Identification of distinct monocyte phenotypes and correlation with circulating cytokine profiles in acute response to spinal cord injury: a pilot study

Systemic Inflammatory Changes in Spinal Cord Injured Patients after Adding Aquatic Therapy to Standard Physiotherapy Treatment

Spinal cord injury (SCI) is a severe medical condition resulting in substantial physiological and functional consequences for the individual. People with SCI are characterised by a chronic, low-grade systemic inflammatory state, which contributes to further undesirable secondary injuries. This study aimed to evaluate the effect of adding aquatic therapy to the standard physiotherapy treatment, implemented in two different schedules, on systemic inflammation in SCI patients. Additionally, the relationship between cytokine blood levels and changes in functionality (measured with the 6MWT, 10MWT, WISCI, BBS, and TUG tests) throughout the study was assessed. A quantitative multiplexed antibody assay was performed to measure the expression level of 20 pro- and anti-inflammatory cytokines in blood samples from SCI patients at three time points: baseline, week 6, and immediately post-intervention (week 12). This study identified a complex signature of five cytokines (IL-12p70, IL-8, MCP-1, IL-1α, and IP10) associated with the time course of the two physiotherapy programs. Two other cytokines (IL-4 and TNF-α) were also associated with the functional recovery of patients. These could be important indicators for SCI prognosis and provide a basis for developing novel targeted therapies.

Water channels in the brain and spinal cord-overview of the role of aquaporins in traumatic brain injury and traumatic spinal cord injury

Knowledge about the mechanisms underlying the fluid flow in the brain and spinal cord is essential for discovering the mechanisms implicated in the pathophysiology of central nervous system diseases. During recent years, research has highlighted the complexity of the fluid flow movement in the brain through a glymphatic system and a lymphatic network. Less is known about these pathways in the spinal cord. An important aspect of fluid flow movement through the glymphatic pathway is the role of water channels, especially aquaporin 1 and 4. This review provides an overview of the role of these aquaporins in brain and spinal cord, and give a short introduction to the fluid flow in brain and spinal cord during in the healthy brain and spinal cord as well as during traumatic brain and spinal cord injury. Finally, this review gives an overview of the current knowledge about the role of aquaporins in traumatic brain and spinal cord injury, highlighting some of the complexities and knowledge gaps in the field.

A comprehensive look at the psychoneuroimmunoendocrinology of spinal cord injury and its progression: mechanisms and clinical opportunities

Spinal cord injury (SCI) is a devastating and disabling medical condition generally caused by a traumatic event (primary injury). This initial trauma is accompanied by a set of biological mechanisms directed to ameliorate neural damage but also exacerbate initial damage (secondary injury). The alterations that occur in the spinal cord have not only local but also systemic consequences and virtually all organs and tissues of the body incur important changes after SCI, explaining the progression and detrimental consequences related to this condition. Psychoneuroimmunoendocrinology (PNIE) is a growing area of research aiming to integrate and explore the interactions among the different systems that compose the human organism, considering the mind and the body as a whole. The initial traumatic event and the consequent neurological disruption trigger immune, endocrine, and multisystem dysfunction, which in turn affect the patient's psyche and well-being. In the present review, we will explore the most important local and systemic consequences of SCI from a PNIE perspective, defining the changes occurring in each system and how all these mechanisms are interconnected. Finally, potential clinical approaches derived from this knowledge will also be collectively presented with the aim to develop integrative therapies to maximize the clinical management of these patients.

