Intracerebral granulocyte‐macrophage colony‐stimulating factor induces functionally competent dendritic cells in the mouse brain

Granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) is a hematopoietic growth factor and a proinflammatory cytokine. While GM‐CSF is lacking in normal brain tissue, it is expressed under pathological conditions and correlates with the presence of dendritic cells (DC). However, the role of GM‐CSF for the onset of immune responses in the brain is still unclear. To analyze the role of GM‐CSF for the induction and functional activity of immune cells in the brain, we performed chronic intracerebroventricular administration of GM‐CSF to the brains of adult mice. After GM‐CSF administration, intracerebral leukocytes (ICL) were characterized by means of flow cytometry, immunohistochemistry, and an ex vivo functional assay. GM‐CSF treatment significantly increased the number of leukocytes expressing high levels of CD45, indicative of peripheral, blood‐derived cells. The infiltrating cells were preferentially DC of the myeloid lineage (CD45^high CD11c⁺ CD11b⁺) with an activated phenotype characterized by upregulated expression of MHCII and the costimulatory ligand CD80. Furthermore, DC from GM‐CSF treated mice were fully competent to activate naive allogeneic T cells in a mixed leukocyte reaction. In contrast, intracerebroventricular IFN‐γ administration stimulated MHCII expression on cells resembling resident microglia, but did not induce comparable presence of DC. Taken together, intracerebroventricular GM‐CSF treatment results in high numbers of DC in the brain. Moreover, these GM‐CSF‐induced DC display an activated phenotype and exhibit the capacity to act as fully competent DC even without a further inflammatory stimulus. © 2009 Wiley‐Liss, Inc.     

Neuregulin‐1 positively modulates glial response and improves neurological recovery following traumatic spinal cord injury

Spinal cord injury (SCI) results in glial activation and neuroinflammation, which play pivotal roles in the secondary injury mechanisms with both pro‐ and antiregeneration effects. Presently, little is known about the endogenous molecular mechanisms that regulate glial functions in the injured spinal cord. We previously reported that the expression of neuregulin‐1 (Nrg‐1) is acutely and chronically declined following traumatic SCI. Here, we investigated the potential ramifications of Nrg‐1 dysregulation on glial and immune cell reactivity following SCI. Using complementary in vitro approaches and a clinically‐relevant model of severe compressive SCI in rats, we demonstrate that immediate delivery of Nrg‐1 (500 ng/day) after injury enhances a neuroprotective phenotype in inflammatory cells associated with increased interleukin‐10 and arginase‐1 expression. We also found a decrease in proinflammatory factors including IL‐1β, TNF‐α, matrix metalloproteinases (MMP‐2 and 9) and nitric oxide after injury. In addition, Nrg‐1 modulates astrogliosis and scar formation by reducing inhibitory chondroitin sulfate proteoglycans after SCI. Mechanistically, Nrg‐1 effects on activated glia are mediated through ErbB2 tyrosine phosphorylation in an ErbB2/3 heterodimer complex. Furthermore, Nrg‐1 exerts its effects through downregulation of MyD88, a downstream adaptor of Toll‐like receptors, and increased phosphorylation of Erk1/2 and STAT3. Nrg‐1 treatment with the therapeutic dosage of 1.5 μg/day significantly improves tissue preservation and functional recovery following SCI. Our findings for the first time provide novel insights into the role and mechanisms of Nrg‐1 in acute SCI and suggest a positive immunomodulatory role for Nrg‐1 that can harness the beneficial properties of activated glia and inflammatory cells in recovery following SCI.     

Exogenous platelet-derived growth factor improves neurovascular unit recovery after spinal cord injury

