Isolated spinal cord contusion in rats induces chronic brain neuroinflammation, neurodegeneration, and cognitive impairment. Involvement of cell cycle activation

Depression-like behavior is associated with deficits in cognition and hippocampal neurogenesis in a subset of spinally contused male, but not female, rats

Depression and cognitive deficits present at higher rates among people with spinal cord injury (SCI) compared to the general population, yet these SCI comorbidities are poorly addressed. Sex and age appear to play roles in depression incidence, but consensus on the direction of their effects is limited. Systemic and cortical inflammation and disruptions in hippocampal neurogenesis have been identified as potential treatment targets, but a comprehensive understanding of these mechanisms remains elusive. We used a rodent SCI model to interrogate these gaps in knowledge. We examined post-injury depression-like behavior and cognitive deficits, as well as the association between affect, cognition, chronic hippocampal inflammation and hippocampal neurogenesis, in young and middle-aged male and female Sprague-Dawley rats. Depression-like behavior manifested in male and female subsets of SCI rats irrespective of age, at rates commensurate with the incidence of clinical depression. Changes in components of behavior were driven by sex and age, and affective outcomes were independent of common post-injury pathophysiological outcomes including locomotor functional deficits and spinal lesion severity. Interestingly, however, only male depression-like SCI rats exhibited deficits in hippocampal-associated spatial cognition. Neurogenesis was also disrupted in only SCI males in regions of the hippocampus responsible for affective outcomes. Decreased neurogenesis among middle-aged male subjects coincided with increases in numbers of the pro-inflammatory markers CD86 and iNOS, while middle-aged females had increased numbers of cells expressing Iba-1 and anti-inflammatory marker CD206. Overall, the present data suggest that post-SCI depression and cognition may be affected, in part, by sex- and age-dependent changes in hippocampal neurogenesis and inflammation. Hippocampal neurogenesis is a potential target to address psychological wellbeing after SCI, but therapeutic strategies must carefully consider sex and age as biological variables.

Activation of GPR55 alleviates neuropathic pain and chronic inflammation

Neuropathic pain (NP) significantly impacts the quality of life due to its prolonged duration and lack of effective treatment. Recent findings suggest that targeting neuroinflammation is a promising approach for treating NP. G protein-coupled receptor 55 (GPR55), a member of the GPCR family, plays an important role in neuroinflammatory regulation. CID16020046, a GPR55 agonist, possesses promising anti-neuroinflammatory effects. Herein, the therapeutic effect of CID16020046 on NP was investigated in an NP rat model. The NP model was established using the unilateral sciatic nerve chronic constriction injury (CCI) assay. Both sham and CCI rats were intraperitoneally administered with 20 mg/kg CID16020046. NP was assessed using paw withdrawal threshold (PWT) and paw withdrawal latency (PWL). First, we showed that GPR55 was downregulated in the spinal dorsal horn of CCI rats. After CCI rats were treated with CID16020046, the values of PWT and PWL were increased, indicating their effect on pain relief. The treated rats had attenuated release of inflammatory cytokines in the spinal cord, decreased spinal malondialdehyde (MDA) levels, and increased spinal glutathione peroxidase (GSH-PX) activity. Additionally, the increased levels of phosphorylated nuclear factor (NF)-κB p65 in CCI rats were significantly alleviated by CID16020046 treatment. Mechanistically, we showed that CID16020046 significantly suppressed the activation of the Janus kinase (JAK2)/signal transducer and activator of transcription 3 (JAK2/STAT3) pathway in the spinal cord of CCI-treated rats. However, Colivelin TFA (a STAT3 agonist) abolished the effect of CID16020046 on JAK2/STAT3 activation. In conclusion, our data demonstrate that the activation of GPR55 by CID16020046 alleviates NP and neuroinflammation in CCI rats by mediating the JAK2/STAT3 pathway.

Old age alters inflammation and autophagy signaling in the brain, leading to exacerbated neurological outcomes after spinal cord injury in male mice

Older patients with spinal cord injury (SCI) have different features with regard to neurological characteristics after injury. Recent large-scale longitudinal population-based studies showed that individuals with SCI are at a higher risk of developing dementia than non-SCI patients, indicating that SCI is a potential risk factor for dementia. Aging is known to potentiate inflammation and neurodegeneration at the injured site leading to impaired recovery from SCI. However, no research has been aimed at studying the mechanisms of SCI-mediated cognitive impairment in the elderly. The present study examined neurobehavioral and molecular changes in the brain and the underlying mechanisms associated with brain dysfunction in aged C57BL/6 male mice using a contusion SCI model. At 2 months post-injury, aged mice displayed worse performance in locomotor, cognitive and depressive-like behavioral tests compared to young adult animals. Histopathology in injured spinal cord tissue was exacerbated in aged SCI mice. In the brain, transcriptomic analysis with NanoString neuropathology panel identified activated microglia and dysregulated autophagy as the most significantly altered pathways by both age and injury. These findings were further validated by flow cytometry, which demonstrated increased myeloid and lymphocytes infiltration at both the injured site and brain of aged mice. Moreover, SCI in aged mice altered microglial function and dysregulated autophagy in microglia, resulting in worsened neurodegeneration. Taken together, our data indicate that old age exacerbates neuropathological changes in both the injured spinal cord and remote brain regions leading to poorer functional outcomes, at least in part, through altered inflammation and autophagy function.

Multi-platform omics sequencing dissects the atlas of plasma-derived exosomes in rats with or without depression-like behavior after traumatic spinal cord injury

BACKGROUND

Exosomes can penetrate the blood-brain barrier for material exchange between the peripheral and central nervous systems. Differences in exosome contents could explain the susceptibility of different individuals to depression-like behavior after traumatic spinal cord injury (TSCI).

METHODS

Hierarchical clustering was used to integrate multiple depression-related behavioral outcomes in sham and TSCI rats and ultimately identify non-depressed and depressed rats. The difference in plasma exosome contents between non-depressed and depressed rats after TSCI was assessed in 15 random subjects by performing plasma exosome transcriptomics, mass spectroscope-based proteomics, and non-targeted metabolomics analyses.

RESULTS

The results revealed that about 27.6% of the rats developed depression-like behavior after TSCI. Totally, 10 differential metabolites, 81 differentially expressed proteins (DEPs), 373 differentially expressed genes (DEGs), and 55 differentially expressed miRNAs (DEmiRNAs) were identified between non-depressed TSCI and sham rats. Meanwhile, 37 differential metabolites, 499 DEPs, 1361 DEGs, and 89 DEmiRNAs were identified between depressed and non-depressed TSCI rats. Enrichment analysis showed that the progression of depression-like behavior after TSCI may be related to amino acid metabolism disorder and dysfunction of multiple signaling pathways, including endocytosis, lipid and atherosclerosis, toll-like receptor, TNF, and PI3K-Akt pathway.

CONCLUSION

Overall, our study systematically revealed for the first time the differences in plasma exosome contents between non-depressed and depressed rats after TSCI, which will help broaden our understanding of the complex molecular mechanisms involved in brain functional recombination after TSCI.

Effects of dim light at night in C57BL/6 J mice on recovery after spinal cord injury

Spinal cord injury (SCI) can cause long-lasting locomotor deficits, pain, and mood disorders. Anatomical and functional outcomes are exacerbated by inflammation after SCI, which causes secondary damage. One promising target after SCI is manipulating the circadian system, which optimizes biology and behavior for time of day - including neuroimmune responses and mood-related behaviors. Circadian disruption after SCI is likely worsened by a disruptive hospital environment, which typically includes dim light-at-night (dLAN). Here, we hypothesized that mice subjected to SCI, then placed in dLAN, would exhibit worsened locomotor deficits, pain-like behavior, and anxiety-depressive-like symptoms compared to mice maintained in light days with dark nights (LD). C57BL/6 J mice received sham surgery or moderate T9 contusion SCI, then were placed permanently in LD or dLAN. dLAN after SCI did not worsen locomotor deficits; rather, SCI-dLAN mice showed slight improvement in open-field locomotion at the final timepoint. Although dLAN did not alter SCI-induced heat hyperalgesia, SCI-dLAN mice exhibited an increase in mechanical allodynia at 13 days post-SCI compared to SCI-LD mice. SCI-LD and SCI-dLAN mice had similar outcomes using sucrose preference (depressive-like) and open-field (anxiety-like) tests. At 21 dpo, SCI-dLAN mice had reduced preference for a novel juvenile compared to SCI-LD, implying that dLAN combined with SCI may worsen this mood-related behavior. Finally, lesion size was similar between SCI-LD and SCI-dLAN mice. Therefore, newly placing C57BL/6 J mice in dLAN after SCI had modest effects on locomotor, pain-like, and mood-related behaviors. Future studies should consider whether clinically-relevant circadian disruptors, alone or in combination, could be ameliorated to enhance outcomes after SCI.

