Secondary pathology following contusion, dislocation, and distraction spinal cord injuries

Neurophysiological, histological, and behavioral characterization of animal models of distraction spinal cord injury: a systematic review

Distraction spinal cord injury is caused by some degree of distraction or longitudinal tension on the spinal cord and commonly occurs in patients who undergo corrective operation for severe spinal deformity. With the increased degree and duration of distraction, spinal cord injuries become more serious in terms of their neurophysiology, histology, and behavior. Very few studies have been published on the specific characteristics of distraction spinal cord injury. In this study, we systematically review 22 related studies involving animal models of distraction spinal cord injury, focusing particularly on the neurophysiological, histological, and behavioral characteristics of this disease. In addition, we summarize the mechanisms underlying primary and secondary injuries caused by distraction spinal cord injury and clarify the effects of different degrees and durations of distraction on the primary injuries associated with spinal cord injury. We provide new concepts for the establishment of a model of distraction spinal cord injury and related basic research, and provide reference guidelines for the clinical diagnosis and treatment of this disease.

Potential of rosmarinic acid from Orthosiphon aristatus extract for inflammatory induced diseases and its mechanisms of action

Orthosiphon aristatus has been traditionally used as a medicinal herb for various illnesses in Southeast Asia and Europe. The most dominant bioactive compound of the herb is rosmarinic acid (RosA) which has been demonstrated for its remarkable anti-inflammatory properties. This review describes the recent progress of studies on multi-target molecular pathways of RosA in relation to targeted inflammatory-associated diseases. An inclusive literature search was conducted using electronic databases such as Google Scholar, Scopus, Springer Link, PubMed, Medline, Wiley and Science Direct for studies reporting on the anti-inflammatory actions of RosA from 2008 until 2023. The keywords of the search were RosA and anti-inflammatory in relation to hepatoprotective, chondroprotective, cardioprotective, neuroprotective and toxicity. Only publications that are written in English are included in this review. The inhibition and deactivation of pro-inflammatory biomolecules by RosA were explained based on the initial inflammation stimuli and their location in the body. The activation of Nrf2/HO-1 expression to inhibit NF-κB pathway is the key mechanism for hepatoprotection. Besides NF-κB inhibition, RosA activates PPARγ to alleviate ischemia/reperfusion (I/R)-induced myocardial injury for cardioprotection. The regulation of MAPK and T-cell activation is important for chondroprotection, whereas the anti-oxidant property of RosA is the main contributor of neuroprotection. Even though less studies on the anti-inflammation of RosA extracts from O. aristatus, but the effective pharmacological properties of RosA has promoted it as a natural potent lead for further investigation.

Pediatric spinal cord injury with radiographic abnormality: the Beijing experience

BACKGROUND CONTEXT

Spinal cord injury (SCI) without radiographic abnormality (SCIWORA) is a syndrome that usually occurs in children primarily because of the unique biomechanics of the pediatric spine. We recently found that the histopathological and behavioral effects of SCI with radiographic abnormality (SCIWRA) and SCIWORA are very different from each other in animal models. Although numerous studies were conducted to understand the epidemiological and clinical characteristics of the overall pediatric SCI population and the pediatric SCIWORA population, the characteristics of the pediatric SCIWRA population and their differences from those of the SCIWORA population are poorly understood.

PURPOSE

To describe the epidemiology and clinical outcomes of pediatric patients with SCIWRA and their differences from those with SCIWORA.

STUDY DESIGN/SETTING

Retrospective study.

PATIENT SAMPLE

A total of 47 pediatric SCIWRA patients.

OUTCOME MEASURES

Epidemiological characteristics, injury severities, functional deficits, and management and recovery outcomes.

METHODS

Review of all cases with SCIWRA at Beijing Children's Hospital between July 2007 and December 2019 and comparison between the present data and our previous SCIWORA data.

RESULTS

Of the 187 pediatric SCI patients, 47 had SCIWRA (age: 7.06 ± 3.75 years, male-to-female ratio: 3:2). Main causes of SCIWRA were fall (38%) and traffic accidents (38%). Lesions were often located at multiple levels (62%). Incubation period was 3 ± 18 hours. According to the American Spinal Injury Association impairment scale (AIS), many SCIWRA patients had incomplete impairment (AIS B, 9%; AIS C, 9%; AIS D, 32%). Specifically, many of them had abnormal upper and lower limb muscle powers (55% and 60%), upper and lower limb muscle tones (34% and 49%), sensation (38%), and knee, ankle, and abdominal reflexes (47%, 34%, and 36%). 72% of SCIWRA patients were treated with methylprednisolone, dexamethasone, or both. 81% of them showed neurological improvement before discharge. There was no association between corticosteroid therapy and neurological improvement. Moreover, functional outcomes of their upper and lower limb muscle powers were significantly associated with functional outcomes of their upper and lower limb muscle tones (p < 0.01), respectively. In comparison to the SCIWRA population, the SCIWORA population had a higher ratio of younger and female patients of sports-related thoracic injuries with long incubation period leading to lower-body deficits and complete impairment (p<0.05 or p<0.01). Despite all the differences, their neurological improvement was similar (p>0.05).

CONCLUSIONS

Demographic differences exist in the SCIWRA population. Corticosteroids do not appear to be effective in the different types of pediatric SCI. Limb muscle tone may be used to evaluate the functional status of limb muscle power. The epidemiological and clinical characteristics of SCIWRA and SCIWORA are very different from each other. It is important to formulate tailor-made prevention, evaluation, and management strategies for the pediatric population to optimize the SCI outcomes.

Rodent Models of Spinal Cord Injury: From Pathology to Application

Spinal cord injury (SCI) often has devastating consequences for the patient's physical, mental and occupational health. At present, there is no effective treatment for SCI, and appropriate animal models are very important for studying the pathological manifestations, injury mechanisms, and corresponding treatment. However, the pathological changes in each injury model are different, which creates difficulties in selecting appropriate models for different research purposes. In this article, we analyze various SCI models and introduce their pathological features, including inflammation, glial scar formation, axon regeneration, ischemia-reperfusion injury, and oxidative stress, and evaluate the advantages and disadvantages of each model, which is convenient for selecting suitable models for different injury mechanisms to study therapeutic methods.

Surgical Decompression of Traumatic Cervical Spinal Cord Injury: A Pilot Study Comparing Real-Time Intraoperative Ultrasound After Laminectomy With Postoperative MRI and CT Myelography

BACKGROUND

Decompression of the injured spinal cord confers neuroprotection. Compared with timing of surgery, verification of surgical decompression is understudied.

OBJECTIVE

To compare the judgment of cervical spinal cord decompression using real-time intraoperative ultrasound (IOUS) following laminectomy with postoperative MRI and CT myelography.

METHODS

Fifty-one patients were retrospectively reviewed. Completeness of decompression was evaluated by real-time IOUS and compared with postoperative MRI (47 cases) and CT myelography (4 cases).

RESULTS

Five cases (9.8%) underwent additional laminectomy after initial IOUS evaluation to yield a final judgment of adequate decompression using IOUS in all 51 cases (100%). Postoperative MRI/CT myelography showed adequate decompression in 43 cases (84.31%). Six cases had insufficient bony decompression, of which 3 (50%) had cerebrospinal fluid effacement at >1 level. Two cases had severe circumferential intradural swelling despite adequate bony decompression. Between groups with and without adequate decompression on postoperative MRI/CT myelography, there were significant differences for American Spinal Injury Association motor score, American Spinal Injury Association Impairment Scale grade, AO Spine injury morphology, and intramedullary lesion length (IMLL). Multivariate analysis using stepwise variable selection and logistic regression showed that preoperative IMLL was the most significant predictor of inadequate decompression on postoperative imaging (P = .024).

CONCLUSION

Patients with severe clinical injury and large IMLL were more likely to have inadequate decompression on postoperative MRI/CT myelography. IOUS can serve as a supplement to postoperative MRI/CT myelography for the assessment of spinal cord decompression. However, further investigation, additional surgeon experience, and anticipation of prolonged swelling after surgery are required.

