Delayed myelopathy induced by chronic compression in the rat spinal cord

Development of a mouse model of chronic ventral spinal cord compression: Neurobehavioral, radiological, and pathological changes

Objectives

The main objective of this study was to establish a mouse model of spinal ligament ossification to simulate the chronic spinal cord compression observed in patients with ossification of the posterior longitudinal ligament (OPLL). The study also aimed to examine the mice's neurobiological, radiological, and pathological changes.

Methods

In the previous study, a genetically modified mouse strain was created using Crispr-Cas9 technology, namely, Enpp1 flox/flox /EIIa-Cre (C57/B6 background), to establish the OPLL model. Wild-type (WT) mice without compression were used as controls. Functional deficits were evaluated through motor score assessment, inclined plate testing, and gait analysis. The extent of compression was determined using CT imaging. Hematoxylin and eosin staining, luxol fast blue staining, TUNEL assay, immunofluorescence staining, qPCR, and Western blotting were performed to evaluate levels of apoptosis, inflammation, vascularization, and demyelination in the study.

Results

The results demonstrated a gradual deterioration of compression in the Enpp1 flox/flox /EIIa-Cre mice group as they aged. The progression rate was more rapid between 12 and 20 weeks, followed by a gradual stabilization between 20 and 28 weeks. The scores for spinal cord function and strength, assessed using the Basso Mouse Scale and inclined plate test, showed a significant decline. Gait analysis revealed a noticeable reduction in fore and hind stride lengths, stride width, and toe spread. Chronic spinal cord compression resulted in neuronal damage and activated astrocytes and microglia in the gray matter and anterior horn. Progressive posterior cervical compression impeded blood supply, leading to inflammation and Fas-mediated neuronal apoptosis. The activation of Bcl2 and Caspase 3 was associated with the development of progressive neurological deficits (p < 0.05).

Conclusions

The study presents a validated model of chronic spinal cord compression, enabling researchers to explore clinically relevant therapeutic approaches for OPLL.

Differences in the expression of myelopathy in a rat model of chronic spinal cord compression

CONTEXT/OBJECTIVE

The degree of spinal cord compression does not always parallel neurological symptoms. We considered that some compensatory neuroprotective mechanism underlies the expression of this neurological phenotype. Oxygen-regulated-protein 150 (ORP150) is neuroprotective and expressed in neurons in response to neuronal ischemia. We sought to elucidate whether ORP150 expression is associated with the severity and variation of neurological recovery in our rat model of chronic spinal cord compression.

METHODS

We made a rat model of chronic spinal cord compression inserting an expandable water-absorbing polyurethane sheet. A neurological behavioral assessment of the severity of paralysis was performed for 10 weeks postoperatively. The rat model was defined as two groups: a myelopathy group with decreased locomotor function and an asymptomatic group. At 10 weeks postoperatively, the spinal cord of the cervical segment was resected for histology and qPCR.

RESULTS

Slowly progressive paralysis appeared at 5-10 weeks postoperatively in 53% of the rats with spinal cord compression. The asymptomatic group had no histological changes indicative of myelopathy. Histology and qPCR showed increased expression of ORP150 in the asymptomatic group, but the ratio of ORP150-positive neuron in the two groups was not significantly different.

CONCLUSION

The expression of ORP150 in neurons associated with spinal cord compression suggested that the spinal cord was under ischemic stress due to compression, but relation to the development of myelopathy was unclear. The results suggested that some other compensatory mechanisms may exist in response to spinal cord compression in asymptomatic rats.

Impaired communication at the neuromotor axis during Degenerative Cervical Myelopathy

Degenerative Cervical Myelopathy (DCM) is a progressive neurological condition characterized by structural alterations in the cervical spine, resulting in compression of the spinal cord. While clinical manifestations of DCM are well-documented, numerous unanswered questions persist at the molecular and cellular levels. In this study, we sought to investigate the neuromotor axis during DCM. We use a clinically relevant mouse model, where after 3 months of DCM induction, the sensorimotor tests revealed a significant reduction in both locomotor activity and muscle strength compared to the control group. Immunohistochemical analyses showed alterations in the gross anatomy of the cervical spinal cord segment after DCM. These changes were concomitant with the loss of motoneurons and a decrease in the number of excitatory synaptic inputs within the spinal cord. Additionally, the DCM group exhibited a reduction in the endplate surface, which correlated with diminished presynaptic axon endings in the supraspinous muscles. Furthermore, the biceps brachii (BB) muscle exhibited signs of atrophy and impaired regenerative capacity, which inversely correlated with the transversal area of remnants of muscle fibers. Additionally, metabolic assessments in BB muscle indicated an increased proportion of oxidative skeletal muscle fibers. In line with the link between neuromotor disorders and gut alterations, DCM mice displayed smaller mucin granules in the mucosa layer without damage to the epithelial barrier in the colon. Notably, a shift in the abundance of microbiota phylum profiles reveals an elevated Firmicutes-to-Bacteroidetes ratio-a consistent hallmark of dysbiosis that correlates with alterations in gut microbiota-derived metabolites. Additionally, treatment with short-chain fatty acids stimulated the differentiation of the motoneuron-like NSC34 cell line. These findings shed light on the multifaceted nature of DCM, resembling a synaptopathy that disrupts cellular communication within the neuromotor axis while concurrently exerting influence on other systems. Notably, the colon emerges as a focal point, experiencing substantial perturbations in both mucosal barrier integrity and the delicate balance of intestinal microbiota.

Blood-spinal cord barrier disruption in degenerative cervical myelopathy

Degenerative cervical myelopathy (DCM) is the most prevalent cause of spinal cord dysfunction in the aging population. Significant neurological deficits may result from a delayed diagnosis as well as inadequate neurological recovery following surgical decompression. Here, we review the pathophysiology of DCM with an emphasis on how blood-spinal cord barrier (BSCB) disruption is a critical yet neglected pathological feature affecting prognosis. In patients suffering from DCM, compromise of the BSCB is evidenced by elevated cerebrospinal fluid (CSF) to serum protein ratios and abnormal contrast-enhancement upon magnetic resonance imaging (MRI). In animal model correlates, there is histological evidence of increased extravasation of tissue dyes and serum contents, and pathological changes to the neurovascular unit. BSCB dysfunction is the likely culprit for ischemia-reperfusion injury following surgical decompression, which can result in devastating neurological sequelae. As there are currently no therapeutic approaches specifically targeting BSCB reconstitution, we conclude the review by discussing potential interventions harnessed for this purpose.

Spinal Canal and Spinal Cord in Rat Continue to Grow Even after Sexual Maturation: Anatomical Study and Molecular Proposition

Although rodents have been widely used for experimental models of spinal cord diseases, the details of the growth curves of their spinal canal and spinal cord, as well as the molecular mechanism of the growth of adult rat spinal cords remain unavailable. They are particularly important when conducting the experiments of cervical spondylotic myelopathy (CSM), since the disease condition depends on the size of the spinal canal and the spinal cord. Thus, the purposes of the present study were to obtain accurate growth curves for the spinal canal and spinal cord in rats; to define the appropriate age in weeks for their use as a CSM model; and to propose a molecular mechanism of the growth of the adult spinal cord in rats. CT myelography was performed on Lewis rats from 4 weeks to 40 weeks of age. The vertical growth of the spinal canal at C5 reached a plateau after 20 and 12 weeks, and at T8 after 20 and 16 weeks, in males and females, respectively. The vertical growth of the C5 and T8 spinal cord reached a plateau after 24 weeks in both sexes. The vertical space available for the cord (SAC) of C5 and T8 did not significantly change after 8 weeks in either sex. Western blot analyses showed that VEGFA, FGF2, and BDNF were highly expressed in the cervical spinal cords of 4-week-old rats, and that the expression of these growth factors declined as rats grew. These findings indicate that the spinal canal and the spinal cord in rats continue to grow even after sexual maturation and that rats need to be at least 8 weeks of age for use in experimental models of CSM. The present study, in conjunction with recent evidence, proposes the hypothetical model that the growth of rat spinal cord after the postnatal period is mediated at least in part by differentiation of neural progenitor cells and that their differentiation potency is maintained by VEGFA, FGF2, and BDNF.

Prognostic effect of increased postoperative MRI T2WI high signal intensity in degenerative cervical myelopathy

BACKGROUND CONTEXT

High cord signals (HCS) are common in patients undergoing surgery for degenerative cervical myelopathy (DCM). Few studies have investigated the prognostic effects of postoperative HCS changes.

PURPOSE

To investigate whether different changes in the postoperative magnetic resonance imaging (MRI) T2-weighted images (T2WIs) signal intensity ratio (SIR) is related to patient outcomes, predictors of unsatisfactory recovery, and the factors associated with changes in postoperative SIR.

STUDY DESIGN

A retrospective chart review at a single institution.

PATIENT SAMPLE

The study population included all consecutive patients who showed HCS in preoperative MRI T2WIs and underwent double-door laminoplasty for DCM from December 2017 to December 2020.

