Animals models of spinal cord contusion injury

Body weight-supported treadmill training reduces glial scar overgrowth in SCI rats by decreasing the reactivity of astrocytes during the subacute phase

BACKGROUND

Spinal cord injury is followed by glial scar formation, which was long seen mainly as a physical barrier preventing axonal regeneration. Glial scar astrocytes lead to glial scar formation and produce inhibitory factors to prevent axons from growing through the scar, while inhibiting the conversion of reactive astrocytes into glial scar-forming astrocytes may represent an ideal treatment for CNS injury. Exercise is a non-invasive and effective therapeutic intervention for clinical rehabilitation of spinal cord injury. However, its precise therapeutic mechanisms still need to be continuously explored.

METHODS

30 rats were randomly assigned to three groups (Sham, SCI, SCI + BWSTT; n = 10 rats per group). In this study, we employed the BBB scales and gait analysis system to examine the behavioral functions of the rats in each group. Furthermore, we utilized immunoblotting of spinal cord tissue at the injury site, in addition to histological staining and immunofluorescence staining, to explore glial scar aggregation and axonal regeneration in each group of rats.

RESULTS

Our results revealed that hindlimb motor function was significantly improved in SCI rats after a sustained subacute period of BWSTT, accompanied by the promotion of histological repair and nerve regeneration. Subsequent immunofluorescence staining and immunoblotting showed diminished astrocyte reactivity in the region surrounding the spinal cord injury as well as reduced expression and distribution of collagen fibers near the lesion after BWSTT. Additionally, a significant decrease in the expression of MMP-2/9, which is closely related to astrocyte migration, was observed in the vicinity of spinal cord tissue lesions.

CONCLUSION

Our study demonstrates that a sustained BWSTT intervention during the subacute phase of spinal cord injury can effectively reduce astrocyte reactivity and glial scarring overgrowth, thereby facilitating functional recovery after SCI.

Long-Term Management and Monitoring of the Bladder After Spinal Cord Injury in a Rodent Model

Spinal cord injury (SCI) is a complex clinical condition with a wide range of permanent functional and neurological consequences. A prime factor limiting the patient's quality of life (QoL) is difficulties in bladder function. Chronic animal models that help to develop novel therapeutic strategies are highly demanded, but their availability is scarce and frequently accompanied by substantial limitations. We want to provide our detailed protocols that allow full reproducibility of a novel model for investigating both the acute and chronic condition, and give transparency regarding challenges. The preclinical animal model of female rats with mid-thoracic SCI contusion and a permanently implanted urinary catheter allowed the measuring of bladder function repetitively. Over a period of six months, data were collected weekly from the same, conscious individuals. To our knowledge, this is the first study that obtained a clinically relevant urodynamic dataset seamlessly from the acute to the chronic phase in rats with SCI. The ability to generate a complete data set from one single individual, rather than requiring multiple subjects, has the potential to markedly reduce the number of experimental animals, eliminate group differences, and give more flexibility for therapeutic intervention. Future projects could also benefit from the described optimizations in animal care.

Prok2/PKR signaling regulates ferroptosis after spinal cord injury

Spinal cord injury (SCI) is a severe traumatic condition that often results in significant disability and death. SCI also causes secondary damage in the acute phase due to neuronal cell death. SCI has been linked to ferroptosis, a new type of cell death. Prokineticin 2 (Prok2) and its receptors (PKR1 and PKR2) are involved in various physiological processes and have been shown to regulate ferroptosis in traumatic brain injury. However, the role of Prok2/PKR signaling in SCI-induced ferroptosis and neurodegeneration is unclear. In this study, we examined the expression of Prok2/PKR signaling pathway components and the function of the Prok2/PKR signaling pathway in a rat model of contusion SCI. We found that the expression of Prok2 and PKRs decreased and was subsequently restored after SCI and that Prok2 and PKRs were localized in neurons in the anterior horn of the spinal cord. We also found that the expression levels of the ferroptosis-related proteins glutathione peroxidase 4 (GPX4) and acyl-CoA synthetase long-chain family member 4 (ACSL4) were altered after SCI, suggesting that neurons underwent ferroptosis. Furthermore, we demonstrated that upregulation of Prok2 by intraperitoneal injection of recombinant human Prok2 protein inhibited ferroptosis and reduced neurodegeneration after SCI and that this effect was mediated by PKR1 and PKR2, as silencing these receptors with small interfering RNA (siRNA) reversed recombinant Prok2-mediated ferroptosis inhibition. Our study is the first to reveal that Prok2/PKR signaling plays antiferroptotic and neuroprotective roles in SCI, making it a potential target for SCI treatment.

A comprehensive transcriptional reference for severity and progression in spinal cord injury reveals novel translational biomarker genes

Spinal cord injury (SCI) is a devastating condition that leads to motor, sensory, and autonomic dysfunction. Current therapeutic options remain limited, emphasizing the need for a comprehensive understanding of the underlying SCI-associated molecular mechanisms. This study characterized distinct SCI phases and severities at the gene and functional levels, focusing on biomarker gene identification. Our approach involved a systematic review, individual transcriptomic analysis, gene meta-analysis, and functional characterization. We compiled a total of fourteen studies with 273 samples, leading to the identification of severity- and phase-specific biomarker genes that allow the precise classification of transcriptomic profiles. We investigated the potential transferability of severity-specific biomarkers and identified a twelve-gene signature that predicted injury prognosis from human blood samples. We also report the development of MetaSCI-app - an interactive web application designed for researchers - that allows the exploration and visualization of all generated results ( https://metasci-cbl.shinyapps.io/metaSCI ). Overall, we present a transcriptomic reference and provide a comprehensive framework for assessing SCI considering severity and time perspectives, all integrated into a user-friendly tool.

