Lentiviral-Mediated Netrin-1 Overexpression Improves Motor and Sensory Functions in SCT Rats Associated with SYP and GAP-43 Expressions

Spinal cord injury (SCI), as a major cause of disability, usually causes serious loss of motor and sensory functions. As a bifunctional axonal guidance cue, netrin-1 can attract axons via the deleted in colorectal cancer (DCC) receptors and repelling others via Unc5 receptors, but its exact role in the recovery of motor and sensory function has not well been studied, and the mechanisms remains elusive. The aim of this experiment is to determine whether lentiviral (LV)-mediated overexpression of netrin-1 or RNA interference (RNAi) can regulate the functional recovery in rats subjected to spinal cord transection (SCT). Firstly, two lentiviral vectors including Lv-exNtn-1 (netrin-1 open reading frame (ORF)) and Lv-shNtn-1 (netrin-1 sh) were constructed and injected into spinal cords rostral and caudal to the transected lesion site. Overexpressing netrin-1 enhanced significantly locomotor function, and reduced thermal and mechanical stimuli in vivo, compared with the control, while silencing netrin-1 did not significantly change the situation. Western blot and immunostaining analysis confirmed that netrin-1 ORF treatment not only effectively increased the expression level of netrin-1, also up-regulated the level of synaptophysin (SYP) in spinal cord rostral to the lesion, but also enhanced growth-associated protein-43 (GAP-43) expression in spinal cord caudal to the lesion site. Comparatively, knockdown of netrin-1 did not give rise to positive findings in our experimental condition. These findings therefore pointed that Lv-mediated netrin-1 overexpression could promote motor and sensory functional recoveries following SCT, and the underlying mechanisms were associated with SYP and GAP-43 expressions. The present study therefore provided a novel strategy for the treatment of SCI and explained the possible mechanisms for the functional improvement.     

Sox11 promotes endogenous neurogenesis and locomotor recovery in mice spinal cord injury

We introduced a lentiviral vector containing the Sox11 gene into injured spinal cords of mice to evaluate the therapeutic potential of Sox11 in spinal cord injury. Sox11 markedly improved locomotor recovery after spinal cord injury and this recovery was accompanied by an up-regulation of Nestin/Doublecortin expression in the injured spinal cord. Sox11 was mainly located in endogenous neural stem cells lining the central canal and in newly-generated neurons in the spinal cord. In addition, Sox 11 significantly induced expressions of BDNF in the spinal cords of LV-Sox11-treated mice. We concluded that Sox11 induced activation of endogenous neural stem cells into neuronal determination and migration within the injured spinal cord. The resultant increase of BDNF at the injured site might form a distinct neurogenic niche which induces a final neuronal differentiation of these neural stem cells. Enhancing Sox11 expression to induce neurogenic differentiation of endogenous neural stem cells after injury may be a promising strategy in restorative therapy after SCI in mammals.     

Development of protective autoimmunity by immunization with a neural-derived peptide is ineffective in severe spinal cord injury

Protective autoimmunity (PA) is a physiological response to central nervous system trauma that has demonstrated to promote neuroprotection after spinal cord injury (SCI). To reach its beneficial effect, PA should be boosted by immunizing with neural constituents or neural-derived peptides such as A91. Immunizing with A91 has shown to promote neuroprotection after SCI and its use has proven to be feasible in a clinical setting. The broad applications of neural-derived peptides make it important to determine the main features of this anti-A91 response. For this purpose, adult Sprague-Dawley rats were subjected to a spinal cord contusion (SCC; moderate or severe) or a spinal cord transection (SCT; complete or incomplete). Immediately after injury, animals were immunized with PBS or A91. Motor recovery, T cell-specific response against A91 and the levels of IL-4, IFN-γ and brain-derived neurotrophic factor (BDNF) released by A91-specific T (T(A91)) cells were evaluated. Rats with moderate SCC, presented a better motor recovery after A91 immunization. Animals with moderate SCC or incomplete SCT showed significant T cell proliferation against A91 that was characterized chiefly by the predominant production of IL-4 and the release of BDNF. In contrast, immunization with A91 did not promote a better motor recovery in animals with severe SCC or complete SCT. In fact, T cell proliferation against A91 was diminished in these animals. The present results suggest that the effective development of PA and, consequently, the beneficial effects of immunizing with A91 significantly depend on the severity of SCI. This could mainly be attributed to the lack of T(A91) cells which predominantly showed to have a Th2 phenotype capable of producing BDNF, further promoting neuroprotection.     

