production by microglia and macrophages.

Conclusions

These results suggest that morphine administered immediately after an SCI changes the innate immune response by increasing the number of immune cells and altering neuropeptide synthesis by these cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12868-022-00739-3.

Effects of photobiomodulation in experimental spinal cord injury models: A systematic review

This systematic review investigated the repercussions of photobiomodulation using low-level laser therapy (LLLT) for the treatment of spinal cord injury (SCI) in experimental models. Studies were identified from relevant databases published between January 2009 and December 2021. Nineteen original articles were selected and 68.4% used light at an infrared wavelength. There was a considerable variation of the power used (from 25 to 200 mW), total application time (8-3000 s) and total energy (0.3-450 J). In 79% of the studies, irradiation was initiated immediately after or within 2 h of the SCI, and treatment time ranged continuously from 5 to 21 days. In conclusion, LLLT can be an auxiliary therapy in the treatment of SCI, playing a neuroprotective role, enabling functional recovery, increasing the concentration of nerve connections around the injury site and reducing pro-inflammatory cytokines. However, there is a need for standardization in the dosimetric parameters.

Correlation Analysis Between Magnetic Resonance Imaging-Based Anatomical Assessment and Behavioral Outcome in a Rat Contusion Model of Chronic Thoracic Spinal Cord Injury

Although plenty of evidences from preclinical studies have led to potential treatments for patients with spinal cord injury (SCI), the failure to translate promising preclinical findings into clinical advances has long puzzled researchers. Thus, a more reliable combination of anatomical assessment and behavioral testing is urgently needed to improve the translational worth of preclinical studies. To address this issue, the present study was designed to relate magnetic resonance imaging (MRI)-based anatomical assessment to behavioral outcome in a rat contusion model. Rats underwent contusion with three different heights to simulate various severities of SCI, and their locomotive functions were evaluated by the grid-walking test, Louisville swim scale (LSS), especially catwalk gait analysis system and basic testing, and Basso, Beattie, Bresnahan (BBB) score. The results showed that the lesion area (LA) is a better indicator for damage assessment compared with other parameters in sagittal T2-weighted MRI (T2WI). Although two samples are marked as outliers by the box plot analysis, LA correlated closely with all of the behavioral testing without ceiling effect and floor effect. Moreover, with a moderate severity of SCI in a contusion height of 25 mm, the smaller the LA of the spinal cord measured on sagittal T2WI the better the functional performance, the smaller the cavity region and glial scar, the more spared the myelin, the higher the volatility, and the thicker the bladder wall. We found that LA significantly related with behavior outcomes, which indicated that LA could be a proxy of damage assessment. The combination of sagittal T2WI and four types of behavioral testing can be used as a reliable scheme to evaluate the prognosis for preclinical studies of SCI.

Automated lever task with minimum antigravity movement for rats with cervical spinal cord injury

BACKGROUND

Although there is currently no cure for paralysis due to spinal cord injury (SCI), the highest treatment priority is restoring arm and hand function for people with cervical SCI. Preclinical animal models provide an opportunity to test innovative treatments, but severe cervical injury models require significant time and effort to assess responses to novel interventions. Moreover, there is no behavioral task that can assess forelimb movement in rats with severe cervical SCI unable to perform antigravity movements.

NEW METHOD

We developed a novel lever pressing task for rats with severe cervical SCI. We employed an automated adaptive algorithm to train animals using open-source software and commercially available hardware. We found that using the adaptive training required only 13.3 ± 2.5 training days to achieve behavioral proficiency. The lever press task could quantify immediate and long-term improvements in severely impaired forelimb function effectively. This behavior platform has potential to facilitate rehabilitative training and assess effects of therapeutic modalities following SCI.

COMPARISON WITH EXISTING METHODS

There is no existing assessment aiming to quantify forelimb extension movement in rodents without function against gravity. We found that the new lever press task in the antigravity position could assess the severity of cervical SCI as well as the compensatory movement in the proximal forelimb less affected by the injury.

CONCLUSIONS

This study demonstrates that the new behavioral task is capable of tracking the functional changes with various therapies in rats with severe forelimb impairments in a cost- and time-efficient manner.

Refinement of the spinal cord injury rat model and validation of its applicability as a model for memory loss and chronic pain

BACKGROUND

Laminectomy produces trauma in spinal cord injury (SCI) animal models resulting in impinging artefacts and welfare issues. Mechanizing laminectomy using a dental burr assisted (DBA) technique to reduce the impact of conventionally performed laminectomy on animal welfare without any alterations in the outcome of the model was previously demonstrated. However, further validation was necessary to establish it as an alternative in developing SCI rats as a model of chronic pain and memory loss.

NOVEL METHOD

DBA technique was employed to perform laminectomy at T10-T11 vertebrae in rats undergoing contusion SCI as a model of chronic pain and memory loss. In a 56-day study, 24 female Wistar rats (Crl: WI) were assigned randomly to four equal groups: conventionally laminectomised, DBA laminectomised, conventionally laminectomised with SCI and DBA laminectomised with SCI.

RESULTS

The study revealed DBA technique to cause less surgical bleeding (p = 0.001), lower Rat Grimace Scale (p = 0.0006); resulted in better body weight changes (p = 0.0002 on Day 7 and p = 0.0108 on Day 28) and dark phase activity (p = .0.0014 on Day 1; p = 0.0422 on Day 56). Different techniques did not differ in Basso Beattie Bresnahan score, novel object recognition, mechanical allodynia, number of surviving neurons and the area of vacuolation- indicating that the new method doesn't affect the validity of the model.

COMPARISON WITH EXISTING METHODS

In comparison with the conventional technique, motorised laminectomy can be a valid tool that evokes lesser pain and ensures higher well-being in rats modelled for chronic pain and memory loss.

CONCLUSIONS

The intended outcome from the model is not influenced by techniques whereas the DBA-technique is a refined alternative to the conventional method in achieving better welfare in SCI studies.

Zn-0.8Mg-0.2Sr (wt.%) Absorbable Screws-An In-Vivo Biocompatibility and Degradation Pilot Study on a Rabbit Model

In this pilot study, we investigated the biocompatibility and degradation rate of an extruded Zn-0.8Mg-0.2Sr (wt.%) alloy on a rabbit model. An alloy screw was implanted into one of the tibiae of New Zealand White rabbits. After 120 days, the animals were euthanized. Evaluation included clinical assessment, microCT, histological examination of implants, analyses of the adjacent bone, and assessment of zinc, magnesium, and strontium in vital organs (liver, kidneys, brain). The bone sections with the implanted screw were examined via scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS). This method showed that the implant was covered by a thin layer of phosphate-based solid corrosion products with a thickness ranging between 4 and 5 µm. Only negligible changes of the implant volume and area were observed. The degradation was not connected with gas evolution. The screws were fibrointegrated, partially osseointegrated histologically. We observed no inflammatory reaction or bone resorption. Periosteal apposition and formation of new bone with a regular structure were frequently observed near the implant surface. The histological evaluation of the liver, kidneys, and brain showed no toxic changes. The levels of Zn, Mg, and Sr after 120 days in the liver, kidneys, and brain did not exceed the reference values for these elements. The alloy was safe, biocompatible, and well-tolerated.

