A consistent, quantifiable, and graded rat lumbosacral spinal cord injury model

Intermediate gray matter interneurons in the lumbar spinal cord play a critical and necessary role in coordinated locomotion

Locomotion is a complex task involving excitatory and inhibitory circuitry in spinal gray matter. While genetic knockouts examine the function of individual spinal interneuron (SpIN) subtypes, the phenotype of combined SpIN loss remains to be explored. We modified a kainic acid lesion to damage intermediate gray matter (laminae V-VIII) in the lumbar spinal enlargement (spinal L2-L4) in female rats. A thorough, tailored behavioral evaluation revealed deficits in gross hindlimb function, skilled walking, coordination, balance and gait two weeks post-injury. Using a Random Forest algorithm, we combined these behavioral assessments into a highly predictive binary classification system that strongly correlated with structural deficits in the rostro-caudal axis. Machine-learning quantification confirmed interneuronal damage to laminae V-VIII in spinal L2-L4 correlates with hindlimb dysfunction. White matter alterations and lower motoneuron loss were not observed with this KA lesion. Animals did not regain lost sensorimotor function three months after injury, indicating that natural recovery mechanisms of the spinal cord cannot compensate for loss of laminae V-VIII neurons. As gray matter damage accounts for neurological/walking dysfunction in instances of spinal cord injury affecting the cervical or lumbar enlargement, this research lays the groundwork for new neuroregenerative therapies to replace these lost neuronal pools vital to sensorimotor function.

A Novel Acute Discogenic Myelopathy Model Using Merocel® Sponge: Comparison With Clip Compression Model in Rats

Objective

Animal models of spinal cord injuries (SCIs) use rats to simulate human SCIs. Among the various techniques, clips have been used to reproduce the compression-contusion model. However, the mechanism of injury in discogenic incomplete SCI may differ from that in clip injury; however, a model has yet to be established. Previously, we issued a patent (No. 10-2053770) for a rat SCI model using Merocel®, a water-absorbing self-expanding polymer sponge. The objectives of this study were to compare the locomotor and histopathological changes between the Merocel®-compression model (MC group) and clip compression model (clip group).

Methods

This study included 4 groups of rats: MC (n=30), MC-sham (n=5), clip (n=30), and clip-sham (n=5). Locomotor function was evaluated in all groups using the Basso, Beattie, and Bresnahan (BBB) scoring system, 4 weeks after injury. Histopathological analyses included morphology, presence of inflammatory cells, microglial activation, and extent of neuronal damage, which were compared among the groups.

Results

The BBB scores in the MC group were significantly higher than those in the clip group throughout the 4 weeks (p<0.01). Neuropathological changes in the MC group were significantly less severe than those in the clip group. In addition, motor neurons were well preserved in the ventral horn of the MC group but poorly preserved in the ventral horn of the clip group.

Conclusion

The novel MC group can help elucidate the pathophysiology of acute discogenic incomplete SCIs and may be applied in various SCI therapeutic strategies.

Circular Ribonucleic Acid Expression Alteration in the Spinal Cord Tissue after Spinal Cord Injury in Rats

BACKGROUND AND PURPOSE

Increased researches focus into pathophysiological mechanisms of spinal cord injury (SCI), particularly toward the relationship between relevant biomarkers and the degree of SCI and prognosis. Circular ribonucleic acids (circRNAs) possess microRNA (miRNA) binding sites that can play the role of miRNA sponges and thus participate in the expression of parental gene modification. This study focused on rat SCI models and explore the relationship between circRNAs and SCI at a genomic level.

METHODS

We first established a rat SCI model and extracted the target spinal cord tissue according to 4 time points. Then investigated the alterations in the circRNA expression by high-throughput whole transcriptome sequencing, analyzed data by gene ontology and the Kyoto Encyclopedia of Genes and Genomes, and constructed the circRNA-miRNA network.

RESULTS

A total of 178 circRNAs were dysregulated (89 upregulated/89 downregulated). Differential circRNAs were found to be mainly involved in the composition of specific organelles in the cytoplasm and are mainly involved in the energy transfer process associated with electron transfer (and similar activities). In all the signaling pathways identified in this study, the MAPK, Wnt, and mTOR signaling pathways are intimately associated with the pathophysiological process of rats post-SCI. In this study, 10 circRNAs with obvious dysregulation were selected for prediction, 26 miRNAs with additional interactions were obtained, and a network diagram of circRNAs-miRNAs was constructed. In this manner, one can understand in further detail the pathogenesis of SCI and to provide new strategies for the prevention, diagnosis, and treatment of SCI-related injuries at the genetic level.