TLR3 Knockdown Attenuates Pressure-Induced Neuronal Damage In Vitro

The disruption of nerve parenchyma and axonal networks triggered by spinal cord injury (SCI) can initiate a cascade of events associated with secondary injury. Toll-like receptors play a critical role in initiating and regulating immune-inflammatory responses following SCI; however, the precise involvement of Toll-like receptor-3 (TLR3) in secondary neuronal injury remains incompletely understood. To investigate the potential contribution of TLR3 in mediating neuronal pressure-induced damage, we established a stress-induced neuronal damage model using rat anterior horn motor neuron line (VSC4.1), which was subjected to varying levels and durations of sustained pressure. Our findings suggest that pressure induces neuronal damage and apoptosis, and reduced proliferation rates in VSC4.1 cells. Furthermore, this pressure-induced neuronal injury is accompanied by upregulation of TLR3 expression and activation of downstream TLR3 signalling molecules. Knockdown experiments targeting TLR3 significantly alleviate pressure-induced motor neuron injury and apoptosis within the anterior horn region while promoting mitochondria-related autophagy and reducing mitochondrial dysfunction via the TLR3/IRF3 and TLR3/NF-κB pathways.

Injectable alginate chitosan hydrogel as a promising bioengineered therapy for acute spinal cord injury

Dealing with spinal cord injuries presents problematic due to multiple secondary mechanisms. Beyond primary concerns like paralysis and disability, complications including urinary, gastrointestinal, cardiac, and respiratory disorders, along with substantial economic burdens may occur. Limited research focuses on modeling and treating contusion and compression injuries. Tissue engineering emerges as an innovative treatment, targeting lesion pathophysiology. This study was evaluated implanting injectable biomaterials into injury-induced cavity before glial scar formation, avoiding tissue incisions and minimizing further damage. The efficacy of injectable alginate/thiolated chitosan hydrogel was investigated for acute spinal cord injury induced by Vanický method in Wistar rats. Three days post-injury, hydrogel was administrated through microinjection after laminectomy. After 60 days, the hydrogel group demonstrated notable motor function enhancement compared to the control by the BBB locomotor test (P < 0.05). However, no statistically significant differences were observed in MRI assessment concerning lesion severity. Stereological and histopathological evaluations revealed a reduction in vacuole volume and the presence of axon profiles within the scaffold (P < 0.05), alongside reduced infiltration of inflammatory and Gitter cells in the hydrogel group, although the latter was not statistically significant compared to the control. Thiolated chitosan/ alginate hydrogel implantation may be regarded as a promising treatment to enhance motor function by restraining destructive processes post-acute spinal cord injury.

Repeated trans-spinal magnetic stimulation promotes microglial phagocytosis of myelin debris after spinal cord injury through LRP-1

Spinal cord injury (SCI) is a serious trauma of the central nervous system. The clearance of myelin debris is a critical step in the functional recovery following spinal cord injury (SCI). Recent studies have begun to reveal critical roles for professional phagocytes in the central nervous system, microglia, and their receptors in the control of myelin debris in neurodegenerative disease. Repeated trans-spinal magnetic stimulation (rTSMS) has been demonstrated as a noninvasive SCI treatment that enhances tissue repair and functional recovery. In this study, we investigated the role and molecular mechanism of rTSMS on microglial phagocytosis of myelin debris in a rat SCI model. In our studies, we found that rTSMS significantly promoted the motor function recovery of SCI rats associated with the inhibition the neuroinflammation and glia scar formation. Immunofluorescence results further showed that the rTSMS promotes the clearance of myelin debris by microglia in vivo and in vitro. Additionally, receptor-associated protein (RAP), a Low-density lipoprotein receptor-related protein-1 (LRP-1) inhibitor, could cancel the accelerated microglial phagocytosis of myelin debris after rTSMS in vitro experiments. Simultaneously, Elisa's results and western blotting respectively showed that rTSMS significantly decreased the levels of soluble LRP-1(sLRP-1) and the LRP-1 splicing enzyme of ADAM17. In conclusion, rTSMS could promote the clearance of myelin debris by microglia through LRP-1 to improve the functional recovery of SCI rats.

Activation of the sigma-1 receptor ameliorates neuronal ferroptosis via IRE1α after spinal cord injury

Spinal Cord Injury (SCI) is a debilitating disease associated with a significant economic burden owing to its high level of disability; however, current treatment options have only limited efficacy. Past research has shown that iron-dependent programmed cell death, also known as ferroptosis, plays a critical role in the pathogenesis of SCI. The sigma-1 receptor (Sig-1R) is widely distributed in the central nervous system, and has been implicated in the pathophysiology of several neurological and psychiatric disorders. Several in vivo and ex vivo studies have shown that Sig-1R activation exerts unique neuroprotective effects. However, the underlying mechanisms remain unclear. To date, no study has yet demonstrated the association between Sig-1R activation and ferroptosis in patients with SCI. However, the present study found that Sig-1R activation effectively promoted the recovery of motor function in mice after spinal cord injury, attenuated neuronal apoptosis, reduced the production of pro-inflammatory cytokines and iron accumulation, and inhibited ferroptosis in spinal cord tissues following SCI in mice. Ferroptosis and IRE1α were significantly upregulated after spinal cord injury, while sigma-1 receptor agonists were able to facilitate this result through the elimination of inositol-requiring enzyme-1 alpha (IRE1α)-mediated neuronal ferroptosis. Therefore, sigma-1 receptor activation could attenuate ferroptosis after SCI by reducing IRE1α and improving functional recovery after SCI, potentially representing a new therapeutic strategy for treating SCI.

