Lithium promotes recovery after spinal cord injury

Lithium is associated with oxidative stress and apoptosis,but the mechanism by which lithium protects against spinal cord injury remains poorly understood.In this study,we found that intraperitoneal administration of lithium chloride(LiCl)in a rat model of spinal cord injury alleviated pathological spinal cord injury and inhibited expression of tumor necrosis factorα,interleukin-6,and interleukin 1β.Lithium inhibited pyroptosis and reduced inflammation by inhibiting Caspase-1 expression,reducing the oxidative stress response,and inhibiting activation of the Nod-like receptor protein 3 inflammasome.We also investigated the neuroprotective effects of lithium intervention on oxygen/glucose-deprived PC12 cells.We found that lithium reduced inflammation,oxidative damage,apoptosis,and necrosis and up-regulated nuclear factor E2-related factor 2(Nrf2)and heme oxygenase-1 in PC12 cells.All-trans retinoic acid,an Nrf2 inhibitor,reversed the effects of lithium.These results suggest that lithium exerts anti-inflammatory,anti-oxidant,and anti-pyroptotic effects through the Nrf2/heme oxygenase-1 pathway to promote recovery after spinal cord injury.This study was approved by the Animal Ethics Committee of Xi’an Jiaotong University(approval No.2018-2053)on October 23,2018.     

Oscillating field stimulation promotes axon regeneration and locomotor recovery after spinal cord injury

Oscillating field stimulation(OFS)is a potential method for treating spinal cord injury.Although it has been used in spinal cord injury(SCI)therapy in basic and clinical studies,its underlying mechanism and the correlation between its duration and nerve injury repair remain poorly understood.In this study,we established rat models of spinal cord contusion at T10 and then administered 12 weeks of OFS.The results revealed that effectively promotes the recovery of motor function required continuous OFS for more than 6 weeks.The underlying mechanism may be related to the effects of OFS on promoting axon regeneration,inhibiting astrocyte proliferation,and improving the linear arrangement of astrocytes.This study was approved by the Animal Experiments and Experimental Animal Welfare Committee of Capital Medical University(supplemental approval No.AEEI-2021-204)on July 26,2021.     

Structural and functional reorganization of propriospinal connections promotes functional recovery after spinal cord injury

Axonal regeneration and fiber regrowth is limited in the adult central nervous system, but research over the last decades has revealed a high intrinsic capacity of brain and spinal cord circuits to adapt and reorganize after smaller injuries or denervation. Short-distance fiber growth and synaptic rewiring was found in cortex, brain stem and spinal cord and could be associated with restoration of sensorimotor functions that were impaired by the injury. Such processes of structural plasticity were initially observed in the corticospinal system following spinal cord injury or stroke, but recent studies showed an equally high potential for structural and functional reorganization in reticulospinal, rubrospinal or propriospinal projections. Here we review the lesion-induced plastic changes in the propriospinal pathways, and we argue that they represent a key mechanism triggering sensorimotor recovery upon incomplete spinal cord injury. The formation or strengthening of spinal detour pathways bypassing supraspinal commands around the lesion site to the denervated spinal cord were identified as prominent neural substrate inducing substantial motor recovery in different species from mice to primates. Indications for the existence of propriospinal bypasses were also found in humans after cortical stroke. It is mandatory for current research to dissect the biological mechanisms underlying spinal circuit remodeling and to investigate how these processes can be stimulated in an optimal way by therapeutic interventions(e.g., fiber-growth enhancing interventions, rehabilitation). This knowledge will clear the way for the development of novel strategies targeting the remarkable plastic potential of propriospinal circuits to maximize functional recovery after spinal cord injury.     

LINGO-1 antagonist promotes functional recovery and axonal sprouting after spinal cord injury

LINGO-1 is a CNS-specific protein and a functional component of the NgR1/p75/LINGO-1 and NgR1/TAJ(TROY)/LINGO-1 signaling complexes that mediate inhibition of axonal outgrowth. These receptor complexes mediate the axonal growth inhibitory effects of Nogo, myelin-associated glycoprotein (MAG) and oligodendrocyte-myelin glycoprotein (OMgp) via RhoA activation. Soluble LINGO-1 (LINGO-1-Fc), which acts as an antagonist of these pathways by blocking LINGO-1 binding to NgR1, was administered to rats after dorsal or lateral hemisection of the spinal cord. LINGO-1-Fc treatment significantly improved functional recovery, promoted axonal sprouting and decreased RhoA activation and increased oligodendrocyte and neuronal survival after either rubrospinal or corticospinal tract transection. These experiments demonstrate an important role for LINGO-1 in modulating axonal outgrowth in vivo and that treatment with LINGO-1-Fc can significantly enhance recovery after spinal cord injury.     