Automation of training and testing motor and related tasks in pre-clinical behavioural and rehabilitative neuroscience

Testing and training animals in motor and related tasks is a cornerstone of pre-clinical behavioural and rehabilitative neuroscience. Yet manually testing and training animals in these tasks is time consuming and analyses are often subjective. Consequently, there have been many recent advances in automating both the administration and analyses of animal behavioural training and testing. This review is an in-depth appraisal of the history of, and recent developments in, the automation of animal behavioural assays used in neuroscience. We describe the use of common locomotor and non-locomotor tasks used for motor training and testing before and after nervous system injury. This includes a discussion of how these tasks help us to understand the underlying mechanisms of neurological repair and the utility of some tasks for the delivery of rehabilitative training to enhance recovery. We propose two general approaches to automation: automating the physical administration of behavioural tasks (i.e., devices used to facilitate task training, rehabilitative training, and motor testing) and leveraging the use of machine learning in behaviour analysis to generate large volumes of unbiased and comprehensive data. The advantages and disadvantages of automating various motor tasks as well as the limitations of machine learning analyses are examined. In closing, we provide a critical appraisal of the current state of automation in animal behavioural neuroscience and a prospective on some of the advances in machine learning we believe will dramatically enhance the usefulness of these approaches for behavioural neuroscientists.

The corticospinal tract structure of collagen/silk fibroin scaffold implants using 3D printing promotes functional recovery after complete spinal cord transection in rats

No effective treatment has been established for nerve dysfunction caused by spinal cord injury (SCI). Orderly axonal growth at the site of spinal cord transection and creation of an appropriate biological microenvironment are important for functional recovery. To axially guiding axonal growth, designing a collagen/silk fibroin scaffold fabricated with 3D printing technology (3D-C/SF) emulated the corticospinal tract. The normal collagen/silk fibroin scaffold with freeze-drying technology (C/SF) or 3D-C/SF scaffold were implanted into rats with completely transected SCI to evaluate its effect on nerve repair during an 8-week observation period. Electrophysiological analysis and locomotor performance showed that the 3D-C/SF implants contributed to significant improvements in the neurogolical function of rats compared to C/SF group. By magnetic resonance imaging, 3D-C/SF implants promoted a striking degree of axonal regeneration and connection between the proximal and distal SCI sites. Compared with C/SF group, rats with 3D-C/SF scaffold exhibited fewer lesions and disordered structures in histological analysis and more GAP43-positive profiles at the lesion site. The above results indicated that the corticospinal tract structure of 3D printing collagen/silk fibroin scaffold improved axonal regeneration and promoted orderly connections within the neural network, which could provided a promising and innovative approach for tissue repair after SCI.

Combination of Defined CatWalk Gait Parameters for Predictive Locomotion Recovery in Experimental Spinal Cord Injury Rat Models

In many preclinical spinal cord injury (SCI) studies, assessment of locomotion recovery is key to understanding the effectiveness of the experimental intervention. In such rat SCI studies, the most basic locomotor recovery scoring system is a subjective observation of animals freely roaming in an open field, the Basso Beattie Bresnahan (BBB) score. In comparison, CatWalk is an automated gait analysis system, providing further parameter specifications. Although together the CatWalk parameters encompass gait, studies consistently report single parameters, which differ in significance from other behavioral assessments. Therefore, we believe no single parameter produced by the CatWalk can represent the fully-coordinated motion of gait. Typically, other locomotor assessments, such as the BBB score, combine several locomotor characteristics into a representative score. For this reason, we ranked the most distinctive CatWalk parameters between uninjured and SC injured rats. Subsequently, we combined nine of the topmost parameters into an SCI gait index score based on linear discriminant analysis (LDA). The resulting combination was applied to assess gait recovery in SCI experiments comprising of three thoracic contusions, a thoracic dorsal hemisection, and a cervical dorsal column lesion model. For thoracic lesions, our unbiased machine learning model revealed gait differences in lesion type and severity. In some instances, our LDA was found to be more sensitive in differentiating recovery than the BBB score alone. We believe the newly developed gait parameter combination presented here should be used in CatWalk gait recovery work with preclinical thoracic rat SCI models.

In vivo reprogramming of NG2 glia enables adult neurogenesis and functional recovery following spinal cord injury

Adult neurogenesis plays critical roles in maintaining brain homeostasis and responding to neurogenic insults. However, the adult mammalian spinal cord lacks an intrinsic capacity for neurogenesis. Here we show that spinal cord injury (SCI) unveils a latent neurogenic potential of NG2+ glial cells, which can be exploited to produce new neurons and promote functional recovery after SCI. Although endogenous SOX2 is required for SCI-induced transient reprogramming, ectopic SOX2 expression is necessary and sufficient to unleash the full neurogenic potential of NG2 glia. Ectopic SOX2-induced neurogenesis proceeds through an expandable ASCL1+ progenitor stage and generates excitatory and inhibitory propriospinal neurons, which make synaptic connections with ascending and descending spinal pathways. Importantly, SOX2-mediated reprogramming of NG2 glia reduces glial scarring and promotes functional recovery after SCI. These results reveal a latent neurogenic potential of somatic glial cells, which can be leveraged for regenerative medicine.

Motor Coordination Disorders Evaluated through the Grid Test and Changes in the Nigral Nrf2 mRNA Expression in Rats with Pedunculopontine Lesion

Neurotoxic lesion of the pedunculopontine nucleus (PPN) is known to cause subtle motor dysfunctions. However, motor coordination during advance on a discontinuous and elevated surface has not been studied. It is also not known whether there are changes in the mRNA expression of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) in nigral tissue. Methods: The effects of the unilateral neurotoxic lesion of the PPN in motor coordination evaluated through grid test and Nrf2 mRNA expression in nigral tissue were evaluated. Two experimental designs (ED) were organized: ED#1 behavioral study (7 and 30 days after PPN lesion) and ED#2 molecular biology study (24 h, 48 h and 7 days) after PPN lesion. Results: ED#1—The number of faults made with left limbs, were significant higher in the lesioned groups (p < 0.01) both 7 and 30 days post-lesion. The number of failures made by the right limbs, was also significantly higher (p < 0.05) vs. control groups. ED#2—Nrf2 mRNA expression showed an increase 24 h after PPN injury (p < 0.01), followed by a peak of expression 48 h post injury (p < 0.001). Conclusions: Disorders of motor coordination associated with PPN injury are bilateral. The increased Nrf2 mRNA expression could represent an adaptive response to oxidative stress in the nigral tissue following pontine injury.