OUTCOME MEASURES

Patient self-reported measures included the Japanese Orthopedic Association (JOA) score, 36-Item Short Form Survey (SF-36) physical component score, and SF-36 mental component score. Imaging measures included SIR, length of HCS, and canal narrowing ratio (CNR).

METHODS

We reviewed patient records and analyzed the statistical associations of MRI T2WI measures with the JOA score, SF-36 physical, and mental component scores.

RESULTS

Fifty-three patients were categorized into three groups based on the postoperative HCS changes, identified from MRI T2WI before and after surgery: reduced (Group A, N=26); unchanged (Group B, N=12); and increased (Group C, N=15). The neurological recovery rates 12 months after surgery were 67.72%±17.45% in Group A, 51.53%±16.00% in Group B, and 13.35%±21.35% in Group C (p<.001). Significant differences across the three groups were found in symptom duration, postoperative SIR and length of HCS, pre- and postoperative CNR, recovery rate, JOA, SF-36 scores, with patients in Group C having the worst outcomes. Longer DCM symptom duration, greater preoperative CNR, and increased postoperative HCS were prognostic factors for a recovery rate<50%. Preoperative CNR, with an optimal threshold of 57.303%, was an independent risk factor for increased postoperative HCS.

CONCLUSIONS

Less than one-third of DCM patients with preoperative HCS exhibited an increase in HCS after double-door laminoplasty and reported worse outcomes at the 12-month follow-up when compared to patients with decreased or unchanged postoperative HCS.

Animal models of compression spinal cord injury

Compression spinal cord injuries are a common cause of morbidity in people who experience a spinal cord injury (SCI). Either as a by-product of a traumatic injury or due to nontraumatic conditions such as cervical myelitis, compression injuries are growing in prevalence clinically and many attempts of animal replication have been described within the literature. These models, however, often focus on the traumatic side of injury or mimic short-term injuries that are not representative of the majority of compression SCI. Of this, nontraumatic spinal cord injuries are severely understudied and have an increased prevalence in elderly populations, adults, and children. Therefore, there is a need to critically evaluate the current animal models of compression SCI and their suitability as a method for clinically relevant data that can help reduce morbidity and mortality of SCI. In this review, we reviewed the established and emerging methods of animal models of compression SCI. These models are the clip, balloon, solid spacer, expanding polymer, remote, weight drop, calibrated forceps, screw, and strap methods. These methods showed that there is a large reliance on the use of laminectomy to induce injury. Furthermore, the age range of many studies does not reflect the elderly and young populations that commonly suffer from compression injuries. It is therefore important to have techniques and methods that are able to minimize secondary effects of the surgeries, and are representative of the clinical cases seen so that treatments and interventions can be developed that are specific.

Early decompression promotes motor recovery after cervical spinal cord injury in rats with chronic cervical spinal cord compression

The number of elderly patients with spinal cord injury without radiographic abnormalities (SCIWORA) has been increasing in recent years and common of most cervical spinal cord injuries. Basic research has shown the effectiveness of early decompression after spinal cord injury on the spinal cord without stenosis; no studies have reported the efficacy of decompression in models with spinal cord compressive lesions. The purpose of this study was to evaluate the effects of decompression surgery after acute spinal cord injury in rats with chronic spinal cord compressive lesions, mimicking SCIWORA. A water-absorbent polymer sheet (Aquaprene DX, Sanyo Chemical Industries) was inserted dorsally into the 4–5th cervical sublaminar space in 8-week-old Sprague Dawley rats to create a rat model with a chronic spinal compressive lesion. At the age of 16 weeks, 30 mildly myelopathic or asymptomatic rats with a Basso, Beattie, and Bresnahan score (BBB score) of 19 or higher were subjected to spinal cord compression injuries. The rats were divided into three groups: an immediate decompression group (decompress immediately after injury), a sub-acute decompression group (decompress 1 week after injury), and a non-decompression group. Behavioral and histological evaluations were performed 4 weeks after the injury. At 20 weeks of age, the BBB score and FLS (Forelimb Locomotor Scale) of both the immediate and the sub-acute decompression groups were significantly higher than those of the non-decompression group. There was no significant difference between the immediate decompression group and the sub-acute decompression group. TUNEL (transferase-mediated dUTP nick end labeling) staining showed significantly fewer positive cells in both decompression groups compared to the non-decompression group. LFB (Luxol fast blue) staining showed significantly more demyelination, and GAP-43 (growth associated protein-43) staining tended to show fewer positive cells in the non-decompression group. Decompression surgery in the acute or sub-acute phase of injury is effective after mild spinal cord injury in rats with chronic compressive lesions. There was no significant difference between the immediate decompression and sub-acute decompression groups.

A sheep model of chronic cervical compressive myelopathy via an implantable wireless compression device

PURPOSE

This study aimed to establish an animal model in which we can precisely displace the spinal cord and therefore mimic the chronic spinal compression of cervical spondylotic myelopathy.

METHODS

In vivo intervertebral compression devices (IVCDs) connected with subcutaneous control modules (SCCMs) were implanted into the C2-3 intervertebral disk spaces of sheep and connected by Bluetooth to an in vitro control system. Sixteen sheep were divided into four groups: (Group A) control; (Group B) 10-week progressive compression, then held; (Group C) 20-week progressive compression, then held; and (Group D) 20-week progressive compression, then decompression. Electrophysiological analysis (latency and amplitude of the N1-P1-N2 wave in somatosensory evoked potentials, SEP), behavioral changes (Tarlov score), imaging test (encroachment ratio (ER) of intraspinal invasion determined by X-ray and CT scan), and histological examinations (hematoxylin and eosin, Nissl, and TUNEL staining) were performed to assess the efficacy of our model.

RESULTS

Tarlov scores gradually decreased as compression increased with time and partially recovered after decompression. The Pearson correlation coefficient between ER and time was r = 0.993 (p < 0.001) in Group B at 10 weeks and Groups C and D at 20 weeks. And ER was negatively correlated with the Tarlov score (r = -0.878, p < 0.001). As compression progressed, the SEP latency was significantly extended (p < 0.001), and the amplitude significantly decreased (p < 0.001), while they were both partially restored after decompression. The number of abnormal motor neurons and TUNEL-positive cells increased significantly (p < 0.001) with compression.

CONCLUSION

Our implantable and wireless intervertebral compression model demonstrated outstanding controllability and reproducibility in simulating chronic cervical spinal cord compression in animals.

Different Time-frequency Distribution Patterns of Somatosensory Evoked Potentials in Dual- and Single-level Spinal Cord Compression

Among patients with cervical myelopathy, the most common level of stenosis at spinal cord of all ages was reported to be between cervical levels C5-6. Previous studies found that time-frequency components (TFCs) of somatosensory evoked potentials (SEPs) possess location information of spinal cord injury (SCI) in single-level deficits in the spinal cord. However, the clinical reality is that there are multiple compressions at multiple spinal cord segments. This study proposed a new algorithm to differentiate distribution patterns of SEP TFCs between the dual-level compression and the corresponding single-level compression, which is potentials in providing precise diagnosis of cervical myelopathy. In the present animal study, a group of rats with dual-level compressive (C5+6) injury to cervical spinal cord was investigated. SEPs were collected at 2 weeks after surgery, while SEP TFCs were calculated. The SEP TFCs under dual-level compression were compared to an existent dataset with one sham control group and three single level compression groups at C4, C5, C6. Behavioral evaluation showed very similar scale of injury severity between individual rats, while histology evaluation confirmed the precise location of injury. According to time-frequency distribution patterns, it showed that the middle-energy components of dual-level showed similar patterns as that of each single-level group. In addition, the low-energy components of the dual-level C5+6 group had the highest correlation with C5 (R=0.3423, p<0.01) and C6 (R=0.4000, p<0.01) groups, but much lower with C4 group (R=0.1071, p=0.012). These results indicated that SEP TFCs components possess information regarding the location of neurological lesion after spinal cord compression. It preliminarily demonstrated that SEP TFCs are likely a useful measure to provide location information of neurological lesions after compression SCI.

Postdecompressive spinal cord blood flow increments in a cervical chronic myelopathy model in rats

OBJECTIVE

In cervical spondylotic myelopathy (CSM), compromise of blood flow to the compressed spinal cord has been postulated to contribute to the development of myelopathy. Although decompressive surgery has been considered to improve spinal cord blood flow, evidence to support this notion is scarce. To determine whether blood flow improves after decompressive surgery for CSM, regional blood flow was measured in a model of chronic cervical compression in rats by using a fluorescent microsphere technique.

METHODS

Thin polyurethane sheets, measuring precisely 3 × 5 × 0.7 mm, were implanted under the C5-6 laminae in 24 rats to induce continuous compression on the cervical spinal cord. These sheets expand gradually by absorbing tissue fluid. This animal model has been demonstrated to reproduce the clinical features and histological changes of CSM, including progressive motor weakness with delayed onset and insidious tissue damage prior to symptom onset. Twenty-four rats that underwent sham operation were allocated to a control group. To confirm the development of cervical myelopathy, motor functions were measured weekly over the study period. Nine weeks after implantation of the sublaminar expanding sheets, histological studies and C5-6 decompressive surgery were conducted. Regional blood flow in the brainstem and cervical spinal cord was measured sequentially until 120 minutes after decompression.