The blood-spinal cord barrier plays a vital role in recovery after spinal cord injury. The neurovascular unit concept emphasizes the relationship between nerves and vessels in the brain, while the effect of the blood-spinal cord barrier on the neurovascular unit is rarely reported in spinal cord injury studies. Mouse models of spinal cord injury were established by heavy object impact and then immediately injected with plateletderived growth factor(80 μg/kg) at the injury site. Our results showed that after platelet-derived growth factor administration, spinal cord injury, neuronal apoptosis, and blood-spinal cord barrier permeability were reduced, excessive astrocyte proliferation and the autophagyrelated apoptosis signaling pathway were inhibited, collagen synthesis was increased, and mouse locomotor function was improved. In vitro, human umbilical vein endothelial cells were established by exposure to 200 μM H_2O_2. At 2 hours prior to injury, in vitro cell models were treated with 5 ng/mL platelet-derived growth factor. Our results showed that expression of blood-spinal cord barrier-related proteins, including Occludin, Claudin 5, and β-catenin, was significantly decreased and autophagy was significantly reduced. Additionally, the protective effects of platelet-derived growth factor could be reversed by intraperitoneal injection of 80 mg/kg chloroquine, an autophagy inhibitor, for 3 successive days prior to spinal cord injury. Our findings suggest that platelet-derived growth factor can promote endothelial cell repair by regulating autophagy, improve the function of the blood-spinal cord barrier, and promote the recovery of locomotor function post-spinal cord injury. Approval for animal experiments was obtained from the Animal Ethics Committee, Wenzhou Medical University, China(approval No. wydw2018-0043) in July 2018.     

Deferoxamine improves neurological function in a rat model of experimental spinal cord injury

A rat model of spinal cord injury was established using modified Allen's method and treated with the ferric iron-chelating agent,deferoxamine.Hematoxylin-eosin,Nissl and Perl's Prussian blue staining,at 7-14 days following spinal cord injury,showed that following deferoxamine treatment,glial cells proliferation increased significantly,nerve cell morphology was improved and hemosiderin was significantly reduced in the injury region.At 1-56 days following injury,Basso,Beattie,and Bresnahan Locomotor Rating Sc...     

NMDAR1、Caspase-3在脊髓缺血性损伤的表达特点及相关性研究

目的探讨脊髓缺血后N-甲基-D-天门冬氨酸受体1（N-methyl-D-aspartatereceptor,NMDARl）、Caspase-3的表达变化规律及意义。方法40只新西兰大白兔采用结扎腰动脉建立脊髓缺血模型,于缺血后6h、12h、24h、48h、72h取缺血脊髓标本,运用反转录聚合酶链反应（RT—PCR）及蛋白印记技术在基因和蛋白水平检测NMDAR1、Caspase-3在不同缺血时间的表达变化规律,同时运用免疫组织化学技术观察NMDAR1、Caspase-3在细胞中的表达定位情况;用SPSS统计分析。结果RT-PCR、蛋白印记显示缺血组与对照组比较NMDAR1、Caspase-3表达增加,并且有随缺血时间的延长表达逐渐增高的趋势,相关性分析显示NMDAR1、caspase-3在mRNA（r=0．947,P〈0．005）、蛋白（r=0．984,P〈0．005）水平呈正相关;免疫组化结果发现,NMDAR1、Caspase-3主要在细胞浆中表达。结论脊髓缺血时NMDAR1、caspase-3随缺血时间延长表达增加,NMDAR1、Caspase-3共同参与脊髓缺血性损伤过程,其表达与缺血时间有关。     

Effect of interleukin-2 on neurogliocyte and neuron apoptosis in rat models of acute spinal cord injury

BACKGROUND： lnterleukin-2 （IL-2） may influence the growth and survival of nerve cells following spinal cord injury and resuscitate the proliferation and maturation of oligodendrocytes. OBJECTIVE： To observe the effect of IL-2 on neuronal apoptosis of neurogliocytes at different times following acute spinal cord injury in rats. DESIGN, TIME AND SETTING： A randomized grouping trial based on cellular morphology was performed at the Institute of Traumatic Orthopedics of Shandong Province between October 2004 and January 2006. MATERIALS： A total of 72 adult, male, Sprague Dawley rats were included in this study and were divided into a control group and an IL-2 group. The Bcl-2 monoclonal antibody and TUNEL kit were purchased from Wunan Boster Biological Technology Corporation. METHODS： Spinal cord injury was induced in all the rats by dropping a weight from a height of 25 cm onto the exposed spinal cord at vertebral levels T7-11, thus producing a mild lesion. Immediately following the modeling, the rats were injected with daily IL-2 （10 uL） intramuscularly （the IL-2 group）. Other rats received an injection of physiological saline 0.5 mL/d （the control group）. MAIN OUTCOME MEASURES： Bcl-2 immunohistochemistry was applied to detect the Bcl-protein and positive cell expression. The TUNEL method was used to count the number of apoptotic cells. RESULTS： The expression level of Bcl-2 proteins increased significantly in spinal cord tissues during the first day after acute spinal cord injury, reaching a peak on days 3 and days 8 in the control and IL-2 groups, respectively. They were more prevalent in neurogliocytes than in neurocytes, and then began to decrease on day 14. From then until day 21, less expression was detected （P 〈 0.05）. In the control group, many apoptotic cells existed after 24 hours, and most of them were gliocytes; apoptotic cells reached a peak after 3-8 days. They then decreased gradually until day 21, when a small number of cells were still available. In the IL-2 grou     