Abnormal Characterization and Distribution of Circulating Regulatory T Cells in Patients with Chronic Spinal Cord Injury According to the Period of Evolution

Spinal cord injury (SCI) is a progressive and complex neurological disorder accompanied by multiple systemic challenges. Peripheral immune dysfunction is a major event occurring after SCI, especially in its chronic phase. Previous works have demonstrated significant changes in different circulating immune compartments, including in T cells. However, the precise characterization of these cells remains to be fully unraveled, particularly when considering important variants such as the time since the initial injury. In the present work, we aimed to study the level of circulating regulatory T cells (Tregs) in SCI patients depending on the duration of evolution. For this purpose, we studied and characterized peripheral Tregs from 105 patients with chronic SCI using flow cytometry, with patients classified into three major groups depending on the time since initial injury: short period chronic (SCI-SP, <5 years since initial injury); early chronic (SCI-ECP, from 5-15 years post-injury) and late chronic SCI (SCI-LCP, more than 15 years post-injury. Our results show that both the SCI-ECP and SCI-LCP groups appeared to present increased proportions of CD4+ CD25+/low Foxp3+ Tregs in comparison to healthy subjects, whereas a decreased number of these cells expressing CCR5 was observed in SCI-SP, SCI-ECP, and SCI-LCP patients. Furthermore, an increased number of CD4+ CD25+/high/low Foxp3 with negative expression of CD45RA and CCR7 was observed in SCI-LCP patients when compared to the SCI-ECP group. Taken together, these results deepen our understanding of the immune dysfunction reported in chronic SCI patients and how the time since initial injury may drive this dysregulation.

The inflammatory response and blood-spinal cord barrier integrity in traumatic spinal cord injury: a prospective pilot study

PURPOSE

Triggering of inflammatory responses and disruption of blood-spinal cord barrier (BSCB) integrity are considered pivotal events in the pathophysiology of traumatic spinal cord injury (TSCI). Yet, these events are poorly understood and described in humans. This study aims to describe inflammatory responses and BSCB integrity in human TSCI.

METHODS

Fifteen TSCI patients and fifteen non-TSCI patients were prospectively recruited from Aarhus University Hospital, Denmark. Peripheral blood (PB) and cerebrospinal fluid (CSF) were collected at median day 0 [IQR: 1], median day 9 [IQR: 2], and median day 148 [IQR: 49] after injury. PB and CSF were analyzed for immune cells by flow cytometry, cytokines by multiplex immunoassay, and BSCB integrity by IgG Index.

RESULTS

Eleven TSCI patients completed follow-up. Results showed alterations in innate and adaptive immune cell counts over time. TSCI patients had significantly increased cytokine concentrations in CSF at the first and second follow-up, while only concentrations of interleukin (IL)-4, IL-8, and tumor necrosis factor-α remained significantly increased at the third follow-up. In PB, TSCI patients had significantly increased IL-6, IL-8, and IL-10 concentrations and significantly decreased interferon-γ concentrations at the first follow-up. Results further showed increased IgG Index indicative of BSCB disruption in seven TSCI patients at the first follow-up, five TSCI patients at the second follow-up, and two patients at the third follow-up.

CONCLUSIONS

Our results suggest that TSCI mainly triggers innate inflammatory responses that resolves over time, although with some degree of non-resolving inflammation, particularly in CSF. Our results cannot confirm BSCB disruption in all TSCI patients.

Role of CXCL10 in Spinal Cord Injury

Spinal cord injury (SCI) results in acute inflammatory responses and secondary damages, including neuronal and glial cell death, axonal damage and demyelination, and blood-brain barrier (BBB) damage, eventually leading to neuronal dysfunction and other complications. C-X-C motif Chemokine Ligand 10 (CXCL10) is expressed after the injury, playing multiple roles in the development and progression of SCI. Moreover, the CXCL10 antagonist can restrict inflammatory immune responses and promote neuronal regeneration and functional recovery. In this review, we summarize the structure and biological functions of CXCL10, and the roles of the CXCL10 / CXCR3 axis in acute inflammatory responses, secondary damages, and complications during SCI, thus providing a potential theoretical basis by highlighting CXCL10 as a new potential drug target for the treatment of SCI.

Cerebrospinal fluid and peripheral blood proteomics in Traumatic Spinal Cord Injury: A prospective pilot study

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Proteomics enable profiling of inflammatory responses after spinal cord injury.

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Proteins are differentially expressed over time.

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Proteins are differentially expressed in cerebrospinal fluid and peripheral blood.

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A poor relationship exists between protein expression and neurological outcome.