RESULTS

In the CSM group, bilateral forepaw grip strength deteriorated progressively from 5 weeks after implantation. In the compressed C5-6 segment of the spinal cord, significant flattening of the cord, a decreased number of motor neurons, and vacuolations of gray matter were demonstrated. In the control group, blood flow in the brainstem and cervical spinal cord was unchanged by the decompressive surgery. In the CSM group, however, diminished blood flow and continuous blood flow increments for 120 minutes after decompression were demonstrated in the compressed C5-6 spinal cord segment.

CONCLUSIONS

Chronic mechanical compression induced regional spinal cord blood flow insufficiency concomitant with progressive neuronal loss and motor dysfunction in a chronic compression model in rats. Decompressive surgery increased spinal cord blood flow. These findings suggest that blood flow recovery may contribute to postoperative neurological improvement.

LncRNA Xist Contributes to Endogenous Neurological Repair After Chronic Compressive Spinal Cord Injury by Promoting Angiogenesis Through the miR-32-5p/Notch-1 Axis

Endogenous repair after chronic compressive spinal cord injury (CCSCI) is of great clinical interest. Ischemia-hypoxia-induced angiogenesis has been proposed to play an important role during this repair process. Emerging evidence indicates that long non-coding RNAs (lncRNAs) are involved in the pathophysiological processes of various diseases. Here, we identified a lncRNA (Xist; X-inactive specific transcript) with upregulated expression in cervical spine lesions during endogenous neurological repair in CCSCI rats. Therapeutically, the introduction of Xist to rats increased neurological function in vivo as assayed using the Basso, Beattie, and Bresnahan (BBB) score and inclined plane test (IPT). We found that the introduction of Xist enhanced endogenous neurological repair by promoting angiogenesis and microvessel density after CCSCI, while depletion of Xist inhibited angiogenesis and cell sprouting and migration. Mechanistically, Xist promoted angiogenesis by sponging miR-32-5p and modulating Notch-1 expression both in vitro and in vivo. These findings suggest a role of the Xist/miR-32-5p/Notch-1 axis in endogenous repair and provide a potential molecular target for the treatment of ischemia-related central nervous system (CNS) diseases.

Zonisamide ameliorates progression of cervical spondylotic myelopathy in a rat model

Cervical spondylotic myelopathy (CSM) is caused by chronic compression of the spinal cord and is the most common cause of myelopathy in adults. No drug is currently available to mitigate CSM. Herein, we made a rat model of CSM by epidurally implanting an expanding water-absorbent polymer underneath the laminae compress the spinal cord. The CSM rats exhibited progressive motor impairments recapitulating human CSM. CSM rats had loss of spinal motor neurons, and increased lipid peroxidation in the spinal cord. Zonisamide (ZNS) is clinically used for epilepsy and Parkinson's disease. We previously reported that ZNS protected primary spinal motor neurons against oxidative stress. We thus examined the effects of ZNS on our rat CSM model. CSM rats with daily intragastric administration of 0.5% methylcellulose (n = 11) and ZNS (30 mg/kg/day) in 0.5% methylcellulose (n = 11). Oral administration of ZNS ameliorated the progression of motor impairments, spared the number of spinal motor neurons, and preserved myelination of the pyramidal tracts. In addition, ZNS increased gene expressions of cystine/glutamate exchange transporter (xCT) and metallothionein 2A in the spinal cord in CSM rats, and also in the primary astrocytes. ZNS increased the glutathione (GSH) level in the spinal motor neurons of CSM rats. ZNS potentially ameliorates loss of the spinal motor neurons and demyelination of the pyramidal tracts in patients with CSM.

Echinacoside attenuates inflammatory response in a rat model of cervical spondylotic myelopathy via inhibition of excessive mitochondrial fission

Cervical spondylotic myelopathy (CSM) is a leading cause of spinal cord dysfunction with few treatment options. Although mitochondrial dynamics are linked to a wide range of pathological changes in neurodegenerative diseases, a connection between aberrant mitochondrial dynamics and CSM remains to be illuminated. In addition, mechanisms underlying the emerging anti-inflammatory and neuroprotective effects of echinacoside (ECH), the main active ingredient of Cistanche salsa, are poorly understood. We hypothesized that excessive mitochondrial fission plays a critical role in regulating inflammatory responses in CSM, and ECH might alleviate such responses by regulating mitochondrial dynamics. To this end, we assessed the effects of ECH and Mdivi-1, a selective inhibitor of dynamin-related protein (Drp1), in a rat model of chronic cervical cord compression and activated BV2 cells. Our results showed that rats with Mdivi-1 intervention had improved motor function compared with vehicle-treated rats. Indeed, Mdivi-1 treatment attenuated pro-inflammatory cytokine expression, as well as activation of the nod-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome, nuclear transcription factor-κB (NF-κB), and Drp1 in lesions. Compared with vehicle-treated rats, compression sites of Mdivi-1-treated animals exhibited elongated mitochondrial morphologies and reduced reactive oxygen species (ROS). Similarly, ECH-treated rats exhibited neurological recovery and suppression of inflammatory response or related signals in the lesion area after treatment. Interestingly, ECH treatment partly reversed aberrant mitochondrial fragmentation and oxidative stress within the lesion area. In vitro data suggested that ECH suppressed activated microglia by modulating activation of the NLRP3 inflammasome and NF-κB signaling. Furthermore, we observed that ECH markedly inhibited Drp1 translocation onto mitochondria, whereby it regulated mitochondrial dynamics and ROS production, which act as regulators of NLRP3 inflammasome activation and NF-κB signaling. Thus, our findings reveal that mitochondrial dynamics modulate inflammatory responses during CSM. Moreover, ECH may attenuate neuroinflammation in rats subjected to chronic cervical cord compression by regulating Drp1-dependent mitochondrial fission and activation of downstream signaling.

The Pathophysiology of Degenerative Cervical Myelopathy and the Physiology of Recovery Following Decompression

Background: Degenerative cervical myelopathy (DCM), also known as cervical spondylotic myelopathy is the leading cause of spinal cord compression in adults. The mainstay of treatment is surgical decompression, which leads to partial recovery of symptoms, however, long term prognosis of the condition remains poor. Despite advances in treatment methods, the underlying pathobiology is not well-known. A better understanding of the disease is therefore required for the development of treatments to improve outcomes following surgery. Objective: To systematically evaluate the pathophysiology of DCM and the mechanism underlying recovery following decompression. Methods: A total of 13,808 published articles were identified in our systematic search of electronic databases (PUBMED, WEB OF SCIENCE). A total of 51 studies investigating the secondary injury mechanisms of DCM or physiology of recovery in animal models of disease underwent comprehensive review. Results: Forty-seven studies addressed the pathophysiology of DCM. Majority of the studies demonstrated evidence of neuronal loss following spinal cord compression. A number of studies provided further details of structural changes in neurons such as myelin damage and axon degeneration. The mechanisms of injury to cells included direct apoptosis and increased inflammation. Only four papers investigated the pathobiological changes that occur in spinal cords following decompression. One study demonstrated evidence of axonal plasticity following decompressive surgery. Another study demonstrated ischaemic-reperfusion injury following decompression, however this phenomenon was worse when decompression was delayed. Conclusions: In preclinical studies, the pathophysiology of DCM has been poorly studied and a number of questions remain unanswered. The physiological changes seen in the decompressed spinal cord has not been widely investigated and it is paramount that researchers investigate the decompressed spinal cord further to enable the development of therapeutic tools, to enhance recovery following surgery.

Muscone suppresses inflammatory responses and neuronal damage in a rat model of cervical spondylotic myelopathy by regulating Drp1-dependent mitochondrial fission

Cervical spondylotic myelopathy (CSM) is a common cause of disability with few treatments. Aberrant mitochondrial dynamics play a crucial role in the pathogenesis of various neurodegenerative diseases. Thus, regulation of mitochondrial dynamics may offer therapeutic benefit for the treatment of CSM. Muscone, the active ingredient of an odoriferous animal product, exhibits anti-inflammatory and neuroprotective effects for which the underlying mechanisms remain obscure. We hypothesized that muscone might ameliorate inflammatory responses and neuronal damage by regulating mitochondrial dynamics. To this end, the effects of muscone on a rat model of chronic cervical cord compression, as well as activated BV2 cells and injured neurons, were assessed. The results showed that muscone intervention improved motor function compared with vehicle-treated rats. Indeed, muscone attenuated pro-inflammatory cytokine expression, neuronal-apoptosis indicators in the lesion area, and activation of the nod-like receptor family pyrin domain-containing 3 inflammasome, nuclear transcription factor-κB, and dynamin-related protein 1 in Iba1- and βIII-tubulin-labeled cells. Compared with vehicle-treated rats, compression sites of muscone-treated animals exhibited elongated mitochondrial morphologies in individual cell types and reduced reactive oxygen species. In vitro results indicated that muscone suppressed microglial activation and neuronal damage by regulating related-inflammatory or apoptotic molecules. Moreover, muscone inhibited dynamin-related protein 1 activation in activated BV2 cells and injured neurons, whereby it rescued mitochondrial fragmentation and reactive oxygen species production, which regulate a wide range of inflammatory and apoptotic molecules. Our findings reveal that muscone attenuates neuroinflammation and neuronal damage in rats with chronic cervical cord compression by regulating mitochondrial fission events, suggesting its promise for CSM therapy.