Identification of injury type using somatosensory and motor evoked potentials in a rat spinal cord injury model

The spinal cord is at risk of injury during spinal surgery. If intraoperative spinal cord injury is identified early, irreversible impairment or loss of neurological function can be prevented. Different types of spinal cord injury result in damage to different spinal cord regions, which may cause different somatosensory and motor evoked potential signal responses. In this study, we examined electrophysiological and histopathological changes between contusion, distraction, and dislocation spinal cord injuries in a rat model. We found that contusion led to the most severe dorsal white matter injury and caused considerable attenuation of both somatosensory and motor evoked potentials. Dislocation resulted in loss of myelinated axons in the lateral region of the injured spinal cord along the rostrocaudal axis. The amplitude of attenuation in motor evoked potential responses caused by dislocation was greater than that caused by contusion. After distraction injury, extracellular spaces were slightly but not significantly enlarged; somatosensory evoked potential responses slightly decreased and motor evoked potential responses were lost. Correlation analysis showed that histological and electrophysiological findings were significantly correlated and related to injury type. Intraoperative monitoring of both somatosensory and motor evoked potentials has the potential to identify iatrogenic spinal cord injury type during surgery.

Therapeutic targeting of microglia mediated oxidative stress after neurotrauma

Inflammation is a primary component of the central nervous system injury response. Traumatic brain and spinal cord injury are characterized by a pronounced microglial response to damage, including alterations in microglial morphology and increased production of reactive oxygen species (ROS). The acute activity of microglia may be beneficial to recovery, but continued inflammation and ROS production is deleterious to the health and function of other cells. Microglial nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX), mitochondria, and changes in iron levels are three of the most common sources of ROS. All three play a significant role in post-traumatic brain and spinal cord injury ROS production and the resultant oxidative stress. This review will evaluate the current state of therapeutics used to target these avenues of microglia-mediated oxidative stress after injury and suggest avenues for future research.

Clinical safety study of photobiomodulation in acute spinal cord injury by scattering fiber

The study aimed to design a reliable and straightforward PBM method by implanting a medical scattering fiber above surgically exposed spinal cord in SCI patients. Moreover, the safety of this method was examined. Twelve patients with acute SCI (ASIA B) requiring posterior decompression were recruited. The medical scattering fiber was implanted above the spinal cord, and was continuously irradiated at 810 nm, 300 mW, 30 min/day, once per day for 7 days. The vital signs (temperature, blood pressure, respiratory rate, heart rate, and oxygen saturation), infection indicators (WBC, NEUT, hs-CRP, and PCT), photo-allergic reaction indicators (Eosinophil and Basophil), coagulation function indicators (PT, APTT, TT) and neurological stability indicators (ASIA sensory and motor scores) were recorded to evaluate the safety of PBM. Three months after surgery, 12 patients completed follow-up. In our study, direct PBM on SCI site did not cause clinically pathologic changes in vital signs of the patients. All patients had higher WBC, NEUT, and hs-CRP at day 3 during irradiation than those before surgery, and returned to normal at day 7. The changes in Eosinophil and Basophil that were closely associated with allergic reactions were within normal limits throughout the course of irradiation. The coagulation function (PT, APTT, and TT) of patients were also in the normal range. The ASIA sensory and motor scores of all patients had no changes throughout the irradiation process. However, in the follow-up, both ASIA sensory and motor scores of all patients had minor improvement than those in pre-irradiation, and 7 patients had adverse events, but they were not considered to be related to PBM. Our study might firstly employ direct PBM in the SCI by using scattered optical fibers. In a limited sample size, our study concluded that direct PBM at the site of SCI would not produce adverse effects within the appropriate irradiation parameters. The method is safe, feasible, and does not add additional trauma to the patient. Our preliminary study might provide a new methodology for the clinical PBM treatment of acute SCI.

The Role of Microglia/Macrophages Activation and TLR4/NF-κB/MAPK Pathway in Distraction Spinal Cord Injury-Induced Inflammation

Distraction spinal cord injuries (DSCIs) often occur as the neurological complication of distraction forces following the implantation of internal fixation devices during scoliosis correction surgery. However, the underlying mechanism behind these injuries remains unclear. The present study aimed to explore the activation of microglia and macrophages, as well as changes in TLR4-mediated NF-κB and MAPK pathway activity after DSCIs in Bama miniature pigs. Prior to surgical intervention, the pigs were randomly divided into three groups: the sham group, the complete distraction spinal cord injury (CDSCI) group, and the incomplete distraction spinal cord injury (IDSCI) group. After surgery, the Tarlov scale and individual limb motor scale (ILMS) were used to evaluate changes in the pigs’ behavior. All pigs were euthanized 7 days after surgery, and histopathological examinations of the spinal cord tissues were performed. Immunohistochemistry was used to detect Caspase-3 expression in the anterior horn of spinal gray matter tissues. Immunofluorescence staining was utilized to assess the M1/M2 phenotype changes in microglia/macrophages and NF-κB P65 expression in central DSCI lesions, while western blotting was performed to determine the expression of TLR4/NF-κB/MAPK pathway-related proteins. The results of the present study showed that the Tarlov and ILMS scores decreased significantly in the two DSCI groups compared with the sham group. Hematoxylin and eosin (HE) and Nissl staining revealed that the tissue structure and nerve fiber tracts in the distracted spinal cord tissues were destroyed. Both DSCI groups showed the number of survived neurons decreased and the Caspase-3 expression increased. The results of the immunofluorescence staining indicated that the CD16 and CD206 expression in the microglia/macrophages increased. Between the two DSCI groups, the CDSCI group showed increased CD16 and decreased CD206 expression levels. The intensity of the fluorescence of NF-κB P65 was found to be significantly enhanced in pigs with DSCIs. Moreover, western blot results revealed that the expression of TLR4, p-IκBα, NF-κB P65, p-JNK, p-ERK, and p-P38 proteins increased in spinal cord tissues following DSCI. The present study was based on a porcine DSCI model that closely mimicked clinical DSCIs while clarifying DSCI-associated neuroinflammation mechanisms, in turn providing evidence for identifying potential anti-inflammatory targets.

Hydrogels in Spinal Cord Injury Repair: A Review

Traffic accidents and falling objects are responsible for most spinal cord injuries (SCIs). SCI is characterized by high disability and tends to occur among the young, seriously affecting patients' lives and quality of life. The key aims of repairing SCI include preventing secondary nerve injury, inhibiting glial scarring and inflammatory response, and promoting nerve regeneration. Hydrogels have good biocompatibility and degradability, low immunogenicity, and easy-to-adjust mechanical properties. While providing structural scaffolds for tissues, hydrogels can also be used as slow-release carriers in neural tissue engineering to promote cell proliferation, migration, and differentiation, as well as accelerate the repair of damaged tissue. This review discusses the characteristics of hydrogels and their advantages as delivery vehicles, as well as expounds on the progress made in hydrogel therapy (alone or combined with cells and molecules) to repair SCI. In addition, we discuss the prospects of hydrogels in clinical research and provide new ideas for the treatment of SCI.

Progression in translational research on spinal cord injury based on microenvironment imbalance

Spinal cord injury (SCI) leads to loss of motor and sensory function below the injury level and imposes a considerable burden on patients, families, and society. Repair of the injured spinal cord has been recognized as a global medical challenge for many years. Significant progress has been made in research on the pathological mechanism of spinal cord injury. In particular, with the development of gene regulation, cell sequencing, and cell tracing technologies, in-depth explorations of the SCI microenvironment have become more feasible. However, translational studies related to repair of the injured spinal cord have not yielded significant results. This review summarizes the latest research progress on two aspects of SCI pathology: intraneuronal microenvironment imbalance and regenerative microenvironment imbalance. We also review repair strategies for the injured spinal cord based on microenvironment imbalance, including medications, cell transplantation, exosomes, tissue engineering, cell reprogramming, and rehabilitation. The current state of translational research on SCI and future directions are also discussed. The development of a combined, precise, and multitemporal strategy for repairing the injured spinal cord is a potential future direction.