Regulation of Inflammatory Cytokines for Spinal Cord Injury Repair Through Local Delivery of Therapeutic Agents

The balance of inflammation is critical to the repair of spinal cord injury (SCI), which is one of the most devastating traumas in human beings. Inflammatory cytokines, the direct mediators of local inflammation, have differential influences on the repair of the injured spinal cord. Some inflammatory cytokines are demonstrated beneficial to spinal cord repair in SCI models, while some detrimental. Various animal researches have revealed that local delivery of therapeutic agents efficiently regulates inflammatory cytokines and promotes repair from SCI. Quite a few clinical studies have also shown the promotion of repair from SCI through regulation of inflammatory cytokines. However, local delivery of a single agent affects only a part of the inflammatory cytokines that need to be regulated. Meanwhile, different individuals have differential profiles of inflammatory cytokines. Therefore, future studies may aim to develop personalized strategies of locally delivered therapeutic agent cocktails for effective and precise regulation of inflammation, and substantial functional recovery from SCI.

Promises and limitations of immune cell-based therapies in neurological disorders

The healthy immune system has natural checkpoints that temper pernicious inflammation. Cells mediating these checkpoints include regulatory T cells, regulatory B cells, regulatory dendritic cells, microglia, macrophages and monocytes. Here, we highlight discoveries on the beneficial functions of regulatory immune cells and their mechanisms of action and evaluate their potential use as novel cell-based therapies for brain disorders. Regulatory immune cell therapies have the potential not only to mitigate the exacerbation of brain injury by inflammation but also to promote an active post-injury brain repair programme. By harnessing the reparative properties of these cells, we can reduce over-reliance on medications that mask clinical symptoms but fail to impede or reverse the progression of brain disorders. Although these discoveries encourage further testing and genetic engineering of regulatory immune cells for the clinical management of neurological disorders, a number of challenges must be surmounted to improve their safety and efficacy in humans.

Spinal Cord Injury Scarring and Inflammation: Therapies Targeting Glial and Inflammatory Responses

Deficits in neuronal function are a hallmark of spinal cord injury (SCI) and therapeutic efforts are often focused on central nervous system (CNS) axon regeneration. However, secondary injury responses by astrocytes, microglia, pericytes, endothelial cells, Schwann cells, fibroblasts, meningeal cells, and other glia not only potentiate SCI damage but also facilitate endogenous repair. Due to their profound impact on the progression of SCI, glial cells and modification of the glial scar are focuses of SCI therapeutic research. Within and around the glial scar, cells deposit extracellular matrix (ECM) proteins that affect axon growth such as chondroitin sulfate proteoglycans (CSPGs), laminin, collagen, and fibronectin. This dense deposition of material, i.e., the fibrotic scar, is another barrier to endogenous repair and is a target of SCI therapies. Infiltrating neutrophils and monocytes are recruited to the injury site through glial chemokine and cytokine release and subsequent upregulation of chemotactic cellular adhesion molecules and selectins on endothelial cells. These peripheral immune cells, along with endogenous microglia, drive a robust inflammatory response to injury with heterogeneous reparative and pathological properties and are targeted for therapeutic modification. Here, we review the role of glial and inflammatory cells after SCI and the therapeutic strategies that aim to replace, dampen, or alter their activity to modulate SCI scarring and inflammation and improve injury outcomes.

Suppressed networks of inflammatory mediators characterize chronic venous insufficiency

OBJECTIVE

Chronic venous insufficiency (CVI) affects 25 million adults in the United States. Little emphasis has been placed on inflammatory changes associated with CVI. We hypothesize that in patients with early to mid-stage benign varicose vein disease, differences in circulating inflammatory mediators will be manifested in blood draining the involved area vs circulating blood in control subjects.