Hepatocyte growth factor promotes endogenous repair and functional recovery after spinal cord injury

Many therapeutic interventions using neurotrophic factors or pharmacological agents have focused on secondary degeneration after spinal cord injury (SCI) to reduce damaged areas and promote axonal regeneration and functional recovery. Hepatocyte growth factor (HGF), which was identified as a potent mitogen for mature hepatocytes and a mediator of inflammatory responses to tissue injury, has recently been highlighted as a potent neurotrophic and angiogenic factor in the central nervous system (CNS). In the present study, we revealed that the extent of endogenous HGF up-regulation was less than that of c-Met, an HGF receptor, during the acute phase of SCI and administered exogenous HGF into injured spinal cord using a replication-incompetent herpes simplex virous-1 (HSV-1) vector to determine whether HGF exerts beneficial effects and promotes functional recovery after SCI. This treatment resulted in the significant promotion of neuron and oligodendrocyte survival, angiogenesis, axonal regrowth, and functional recovery after SCI. These results suggest that HGF gene delivery to the injured spinal cord exerts multiple beneficial effects and enhances endogenous repair after SCI. This is the first study to demonstrate the efficacy of HGF for SCI.     

Scaffoldless tissue-engineered nerve conduit promotes peripheral nerve regeneration and functional recovery after tibial nerve injury in rats

Damage to peripheral nerve tissue may cause loss of function in both the nerve and the targeted muscles it innervates. This study compared the repair capability of engineered nerve conduit (ENC), engineered fibroblast conduit (EFC), and autograft in a 10-mm tibial nerve gap. ENCs were fabricated utilizing primary fibroblasts and the nerve cells of rats on embryonic day 15 (E15). EFCs were fabricated utilizing primary fi-broblasts only. Following a 12-week recovery, nerve repair was assessed by measuring contractile properties in the medial gastrocnemius muscle, distal motor nerve conduction velocity in the lateral gastrocnemius, and histology of muscle and nerve. The autografts, ENCs and EFCs reestablished 96%, 87% and 84% of native distal motor nerve conduction velocity in the lateral gastrocnemius, 100%, 44% and 44% of native specific force of medical gastrocnemius, and 63%, 61% and 67% of native medial gastrocnemius mass, re-spectively. Histology of the repaired nerve revealed large axons in the autograft, larger but fewer axons in the ENC repair, and many smaller axons in the EFC repair. Muscle histology revealed similar muscle fiber cross-sectional areas among autograft, ENC and EFC repairs. In conclusion, both ENCs and EFCs promot-ed nerve regeneration in a 10-mm tibial nerve gap repair, suggesting that the E15 rat nerve cells may not be necessary for nerve regeneration, and EFC alone can suffice for peripheral nerve injury repair.     

Valproic acid reduces autophagy and promotes functional recovery after spinal cord injury in rats

Secondary damage is a critical determinant of the functional outcome in patients with spinal cord injury (SCI), and involves multiple mechanisms of which the most important is the loss of nerve cells mediated by multiple factors. Autophagy can result in cell death, and plays a key role in the development of SCI. It has been recognized that valproic acid (VPA) is neuroprotective in certain experimental animal models, however, the levels of autophagic changes in the process of neuroprotection by VPA treatment following SCI are still unknown. In the present study, we determined the extent of autophagy after VPA treatment in a rat model of SCI. We found that both the mRNA and protein levels of Beclin-1 and LC3 were significantly increased at 1, 2, and 6 h after SCI and peaked at 2 h; however, Western blot showed that autophagy was markedly decreased by VPA treatment at 2 h post-injury. Besides, post-SCI treatment with VPA improved the Basso-Beattie-Bresnahan scale, increased the number of ventral horn motoneurons, and reduced myelin sheath damage compared with vehicle-treated animals at 42 days after SCI. Together, our results demonstrated the characteristics of autophagy expression following SCI, and found that VPA reduced autophagy and enhanced motor function.     