Multi-session transcutaneous spinal cord stimulation prevents chloride homeostasis imbalance and the development of hyperreflexia after spinal cord injury in rat

Spasticity is a complex and multidimensional disorder that impacts nearly 75% of individuals with spinal cord injury (SCI) and currently lacks adequate treatment options. This sensorimotor condition is burdensome as hyperexcitability of reflex pathways result in exacerbated reflex responses, co-contractions of antagonistic muscles, and involuntary movements. Transcutaneous spinal cord stimulation (tSCS) has become a popular tool in the human SCI research field. The likeliness for this intervention to be successful as a noninvasive anti-spastic therapy after SCI is suggested by a mild and transitory improvement in spastic symptoms following a single stimulation session, but it remains to be determined if repeated tSCS over the course of weeks can produce more profound effects. Despite its popularity, the neuroplasticity induced by tSCS also remains widely unexplored, particularly due to the lack of suitable animal models to investigate this intervention. Thus, the basis of this work was to use tSCS over multiple sessions (multi-session tSCS) in a rat model to target spasticity after SCI and identify the long-term physiological improvements and anatomical neuroplasticity occurring in the spinal cord. Here, we show that multi-session tSCS in rats with an incomplete (severe T9 contusion) SCI (1) decreases hyperreflexia, (2) increases the low frequency-dependent modulation of the H-reflex, (3) prevents potassium-chloride cotransporter isoform 2 (KCC2) membrane downregulation in lumbar motoneurons, and (4) generally augments motor output, i.e., EMG amplitude in response to single pulses of tSCS, particularly in extensor muscles. Together, this work displays that multi-session tSCS can target and diminish spasticity after SCI as an alternative to pharmacological interventions and begins to highlight the underlying neuroplasticity contributing to its success in improving functional recovery.

The beneficial effect of α-lipoic acid on spinal cord injury repair in rats is mediated through inhibition of oxidative stress: A transcriptomic analysis

BACKGROUND

Oxidative stress is a crucial factor contributing to the occurrence and development of secondary damage in spinal cord injuries (SCI), ultimately impacting the recovery process. α-lipoic acid (ALA) exhibits potent antioxidant properties, effectively reducing secondary damage and providing neuroprotective benefits. However, the precise mechanism by which ALA plays its antioxidant role remains unknown.

METHODS

We established a model of moderate spinal cord contusion in rats. Experimental rats were randomly divided into 3 distinct groups: the sham group, the model control group (SCI_Veh), and the ALA treatment group (SCI_ALA). The sham group rats were exposed only to the SC without contusion injury. Rats belonging to SCI_Veh group were not administered any treatment after SCI. Rats of SCI_ALA group were intraperitoneally injected with the corresponding volume of ALA according to body weight for three consecutive days after the surgery. Subsequently, three days after SCI, spinal cord samples were obtained from three groups of rats: the sham group, model control group, and administration group. Thereafter, total RNA was extracted from the samples and the expression of three sets of differential genes was analyzed by transcriptome sequencing technology. Real-time PCR was used to verify the sequencing results. The impact of ALA on oxidative stress in rats following SCI was assessed by measuring their total antioxidant capacity and hydrogen peroxide (H2O2) content. The effects of ALA on rat recovery following SCI was investigated through Beattie and Bresnahan (BBB) score and footprint analysis.

RESULTS

The findings from the transcriptome sequencing analysis revealed that the model control group had 2975 genes with altered expression levels when compared to the ALA treatment group. Among these genes, 1583 were found to be upregulated while 1392 were down-regulated. Gene ontology (GO) displayed significant enrichment in terms of functionality, specifically in oxidative phosphorylation, oxidoreductase activity, and signaling receptor activity. The Kyoto encyclopedia of genes and genomes (KEGG) pathway was enriched in oxidative phosphorylation, glutathione metabolism and cell cycle. ALA was found to have multiple benefits for rats after SCI, including increasing their antioxidant capacity and reducing H2O2 levels. Additionally, it was effective in improving motor function (such as 7 days after SCI, the BBB score for SCI_ALA was 8.400 ± 0.937 compared to 7.050 ± 1.141 for SCI_Veh) and promoting histological recovery after SCI (The results of HE demonstrated that the percentage of damage area in was 44.002 ± 6.680 in the SCI_ALA and 57.215 ± 3.964 in the SCI_Veh at the center of injury.). The sequence data from this study has been deposited into Sequence Read Archive (https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE242507).

CONCLUSION

Overall, the findings of this study confirmed the beneficial effects of ALA on recovery in SCI rats through transcriptome sequencing, behavioral, as well histology analyses.

Effects of Moleac 901 after severe spinal cord injury on chronic phase in Wistar rats

Background

MLC901 is a phytopharmaceutical comprising significant compounds that can induce microenvironments conducive to the proliferation and specialization of neural cell progenitors. This study investigates the impact of administering MLC901, reducing the expression of NG2 and caspase-3 and increasing IL-10 levels, as well as histopathological and motor function, after severe spinal cord injury (SCI) in the chronic phase.

Methods

The study employed a randomized post-test-only control group design conducted between February and April 2023 at the Integrated Biomedical Laboratory. The participants in this study were categorized into three distinct groups: normal control, negative control, and therapy. A cohort of 18 rats was utilized for the study, with each group assigned a random allocation of six rats as subjects.

Results

The findings demonstrated a statistically significant disparity in the average NG2 expression (-52.00 ± 20.03; p ≤ 0.05), as well as Caspase-3 expression (-94.89 ± 8.57; p ≤ 0.05), which exhibited a lower magnitude. The levels of IL-10 (8.96 ± 3.98; p ≤ 0.05) were observed to be higher, along with an elevation in BBB score (7.67 ± 0.89; p ≤ 0.05), which was more pronounced in the treatment group compared to the negative control group. The cut-off point for cavitation diameter is determined to be 114.915 μm, exhibiting a sensitivity and specificity of 100%. The area under curve (AUC) value is 1.0. The administration of MLC901 demonstrated a strong positive correlation with the increase in IL-10 levels (B 8.968; p ≤ 0.05), as well as a substantial negative correlation with the decrease in Caspase-3 expression (B -52.000; p ≤ 0.05) and NG2 expression (B -94.892; p ≤ 0.05). The administration of MLC901 via the upregulation of NG2 and Caspase-3 significantly increased the Basso, Beattie, and Bresnahan (BBB) scores.

Conclusions

MLC901 positively affects motor and histopathological outcomes in the chronic phase of severe SCI in the Wistar rat model. These benefits are believed to be achieved by suppressing gliosis, neuroapoptosis, and neuroinflammation processes.