Jingshu Keli and its Components Notoginsenoside R1 and Ginsenoside Rb1 Alleviate the Symptoms of Cervical Myelopathy through Kir3.1 Mediated Mechanisms

Background & Objective::

Cervical Spondylotic Myelopathy (CSM) is one of the most serious spinal cord disorders in adults. Pharmacological modulation of ion channels is a common strategy to interfere with CSM and prevent neuronal damage.

Methods:

Here, we investigated the effects of Jingshu Keli (JSKL), a traditional Chinese herbal formula, on CSM-related gait abnormality, mechanical allodynia and thermal hyperalgesia, and assessed the neuronal mechanisms of JSKL on cultured brainstem cells. Behavioral tests and patch clamp recordings were performed to make this assessment.

Results:

In our study, we found that JSKL significantly recovered the gait performance (P<0.001) and decreased the levels of mechanical pain in 18.9% (P<0.01) and thermal pain in 18.1% (P<0.05). Further investigation suggested that JSKL and its containing ginsenoside Rb1 (GRb1), notoginsenoside R1 (NGR1) reduced the action potential frequency in 38.5%, 27.2%, 25.9%, and hyperpolarized resting membrane potential in 15.0%, 13.8%, 12.1%, respectively. Kir channels, not KV channels and KCa channels, were the major intermediate factors achieving treatment effects. Finally, immunostaining results showed that the phosphorylation of Kir3.1 was promoted, whereas the total expression level did not change.

Conclusion:

Our study reveals a novel strategy of treating CSM by using Traditional Chinese Medicines (TCMs) containing active components.

Human recombinant erythropoietin improves motor function in rats with spinal cord compression-induced cervical myelopathy

Objective

Erythropoietin (EPO) is a clinically available hematopoietic cytokine. EPO has shown beneficial effects in the context of spinal cord injury and other neurological conditions. The aim of this study was to evaluate the effect of EPO on a rat model of spinal cord compression-induced cervical myelopathy and to explore the possibility of its use as a pharmacological treatment.

Methods

To develop the compression-induced cervical myelopathy model, an expandable polymer was implanted under the C5-C6 laminae of rats. EPO administration was started 8 weeks after implantation of a polymer. Motor function of rotarod performance and grip strength was measured after surgery, and motor neurons were evaluated with H-E, NeuN and choline acetyltransferase staining. Apoptotic cell death was assessed with TUNEL and Caspase-3 staining. The 5HT, GAP-43 and synaptophysin were evaluated to investigate the protection and plasticity of axons. Amyloid beta precursor protein (APP) was assessed to evaluate axonal injury.

To assess transfer of EPO into spinal cord tissue, the EPO levels in spinal cord tissue were measured with an ELISA for each group after subcutaneous injection of EPO.

Results

High-dose EPO maintained motor function in the compression groups. EPO significantly prevented the loss of motor neurons and significantly decreased neuronal apoptotic cells. Expression of 5HT and synaptophysin was significantly preserved in the EPO group. APP expression was partly reduced in the EPO group. The EPO levels in spinal cord tissue were significantly higher in the high-dose EPO group than other groups.

Conclusion

EPO improved motor function in rats with compression-induced cervical myelopathy. EPO suppressed neuronal cell apoptosis, protected motor neurons, and induced axonal protection and plasticity. The neuroprotective effects were produced following transfer of EPO into the spinal cord tissue. These findings suggest that EPO has high potential as a treatment for degenerative cervical myelopathy.

Mechanisms of Below-Level Pain Following Spinal Cord Injury (SCI)

Mechanisms of below-level pain are discoverable as neural adaptations rostral to spinal injury. Accordingly, the strategy of investigations summarized here has been to characterize behavioral and neural responses to below-level stimulation over time following selective lesions of spinal gray and/or white matter. Assessments of human pain and the pain sensitivity of humans and laboratory animals following spinal injury have revealed common disruptions of pain processing. Interruption of the spinothalamic pathway partially deafferents nocireceptive cerebral neurons, rendering them spontaneously active and hypersensitive to remaining inputs. The spontaneous activity among these neurons is disorganized and unlikely to generate pain. However, activation of these neurons by their remaining inputs can result in pain. Also, injury to spinal gray matter results in a cascade of secondary events, including excitotoxicity, with rostral propagation of excitatory influences that contribute to chronic pain. Establishment and maintenance of below-level pain results from combined influences of injured and spared axons in the spinal white matter and injured neurons in spinal gray matter on processing of nociception by hyperexcitable cerebral neurons that are partially deafferented. A model of spinal stenosis suggests that ischemic injury to the core spinal region can generate below-level pain. Additional questions are raised about demyelination, epileptic discharge, autonomic activation, prolonged activity of C nocireceptive neurons, and thalamocortical plasticity in the generation of below-level pain. PERSPECTIVE: An understanding of mechanisms can direct therapeutic approaches to prevent development of below-level pain or arrest it following spinal cord injury. Among the possibilities covered here are surgical and other means of attenuating gray matter excitotoxicity and ascending propagation of excitatory influences from spinal lesions to thalamocortical systems involved in pain encoding and arousal.

Time course of diffusion tensor imaging metrics in the chronic spinal cord compression rat model

BACKGROUND

Diffusion tensor imaging (DTI) provides information about water molecule diffusion in spinal cord.

PURPOSE

This study was aimed to investigate DTI changes in the different stages of compressive spinal cord induced by water-absorbing material implantation.

MATERIAL AND METHODS

The spinal cord compression was administered over the fourth cervical vertebral level in rat. Rat models were divided into five subgroups according to compression stages: sham group, group A: three-day compression rat models; group B: 12-day compression rat models; group C: 20-day compression rat models; group D: 60-day compression rat models. DTI including fractional anisotropy (FA) and apparent diffusion coefficient (ADC) in the compressive spinal cord were collected. The relationship between the Basso, Beattie, and Bresnahan (BBB) scores and DTI metrics was further explored.

RESULTS

Compared with the sham group, BBB scoring of rat model showed a decreased tendency from group A ( P < 0.05) to group B ( P < 0.05). Then the motor function of rat model hindlimbs was recovered in some degree from group C ( P < 0.05) to group D ( P < 0.05) but had significant motor defects when compared with the normal level ( P < 0.05). The DTI metrics results revealed that chronic spinal cord compression resulted in lower FA value and higher ADC value at the compressive spinal cord level assessed at all four time-points ( P < 0.05). DTI metrics also showed a close correlation with motor function ( P < 0.05).

CONCLUSION

DTI is an optimal pre-clinical imaging tool to reflect locomotor performance and pathological status of compressive spinal cord epicenter in chronic spinal cord compression rat model.

Short- and long-term outcome and magnetic resonance imaging findings after surgical treatment of thoracolumbar spinal arachnoid diverticula in 25 Pugs

Background

There is a successful outcome after surgical management of spinal arachnoid diverticula (SAD) in up to 82% of cases.

Hypothesis/Objectives

We hypothesized that Pugs have favorable short‐term and poor long‐term prognosis after surgical treatment of thoracolumbar SAD. The aim of the present investigation was to describe clinical findings, short‐ and long‐term outcomes, and follow‐up magnetic resonance imaging (MRI) findings in Pugs with thoracolumbar SAD.

Animals

Twenty‐five client owned Pugs with 12‐month follow‐up information after surgical treatment of thoracolumbar SAD.

Methods

Multicenter retrospective case series. All medical records were searched for Pugs diagnosed with SAD. Data regarding signalment, history, surgical procedure, outcome, histopathology, and follow‐up MRI results were extracted.

Results

Mean age at presentation was 7.32 (range 2‐11) years, 80% were males. Short‐term outcome was available in 25 dogs, and improvement was confirmed in 80% of dogs. Long‐term outcome was available in 21 dogs, and deterioration was confirmed in 86% of cases, with late‐onset recurrence of clinical signs after initial postsurgical improvement affecting 85% of Pugs. A moderate correlation (r = 0.50) was found between duration of clinical signs and outcome. In 8 dogs with deteriorating clinical signs, follow‐up MRI revealed regrowth of the SAD in 2 cases, new SAD formation in 2 cases, and intramedullary T2W hyperintensity/syringomyelia in 6 cases.