Effects of FTY720 on Neural Cell Behavior in Two and Three-Dimensional Culture and in Compression Spinal Cord Injury

Introduction

The present study aimed to evaluate the effects of FTY720 as a neuromodulatory drug on the behaviors of neural stem/progenitor cells (NS/PCs) in two-dimensional (2-D) and three-dimensional (3-D) cultures and in spinal cord injury (SCI).

Methods

The NS/PCs isolated from the ganglionic eminence of the 13.5-day old embryos were cultured as free-floating spheres. The single cells obtained from the second passage were cultured in 96-well plates without any scaffold (2-D) or containing PuraMatrix (PM, 3-D) or were used for transplantation in a mouse model of compression SCI. After exposure to 0, 10, 50, and 100 nanomolar of FTY720, the survival, proliferation, and migration of the NS/PCs were evaluated in vitro using MTT assay, neurosphere assay, and migration assay, respectively. Moreover, the functional recovery, survival and migration capacity of transplanted cells exposure to 100 nanomolar FTY720 were investigated in SCI.

Results

Cell survival and migration capacity increased after exposure to 50 and 100 nanomolar FTY720. In addition, higher doses of FTY720 led to the formation of more extensive and more neurospheres. Although this phenomenon was similar in both 2-D and 3-D cultures, PM induced better distribution of the cells in a 3-D environment. Furthermore, co-administration of FTY720 and NS/PCs 7 days after SCI enhanced functional recovery and both survival and migration of transplanted cells in the lesion site.

Conclusions

Due to the positive effects of FTY720 on the behavior of NS/PCs, using them in combination therapies can be an appealing approach for stem cell therapy in CNS injury.

Temporal Progression of Acute Spinal Cord Injury Mechanisms in a Rat Model: Contusion, Dislocation, and Distraction

Traumatic spinal cord injuries (SCIs) occur due to different spinal column injury patterns, including burst fracture, dislocation, and flexion-distraction. Pre-clinical studies modeling different SCI mechanisms have shown distinct histological differences between these injuries both acutely (3 h and less) and chronically (8 weeks), but there remains a temporal gap. Different rates of injury progression at specific regions of the spinal cord may provide insight into the pathologies that are initiated by specific SCI mechanisms. Therefore, the objective of this study was to evaluate the temporal progression of injury at specific tracts within the white matter, for time-points of 3 h, 24 h, and 7 days, for three distinct SCI mechanisms. In this study, 96 male Sprague Dawley rats underwent one of three SCI mechanisms: contusion, dislocation, or distraction. Animals were sacrificed at one of three times post-injury: 3 h, 24 h, or 7 days. Histological analysis using eriochrome cyanide and immunostaining for MBP, SMI-312, neurofilament-H (NF-H), and β-III tubulin were used to characterize white matter sparing and axon and myelinated axon counts. The regions analyzed were the gracile fasciculus, cuneate fasciculus, dorsal corticospinal tract, and ventrolateral white matter. Contusion, dislocation, and distraction SCIs demonstrated distinct damage patterns that progressed differently over time. Myelinated axon counts were significantly reduced after dislocation and contusion injuries in most locations and time-points analyzed (compared with sham). This indicates early myelin damage often within 3 h. Myelinated axon counts after distraction dropped early and did not demonstrate any significant progression over the next 7 days. Important differences in white matter degeneration were identified between injury types, with distraction injuries showing the least variability across time-points These findings and the observation that white matter injury occurs early, and in many cases, without much dynamic change, highlight the importance of injury type in SCI research-both clinically and pre-clinically.

Local delivery of fingolimod through PLGA nanoparticles and PuraMatrix-embedded neural precursor cells promote motor function recovery and tissue repair in spinal cord injury

Spinal cord injury (SCI) is a devastating clinical problem that can lead to permanent motor dysfunction. Fingolimod (FTY720) is a sphingosine structural analogue, and recently, its therapeutic benefits in SCI have been reported. The present study aimed to evaluate the therapeutic efficacy of fingolimod-incorporated poly lactic-co-glycolic acid (PLGA) nanoparticles (nanofingolimod) delivered locally together with neural stem/progenitor cells (NS/PCs) transplantation in a mouse model of contusive acute SCI. Fingolimod was encapsulated in PLGA nanoparticles by the emulsion-evaporation method. Mouse NS/PCs were harvested and cultured from embryonic Day 14 (E14) ganglionic eminences. Induction of SCI was followed by the intrathecal delivery of nanofingolimod with and without intralesional transplantation of PuraMatrix-encapsulated NS/PCs. Functional recovery, injury size and the fate of the transplanted cells were evaluated after 28 days. The nanofingolimod particles represented spherical morphology. The entrapment efficiency determined by UV-visible spectroscopy was approximately 90%, and the drug content of fingolimod loaded nanoparticles was 13%. About 68% of encapsulated fingolimod was slowly released within 10 days. Local delivery of nanofingolimod in combination with NS/PCs transplantation led to a stronger improvement in neurological functions and minimized tissue damage. Furthermore, co-administration of nanofingolimod and NS/PCs not only increased the survival of transplanted cells but also promoted their fate towards more oligodendrocytic phenotype. Our data suggest that local release of nanofingolimod in combination with three-dimensional (3D) transplantation of NS/PCs in the acute phase of SCI could be a promising approach to restore the damaged tissues and improve neurological functions.

Feruloylated Oligosaccharides Alleviate Central Nervous Inflammation in Mice Following Spinal Cord Contusion

As one of the empirical models of the chronic central inflammatory response, a spinal cord injury (SCI) deteriorates the neuronal survival and results in irreversible motor and sensory dysfunction below the injury area. Our previous studies have reported that maize bran feruloylated oligosaccharides (FOs) exert significant anti-inflammatory activities both in diabetes and colitis. However, no direct evidence of FOs alleviating central nervous inflammation was stated. This study aimed to investigate the therapeutic effect of FOs on SCI and its potential mechanism. Our results indicated that 4 weeks of FO administration effectively mitigated the inflammatory response via decreasing the number of microglia (labelled with Iba1), result in the expression of IL-1α, IL-2, IL-6, IL-18 and TNF-α downregulating, but the level of IL-10 and BDNF increases in the injured spinal cord. Moreover, FOs enhanced neuronal survival, ameliorated the scar cavities, and improved behaviors, including Basso mouse scale (BMS) scores and the gait of mice after SCI. Together, these results demonstrated that administration of FOs showed superior functional recovery effects in a SCI model. Also, FOs may modulate inflammatory activities by regulating the expression of proinflammatory factors, decreasing the production of inflammatory cells, and promoting functional recovery through the MAPK pathway following SCI.

Progress in Stem Cell Therapy for Spinal Cord Injury

Background

Spinal cord injury (SCI) is one of the serious neurological diseases that occur in young people with high morbidity and disability. However, there is still a lack of effective treatments for it. Stem cell (SC) treatment of SCI has gradually become a new research hotspot over the past decades. This article is aimed at reviewing the research progress of SC therapy for SCI.

Methods

Review the literature and summarize the effects, strategies, related mechanisms, safety, and clinical application of different SC types and new approaches in combination with SC in SCI treatment.

Results

A large number of studies have focused on SC therapy for SCI, most of which showed good effects. The common SC types for SCI treatment include mesenchymal stem cells (MSCs), hematopoietic stem cells (HSCs), neural stem cells (NSCs), induced pluripotent stem cells (iPSCs), and embryonic stem cells (ESCs). The modes of treatment include in vivo and in vitro induction. The pathways of transplantation consist of intravenous, transarterial, nasal, intraperitoneal, intrathecal, and intramedullary injections. Most of the SC treatments for SCI use a number of cells ranging from tens of thousands to millions. Early or late SC administration, application of immunosuppressant or not are still controversies. Potential mechanisms of SC therapy include tissue repair and replacement, neurotrophy, and regeneration and promotion of angiogenesis, antiapoptosis, and anti-inflammatory. Common safety issues include thrombosis and embolism, tumorigenicity and instability, infection, high fever, and even death. Recently, some new approaches, such as the pharmacological activation of endogenous SCs, biomaterials, 3D print, and optogenetics, have been also developed, which greatly improved the application of SC therapy for SCI.