Naringin may promote functional recovery following spinal cord injury by modulating microglial polarization through the PPAR-γ/NF-κB signaling pathway

OBJECTIVE

The flavonoid Naringin (Nar) has been extensively investigated and found to have multiple pharmacological properties, including neuroprotection. Although recent reports have shown that Nar can effectively treat spinal cord injury (SCI), its potential mechanism remains unknown. This study aimed to investigate the effects of Nar on motor recovery and inflammatory responses after SCI and to elucidate its mechanism.

METHODS

SCI rat models were established using Allen's weight-drop method. The rats were intragastrically given Nar (40 mg/kg) for 21 d, and their motor function before surgery and on the 1st, 3rd, 7th, 14th, 21st days after surgery was assessed by the Basso-Beattie-Bresnahan (BBB) scale and examined by the grid walking test (GWT). The enzyme linked immunosorbent assay (ELISA) was used to detect the interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and monocyte chemoattractant protein (MCP)-1 levels in rat spinal cord tissues, and quantitative reverse transcription polymerase chain reaction (qRT-PCR) to measure the mRNA expression levels of microglial activation markers CD68 and ionized calcium binding adaptor molecule 1 (Iba-1), M1 markers inducible nitric oxide synthase (iNOS) and IL-6, and M2 markers CD206 and Arginase 1 (Arg1). The expression levels of peroxisome proliferator-activated receptor gamma/nuclear factor kappa B (PPAR-γ/NF-κB) pathway-related proteins in rat spinal cord tissues were determined using western blotting.

RESULTS

Nar significantly increased the BBB score and decreased the mean error rate of GWT in SCI rats. Additionally, Nar effectively inhibited microglial activation and expression of M1 markers in spinal cord tissues. It also elevated M2 polarization-related gene expression and significantly lowered the levels of inflammatory factors. Further investigation showed that Nar enhanced the expression of PPAR-γ protein and inhibited NF-κB pathway activity.

CONCLUSION

Nar promotes functional recovery by regulating microglial polarization and inhibiting the inflammatory response in SCI, and its mechanism may be related to the PPAR-γ/NF-κB signaling pathway activity.

The cervical ligamentum flavum area: A new sensitive morphological parameter for identifying the cervical spinal stenosis

Thickening of the cervical ligamentum flavum (CLF) has been considered as a main cause of cervical spinal stenosis (CSS). A previous study reported that cervical ligamentum flavum thickness (CLFT) is correlated with CSS. However, the whole hypertrophy is different from focal thickness. Therefore, to analyze hypertrophy of the CLF, we created a new morphological parameter, called the cervical ligamentum flavum area (CLFA). We hypothesized that the CLFA is an important morphological parameter in the diagnosis of CSS. CLF samples were acquired from 83 patients with CSS, and from 84 controls who underwent cervical magnetic resonance imaging (C-MRI). T2-weighted axial C-MRI images were acquired. We measured the CLFA and CLFT at the C6-C7 intervertebral level on C-MRI using appropriate image analysis software. The CLFA was measured as the cross-sectional area of the entire CLF at the level of C6-C7 stenosis. The CLFT was measured by drawing a straight line along the ligament side towards the spinal canal at the C6-C7 level. Mean CLFA was 25.24 ± 6.43 mm2 in the control group and 45.34 ± 9.09 mm2 in the CSS group. The average CLFT was 1.48 ± 0.28 mm in the control group and 2.09 ± 0.35 mm in the CSS group. CSS patients had significantly higher CLFA (P < .01) and CLFT (P < .01). For the validity of both CLFA and CLFT as predictors of CSS, a receiver operating characteristic curve analysis revealed an optimal cutoff point for the CLFA was 31.66 mm2, a sensitivity of 92.8%, specificity of 88.4%, and an area under the curve of 0.97 (95% CI, 0.94-0.99). The optimal cut off-point of the CLFT was 1.79 mm, with a sensitivity of 83.5%, specificity of 84.5%, and an area under the curve of 0.92 (95% CI, 0.87-0.96). Both CLFT and CLFA were significantly related to CSS, but CLFA was the more sensitive measurement parameter. Therefore, to evaluate patients with CSS, treating physicians should test for CLFA.

Multi-session transcutaneous spinal cord stimulation prevents chloridehomeostasis imbalance and the development of spasticity after spinal cordinjury in rat

Spasticity is a complex and multidimensional disorder that impacts nearly 75% of individuals with spinal cord injury (SCI) and currently lacks adequate treatment options. This sensorimotor condition is burdensome as hyperexcitability of reflex pathways result in exacerbated reflex responses, co-contractions of antagonistic muscles, and involuntary movements. Transcutaneous spinal cord stimulation (tSCS) has become a popular tool in the human SCI research field. The likeliness for this intervention to be successful as a noninvasive anti-spastic therapy after SCI is suggested by a mild and transitory improvement in spastic symptoms following a single stimulation session, but it remains to be determined if repeated tSCS over the course of weeks can produce more profound effects. Despite its popularity, the neuroplasticity induced by tSCS also remains widely unexplored, particularly due to the lack of suitable animal models to investigate this intervention. Thus, the basis of this work was to use tSCS over multiple sessions (multi-session tSCS) in a rat model to target spasticity after SCI and identify the long-term physiological improvements and anatomical neuroplasticity occurring in the spinal cord. Here, we show that multi-session tSCS in rats with an incomplete (severe T9 contusion) SCI (1) decreases hyperreflexia, (2) increases the low frequency-dependent modulation of the H-reflex, (3) prevents potassium-chloride cotransporter isoform 2 (KCC2) membrane downregulation in lumbar motoneurons, and (4) generally augments motor output, i.e., EMG amplitude in response to single pulses of tSCS, particularly in extensor muscles. Together, this work displays that multi-session tSCS can target and diminish spasticity after SCI as an alternative to pharmacological interventions and begins to highlight the underlying neuroplasticity contributing to its success in improving functional recovery.