Syntenin‐a promotes spinal cord regeneration following injury in adult zebrafish

In contrast to mammals, adult zebrafish recover locomotor function after spinal cord injury, in part due to the capacity of the central nervous system to repair severed connections. To identify molecular cues that underlie regeneration, we conducted mRNA expression profiling and found that syntenin‐a expression is upregulated in the adult zebrafish spinal cord caudal to the lesion site after injury. Syntenin is a scaffolding protein involved in mammalian cell adhesion and movement, axonal outgrowth, establishment of cell polarity, and protein trafficking. It could thus be expected to be involved in supporting regeneration in fish. Syntenin‐a mRNA and protein are expressed in neurons, glia and newly generated neural cells, and upregulated caudal to the lesion site on days 6 and 11 following spinal cord injury. Treatment of spinal cord‐injured fish with two different antisense morpholinos to knock down syntenin‐a expression resulted in significant inhibition of locomotor recovery at 5 and 6 weeks after injury, when compared to control morpholino‐treated fish. Knock‐down of syntenin‐a reduced regrowth of descending axons from brainstem neurons into the spinal cord caudal to the lesion site. These observations indicate that syntenin‐a is involved in regeneration after traumatic insult to the central nervous system of adult zebrafish, potentially leading to novel insights into the cellular and molecular mechanisms that require activation in the regeneration‐deficient mammalian central nervous system.     

Endogenous expression of interleukin‐4 regulates macrophage activation and confines cavity formation after traumatic spinal cord injury

Traumatic spinal cord injury (SCI) triggers inflammatory reactions in which various types of cells and cytokines are involved. Several proinflammatory cytokines are up‐regulated after SCI and play crucial roles in determining the extent of secondary tissue damage. However, relatively little is known about antiinflammatory cytokines and their roles in spinal cord trauma. Recent studies have shown that an antiinflammatory cytokine, interleukin‐4 (IL‐4), is expressed and exerts various modulatory effects in CNS inflammation. We found in the present study that IL‐4 was highly expressed at 24 hr after contusive SCI in rats and declined thereafter, with concurrent up‐regulation of IL‐4 receptor subunit IL‐4α. The majority of IL‐4‐producing cells were myeloperoxidase‐positive neutrophils. Injection of neutralizing antibody against IL‐4 into the contused spinal cord did not significantly affect the expression levels of proinflammatory cytokines such as IL‐1β, IL‐6, and tumor necrosis factor‐α or other antiinflammatory cytokines such as IL‐10 and transforming growth factor‐β. Instead, attenuation of IL‐4 activity led to a marked increase in the extent of ED1‐positive macrophage activation along the rostrocaudal extent at 7 days after injury. The enhanced macrophage activation was preceded by an increase in the level of monocyte chemoattractant protein‐1 (MCP‐1/CCL2). Finally, IL‐4 neutralization resulted in more extensive cavitation at 4 weeks after injury. These results suggest that endogenous expression of antiinflammatory cytokine IL‐4 regulates the extent of acute macrophage activation and confines the ensuing secondary cavity formation after spinal cord trauma. © 2010 Wiley‐Liss, Inc     

Relationships between microRNA-20a and microRNA-125b expression and apoptosis and inflammation in experimental spinal cord injury

ABSTRACT

Objectives: The aim of the study was to determine the relationships between microRNA-20a and microRNA-125b expression and apoptosis and inflammation in a rat model of spinal cord injury (SCI) using microscopy, immunohistochemistry, and molecular biology.

Methods: Sixty-one rats were divided into three groups: a control group that was not subjected to any operation; a sham-operated group; and an experimental group that was subjected to spinal cord compression. The experimental group was further subdivided into two subgroups: the experimental control group, which did not receive any drug treatment; and the methylprednisolone treatment group, which received 30 mg/kg methylprednisolone on day 0 followed by 10 mg/kg/day methylprednisolone from days 1–14.