Transplantation of mature adipocyte-derived dedifferentiated fat cells promotes locomotor functional recovery by remyelination and glial scar reduction after spinal cord injury in mice

Mature adipocyte-derived dedifferentiated fat cells (DFAT) have a potential to be useful as new cell-source for cell-based therapy for spinal cord injury (SCI), but the mechanisms remain unclear. The objective of this study was to examine whether DFAT-induced functional recovery is achieved through remyelination and/or glial scar reduction in a mice model of SCI. To accomplish this we subjected adult female mice (n = 22) to SCI. On the 8th day post-injury locomotor tests were performed, and the mice were randomly divided into two groups (control and DFAT). The DFAT group received stereotaxic injection of DFAT, while the controls received DMEM medium. Functional tests were conducted at repeated intervals, until the 36th day, and immunohistochemistry or staining was performed on the spinal cord sections. DFAT transplantation significantly improved locomotor function of their hindlimbs, and promoted remyelination and glial scar reduction, when compared to the controls. There were significant and positive correlations between promotion of remyelination or/and reduction of glial scar, and recovery of locomotor function. Furthermore, transplanted DFAT expressed markers for neuron, astrocyte, and oligodendrocyte, along with neurotrophic factors, within the injured spinal cord. In conclusion, DFAT-induced functional recovery in mice after SCI is probably mediated by both cell-autonomous and cell-non-autonomous effects on remyelination of the injured spinal cord.     

Naringin Treatment Improves Functional Recovery by Increasing BDNF and VEGF Expression, Inhibiting Neuronal Apoptosis After Spinal Cord Injury

The aim of this study was to determine the therapeutic efficacy of starting naringin treatment 1 day after spinal cord injury (SCI) in rat and to investigate the underlying mechanism. SCI was induced using the modified weight-drop method in Sprague-Dawley rats. The SCI animals were randomly divided into three groups: vehicle-treated group; 20 mg/kg naringin-treated group; 40 mg/kg naringin-treated group, and additionally with sham group (laminectomy only). Locomotors functional recovery was assessed during the 6 weeks post operation period by performing open-field locomotors tests and inclined-plane tests. At the end of the study, the segments of spinal cord encompassing the injury site were removed for histopathological analysis. Immunohistochemistry was performed to observe the expression of the brain-derived neurotrophic factor (BDNF). The expression of vascular endothelial growth factor (VEGF), B-cell CLL/lymphoma-2 (Bcl-2), BCL-2-associated X protein (Bax) and caspase-3 were detected by Western blot analysis. The apoptotic neural cells were assessed using the TUNEL method. The results showed that the naringin-treated animals had significantly better locomotor function recovery, less myelin loss, and higher expression of BDNF and VEGF. In addition, naringin treatment significantly increased in Bcl-2:Bax ratio, reduced the enzyme activity of caspase-3 and decreased the number of apoptotic cells after SCI. These findings suggest that naringin treatment starting 1 day after SCI can significantly improve locomotor recovery, and this neuroprotective effect may be related to the upregulation of BDNF and VEGF and the inhibition of neural apoptosis. Therefore, naringin may be useful as a promising therapeutic agent for SCI.     

Intrathecal Epigallocatechin Gallate Treatment Improves Functional Recovery After Spinal Cord Injury by Upregulating the Expression of BDNF and GDNF

This study aimed to investigate the therapeutic effects of epigallocatechin-3-gallate (EGCG) administered by subarachnoid injection following spinal cord injury (SCI) in rats and to explore the underlying mechanism. Sprague–Dawley rats were randomly divided into four groups of 12 as follows: a sham group (laminectomy only); a control group; a 10 mg/kg EGCG-treated group; and a 20 mg/kg EGCG-treated group. SCI was induced in the rats using the modified weight-drop method (10 g × 4 cm) at the T10 (10th thoracic vertebral) level. EGCG (10 or 20 mg/kg) or vehicle as control was administered by subarachnoid injection at lumbar level 4 immediately after SCI. Locomotor functional recovery was assessed during the four weeks post-operation using open-field locomotor tests and inclined-plane tests. At the end of the study, the segments of spinal cord encompassing the injury site were removed for histopathological analysis. Immunohistochemical and Western blot analyses were performed to observe the expression of: the B cell CLL/lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax), brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF). The results showed that the EGCG-treated animals had significantly better recovery of locomotor function, less myelin loss, greater Bcl-2 expression and attenuated Bax expression. In addition, the EGCG treatment significantly increased the expression of BDNF and GDNF after SCI. These findings suggest that EGCG treatment can significantly improve locomotor recovery, and this neuroprotective effect may be related to the up-regulation of BDNF and GDNF, and the inhibition of apoptosis-related proteins. Therefore, EGCG may be a promising therapeutic agent for SCI.     