IPSC-Derived Sensory Neurons Directing Fate Commitment of Human BMSC-Derived Schwann Cells: Applications in Traumatic Neural Injuries

The in vitro derivation of Schwann cells from human bone marrow stromal cells (hBMSCs) opens avenues for autologous transplantation to achieve remyelination therapy for post-traumatic neural regeneration. Towards this end, we exploited human induced pluripotent stem-cell-derived sensory neurons to direct Schwann-cell-like cells derived from among the hBMSC-neurosphere cells into lineage-committed Schwann cells (hBMSC-dSCs). These cells were seeded into synthetic conduits for bridging critical gaps in a rat model of sciatic nerve injury. With improvement in gait by 12-week post-bridging, evoked signals were also detectable across the bridged nerve. Confocal microscopy revealed axially aligned axons in association with MBP-positive myelin layers across the bridge in contrast to null in non-seeded controls. Myelinating hBMSC-dSCs within the conduit were positive for both MBP and human nucleus marker HuN. We then implanted hBMSC-dSCs into the contused thoracic cord of rats. By 12-week post-implantation, significant improvement in hindlimb motor function was detectable if chondroitinase ABC was co-delivered to the injured site; such cord segments showed axons myelinated by hBMSC-dSCs. Results support translation into a protocol by which lineage-committed hBMSC-dSCs become available for motor function recovery after traumatic injury to both peripheral and central nervous systems.

A custom-made weight-drop impactor to produce consistent spinal cord injury outcomes in a rat model

Objective

The main objective of this study is to design a custom-made weight-drop impactor device to produce a consistent spinal cord contusion model in rats in order to examine the efficacy of potential therapies for post-traumatic spinal cord injuries (SCIs).

Methods

Adult female Sprague-Dawley rats (n = 24, 11 weeks old) were randomly divided equally into two groups: sham and injured. The consistent injury pattern was produced by a 10 g stainless steel rod dropped from a height of 30 mm to cause (0.75 mm) intended displacement to the dorsal surface of spinal cord. The neurological functional outcomes were assessed at different time intervals using the following standardized neurobehavioral tests: Basso, Beattie, and Bresnahan (BBB) scores, BBB open-field locomotion test, Louisville Swim Scale (LSS), and CatWalk gait analysis system.

Results

Hind limb functional parameters between the two groups using BBB scores and LSS were significantly different (p < 0.05). There were significant differences (p < 0.05) between the SCI group and the sham group for the hind limb functional parameters using the CatWalk gait analysis.

Conclusion

We developed an inexpensive custom-made SCI device that yields a precise adjustment of the height and displacement of the impact relative to the spinal cord surface.

Initiating daily acute intermittent hypoxia (dAIH) therapy at 1-week after contusion spinal cord injury (SCI) improves lower urinary tract function in rat

Spinal cord injury (SCI) above the level of the lumbosacral spinal cord produces lower urinary tract (LUT) dysfunction, resulting in impairment of urine storage and elimination (voiding). While spontaneous functional recovery occurs due to remodeling of spinal reflex micturition pathways, it is incomplete, indicating that additional strategies to further augment neural plasticity following SCI are essential. To this end, acute intermittent hypoxia (AIH) exposure has been proposed as a therapeutic strategy for improving recovery of respiratory and other somatic motor function following SCI; however, the impact of AIH as a therapeutic intervention to improve LUT dysfunction remains to be determined. Therefore, we examined the effects of daily AIH (dAIH) on both spontaneous micturition patterns and reflex micturition event (rME) behaviors in adult female Sprague-Dawley rats with mid-thoracic moderate contusion SCI. For these experiments, dAIH gas exposures (five alternating 3 min 12% O₂ and 21% O₂ episodes) were delivered for 7 consecutive days beginning at 1-week after SCI, with awake micturition patterns being evaluated weekly for 2-3 sessions before and for 4 weeks after SCI and rME behaviors elicited by continuous infusion of saline into the bladder being evaluated under urethane anesthesia at 4-weeks after SCI; daily normoxia (dNx; 21% O₂ episodes) served as a control. At 1-week post-SCI, both an areflexic phenotype (i.e., no effective voiding events) and a functional voiding phenotype (i.e., infrequent voiding events with large volumes) were observed in spontaneous micturition patterns (as expected), and subsequent dAIH, but not dNx, treatment led to recovery of spontaneous void frequency pattern to pre-SCI levels; both dAIH- and dNx-treated rats exhibited slightly increased void volumes. At 4-weeks post-SCI, rME behaviors showed increased effectiveness in voiding in dAIH-treated (compared to dNx-treated) rats that included an increase in both bladder contraction pressure (delta BP; P = 0.014) and dynamic voiding efficiency (P = 0.018). Based on the voiding and non-voiding bladder contraction behaviors (VC and NVC, respectively) observed in the BP records, bladder dysfunction severity was classified into mild, moderate, and severe phenotypes, and while rats in both treatment groups included each severity phenotype, the primary phenotype observed in dAIH-treated rats was mild and that in dNx-treated rats was moderate (P = 0.044). Taken together, these findings suggest that 7-day dAIH treatment produces beneficial improvements in LUT function that include recovery of micturition pattern, more efficient voiding, and decreased NVCs, and extend support to the use of dAIH therapy to treat SCI-induced LUT dysfunction.

5-Fluorouracil reduces the fibrotic scar via inhibiting matrix metalloproteinase 9 and stabilizing microtubules after spinal cord injury

AIMS

Fibrotic scars composed of a dense extracellular matrix are the major obstacles for axonal regeneration. Previous studies have reported that antitumor drugs promote neurofunctional recovery.

METHODS

We investigated the effects of 5-fluorouracil (5-FU), a classical antitumor drug with a high therapeutic index, on fibrotic scar formation, axonal regeneration, and functional recovery after spinal cord injury (SCI).