Conclusion

Most studies support the effects of SC therapy on SCI, while a few studies do not. The cell types, mechanisms, and strategies of SC therapy for SCI are very different among studies. In addition, the safety cannot be ignored, and more clinical trials are required. The application of new technology will promote SC therapy of SCI.

Effects of rosmarinic acid on nervous system disorders: an updated review

Nowadays, the worldwide interest is growing to use medicinal plants and their active constituents to develop new potent medicines with fewer side effects. Precise dietary compounds have prospective beneficial applications for various neurodegenerative ailments. Rosmarinic acid is a polyphenol and is detectable most primarily in many Lamiaceae families, for instance, Rosmarinus officinalis also called rosemary. This review prepared a broad and updated literature review on rosmarinic acid elucidating its biological activities on some nervous system disorders. Rosmarinic acid has significant antinociceptive, neuroprotective, and neuroregenerative effects. In this regard, we classified and discussed our findings in different nervous system disorders including Alzheimer's disease, epilepsy, depression, Huntington's disease, familial amyotrophic lateral sclerosis, Parkinson's disease, cerebral ischemia/reperfusion injury, spinal cord injury, stress, anxiety, and pain.

Rosmarinic acid exerts a neuroprotective effect on spinal cord injury by suppressing oxidative stress and inflammation via modulating the Nrf2/HO-1 and TLR4/NF-κB pathways

Spinal cord injury (SCI) is a severe central nervous system injury for which few efficacious drugs are available. Rosmarinic acid (RA), a water-soluble polyphenolic phytochemical, has antioxidant, anti-inflammatory, and anti-apoptotic properties. However, the effect of RA on SCI is unclear. We investigated the therapeutic effect and underlying mechanism of RA on SCI. Using a rat model of SCI, we showed that RA improved locomotor recovery after SCI and significantly mitigated neurological deficit, increased neuronal preservation, and reduced apoptosis. Also, RA inhibited activation of microglia and the release of TNF-α, IL-6, and IL-1β and MDA. Moreover, proteomics analyses identified the Nrf2 and NF-κB pathways as targets of RA. Pretreatment with RA increased levels of Nrf2 and HO-1 and reduced those of TLR4 and MyD88 as well as phosphorylation of IκB and subsequent nuclear translocation of NF-κB-p65. Using H2O2- and LPS-induced PC12 cells, we found that RA ameliorated the H2O2-induced decrease in viability and increase in apoptosis and oxidative injury by activating the Nrf2/HO-1 pathway. Also, LPS-induced cytotoxicity and increased apoptosis and inflammatory injury in PC-12 cells were mitigated by RA by inhibiting the TLR4/NF-κB pathway. The Nrf2 inhibitor ML385 weakened the effect of RA on oxidant stress, inflammation and apoptosis in SCI rats, and significantly increased the nuclear translocation of NF-κB. Therefore, the neuroprotective effect on SCI of RA may be due to its antioxidant and anti-inflammatory properties, which are mediated by modulation of the Nrf2/HO-1 and TLR4/NF-κB pathways. Moreover, RA activated Nrf2/HO-1, which amplified its inhibition of the NF-κB pathway.

Effect of Velocity and Duration of Residual Compression in a Rat Dislocation Spinal Cord Injury Model

Early decompression of the traumatically injured and persistently compressed spinal cord is intuitively beneficial for neurological outcome. Despite considerable pre-clinical evidence of a neurological benefit to early decompression, the effect of early surgical decompression in clinical spinal cord injury (SCI) remains less clear. The discrepancy between pre-clinical and clinical results may be due to differences between the biomechanical variables used in pre-clinical animal models and the biomechanical conditions occurring in clinical injuries. These pre-clinical variables include region of spinal cord, velocity of impact, and injury mechanism. In this study, the effect of velocity and duration of residual compression on injury severity were evaluated using a novel, rodent model of cervical dislocation SCI. Fifty-two male Sprague-Dawley rats were included in five groups: two timings of decompression (24 min, 240 min), two velocities (10 mm/sec, 500 mm/sec), and a sham group. All injuries involved a 1.45-mm dorsal dislocation of the C6 vertebra relative to C5 with subsequent residual compression of 0.8 mm. Animals were evaluated for motor function using the Martinez open field, grip strength, and grooming tests for 6 weeks post-injury. Immunohistochemistry and histology following sacrifice were conducted with counts for NeuN- and choline acetyltransferase (ChAT)-positive neurons, and length of cavitation. Behavioral testing and histological analysis revealed that injuries induced by the high velocity were consistently more severe than those induced by the low velocity, with behavioral correlations ranging between 0.46 and 0.58 (p < 0.05). Longer duration of residual compression did not produce significantly more severe injuries as measured by functional tests and histology. These findings demonstrate that the velocity of the initial traumatic impact may be a more important factor than duration of residual compression in determining SCI severity in a dislocation model of SCI.

Stem Cells Therapy for Spinal Cord Injury: An Overview of Clinical Trials

Spinal cord injury (SCI) is a traumatic lesion that causes disability with temporary or permanent sensory and/or motor deficits. The pharmacological approach still in use for the treatment of SCI involves the employment of corticosteroid drugs. However, SCI remains a very complex disorder that needs future studies to find effective pharmacological treatments. SCI actives a strong inflammatory response that induces a loss of neurons followed by a cascade of events that lead to further spinal cord damage. Many experimental studies demonstrate the therapeutic effect of stem cells in SCI due to their capacity to differentiate into neuronal cells and by releasing neurotrophic factors. Therefore, they appear to be a valid strategy to use in the field of regenerative medicine. The purpose of this paper is to provide an overview of clinical trials, recorded in clinical trial.gov during 2005-2019, aimed to evaluate the use of stem cell-based therapy in SCI. The results available thus far show the safety and efficacy of stem cell therapy in patients with SCI. However, future trials are needed to investigate the safety and efficacy of stem cell transplantation.

Dental mesenchymal stem cells and neuro-regeneration: a focus on spinal cord injury

Regenerative medicine is a branch of translational research that aims to reestablish irreparably damaged tissues and organs by stimulating the body's own repair mechanisms via the implantation of stem cells differentiated into specialized cell types. A rich source of adult stem cells is located inside the tooth and is represented by human dental pulp stem cells, or hDPSCs. These cells are characterized by a high proliferative rate, have self-renewal and multi-lineage differentiation properties and are often used for tissue engineering and regenerative medicine. The present review will provide an overview of hDPSCs and related features with a special focus on their potential applications in regenerative medicine of the nervous system, such as, for example, after spinal cord injury. Recent advances in the identification and characterization of dental stem cells and in dental tissue engineering strategies suggest that bioengineering approaches may successfully be used to regenerate districts of the central nervous system, previously considered irreparable.

Development of a traumatic cervical dislocation spinal cord injury model with residual compression in the rat

BACKGROUND

Preclinical spinal cord injury models do not represent the wide range of biomechanical factors seen in human injuries, such as spinal level, injury mechanism, velocity of spinal cord impact, and residual compression. These factors may be responsible for differences observed between experimental and clinical study results, especially related to the controversial issue of timing of surgical decompression.

NEW METHOD

Somatosensory Evoked Potentials were used to: a) characterize residual compression depths in a dislocation model, and b) evaluate the physiological effect of whether or not the spinal cord was decompressed following the initial injury, prior to the application of residual compression. Modifications to vertebral clamps and the development of a novel surgical frame allowed us to conduct surgical and injury procedures in a controlled manner without the risk of additional damage to the spinal cord. Behavioural outcomes were evaluated following varying dislocation displacements, in addition to the survivability of 4 h of residual compression following a traumatic injury.

RESULTS

Residual compression immediately following the initial dislocation demonstrated significantly different electrophysiological response compared to when the residual compression was delayed.