Conclusions and Clinical Importance

This study suggests that Pugs with thoracolumbar SAD do not have a favorable long‐term prognosis after surgical treatment for reasons yet to be determined.

Expression profile of long non-coding RNAs in cervical spondylotic myelopathy of rats by microarray and bioinformatics analysis

INTRODUCTION

It has been reported that a wide range of long non-coding RNAs (lncRNAs) are implicated in numerous diseases such as tumor, cardiopathy and neurological disorders. Identifying the differentially expressed (DE) profile of lncRNAs in cervical spondylotic myelopathy (CSM) is essential to understand the mechanisms of CSM.

METHODS

Microarray assay, quantitative real-time PCR (qRT-PCR) and bioinformatics analysis were employed to reveal the DE profile and potential functions of lncRNAs in CSM.

RESULTS

Microarray analysis displayed the DE profiles of lncRNAs and mRNAs in rats between the CSM group and the control (CON) group. Thereinto, 1266 DE lncRNAs (738 up-regulation and 528 down-regulation) and 847 mRNAs (487 up-regulation and 360 down-regulation) with >1.1 fold change (FC) were finally identified. Moreover, 17 lncRNAs (13 up-regulation and 4 down-regulation) and 18 mRNAs (13 up-regulation and 5 down-regulation) were found deregulated by >2 FC. Further bioinformatics analysis showed the most remarkable biological processes among up-regulated RNAs contain cellular response to interferon-beta, inflammatory response and innate immune response, which may involve in CSM. Besides, related DE mRNAs of 17 DE lncRNAs in the genome were related to signaling pathway about NOD-like receptor, TNF, and apoptosis. In addition, a co-expression network of lncRNA-mRNA was established for analyzing the biological roles of lncRNAs. Among these, we found a ceRNA network related to CSM. Finally, the expressions of the DE lncRNAs and ceRNA network confirmed by qRT-PCR were in agreement with microarray data.

CONCLUSIONS

Our study revealed the DE profiles of lncRNAs and mRNAs for CSM. Those dysregulated RNAs may represent potential therapeutic targets of CSM for further study.

Interleukin-6 Serum Levels Are Elevated in Individuals with Degenerative Cervical Myelopathy and Are Correlated with Symptom Severity

Background

Few studies have investigated systemic inflammation levels in degenerative cervical myelopathy (DCM). This study evaluated the concentration of inflammatory cytokines in DCM patients and assessed whether they can predict symptom severity.

Material/Methods

A total of 40 consecutive DCM patients and 10 healthy volunteers were included in this study. Concentrations of interleukin (IL)-1β, IL-6, interferon-γ, and tumor necrosis factor-α were compared between DCM patients and normal controls. Spearman’s correlation coefficient was used to examine relationships of cytokines with age, body mass index (BMI), symptom duration, and symptom severity. A DCM compression rat model was established to examine the levels of inflammatory cytokines in serum and cerebrospinal fluid (CSF).

Results

Serum level of IL-6 is significantly higher in DCM patients compared with normal people (0.8±0.5 pg/ml vs. 0.5±0.3 pg/ml, P=0.036). Positive correlations were found between IL-6 levels with BMI (ρ=0.519; P=0.001) and symptom severity (ρ=−0.556, P<0.001). In DCM compression model rats, IL-6 was elevated in CSF (40.5±3.3 vs. 13.2±2.4 pg/ml, P<0.001) and serum (7.1±1.7 vs. 2.9±1.6 pg/ml, P<0.001) samples from rats in the compression operation group compared with the sham operation group. Infusion of IL-6 in rats receiving the sham operation also led to motor function damage and mechanical allodynia threshold decline.

Conclusions

Serum IL-6 level was elevated in DCM patients and its concentration can predict symptom severity. Local infusion of IL-6 led to myelopathy symptoms in model rats, which suggests that anti-inflammation can effectively treat DCM.

Experimental rat model for cervical compressive myelopathy

Previously, a rat model of chronic compressive myelopathy that uses a water-absorbing polymer inserted under a spinal lamina was reported. However, the best size and coefficient of expansion of the polymer sheet have not yet been established. The aim of the present study was to optimize these properties in an ideal rat model of cervical compressive myelopathy. Thirty rats were used in this study. A sheet of water-absorbing polymer was inserted under the cervical laminae. Rats were divided randomly into five experimental groups by the expansion rate (350 or 200%) and thickness (0.5 or 0.7 mm) and the control. After the surgery, the severity of paralysis was evaluated for 12 weeks. At 12 weeks after the surgery, cresyl violet staining was performed to assess the number of motor neurons in the anterior horn at the C4/C5 segment and Luxol Fast Blue staining was performed to assess demyelination in the corticospinal tract at the C7 segment. 'Slow-progressive' paralysis appeared at 4-8 weeks postoperatively in rat models using sheets with 200% expansion. By contrast, only temporary paralysis was observed in rat models using sheets with 350% expansion. A loss of motor neurons in the anterior horn was observed in all groups, except for the control. Demyelination in the corticospinal tract was observed in rat models using sheets with 200% expansion, but not rat models using sheets with 350% expansion. A polymer sheet that expands its volume by 200% is an ideal material for rat models of cervical compressive myelopathy.

Effect of Myoarchitectonic Spinolaminoplasty on Concurrent Hypertension in Patients With Cervical Spondylotic Myelopathy

Objective

When treating patients with cervical spondylotic myelopathy (CSM), we often note amelioration in concomitant hypertension after surgery. To assess the effects of surgery and the mechanisms thereof, blood pressure (BP) and parasympathetic nervous activity were monitored prospectively in CSM patients undergoing surgery.

Methods

Sixty-eight consecutive CSM patients who underwent surgery with myoarchitectonic spinolaminoplasty were enrolled. BP and electrocardiography were recorded preoperatively and at 1, 3, and 6 months postoperatively. Forty-six patients completed the scheduled follow-ups and were analyzed. Preoperatively, 17 had a mean BP higher than 100 mmHg (the HT group) and 12 had hypertension despite taking medication (the HT-refractory group). To evaluate alterations in parasympathetic function, the coefficient of variation of the RR interval (CVRR) was evaluated.

Results

A significant BP reduction was observed in the HT group 6 months after surgery, but not in the normotensive group (n=29). The effect was more remarkable in the HT-refractory group. A transient BP increase at 1 and 3 months after surgery was observed in all groups. Comparisons were made between groups classified by age (over 65 years or younger than 60 years) and the presence or absence of an intramedullary hyperintense T2 signal on magnetic resonance imaging, but no significant differences were detected. Measurements of CVRR did not significantly differ between the groups over the course of follow-up.

Conclusion

Hypertension coexisting with CSM can be ameliorated after surgical treatment. The effect is likely to be mediated by moderation of sympathetic activity, rather than parasympathetic activation. We believe that a combination of adequate decompression of the spinal cord and relief from musculoskeletal stresses effectuate this moderation.

Application of Quantitative Microstructural MR Imaging with Atlas-based Analysis for the Spinal Cord in Cervical Spondylotic Myelopathy

Mapping of MR fiber g-ratio, which is the ratio of the diameter of the axon to the diameter of the neuronal fiber, is introduced in this article. We investigated the MR fiber g-ratio, the axon volume fraction (AVF) and the myelin volume fraction (MVF) to evaluate microstructural changes in the spinal cord in patients with cervical spondylotic myelopathy (CSM) in vivo, using atlas-based analysis. We used diffusion MRI data acquired with a new simultaneous multi-slice accelerated readout-segmented echo planar imaging sequence for diffusion analysis for AVF calculation and magnetization transfer saturation imaging for MVF calculation. The AVFs of fasciculus gracilis in the affected side spinal cord, fasciculus cuneatus and lateral corticospinal tracts (LSCT) in the affected and unaffected side spinal cord were significantly lower (P = 0.019, 0.001, 0019, 0.000, and 0.002, respectively) than those of normal controls. No difference was found in the MVFs. The fiber g-ratio of LSCT was significantly lower (P = 0.040) in the affected side spinal cords than in the normal controls. The pathological microstructural changes in the spinal cord in patients with CSM, presumably partial axonal degenerations with preserved myelin. This technique has the potential to be a clinical biomarker in patients with CSM in vivo.

Neuroprotective Potential of Gentongping in Rat Model of Cervical Spondylotic Radiculopathy Targeting PPAR-γ Pathway

Cervical spondylotic radiculopathy (CSR) is the most general form of spinal degenerative disease and is characterized by pain and numbness of the neck and arm. Gentongping (GTP) granule, as a classical Chinese patent medicine, has been widely used in curing CSR, whereas the underlying mechanism remains unclear. Therefore, the aim of this study is to explore the pharmacological mechanisms of GTP on CSR. The rat model of CSR was induced by spinal cord injury (SCI). Our results showed that GTP could significantly alleviate spontaneous pain as well as ameliorate gait. The HE staining and Western blot results showed that GTP could increase the quantity of motoneuron and enhance the activation of peroxisome proliferator-activated receptor gamma (PPAR-γ) in the spinal cord tissues. Meanwhile, immunofluorescence staining analysis indicated that GTP could reduce the expression of TNF-α in the spinal cord tissues. Furthermore, the protein level of Bax was decreased whereas the protein levels of Bcl-2 and NF200 were increased after the GTP treatment. These findings demonstrated that GTP might modulate the PPAR-γ pathway by inhibiting the inflammatory response and apoptosis as well as by protecting the cytoskeletal integrity of the spinal cord, ultimately play a neuroprotective role in CSR.