Phrenic motor neuron survival below cervical spinal cord hemisection

Cervical spinal cord injury (cSCI) severs bulbospinal projections to respiratory motor neurons, paralyzing respiratory muscles below the injury. C2 spinal hemisection (C2Hx) is a model of cSCI often used to study spontaneous and induced plasticity and breathing recovery post-injury. One key assumption is that C2Hx dennervates motor neurons below the injury, but does not affect their survival. However, a recent study reported substantial bilateral motor neuron death caudal to C2Hx. Since phrenic motor neuron (PMN) death following C2Hx would have profound implications for therapeutic strategies designed to target spared neural circuits, we tested the hypothesis that C2Hx minimally impacts PMN survival. Using improved retrograde tracing methods, we observed no loss of PMNs at 2- or 8-weeks post-C2Hx. We also observed no injury-related differences in ChAT or NeuN immunolabeling within labelled PMNs. Although we found no evidence of PMN loss following C2Hx, we cannot rule out neuronal loss in other motor pools. These findings address an essential prerequisite for studies that utilize C2Hx as a model to explore strategies for inducing plasticity and/or regeneration within the phrenic motor system, as they provide important insights into the viability of phrenic motor neurons as therapeutic targets after high cervical injury.

Possible therapeutic effect of royal jelly on endometriotic lesion size, pain sensitivity, and neurotrophic factors in a rat model of endometriosis

Endometriosis is the abnormal growth of endometrial tissue. The goals of the study are: (1) Is any correlation between endometriosis pain and neurotrophins in the serum, dorsal root ganglion (DRG), and peritoneal fluid (PF) in rat models of experimental endometriosis?, (2) Possible therapeutic effects of royal jelly (RJ) on pain scores, size of endometriotic lesion, and neurotrophic factors. Forty-eight Sprague Dawley female rats weighing 205.023 ± 21.54 g were maintained in a standard condition. The rats were randomly divided into one of the six groups: Control (no intervention), Sham-1 (remove of uterine horn), RJ (administration of 200 mg/kg/day RJ for 21 days), Endometriosis (induction of endometriosis), Treatment (induction of endometriosis+administration of 200 mg/kg/day RJ for 21 days), and Sham-2 (induction of endometriosis+administration of water). Formalin test performed for pain evaluation. The levels of Brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), substance P, and calcitonin gene-related peptide (CGRP) were measured by enzyme-linked immunosorbent assay. The mean pain scores in all three phases of the formalin test were significantly increased by endometriosis induction (p < 0.05). The concentrations of BDNF, NGF, and CGRP in DRG of the endometriosis group were significantly higher than these factors in the Control, Sham-1, and RJ groups (p < 0.05). RJ could significantly (p < 0.001) decrease the mean lesion size and the mean pain score in the late phase (p < 0.05). The present results determine that endometriosis pain may be related to nervous system neurotrophic factors. Treatment with RJ could decrease the size of endometriosis lesions as well as pain scores. The findings may shed light on other complementary and alternative remedies for endometriosis.

Neuromodulatory effects of repetitive transcranial magnetic stimulation on neural plasticity and motor functions in rats with an incomplete spinal cord injury: A preliminary study

We investigated the effects of intermittent theta-burst stimulation (iTBS) on locomotor function, motor plasticity, and axonal regeneration in an animal model of incomplete spinal cord injury (SCI). Aneurysm clips with different compression forces were applied extradurally around the spinal cord at T10. Motor plasticity was evaluated by examining the motor evoked potentials (MEPs). Long-term iTBS treatment was given at the post-SCI 5th week and continued for 2 weeks (5 consecutive days/week). Time-course changes in locomotor function and the axonal regeneration level were measured by the Basso Beattie Bresnahan (BBB) scale, and growth-associated protein (GAP)-43 expression was detected in brain and spinal cord tissues. iTBS-induced potentiation was reduced at post-1-week SCI lesion and had recovered by 4 weeks post-SCI lesion, except in the severe group. Multiple sessions of iTBS treatment enhanced the motor plasticity in all SCI rats. The locomotor function revealed no significant changes between pre- and post-iTBS treatment in SCI rats. The GAP-43 expression level in the spinal cord increased following 2 weeks of iTBS treatment compared to the sham-treatment group. This preclinical model may provide a translational platform to further investigate therapeutic mechanisms of transcranial magnetic stimulation and enhance the possibility of the potential use of TMS with the iTBS scheme for treating SCIs.