Amphetamine-induced locomotion and gene expression are altered in BDNF heterozygous mice

Administration of amphetamine overstimulates medium spiny neurons (MSNs) by releasing dopamine and glutamate from afferents in the striatum. However, these afferents also release brain-derived neurotrophic factor (BDNF) that protects striatal MSNs from overstimulation. Intriguingly, all three neurochemicals increase opioid gene expression in MSNs. In contrast, striatal opioid expression is less in naive BDNF heterozygous (BDNF(+/-)) vs. wild-type (WT) mice. This study was designed to determine whether partial genetic depletion of BDNF influences the behavioral and molecular response to an acute amphetamine injection. An acute injection of amphetamine [5 mg/kg, intraperitoneal (i.p.)] or saline was administered to WT and BDNF(+/-) mice. WT and BDNF(+/-) mice exhibited similar locomotor activity during habituation, whereas BDNF(+/-) mice exhibited more prolonged locomotor activation during the third hour after injection of amphetamine. Three hours after amphetamine injection, there was an increase of preprodynorphin mRNA in the caudate putamen and nucleus accumbens (Acb) and dopamine D(3) receptor mRNA levels were increased in the Acb of BDNF(+/-) and WT mice. Striatal/cortical trkB and BDNF, and mesencephalic tyrosine hydroxylase mRNA levels were only increased in WT mice. These results indicate that BDNF modifies the locomotor responses of mice to acute amphetamine and differentially regulates amphetamine-induced gene expression.     

MicroRNA-26b inhibits oligodendrocyte precursor cell differentiation by targeting adrenomedullin in spinal cord injury

Oligodendrocyte precursor cells (OPCs) serve as a reservoir of newborn oligodendrocytes (OLs) in pathological and homeostatic conditions. After spinal cord injury (SCI), OPCs are activated to generate myelinating OLs, contributing to remyelination and functional recovery; however, the underlying molecular mechanisms remain unclear. Here, microRNA-26b (miR-26b) expression in the spinal cord tissues of SCI rats was examined by real-time polymerase chain reaction analysis. The influences of miR-26b on locomotor recovery following SCI were assessed utilizing Basso, Beattie, and Bresnahan (BBB) scores. The effects of miR-26b on OPC differentiation were explored using immunofluorescence and western blot analyses in vitro and in vivo. The potential targets that are modulated by miR-26b were identified by bioinformatics, luciferase reporter assays, and western blot analyses. The effects of adrenomedullin (ADM) on OPC differentiation were explored in vitro using immunofluorescence and western blot analyses. We demonstrated that miR-26b was significantly downregulated after SCI. BBB scores showed that miR-26b exacerbated the locomotor function deficits induced by SCI. In vitro, miR-26b inhibited the differentiation of primary rat OPCs. In vivo, miR-26b suppressed OPC differentiation in SCI rats. Bioinformatics analyses and experimental detection revealed that miR-26b directly targeted ADM in OPCs. In addition, knockdown of ADM suppressed the differentiation of primary rat OPCs. Our study provides evidence that ADM may mediate miR-26b-inhibited OPC differentiation in SCI.     