COMPARISON WITH EXISTING METHOD

There are currently no other residual compression models that utilize a dislocation injury mechanism. Many residual compression studies have demonstrated the effectiveness of early decompression, however the compression of the spinal cord is often not representative of clinical traumatic injuries. Preclinical studies typically model residual compression using a sustained force through quasi-static application, when human injuries often occur at high velocities, followed by a sustained displacement occlusion of the spinal canal.

CONCLUSIONS

This study has validated several novel procedural approaches and injury parameters, and provided critical details to implement in the development of a traumatic cervical dislocation SCI model with residual compression.

Engineering approaches to understanding mechanisms of spinal column injury leading to spinal cord injury

BACKGROUND

The mechanical interactions occurring between the spinal column and spinal cord during an injury event are complex and variable, and likely have implications for the clinical presentation and prognosis of the individual.

METHODS

The engineering approaches that have been developed to better understand spinal column and cord interactions during an injury event are discussed. These include injury models utilising human and animal cadaveric specimens, in vivo anaesthetised animals, finite element models, inanimate physical systems and combinations thereof.

FINDINGS

The paper describes the development of these modelling approaches, discusses the advantages and disadvantages of the various models, and the major outcomes that have had implications for spinal cord injury research and clinical practice.

INTERPRETATION

The contribution of these four engineering approaches to understanding the interaction between the biomechanics and biology of spinal cord injury is substantial; they have improved our understanding of the factors contributing to the spinal column disruption, the degree of spinal cord deformation or motion, and the resultant neurological deficit and imaging features. Models of the injury event are challenging to produce, but technological advances are likely to improve these models and, consequently, our understanding of the mechanical context in which the biological injury occurs.

Basic biomechanics of spinal cord injury - How injuries happen in people and how animal models have informed our understanding

The wide variability, or heterogeneity, in human spinal cord injury is due partially to biomechanical factors. This review summarizes our current knowledge surrounding the patterns of human spinal column injury and the biomechanical factors affecting injury. The biomechanics of human spinal injury is studied most frequently with human cadaveric models and the features of the two most common injury patterns, burst fracture and fracture dislocation, are outlined. The biology of spinal cord injury is typically studied with animal models and the effects of the most relevant biomechanical factors - injury mechanism, injury velocity, and residual compression, are described. Tissue damage patterns and behavioural outcomes following dislocation or distraction injury mechanisms differ from the more commonly used contusion mechanism. The velocity of injury affects spinal cord damage, principally in the white matter. Ongoing, or residual compression after the initial impact does affect spinal cord damage, but few models exist that replicate the clinical scenario. Future research should focus on the effects of these biomechanical factors in different preclinical animal models as recent data suggests that treatment outcomes may vary between models.

Axonal degeneration and demyelination following traumatic spinal cord injury: A systematic review and meta-analysis

The pathophysiology of spinal cord injury (SCI) related processes of axonal degeneration and demyelination are poorly understood. The present systematic review and meta-analysis were performed such to establish quantitative results of animal studies regarding the role of injury severity, SCI models and level of injury on the pathophysiology of axon and myelin sheath degeneration. 39 related articles were included in the analysis. The compiled data showed that the total number of axons, number of myelinated axons, myelin sheath thickness, axonal conduction velocity, and internode length steadily decreased as time elapsed from the injury (P_{for trend}<0.0001). The rate of axonal retrograde degeneration was affected by SCI model and severity of the injury. Axonal degeneration was higher in injuries of the thoracic region. The SCI model and the site of the injury also affected axonal retrograde degeneration. The number of myelinated axons in the caudal region of the injury was significantly higher than the lesion site and the rostral region. The findings of the present meta-analysis show that the pathophysiology of axons and myelin sheath differ in various phases of SCI and are affected by multiple factors related to the injury.

High-Speed Fluoroscopy to Measure Dynamic Spinal Cord Deformation in an In Vivo Rat Model

Although spinal cord deformation is thought to be a predictor of injury severity, few researchers have investigated dynamic cord deformation, in vivo, during impact. This is needed to establish correlations among impact parameters, internal cord deformation, and histological and functional outcomes. Relying on surface deformations alone may not sufficiently represent spinal cord deformation. The objective of this study was to develop a high-speed fluoroscopic method of tracking the surface and internal cord deformations of rat spinal cord during experimental cord injury. Two radio-opaque beads were injected into the cord at C5/6 in the dorsal and ventral white matter. Four additional beads were glued to the surface of the cord. Dynamic bead displacement was tracked during a dorsal impact (130 mm/sec, 1 mm depth) by high-speed radiographic imaging at 3000 FPS, laterally. The internal spinal cord beads displaced significantly more than the surface beads in the ventral direction (1.1-1.9 times) and more than most surface beads in the cranial direction (1.2-1.5 times). The dorsal beads (internal and surface) displaced more than the ventral beads during all impacts. The bead displacement pattern implies that the spinal cord undergoes complex internal and surface deformations during impact. Residual displacement of the internal beads was significantly greater than that of the surface beads in the cranial-caudal direction but not the dorsoventral direction. Finite element simulation confirmed that the additional bead mass likely had little effect on the internal cord deformations. These results support the merit of this technique for measuring in vivo spinal cord deformation.

Diffusion tensor imaging shows mechanism-specific differences in injury pattern and progression in rat models of acute spinal cord injury

We investigate the ability of diffusion tensor imaging (DTI) to distinguish between three experimental rat models of spinal cord injury mechanism - contusion, dislocation, and distraction. Ex vivo DTI scans were performed on cord specimens that were preserved at different time points of the acute injury (3 hr, 24 hr, and 7 days post-injury) across all three injury mechanisms. White matter was classified as abnormal if their DTI metric was substantially different from regional values measured from a set of uninjured controls, thus allowing generation of binary "white matter damage maps" which categorizes each pixel in the DTI image as "normal" or "damaged". Damage classification was most robust using thresholds in the longitudinal diffusivity, which supports previous studies that show that longitudinal diffusivity is the most robust DTI metric in depicting damage in SCI. Furthermore, the spatial damage patterns from all subjects in the same group were consolidated into a "damage occurrence ratio map", which illustrates an average damage shape that characterizes the injury mechanism. Our analysis has yielded a dataset which highlights the differences in injury pattern due to the initial mode of mechanical injury. For example, contusion produced an initial injury that emanated radially outward from the central canal, with subsequent damage along the caudal corticospinal tract and rostral gracile fasciculus; dislocation injuries showed a high level of involvement in the lateral and ventral white matter which became less apparent by 7 days post-injury, and distraction injuries were found to be less focal and more distributed rostrocaudally. This work represents a first step in adopting the use of the primary injury mechanism as a clinical prognostic factor in SCI, which may help to inform the trialing of existing neuroprotective treatment candidates, the development of new therapies as well as personalize the management of SCI for the individual patient.

Bioinformatics Analysis Identifies p53 as a Candidate Prognostic Biomarker for Neuropathic Pain

Neuropathic pain (NP) is a type of chronic pain that is different from the common type of pain. The mechanisms of NP are still poorly understood. Exploring the key genes and neurobiological changes in NP could provide important diagnostic and treatment tools for clinicians. GSE24982 is an mRNA-seq dataset that we downloaded from the Gene Expression Omnibus database to identify key genes in NP. Differentially expressed genes (DEGs) were identified using the BRB-ArrayTools software and R. Functional and pathway enrichment analyses of the DEGs were performed using Metascape. A protein–protein interaction network was created and visualized using Cytoscape. A total of 123 upregulated DEGs were obtained. Among these genes, p53 was the node with the highest degree; hence, we validated it experimentally using a chronic constriction injury mouse model. Our results showed that overexpression of the p53 gene, and the subsequent increase in caspase-3 expression, in dorsal root ganglion neurons led to increased apoptotic changes in these neurons. p53 may therefore be partly responsible for the development of chronic constriction injury-induced NP.