Cognitive, behavioral and psychiatric symptoms in patients with spinal cord injury: a scoping review

Spinal Cord Injury (SCI) is a condition where the spinal cord is damaged and experiences partial or complete loss of motor and/or sensory function, which is typically less than normal. After SCI, patients may exhibit more severe psychiatric symptoms and experience cognitive impairments, including reduced speed and attention processing capacity, as well as difficulties with executive function and episodic memory retention. Among the behavioral and psychiatric symptoms, depression, anxiety, substance use disorder, and posttraumatic stress disorder are the most common. This review aims to investigate the cognitive, behavioral, or psychiatric symptoms of the patient with SCI and their influence on the rehabilitation process. Studies were identified from an online search of PubMed, Web of Science, Cochrane Library, and Embase databases. Studies published between 2013-2023 were selected. This review has been registered on OSF (n) 3KB2U. We have found that patients with SCI are at high risk of cognitive impairment and experience a wide range of difficulties, including tasks based on processing speed and executive function. This clinical population may experience adjustment disorders with depression and anxiety, as well as other psychiatric symptoms such as fatigue, stress, and suicidal ideation. This review has demonstrated that SCI patients may experience psychiatric symptoms and cognitive impairments that affect their functioning. At the same time, these patients may be more prone to various adjustment and mood disorders. Moreover, these two aspects may interact with each other, causing a range of symptoms, increasing the risk of hospitalization, and delaying the rehabilitation process.

Brain region changes following a spinal cord injury

Brain-related complications are common in clinical practice after spinal cord injury (SCI); however, the molecular mechanisms of these complications are still unclear. Here, we reviewed the changes in the brain regions caused by SCI from three perspectives: imaging, molecular analysis, and electrophysiology. Imaging studies revealed abnormal functional connectivity, gray matter volume atrophy, and metabolic abnormalities in brain regions after SCI, leading to changes in the structure and function of brain regions. At the molecular level, chemokines, inflammatory factors, and damage-associated molecular patterns produced in the injured area were retrogradely transmitted through the corticospinal tract, cerebrospinal fluid, or blood circulation to the specific brain area to cause pathologic changes. Electrophysiologic recordings also suggested abnormal changes in brain electrical activity after SCI. Transcranial magnetic stimulation, transcranial direct current stimulation, and deep brain stimulation alleviated pain and improved motor function in patients with SCI; therefore, transcranial therapy may be a new strategy for the treatment of patients with SCI.

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

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

Effects of dim light at night in C57BL/6J mice on recovery after spinal cord injury

Spinal cord injury (SCI) can cause long-lasting locomotor deficits, pain, and mood disorders. Anatomical and functional outcomes are exacerbated by inflammation after SCI, which causes secondary damage. One promising target after SCI is manipulating the circadian system, which optimizes biology and behavior for time of day - including neuroimmune responses and mood-related behaviors. Circadian disruption after SCI is likely worsened by a disruptive hospital environment, which typically includes dim light-at-night (dLAN). Here, we hypothesized that mice subjected to SCI, then placed in dLAN, would exhibit worsened locomotor deficits, pain-like behavior, and anxiety-depressive-like symptoms compared to mice maintained in light days with dark nights (LD). C57BL/6J mice received sham surgery or moderate T9 contusion SCI, then were placed permanently in LD or dLAN. dLAN after SCI did not worsen locomotor deficits; rather, SCI-dLAN mice showed slight improvement in open-field locomotion at the final timepoint. Although dLAN did not alter SCI-induced heat hyperalgesia, SCI-dLAN mice exhibited an increase in mechanical allodynia at 13 days post-SCI compared to SCI-LD mice. SCI-LD and SCI-dLAN mice had similar outcomes using sucrose preference (depressive-like) and open-field (anxiety-like) tests. At 21 dpo, SCI-dLAN mice had reduced preference for a novel juvenile compared to SCI-LD, implying that dLAN combined with SCI may worsen this mood-related behavior. Finally, lesion size was similar between SCI-LD and SCI-dLAN mice. Therefore, newly placing C57BL/6J mice in dLAN after SCI had modest effects on locomotor, pain-like, and mood-related behaviors. Future studies should consider whether clinically-relevant circadian disruptors, alone or in combination, could be ameliorated to enhance outcomes after SCI.

Role of NLRP3 Inflammasome in Post-Spinal-Cord-Injury Anxiety and Depression: Molecular Mechanisms and Therapeutic Implications

The majority of research on the long-term effects of spinal cord injury (SCI) has primarily focused on neuropathic pain (NP), psychological issues, and sensorimotor impairments. Among SCI patients, mood disorders, such as anxiety and depression, have been extensively studied. It has been found that chronic stress and NP have negative consequences and reduce the quality of life for individuals living with SCI. Our review examined both human and experimental evidence to explore the connection between mood changes following SCI and inflammatory pathways, with a specific focus on NLRP3 inflammasome signaling. We observed increased proinflammatory factors in the blood, as well as in the brain and spinal cord tissues of SCI models. The NLRP3 inflammasome plays a crucial role in various diseases by controlling the release of proinflammatory molecules like interleukin 1β (IL-1β) and IL-18. Dysregulation of the NLRP3 inflammasome in key brain regions associated with pain processing, such as the prefrontal cortex and hippocampus, contributes to the development of mood disorders following SCI. In this review, we summarized recent research on the expression and regulation of components related to NLRP3 inflammasome signaling in mood disorders following SCI. Finally, we discussed potential therapeutic approaches that target the NLRP3 inflammasome and regulate proinflammatory cytokines as a way to treat mood disorders following SCI.

Involvement of microglia in chronic neuropathic pain associated with spinal cord injury - a systematic review

In recent decade microglia have been found to have a central role in the development of chronic neuropathic pain after injury to the peripheral nervous system. It is widely accepted that peripheral nerve injury triggers microglial activation in the spinal cord, which contributes to heightened pain sensation and eventually chronic pain states. The contribution of microglia to chronic pain arising after injury to the central nervous system, such as spinal cord injury (SCI), has been less studied, but there is evidence supporting microglial contribution to central neuropathic pain. In this systematic review, we focused on post-SCI microglial activation and how it is linked to emergence and maintenance of chronic neuropathic pain arising after SCI. We found that the number of studies using animal SCI models addressing microglial activity is still small, compared with the ones using peripheral nerve injury models. We have collected 20 studies for full inclusion in this review. Many mechanisms and cellular interactions are yet to be fully understood, although several studies report an increase of density and activity of microglia in the spinal cord, both in the vicinity of the injury and in the spared spinal tissue, as well as in the brain. Changes in microglial activity come with several molecular changes, including expression of receptors and activation of signalling pathways. As with peripheral neuropathic pain, microglia seem to be important players and might become a therapeutic target in the future.

The gray matter atrophy and related network changes occur in the higher cognitive region rather than the primary sensorimotor cortex after spinal cord injury

Objective

This study used functional magnetic resonance imaging (fMRI) to explore brain structural and related network changes in patients with spinal cord injury (SCI).

Methods

Thirty-one right-handed SCI patients and 31 gender- and age-matched healthy controls (HC) were included. The gray matter volume (GMV) changes in SCI patients were observed using voxel-based morphometry (VBM). Then, these altered gray matter clusters were used as the regions of interest (ROIs) for whole-brain functional connectivity (FC) analysis to detect related functional changes. The potential association between GMV and FC values with the visual analog scale (VAS), the American Spinal Injury Association (ASIA) score, and the course of injuries was investigated through partial correlation analysis.