Imaging Factors that Distinguish Between Patients with Asymptomatic and Symptomatic Cervical Spondylotic Myelopathy with Mild to Moderate Cervical Spinal Cord Compression

Background

Not all patients with spinal cord compression due to cervical spondylotic myelopathy (CSM) have clinical symptoms and signs. The aim of this study was to investigate and compare the imaging findings in asymptomatic and symptomatic patients with CSM with mild to moderate cervical spinal cord compression.

Material/Methods

A retrospective clinical study included 68 patients. Group A (n=30) had no symptoms and signs; group B (n=38) had symptoms and signs of cervical myelopathy. The age, sex, body mass index (BMI), history of steroid treatment, duration of symptoms, number of spondylotic cervical segments, Torg ratio, range of motion (ROM), incidence of cervical segmental instability, overall curvature of the cervical spine, direction of spinal cord compression, and spinal cord magnetic resonance imaging (MRI) signal intensity were compared.

Results

For groups A and B, the Torg ratio was 90.3% and 83.6% (P<0.05), the incidence of cervical segmental instability was 23.3% and 65.8% (P<0.05), and the incidence of a spinal cord high intensity signal was 13.3% and 86.9% (P<0.05). Logistic regression analysis showed myelopathy as a dependent variable, independently associated with cervical segmental instability (OR=5.898, P=0.037), an MRI T2-weighted intramedullary high signal (OR=9.718, P=0.002), and Torg ratio (OR=0.155, P=0.006).

Conclusions

Cervical segmental instability, a high intramedullary signal on T2-weighted MRI, and the Torg ratio had the greatest capacity to distinguish between asymptomatic and symptomatic patients with CSM with mild to moderate cervical spinal cord compression.

A rat model of chronic syringomyelia induced by epidural compression of the lumbar spinal cord

OBJECTIVE

There has been no established animal model of syringomyelia associated with lumbosacral spinal lipoma. The research on the pathophysiology of syringomyelia has been focused on Chiari malformation, trauma, and inflammation. To understand the pathophysiology of syringomyelia associated with occult spinal dysraphism, a novel animal model of syringomyelia induced by chronic mechanical compression of the lumbar spinal cord was created.

METHODS

The model was made by epidural injection of highly concentrated paste-like kaolin solution through windows created by partial laminectomy of L-1 and L-5 vertebrae. Behavioral outcome in terms of motor (Basso-Beattie-Bresnahan score) and urinary function was assessed serially for 12 weeks. Magnetic resonance images were obtained in some animals to confirm the formation of a syrinx and to monitor changes in its size. Immunohistochemical studies, including analysis for glial fibrillary acidic protein, NeuN, CC1, ED-1, and caspase-3, were done.

RESULTS

By 12 weeks after the epidural compression procedure, syringomyelia formation was confirmed in 85% of the rats (34 of 40) on histology and/or MRI. The syrinx cavities were found rostral to the epidural compression. Motor deficit of varying degrees was seen immediately after the procedure in 28% of the rats (11 of 40). In 13 rats (33%), lower urinary tract dysfunction was seen. Motor deficit improved by 5 weeks after the procedure, whereas urinary dysfunction mostly improved by 2 weeks. Five rats (13%, 5 of 40) died 1 month postoperatively or later, and 3 of the 5 had developed urinary tract infection. At 12 weeks after the operation, IHC showed no inflammatory process, demyelination, or accelerated apoptosis in the spinal cords surrounding the syrinx cavities, similar to sham-operated animals.

CONCLUSIONS

A novel experimental model for syringomyelia by epidural compression of the lumbar spinal cord has been created. The authors hope that it will serve as an important research tool to elucidate the pathogenesis of this type of syringomyelia, as well as the CSF hydrodynamics of the lumbar spinal cord.

Component analysis of somatosensory evoked potentials for identifying spinal cord injury location

This study aims to determine whether the time-frequency components (TFCs) of somatosensory evoked potentials (SEPs) can be used to identify the specific location of a compressive spinal cord injury using a classification technique. Waveforms of SEPs after compressive injuries at various locations (C4, C5 and C6) in rat spinal cords were decomposed into a series of TFCs using a high-resolution time-frequency analysis method. A classification method based on support vector machine (SVM) was applied to the distributions of these TFCs among different pathological locations. The difference among injury locations manifests itself in different categories of SEP TFCs. High-energy TFCs of normal-state SEPs have significantly higher power and frequency than those of injury-state SEPs. The location of C5 is characterized by a unique distribution pattern of middle-energy TFCs. The difference between C4 and C6 is evidenced by the distribution pattern of low-energy TFCs. The proposed classification method based on SEP TFCs offers a discrimination accuracy of 80.2%. In this study, meaningful information contained in various SEP components was investigated and used to propose a new application of SEPs for identification of the location of pathological changes in the cervical spinal cord.

Prevalence and Imaging Characteristics of Nonmyelopathic and Myelopathic Spondylotic Cervical Cord Compression

STUDY DESIGN

Cross-sectional population-based observational study.

OBJECTIVE

To estimate the prevalence of nonmyelopathic spondylotic cervical cord compression (NMSCCC) and cervical spondylotic myelopathy (CSM) in a population older than 40 years and to evaluate the magnetic resonance imaging (MRI) characteristics of these conditions.

SUMMARY OF BACKGROUND DATA

The prevalence of neither NMSCCC nor CSM is known and there exists no commonly accepted quantitative MRI definition of cervical cord compression.

METHODS

A group of 183 randomly recruited volunteers, 93 women, median age 66 years, range 40-80 years, underwent MRI examination of the cervical spine and spinal cord on a 1.5 T device using conventional sequences from disc levels C2/C3 to C6/C7. The imaging criterion for cervical cord compression was defined as a change in spinal cord contour at the level of an intervertebral disc on axial or sagittal MRI scan.

RESULTS

MRI signs of cervical cord compression were found in 108 individuals (59.0%; 95% CI: 51.5%-66.2%); their numbers increased with age from 31.6% in the fifth decade to 66.8% in the eighth. Clinical signs of symptomatic CSM were found in two cases (1.1%), and 75 cases (41.0%) were without compression. An anteroposterior cervical canal diameter at the level of intervertebral disc (CDdisc) of less than 9.9 mm was associated with the highest probability of NMSCCC-odds ratio (OR) = 32.5, followed by a compression ratio of ≤0.5: OR = 11.1.

CONCLUSION

The prevalence of NMSCCC in a population older than 40 years is higher than previously reported and increases with age. CDdisc and compression ratio had the highest capacity to discriminate between subjects with and without asymptomatic compression, and their cut-off values could be used to objectify criteria for cervical cord compression.

LEVEL OF EVIDENCE

2.

Granulocyte Colony-Stimulating Factor Improves Motor Function in Rats Developing Compression Myelopathy

STUDY DESIGN

Basic animal research.

OBJECTIVE

The effects of granulocyte colony-stimulating factor (G-CSF) were assessed in a rat chronic spinal cord compression model to explore the potential of G-CSF as a pharmacological treatment for cervical spondylotic myelopathy.

SUMMARY OF BACKGROUND DATA

G-CSF is a hematopoietic cytokine used clinically to treat neutropenia. Recently, neuroprotective effects of G-CSF have been reported in spinal cord disorders.

METHODS

To introduce the chronic cervical cord compression, thin polyurethane sheets were implanted under C5-C6 laminae of rats and gradually expanded by absorbing water. This model reproduces delayed compressive myelopathy of the cervical spine. In sham operations, the sheets were immediately removed. G-CSF (15 μg/kg) or normal saline (NS) was administered subcutaneously 5 days a week. Experimental groups were sham operation given NS; cord compression given NS; and cord compression given G-CSF. To assess motor functions, rotarod performance, and grip strength were measured. Twenty-six weeks after surgery, cervical spinal cords were examined histopathologically. In the prevention experiment, G-CSF or NS administration was started immediately after surgery. In the treatment experiment, their administration was started 8 weeks after surgery. In another experiment, in three groups in the prevention experiment, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling staining was performed to assess apoptotic cell death at 8 weeks after surgery.

RESULTS

In the prevention experiment, administration of G-CSF preserved the motor functions and motor neurons throughout the 26 weeks, and significantly decreased the number of apoptotic cells at 8 weeks. In the treatment experiment, G-CSF administration from 8 weeks after surgery markedly restored the motor function temporarily to a level equal to the sham group.