Major vault protein promotes locomotor recovery and regeneration after spinal cord injury in adult zebrafish

In contrast to mammals, adult zebrafish recover locomotor functions after spinal cord injury (SCI), in part due to axonal regrowth and regeneration permissivity of the central nervous system. Upregulation of major vault protein (MVP) expression after spinal cord injury in the brainstem of the adult zebrafish prompted us to probe for its contribution to recovery after SCI. MVP is a multifunctional protein expressed not only in many types of tumours but also in the nervous system, where its importance for regeneration is, however, unclear. Using an established zebrafish SCI model, we found that MVP mRNA and protein expression levels were increased in ependymal cells in the spinal cord caudal to the lesion site at 6 and 11 days after SCI. Double immunolabelling showed that MVP was co‐localised with Islet‐1 or tyrosine hydroxylase around the central canal of the spinal cord in sham‐injured control fish and injured fish 11 days after surgery. MVP co‐localised with the neural stem cell marker nestin in ependymal cells after injury. By using an in vivo morpholino‐based knock‐down approach, we found that the distance moved by MVP morpholino‐treated fish was reduced at 4, 5 and 6 weeks after SCI when compared to fish treated with standard control morpholino. Knock‐down of MVP resulted in reduced regrowth of axons from brainstem neurons into the spinal cord caudal to the lesion site. These results indicate that MVP supports locomotor recovery and axonal regrowth after SCI in adult zebrafish.     

Inhibition of EphA7 up-regulation after spinal cord injury reduces apoptosis and promotes locomotor recovery

Functional impairment after spinal cord injury (SCI) is partially attributed to neuronal cell death, with further degeneration caused by the accompanying apoptosis of myelin-forming oligodendrocytes. The Eph receptor protein tyrosine kinase family and its cognate ligands, the ephrins, have been identified to be involved in axonal outgrowth, synapse formation, and target recognition, mainly mediated by repulsive activity. Recent reports suggest that ephrin/Eph signaling might also play a role as a physiological trigger for apoptosis during embryonic development. Here, we investigated the expression profile of EphA7, after SCI, by using a combination of quantitative real-time PCR (QRT-PCR) and immunohistochemical techniques. QRT-PCR analysis showed an increase in the expression of full-length EphA7 at 7 days postinjury (DPI). Receptor immunoreactivity was shown mostly in astrocytes of the white matter at the injury epicenter. In control animals, EphA7 expression was observed predominantly in motor neurons of the ventral gray matter, although some immunoreactivity was seen in white matter. Furthermore, blocking the expression of EphA7 after SCI using antisense oligonucleotides resulted in significant acceleration of hindlimb locomotor recovery at 1 week. This was a transient effect; by 2 weeks postinjury, treated animals were not different from controls. Antisense treatment also produced a return of nerve conduction, with shorter latencies than in control treated animals after transcranial magnetic stimulation. We identified EphA7 receptors as putative regulators of apoptosis in the acute phase after SCI. These results suggest a functional role for EphA7 receptors in the early stages of SCI pathophysiology.     

Recombinant human fibroblast growth factor-2 promotes nerve regeneration and functional recovery after mental nerve crush injury

Several studies have shown that fibroblast growth factor-2(FGF2) can directly affect axon regeneration after peripheral nerve damage. In this study, we performed sensory tests and histological analyses to study the effect of recombinant human FGF-2(rh FGF2) treatment on damaged mental nerves. The mental nerves of 6-week-old male Sprague-Dawley rats were crush-injured for 1 minute and then treated with 10 or 50 μg/m L rh FGF2 or PBS in crush injury area with a mini Osmotic pump. Sensory test using von Frey filaments at 1 week revealed the presence of sensory degeneration based on decreased gap score and increased difference score. However, at 2 weeks, the gap score and difference score were significantly rebounded in the mental nerve crush group treated with 10 μg/m L rh FGF2. Interestingly, treatment with 10 μg/m L rh FGF had a more obviously positive effect on the gap score than treatment with 50 μg/m L rh FGF2. In addition, retrograde neuronal tracing with Dil revealed a significant increase in nerve regeneration in the trigeminal ganglion at 2 and 4 weeks in the rh FGF2 groups(10 μg/m L and 50 μg/m L) than in the PBS group. The 10 μg/m L rh FGF2 group also showed an obviously robust regeneration in axon density in the mental nerve at 4 weeks. Our results demonstrate that 10 μg/m L rh FGF induces mental nerve regeneration and sensory recovery after mental nerve crush injury.     