METHODS

Patients undergoing either endovenous ablation or sclerotherapy for Clinical, Etiology, Anatomy, and Pathophysiology clinical class 3 to 5 disease underwent phlebotomy from regional veins at the time of the procedure. The patient's age, gender, clinical class, duration of symptoms, presence of superficial truncal reflux by duplex ultrasound, and treatment modality were recorded. Plasma from patients and banked blood samples from healthy volunteers (HVs) were subjected to Luminex (EMD Millipore, Billerica, Mass) to evaluate the expression of an established panel of 20 inflammatory mediators. Mediator concentrations were compared between patients and HVs using Mann-Whitney U tests. Importantly, computational analysis allowed us to compare not only the panel of inflammatory mediators but also the inflammatory networks connecting these mediators to one another. Principal components were analyzed to assess network robustness in each group.

RESULTS

CVI venous blood revealed significantly lower levels of monokine induced by γ interferon, soluble interleukin (IL) 2 receptor α chain, IL-4, IL-6, IL-7, tumor necrosis factor α, eotaxin, and granulocyte-macrophage colony-stimulating factor than blood from controls. Inflammatory networks were significantly less complex and less robust in the CVI patients compared with HVs. Based on principal component analysis, responses among HVs were more varied than those of CVI patients.

CONCLUSIONS

We demonstrate that patients with CVI have significant differences not only in blood-borne inflammatory mediators but also in the interconnectedness of these mediators with one another and in their principal inflammatory characteristics. Results suggest hypoinflammation in chronic nonhealing changes in CVI. These novel findings, if validated in larger cohorts, may help predict the risk of disease progression or response to therapy in the future and may guide mechanistic studies on tissue responses to CVI.

Minocycline Has Anti-inflammatory Effects and Reduces Cytotoxicity in an Ex Vivo Spinal Cord Slice Culture Model of West Nile Virus Infection

West Nile virus (WNV) is a neurotropic flavivirus that can cause significant neurological disease. Mouse models of WNV infection demonstrate that a proinflammatory environment is induced within the central nervous system (CNS) after WNV infection, leading to entry of activated peripheral immune cells. We utilized ex vivo spinal cord slice cultures (SCSC) to demonstrate that anti-inflammatory mechanisms may also play a role in WNV-induced pathology and/or recovery. Microglia are a type of macrophage that function as resident CNS immune cells. Similar to mouse models, infection of SCSC with WNV induces the upregulation of proinflammatory genes and proteins that are associated with microglial activation, including the microglial activation marker Iba1 and CC motif chemokines CCL2, CCL3, and CCL5. This suggests that microglia assume a proinflammatory phenotype in response to WNV infection similar to the proinflammatory (M1) activation that can be displayed by other macrophages. We now show that the WNV-induced expression of these and other proinflammatory genes was significantly decreased in the presence of minocycline, which has antineuroinflammatory properties, including the ability to inhibit proinflammatory microglial responses. Minocycline also caused a significant increase in the expression of anti-inflammatory genes associated with alternative anti-inflammatory (M2) macrophage activation, including interleukin 4 (IL-4), IL-13, and FIZZ1. Minocycline-dependent alterations to M1/M2 gene expression were associated with a significant increase in survival of neurons, microglia, and astrocytes in WNV-infected slices and markedly decreased levels of inducible nitric oxide synthase (iNOS). These results demonstrate that an anti-inflammatory environment induced by minocycline reduces viral cytotoxicity during WNV infection in ex vivo CNS tissue.IMPORTANCE West Nile virus (WNV) causes substantial morbidity and mortality, with no specific therapeutic treatments available. Antiviral inflammatory responses are a crucial component of WNV pathology, and understanding how they are regulated is important for tailoring effective treatments. Proinflammatory responses during WNV infection have been extensively studied, but anti-inflammatory responses (and their potential protective and reparative capabilities) following WNV infection have not been investigated. Minocycline induced the expression of genes associated with the anti-inflammatory (M2) activation of CNS macrophages (microglia) in WNV-infected SCSC while inhibiting the expression of genes associated with proinflammatory (M1) macrophage activation and was protective for multiple CNS cell types, indicating its potential use as a therapeutic reagent. This ex vivo culture system can uniquely address the ability of CNS parenchymal cells (neurons, astrocytes, and microglia) to respond to minocycline and to modulate the inflammatory environment and cytotoxicity in response to WNV infection without peripheral immune cell involvement.