Inhibiting HMGB1-RAGE axis prevents pro-inflammatory macrophages/microglia polarization and affords neuroprotection after spinal cord injury

Background

Spinal cord injury (SCI) favors a persistent pro-inflammatory macrophages/microglia-mediated response with only a transient appearance of anti-inflammatory phenotype of immune cells. However, the mechanisms controlling this special sterile inflammation after SCI are still not fully elucidated. It is known that damage-associated molecular patterns (DAMPs) released from necrotic cells after injury can trigger severe inflammation. High mobility group box 1(HMGB1), a ubiquitously expressed DNA binding protein, is an identified DAMP, and our previous study demonstrated that reactive astrocytes could undergo necroptosis and release HMGB1 after SCI in mice. The present study aimed to explore the effects and the possible mechanism of HMGB1on macrophages/microglia polarization, as well as the neuroprotective effects by HMGB1 inhibition after SCI.

Methods

In this study, the expression and the concentration of HMGB1 was determined by qRT-PCR, ELISA, and immunohistochemistry. Glycyrrhizin was applied to inhibit HMGB1, while FPS-ZM1 to suppress receptor for advanced glycation end products (RAGE). The polarization of macrophages/microglia in vitro and in vivo was detected by qRT-PCR, immunostaining, and western blot. The lesion area was detected by GFAP staining, while neuronal survival was examined by Nissl staining. Luxol fast blue (LFB) staining, DAB staining, and western blot were adopted to evaluate the myelin loss. Basso-Beattie-Bresnahan (BBB) scoring and rump-height Index (RHI) assay was applied to evaluate locomotor functional recovery.

Results

Our data showed that HMGB1 can be elevated and released from necroptotic astrocytes and HMGB1 could induce pro-inflammatory microglia through the RAGE-nuclear factor-kappa B (NF-κB) pathway. We further demonstrated that inhibiting HMGB1 or RAGE effectively decreased the numbers of detrimental pro-inflammatory macrophages/microglia while increased anti-inflammatory cells after SCI. Furthermore, our data showed that inhibiting HMGB1 or RAGE significantly decreased neuronal loss and demyelination, and improved functional recovery after SCI.

Conclusions

The data implicated that HMGB1-RAGE axis contributed to the dominant pro-inflammatory macrophages/microglia-mediated pro-inflammatory response, and inhibiting this pathway afforded neuroprotection for SCI. Thus, therapies designed to modulate immune microenvironment based on this cascade might be a prospective treatment for SCI.

Criteria for assessing peripheral nerve injury. Behavioral and functional assessment in non-operated Wistar rats

Purpose

To evaluate the normality pattern in functional tests of peripheral nerves.

Methods

Sixty female and sixty male Wistar rats were submitted to vibrissae movement and nictitating reflex for facial nerve; grooming test and grasping test for brachial plexus; and walking tracking test and horizontal ladder test for lumbar plexus. The tests were performed separately, with an interval of seven days between each.

Results

All animals showed the best score in vibrissae movement, nictitating reflex, grooming test, and horizontal ladder test. The best score was acquired for the first time in more than 90% of animals. The mean of strength on the grasping test was 133.46±12.08g for the right and 121.74±8.73g for the left anterior paw. There was a difference between the right and left sides. There was no difference between the groups according to sex. There is no statistical difference comparing all functional indexes between sex, independent of the side analyzed. The peroneal functional index showed higher levels than the sciatic and tibial functional index on both sides and sex.

Conclusions

The behavioral and functional assessment of peripheral nerve regeneration are low-cost, easy to perform, and reliable tests. However, they need to be performed by experienced researchers to avoid misinterpretation.

Intracisternal IGF-1 gene therapy abrogates kainic acid-induced excitotoxic damage of the rat spinal cord

Development of alternative therapies for treating functional deficits after different neurological damages is a challenge in neuroscience. Insulin-like growth factor-1 (IGF-1) is a potent neurotrophic factor exerting neuroprotective actions in brain and spinal cord. It is used to prevent or treat injuries of the central nervous system using different administration routes in different animal models. In this study, we evaluated whether intracisternal (IC) route for IGF-1 gene therapy may abrogate or at least reduce the structural and behavioral damages induced by the intraparenchymal injection of kainic acid (KA) into the rat spinal cord. Experimental (Rad-IGF-1) and control (Rad-DsRed-KA) rats were evaluated using a battery of motor and sensory tests before the injection of the recombinant adenovector (day -3), before KA injection (day 0) and at every post-injection (pi) time point (days 1, 2, 3 and 7 pi). Histopathological changes and neuronal and glial counting were assessed. Pretreatment using IC delivery of RAd-IGF-1 improved animal's general condition and motor and sensory functions as compared to Rad-DsRed-KA-injected rats. Besides, IC Rad-IGF-1 therapy abrogated later spinal cord damage and reduced the glial response induced by KA as observed in Rad-DsRed-KA rats. We conclude that the IC route for delivering RAd-IGF-1 prevents KA-induced excitotoxicity in the spinal cord.

Variability in Open-Field Locomotor Scoring Following Force-Defined Spinal Cord Injury in Rats: Quantification and Implications

Spinal cord injury research in experimental animals aims to define mechanisms of tissue damage and identify interventions that can be translated into effective clinical therapies. Highly reliable models of injury and outcome measurement are essential to achieve these aims and avoid problems with reproducibility. Functional scoring is a critical component of outcome assessment and is currently commonly focused on open field locomotion (the "BBB score"). Here we analyze variability of observed locomotor outcome after a highly regulated spinal cord contusion in a large group of rats that had not received any therapeutic intervention. Our data indicate that, despite tight regulation of the injury severity, there is considerable variability in open-field score of individual rats at 21 days after injury, when the group as a whole reaches a functional plateau. The bootstrapped reference interval (that defines boundaries that contain 95% scores in the population without regard for data distributional character) for the score at 21 days was calculated to range from 2.3 to 15.9 on the 22-point scale. Further analysis indicated that the mean day 21 score of random groups of 10 individuals drawn by bootstrap sampling from the whole study population varies between 9.5 and 13.5. Wide variability between individuals implies that detection of small magnitude group-level treatment effects will likely be unreliable, especially if using small experimental group sizes. To minimize this problem in intervention studies, consideration should be given to assessing treatment effects by comparing proportions of animals in comparator groups that attain pre-specified criterion scores.

Mannitol Reduces Spinal Cord Edema in Rats with Acute Traumatic Spinal Cord Injury

Background:

The research about anti-edema effects of mannitol on acute traumatic spinal cord injury (SCI) in rats is rare.

Objective:

This study aimed to explore the effect of mannitol on spinal cord edema after SCI in rats.

Methods:

Seventy-eight adult female rats were assigned to three groups randomly: a sham control group (n = 18), a contusion and normal saline contrast group (n=30), and a contusion and mannitol treatment group (n=30). We used the open-field test to estimate the functional recovery of rats weekly. Spinal cord water content was measured to determine the spinal cord edema. The ultrastructure features of the injured dorsolateral spinal cord were determined on the 7th day after SCI by HE staining.