Transplants of Human Mesenchymal Stem Cells Improve Functional Recovery After Spinal Cord Injury in the Rat

Human mesenchymal stem cells (hMSCs) derived from adult bone marrow represent a potentially useful source of cells for cell replacement therapy after nervous tissue damage. They can be expanded in culture and reintroduced into patients as autografts or allografts with unique immunologic properties. The aim of the present study was to investigate (i) survival, migration, differentiation properties of hMSCs transplanted into non-immunosuppressed rats after spinal cord injury (SCI) and (ii) impact of hMSC transplantation on functional recovery. Seven days after SCI, rats received i.v. injection of hMSCs (2×10⁶ in 0.5 mL DMEM) isolated from adult healthy donors. Functional recovery was assessed by Basso–Beattie–Bresnahan (BBB) score weekly for 28 days. Our results showed gradual improvement of locomotor function in transplanted rats with statistically significant differences at 21 and 28 days. Immunocytochemical analysis using human nuclei (NUMA) and BrdU antibodies confirmed survival and migration of hMSCs into the injury site. Transplanted cells were found to infiltrate mainly into the ventrolateral white matter tracts, spreading also to adjacent segments located rostro-caudaly to the injury epicenter. In double-stained preparations, hMSCs were found to differentiate into oligodendrocytes (APC), but not into cells expressing neuronal markers (NeuN). Accumulation of GAP-43 regrowing axons within damaged white matter tracts after transplantation was observed. Our findings indicate that hMSCs may facilitate recovery from spinal cord injury by remyelinating spared white matter tracts and/or by enhancing axonal growth. In addition, low immunogenicity of hMSCs was confirmed by survival of donor cells without immunosuppressive treatment.     

Early Endogenous Activation of CB1 and CB2 Receptors after Spinal Cord Injury Is a Protective Response Involved in Spontaneous Recovery

Spinal cord injury (SCI) induces a cascade of processes that may further expand the damage (secondary injury) or, alternatively, may be part of a safeguard response. Here we show that after a moderate-severe contusive SCI in rats there is a significant and very early increase in the spinal cord content of the endocannabinoids 2-arachidonoylglycerol (2-AG) and arachidonoyl ethanolamide (anandamide, AEA). Since 2-AG and AEA act through CB1 and CB2 cannabinoid receptors, we administered at 20 minutes after lesion a single injection of their respective antagonists AM281 and AM630 alone or in combination to block the effects of this early endocannabinoid accumulation. We observed that AM281, AM630 or AM281 plus AM630 administration impairs the spontaneous motor recovery of rats according to the Basso-Beattie-Bresnahan (BBB) locomotor scale. However, blockade of CB1, CB2 or both receptors produced different effects at the histopathological level. Thus, AM630 administration results at 90 days after lesion in increased MHC-II expression by spinal cord microglia/monocytes and reduced number of serotoninergic fibres in lumbar spinal cord (below the lesion). AM281 exerted the same effects but also increased oedema volume estimated by MRI. Co-administration of AM281 and AM630 produced the effects observed with the administration of either AM281 or AM630 and also reduced white matter and myelin preservation and enhanced microgliosis in the epicentre. Overall, our results suggest that the endocannabinoids acting through CB1 and CB2 receptors are part of an early neuroprotective response triggered after SCI that is involved in the spontaneous recovery after an incomplete lesion.     

Knockdown of α-synuclein in cerebral cortex improves neural behavior associated with apoptotic inhibition and neurotrophin expression in spinal cord transected rats

Spinal cord injury (SCI) often causes severe functional impairment with poor recovery. The treatment, however, is far from satisfaction, and the mechanisms remain unclear. By using proteomics and western blot, we found spinal cord transection (SCT) resulted in a significant down-regulation of α-synuclein (SNCA) in the motor cortex of SCT rats at 3 days post-operation. In order to detect the role of SNCA, we used SNCA-ORF/shRNA lentivirus to upregulate or knockdown SNCA expression. In vivo, SNCA-shRNA lentivirus injection into the cerebral cortex motor area not only inhibited SNCA expression, but also significantly enhanced neurons’ survival, and attenuated neuronal apoptosis, as well as promoted motor and sensory function recovery in hind limbs. While, overexpression SNCA exhibited the opposite effects. In vitro, cortical neurons transfected with SNCA-shRNA lentivirus gave rise to an optimal neuronal survival and neurite outgrowth, while it was accompanied by reverse efficiency in SNCA-ORF group. In molecular level, SNCA silence induced the upregulation of Bcl-2 and the downregulation of Bax, and the expression of NGF, BDNF and NT3 was substantially upregulated in cortical neurons. Together, endogenous SNCA play a crucial role in motor and sensory function regulation, in which, the underlying mechanism may be linked to the regulation of apoptosis associated with apoptotic gene (Bax, Bcl2) and neurotrophic factors expression (NGF, BDNF and NT3). These finds provide novel insights to understand the role of SNCA in cerebral cortex after SCT, and it may be as a novel treatment target for SCI repair in future clinic trials.     