RESULTS

5-FU administration after hemisection SCI improved hind limb sensorimotor function of the ipsilateral hind paws. 5-FU application also significantly reduced the fibrotic scar formation labeled with aggrecan and fibronectin-positive components, Iba1⁺ /CD11b⁺ macrophages/microglia, vimentin, chondroitin sulfate proteoglycan 4 (NG2/CSPG4), and platelet-derived growth factor receptor beta (PDGFRβ)⁺ pericytes. Moreover, 5-FU treatment promoted stromal cells apoptosis and inhibited fibroblast proliferation and migration by abrogating the polarity of these cells and reducing matrix metalloproteinase 9 expression and promoted axonal growth of spinal neurons via the neuron-specific protein doublecortin-like kinase 1 (DCLK1). Therefore, 5-FU administration impedes the formation of fibrotic scars and promotes axonal regeneration to further restore sensorimotor function after SCI.

Biological Functions and Therapeutic Potential of Autophagy in Spinal Cord Injury

Autophagy is an evolutionarily conserved lysosomal degradation pathway that maintains metabolism and homeostasis by eliminating protein aggregates and damaged organelles. Many studies have reported that autophagy plays an important role in spinal cord injury (SCI). However, the spatiotemporal patterns of autophagy activation after traumatic SCI are contradictory. Most studies show that the activation of autophagy and inhibition of apoptosis have neuroprotective effects on traumatic SCI. However, reports demonstrate that autophagy is strongly associated with distal neuronal death and the impaired functional recovery following traumatic SCI. This article introduces SCI pathophysiology, the physiology and mechanism of autophagy, and our current review on its role in traumatic SCI. We also discuss the interaction between autophagy and apoptosis and the therapeutic effect of activating or inhibiting autophagy in promoting functional recovery. Thus, we aim to provide a theoretical basis for the biological therapy of SCI.

A Simple and Cost-Effective Weight Drop Model to Induce Contusive Spinal Cord Injury: Functional and Histological Outcomes

Background: Animal spinal cord injury (SCI) models have provided a better perception of the mechanisms related to traumatic SCI and evaluation of the effectiveness of experimental therapeutic interventions. Objectives: The aim of this study is to develop a cost-effective modified Allen's device to induce contusive spinal cord injury. Methods: Adult male Wistar rats were subjected to contusive spinal cord injury using a customized weight drop model through 10-g weights delivered from a 25-mm height onto an exposed spinal cord. Locomotor and sensory function during 28 days were assessed. Moreover, histopathological changes were assessed at one week and 28 days post SCI. Results: All the SCI rats showed hind limb paralysis up to 48 h post SCI and neuropathic pain after injury. Histological changes similar to the previous reports for contusion model were observed. Conclusions: According to our findings, little variability was observed in the BBB score of individual rats at 28 days after injury. Our customized device to induce spinal cord injury is a simple and inexpensive alternative method to the highly sophisticated contusion device commonly used to induce SCI.

Prognostic value of cervical ligamentum flavum thickness as a morphological parameter to predict cervical stenosis

One of major causes of cervical central stenosis (CCS) is thickened change of cervical ligament flavum (CLF). The association of a morphological parameter called cervical ligament flavum thickness (CLFT) with CCS has not been reported yet. Thus, the purpose of this research was to investigate the relationship between CCS and CFJT.Data were obtained from 88 patients with CCS. A total of 87 normal controls also underwent cervical spine magnetic resonance imaging (CSMRI). All subjects underwent axial T2-weighted CSMRI. Using our picture archiving and communications system, thickness of ligament flavum of the cervical spine at C6/7 level was analyzed.The mean CLFT was 1.41 ± 0.24 mm in normal subjects and 2.09 ± 0.39 mm in patients with CCS. The CCS group was found to have significantly (P < .001) higher rate of CLFT than normal subjects. ROC curves were used to assess the usefulness of CLFT as a predictor of CCS. In the CCS group, the best practical cut off-point of CLFT was 1.71 mm (sensitivity = 90.9%; specificity = 90.8%), with AUC of 0.94 (95% confidence interval: 0.90--0.98).Greater CLFT values were associated with greater possibility of CCS. Thus, treating physician should carefully examine CLFT, as it can help diagnose CCS.

A New Precision Minimally Invasive Method of Glial Scar Simulation in the Rat Spinal Cord Using Cryoapplication

According to the World Health Organization, every year worldwide up to 500,000 people suffer a spinal cord injury (SCI). Various animal biomodels are essential for searching for novel protocols and therapeutic approaches for SCI treatment. We have developed an original model of post-traumatic spinal cord glial scarring in rats through cryoapplication. With this method the low-temperature liquid nitrogen is used for the cryodestruction of the spinal cord tissue. Forty-five Sprague Dawley (SD) non-linear male rats of the Specific-pathogen-free (SPF) category were included in this experimental study. A Th13 unilateral hemilaminectomy was performed with dental burr using an operating microscope. A specifically designed cryogenic probe was applied to the spinal cord for one minute through the created bone defect. The animals were euthanized at different time points ranging from 1 to 60 days after cold-induced injury. Their Th12-L1 vertebrae with the injured spinal cord region were removed "en bloc" for histological examination. Our data demonstrate that cryoapplication producing a topical cooling around-20°C, caused a highly standardized transmural lesion of the spinal cord in the dorsoventral direction. The lesion had an "hour-glass" shape on histological sections. During the entire study period (days 1-60 of the post-trauma period), the necrotic processes and the development of the glial scar (lesion evolution) were contained in the surgically approached vertebral space (Th13). Unlike other known experimental methods of SCI simulation (compression, contusion, etc.), the proposed technique is characterized by minimal invasiveness, high precision, and reproducibility. Also, histological findings, lesion size, and postoperative clinical course varied only slightly between different animals. An original design of the cryoprobe used in the study played a primary role in the achieving of these results. The spinal cord lesion's detailed functional morphology is described at different time points (1-60 days) after the produced cryoinjury. Also, changes in the number of macrophages at distinct time points, neoangiogenesis and the formation of the glial scar's fibrous component, including morphodynamic characteristics of its evolution, are analyzed. The proposed method of cryoapplication for inducing reproducible glial scars could facilitate a better understanding of the self-recovery processes in the damaged spinal cord. It would be evidently helpful for finding innovative approaches to the SCI treatment.