Results:

The mannitol group had greatly improved Basso-Beattie-Bresnahan (BBB) scores when compared with the saline contrast group. The spinal cord water content was increased significantly after SCI, and there was no significant difference in the water content between the NaCl and mannitol groups 1 day after SCI. The water content at 3 and 7 days after SCI was significantly lower in the mannitol group than in the NaCl group (p < 0.05). Mannitol can reduce spinal cord edema by increasing the number of red blood cells in the injured spinal cord and decrease the ratio (dorsoventral diameter/ mediolateral diameter) of spinal cord 7 days post-SCI.

Conclusion:

Mannitol increases recovery of motor function in rats, reduces spinal cord edema and increases the number of red blood cells in the injured spinal cord, decreasing the ratio of spinal cord to reduce pressure.

Cannabidiol improves survival and behavioural co-morbidities of Dravet syndrome in mice

Background and Purpose

Dravet syndrome is a severe, genetic form of paediatric epilepsy associated with premature mortality and co‐morbidities such as anxiety, depression, autism, motor dysfunction and memory deficits. Cannabidiol is an approved anticonvulsive drug in the United States and Europe for seizures associated with Dravet syndrome in patients 2 years of age and older. We investigated its potential to prevent premature mortality and improve associated co‐morbidities.

Experimental Approach

The efficacy of sub‐chronic cannabidiol administration in two mouse models of Dravet syndrome was investigated. The effect of cannabidiol on neonatal welfare and survival was studied using Scn1a^−/− mice. We then used a hybrid, heterozygote Scn1a^+/− mouse model to study the effect of cannabidiol on survival and behavioural co‐morbidities: motor deficits (rotarod and static‐beam test), gait abnormality (gait test), social anxiety (social interaction test), anxiety‐like (elevated plus maze) and depressive‐like behaviours (sucrose preference test) and cognitive impairment (radial arm maze test).

Key Results

In Scn1a^−/− mice, cannabidiol increased survival and delayed worsening of neonatal welfare. In Scn1a^+/− mice, chronic cannabidiol administration did not show any adverse effect on motor function and gait, reduced premature mortality, improved social behaviour and memory function, and reduced anxiety‐like and depressive‐like behaviours.

Conclusion and Implications

We are the first to demonstrate a potential disease‐modifying effect of cannabidiol in animal models of Dravet syndrome. Cannabidiol treatment reduced premature mortality and improved several behavioural co‐morbidities in Dravet syndrome mice. These crucial findings may be translated into human therapy to address behavioural co‐morbidities associated with Dravet syndrome.

Quercetin prevents necroptosis of oligodendrocytes by inhibiting macrophages/microglia polarization to M1 phenotype after spinal cord injury in rats

Background

Oligodendrocytes (OLs) death after spinal cord injury (SCI) contributes to demyelination, even leading to a permanent neurological deficit. Besides apoptosis, our previous study demonstrated that OLs underwent receptor-interacting serine-threonine kinase 3(RIP3)/mixed lineage kinase domain-like protein (MLKL)-mediated necroptosis. Considering that necroptosis is always accompanied with pro-inflammatory response and quercetin has long been used as anti-inflammatory agent, in the present study we investigated whether quercetin could inhibit necroptosis of OLs and suppress the M1 macrophages/microglia-mediated immune response after SCI as well as the possible mechanism.

Methods

In this study, we applied quercetin, an important flavonoid component of various herbs, to treat rats with SCI and rats injected with saline were employed as the control group. Locomotor functional recovery was evaluated using Basso-Beattie-Bresnahan (BBB) scoring and rump-height Index (RHI) assay. In vivo, the necroptosis, apoptosis, and regeneration of OLs were detected by immunohistochemistry, 5′-bromo-2′-deoxyuridine (BrdU) incorporation. The loss of myelin and axons after SCI were evaluated by Luxol fast blue (LFB) staining, immunohistochemistry, and electron microscopic study. The polarization of macrophages/microglia after SCI and the underlying mechanisms were detected by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and immunohistochemistry. In vitro, the ATP and reactive oxygen species (ROS) level examination, propidium iodide (PI) labeling, and Western blotting were used to analyze the necroptosis of cultured OLs, while the signaling pathways-mediated polarization of cultured macrophages/microglia was detected by qRT-PCR and Western blotting.

Results

We demonstrated that quercetin treatment improved functional recovery in rats after SCI. We then found that quercetin significantly reduced necroptosis of OLs after SCI without influencing apoptosis and regeneration of OLs. Meanwhile, myelin loss and axon loss were also significantly reduced in quercetin-treated rats, as compared to SCI + saline control. Further, we revealed that quercetin could suppress macrophages/microglia polarized to M1 phenotype through inhibition of STAT1 and NF-κB pathway in vivo and in vitro, which contributes to the decreased necroptosis of OLs.

Conclusions

Quercetin treatment alleviated necroptosis of OLs partially by inhibiting M1 macrophages/microglia polarization after SCI. Our findings suggest that necroptosis of OLs may be a potential therapeutic target for clinical SCI.

Diffusion tensor imaging predicting neurological repair of spinal cord injury with transplanting collagen/chitosan scaffold binding bFGF

Prognosis and treatment evaluation of spinal cord injury (SCI) are still in the long-term research stage. Prognostic factors for SCI treatment need effective biomarker to assess therapeutic effect. Quantitative diffusion tensor imaging (DTI) may become a potential indicators for assessing SCI repair. However, its correlation with the results of locomotor function recovery and tissue repair has not been carefully studied. The aim of this study was to use quantitative DTI to predict neurological repair of SCI with transplanting collagen/chitosan scaffold binding basic fibroblast growth factor (bFGF). To achieve our research goals, T10 complete transection SCI model was established. Then collagen/chitosan mixture adsorbed with bFGF (CCS/bFGF) were implanted into rats with SCI. At 8 weeks after modeling, implanting CCS/bFGF demonstrated more significant improvements in locomotor function according to Basso-Beattie-Bresnahan (BBB) score, inclined-grid climbing test, and electrophysiological examinations. DTI was carried out to evaluate the repair of axons by diffusion tensor tractgraphy (DTT), fractional anisotropy (FA) and apparent diffusion coefficient (ADC), a numerical measure of relative white matter from the rostral to the caudal. Parallel to locomotor function recovery, the CCS/bFGF group could significantly promote the regeneration of nerve fibers tracts according to DTT, magnetic resonance imaging (MRI), Bielschowsky's silver staining and immunofluorescence staining. Positive correlations between imaging and locomotor function or histology were found at all locations from the rostral to the caudal (P < 0.0001). These results demonstrated that DTI might be used as an effective predictor for evaluating neurological repair after SCI in experimental trails and clinical cases.