Results

GMV of the frontal, temporal, and insular cortices was lower in the SCI group than in the HC group. No GMV changes were found in the primary sensorimotor area in the SCI group. Besides, the altered FC regions were not in the primary sensorimotor area but in the cingulate gyrus, supplementary motor area, precuneus, frontal lobe, and insular. Additionally, some of these altered GMV and FC regions were correlated with ASIA motor scores, indicating that higher cognitive regions can affect motor function in SCI patients.

Conclusions

This study demonstrated that gray matter and related network reorganization in patients with SCI occurred in higher cognitive regions. Future rehabilitation strategies should focus more on cognitive functions.

Sexually dimorphic extracellular vesicle responses after chronic spinal cord injury are associated with neuroinflammation and neurodegeneration in the aged brain

BACKGROUND

Medical advances have made it increasingly possible for spinal cord injury (SCI) survivors to survive decades after the insult. But how SCI affects aging changes and aging impacts the injury process have received limited attention. Extracellular vesicles (EVs) are recognized as critical mediators of neuroinflammation after CNS injury, including at a distance from the lesion site. We have previously shown that SCI in young male mice leads to robust changes in plasma EV count and microRNA (miR) content. Here, our goal was to investigate the impact of biological sex and aging on EVs and brain after SCI.

METHODS

Young adult age-matched male and female C57BL/6 mice were subjected to SCI. At 19 months post-injury, total plasma EVs were isolated by ultracentrifugation and characterized by nanoparticle tracking analysis (NTA). EVs miR cargo was examined using the Fireplex® assay. The transcriptional changes in the brain were assessed by a NanoString nCounter Neuropathology panel and validated by Western blot (WB) and flow cytometry (FC). A battery of behavioral tests was performed for assessment of neurological function.

RESULTS

Transcriptomic changes showed a high number of changes between sham and those with SCI. Sex-specific changes were found in transcription networks related to disease association, activated microglia, and vesicle trafficking. FC showed higher microglia and myeloid counts in the injured tissue of SCI/Female compared to their male counterparts, along with higher microglial production of ROS in both injured site and the brain. In the latter, increased levels of TNF and mitochondrial membrane potential were seen in microglia from SCI/Female. WB and NTA revealed that EV markers are elevated in the plasma of SCI/Male. Particle concentration in the cortex increased after injury, with SCI/Female showing higher counts than SCI/Male. EVs cargo analysis revealed changes in miR content related to injury and sex. Behavioral testing confirmed impairment of cognition and depression at chronic time points after SCI in both sexes, without significant differences between males and females.

CONCLUSIONS

Our study is the first to show sexually dimorphic changes in brain after very long-term SCI and supports a potential sex-dependent EV-mediated mechanism that contributes to SCI-induced brain changes.

Initial study on an expert system for spine diseases screening using inertial measurement unit

In recent times, widely understood spine diseases have advanced to one of the most urgetn problems where quick diagnosis and treatment are needed. To diagnose its specifics (e.g. to decide whether this is a scoliosis or sagittal imbalance) and assess its extend, various kind of imaging diagnostic methods (such as X-Ray, CT, MRI scan or ST) are used. However, despite their common use, some may be regarded as (to a level) invasive methods and there are cases where there are contraindications to using them. Besides, which is even more of a problem, these are very expensive methods and whilst their use for pure diagnostic purposes is absolutely valid, then due to their cost, they cannot rather be considered as tools which would be equally valid for bad posture screening programs purposes. This paper provides an initial evaluation of the alternative approach to the spine diseases diagnostic/screening using inertial measurement unit and we propose policy-based computing as the core for the inference systems. Although the methodology presented herein is potentially applicable to a variety of spine diseases, in the nearest future we will focus specifically on sagittal imbalance detection.

Paths to hippocampal damage in neuromyelitis optica spectrum disorders

AIMS

Many patients with neuromyelitis optica spectrum disorders (NMOSD) suffer from cognitive impairment affecting memory, processing speed and attention and suffer from depressive symptoms. Because some of these manifestations could trace back to the hippocampus, several magnetic resonance imaging (MRI) studies have been performed in the past, with a number of groups describing volume loss of the hippocampus in NMOSD patients, whereas others did not observe such changes. Here, we addressed these discrepancies.

METHODS

We performed pathological and MRI studies on the hippocampi of NMOSD patients, combined with detailed immunohistochemical analysis of hippocampi from experimental models of NMOSD.

RESULTS

We identified different pathological scenarios for hippocampal damage in NMOSD and its experimental models. In the first case, the hippocampus was compromised by the initiation of astrocyte injury in this brain region and subsequent local effects of microglial activation and neuronal damage. In the second case, loss of hippocampal volume was seen by MRI in patients with large tissue-destructive lesions in the optic nerves or the spinal cord, and the pathological work-up of tissue derived from a patient with such lesions revealed subsequent retrograde neuronal degeneration affecting different axonal tracts and neuronal networks. It remains to be seen whether remote lesions and associated retrograde neuronal degeneration on their own are sufficient to cause extensive volume loss of the hippocampus, or whether they act in concert with small astrocyte-destructive, microglia-activating lesions in the hippocampus that escape detection by MRI, either due to their small size or due to the chosen time window for examination.

CONCLUSIONS

Different pathological scenarios can culminate in hippocampal volume loss in NMOSD patients.

Ginsenoside Rg1 attenuation of neurogenesis disorder and neuronal apoptosis in the rat hippocampus after spinal cord injury may involve brain-derived neurotrophic factor/extracellular signal-regulated kinase signaling

OBJECTIVE

We previously demonstrated that spinal cord injury (SCI) induced hippocampus injury and depression in rodents. Ginsenoside Rg1 effectively prevents neurodegenerative disorders. Here, we investigated the effects of ginsenoside Rg1 on the hippocampus after SCI.

METHODS

We used a rat compression SCI model. Western blotting and morphologic assays were used to investigate the protective effects of ginsenoside Rg1 in the hippocampus.

RESULTS

Brain-derived neurotrophic factor/extracellular signal-regulated kinases (BDNF/ERK) signaling was altered in the hippocampus at 5 weeks after SCI. SCI attenuated neurogenesis and enhanced the expression of cleaved caspase-3 in the hippocampus; however, ginsenoside Rg1 attenuated cleaved caspase-3 expression and improved neurogenesis and BDNF/ERK signaling in the rat hippocampus. The results suggest that SCI affects BDNF/ERK signaling, and ginsenoside Rg1 can attenuate hippocampal damage after SCI.

CONCLUSION

We speculate that the protective effects of ginsenoside Rg1 in hippocampal pathophysiology after SCI may involve BDNF/ERK signaling. Ginsenoside Rg1 shows promise as a therapeutic pharmaceutical product when seeking to counter SCI-induced hippocampal damage.

Transient Reflexive Pain Responses and Chronic Affective Nonreflexive Pain Responses Associated with Neuroinflammation Processes in Both Spinal and Supraspinal Structures in Spinal Cord-Injured Female Mice

Central neuropathic pain is not only characterized by reflexive pain responses, but also emotional or affective nonreflexive pain responses, especially in women. Some pieces of evidence suggest that the activation of the neuroimmune system may be contributing to the manifestation of mood disorders in patients with chronic pain conditions, but the mechanisms that contribute to the development and chronicity of CNP and its associated disorders remain poorly understood. This study aimed to determine whether neuroinflammatory factor over-expression in the spinal cord and supraspinal structures may be associated with reflexive and nonreflexive pain response development from acute SCI phase to 12 weeks post-injury in female mice. The results show that transient reflexive responses were observed during the SCI acute phase associated with transient cytokine overexpression in the spinal cord. In contrast, increased nonreflexive pain responses were observed in the chronic phase associated with cytokine overexpression in supraspinal structures, especially in mPFC. In addition, results revealed that besides cytokines, the mPFC showed an increased glial activation as well as CX3CL1/CX3CR1 upregulation in the neurons, suggesting the contribution of neuron-glia crosstalk in the development of nonreflexive pain responses in the chronic spinal cord injury phase.