Neuroimmunology of Traumatic Brain Injury: Time for a Paradigm Shift

Traumatic brain injury (TBI) is a leading cause of morbidity and disability, with a considerable socioeconomic burden. Heterogeneity of pathoanatomical subtypes and diversity in the pathogenesis and extent of injury contribute to differences in the course and outcome of TBI. Following the primary injury, extensive and lasting damage is sustained through a complex cascade of events referred to as "secondary injury." Neuroinflammation is proposed as an important manipulable aspect of secondary injury in animal and human studies. Because neuroinflammation can be detrimental or beneficial, before developing immunomodulatory therapies, it is necessary to better understand the timing and complexity of the immune responses that follow TBI. With a rapidly increasing body of literature, there is a need for a clear summary of TBI neuroimmunology. This review presents our current understanding of the immune response to TBI in a chronological and compartment-based manner, highlighting early changes in gene expression and initial signaling pathways that lead to activation of innate and adaptive immunity. Based on recent advances in our understanding of innate immune cell activation, we propose a new paradigm to study innate immune cells following TBI that moves away from the existing M1/M2 classification of activation states toward a stimulus- and disease-specific understanding of polarization state based on transcriptomic and proteomic profiling.

sCD95L in serum after spinal cord injury

STUDY DESIGN

A prospective observational study reporting correlation between sCD95L (serum cluster of differentiation 95 ligand) serum levels and remission after traumatic spinal cord injury (SCI).

OBJECTIVES

To describe the correlation between sCD95L serum levels and remission after traumatic SCI in a human protocol compared with animal studies.

SETTING

Rhineland-Palatinate (Rheinland-Pfalz), Germany.

METHODS

We included 45 patients with traumatic SCI. According to their neurological outcome, patients were divided into two groups, patients with (G1, n=26) and without (G2, n=19) remission. Blood was collected on post-admission and according to a fixed scheme, that is, after 4, 9, 12 h, 1, 3 days and 1, 2, 4, 8, 12 weeks.

RESULTS

By comparing G1 with G2, we found a correlation between neurological remission and sCD95L serum concentrations. Consistently elevated levels of sCD95L in G1 between 9 h and 1 month after injury show significantly differing values 7 days after injury. This indicates a correlation between patients with clinically documented neurological remission and elevated sCD95L serum concentrations.

CONCLUSIONS

In opposite to animal studies, our patients with neurological remission show on average higher levels of sCD95L compared with patients without. Therefore, spinal cord-injured patients would probably not profit from neutralizing CD95L. Our results present that the transfer of findings from animal studies to humans must always be considered critically. We were able to show that peripheral serum cytokine expression is suitable to state processes after SCI in humans.

Inflammogenesis of Secondary Spinal Cord Injury

Spinal cord injury (SCI) and spinal infarction lead to neurological complications and eventually to paraplegia or quadriplegia. These extremely debilitating conditions are major contributors to morbidity. Our understanding of SCI has certainly increased during the last decade, but remains far from clear. SCI consists of two defined phases: the initial impact causes primary injury, which is followed by a prolonged secondary injury consisting of evolving sub-phases that may last for years. The underlying pathophysiological mechanisms driving this condition are complex. Derangement of the vasculature is a notable feature of the pathology of SCI. In particular, an important component of SCI is the ischemia-reperfusion injury (IRI) that leads to endothelial dysfunction and changes in vascular permeability. Indeed, together with endothelial cell damage and failure in homeostasis, ischemia reperfusion injury triggers full-blown inflammatory cascades arising from activation of residential innate immune cells (microglia and astrocytes) and infiltrating leukocytes (neutrophils and macrophages). These inflammatory cells release neurotoxins (proinflammatory cytokines and chemokines, free radicals, excitotoxic amino acids, nitric oxide (NO)), all of which partake in axonal and neuronal deficit. Therefore, our review considers the recent advances in SCI mechanisms, whereby it becomes clear that SCI is a heterogeneous condition. Hence, this leads towards evidence of a restorative approach based on monotherapy with multiple targets or combinatorial treatment. Moreover, from evaluation of the existing literature, it appears that there is an urgent requirement for multi-centered, randomized trials for a large patient population. These clinical studies would offer an opportunity in stratifying SCI patients at high risk and selecting appropriate, optimal therapeutic regimens for personalized medicine.