Results: Tumor necrosis factor-alpha (TNF-α) and interleukin (IL)-6 levels increased in the experimental control group on days 1 and 3, and decreased in the experimental control group and methylprednisolone treatment group on days 7 and 14. Caspase-3 levels increased in the experimental control group on day 1, and decreased in the experimental control group and methylprednisolone treatment group on days 3, 7, and 14. MicroRNA-20a expression was upregulated in the experimental control group on days 1 and 3, and microRNA-125b expression was downregulated on days 3 and 7.

Conclusions: After SCI, upregulated microRNA-20a expression and increased proinflammatory cytokines may lead to an increase in inflammation. MicroRNA-125b may be associated with caspase-3, and microRNA-125b downregulation may inhibit apoptosis. Although the results of this study suggest potential relationships between microRNA-20a and microRNA-125b expression and apoptosis and inflammation in SCI, further studies are needed to confirm microRNA-20a and microRNA-125b as biomarkers in SCI and to develop new strategies for the treatment of SCI.     

Contribution of bone marrow‐derived endothelial progenitor cells to neovascularization and astrogliosis following spinal cord injury

Spinal cord injury causes initial mechanical damage, followed by ischemia‐induced, secondary degeneration, worsening the tissue damage. Although endothelial progenitor cells (EPCs) have been reported to play an important role for pathophysiological neovascularization in various ischemic tissues, the EPC kinetics following spinal cord injury have never been elucidated. In this study, we therefore assessed the in vivo kinetics of bone marrow‐derived EPCs by EPC colony‐forming assay and bone marrow transplantation from Tie2/lacZ transgenic mice into wild‐type mice with spinal cord injury. The number of circulating mononuclear cells and EPC colonies formed by the mononuclear cells peaked at day 3 postspinal cord injury. Bone marrow transplantation study revealed that bone marrow‐derived EPCs recruited into the injured spinal cord markedly increased at day 7, when neovascularization and astrogliosis drastically occurred in parallel with axon growth in the damaged tissue. To elucidate further the contribution of EPCs to recovery after spinal cord injury, exogenous EPCs were systemically infused immediately after the injury. The administered EPCs were incorporated into the injured spinal cord and accelerated neovascularization and astrogliosis. These findings suggest that bone marrow‐derived EPCs may contribute to the tissue repair by augmenting neovascularization and astrogliosis following spinal cord injury. © 2012 Wiley Periodicals, Inc.     

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.     

表达hVEGF165重组腺相关病毒对脊髓损伤的作用

血管内皮细胞因子曾经被认为是具有促血管生成作用的血管生长因子,如今,更多的研究将其应用于神经细胞缺血损伤的保护中。然而,一些研究却认为VEGF的应用使得脊髓损伤后脊髓的二次打击更加严重。为了探讨VEGF是否能够有效保护损伤的脊髓,我们在大鼠脊髓损伤模型中应用了表达hVEGF165的重组腺相关病毒。我们将大鼠随机分为假手术组,单纯脊髓损伤对照组,AAV-GFP组及AAV-VEGF 组。在相应时间点评估完神经功能后,我们将脊髓组织迅速取出。我们通过透射电子显微镜观察及TUNEl凋亡组织学染色观察在形态学角度评估凋亡的发生。应用免疫组化及Western blot评估凋亡蛋白Bax 和Bcl-2的表达。通过水通道蛋白-4（AQP-4）的免疫组化染色观察VEGF表达与脊髓损伤的相关性。实验结果显示,AAV-VEGF 组神经功能较对照组及AAV-GFP组有显著差异。(P < 0.05). VEGF能够明显抑制神经细胞的凋亡,减少运动神经元的损伤和丢失,减少细胞凋亡率。VEGF治疗组BAX蛋白表达减弱,Bcl-2蛋白表达加强,AQP-4表达减弱。所有结果表明VEGF具有对脊髓损伤神经的保护效应。     

Differences in neurotrophic factor gene expression profiles between neonate and adult rat spinal cord after injury