Assessing Pain Behavioral Responses and Neurotrophic Factors in the Dorsal Root Ganglion, Serum and Peritoneal Fluid in Rat Models of Endometriosis

Objective: Pain is the most frequently reported symptom involving in endometriosis. The alterations of neurotrophic factors and certain neuropeptides in the dorsal root ganglion (DRG), as well as serum and peritoneal fluid (PF), were evaluated in rat models of endometriosis.

Materials and methods: Twenty-four Sprague Dawley female rats were selected and maintained in a standard condition with 12 hours’ dark-light cycles. All the rats were randomly assigned to 3 groups: Control (intact rats); Sham (the operation was conducted without endometriosis induction); and Endometriosis (endometriosis induction was performed). The formalin test was performed for all groups on the first and the 21^st day of the study. The assessments of Brain-Derived Neurotrophic Factor (BDNF), Nerve Growth Factor (NGF), Calcitonin Gene-Related Peptide (CGRP), and Substance P levels were carried out by enzyme-linked immunosorbent assay (Elisa). The data were analyzed by One-Way ANOVA. The Tukey’s test was used as post-hoc.

Results: Endometriosis induction significantly increased the mean pain scores in the endometriosis group in all three phases of the formalin test. The concentrations of DRG-CGRP (p=0.035), BDNF (p<0.001), and NGF (p=0.006) in the endometriosis group were significantly higher than that of the other groups while serum-BDNF (p<0.001), Substance P (p=0.009), and NGF (p=0.015) were significantly lower in endometriosis group compared to other groups. The concentrations of PF-BDNF (p=0.025) and Substance P (p=0.009) were significantly lower than those of other groups.

Conclusion: The present results delineate that endometriosis induction could lead to hyperalgesia. This may be related to the significant increases in the BDNF, NGF, and CGRP in DRG.

Effect of Low Intensity Magnetic Field Stimulation on Calcium-Mediated Cytotoxicity After Mild Spinal Cord Contusion Injury in Rats

Background:

Magnetic field (MF) stimulation has the potential to reduce secondary damage and promote functional recovery after neural tissue injury. The study aimed to observe the effect of very low intensity (17.96µT) MF on general body condition, secondary damage, pain status, and locomotion.

Methods:

We exposed rats to MF (2 h/day × 3 weeks) after 6.25 mm contusion spinal injury. Locomotor behavior was evaluated by BBB score, pain assessment was done by recording threshold for tail flick, expression of voltage-gated calcium channels and extent of secondary damage in the spinal cord was assessed by immunofluorescence and Cresyl violet staining, respectively.

Results:

A significant (p ≤ .001) improvement in bladder function as well as BBB score was observed after MF exposure in comparison with sham and SCI over the observation period of 3 weeks. SCI group showed an increase in the threshold for vocalization after discharge, which decreased following MF exposure. Cresyl violet staining showed significantly higher tissue sparing (73%) at the epicenter after MF exposure when compared to SCI group. This was accompanied with a significant decrease in calcium channel expression in MF group as compared to SCI.

Conclusion:

The results suggest facilitation of sensory-motor recovery after MF exposure, which could be due to attenuation of secondary damage and calcium-mediated excitotoxicity in a mild contusion rat model of SCI.

Protective effect of cerium oxide nanoparticles on cisplatin and oxaliplatin primary toxicities in male albino rats

Cisplatin and oxaliplatin are widely used anticancer drugs. Their use is restricted by their dose-limiting side effects: nephrotoxicity and neurotoxicity, respectively. Cerium oxide nanoparticles (CONPs) are promising antioxidant and anti-inflammatory agent. To test the possible ameliorative impact of CONPs on the toxic effect of cisplatin and oxaliplatin in male albino rats. Forty eight rats were divided into 6 groups: control group, CONPs group, cisplatin group, cisplatin and CONPs group, oxaliplatin group, and oxaliplatin and CONPs group. After 4 weeks, serum urea and creatinine, renal tissue level of interleukin 10 (IL10), and total antioxidant (TAO) were measured in control, CONPs, and cisplatin groups. The other kidney was used for histopathological and immunohistochemical studies. The right sciatic nerves and the lumbar spinal cord of rats from control, CONPs, and oxaliplatin groups were used for immunohistochemical evaluations of nitrotyrosine, myelin basic protein (MBP), and glial fibrillary acidic protein (GFAP). Cisplatin significantly increased serum urea and creatinine levels, significantly decreased the kidney level of IL10 and TAO with marked tubular necrosis, hemorrhage and renal damage. Also, it decreased IL10 immunohistochemical expression. CONPs significantly decreased the serum urea and creatinine level and increased IL10 and TAO with lower renal damage and strong IL10 expression compared with cisplatin group. Oxaliplatin significantly decreased MBP immunoreactivity and increased nitrotyrosine immunoreactivity. In the lumbar spinal cord, GFAP immunoreactivity was significantly increased. CONPs significantly increased MBP and decreased nitrotyrosine immunoreactivity. GFAP immunoreactivity was significantly decreased. CONPs ameliorated cisplatin and oxaliplatin primary toxicities through anti-inflammatory and antioxidant characteristics.