Brain and spinal cord trauma: what we know about the therapeutic potential of insulin growth factor 1 gene therapy

Although little attention has been paid to cognitive and emotional dysfunctions observed in patients after spinal cord injury, several reports have described impairments in cognitive abilities. Our group also has contributed significantly to the study of cognitive impairments in a rat model of spinal cord injury. These findings are very significant because they demonstrate that cognitive and mood deficits are not induced by lifestyle changes, drugs of abuse, and combined medication. They are related to changes in brain structures involved in cognition and emotion, such as the hippocampus. Chronic spinal cord injury decreases neurogenesis, enhances glial reactivity leading to hippocampal neuroinflammation, and triggers cognitive deficits. These brain distal abnormalities are recently called tertiary damage. Given that there is no treatment for Tertiary Damage, insulin growth factor 1 gene therapy emerges as a good candidate. Insulin growth factor 1 gene therapy recovers neurogenesis and induces the polarization from pro-inflammatory towards anti-inflammatory microglial phenotypes, which represents a potential strategy to treat the neuroinflammation that supports tertiary damage. Insulin growth factor 1 gene therapy can be extended to other central nervous system pathologies such as traumatic brain injury where the neuroinflammatory component is crucial. Insulin growth factor 1 gene therapy could emerge as a new therapeutic strategy for treating traumatic brain injury and spinal cord injury.

Microglial activation in the motor cortex mediated NLRP3-related neuroinflammation and neuronal damage following spinal cord injury

Spinal cord injury (SCI) is a traumatic event that can lead to neurodegeneration. Neuronal damage in the primary motor cortex (M1) can hinder motor function recovery after SCI. However, the exact mechanisms involved in neuronal damage after SCI remain incompletely understood. In this study, we found that microglia were activated in M1 after SCI, which triggered Nod-like receptor protein 3 (NLRP3) related chronic neuroinflammation and neuronal damage in vivo. Meanwhile, treatment with the microglia inhibitor minocycline reduced inflammation-induced neuronal damage in M1, protected the integrity of the motor conduction pathway, and promoted motor function recovery. Furthermore, we simulated chronic inflammation in M1 after SCI by culturing the primary neurons in primary microglia-conditioned medium, and observed that the injury to the primary neurons also occurred in vitro; however, as observed in vivo, these effects could be mitigated by minocycline treatment. Our results indicated that microglial activation in M1 mediates NLRP3-related neuroinflammation and causes the injury to M1 neurons, thereby impairing the integrity of the motor conduction pathway and inhibiting motor function recovery. These findings might contribute to the identification of novel therapeutic strategies for SCI.

Motor Neuroplastic Effects of a Novel Paired Stimulation Technology in an Incomplete Spinal Cord Injury Animal Model

Paired stimulation of the brain and spinal cord can remodel the central nervous tissue circuitry in an animal model to induce motor neuroplasticity. The effects of simultaneous stimulation vary according to the extent and severity of spinal cord injury. Therefore, our study aimed to determine the significant effects on an incomplete SCI rat brain and spinal cord through 3 min and 20 min stimulations after 4 weeks of intervention. Thirty-three Sprague Dawley rats were classified into six groups: (1) normal, (2) sham, (3) iTBS/tsDCS, (4) iTBS/ts-iTBS, (5) rTMS/tsDCS, and (6) rTMS/ts-iTBS. Paired stimulation of the brain cortex and spinal cord thoracic (T10) level was applied simultaneously for 3−20 min. The motor evoked potential (MEP) and Basso, Beattie, and Bresnahan (BBB) scores were recorded after every week of intervention for four weeks along with wheel training for 20 min. Three-minute stimulation with the iTBS/tsDCS intervention induced a significant (p < 0.050 *) increase in MEP after week 2 and week 4 treatments, while 3 min iTBS/ts-iTBS significantly improved MEP (p < 0.050 *) only after the week 3 intervention. The 20 min rTMS/ts-iTBS intervention showed a significant change only in post_5 min after week 4. The BBB score also changed significantly in all groups except for the 20 min rTMS/tsDCS intervention. iTBS/tsDCS and rTMS/ts-iTBS interventions induce neuroplasticity in an incomplete SCI animal model by significantly changing electrophysiological (MEP) and locomotion (BBB) outcomes.

Intersection of hippocampus and spinal cord: a focus on the hippocampal alpha-synuclein accumulation, dopaminergic receptors, neurogenesis, and cognitive function following spinal cord injury in male rats

Background

Following Spinal Cord Injury (SCI), innumerable inflammatory and degenerative fluctuations appear in the injured site, and even remotely in manifold areas of the brain. Howbeit, inflammatory, degenerative, and oscillatory changes of motor cortices have been demonstrated to be due to SCI, according to recent studies confirming the involvement of cognitive areas of the brain, such as hippocampus and prefrontal cortex. Therefore, addressing SCI induced cognitive complications via different sights can be contributory in the treatment approaches.

Results

Herein, we used 16 male Wistar rats (Sham = 8, SCI = 8). Immunohistochemical results revealed that spinal cord contusion significantly increases the accumulation of alpha-synuclein and decreases the expression of Doublecortin (DCX) in the hippocampal regions like Cornu Ammonis1 (CA1) and Dentate Gyrus (DG). Theses degenerative manifestations were parallel with a low expression of Achaete-Scute Family BHLH Transcription Factor 1 (ASCL1), SRY (sex determining region Y)-box 2 (SOX2), and dopaminergic receptors (D1 and D5). Additionally, based on the TUNEL assay analysis, SCI significantly increased the number of apoptotic cells in the CA1 and DG regions. Cognitive function of the animals was assessed, using the O-X maze and Novel Object Recognition (NORT); the obtained findings indicted that after SCI, hippocampal neurodegeneration significantly coincides with the impairment of learning, memory and recognition capability of the injured animals.

Conclusions

Based on the obtained findings, herein SCI reduces neurogenesis, decreases the expression of D1 and D5, and increases apoptosis in the hippocampus, which are all associated with cognitive function deficits.

Graphical Abstract

Hippocampal Mitochondrial Abnormalities Induced the Dendritic Complexity Reduction and Cognitive Decline in a Rat Model of Spinal Cord Injury

Spinal cord injury (SCI) is a progressive neurodegenerative disease in addition to a traumatic event. Cognitive dysfunction following SCI has been widely reported in patients and animal models. However, the neuroanatomical changes affecting cognitive function after SCI, as well as the mechanisms behind these changes, have so far remained elusive. Herein, we found that SCI accelerates oxidative stress damage of hippocampal neuronal mitochondria. Then, for the first time, we presented a three-dimensional morphological atlas of rat hippocampal neurons generated using a fluorescence Micro-Optical Sectioning Tomography system, a method that accurately identifies the spatial localization of neurons and trace neurites. We showed that the number of dendritic branches and dendritic length was decreased in late stage of SCI. Western blot and transmission electron microscopy analyses also showed a decrease in synaptic communication. In addition, a battery of behavioral tests in these animals revealed hippocampal based cognitive dysfunction, which could be attributed to changes in the dendritic complexity of hippocampal neurons. Taken together, these results suggested that mitochondrial abnormalities in hippocampal neurons induced the dendritic complexity reduction and cognitive decline following SCI. Our study highlights the neuroanatomical basis and importance of mitochondria in brain degeneration following SCI, which might contribute to propose new therapeutic strategies.