Radiography used to measure internal spinal cord deformation in an in vivo rat model

Little is known about the internal mechanics of the in vivo spinal cord during injury. The objective of this study was to develop a method of tracking internal and surface deformation of in vivo rat spinal cord during compression using radiography. Since neural tissue is radio-translucent, radio-opaque markers were injected into the spinal cord. Two tantalum beads (260 µm) were injected into the cord (dorsal and ventral) at C5 of nine anesthetized rats. Four beads were glued to the lateral surface of the cord, caudal and cranial to the injection site. A compression plate was displaced 0.5 mm, 2 mm, and 3 mm into the spinal cord and lateral X-ray images were taken before, during, and after each compression for measuring bead displacements. Potential bead migration was monitored for by comparing displacements of the internal and glued surface beads. Dorsal beads moved significantly more than ventral beads with a range in averages of 0.57-0.71 mm and 0.31-0.35 mm respectively. Bead displacements during 0.5 mm compressions were significantly lower than 2 mm and 3 mm compressions. There was no statistically significant migration of the internal beads. The results indicate the merit of this technique for measuring in vivo spinal cord deformation. The pattern of bead displacements illustrates the complex internal and surface deformations of the spinal cord during transverse compression. This information is needed for validating physical and finite element spinal cord surrogates and to define relationships between loading parameters, internal cord deformation, and biological and functional outcomes.

Repeatability of a Dislocation Spinal Cord Injury Model in a Rat-A High-Speed Biomechanical Analysis

Dislocation is the most common, and severe, spinal cord injury (SCI) mechanism in humans, yet there are few preclinical models. While dislocation in the rat model has been shown to produce unique outcomes, like other closed column models it exhibits higher outcome variability. Refinement of the dislocation model will enhance the testing of neuroprotective strategies, further biomechanical understanding, and guide therapeutic decisions. The overall objective of this study is to improve biomechanical repeatability of a dislocation SCI model in the rat, through the following specific aims: (i) design new injury clamps that pivot and self-align to the vertebrae; (ii) measure intervertebral kinematics during injury using the existing and redesigned clamps; and (iii) compare relative motion at the vertebrae-clamp interface to determine which clamps provide the most rigid connection. Novel clamps that pivot and self-align were developed based on the quantitative rat vertebral anatomy. A dislocation injury was produced in 34 rats at C4/C5 using either the existing or redesigned clamps, and a high-speed X-ray device recorded the kinematics. Relative motion between the caudal clamp and C5 was significantly greater in the existing clamps compared to the redesigned clamps in dorsoventral translation and sagittal rotation. This study demonstrates that relative motions can be of magnitudes that likely affect injury outcomes. We recommend such biomechanical analyses be applied to other SCI models when repeatability is an issue. For this dislocation model, the results show the importance of using clamps that pivot and self-align to the vertebrae.

Effect of VEGF on Inflammatory Regulation, Neural Survival, and Functional Improvement in Rats following a Complete Spinal Cord Transection

After complete transection of the thoracic spinal segment, neonatal rats exhibit spontaneous locomotor recovery of hindlimbs, but this recovery is not found in adult rats after similar injury. The potential mechanism related to the difference in recovery of neonatal and adult rats remains unknown. In this study, 342 animals were analyzed. The vascular endothelial growth factor (VEGF) level in spinal segments below injury sites was significantly higher in postnatal day 1 rats (P1) compared with 28-day-old adult rats (P28) following a complete T9 transection. VEGF administration in P28 rats with T9 transection significantly improved the functional recovery; by contrast, treatment with VEGF receptor inhibitors in P1 rats with T9 transection slowed down the spontaneous functional recovery. Results showed more neurons reduced in the lumbar spinal cord and worse local neural network reorganization below injury sites in P28 rats than those in P1 rats. Transynaptic tracing with pseudorabies virus and double immunofluorescence analysis indicated that VEGF treatment in P28 rats alleviated the reduced number of neurons and improved their network reorganization. VEGF inhibition in neonates resulted in high neuronal death rate and deteriorated network reorganization. In in vivo studies, T9 transection induced less increase in the number of microglia in the spinal cord in P1 animals than P28 animals. VEGF treatment reduced the increase in microglial cells in P28 animals. VEGF administration in cultured spinal motoneurons prevented lipopolysaccharide (LPS)-induced neuronal death and facilitated neurite growth. Western blots of the samples of lumbar spinal cord after spinal transection and cultured spinal motoneurons showed a lower level of Erk1/2 phosphorylation after the injury or LPS induction compared with that in the control. The phosphorylation level increased after VEGF treatment. In conclusion, VEGF is a critical mediator involved in functional recovery after spinal transection and can be considered a potential target for clinical therapy.

The pathologic mechanisms underlying lumbar distraction spinal cord injury in rabbits

BACKGROUND CONTEXT

A reliable experimental rabbit model of distraction spinal cord injury (SCI) was established to successfully simulate gradable and replicable distraction SCI. However, further research is needed to elucidate the pathologic mechanisms underlying distraction SCI.

PURPOSE

The aim of this study was to investigate the pathologic mechanisms underlying lumbar distraction SCI in rabbits.

STUDY DESIGN

This is an animal laboratory study.

METHODS

Using a self-designed spine distractor, the experimental animals were divided into a control group and 10%, 20%, and 30% distraction groups. Pathologic changes to the spinal cord microvessels in the early stage of distraction SCI were identified by perfusion of the spinal cord vasculature with ink, production of transparent specimens, observation by light microscopy, and observation of corrosion casts of the spinal cord microvascular architecture by scanning electron microscopy. Malondialdehyde (MDA) and superoxide dismutase (SOD) concentrations in the injured spinal cord tissue were measured after 8 hours.

RESULTS

With an increasing degree and duration of distraction, the spinal cord microvessels were only partially filled and had the appearance of spasm until rupture and hemorrhage were observed. The MDA concentration increased and the SOD concentration decreased in the spinal cord tissue.

CONCLUSIONS

Changes to the internal and external spinal cord vessels led to spinal cord ischemia, which is a primary pathologic mechanism of distraction SCI. Lipid peroxidation mediated by free radicals took part in secondary pathologic damage of distraction SCI.

The combined strategy of mesenchymal stem cells and tissue-engineered scaffolds for spinal cord injury regeneration

Spinal cord injury (SCI) is a traumatic lesion that can result in the loss of motor or sensory neurons. Stem cell (SC)-based therapies have been demonstrated to promote neuronal regeneration following SCI, by releasing a range of trophic factors that support endogenous repair or by differentiating into neurons, or glial cells in order to replace the damaged cells. However, numerous limitations remain for therapies based on SC transplantion alone, including a low rate of survival/engraftment. Nevertheless, scaffolds are 3-dimentional substrates that have revealed to support cell survival, proliferation and differentiation in vivo, by mimicking a more favorable endogenous microenvironment. A multidisciplinary approach, which combines engineered scaffolds with SCs has been proposed as a promising strategy for encouraging spinal cord regeneration. The present review has focused on the regenerative potential of mesenchymal SCs isolated from different sources and combined with various scaffold types, in preclinical and clinical SCI studies.

Nanofiber Scaffolds as Drug Delivery Systems to Bridge Spinal Cord Injury

The complex pathophysiology of spinal cord injury (SCI) may explain the current lack of an effective therapeutic approach for the regeneration of damaged neuronal cells and the recovery of motor functions. A primary mechanical injury in the spinal cord triggers a cascade of secondary events, which are involved in SCI instauration and progression. The aim of the present review is to provide an overview of the therapeutic neuro-protective and neuro-regenerative approaches, which involve the use of nanofibers as local drug delivery systems. Drugs released by nanofibers aim at preventing the cascade of secondary damage (neuro-protection), whereas nanofibrous structures are intended to re-establish neuronal connectivity through axonal sprouting (neuro-regeneration) promotion, in order to achieve a rapid functional recovery of spinal cord.