Application of Midazolam Injection in Patients with Intraoperative Nerve Block Anesthesia and Sedation Assisted by Imaging Guidance

OBJECTIVE

In the present study, we explored the clinical effect of midazolam as an adjuvant analgesic and tranquilizer after brachial plexus block anesthesia with the aid of imaging guidance.

METHODS

We selected 106 patients who had undergone elective unilateral upper extremity surgery from January 2017 to December 2019 and randomly divided them into groups A and B, with 53 cases in each group. All the patients had undergone brachial plexus block anesthesia. Group A received imidazole-assisted sedation, and group B received fentanyl plus midazolam-assisted sedation. Under ultrasound-guided intermuscular sulcus brachial plexus block, we observed and recorded the ultrasound anatomical images before injection, including the distance from the lower edge of the upper, middle, and lower trunk of the forearm brachial plexus to the skin. We also recorded the anesthesia and operation times, effects of the anesthetic block, and incidence of adverse reactions.

RESULTS

The distance from the lower edge of each nerve trunk to the skin averaged 1.002 cm for the upper stem, 1.598 cm for the middle stem, and 2.26 cm for the lower stem. The average anesthesia procedure time was 3 minutes, 56 seconds and was within 3-5 minutes for 92% of the procedures. The anesthesia effect was excellent, good, and poor in 81%, 11%, and 6%, respectively, and ineffective for 2% and effective for 92%.

CONCLUSIONS

The ultrasound-guided inferior intermuscular sulcus approach for brachial plexus block is suitable for unilateral upper extremity radial hand surgery. For surgery involving the upper extremity ulnar hand side, a larger dose (concentration) of local anesthetic should be used within a safe range and/or an additional ulnar nerve block might be necessary. Midazolam adjuvant medication can have a good sedative and amnestic effect in brachial plexus block anesthesia, helping to reduce pain and inhibit the increase in stress levels.

Correlating Tissue Mechanics and Spinal Cord Injury: Patient-Specific Finite Element Models of Unilateral Cervical Contusion Spinal Cord Injury in Non-Human Primates

Non-human primate (NHP) models are the closest approximation of human spinal cord injury (SCI) available for pre-clinical trials. The NHP models, however, include broader morphological variability that can confound experimental outcomes. We developed subject-specific finite element (FE) models to quantify the relationship between impact mechanics and SCI, including the correlations between FE outcomes and tissue damage. Subject-specific models of cervical unilateral contusion SCI were generated from pre-injury MRIs of six NHPs. Stress and strain outcomes were compared with lesion histology using logit analysis. A parallel generic model was constructed to compare the outcomes of subject-specific and generic models. The FE outcomes were correlated more strongly with gray matter damage (0.29 < R² < 0.76) than white matter (0.18 < R² < 0.58). Maximum/minimum principal strain, Von-Mises and Tresca stresses showed the strongest correlations (0.31 < R² < 0.76) with tissue damage in the gray matter while minimum principal strain, Von-Mises stress, and Tresca stress best predicted white matter damage (0.23 < R² < 0.58). Tissue damage thresholds varied for each subject. The generic FE model captured the impact biomechanics in two of the four models; however, the correlations between FE outcomes and tissue damage were weaker than the subject-specific models (gray matter [0.25 < R² < 0.69] and white matter [R² < 0.06] except for one subject [0.26 < R² < 0.48]). The FE mechanical outputs correlated with tissue damage in spinal cord white and gray matters, and the subject-specific models accurately mimicked the biomechanics of NHP cervical contusion impacts.

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.