Spinal Cord Injury Causes Prominent Tau Pathology Associated with Brain Post-Injury Sequela

Spinal cord injury (SCI) can result in significant neurological impairment and functional and cognitive deficits. It is well established that SCI results in focal neurodegeneration that gradually spreads to other cord areas. On the other hand, traumatic brain injury (TBI) is strongly associated with tau protein pathology and neurodegeneration that can spread in areas throughout the brain. Tau is a microtubule-associated protein abundant in neurons and whose abnormalities result in neuronal cell death. While SCI and TBI have been extensively studied, there is limited research on the relationship between SCI and brain tau pathology. As a result, in this study, we examined tau pathology in spinal cord and brain samples obtained from severe SCI mouse models at various time points. The effects of severe SCI on locomotor function, spatial memory, anxiety/risk-taking behavior were investigated. Immunostaining and immunoblotting confirmed a progressive increase in tau pathology in the spinal cord and brain areas. Moreover, we used electron microscopy to examine brain samples and observed disrupted mitochondria and microtubule structure following SCI. SCI resulted in motor dysfunction, memory impairment, and abnormal risk-taking behavior. Notably, eliminating pathogenic cis P-tau via systemic administration of appropriate monoclonal antibodies restored SCI's pathological and functional consequences. Thus, our findings suggest that SCI causes severe tauopathy that spreads to brain areas, indicating brain dysfunction. Additionally, tau immunotherapy with an anti-cis P-tau antibody could suppress pathogenic outcomes in SCI mouse models, with significant clinical implications for SCI patients. SCI induces profound pathogenic cis p-tau, which diffuses into the brain through CSF, resulting in brain neurodegeneration and cognitive decline.

Sexual dimorphism in neurological function after SCI is associated with disrupted neuroinflammation in both injured spinal cord and brain

Whereas human spinal cord injury (SCI) is more common in men, the prevalence is growing in women. However, little is known about the effect of biological sex on brain dysfunction and injury mechanisms. To model the highest per capita rate of injury (ages between 16 and 30 years old) in humans, in the present study, young adult or a young/middle-aged male and female C57BL/6 mice were subjected to moderate contusion SCI. When mice were injured at 10-12-week-old, transcriptomic analysis of inflammation-related genes and flow cytometry revealed a more aggressive neuroinflammatory profile in male than females following 3 d SCI, ostensibly driven by sex-specific changes myeloid cell function rather than cell number. Female mice were generally more active at baseline, as evidenced by greater distance traveled in the open field. After SCI, female mice had more favorable locomotor function than male animals. At 13 weeks post-injury, male mice showed poor performance in cognitive and depressive-like behavioral tests, while injured female mice showed fewer deficits in these tasks. However, when injured at 6 months old followed by 8 months post-injury, male mice had considerably less inflammatory activation compared with female animals despite having similar or worse outcomes in affective, cognitive, and motor tasks. Collectively, these findings indicate that sex differences in functional outcome after SCI are associated with the age at onset of injury, as well as disrupted neuroinflammation not only at the site of injury but also in remote brain regions. Thus, biological sex should be considered when designing new therapeutic agents.

Therapeutic Potential of Astrocyte Transplantation

Cell transplantation is an attractive treatment strategy for a variety of brain disorders, as it promises to replenish lost functions and rejuvenate the brain. In particular, transplantation of astrocytes has come into light recently as a therapy for amyotrophic lateral sclerosis (ALS); moreover, grafting of astrocytes also showed positive results in models of other conditions ranging from neurodegenerative diseases of older age to traumatic injury and stroke. Despite clear differences in etiology, disorders such as ALS, Parkinson's, Alzheimer's, and Huntington's diseases, as well as traumatic injury and stroke, converge on a number of underlying astrocytic abnormalities, which include inflammatory changes, mitochondrial damage, calcium signaling disturbance, hemichannel opening, and loss of glutamate transporters. In this review, we examine these convergent pathways leading to astrocyte dysfunction, and explore the existing evidence for a therapeutic potential of transplantation of healthy astrocytes in various models. Existing literature presents a wide variety of methods to generate astrocytes, or relevant precursor cells, for subsequent transplantation, while described outcomes of this type of treatment also differ between studies. We take technical differences between methodologies into account to understand the variability of therapeutic benefits, or lack thereof, at a deeper level. We conclude by discussing some key requirements of an astrocyte graft that would be most suitable for clinical applications.

IGF1 Gene Therapy Reversed Cognitive Deficits and Restored Hippocampal Alterations After Chronic Spinal Cord Injury

The hippocampus is implicated in the generation of memory and learning, processes which involve extensive neuroplasticity. The generation of hippocampal adult-born neurons is particularly regulated by glial cells of the neurogenic niche and the surrounding microenvironment. Interestingly, recent evidence has shown that spinal cord injury (SCI) in rodents leads to hippocampal neuroinflammation, neurogenesis reduction, and cognitive impairments. In this scenario, the aim of this work was to evaluate whether an adenoviral vector expressing IGF1 could reverse hippocampal alterations and cognitive deficits after chronic SCI. SCI caused neurogenesis reduction and impairments of both recognition and working memories. We also found that SCI increased the number of hypertrophic arginase-1 negative microglia concomitant with the decrease of the number of ramified surveillance microglia in the hilus, molecular layer, and subgranular zone of the dentate gyrus. RAd-IGF1 treatment restored neurogenesis and improved recognition and working memory impairments. In addition, RAd-IGF1 gene therapy modulated differentially hippocampal regions. In the hilus and molecular layer, IGF1 gene therapy recovered the number of surveillance microglia coincident with a reduction of hypertrophic microglia cell number. However, in the neurogenic niche, IGF1 reduced the number of ramified microglia and increased the number of hypertrophic microglia, which as a whole expressed arginase-1. In summary, RAd-IGF1 gene therapy might surge as a new therapeutic strategy for patients with hippocampal microglial alterations and cognitive deficits such as those with spinal cord injury and other neurodegenerative diseases.

Inflammation increases the development of depression behaviors in male rats after spinal cord injury

Following spinal cord injury, 18-26% of patients are diagnosed with depressive disorders, compared to 8-12% in the general population. As increased inflammation strongly correlates with depression in both animal and human studies, we hypothesized that the immune activation inherent to SCI could increase depression-like behavior. Thus, we proposed that reducing immune activation with minocycline, a microglial inhibitor, would decrease depression-like behavior following injury. Male Sprague-Dawley rats were given minocycline in their drinking water for 14 days following a moderate, mid-thoracic (T12) spinal contusion. An array of depression-like behaviors (social activity, sucrose preference, forced swim, open field activity) were examined prior to injury as well as on days 9-10, 19-20, and 29-30 post-injury. Peripheral cytokine levels were analyzed in serum collected prior to injury and 10 days post-injury. Hierarchical cluster analysis divided subjects into two groups based on behavior: depressed and not-depressed. Depressed subjects displayed lower levels of open field activity and social interaction relative to their not-depressed counterparts. Depressed subjects also showed significantly greater expression of pro-inflammatory cytokines both before and after injury and displayed lower levels of hippocampal neurogenesis than not-depressed subjects. Intriguingly, subjects who later showed depressive behaviors had higher baseline levels of the pro-inflammatory cytokine IL-6, which persisted throughout the duration of the experiment. Minocycline, however, did not affect serum cytokine levels and did not block the development of depression; equal numbers of minocycline versus vehicle-treated subjects appeared in both phenotypic groups. Despite this, these data overall suggest that molecular correlates of inflammation prior to injury could predict the development of depression after a physical stressor.

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

BACKGROUND

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

NOVEL METHOD

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

RESULTS

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

COMPARISON WITH EXISTING METHODS

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

CONCLUSIONS

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

Extracellular Vesicles as an Emerging Frontier in Spinal Cord Injury Pathobiology and Therapy

Extracellular vesicles (EVs) are membrane-delimited particles that are secreted by nearly all cell types. EVs mediate crucial physiological functions and pathophysiological processes in the CNS. As carriers of diverse bioactive cargoes (e.g., proteins, lipids, and nucleic acids) that can be modified in response to external stimuli, EVs have emerged as pathological mediators following neurotrauma such as spinal cord injury (SCI). We discuss the roles of endogenous EVs in the CNS as well as crosstalk with peripheral EVs in relation to neurotrauma, with a particular focus on SCI. We then summarize the status of EV-based therapeutic advances in preclinical animal models for these conditions. Finally, we discuss new bioengineering strategies that are poised to enhance CNS-specific therapeutic capabilities of EVs.