Prospects of siRNA cocktails as tools for modifying multiple gene targets in the injured spinal cord

Gene silencing through RNA interference (RNAi) has been touted as a boon for identifying potential therapies for difficult-to-treat pathologies. In this regard, siRNA-mediated gene silencing for tackling the multifaceted pathophysiology of spinal cord injury seemed promising. The genes caspase 3 and sarm1 were targeted in the present study, using siRNAs in a rodent model of spinal cord injury, as the feasibility of concomitant silencing of more than one gene had not been previously attempted. The results indicated meager benefits in terms of functional recovery and tissue preservation. Interestingly, differential transfection efficiencies due to the heterogeneous nature of cells in the spinal cord along with variability in efficacy based on time of intervention affected the reproducibility of this approach. Complex gene interactions and inadequacies in molecular evaluation strategies further complicated the interpretation of the outcome. If these glitches are resolved through further research, gene therapy in general and RNAi, in particular, may become a mainstay approach for treating contusion spinal cord injury.

Impact statement

Gene therapy has reached the level of clinical trials. However, safety and efficacy are yet to be confirmed. The present study tested the prospects of gene silencing using siRNAs in a rat model of spinal cord injury. Some noteworthy observations include the effective and long-lasting silencing effects of siRNAs, inhibition of one gene's expression resulting in silencing of multiple genes in associated pathways, possibility of targeting more than one gene through siRNA cocktails, and differential gene silencing effects based on temporal changes in their expression patterns. It is argued that differential uptake of siRNAs by cells as observed and limitations in the analysis methods available can skew interpretations. Thus, this study may serve as a cautionary tale indicating that gene silencing using siRNAs for spinal cord injury can be a potential therapy, but practical issues are to be addressed in order to ensure consistency and safety.

A novel technique to develop thoracic spinal laminectomy and a methodology to assess the functionality and welfare of the contusion spinal cord injury (SCI) rat model

This study reports the advantage of a novel technique employing a motorised dental burr to assist laminectomy over the conventional manual technique at T10-T11 vertebra level in a rat model of spinal cord injury. Twenty-four female rats were randomly assigned to four groups: (1) conventionally laminectomised, (2) dental burr assisted laminectomised, (3) conventionally laminectomised with spinal cord contusion and (4) dental burr assisted laminectomised with spinal cord contusion. Basso Beattie Bresnahan (BBB) score, postoperative body weights, rat grimace scale (RGS), open cage activity and rearing was studied at 1, 7, 14, 21 and 28 days postoperatively, and area of spinal tissue affected was evaluated histologically. Laminectomised and spinal cord injured rats from dental burr groups showed significantly more weight gain and less weight loss respectively in comparison with respective conventionally laminectomised groups at various time points. Significantly higher RGS score was noticed in conventionally laminectomised animals on Day 1 in comparison to burr assisted laminectomy and presence of pain was evident until Day 7 in the conventionally spinal cord injured group. BBB score did not differ between techniques, whereas laminectomy groups showed more resting time than spinal injury groups. High rearing score was significantly higher in groups which underwent dental burr assisted technique at various time points with respect to their conventional counterparts. This study suggests that the use of dental burr assisted technique to perform laminectomy will bring refinement by producing less pain, aiding in better recovery, removing procedural artefacts without affecting the outcome of the model.

Morphine increases macrophages at the lesion site following spinal cord injury: Protective effects of minocycline

Opioids are among the most effective and widely prescribed medications for the treatment of pain following spinal cord injury (SCI). Spinally-injured patients receive opioids within hours of arrival at the emergency room, and prolonged opioid regimens are often employed for the management of post-SCI chronic pain. However, previous studies in our laboratory suggest that the effects of opioids such as morphine may be altered in the pathophysiological context of neurotrauma. Specifically, we have shown that morphine administration in a rodent model of SCI increases mortality and tissue loss at the injury site, and decreases recovery of motor and sensory function, and overall health, even weeks after treatment. The literature suggests that opioids may produce these adverse effects by acting as endotoxins and increasing glial activation and inflammation. To better understand the effects of morphine following SCI, in this study we used flow cytometry to assess immune-competent cells at the lesion site. We observed a morphine-induced increase in the overall number of CD11b+ cells, with marked effects on microglia, in SCI subjects. Next, to investigate whether this increase in the inflammatory profile is necessary to produce morphine's effects, we challenged morphine treatment with minocycline. We found that pre-treatment with minocycline reduced the morphine-induced increase in microglia at the lesion site. More importantly, minocycline also blocked the adverse effects of morphine on recovery of function without disrupting the analgesic efficacy of this opioid. Together, our findings suggest that following SCI, morphine may exacerbate the inflammatory response, increasing cell death at the lesion site and negatively affecting functional recovery.

Effects of Athermal Shortwave Diathermy Treatment on Somatosensory Evoked Potentials and Motor Evoked Potentials in Rats With Spinal Cord Injury

STUDY DESIGN

A study on shortwave diathermy (SWD) versus no treatment following induced spinal cord injury (SCI) in rats.

OBJECTIVE

To investigate the effects of athermal SWD treatment on somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) and hindlimb movements in rats with SCI.

SUMMARY OF BACKGROUND DATA

SWD has been proven to improve vascular circulation and reduce inflammation. However, there have been few studies on neuroprotective effect of SWD on SCI.

METHODS

Twenty-four female Sprague-Dawley (SD) rats were randomly divided into four groups: sham, SCI, SWD, and intact groups. The SCI model was established using the modified Allen weight-drop method. The SWD group received 15 sessions of athermal SWD treatment over a 3-week period of time at 24 hours after SCI. While the sham group and SCI group received no treatment after surgery. Hindlimb movements were evaluated by the Basso, Beattie, and Bresnahan (BBB) scale before surgery, and on days 1, 7, 14, and 21 after the surgery, respectively. The SEP and MEP measurements were simultaneously performed to detect the responses of neural conduction.

RESULTS

The week-by-week BBB scores showed a gradual improvement in the rats of both SCI and SWD groups from the first week to the end of the study; however, the BBB scores of the SWD group were higher than those of the SCI group over the course of 3 weeks. Data from the SEP and MEP measurements showed a significant improvement in the SWD group compared with the SCI group at each time point of observation, with a more prominent increase of amplitude and a more evident reduction of latency. There was a linear correlation between the BBB scores and the latency and amplitude of SEPs or MEPs.

CONCLUSION

Athermal SWD treatment might facilitate the recovery of locomotor function and exert neuroprotective effect on the SCI.

LEVEL OF EVIDENCE

N/A.