Compression Decreases Anatomical and Functional Recovery and Alters Inflammation after Contusive Spinal Cord Injury

Experimental models of spinal cord injury (SCI) typically utilize contusion or compression injuries. Clinically, however, SCI is heterogeneous and the primary injury mode may affect secondary injury progression and neuroprotective therapeutic efficacy. Specifically, immunomodulatory agents are of therapeutic interest because the activation state of SCI macrophages may facilitate pathology but also improve repair. It is unknown currently how the primary injury biomechanics affect macrophage activation. Therefore, to determine the effects of compression subsequent to spinal contusion, we examined recovery, secondary injury, and macrophage activation in C57/BL6 mice after SCI with or without a 20 sec compression at two contusion impact forces (50 and 75 kdyn). We observed that regardless of the initial impact force, compression increased tissue damage and worsened functional recovery. Interestingly, compression-dependent damage is not evident until one week after SCI. Further, compression limits functional recovery to the first two weeks post-SCI; in the absence of compression, mice receiving contusion SCI recover for four weeks. To determine whether the recovery plateau is indicative of compression-specific inflammatory responses, we examined macrophage activation with immunohistochemical markers of purportedly pathological (CD86 and macrophage receptor with collagenous structure [MARCO]) and reparative macrophages (arginase [Arg1] and CD206). We detected significant increases in macrophages expression of MARCO and decreases in macrophage Arg1 expression with compression, suggesting a biomechanical-dependent shift in SCI macrophage activation. Collectively, compression-induced alterations in tissue and functional recovery and inflammation highlight the need to consider the primary SCI biomechanics in the design and clinical implementation of immunomodulatory therapies.

Spinal cord injury effectively ameliorated by neuroprotective effects of rosmarinic acid

OBJECTIVE

Pathophysiology of spinal cord injury (SCI) causes primary and secondary effects leading to loss of neuronal function. The aim of the present study was to investigate the role of rosmarinic acid (RA) in protection against SCI.

METHODS

The experimental study was carried out in male wistar rats categorized into three groups. Group I - sham operated rats; Group II - SCI; Group III - SCI followed by RA treatment (10 mg/kg). The spinal tissues after treatment schedule were analyzed for oxidative stress status through determination of reactive oxygen species (ROS), lipid peroxidation, protein damage (carbonyl and sulfhydryl contents), and antioxidant enzyme activities. The expression of oxidative stress factors NF-κB and Nrf-2 was determined by Western blot analysis. Further pro-inflammatory cytokines (TNF-α, IL-6, MCP-1, and IL-1β) were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The results show that treatment with RA significantly enhances the antioxidant status and decrease the oxidative stress in wistar rats post-SCI. RA effectively ameliorated inflammatory mechanisms by downregulation of NF-κB and pro-inflammatory cytokines post-SCI.

CONCLUSION

The study demonstrates for the first time on the role of RA in protecting the spinal cord from injury and demonstrates its neuroprotection in wistar rats.

The Expression of IGFBP6 after Spinal Cord Injury: Implications for Neuronal Apoptosis

IGFBP6, a member of the insulin-like growth factor-binding proteins family that contains six high affinity IGFBPs, modulates insulin-like growth factor (IGF) activity and also showed an independent effect of IGF, such as growth inhibition and apoptosis. However, the role of IGFBP6 in spinal cord injury (SCI) remains largely elusive. In this study, we have performed an acute SCI model in adult rats and investigated the dynamic changes of IGFBP6 expression in the spinal cord. Our results showed that IGFBP6 was upregulated significantly after SCI, which was paralleled with the levels of apoptotic proteins p53 and active caspase-3. Immunofluorescent labeling showed that IGFBP6 was co-localizated with active caspase-3 and p53 in neurons. To further investigate the function of IGFBP6, an apoptosis model was established in primary neuronal cells. When IGFBP6 was knocked down by specific short interfering RNA (siRNA), the protein levels of active caspase-3 and Bax as well as the number of apoptotic primary neurons were significantly decreased in our study. Taken together, our findings suggest that the change of IGFBP6 protein expression plays a key role in neuronal apoptosis after SCI.

Cornel Iridoid Glycoside Improves Locomotor Impairment and Decreases Spinal Cord Damage in Rats

Purpose. This study was to investigate the effects of cornel iridoid glycoside (CIG) on spinal cord injury (SCI) in rats. Methods. The thoracic cord (at T9) of rats was injured by clip compression for 30 sec. Locomotor function was assessed using the Basso, Beattie, and Bresnahan (BBB) rating scale. Neuroanatomic stereological parameters as well as Nogo-A, p75 neurotrophin receptor (p75NTR), and ROCKII expression were measured by histological processing, immunohistochemistry, and stereological analyses. The axons passing through the lesion site were detected by BDA tracing. Results. Intragastric administration of CIG (60 and 180 mg/kg) improved the locomotor impairment at 10, 17, 24, and 31 days post-injury (dpi) compared with untreated SCI model rats. CIG treatment decreased the volume of the lesion epicenter (LEp) and increased the volume of spared tissue and the number of surviving neurons in the injured spinal cord at 31 dpi. CIG promoted the growth of BDA-positive axons and their passage through the lesion site and decreased the expression of Nogo-A, p75NTR, and ROCKII both in and around the LEp. Conclusion. CIG improved the locomotor impairment, decreased tissue damage, and downregulated the myelin-associated inhibition signaling pathway in SCI rats. The results suggest that CIG may be beneficial for SCI therapy.

Differential Histopathological and Behavioral Outcomes Eight Weeks after Rat Spinal Cord Injury by Contusion, Dislocation, and Distraction Mechanisms

The objective of this study was to compare the long-term histological and behavioral outcomes after spinal cord injury (SCI) induced by one of three distinct biomechanical mechanisms: dislocation, contusion, and distraction. Thirty male Sprague-Dawley rats were randomized to incur a traumatic cervical SCI by one of these three clinically relevant mechanisms. The injured cervical spines were surgically stabilized, and motor function was assessed for the following 8 weeks. The spinal cords were then harvested for histologic analysis. Quantification of white matter sparing using Luxol fast blue staining revealed that dislocation injury caused the greatest overall loss of white matter, both laterally and along the rostrocaudal axis of the injured cord. Distraction caused enlarged extracellular spaces and structural alteration in the white matter but spared the most myelinated axons overall. Contusion caused the most severe loss of myelinated axons in the dorsal white matter. Immunohistochemistry for the neuronal marker NeuN combined with Fluoro Nissl revealed that the dislocation mechanism resulted in the greatest neuronal cell losses in both the ventral and dorsal horns. After the distraction injury mechanism, animals displayed no recovery of grip strength over time, in contrast to the animals subjected to contusion or dislocation injuries. After the dislocation injury mechanism, animals displayed no improvement in the grooming test, in contrast to the animals subjected to contusion or distraction injuries. These data indicate that different SCI mechanisms result in distinct patterns of histopathology and behavioral recovery. Understanding this heterogeneity may be important for the future development of therapeutic interventions that target specific neuropathology after SCI.

Hyaluronic acid scaffold has a neuroprotective effect in hemisection spinal cord injury

OBJECTIVE

Spinal cord injury occurs in 2 phases. The initial trauma is followed by inflammation that leads to fibrous scar tissue, glial scarring, and cavity formation. Scarring causes further axon death around and above the injury. A reduction in secondary injury could lead to functional improvement. In this study, hyaluronic acid (HA) hydrogels were implanted into the gap formed in the hemisected spinal cord of Sprague-Dawley rats in an attempt to attenuate damage and regenerate tissue.

METHODS

A T-10 hemisection spinal cord injury was created in adult male Sprague-Dawley rats; the rats were assigned to a sham, control (phosphate-buffered saline), or HA hydrogel–treated group. One cohort of 23 animals was followed for 12 weeks and underwent weekly behavioral assessments. At 12 weeks, retrograde tracing was performed by injecting Fluoro-Gold in the left L-2 gray matter. At 14 weeks, the animals were killed. The volume of the lesion and the number of cells labeled from retrograde tracing were calculated. Animals in a separate cohort were killed at 8 or 16 weeks and perfused for immunohistochemical analysis and transmission electron microscopy. Samples were stained using H & E, neurofilament stain (neurons and axons), silver stain (disrupted axons), glial fibrillary acidic protein stain (astrocytes), and Iba1 stain (mononuclear cells).