Longitudinal [18F]FDG and [13N]NH3 PET/CT imaging of brain and spinal cord in a canine hemisection spinal cord injury model

To further understand the neurological changes induced by spinal cord injury (SCI) in its acute and subacute stages, we evaluated longitudinal changes in glucose and glutamate metabolism in the spinal cord and brain regions of a canine hemisection SCI model. [18F]FDG and [13N]NH3 positron-emission tomography (PET) with computed tomography (CT) was performed before SCI and at 1, 3, 7, 14, and 21 days after SCI. Spinal cord [18F]FDG uptake increased and peaked at 3 days post SCI. Similar changes were observed in the brain regions but were not statistically significant. Compared to the acute phase of SCI, [13N]NH3 uptake increased in the subacute stage and peaked at 7 days post SCI in all analyzed brain regions. But in spinal cord, no [13N]NH3 uptake was detected before SCI when the blood-spinal cord barrier (BSCB) was intact, then gradually increased when the BSCB was damaged after SCI. [13N]NH3 uptake was significantly correlated with plasma levels of the BSCB disruption marker, monocyte chemoattractant protein-1 (MCP-1). Overall, we showed that SCI induced in vivo changes in glucose uptake in both the spinal cord and the examined brain regions, and changes in glutamine synthetase activity in the latter. Moreover, our results suggest that [13N]NH3 PET may serve as a potential method for assessing BSCB permeability in vivo.

The Effects of P75NTR on Learning Memory Mediated by Hippocampal Apoptosis and Synaptic Plasticity

Neurological diseases bring great mental and physical torture to the patients, and have long-term and sustained negative effects on families and society. The attention to neurological diseases is increasing, and the improvement of the material level is accompanied by an increase in the demand for mental level. The p75 neurotrophin receptor (p75NTR) is a low-affinity neurotrophin receptor and involved in diverse and pleiotropic effects in the developmental and adult central nervous system (CNS). Since neurological diseases are usually accompanied by the regression of memory, the pathogenesis of p75NTR also activates and inhibits other signaling pathways, which has a serious impact on the learning and memory of patients. The results of studies shown that p75NTR is associated with LTP/LTD-induced synaptic enhancement and inhibition, suggest that p75NTR may be involved in the progression of synaptic plasticity. And its proapoptotic effect is associated with activation of proBDNF and inhibition of proNGF, and TrkA/p75NTR imbalance leads to pro-survival or proapoptotic phenomena. It can be inferred that p75NTR mediates apoptosis in the hippocampus and amygdale, which may affect learning and memory behavior. This article mainly discusses the relationship between p75NTR and learning memory and associated mechanisms, which may provide some new ideas for the treatment of neurological diseases.

Hippocampal neurodegeneration and rhythms mirror each other during acute spinal cord injury in male rats

Spinal Cord Injury (SCI), triggers neurodegenerative changes in the spinal cord, and simultaneously alters oscillatory manifestations of motor cortex. However, these disturbances may not be limited to motor areas and other parts such as hippocampus, which is vital in the neurogenesis and cognitive function, may be affected in the neurogenic and oscillatory manners. Addressing this remarkable complication of SCI, we evaluated the hippocampal neurogenesis and rhythms through acute phase of SCI. In the present study, we used 40 male rats (Sham.W1 = 10, SCI.W1 = 10, Sham.W2 = 10, SCI.W2 = 10), and findings revealed that contusive SCI declines hippocampal rhythms (Delta, Theta, Beta, Gamma) power and max-frequency. Also, there was a significant decrease in the DCX + and BrdU + cells of the dentate gyrus; correlated significantly with rhythms power decline. Considering the TUNEL assay analysis, there were significantly greater apoptotic cells, in the CA1, CA3, and DG regions of injured animals. Furthermore, according to the western blotting analysis, the expression of receptors (NMDA, GABAA, Muscarinic1), which are essential in the neurogenesis and generation of rhythms significantly attenuated following SCI. Our study demonstrated that acute SCI, alters the power and max-frequency of hippocampal rhythms parallel with changes in the hippocampal neurogenesis, apoptosis, and receptors expression.

Motor demands of cognitive testing may artificially reduce executive function scores in individuals with spinal cord injury

Objective: To determine whether the motor demands of cognitive tests contribute to differences in cognitive function scores in participants with and without spinal cord injury (SCI).Design: Cohort study.Setting: Rehabilitation research laboratory.Participants: 68 individuals without SCI ("NON") and 22 individuals with motor complete SCI ("SCI").Interventions: None.Outcome Measures: NIH Toolbox cognitive assessments, including two with motor demands and reaction-time based scoring (Dimensional Change Card Sort (DCCS), Flanker Inhibitory Control and Attention (Flanker) and two without timed scoring (List Sorting Working Memory (List Sorting), Picture Sequence Memory Test (Picture Sequence). Tests were administered with and without the assistance of a proctor on two randomly-determined days (>24 hr interval). For DCCS and Flanker, the motor-task score offset was estimated as the difference between the proctored and non-proctored scores.Results: For demographically-corrected data, proctoring reduced DCCS and Flanker scores (P < 0.001) but mitigated apparent differences between SCI and NON (all P > 0.403). SCI and NON did not differ for List Sorting (P > 0.072) but did differ significantly for Picture Sequence (P < 0.001). Significant practice effects existed for memory-based tests (List Sorting and Picture Sequence); all P < 0.015, effect size>0.645.Conclusions: DCCS and Flanker scores for individuals with SCI may be artificially reduced consequent to secondary motor demands of the tests. Proctoring and computation of a motor-response score offset enables comparisons to be made between individuals with SCI and a Non-SCI control cohort; however, further work is needed to determine whether offset-adjusted scores can be compared to standardized normative values.

Spinal cord injury alters microRNA and CD81+ exosome levels in plasma extracellular nanoparticles with neuroinflammatory potential

Extracellular vesicles (EVs) have been implicated mechanistically in the pathobiology of neurodegenerative disorders, including central nervous system injury. However, the role of EVs in spinal cord injury (SCI) has received limited attention to date. Moreover, technical limitations related to EV isolation and characterization methods can lead to misleading or contradictory findings. Here, we examined changes in plasma EVs after mouse SCI at multiple timepoints (1d, 3d, 7d, 14d) using complementary measurement techniques. Plasma EVs isolated by ultracentrifugation (UC) were decreased at 1d post-injury, as shown by nanoparticle tracking analysis (NTA), and paralleled an overall reduction in total plasma extracellular nanoparticles. Western blot (WB) analysis of UC-derived plasma EVs revealed increased expression of the tetraspanin exosome marker, CD81, between 1d and 7d post-injury. To substantiate these findings, we performed interferometric and fluorescence imaging of single, tetraspanin EVs captured directly from plasma with ExoView®. Consistent with WB, we observed significantly increased plasma CD81+ EV count and cargo at 1d post-injury. The majority of these tetraspanin EVs were smaller than 50 nm based on interferometry and were insufficiently resolved by flow cytometry-based detection. At the injury site, there was enhanced expression of EV biogenesis proteins that were also detected in EVs directly isolated from spinal cord tissue by WB. Surface expression of tetraspanins CD9 and CD63 increased in multiple cell types at the injury site; however, astrocyte CD81 expression uniquely decreased, as demonstrated by flow cytometry. UC-isolated plasma EV microRNA cargo was also significantly altered at 1d post-injury with changes similar to that reported in EVs released by astrocytes after inflammatory stimulation. When injected into the lateral ventricle, plasma EVs from SCI mice increased both pro- and anti-inflammatory gene as well as reactive astrocyte gene expression in the brain cortex. These studies provide the first detailed characterization of plasma EV dynamics after SCI and suggest that plasma EVs may be involved in posttraumatic brain inflammation.

Multidimensional review of cognitive impairment after spinal cord injury

Cognitive impairment is highly prevalent in the population with spinal cord injury (SCI) and exerts a significant impact on functional independence and quality of life in this population. A number of neuroscientists have conducted preliminary investigations of cognitive deficits after SCI, but achieved marginally contradictory results due to some limitations such as the heterogeneity in the sample population, sample size, types of tests utilized, study design, and time since SCI. Therefore, this review mainly focuses on the characteristics, assessments, potential causality and treatment of cognitive impairment for better understanding such deficits in the SCI population.