Following of aging process in a new motor skill learning model, "pot jumping" in rats

Impairment of procedural memory is a frequent and severe symptom in many neurological and psychiatric diseases as well as during aging. Our aim was to establish an assay in rats in which procedural learning and changes in performance can be studied on the long term. The work was done in the frame of a larger project aiming to establish a complex cognitive animal test battery of high translational value. The equipment was a 190-cm-diameter circular water tank where 12 flower pots were placed upside down in a circle with increasing distances (18-46 cm) between the adjacent ones. Male Lister Hooded and Long-Evans rats were allowed to move on the pots for 3 min. The arena was filled with shallow water to make the rats stay on the pots. Animals were obviously motivated to move around on the pots; however, the distance which required jumping (> 26 cm) meant a barrier for some of them. Development of motor skill was measured by the longest distance successfully spanned. A relatively flat bell-shaped age dependence was observed, with a peak at 13 months of age. A gradual decline in performance could be observed after the age of 20 months which preceded the appearance of overt physical weakness. Long-Evans rats showed more homogeneous performance and higher individual stability than Lister Hooded rats. The method is appropriate to study the development of motor learning and to follow its age-dependent changes. It may also serve as an assay for testing potential drugs for improving motor skills and/or procedural memory.

Spinal Cord Injury: Animal Models, Imaging Tools and the Treatment Strategies

Spinal cord injury (SCI) often leads to irreversible neuro-degenerative changes with life-long consequences. While there is still no effective therapy available, the results of past research have led to improved quality of life for patients suffering from partial or permanent paralysis. In this review we focus on the need, importance and the scientific value of experimental animal models simulating SCI in humans. Furthermore, we highlight modern imaging tools determining the location and extent of spinal cord damage and their contribution to early diagnosis and selection of appropriate treatment. Finally, we focus on available cellular and acellular therapies and novel combinatory approaches with exosomes and active biomaterials. Here we discuss the efficacy and limitations of adult mesenchymal stem cells which can be derived from bone marrow, adipose tissue or umbilical cord blood and its Wharton's jelly. Special attention is paid to stem cell-derived exosomes and smart biomaterials due to their special properties as a delivery system for proteins, bioactive molecules or even genetic material.

Experimental spinal cord injury and behavioral tests in laboratory rats

Traumatic spinal cord injury (SCI) results in some serious neurophysiological consequences that alter healthy body functions and devastate the quality of living of individuals. To find a cure for SCI, researchers around the world are working on different neurorepair and neurorehabilitation modalities. To test a new treatment for SCI as well as to understand the mechanism of recovery, animal models are being widely used. Among them, SCI rat models are arguably the most prominent. Furthermore, it is important to select a suitable behavioral test to evaluate both the motor and sensory recovery following any therapeutic intervention. In this paper, we review the rat models of spinal injury and commonly used behavioral tests to serve as a useful guideline for neuroscientists in the field of SCI research.

Regenerative rehabilitation: exploring the synergistic effects of rehabilitation and implantation of a bio-functional scaffold in enhancing nerve regeneration

Combinatorial approach of rehabilitation and regeneration is essential for functional recovery.

Effects of astaxanthin on sensory-motor function in a compression model of spinal cord injury: Involvement of ERK and AKT signalling pathway

BACKGROUND

Spinal cord injury (SCI) causes continuous neurological deficits and major sensory-motor impairments. There is no effective treatment to enhance sensory-motor function following SCI. Thus, it is crucial to develop novel therapeutics for this particular patient population. Astaxanthin (AST) is a strong antioxidant, anti-inflammatory and anti-apoptotic agent. In the present study, it was tested in a severe compression SCI model with emphasis on sensory-motor outcomes, signalling pathway, along with other complications.

METHODS

A severe SCI was induced by compression of the rat thoracic spinal cord with an aneurysm clip and treatment with AST or the vehicle was carried out, 30 min after injury. Behavioural tests including open field, von Frey, hot plate and BBB were performed weekly to 28 days post-injury. Rats were assigned to measure blood glucose, weight and auricle temperature. Western blot and histological analysis also were performed at the same time points.

RESULTS

AST decreased mechanical and thermal pain and also improved motor function performance, reduced blood glucose and auricle temperature increases and attenuated weight loss in SCI rats. Western blot analysis showed decreased activation of ERK1/2 and increased activation of AKT following AST treatment. The histology results revealed that AST considerably preserved myelinated white matter and the number of motor neurons following SCI.

CONCLUSION

Taken together, the beneficial effects of AST to improve sensory-motor outcomes, attenuate pathological tissue damage and modulate ERK and AKT signalling pathways following SCI, suggest it as a strong therapeutic agent towards clinical applications.

SIGNIFICANCE

Spinal cord injury (SCI) impairs sensory-motor function and causes complications, which astaxanthin (AST) has the potential to be used as a treatment for. The present study investigates the effects of AST in a compression model of SCI with emphasis on sensory-motor outcomes alongside other complications, histopathological damage and also related signalling pathways.

Astaxanthin attenuates neuroinflammation contributed to the neuropathic pain and motor dysfunction following compression spinal cord injury

Spinal cord injury (SCI) is a debilitating condition in which inflammatory responses in the secondary phase of injury leads to long lasting sensory-motor dysfunction. The medicinal therapy of SCI complications is still a clinical challenge. Understanding the molecular pathways underlying the progress of damage will help to find new therapeutic candidates. Astaxanthin (AST) is a ketocarotenoid which has shown anti-inflammatory effects in models of traumatic brain injury. In the present study, we examined its potential in the elimination of SCI damage through glutamatergic-phospo p38 mitogen-activated protein kinase (p-p38MAPK) signaling pathway. Inflammatory response, histopathological changes and sensory-motor function were also investigated in a severe compression model of SCI in male rats. The results of acetone drop and inclined plane tests indicated the promising role of AST in improving sensory and motor function of SCI rats. AST decreased the expression of n-methyl-d-aspartate receptor subunit 2B (NR2B) and p-p38MAPK as inflammatory signaling mediators as well as tumor necrosis factor-α (TNF-α) as an inflammatory cytokine, following compression SCI. The histopathological study culminated in preserved white mater and motor neurons beyond the injury level in rostral and caudal parts. The results show the potential of AST to inhibit glutamate-initiated signaling pathway and inflammatory reactions in the secondary phase of SCI, and suggest it as a promising candidate to enhance functional recovery after SCI.

Sensory and Motor Behavior Evidences Supporting the Usefulness of Conditioned Medium from Dental Pulp-Derived Stem Cells in Spinal Cord Injury in Rats

Study Design

Experimental animal study.

Purpose

This study aimed to assess effects of conditioned medium (CM) of dental pulp-derived stem cells loaded in collagen hydrogel on functional recovery following spinal cord injury (SCI).

Overview of Literature

SCI affects sensory and motor functions, and behavioral recovery is the most essential purpose of therapeutic intervention. Recent studies have reported that CM from dental pulp-derived stem cells has therapeutic benefits. In addition, collagen hydrogel acts as a drug delivery system in SCI experiments.

Methods

Stem cells from human exfoliated deciduous teeth (SHEDs) were cultured, and SHED-CM was harvested and concentrated. Collagen hydrogel containing SHED-CM was prepared. The rats were divided into five groups receiving laminectomy, compressive SCI with or without intraspinal injection of biomaterials (SHED-CM), and collagen hydrogel with or without SHED-CM. Basso, Beattie, and Bresnahan (BBB) scoring, inclined plane, cold allodynia, and beam walk tests were performed for 6 weeks to assess locomotor, motor, sensory, and sensory-motor performances, respectively.