Adipose-Derived Stem Cells Expressing the Neurogenin-2 Promote Functional Recovery After Spinal Cord Injury in Rat

Neurogenin2 (Ngn2) is a proneural gene that directs neuronal differentiation of progenitor cells during development. This study aimed to investigate whether the use of adipose-derived stem cells (ADSCs) over-expressing the Ngn2 transgene (Ngn2–ADSCs) could display the characteristics of neurogenic cells and improve functional recovery in an experimental rat model of SCI. ADSCs from rats were cultured and purified in vitro, followed by genetically modified with the Ngn2 gene. Forty-eight adult female Sprague–Dawley rats were randomly assigned to three groups: the control, ADSCs, and Ngn2–ADSCs groups. The hind-limb motor function of all rats was recorded using the Basso, Beattie, and Bresnahan locomotor rating scale for 8 weeks. Moreover, hematoxylineosin staining and immunohistochemistry were also performed. After neural induction, positive expression rate of NeuN in Ngn2–ADSCs group was upon 90 %. Following transplantation, a great number of ADSCs was found around the center of the injury spinal cord at 1 and 4 weeks, which improved retention of tissue at the lesion site. Ngn2–ADSCs differentiated into neurons, indicated by the expression of neuronal markers, NeuN and Tuj1. Additionally, transplantation of Ngn2–ADSCs upregulated the trophic factors (brain-derived neurotrophic factor and vascular endothelial growth factor), and inhibited the glial scar formation, which was indicated by immunohistochemistry with glial fibrillary acidic protein. Finally, Ngn2–ADSCs-treated animals showed the highest functional recovery among the three groups. These findings suggest that transplantation of Ngn2-overexpressed ADSCs promote the functional recovery from SCI, and improve the local microenvironment of injured cord in a more efficient way than that with ADSCs alone.     

Receptor for Advanced Glycation End-Products (RAGE) Blockade Do Damage to Neuronal Survival via Disrupting Wnt/β-Catenin Signaling in Spinal Cord Injury

Wnt signaling are recognized key factors in neuronal development, cell proliferation and axonal guidance. However, RAGE effect on wnt signaling after spinal cord injury (SCI) are poorly understood. Our study aims to explore RAGE blockade effect on wnt signaling after SCI. We constructed Allen SCI model and micro-injected with RAGE neutralizing antibody or IgG after injury. We determined β-catenin, wnt3a and its receptor frizzled-5 via Western blot. We determined β-catenin/NeuN expression at 2 weeks after SCI via immunofluorescence (IF). We found that β-catenin, wnt3a and wnt receptor frizzled5 expression were activated after SCI at 3 days after injury. However, RAGE blockade inhibit β-catenin, wnt3a and frizzled5 expression. We found that β-catenin accumulation in NeuN cells were activated after SCI via IF, however, RAGE blockade reduced β-catenin and NeuN positive cells. RAGE blockade attenuated number of survived neurons and decreased area of spared white matter around the epicenter. RAGE signaling may involved in disrupting wnt signaling to aids neuronal recovery after SCI.     

Progesterone neuroprotection in spinal cord trauma involves up-regulation of brain-derived neurotrophic factor in motoneurons

Progesterone (PROG) provides neuroprotection to the injured central and peripheral nervous system. These effects may be due to regulation of myelin synthesis in glial cells and also to direct actions on neuronal function. Both types of cells express classical intracellular PROG receptors (PR), while neurons additionally express the PROG membrane-binding site called 25-Dx. In motoneurons from rats with spinal cord injury (SCI), PROG restores to normal the deficient levels of choline acetyl-transferase and of alpha3 subunit Na,K-ATPase mRNA, while levels of the growth associated protein GAP-43 mRNA are further stimulated. Recent studies suggest that neurotrophins are possible mediators of hormone action, and in agreement with this assumption, PROG treatment of rats with SCI increases the expression of brain-derived neurotrophic factor (BDNF) at both the mRNA and protein levels in ventral horn motoneurons. In situ hybridization (ISH) has shown that SCI reduces BDNF mRNA levels by 50% in spinal motoneurons, while PROG administration to injured rats (4mg/kg/day during 3 days, s.c.) elicits a three-fold increase in grain density. In addition to enhancement of mRNA levels, PROG increases BDNF immunoreactivity in perikaryon and cell processes of motoneurons of the lesioned spinal cord, and also prevents the lesion-induced chromatolytic degeneration of spinal cord motoneurons as determined by Nissl staining. Our findings strongly indicate that motoneurons of the spinal cord are targets of PROG, as confirmed by the expression of PR and the regulation of molecular parameters. PROG enhancement of endogenous neuronal BDNF could provide a trophic environment within the lesioned spinal cord and might be part of the PROG activated-pathways to provide neuroprotection. Thus, PROG treatment constitutes a new approach to sustain neuronal function after injury.     