Cortical transcriptome analysis after spinal cord injury reveals the regenerative mechanism of central nervous system in CRMP2 knock-in mice

Recent studies have shown that mutation at Ser522 causes inhibition of collapsin response mediator protein 2 (CRMP2) phosphorylation and induces axon elongation and partial recovery of the lost sensorimotor function after spinal cord injury (SCI). We aimed to reveal the intracellular mechanism in axotomized neurons in the CRMP2 knock-in (CRMP2KI) mouse model by performing transcriptome analysis in mouse sensorimotor cortex using micro-dissection punching system. Prior to that, we analyzed the structural pathophysiology in axotomized or neighboring neurons after SCI and found that somatic atrophy and dendritic spine reduction in sensorimotor cortex were suppressed in CRMP2KI mice. Further analysis of the transcriptome has aided in the identification of four hemoglobin genes Hba-a1, Hba-a2, Hbb-bs, and Hbb-bt that are significantly upregulated in wild-type mice with concomitant upregulation of genes involved in the oxidative phosphorylation and ribosomal pathways after SCI. However, we observed substantial upregulation in channel activity genes and downregulation of genes regulating vesicles, synaptic function, glial cell differentiation in CRMP2KI mice. Moreover, the transcriptome profile of CRMP2KI mice has been discussed wherein energy metabolism and neuronal pathways were found to be differentially regulated. Our results showed that CRMP2KI mice displayed improved SCI pathophysiology not only via microtubule stabilization in neurons, but also possibly via the whole metabolic system in the central nervous system, response changes in glial cells, and synapses. Taken together, we reveal new insights on SCI pathophysiology and the regenerative mechanism of central nervous system by the inhibition of CRMP2 phosphorylation at Ser522. All these experiments were performed in accordance with the guidelines of the Institutional Animal Care and Use Committee at Waseda University, Japan (2017-A027 approved on March 21, 2017; 2018-A003 approved on March 25, 2018; 2019-A026 approved on March 25, 2019).

Forelimb Motor Skills Deficits Following Thoracic Spinal Cord Injury: Underlying Dopaminergic and Neural Oscillatory Changes in Rat Primary Motor Cortex

The loss of spinal sensorimotor pathways following spinal cord injury (SCI) can induce retrograde neurodegeneration in the primary motor cortex (M1). However, the effect of thoracic SCI on forelimb motor skills has not been studied clearly. So, herein we aimed to examine the effects of the thoracic SCI model on forelimb motor skills learning, parallel with dopaminergic and oscillatory changes in hindlimb and forelimb areas (HLA and FLA) of M1 in rats. Male Wistar rats were randomly subjected to laminectomy (Control) or contusion SCI at the thoracic (T10) level. Oscillatory activity and motor skills performance were evaluated for six consecutive days using local field potential (LFP) recording and skilled forelimb reaching task, respectively. Dopamine (DA) levels and expression of dopamine receptors (D1R and D2R) were determined in HLA and FLA by ELISA and western blotting. LFP recording results showed a sustained increase of LFP power in SCI rats compared with uninjured rats through skilled reaching training. Also, the SCI group had a lower reaching performance and learning rate in contrast to the Control group. Biochemical analysis of HLA and FLA showed a reduction in DA levels and expression of D1R and D2R after SCI. According to these findings, thoracic SCI causes aberrant changes in the oscillatory activity and dopaminergic system of M1, which are not restricted to HLA but also found in FLA accompanied by a deficit in forelimb motor skills performance.Summary statement: The reorganization of the primary motor cortex, following spinal cord injury, is not restricted to the hind limb area, and interestingly extends to the forelimb limb area, which appears as a dysfunctional change in oscillations and dopaminergic system, associated with a deficit in motor skills learning of forelimb.

Serum CCL21 as a Potential Biomarker for Cognitive Impairment in Spinal Cord Injury

Objective

Cognitive impairment is considered to be an important complication of spinal cord injury (SCI), but its underlying mechanism remains unclear. The purpose of this study is to explore whether serum CCL21 can be used as a potential biomarker of cognitive impairment in SCI.

Methods

In Neck-Shoulder and Lumbocrural Pain Hospital, Shandong First Medical University & Shandong Academy of Medical Sciences, hospitalized or treated acute SCI patients were included in the study as the SCI group (SCI). At the same time, a normal control group (NC) matching the age and sex of the SCI group was recruited in the outpatient clinic. Once the two groups were enrolled, their demographics and clinical characteristics were collected immediately. Enzyme-linked immunosorbent assay (ELISA) was used to detect serum CCL21 levels within 24 hours of admission. Three months later, the Montreal Cognitive Assessment (MoCA) was used to test the cognitive function of the population.

Results

A total of 84 SCI patients and 49 NC populations were eligible for inclusion in the study. There was no significant statistical difference in the demographics and clinical characteristics (age, gender, BMI, TG, LDL-C, FBG, SBP, and DBP) between the two groups (p > 0.05). Compared with the NC group, the SCI group had a higher serum CCL21 level (p < 0.001) and a lower MoCA score (p < 0.001). Serum CCL21 level in SCI was negatively correlated with MoCA score (p = 0.023). Multivariable analyses showed that serum CCL21 level is an independent prognostic factor of cognitive impairment in SCI.

Conclusions

MoCA score has a linear relationship with serum CCL21 quartile, and SCI cognitive function has a negative correlation with serum CCL21. Serum CCL21 is an independent risk factor for cognitive impairment after SCI.

Animal Models of Cerebral Changes Secondary to Spinal Cord Injury

Spinal cord injuries (SCIs) are difficult to treat. The first animal SCI model (featuring the dropping of a weight) was established by Allen in 1911, and other animal models have been developed since then. Most animal studies have focused only on the molecular features of SCIs, which remain disputed. Recently, it has become clear that SCI may trigger mental and cognitive disorders, however, and brain changes secondary to SCI are under investigation. No consensus on an optimal animal model for cerebral research has emerged. We discuss the appropriate SCI models for studying secondary brain changes.

Delayed microglial depletion after spinal cord injury reduces chronic inflammation and neurodegeneration in the brain and improves neurological recovery in male mice

Neuropsychological deficits, including impairments in learning and memory, occur after spinal cord injury (SCI). In experimental SCI models, we and others have reported that such changes reflect sustained microglia activation in the brain that is associated with progressive neurodegeneration. In the present study, we examined the effect of pharmacological depletion of microglia on posttraumatic cognition, depressive-like behavior, and brain pathology after SCI in mice.

Methods: Young adult male C57BL/6 mice were subjected to moderate/severe thoracic spinal cord contusion. Microglial depletion was induced with the colony-stimulating factor 1 receptor (CSF1R) antagonist PLX5622 administered starting either 3 weeks before injury or one day post-injury and continuing through 6 weeks after SCI. Neuroinflammation in the injured spinal cord and brain was assessed using flow cytometry and NanoString technology. Neurological function was evaluated using a battery of neurobehavioral tests including motor function, cognition, and depression. Lesion volume and neuronal counts were quantified by unbiased stereology.

Results: Flow cytometry analysis demonstrated that PLX5622 pre-treatment significantly reduced the number of microglia, as well as infiltrating monocytes and neutrophils, and decreased reactive oxygen species production in these cells from injured spinal cord at 2-days post-injury. Post-injury PLX5622 treatment reduced both CD45^int microglia and CD45^hi myeloid counts at 7-days. Following six weeks of PLX5622 treatment, there were substantial changes in the spinal cord and brain transcriptomes, including those involved in neuroinflammation. These alterations were associated with improved neuronal survival in the brain and neurological recovery.

Conclusion: These findings indicate that pharmacological microglia-deletion reduces neuroinflammation in the injured spinal cord and brain, improving recovery of cognition, depressive-like behavior, and motor function.