Results

Scores of the rats receiving SHED-CM loaded in collagen hydrogel were significantly better than those of the other injured groups at 1-week post-injury for BBB, 2 weeks for inclined plane, 2 weeks for cold allodynia, and 4 weeks for beam walk tests (p <0.05). The differences remained significant throughout the study.

Conclusions

Intraspinal administration of SHED-CM loaded in collagen hydrogel leads to improved functional recovery and proposes a cell-free therapeutic approach for SCI.

Immediate Enhancement of Nerve Function Using a Novel Axonal Fusion Device After Neurotmesis

Background

The management of peripheral nerve injuries remains a large challenge for plastic surgeons. With the inability to fuse axonal endings, results after microsurgical nerve repair have been inconsistent. Our current nerve repair strategies rely upon the slow and lengthy process of axonal regeneration (~1 mm/d). Polyethylene glycol (PEG) has been investigated as a potential axonal fusion agent; however, the percentage of axonal fusion has been inconsistent. The purpose of this study was to identify a PEG delivery device to standardize outcomes after attempted axonal fusion with PEG.

Materials and Methods

We used a rat sciatic nerve injury model in which we completely transected and repaired the left sciatic nerve to evaluate the efficacy of PEG fusion over a span of 12 weeks. In addition, we evaluated the effectiveness of a delivery device's ability to optimize results after PEG fusion.

Results

We found that PEG rapidly (within minutes) restores axonal continuity as assessed by electrophysiology, fluorescent retrograde tracer, and diffusion tensor imaging. Immunohistochemical analysis shows that motor axon counts are significantly increased at 1 week, 4 weeks, and 12 weeks postoperatively in PEG-treated animals. Furthermore, PEG restored behavioral functions up to 50% compared with animals that received the criterion standard epineurial repair (control animals).

Conclusions

The ability of PEG to rapidly restore nerve function after neurotmesis could have vast implications on the clinical management of traumatic injuries to peripheral nerves.

Rodent, large animal and non-human primate models of spinal cord injury

In this narrative review we aimed to assess the usefulness of the different animal models in identifying injury mechanisms and developing therapies for humans suffering from spinal cord injury (SCI). Results obtained from rodent studies are useful but, due to the anatomical, molecular and functional differences, confirmation of these findings in large animals or non-human primates may lead to basic discoveries that cannot be made in rodent models and that are more useful for developing treatment strategies in humans. SCI in dogs can be considered as intermediate between rodent models and human clinical trials, but the primate models could help to develop appropriate methods that might be more relevant to humans. Ideally, an animal model should meet the requirements of availability and repeatability as well as reproduce the anatomical features and the clinical pathological changing process of SCI. An animal model that completely simulates SCI in humans does not exist. The different experimental models of SCI have advantages and disadvantages for investigating the different aspects of lesion development, recovery mechanisms and potential therapeutic interventions. The potential advantages of non-human primate models include genetic similarities, similar caliber/length of the spinal cord as well as biological and physiological responses to injury which are more similar to humans. Among the potential disadvantages, high operating costs, infrastructural requirements and ethical concerns should be considered. The translation from experimental repair strategies to clinical applications needs to be investigated in future carefully designed studies.

Effect of transplantation of olfactory ensheathing cell conditioned medium induced bone marrow stromal cells on rats with spinal cord injury

Spinal cord injury is a serious threat to human health and various techniques have been deployed to ameliorate or cure its effects. Stem cells transplantation is one of the promising methods. The primary aim of the present study was to investigate the effect of the transplantation of olfactory ensheathing cell (OEC) conditioned medium-induced bone marrow stromal cells (BMSCs) on spinal cord injury. Rat spinal cord compression injury animal models were generated, and the rats divided into the following three groups: Group A, (control) Dulbecco's modified Eagle's medium-treated group; group B, normal BMSC-treated group; group C, OEC conditioned medium-induced BMSC-treated group. The animals were sacrificed at 2, 4 and 8 weeks following transplantation for hematoxylin and eosin staining, and fluorescence staining of neurofilament protein, growth associated protein-43 and neuron-specific nuclear protein. The cavity area of the spinal cord injury was significantly reduced at 2 and 4 weeks following transplantation in group C, and a significant difference between the Basso, Beattie and Bresnahan score in group C and groups A and B was observed. Regenerated nerve fibers were observed in groups B and C; however, a greater number of regenerated nerve fibers were observed in group C. BMSCs induced by OEC conditioned medium survived in vivo, significantly reduced the cavity area of spinal cord injury, promoted nerve fiber regeneration following spinal cord injury and facilitated recovery of motor function. The present study demonstrated a novel method to repair spinal cord injury by using induced BMSCs, with satisfactory results.

Estrogen-like neuroprotection of isopsoralen against spinal cord injury through estrogen receptor ERα

Isopsoralen is a type of furocoumarin that exhibits estrogen-like activities. The aim of this study was to determine the estrogen-like neuroprotection of isopsoralen in an animal model of spinal cord injury (SCI). Results indicated that isopsoralen (intraperitoneal injection of 5 and 10 mg/kg per day for two weeks) significantly enhanced the hindlimb locomotor functions of mice with SCI, as revealed in the BMS score and angle of inclined plane tests. Morphological data showed that isopsoralen significantly attenuated the injury of the gray matter of spinal cord and induced the up-regulation of ERα levels. The neuroprotective effects of isopsolaren were blocked by the ERα antagonist MPP (0.3 mg/kg), but not by the ERβ receptor antagonist PHTPP (0.3 mg/kg). Isopsolaren treatment increased phosphorylated PI3K and AKT (P-PI3K and P-AKT) in the spinal cord of SCI mice and showed a significant anti-apoptotic activity. These results suggest that isopsoralen performs estrogen-like neuroprotection against SCI-induced apoptosis by activating ERα and regulating the PI3K/AKT pathway.

Animal models of spinal cord injury: a systematic review

STUDY DESIGN

PRISMA-guided systematic review.

OBJECTIVES

To provide a comprehensive framework of the current animal models for investigating spinal cord injury (SCI) and categorize them based on the aims, patterns and levels of injury, and outcome measurements as well as animal species.

SETTING

Sina Trauma and Surgery Research Center, Tehran University of Medical Sciences, Tehran, Iran.

METHODS

An electronic search of the Medline database for literature describing animal models of SCI was performed on 1 January 2016 using the following keywords: 'spinal cord injuries' and 'animal models'. The search retrieved 2870 articles. Reviews and non-original articles were excluded. Data extraction was independently performed by two reviewers.