Edaravone promotes functional recovery after mechanical peripheral nerve injury

Edaravone has been shown to reduce ischemia/reperfusion-induced peripheral nerve injury. However, the therapeutic effect of edaravone on peripheral nerve injury caused by mechanical factors is unknown. In the present study, we established a peripheral nerve injury model by crushing the sciatic nerve using hemostatic forceps, and then administered edaravone 3 mg/kg intraperitoneally. The sciatic functional index and superoxide dismutase activity of the sciatic nerve were increased, and the malondialdehyde level was decreased in animals in the edaravone group compared with those in the model group. Bcl-2 expression was increased, but Bax expression was decreased in anterior horn cells of the L4–6 spinal cord segments. These results indicated that edaravone has a neuroprotective effect following peripheral nerve injury caused by mechanical factors through alleviating free radical damage to cells and inhibiting lipid peroxidation, as well as regulating apoptosis-related protein expression.     

Nimodipine promotes regeneration and functional recovery after intracranial facial nerve crush

The calcium flow inhibitor, nimodipine, has been shown to promote motor neuron survival in the facial nucleus after intracranial facial nerve transection. However, it has not been known whether the neuroprotective effects primarily involve survival of nerve cell bodies or outgrowth and/or myelination of nerve fibers. Here, we studied the effects of nimodipine in a different injury model in which the facial nerve was unilaterally crushed intracranially. This lesion caused complete anterograde degeneration and partial retrograde degeneration that were studied with a combination of several stereological methods. Nimodipine did not attenuate the modest lesion-induced neuronal loss (13%) but accelerated the time course of functional recovery and axonal regrowth, inducing increased numbers and sizes of myelinated axons in the facial nerve. It is interesting to note that nimodipine also enlarged the axons and the myelin sheaths in the nonlesioned facial nerve, which points to the possibility of using this substance for new clinical applications to promote axonal growth and remyelination.     

Miconazole enhances nerve regeneration and functional recovery after sciatic nerve crush injury

Introduction: Improving axonal outgrowth and remyelination is crucial for peripheral nerve regeneration. Miconazole appears to enhance remyelination in the central nervous system. In this study we assess the effect of miconazole on axonal regeneration using a sciatic nerve crush injury model in rats. Methods: Fifty Sprague‐Dawley rats were divided into control and miconazole groups. Nerve regeneration and myelination were determined using histological and electrophysiological assessment. Evaluation of sensory and motor recovery was performed using the pinprick assay and sciatic functional index. The Cell Counting Kit‐8 assay and Western blotting were used to assess the proliferation and neurotrophic expression of RSC 96 Schwann cells. Results: Miconazole promoted axonal regrowth, increased myelinated nerve fibers, improved sensory recovery and walking behavior, enhanced stimulated amplitude and nerve conduction velocity, and elevated proliferation and neurotrophic expression of RSC 96 Schwann cells. Discussion: Miconazole was beneficial for nerve regeneration and functional recovery after peripheral nerve injury. Muscle Nerve 57 : 821–828, 2018     

Reorganization of spinal neural circuitry and functional recovery after spinal cord injury

<正>The ability of the adult central nervous system to reorganize its circuits over time is the key to understand the functional improvement in subjects with spinal cord injury(SCI).Adaptive changes within spared neuronal circuits may occur at cortical,brainstem,or spinal cord level,both above and below a spinal lesion(Bareyre et al.,2004).At each level the reorganization is a very dynamic process,and its degree is highly variable,depending on several factors,including the age of the     

Inflammation and its role in neuroprotection, axonal regeneration and functional recovery after spinal cord injury

Trauma to the central nervous system (CNS) triggers intraparenchymal inflammation and activation of systemic immunity with the capacity to exacerbate neuropathology and stimulate mechanisms of tissue repair. Despite our incomplete understanding of the mechanisms that control these divergent functions, immune-based therapies are becoming a therapeutic focus. This review will address the complexities and controversies of post-traumatic neuroinflammation, particularly in spinal cord. In addition, current therapies designed to target neuroinflammatory cascades will be discussed.     