CONCLUSION

G-CSF prevents the decline in motor functions and preserves motor neurons in the rat chronic cord compression model. G-CSF also improves motor function in the progressive phase of compression myelopathy.

LEVEL OF EVIDENCE

N/A.

In vivo diffusion tensor imaging of chronic spinal cord compression : a rat model with special attention to the conus medullaris

Background Few studies have focused on diffusion tensor imaging (DTI) parameters of the conus medullaris after chronic compression in the cervical spinal cord. Purpose To discuss the correlation of DTI parameters between the chronically compressed cervical spinal cord and the conus medullaris in a rat model at different time points. Material and Methods Fifty female Sprague-Dawley rats were randomized into five groups: control group (group A), sham group (group B), and test groups C, D, and E (1, 2, and 3 weeks after compression, respectively). Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values of the cervical spinal cord and conus medullaris were compared among different groups. Correlations of ADC and FA values of the cervical spinal cord with those of the conus medullaris were performed in all groups. Results The ADC values at the cervical spinal cord and conus medullaris in all test groups were higher than those of group A and B, while the FA values were lower. The ADC value of the cervical spinal cord was linearly correlated with that of the conus medullaris only in group D. There were no linear correlations of FA values between the cervical spinal cord and the conus medullaris in all test groups. Conclusion After compression of the cervical spinal cord, ADC values of the cervical spinal cord and conus medullaris in test group were significantly increased, while FA values were significantly decreased. The ADC value of the cervical spinal cord was linearly correlated with that of the conus medullaris at 2 weeks after compression.

Axonal plasticity underpins the functional recovery following surgical decompression in a rat model of cervical spondylotic myelopathy

Cervical spondylotic myelopathy (CSM) is the most common spinal cord disorder and a major cause of disability in adults. Improvements following surgical decompression are limited and patients often remain severely disabled. Post mortem studies indicate that CSM is associated with profound axonal loss. However, our understanding of the pathophysiology of CSM remains limited.To investigate the hypothesis that axonal plasticity plays a role in the recovery following surgical decompression, we adopted a novel preclinical model of mild to moderate CSM. Spinal cord compression resulted in significant locomotor deterioration, increased expression of the axonal injury marker APP, and loss of serotonergic fibres. Surgical decompression partially reversed the deficits and attenuated APP expression. Decompression was also associated with axonal sprouting, reflected in the restoration of serotonergic fibres and an increase of GAP43 expression. The re-expression of synaptophysin indicated the restoration of functional synapses following decompression. Promoting axonal plasticity may therefore be a therapeutic strategy for promoting neurological recovery in CSM.

Establishment of a rat model of chronic thoracolumbar cord compression with a flat plastic screw

Previous studies of animal models of chronic mechanical compression of the spinal cord have mainly focused on cervical and thoracic lesions, but few studies have investigated thoracolumbar injury. The specific pathophysiological mechanism of chronic thoracolumbar cord injury has not yet been elucidated. The purpose of this study was to improve animal models of chronic thoracolumbar cord compression using the progressive screw. A custom-designed flat plastic screw was implanted in the spinal cord between thoracic vertebrae 12 and lumbar 1 of rats. The screw was tightened one complete turn (0.5 mm) every 7 days for 4 weeks to create different levels of chronic spinal cord compression. Following insertion of the screw, there was a significant decline in motor function of the hind limbs, and severe stenosis of micro-computed tomography parameters in the spinal cord. Cortical somatosensory evoked potential amplitudes were reduced remarkably, and latencies were prolonged at 30 minutes after surgery. The loss of motor neurons in the gray matter was marked. Demyelination and cavitation were observed in the white matter. An appropriate rat model of chronic thoracolumbar cord compression was successfully created using the progressive screw compression method, which simulated spinal cord compression injury.

Delayed neurological deterioration after surgery for intraspinal meningiomas: Ischemia-reperfusion injury in a rat model

Delayed neurological deterioration in the absence of direct cord insult following surgical removal and cord decompression is a rare but severe postoperative complication in a small subset of patients with intraspinal meningiomas. To date, the underlying pathophysiology of such a finding remains unclear and ischemia-reperfusion injury (IRI) is considered as the potential etiology in the literature. However, no experimental research has been reported to prove this hypothesis. The present study investigated whether IRI occurs following decompression surgery using an experimental rat model of chronic compressive spinal cord injury (SCI). A chronic spinal cord compression model was developed with various sizes of polymer sheets (mild and severe compression) that were microsurgically implanted underneath the T8-9 laminae, and occurrence of IRI in the spinal cord following decompression was determined by measuring superoxide dismutase (SOD) level and malondialdehyde (MDA) concentration. In the mild compression groups, after decompression SOD activities significantly increased along with a reduction in MDA content compared with the non-decompression group (P<0.05), which exhibited diminishment of lipid peroxidation and relief of the secondary injury. These findings indicated that decompression is effective to improve neurological recovery and may deliver improved outcomes for chronic mild compression of the spinal cord. However, in severe compression groups, after decompression, SOD activities markedly reduced further along with a significant increase in MDA content compared with non-decompression group (P<0.05). The results indicated that lipid peroxidation increased immediately after decompression surgery which resulted from reperfusion of the spinal cord. These findings demonstrated IRI may occur as a result of chronic severe compression of the spinal cord. In clinical practice, sudden cord expansion and reperfusion may have lead to disruption in the blood spinal cord barrier, and triggered a cascade of IRI resulting in postoperative neurologic deterioration. Recognition of this neurological deterioration following removal for intraspinal meningiomas may improve preoperative patient counseling and merits further study for determination of the precise pathophysiology.

Inflammation Level after Decompression Surgery for a Rat Model of Chronic Severe Spinal Cord Compression and Effects on Ischemia-Reperfusion Injury

Delayed neurological deterioration in the absence of direct spinal cord insult following surgical decompression is a severe postoperative complication in patients with chronic severe spinal cord compression (SCC). The spinal cord ischemia-reperfusion injury (IRI) has been verified as a potential etiology of the complication. However, the exact pathophysiologic mechanisms of the decompression-related IRI remain to be defined. In this study, we developed a practical rat model of chronic severe SCC. To explore the underlying role of inflammation in decompression-related IRI, immunoreactivity of pro-inflammatory cytokines including tumor necrosis factor-alpha (TNF-α) and interleukin-1β (IL-1β) before and after decompression were measured. In addition, expression level of TNF-α and IL-1β was examined with Western blot. Immunohistochemical staining showed negative result in gray matters in the sham group and sham-decompression group. In the severe compression group, strong positive staining of TNF-α and IL-1β were found, suggesting a dramatic infiltration of inflammatory cells in gray matters. Furthermore, the severe compression group showed a significant increase in expression level of TNF-α and IL-1β as compared with the sham group (p < 0.05). In the severe compression-decompression group, both immunostaining and Western blot showed significant increase of TNF-α and IL-1β levels in the spinal cord compared with the severe compression group (p < 0.05). The results demonstrated that surgical decompression plays a stimulative role in inflammation through increasing the expression of inflammatory cytokines in the rat model of chronic severe SCC injury. Inflammation may be one of the important pathological mechanisms of decompression-related IRI of chronic ischemia.

Comparison of operant escape and reflex tests of nociceptive sensitivity

Testing of reflexes such as flexion/withdrawal or licking/guarding is well established as the standard for evaluating nociceptive sensitivity and its modulation in preclinical investigations of laboratory animals. Concerns about this approach have been dismissed for practical reasons - reflex testing requires no training of the animals; it is simple to instrument; and responses are characterized by observers as latencies or thresholds for evocation. In order to evaluate this method, the present review summarizes a series of experiments in which reflex and operant escape responding are compared in normal animals and following surgical models of neuropathic pain or pharmacological intervention for pain. Particular attention is paid to relationships between reflex and escape responding and information on the pain sensitivity of normal human subjects or patients with pain. Numerous disparities between results for reflex and operant escape measures are described, but the results of operant testing are consistent with evidence from humans. Objective reasons are given for experimenters to choose between these and other methods of evaluating the nociceptive sensitivity of laboratory animals.

Cilostazol, a selective Type III phosphodiesterase inhibitor: prevention of cervical myelopathy in a rat chronic compression model

Object

Regional blood flow is decreased in experimental models of chronic spinal cord compression, and the alteration presumably contributes to the development of myelopathy. Cilostazol (Otsuka Pharmaceuticals Co.), a selective Type III phosphodiesterase inhibitor, has been shown to be neuroprotective in cerebral hypoperfusion animal models and clinically effective in preventing the recurrence of cerebral infarction. To investigate the neuroprotective effect of cilostazol on cervical spondylotic myelopathy, the preventive effect against progressive motor dysfunction and the loss of anterior horn motor neurons were assessed using a chronic cord compression model in rats.