RESULTS

Among the 2209 included studies, testing the effects of drug's or growth factor's interventions was the most common aim (36.6%) followed by surveying pathophysiologic changes (30.2%). The most common spinal region involved was thoracic (81%). Contusion was the most common pattern of injury (41%) followed by transection (32.5%) and compression (19.4%). The most common species involved in animal models of SCI was the rat (72.4%). Two or more types of outcome assessments were used in the majority of the studies, and the most common assessment method was biological plus behavioral (50.8%).

CONCLUSIONS

Prior to choosing an animal model, the objectives of the proposed study must precisely be defined. Contusion and compression models better simulate the biomechanics and neuropathology of human injury, whereas transection models are valuable to study anatomic regeneration. Rodents are the most common and probably best-suited species for preliminary SCI studies.

Effect of ZBD-2 on chronic pain, depressive-like behaviors, and recovery of motor function following spinal cord injury in mice

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ZBD-2 significantly attenuated the symptoms of chronic SCI-pain and pain-induced depressive-like behaviors.

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ZBD-2 inhibited the decreases in the expression of synaptic plasticity-related signaling proteins.

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ZBD-2 reversed chronic, SCI-induced gliocyte activation at the lesion site.

In addition to debilitating sensory and motor deficits, patients with spinal cord injury (SCI) may experience chronic hyperpathic pain (SCI-pain). Recent studies have revealed that translocator protein (TSPO) is involved in repairing neural cells as well as reducing anxiety and depression. However, the role of TSPO in SCI-pain and pain-induced depression remains unknown. The present study aimed to determine the effects of a new TSPO ligand, ZBD-2, on SCI-pain and consequent pain-induced depressive-like behaviors in mice. Treatment with ZBD-2 at either dose significantly attenuated the symptoms of chronic SCI-pain and pain-induced depressive-like behaviors. ZBD-2 reversed SCI-induced elevation of serum corticosterone levels, an index of hyper-activation of the hypothalamic–pituitary–adrenal (HPA) axis. Additionally, administration of ZBD-2 inhibited decreases in the expression of synaptic plasticity-related signaling proteins, including brain-derived neurotrophic factor (BDNF) and cyclic AMP-responsive element binding protein (CREB). Moreover, ZBD-2 administration reversed chronic, SCI-induced gliocyte activation at the lesion site. Therefore, ZBD-2 may improve chronic SCI-pain and pain-induced depressive-like behaviors via suppression of gliocyte activation and restoration of the synaptic plasticity-related signaling systems.

Nor-Binaltorphimine Blocks the Adverse Effects of Morphine after Spinal Cord Injury

Opioids are frequently used for the treatment of pain following spinal cord injury (SCI). Unfortunately, we have shown that morphine administered in the acute phase of SCI results in significant, adverse secondary consequences including compromised locomotor and sensory recovery. Similarly, we showed that selective activation of the κ-opioid receptor (KOR), even at a dose 32-fold lower than morphine, is sufficient to attenuate recovery of locomotor function. In the current study, we tested whether activation of the KOR is necessary to produce morphine's adverse effects using nor-Binaltorphimine (norBNI), a selective KOR antagonist. Rats received a moderate spinal contusion (T12) and 24 h later, baseline locomotor function and nociceptive reactivity were assessed. Rats were then administered norBNI (0, 0.02, 0.08, or 0.32 μmol) followed by morphine (0 or 0.32 μmol). Nociception was reassessed 30 min after drug treatment, and recovery was evaluated for 21 days. The effects of norBNI on morphine-induced attenuation of recovery were dose dependent. At higher doses, norBNI blocked the adverse effects of morphine on locomotor recovery, but analgesia was also significantly decreased. Conversely, at low doses, analgesia was maintained, but the adverse effects on recovery persisted. A moderate dose of norBNI, however, adequately protected against morphine's adverse effects without eliminating its analgesic efficacy. This suggests that activation of the KOR system plays a significant role in the morphine-induced attenuation of recovery. Our research suggests that morphine, and other opioid analgesics, may be contraindicated for the SCI population. Blocking KOR activity may be a viable strategy for improving the safety of clinical opioid use.

Beneficial effects of early hemostasis on spinal cord injury in the rat

STUDY DESIGN

Experimental study.

OBJECTIVES

To investigate the effect of early hemostasis on spinal cord injury (SCI).

SETTING

Fourth Military Medical University, Xi'an, China.

METHODS

Sprague Dawley rats were used. Hematoxylin and eosin (HE) staining was performed to observe hemorrhage at different time points (2, 6, 12, 24 and 48 h) after SCI to determine the time window of hemostatic drug administration (n=3 per time point). Three different concentrations of Etamsylate (0.025, 0.05 and 0.1 g kg-1) were administered immediately and 5 and 10 h after SCI to evaluate the effective dosage (n=6 per group). Another 82 rats were then randomly divided into two groups, Etamsylate group (0.1 g kg-1, n=41) and glucose control group (n=41). Nissl staining was performed to observe neurons at 10 days post injury. Immunohistochemistry, western blot and quantitative real-time PCR were performed to detect tissue necrosis at 7 d.p.i., the activation of astrocytes and microglia/macrophages and lesion cavity at 10 d.p.i. Basso-Beattie-Bresnahan scoring and rump height index assay were used to examine locomotion recovery.

RESULTS

Early hemostasis reduced the lesion area and tissue necrosis, enhanced neuronal survival, alleviated the activation of microglia/macrophages and astrocytes and facilitated functional recovery after spinal cord contusion in rats. Early hemostasis decreased hemorrhage area and lesion area after spinal cord transection in rats.

CONCLUSION

The present study demonstrated that early hemostasis has beneficial effects on SCI in the rat. It has the potential to be translated into clinical practice.

Limited Functional Effects of Subacute Syngeneic Bone Marrow Stromal Cell Transplantation after Rat Spinal Cord Contusion Injury

Cell transplantation might be one means to improve motor, sensory, or autonomic recovery after traumatic spinal cord injury (SCI). Among the different cell types evaluated to date, bone marrow stromal cells (BMSCs) have received considerable interest due to their potential neuroprotective properties. However, uncertainty exists whether the efficacy of BMSCs after intraspinal transplantation justifies an invasive procedure. In the present study, we analyzed the effect of syngeneic BMSC transplantation following a moderate to severe rat spinal cord injury. Adult Fischer 344 rats underwent a T9 contusion injury (200 kDy) followed by grafting of GFP-expressing BMSCs 3 days postinjury. Animals receiving a contusion injury without cellular grafts or an injury followed by grafts of syngeneic GFP-expressing fibroblasts served as control. Eight weeks post-transplantation, BMSC-grafted animals showed only a minor effect in one measure of sensorimotor recovery, no significant differences in tissue sparing, and no changes in the recovery of bladder function compared to both control groups in urodynamic measurements. Both cell types survived in the lesion site with fibroblasts displaying a larger graft volume. Thus, contrary to some reports using allogeneic or xenogeneic transplants, subacute intraparenchymal grafting of syngeneic BMSCs has only a minor effect on functional recovery.