RESULTS

The lesions were significantly smaller in size and there were more retrograde-labeled cells in the red nuclei of the HA hydrogel–treated rats than in those of the controls; however, the behavioral assessments revealed no differences between the groups. The immunohistochemical analyses revealed decreased fibrous scarring and increased retention of organized intact axonal tissue in the HA hydrogel–treated group. There was a decreased presence of inflammatory cells in the HA hydrogel–treated group. No axonal or neuronal regeneration was observed.

CONCLUSIONS

The results of these experiments show that HA hydrogel had a neuroprotective effect on the spinal cord by decreasing the magnitude of secondary injury after a lacerating spinal cord injury. Although regeneration and behavioral improvement were not observed, the reduction in disorganized scar tissue and the retention of neurons near and above the lesion are important for future regenerative efforts. In addition, this gel would be useful as the base substrate in the development of a more complex scaffold.

Mechanical Design and Analysis of a Unilateral Cervical Spinal Cord Contusion Injury Model in Non-Human Primates

Non-human primate (NHP) models of spinal cord injury better reflect human injury and provide a better foundation to evaluate potential treatments and functional outcomes. We combined finite element (FE) and surrogate models with impact data derived from in vivo experiments to define the impact mechanics needed to generate a moderate severity unilateral cervical contusion injury in NHPs (Macaca mulatta). Three independent variables (impactor displacement, alignment, and pre-load) were examined to determine their effects on tissue level stresses and strains. Mechanical measures of peak force, peak displacement, peak energy, and tissue stiffness were analyzed as potential determinants of injury severity. Data generated from FE simulations predicted a lateral shift of the spinal cord at high levels of compression (>64%) during impact. Submillimeter changes in mediolateral impactor position over the midline increased peak impact forces (>50%). Surrogate cords established a 0.5 N pre-load protocol for positioning the impactor tip onto the dural surface to define a consistent dorsoventral baseline position before impact, which corresponded with cerebrospinal fluid displacement and entrapment of the spinal cord against the vertebral canal. Based on our simulations, impactor alignment and pre-load were strong contributors to the variable mechanical and functional outcomes observed in in vivo experiments. Peak displacement of 4 mm after a 0.5N pre-load aligned 0.5-1.0 mm over the midline should result in a moderate severity injury; however, the observed peak force and calculated peak energy and tissue stiffness are required to properly characterize the severity and variability of in vivo NHP contusion injuries.

Inflammogenesis of Secondary Spinal Cord Injury

Spinal cord injury (SCI) and spinal infarction lead to neurological complications and eventually to paraplegia or quadriplegia. These extremely debilitating conditions are major contributors to morbidity. Our understanding of SCI has certainly increased during the last decade, but remains far from clear. SCI consists of two defined phases: the initial impact causes primary injury, which is followed by a prolonged secondary injury consisting of evolving sub-phases that may last for years. The underlying pathophysiological mechanisms driving this condition are complex. Derangement of the vasculature is a notable feature of the pathology of SCI. In particular, an important component of SCI is the ischemia-reperfusion injury (IRI) that leads to endothelial dysfunction and changes in vascular permeability. Indeed, together with endothelial cell damage and failure in homeostasis, ischemia reperfusion injury triggers full-blown inflammatory cascades arising from activation of residential innate immune cells (microglia and astrocytes) and infiltrating leukocytes (neutrophils and macrophages). These inflammatory cells release neurotoxins (proinflammatory cytokines and chemokines, free radicals, excitotoxic amino acids, nitric oxide (NO)), all of which partake in axonal and neuronal deficit. Therefore, our review considers the recent advances in SCI mechanisms, whereby it becomes clear that SCI is a heterogeneous condition. Hence, this leads towards evidence of a restorative approach based on monotherapy with multiple targets or combinatorial treatment. Moreover, from evaluation of the existing literature, it appears that there is an urgent requirement for multi-centered, randomized trials for a large patient population. These clinical studies would offer an opportunity in stratifying SCI patients at high risk and selecting appropriate, optimal therapeutic regimens for personalized medicine.

Drug delivery, cell-based therapies, and tissue engineering approaches for spinal cord injury

Spinal cord injury (SCI) results in devastating neurological and pathological consequences, causing major dysfunction to the motor, sensory, and autonomic systems. The primary traumatic injury to the spinal cord triggers a cascade of acute and chronic degenerative events, leading to further secondary injury. Many therapeutic strategies have been developed to potentially intervene in these progressive neurodegenerative events and minimize secondary damage to the spinal cord. Additionally, significant efforts have been directed toward regenerative therapies that may facilitate neuronal repair and establish connectivity across the injury site. Despite the promise that these approaches have shown in preclinical animal models of SCI, challenges with respect to successful clinical translation still remain. The factors that could have contributed to failure include important biologic and physiologic differences between the preclinical models and the human condition, study designs that do not mirror clinical reality, discrepancies in dosing and the timing of therapeutic interventions, and dose-limiting toxicity. With a better understanding of the pathobiology of events following acute SCI, developing integrated approaches aimed at preventing secondary damage and also facilitating neuroregenerative recovery is possible and hopefully will lead to effective treatments for this devastating injury. The focus of this review is to highlight the progress that has been made in drug therapies and delivery systems, and also cell-based and tissue engineering approaches for SCI.

A novel closed-body model of spinal cord injury caused by high-pressure air blasts produces extensive axonal injury and motor impairments

Diffuse axonal injury is thought to be the basis of the functional impairments stemming from mild traumatic brain injury. To examine how axons are damaged by traumatic events, such as motor vehicle accidents, falls, sports activities, or explosive blasts, we have taken advantage of the spinal cord with its extensive white matter tracts. We developed a closed-body model of spinal cord injury in mice whereby high-pressure air blasts targeted to lower thoracic vertebral levels produce tensile, compressive, and shear forces within the parenchyma of the spinal cord and thereby cause extensive axonal injury. Markers of cytoskeletal integrity showed that spinal cord axons exhibited three distinct pathologies: microtubule breakage, neurofilament compaction, and calpain-mediated spectrin breakdown. The dorsally situated axons of the corticospinal tract primarily exhibited microtubule breakage, whereas all three pathologies were common in the lateral and ventral white matter. Individual axons typically demonstrated only one of the three pathologies during the first 24h after blast injury, suggesting that the different perturbations are initiated independently of one another. For the first few days after blast, neurofilament compaction was frequently accompanied by autophagy, and subsequent to that, by the fragmentation of degenerating axons. TuJ1 immunolabeling and mice with YFP-reporter labeling each revealed more extensive microtubule breakage than did βAPP immunolabeling, raising doubts about the sensitivity of this standard approach for assessing axonal injury. Although motor deficits were mild and largely transient, some aspects of motor function gradually worsened over several weeks, suggesting that a low level of axonal degeneration continued past the initial wave. Our model can help provide further insight into how to intervene in the processes by which initial axonal damage culminates in axonal degeneration, to improve outcomes after traumatic injury. Importantly, our findings of extensive axonal injury also caution that repeated trauma is likely to have cumulative adverse consequences for both brain and spinal cord.

Electroacupuncture in the repair of spinal cord injury: inhibiting the Notch signaling pathway and promoting neural stem cell proliferation

Electroacupuncture for the treatment of spinal cord injury has a good clinical curative effect, but the underlying mechanism is unclear. In our experiments, the spinal cord of adult Sprague-Dawley rats was clamped for 60 seconds. Dazhui (GV14) and Mingmen (GV4) acupoints of rats were subjected to electroacupuncture. Enzyme-linked immunosorbent assay revealed that the expression of serum inflammatory factors was apparently downregulated in rat models of spinal cord injury after electroacupuncture. Hematoxylin-eosin staining and immunohistochemistry results demonstrated that electroacupuncture contributed to the proliferation of neural stem cells in rat injured spinal cord, and suppressed their differentiation into astrocytes. Real-time quantitative PCR and western blot assays showed that electroacupuncture inhibited activation of the Notch signaling pathway induced by spinal cord injury. These findings indicate that electroacupuncture repaired the injured spinal cord by suppressing the Notch signaling pathway and promoting the proliferation of endogenous neural stem cells.