Blocking connexin43 expression reduces inflammation and improves functional recovery after spinal cord injury

After traumatic CNS injury, a cascade of secondary events expands the initial lesion. The gap-junction protein connexin43 (Cx43), which is transiently up-regulated, has been implicated in the spread of 'bystander' damage. We have used an antisense oligodeoxynucleotide (asODN) to suppress Cx43 up-regulation in two rat models of spinal cord injury. Within 24 h of compression injury, rats treated with Cx43-asODN scored higher than sense-ODN and vehicle-treated controls on behavioural tests of locomotion. Their spinal cords showed less swelling and tissue disruption, less up-regulation of astrocytic GFAP, and less extravasation of fluorescently-labelled bovine serum albumin and neutrophils. The locomotor improvement was sustained over at least 4 weeks. Following partial spinal cord transection, Cx43-asODN treatment reduced GFAP immunoreactivity, neutrophil recruitment, and the activity of OX42(+) microglia in and around the lesion site. Cx43 has many potential roles in the pathophysiology of CNS injury and may be a valuable target for therapeutic intervention.     

Granulocyte colony-stimulating factor attenuates neuronal death and promotes functional recovery after spinal cord injury in mice

Granulocyte colony-stimulating factor (G-CSF) is a protein that stimulates differentiation, proliferation, and survival of granulocytic lineage cells. Recently, a neuroprotective effect of G-CSF was reported in a model of cerebral infarction. The aim of the present study was to elucidate the potential therapeutic effect of G-CSF for spinal cord injury (SCI) in mice. We found that G-CSF is neuroprotective against glutamate-induced cell death of cerebellar granule neurons in vitro. Moreover, we used a mouse model of compressive SCI to examine the neuroprotective potential of G-CSF in vivo. Histologic assessment with cresyl violet staining revealed that the number of surviving neurons in the injured spinal cord was significantly increased in G-CSF-treated mice. Immunohistochemistry for neuronal apoptosis revealed that G-CSF suppressed neuronal apoptosis after SCI. Moreover, administration of G-CSF promoted hindlimb functional recovery. Examination of signaling pathways downstream of the G-CSF receptor suggests that G-CSF might promote functional recovery by inhibiting neuronal apoptosis after SCI. G-CSF is currently used in the clinic for hematopoietic stimulation, and its ongoing clinical trial for brain infarction makes it an appealing molecule that could be rapidly placed into trials for patients with acute SCI.     

Dietary restriction started after spinal cord injury improves functional recovery

Spinal cord injury typically results in limited functional recovery. Here we investigated whether therapeutic dietary restriction, a multi-faceted, safe, and clinically-feasible treatment, can improve outcome from cervical spinal cord injury. The well-established notion that dietary restriction increases longevity has kindled interest in its potential benefits in injury and disease. When followed for several months prior to insult, prophylactic dietary restriction triggers multiple molecular responses and improves outcome in animal models of stroke and myocardial infarction. However, the efficacy of the clinically-relevant treatment of post-injury dietary restriction is unknown. Here we report that “every-other-day fasting” (EODF), a form of dietary restriction, implemented after rat cervical spinal cord injury was neuroprotective, promoted plasticity, and improved behavioral recovery. Without causing weight loss, EODF improved gait-pattern, forelimb function during ladder-crossing, and vertical exploration. In agreement, EODF preserved neuronal integrity, dramatically reduced lesion volume by > 50%, and increased sprouting of corticospinal axons. As expected, blood β-hydroxybutyrate levels, a ketone known to be neuroprotective, were increased by 2–3 fold on the fasting days. In addition, we found increased ratios of full-length to truncated trkB (receptor for brain-derived neurotrophic factor) in the spinal cord by 2–6 folds at both 5 days (lesion site) and 3 weeks after injury (caudal to lesion site) which may further enhance neuroprotection and plasticity. Because EODF is a safe, non-invasive, and low-cost treatment, it could be readily translated into the clinical setting of spinal cord injury and possibly other insults.     

Chondroitinase ABC promotes axonal regeneration of Clarke's neurons after spinal cord injury

We examined whether enzymatic digestion of chondroitin sulfate (CS) promoted the axonal regeneration of neurons in Clarke's nucleus (CN) into a peripheral nerve (PN) graft following injury of the spinal cord. After hemisection at T11, a segment of PN graft was implanted at the lesion site. Either vehicle, brain-derived neurotrophic factor (BDNF) or chondroitinase ABC was applied at the implantation site. The postoperative survival period was 4 weeks. Treatment with vehicle or BDNF did not promote the axonal regeneration of CN neurons into the PN graft. Application of 2.5 unit/ml chondroitinase ABC resulted in a significant increase (12.8%) in the number of regenerated CN neurons. Double labeling with Fluoro-Gold and NADPH-diaphorase histochemistry showed that the regenerated CN neurons did not express nitric oxide synthase (NOS). Our results suggest that CS is inhibitory to the regeneration of CN neurons following injury of the spinal cord.