Acute spinal cord injury: Pathophysiology and pharmacological intervention (Review)

Spinal cord injury (SCI) is one of the most debilitating of all the traumatic conditions that afflict individuals. For a number of years, extensive studies have been conducted to clarify the molecular mechanisms of SCI. Experimental and clinical studies have indicated that two phases, primary damage and secondary damage, are involved in SCI. The initial mechanical damage is caused by local impairment of the spinal cord. In addition, the fundamental mechanisms are associated with hyperflexion, hyperextension, axial loading and rotation. By contrast, secondary injury mechanisms are led by systemic and cellular factors, which may also be initiated by the primary injury. Although significant advances in supportive care have improved clinical outcomes in recent years, a number of studies continue to explore specific pharmacological therapies to minimize SCI. The present review summarized some important pathophysiologic mechanisms that are involved in SCI and focused on several pharmacological and non‑pharmacological therapies, which have either been previously investigated or have a potential in the management of this debilitating injury in the near future.

Optimal Ratio of Wnt3a Expression in Human Mesenchymal Stem Cells Promotes Axonal Regeneration in Spinal Cord Injured Rat Model

Objective

Through our previous clinical trials, the demonstrated therapeutic effects of MSC in chronic spinal cord injury (SCI) were found to be not sufficient. Therefore, the need to develop stem cell agent with enhanced efficacy is increased. We transplanted enhanced Wnt3asecreting human mesenchymal stem cells (hMSC) into injured spines at 6 weeks after SCI to improve axonal regeneration in a rat model of chronic SCI. We hypothesized that enhanced Wnt3a protein expression could augment neuro-regeneration after SCI.

Methods

Thirty-six Sprague-Dawley rats were injured using an Infinite Horizon (IH) impactor at the T9-10 vertebrae and separated into five groups : 1) phosphate-buffered saline injection (injury only group, n=7); 2) hMSC transplantation (MSC, n=7); 3) hMSC transfected with pLenti vector (without Wnt3a gene) transplantation (pLenti-MSC, n=7); 4) hMSC transfected with Wnt3a gene transplantation (Wnt3a-MSC, n=7); and 5) hMSC transfected with enhanced Wnt3a gene (1.7 fold Wnt3a mRNA expression) transplantation (1.7 Wnt3a-MSC, n=8). Six weeks after SCI, each 5×105 cells/15 µL at 2 points were injected using stereotactic and microsyringe pump. To evaluate functional recovery from SCI, rats underwent Basso-Beattie-Bresnahan (BBB) locomotor test on the first, second, and third days post-injury and then weekly for 14 weeks. Axonal regeneration was assessed using growth-associated protein 43 (GAP43), microtubule-associated protein 2 (MAP2), and neurofilament (NF) immunostaining.

Results

Fourteen weeks after injury (8 weeks after transplantation), BBB score of the 1.7 Wnt3a-MSC group (15.0±0.28) was significantly higher than that of the injury only (10.0±0.48), MSC (12.57±0.48), pLenti-MSC (12.42±0.48), and Wnt3a-MSC (13.71±0.61) groups (p<0.05). Immunostaining revealed increased expression of axonal regeneration markers GAP43, MAP2, and NF in the Wnt3a-MSC and 1.7 Wnt3a-MSC groups.

Conclusion

Our results showed that enhanced gene expression of Wnt3a in hMSC can potentiate axonal regeneration and improve functional recovery in a rat model of chronic SCI.

A Systematic Review of Animal Models of Disuse-Induced Bone Loss

OBJECTIVE

Several different animal models are used to study disuse-induced bone loss. This systematic review aims to give a comprehensive overview of the animal models of disuse-induced bone loss and provide a detailed narrative synthesis of each unique animal model.

METHODS

PubMed and Embase were systematically searched for animal models of disuse from inception to November 30, 2019. In addition, Google Scholar and personal file archives were searched for relevant publications not indexed in PubMed or Embase. Two reviewers independently reviewed titles and abstracts for full-text inclusion. Data were extracted using a predefined extraction scheme to ensure standardization.

RESULTS

1964 titles and abstracts were screened of which 653 full-text articles were included. The most common animal species used to model disuse were rats (59%) and mice (30%). Males (53%) where used in the majority of the studies and genetically modified animals accounted for 7%. Twelve different methods to induce disuse were identified. The most frequently used methods were hindlimb unloading (44%), neurectomy (15%), bandages and orthoses (15%), and botulinum toxin (9%). The median time of disuse was 21 days (quartiles: 14 days, 36 days) and the median number of animals per group subjected to disuse was 10 (quartiles: 7, 14). Random group allocation was reported in 43% of the studies. Fewer than 5% of the studies justified the number of animals per group by a sample size calculation to ensure adequate statistical power.

CONCLUSION

Multiple animal models of disuse-induced bone loss exist, and several species of animals have successfully been studied. The complexity of disuse-induced bone loss warrants rigid research study designs. This systematic review emphasized the need for standardization of animal disuse research and reporting.

Jia-Ji Electro-Acupuncture Improves Locomotor Function With Spinal Cord Injury by Regulation of Autophagy Flux and Inhibition of Necroptosis

Jia-Ji electro-acupuncture (EA) has been widely applied in clinic to exhibit curative effects on spinal cord injury (SCI). However, its underlying mechanisms leading to improvement of motor function after SCI remain unclear. Allen’s method was made by NYU Impactor M-III equipment to create the SCI rats model. Rats were randomly divided into four groups: Sham (only laminectomy), Model (SCI group), EA (SCI + Jia-Ji EA treatment), EA + CQ (SCI + Jia-Ji EA treatment + inhibitor chloroquine). Basso-Beattie-Bresnahan assessment showed improvement of hind limb motor function after Jia-Ji electro-acupuncture treatment. Histological change of injured spinal cord tissue was alleviated after treatment, observed by hematoxylin-eosin and Nissl staining. The mRNA and protein expression levels of RIPK1, RIPK3 and MLKL were decreased in EA group. Besides, the increased expression of LC3 and reduced expression of P62 after treatment compared with Model group, confirmed that Jia-Ji electro-acupuncture could enhance the autophagy flux. Electron microscopy imaging showed increasing the number of lysosomes, autophagosomes, and autolysosomes after Jia-Ji electro-acupuncture treatment. Furthermore, inhibition of lysosome function with CQ led to partly eliminate the effect of EA on reducing necroptosis. These data make the case that Jia-Ji electro-acupuncture treatment may improve locomotor function by promoting autophagy flux and inhibiting necroptosis.