The capacity of the central nervous system for axonal growth decreases as the age of the animal at the time of injury increases. Changes in the expression of neurotrophic factors within embryonic and early postnatal spinal cord suggest that a lack of trophic support contributes to this restrictive growth environment. We examined neurotrophic factor gene profiles by ribonuclease protection assay in normal neonate and normal adult spinal cord and in neonate and adult spinal cord after injury. Our results show that in the normal developing spinal cord between postnatal days 3 (P3) and P10, compared to the normal adult spinal cord, there are higher levels of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin 3 (NT-3), and glial-derived neurotrophic factor (GDNF) mRNA expression and a lower level of ciliary neurotrophic factor (CNTF) mRNA expression. Between P10 and P17, there is a significant decrease in the expression of NGF, BDNF, NT-3, and GDNF mRNA and a contrasting steady and significant increase in the level of CNTF mRNA expression. These findings show that there is a critical shift in neurotrophic factor expression in normal developing spinal cord between P10 and P17. In neonate spinal cord after injury, there is a significantly higher level of BDNF mRNA expression and a significantly lower level of CNTF mRNA expression compared to those observed in the adult spinal cord after injury. These findings suggest that high levels of BDNF mRNA expression and low levels of CNTF mRNA expression play important roles in axonal regrowth in early postnatal spinal cord after injury.     

Blood-spinal cord barrier after spinal cord injury: relation to revascularization and wound healing

Spinal cord injury produces prominent disruption of the blood-spinal cord barrier. We have defined the blood-spinal cord barrier breakdown to the protein luciferase (61 kDa) in the acutely injured murine spinal cord and during revascularization. We show that newly formed and regenerating blood vessels that have abnormal permeability exhibit differential expression of the glucose-1 transporter (Glut-1), and that its expression is dependent on astrocytes. There was overt extravasation of luciferase within the first hour after injury, a period that coincided with marked tissue disruption within the epicenter of the lesion. Although there was a significant reduction in the number of blood vessels relative to controls by 24 hr after injury, abnormal barrier permeability remained significantly elevated. A second peak of abnormal barrier permeability at 3-7 days postinjury coincided with prominent revascularization of the epicenter. The barrier to luciferase was restored by 21 days postinjury and vascularity was similar to that of controls. During wound-healing process, the cord was reorganized into distinct domains. Between 14 and 21 days postinjury, each domain consisted primarily of nonneuronal cells, including macrophages. Astrocytes were limited characteristically to the perimeter of each domain. Only blood vessels affiliated closely with astrocytes in the perimeter expressed Glut-1, whereas blood vessels within each domain of the repairing cord did not express it. Together, these data demonstrate that both injured and regenerating vessels exhibit abnormal permeability and suggest that Glut-1 expression during revascularization is dependent on the presence of astrocytes.     

Changes in truncated trkB and p75 receptor expression in the rat spinal cord following spinal cord hemisection and spinal cord hemisection plus neurotrophin treatment

Although numerous studies have examined the effects of neurotrophin treatment following spinal cord injury, few have examined the changes that occur in the neurotrophin receptors following either such damage or neurotrophin treatment. To determine what changes occur in neurotrophin receptor expression following spinal cord damage, adult rats received a midthoracic spinal cord hemisection alone or in combination with intrathecal application of brain-derived neurotrophic factor (BDNF) or neurotrophin-3 (NT-3). Using immunohistochemical and in situ hybridization techniques, p75, trkA, trkB, and trkC receptor expression was examined throughout the spinal cord. Results showed that trkA, full-length trkB, and trkC receptors were not present in the lesion site but had a normal expression pattern in uninjured parts of the spinal cord. In contrast, p75 receptor expression occurred on Schwann cells throughout the lesion site. BDNF and NT-3 (but not saline) applied to the lesion site increased this expression. In addition, the truncated trkB receptor was expressed in the border between the lesion and intact spinal cord. Truncated trkB receptor expression was also increased throughout the white matter ipsilateral to the lesion and BDNF (but not NT-3 or saline) prevented this increase. The study is the first to show changes in truncated trkB receptor expression that extend beyond the site of a spinal cord lesion and is one of the first to show that BDNF and NT-3 affect Schwann cells and/or p75 expression following spinal cord damage. These results indicate that changes in neurotrophin receptor expression following spinal cord injury could influence the availability of neurotrophins at the lesion site. In addition, neurotrophins may affect their own availability to damaged neurons by altering the expression of the p75 and truncated trkB receptor.