Tau Pathology Triggered by Spinal Cord Injury Can Play a Critical Role in the Neurotrauma Development

Traumatic spinal cord injury (SCI) can result in substantial neurological impairment along with significant emotional and psychological distress. It is clear that there is profound neurodegeneration upon SCI, gradually spread to other spinal cord regions and brain areas. Despite extensive considerations, it remains uncertain how pathogenicity diffuses in the cord. It has been reported that tau protein abnormal hyperphosphorylation plays a central role in neurodegeneration triggered by traumatic brain injury (TBI). Tau is a microtubule-associated protein, heavily implicated in neurodegenerative diseases. Importantly, tau pathology spreads in a traumatic brain in a timely manner. In particular, we have recently demonstrated that phosphorylated tau at Thr231 exists in two distinct cis and trans conformations, in which that cis P-tau is extremely neurotoxic, has a prion nature, and spreads to various brain areas and cerebrospinal fluid (CSF) upon trauma. On the other hand, tau pathology, in particular hyperphosphorylation at Thr231, has been observed upon SCI. Taken these together, we conclude that cis pT231-tau may accumulate and spread in the spinal cord as well as CSF and diffuse tau pathology in the central nervous system (CNS). Moreover, antibody against cis P-tau can target intracellular cis P-tau and protect pathology spreading. Thus, considering cis P-tau as a driver of tau pathology and neurodegeneration upon SCI would open new windows toward understanding the disease development and early biomarkers. Furthermore, it would help us develop effective therapies for SCI patients.

Reducing Neuron Apoptosis in the Pontine Micturition Center by Nerve Root Transfer for Restoration of Micturition Function after Spinal Cord Injury

Objective

The rate of neuronal apoptosis increases after spinal cord injury (SCI). Anastomosing the normal nerve roots above the SCI level to the injured sacral nerve roots can enhance the functional recovery of neurons. Therefore, we evaluated the effect of sacral nerve root transfer after SCI on pontine neuronal survival.

Methods

Sprague–Dawley rats were randomly divided into three groups: Group A, reconstruction of afferent and efferent nerve pathways of the bladder after SCI; Group B, SCI only; and Group C, control group. We examined pontine neuronal morphology using hematoxylin and eosin (H&E) staining after SCI and nerve transfer. Bcl-2 and Bax protein expression changes in the pontine micturition center were quantified by immunohistochemistry. The number of apoptotic neurons was determined by TUNEL staining. We examined pontine neuronal apoptosis by transmission electron microscopy (TEM) at different time points.

Results

H&E staining demonstrated that the number of neurons had increased in Group A, but more cells in Group B displayed nuclear pyknosis, with the disappearance of the nucleus. Compared with Group B, Group A had significantly higher Bcl-2 expression, significantly lower Bax expression, and a significantly higher Bcl-2/Bax ratio. The number of apoptotic neurons and neuron bodies in Group A was significantly lower than that in Group B, as indicated by TUNEL staining and TEM.

Conclusions

These findings demonstrate that lumbosacral nerve transfer can reduce neuronal apoptosis in the pontine micturition center and enhance functional recovery of neurons. This result further suggests that lumbosacral nerve transfer can be used as a new approach for reconstructing bladder function after spinal cord injury.

Cognitive Profiles Among Individuals With Spinal Cord Injuries: Predictors and Relations With Psychological Well-being

OBJECTIVES

To examine predictors of profiles of cognitive functioning among individuals receiving acute inpatient spinal cord injury (SCI) rehabilitation, as well as associations between their cognitive functioning and psychological well-being (life satisfaction and depression) 6 months after the baseline assessment.

DESIGN

Prospective observational study design, with 2 assessments approximately 6 months apart.

SETTING

A rehabilitation unit at a level 1 trauma hospital during acute SCI hospitalization and outpatient setting after discharge.

PARTICIPANTS

Individuals (N=89) with SCI.

INTERVENTION

None.

MAIN OUTCOME MEASURES

Cognitive functioning (assessed by the Repeatable Battery for the Assessment of Neuropsychological Status), life satisfaction (measured by the Life Satisfaction Index A), and depressive symptoms (measured by the Patient Health Questionnaire-9).

RESULTS

Latent profile analysis identified 3 classes of individuals with similar patterns of cognitive functioning: class1 (average levels of cognitive performance across all assessed domains; n=48), class 2 (average cognitive performance, except in recall and memory; n=23), and class 3 (low cognitive functioning across multiple domains of cognition; n=18). Fewer years of education, history of smoking, history of substance use other than alcohol, and greater postconcussion symptoms were associated with higher odds of classification in class 3 (P<.05). Six months post baseline, individuals in class 3 reported significantly lower levels of life satisfaction than individuals in class 1 (χ²(1)=5.86; P=.045) and marginally higher depressive symptoms than individuals in class 2 (χ²(1)=5.48; P=.057)_. CONCLUSIONS: The impact of impaired cognition during acute rehabilitation may persist after discharge and influence the psychological well-being of individuals with SCI. Identifying individuals with cognitive dysfunction and attending to modifiable risk factors and may help ameliorate maladjustment after SCI.

Vascular-Cognitive Impairment following High-Thoracic Spinal Cord Injury Is Associated with Structural and Functional Maladaptations in Cerebrovasculature

Individuals living with chronic spinal cord injury (SCI) often exhibit impairments in cognitive function, which impede their rehabilitation and transition into the community. Although a number of clinical studies have demonstrated the impact of impaired cardiovascular control on cognitive impairment, the mechanistic understanding of this deleterious relationship is still lacking. The present study investigates whether chronic disruption of cardiovascular control following experimental SCI results in cerebrovascular decline and vascular cognitive impairment. Fourteen weeks following a high thoracic SCI (at the third thoracic segment), rats were subjected to a battery of in vivo and in vitro physiological assessments, cognitive-behavioral tests, and immunohistochemical approaches to investigate changes in cerebrovascular structure and function in the middle cerebral artery (MCA). We show that in the MCA of rats with SCI, there is a 55% (SCI vs. control: 13.4 ± 1.9% vs. 29.63 ± 2.8%, respectively) reduction in the maximal vasodilator response to carbachol, which is associated with reduced expression of endothelial marker cluster of differentiation 31 (CD31) and transient receptor potential cation channel 4 (TRPV 4) channels. Compared with controls, MCAs in rats with SCI were found to have 50% (SCI vs. control: 1.5 ± 0.2 vs. 1 ± 0.1 a.u., respectively) more collagen 1 in the media of vascular wall and 37% (SCI vs. control: 30.5 ± 2.9% vs. 42.0 ± 4.0%, respectively) less distensibility at physiological intraluminal pressure. Further, the cerebral blood flow (CBF) in the hippocampus was reduced by 32% in the SCI group (SCI vs. control: 44.3 ± 4.5 mL/100 g/min vs. 65.0 ± 7.2 mL/100 g/min, respectively) in association with impairment of short-term memory based on a novel object recognition test. There were no changes in the sympathetic innervation of the vasculature and passive structure in the SCI group. Chronic experimental SCI is associated with structural alterations and endothelial dysfunction in cerebral arteries that likely contribute to significantly reduced CBF and vascular cognitive impairment.

Spinal Cord Injury Leads to Hippocampal Glial Alterations and Neural Stem Cell Inactivation

The hippocampus encodes spatial and contextual information involved in memory and learning. The incorporation of new neurons into hippocampal networks increases neuroplasticity and enhances hippocampal-dependent learning performances. Only few studies have described hippocampal abnormalities after spinal cord injury (SCI) although cognitive deficits related to hippocampal function have been reported in rodents and even humans. The aim of this study was to characterize in further detail hippocampal changes in the acute and chronic SCI. Our data suggested that neurogenesis reduction in the acute phase after SCI could be due to enhanced death of amplifying neural progenitors (ANPs). In addition, astrocytes became reactive and microglial cells increased their number in almost all hippocampal regions studied. Glial changes resulted in a non-inflammatory response as the mRNAs of the major pro-inflammatory cytokines (IL-1β, TNFα, IL-18) remained unaltered, but CD200R mRNA levels were downregulated. Long-term after SCI, astrocytes remained reactive but on the other hand, microglial cell density decreased. Also, glial cells induced a neuroinflammatory environment with the upregulation of IL-1β, TNFα and IL-18 mRNA expression and the decrease of CD200R mRNA. Neurogenesis reduction may be ascribed at later time points to inactivation of neural stem cells (NSCs) and inhibition of ANP proliferation. The number of granular cells and CA1 pyramidal neurons decreased only in the chronic phase. The release of pro-inflammatory cytokines at the chronic phase might involve neurogenesis reduction and neurodegeneration of hippocampal neurons. Therefore, SCI led to hippocampal changes that could be implicated in cognitive deficits observed in rodents and humans.