Hydrogen-Rich Saline Protects Against Spinal Cord Injury in Rats

In the present study, we examined the mechanisms of hydrogen-rich saline, a reported therapeutic antioxidant, in the treatment of acute spinal cord contusion injury. Male Sprague-Dawley rats were used to produce a standardized model of contuses spinal cord injury (125 kdyn force). Hydrogen-rich saline was injected intraperitoneally (5 ml/kg) immediately, and at 24 and 48 h after injury. All rats were sacrificed at 72 h after spinal cord injury (SCI). Apoptotic cell death, oxidative stress, inflammation, level of Brain derived neurotrophic factor (BDNF) were evaluated. In addition, locomotor behavior was assessed using the Basso, Beattice and Bresnahan (BBB) scale. We observed that administration of hydrogen-rich saline decreased the number of apoptotic cells, suppressed oxidative stress, and improved locomotor functions. Hydrogen-rich saline increased the release of BDNF. In conclusion, hydrogen-rich saline reduced acute spinal cord contusion injury, possibly by reduction of oxidative stress and elevation of BDNF.     

The role of mTOR signaling pathway in spinal cord injury

The mammalian target of rapamycin (mTOR) signaling pathway plays an important role in multiple cellular functions, such as cell metabolism, proliferation and survival. Many previous studies have shown that mTOR regulates both neuroprotective and neuroregenerative functions in trauma and various diseases in the central nervous system (CNS). Recently, we reported that inhibition of mTOR using rapamycin reduces neural tissue damage and locomotor impairment after spinal cord injury (SCI) in mice. Our results demonstrated that the administration of rapamycin at four hours after injury significantly increases the activity of autophagy and reduces neuronal loss and cell death in the injured spinal cord. Furthermore, rapamycin-treated mice show significantly better locomotor function in the hindlimbs following SCI than vehicle-treated mice. These findings indicate that the inhibition of mTOR signaling using rapamycin during the acute phase of SCI produces neuroprotective effects and reduces secondary damage at lesion sites. However, the role of mTOR signaling in injured spinal cords has not yet been fully elucidated. Various functions are regulated by mTOR signaling in the CNS, and multiple pathophysiological processes occur following SCI. Here, we discuss several unresolved issues and review the evidence from related articles regarding the role and mechanisms of the mTOR signaling pathway in neuroprotection and neuroregeneration after SCI.     

Oncostatin M Reduces Lesion Size and Promotes Functional Recovery and Neurite Outgrowth After Spinal Cord Injury

The family of interleukin (IL)-6 like cytokines plays an important role in the neuroinflammatory response to injury by regulating both neural as well as immune responses. Here, we show that expression of the IL-6 family member oncostatin M (OSM) and its receptor is upregulated after spinal cord injury (SCI). To reveal the relevance of increased OSM signaling in the pathophysiology of SCI, OSM was applied locally after spinal cord hemisection in mice. OSM treatment significantly improved locomotor recovery after mild and severe SCI. Improved recovery in OSM-treated mice was associated with a reduced lesion size. OSM significantly diminished astrogliosis and immune cell infiltration. Thus, OSM limits secondary damage after CNS trauma. In vitro viability assays demonstrated that OSM protects primary neurons in culture from cell death, suggesting that the underlying mechanism involves direct neuroprotective effects of OSM. Furthermore, OSM dose-dependently promoted neurite outgrowth in cultured neurons, indicating that the cytokine plays an additional role in CNS repair. Indeed, our in vivo experiments demonstrate that OSM treatment increases plasticity of serotonergic fibers after SCI. Together, our data show that OSM is produced at the lesion site, where it protects the CNS from further damage and promotes recovery.