Methods

To produce chronic cervical cord compression in male Wistar rats, thin polyurethane sheets (3 × 5 × 0.7 mm) that gradually expand over 48–72 hours by absorbing water were implanted under the C5–6 laminae. In sham operations, the sheets were momentarily placed and then immediately removed. This model has been shown to reproduce characteristic features of clinical cervical myelopathy, with progressive motor disturbances after a latency period and insidious neuronal loss preceding the onset of symptoms. In the treatment group, cilostazol (30 mg/kg/day) was orally administered to the rats once a day, starting the day after surgery and continuing through the entire observation period of 25 weeks. In the control group, vehicle solution was administered under the same protocol. Changes in motor function were monitored by measuring bilateral forepaw grip strength and the duration of forced running on a treadmill. Twenty-five weeks after surgery, cervical spinal cords were examined histopathologically.

Results

Cilostazol preserved both forepaw grip strength and forced running capability. The drug also preserved anterior horn motor neurons in the C5–6 spinal cord segment, which diminished in number in the untreated chronic compression group. The drug decreased the number of TUNEL-positive apoptotic cells.

Conclusions

These results indicate that cilostazol is neuroprotective in the chronically compressed cervical cord and is potentially useful in the treatment of cervical spondylotic myelopathy.

Demyelination initiated by oligodendrocyte apoptosis through enhancing endoplasmic reticulum-mitochondria interactions and Id2 expression after compressed spinal cord injury in rats

BACKGROUND

Demyelination is one of the most important pathological factors of spinal cord injury. Oligodendrocyte apoptosis is involved in triggering demyelination. However, fewer reports on pathological changes and mechanism of demyelination have been presented from compressed spinal cord injury (CSCI). The relative effect of oligodendrocyte apoptosis on CSCI-induced demyelination and the mechanism of apoptosis remain unclear.

AIMS

In this study, a custom-designed model of CSCI was used to determine whether or not demyelination and oligodendrocyte apoptosis occur after CSCI. The pathological changes in axonal myelinated fibers were investigated by osmic acid staining and transmission electron microscopy. Myelin basic protein (MBP), which is used in myelin formation in the central nervous system, was detected by immunofluorescence and Western blot assays. Oligodendrocyte apoptosis was revealed by in situ terminal-deoxytransferase-mediated dUTP nick-end labeling. To analyze the mechanism of oligodendrocyte apoptosis, we detected caspase-12 [a representative of endoplasmic reticulum (ER) stress], cytochrome c (an apoptotic factor and hallmark of mitochondria), and inhibitor of DNA binding 2 (Id2, an oligodendrocyte lineage gene) by immunofluorescence and Western blot assays.

RESULTS

The custom-designed model of CSCI was successfully established. The rats were spastic, paralyzed, and incontinent. The Basso, Beattie, and Bresnahan (BBB) locomotor rating scale scores were decreased as time passed. The compressed spinal cord slices were ischemic. Myelin sheaths became swollen and degenerative; these sheaths were broken down as time passed after CSCI. MBP expression was downregulated after CSCI and consistent with the degree of demyelination. Oligodendrocyte apoptosis occurred at 1 day after CSCI and increased as caspase-12 expression was enhanced and cytochrome c was released. Id2 was distributed widely in the white matter. Id2 expression increased with time after CSCI.

CONCLUSION

Demyelination occurred after CSCI and might be partly caused by oligodendrocyte apoptosis, which was positively correlated with ER-mitochondria interactions and enhanced Id2 expression after CSCI in rats.

Diffusion tensor imaging of the spinal cord: a review

Diffusion tensor imaging (DTI) is a magnetic resonance technique capable of measuring the magnitude and direction of water molecule diffusion in various tissues. The use of DTI is being expanded to evaluate a variety of spinal cord disorders both for prognostication and to guide therapy. The purpose of this article is to review the literature on spinal cord DTI in both animal models and humans in different neurosurgical conditions. DTI of the spinal cord shows promise in traumatic spinal cord injury, cervical spondylotic myelopathy, and intramedullary tumors. However, scanning protocols and image processing need to be refined and standardized.

Neurological recovery is impaired by concurrent but not by asymptomatic pre-existing spinal cord compression after traumatic spinal cord injury

STUDY DESIGN

An in vivo animal study to examine the influence of pre-existing or concurrent spinal canal stenosis (SCS) on the functional recovery after spinal cord injury (SCI).

OBJECTIVES

To clarify whether spinal cord compression before or after SCI results in less favorable neurological recovery.

SUMMARY OF BACKGROUND DATA

The influence of spinal cord compression on the neurological recovery after SCI remains unclear.

METHODS

We created mice with SCS using an extradural spacer before or after producing SCI and statistically analyzed the correlation between the extent of SCS and neurological outcomes. The extent of SCS was calculated by micro-computed tomography, and the spinal cord blood flow (SCBF) was measured serially with laser Doppler flowmetry. Molecular and immunohistochemical examinations were performed to evaluate the neovascularization at the site of cord compression.

RESULTS

Spacer placement (<300 μm) alone in the control mouse resulted in no neurological deficits. Even with spacer placement that caused asymptomatic SCS, the functional recovery after SCI was progressively impaired as spacer sizes increased in the mice with SCS co-occurring with SCI, whereas no significant impact was observed in the mice with pre-existing SCS, irrespective of the spacer sizes. The SCBF progressively decreased immediately after SCS was produced, but it fully recovered at the later time points. Angiogenesis-related genes were upregulated, and neovascular vessels were observed after producing the SCS. We found that concurrent SCS resulted in a significant reduction and impaired the subsequent recovery of the SCBF, whereas pre-existing SCS did not affect the hemodynamics of the spinal cord after SCI.

CONCLUSION

The dynamic reduction of the SCBF occurring immediately after spinal cord compression is a significant factor that impairs the neurological recovery after SCI, whereas pre-existing SCS is not always an impediment due to the potentially restructured SCBF.

Dietary therapy to promote neuroprotection in chronic spinal cord injury

OBJECT

The pathogenesis of cervical spondylotic myelopathy (CSM) is related to both primary mechanical and secondary biological injury. The authors of this study explored a novel, noninvasive method of promoting neuroprotection in myelopathy by using curcumin to minimize oxidative cellular injury and the capacity of omega-3 fatty acids to support membrane structure and improve neurotransmission.

METHODS

An animal model of CSM was created using a nonresorbable expandable polymer placed in the thoracic epidural space, which induced delayed myelopathy. Animals that underwent placement of the expandable polymer were exposed to either a diet rich in docosahexaenoic acid and curcumin (DHA-Cur) or a standard Western diet (WD). Twenty-seven animals underwent serial gait testing, and spinal cord molecular assessments were performed after the 6-week study period.

RESULTS

At the conclusion of the study period, gait analysis revealed significantly worse function in the WD group than in the DHA-Cur group. Levels of brain-derived neurotrophic factor (BDNF), syntaxin-3, and 4-hydroxynonenal (4-HNE) were measured in the thoracic region affected by compression and lumbar enlargement. Results showed that BDNF levels in the DHA-Cur group were not significantly different from those in the intact animals but were significantly greater than in the WD group. Significantly higher lumbar enlargement syntaxin-3 in the DHA-Cur animals combined with a reduction in lipid peroxidation (4-HNE) indicated a possible healing effect on the plasma membrane.

CONCLUSIONS

Data in this study demonstrated that DHA-Cur can promote spinal cord neuroprotection and neutralize the clinical and biochemical effects of myelopathy.

Hyaluronan tetrasaccharide in the cerebrospinal fluid is associated with self-repair of rats after chronic spinal cord compression

The objective of this study was to explore changes in hyaluronan levels in the cerebrospinal fluid (CSF) in a spinal cord compression model, to investigate whether hyaluronan tetrasaccharide was involved in this process, and to test the effects of hyaluronan tetrasaccharide on neuron and oligodendrocyte repair. We developed a chronic spinal cord compression model with various sizes of polymer sheets (1.5×0.7×0.3 mm(3); 5×1.5×0.7 mm(3)) that were implanted microsurgically underneath the C(5-6) laminae. The rats were divided into three groups: a sham group, a mildly compressed (MC) group, and a widely compressed (WC) group. Locomotor functional evaluations revealed that the behavioral function of the MC and WC groups dropped to their lowest level from the fourth to fifth week and gradually recovered thereafter. The hyaluronan levels in the CSF gradually increased after spinal cord compression. Furthermore, hyaluronan tetrasaccharide was involved in the hyaluronan change. In addition, we found that nuclear factor kappa B (NF-κB) and cellular inhibitor-of-apoptosis protein 2 (c-IAP(2)) were co-expressed in neurons and oligodendrocytes, and caspase-3 expression gradually decreased in the compression model. The brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF) expression was upregulated in astrocytes at the fourth week post-compression. Hyaluronan tetrasaccharide (HA(4)) induced NF-κB and c-IAP(2) to suppress the H(2)O(2)-induced apoptosis in primary neuronal cultures and increased BDNF and VEGF expression in astrocytic cultures in vitro. These findings suggest that HA(4) in the CSF may associate with behavioral recovery by increasing the levels of NF-κB, c-IAP(2), and neurotrophic factors after chronic spinal cord compression.