Comparisons of motor and sensory abnormalities after lumbar and thoracic contusion spinal cord injury in male rats

Rodent models of contusion spinal cord injury (SCI) are widely studied for the mechanisms underlying functional deficits after SCI. Yet, how does lesion level affect SCI-induced motor and sensory dysfunctions remains unclear. Using a computer-controlled impactor (Impact One™, Leica) and the same parameters (diameter, 2.0 mm; Speed: 4.0 m/s; Depth: 1.5 mm; Dwell time: 0.1 s), we produced contusions at mid-thoracic (T10) and rostral-lumbar (L2) spinal cord in male rats, and compared locomotor and sensory dysfunctions within the same experimental setting. The time courses of locomotor deficit were comparable between thoracic (n = 8) and lumbar (n = 7) SCI rats, but the severity was greater after thoracic SCI especially during the first week post-injury, as indicated by the lower Basso, Beattle and Bresnahan open-field locomotion scores. Both groups showed similar heightened avoiding response (hyper-reactivity) to mechanical stimulation applied at the hindpaws from day 21-56 post-injury, as indicated by decreased paw withdrawal thresholds. Compared to lumbar SCI, thoracic SCI induced a greater decrease of paw withdrawal latency in hot-plate test from day 28-56 post-injury. In contrast, lumbar SCI rats showed a greater reduction of avoidance threshold to mechanical stimulation at the girdle region, and larger overgroomed area than thoracic SCI rats at day 14 post-injury. Thus, thoracic SCI may induce greater motor deficits and hindpaw heat hyper-reactivity than did lumbar SCI. In contrast, lumbar SCI may elicit greater at-level mechanical hyper-reactivity and overgrooming behavior than thoracic SCI. Future study needs to examine the specific pathological changes underlying different dysfunctions in two SCI models.

Free radical scavenger edaravone produces robust neuroprotection in a rat model of spinal cord injury

We used a multimodal approach to evaluate the effects of edaravone in a rat model of spinal cord injury (SCI). SCI was induced by extradural compression of thoracic spinal cord. In experiment 1, 30 min prior to compression, rats received a 3 mg/kg intravenous bolus of edaravone followed by a maintenance infusion of 1 (low-dose), 3 (moderate-dose), or 10 (high-dose) mg/kg/h edaravone. Although both moderate- and high-dose edaravone regimens promoted recovery of spinal motor-evoked potentials (MEPs) at 2 h post-SCI, the effect of the moderate dose was more pronounced. In experiment 2, moderate-dose edaravone was administered 30 min prior to compression, at the start of compression, or 10 min after decompression. Although both preemptive and coincident administration resulted in significantly improved spinal MEPs at 2 h post-SCI, the effect of preemptive administration was more pronounced. A moderate dose of edaravone resulted in significant attenuation of lipid peroxidation, as evidenced by lower concentrations of the free radical malonyldialdehyde in the spinal cord 3 h post-SCI. Malonyldialdehyde levels in the high-dose edaravone group were not reduced. Both moderate- and high-dose edaravone resulted in significant functional improvements, evidenced by better Basso-Beattie-Bresnahan (BBB) scores and better performance on an inclined plane during an 8 week period post-SCI. Both moderate- and high-dose edaravone significantly attenuated neuronal loss in the spinal cord at 8 weeks post-SCI, as evidenced by quantitative immunohistochemical analysis of NeuN-positive cells. In conclusion, early administration of a moderate dose of edaravone minimized the negative consequences of SCI and facilitated functional recovery.

A New Acute Impact-Compression Lumbar Spinal Cord Injury Model in the Rodent

Traumatic injury to the lumbar spinal cord results in complex central and peripheral nervous tissue damage causing significant neurobehavioral deficits and personal/social adversity. Although lumbar cord injuries are common in humans, there are few clinically relevant models of lumbar spinal cord injury (SCI). This article describes a novel lumbar SCI model in the rat. The effects of moderate (20 g), moderate-to-severe (26 g) and severe (35 g, and 56 g) clip impact-compression injuries at the lumbar spinal cord level L1-L2 (vertebral level T11-T12) were assessed using several neurobehavioral, neuroanatomical, and electrophysiological outcome measures. Lesions were generated after meticulous anatomical landmarking using microCT, followed by laminectomy and extradural inclusion of central and radicular elements to generate a traumatic SCI. Clinically relevant outcomes, such as MR and ultrasound imaging, were paired with robust morphometry. Analysis of the lesional tissue demonstrated that pronounced tissue loss and cavitation occur throughout the acute to chronic phases of injury. Behavioral testing revealed significant deficits in locomotion, with no evidence of hindlimb weight-bearing or hindlimb-forelimb coordination in any injured group. Evaluation of sensory outcomes revealed highly pathological alterations including mechanical allodynia and thermal hyperalgesia indicated by increasing avoidance responses and decreasing latency in the tail-flick test. Deficits in spinal tracts were confirmed by electrophysiology showing increased latency and decreased amplitude of both sensory and motor evoked potentials (SEP/MEP), and increased plantar H-reflex indicating an increase in motor neuron excitability. This is a comprehensive lumbar SCI model and should be useful for evaluation of translationally oriented pre-clinical therapies.