Modulation of autophagy for neuroprotection and functional recovery in traumatic spinal cord injury

Spinal cord injury (SCI) is a serious central nervous system trauma that leads to loss of motor and sensory functions in the SCI patients. One of the cell death mechanisms is autophagy, which is 'self-eating' of the damaged and misfolded proteins and nucleic acids, damaged mitochondria, and other impaired organelles for recycling of cellular building blocks. Autophagy is different from all other cell death mechanisms in one important aspect that it gives the cells an opportunity to survive or demise depending on the circumstances. Autophagy is a therapeutic target for alleviation of pathogenesis in traumatic SCI. However, functions of autophagy in traumatic SCI remain controversial. Spatial and temporal patterns of activation of autophagy after traumatic SCI have been reported to be contradictory. Formation of autophagosomes following therapeutic activation or inhibition of autophagy flux is ambiguous in traumatic SCI studies. Both beneficial and harmful outcomes due to enhancement autophagy have been reported in traumatic SCI studies in preclinical models. Only further studies will make it clear whether therapeutic activation or inhibition of autophagy is beneficial in overall outcomes in preclinical models of traumatic SCI. Therapeutic enhancement of autophagy flux may digest the damaged components of the central nervous system cells for recycling and thereby facilitating functional recovery. Many studies demonstrated activation of autophagy flux and inhibition of apoptosis for neuroprotective effects in traumatic SCI. Therapeutic induction of autophagy in traumatic SCI promotes axonal regeneration, supporting another beneficial role of autophagy in traumatic SCI. In contrast, some other studies demonstrated that disruption of autophagy flux in traumatic SCI strongly correlated with neuronal death at remote location and impaired functional recovery. This article describes our current understanding of roles of autophagy in acute and chronic traumatic SCI, cross-talk between autophagy and apoptosis, therapeutic activation or inhibition of autophagy for promoting functional recovery, and future of autophagy in traumatic SCI.

Inhibiting store-operated calcium entry attenuates white matter secondary degeneration following SCI

Axonal degeneration plays a key role in the pathogenesis of numerous neurological disorders including spinal cord injury. After the irreversible destruction of the white matter elements during the primary (mechanical) injury, spared axons and their supporting glial cells begin to breakdown causing an expansion of the lesion site. Here we mechanistically link external sources of calcium entry through axoplasmic reticulum calcium store depletion that contributes to secondary axonal degeneration through a process called store-operated calcium entry. There is increasing evidence suggesting that store-operated calcium entry impairment is responsible for numerous disorders. Nevertheless, its role following spinal cord injury remains poorly understood. We hypothesize that store-operated calcium entry mediates secondary white matter degeneration after spinal cord injury. We used our previously published model of laser-induced spinal cord injury to focally transect mid cervical dorsal column axons from live 6-8-week-old heterozygous CNPase^GFP/+: Thy1^YFP+ double transgenic murine spinal cord preparations (five treated, eight controls) and documented the dynamic changes in axons over time using two-photon excitation microscopy. We report that 1 hour delayed treatment with YM-58483, a potent inhibitor of store-operated calcium entry, significantly decreased intra-axonal calcium accumulation, axonal dieback both proximal and distal to the lesion site, reduced secondary axonal "bystander" damage acutely after injury, and promoted greater oligodendrocyte survival compared to controls. We also targeted store-operated calcium entry following a clinically relevant contusion spinal cord injury model in vivo. Adult, 6-8-week-old Advillin-Cre: Ai9 mice were subjected to a mild 30 kdyn contusion and imaged to observe secondary axonal degeneration in live animals. We found that delayed treatment with YM-58483 increased axonal survival and reduced axonal spheroid formation compared to controls (n = 5 mice per group). These findings suggest that blocking store-operated calcium entry acutely is neuroprotective and introduces a novel target to prevent pathological calcium entry following spinal cord injury using a clinically relevant model.

The correlation between hypoxia-inducible factor-1α, matrix metalloproteinase-9 and functional recovery following chronic spinal cord compression

The molecular mechanisms underlying cervical spondylotic myelopathy (CSM) are poorly understood. To assess the correlation between HIF-1α, MMP-9 and functional recovery following chronic cervical spinal cord compression (CSCI). Rats in the sham group underwent C5 semi-laminectomy, while a water-absorbable polyurethane polymer was implanted into the C6 epidural space in the chronic CSCI group. Basso, Beattie and Bresnahan score and somatosensory evoked potentials were used to evaluate neurological function. Hematoxylin and eosin staining was performed to assess pathological changes in the spinal cord, while immunohistochemical analysis was used to examine HIF-1α and MMP-9 expression on days 7, 28, 42 and 70 post-surgery. Normal rats were only used for HE staining. The BBB score was significantly reduced on day 28 following CSCI, while SEPs exhibited decreased amplitude and increased latency. In chronic CSCI group, the BBB score and SEPs significantly improved on day 70 compared with day 28. HE staining revealed different level of spinal cord edema after chronic CSCI. Compared with the sham group, immunohistochemical analyses revealed that HIF-1α- and MMP-9-positive cells were increased on day 7 and peaked on day 28. HIF-1α and MMP-9 expression were demonstrated to be significantly positively correlated, whereas HIF-1α expression and BBB score were significantly negatively correlated, as well MMP-9 expression and BBB score. HIF-1α and MMP-9 expression are increased following chronic spinal cord compression and are positively correlated with one another. Decreased expression of HIF-1α and MMP-9 may contribute to functional recovery following CSCI. This expression pattern of HIF-1α and MMP-9 may give a new perspective on the molecular mechanisms of CSM.