Cyclic AMP is a key regulator of M1 to M2a phenotypic conversion of microglia in the presence of Th2 cytokines

BACKGROUND

Microglia and macrophages play a central role in neuroinflammation. Pro-inflammatory cytokines trigger their conversion to a classically activated (M1) phenotype, sustaining inflammation and producing a cytotoxic environment. Conversely, anti-inflammatory cytokines polarize the cells towards an alternatively activated (M2), tissue reparative phenotype. Elucidation of the signal transduction pathways involved in M1 to M2 phenotypic conversion may provide insight into how the innate immune response can be harnessed during distinct phases of disease or injury to mediate neuroprotection and neurorepair.

METHODS

Microglial cells (cell line and primary) were subjected to combined cyclic adenosine monophosphate (cyclic AMP) and IL-4, or either alone, in the presence of pro-inflammatory mediators, lipopolysaccharide (LPS), or tumor necrosis factor-α (TNF-α). Their effects on the expression of characteristic markers for M1 and M2 microglia were assessed. Similarly, the M1 and M2 phenotypes of microglia and macrophages within the lesion site were then evaluated following a contusive spinal cord injury (SCI) to the thoracic (T8) spinal cord of rats and mice when the agents were administered systemically.

RESULTS

It was demonstrated that cyclic AMP functions synergistically with IL-4 to promote M1 to M2 conversion of microglia in culture. The combination of cyclic AMP and IL-4, but neither alone, induced an Arg-1(+)/iNOS(-)cell phenotype with concomitant expression of other M2-specific markers including TG2 and RELM-α. M2-converted microglia showed ameliorated production of pro-inflammatory cytokines (TNF-α and IP-10) and reactive oxygen species, with no alteration in phagocytic properties. M2a conversion required protein kinase A (PKA), but not the exchange protein directly activated by cyclic AMP (EPAC). Systemic delivery of cyclic AMP and IL-4 after experimental SCI also promoted a significant M1 to M2a phenotypic change in microglia and macrophage population dynamics in the lesion.

CONCLUSIONS

Using primary microglia, microglial cell lines, and experimental models of CNS injury, we demonstrate that cyclic AMP levels are a critical determinant in M1-M2 polarization. High levels of cyclic AMP promoted an Arg-1(+) M2a phenotype when microglia were activated with pro-inflammatory stimuli and Th2 cytokines. Th2 cytokines or cyclic AMP independently did not promote these changes. Phenotypic conversion of microglia provides a powerful new therapeutic approach for altering the balance of cytotoxic to reparative microglia in a diversity of neurological diseases and injury.

Azithromycin drives alternative macrophage activation and improves recovery and tissue sparing in contusion spinal cord injury

Background

Macrophages persist indefinitely at sites of spinal cord injury (SCI) and contribute to both pathological and reparative processes. While the alternative, anti-inflammatory (M2) phenotype is believed to promote cell protection, regeneration, and plasticity, pro-inflammatory (M1) macrophages persist after SCI and contribute to protracted cell and tissue loss. Thus, identifying non-invasive, clinically viable, pharmacological therapies for altering macrophage phenotype is a challenging, yet promising, approach for treating SCI. Azithromycin (AZM), a commonly used macrolide antibiotic, drives anti-inflammatory macrophage activation in rodent models of inflammation and in humans with cystic fibrosis.

Methods

We hypothesized that AZM treatment can alter the macrophage response to SCI and reduce progressive tissue pathology. To test this hypothesis, mice (C57BL/6J, 3-month-old) received daily doses of AZM (160 mg/kg) or vehicle treatment via oral gavage for 3 days prior and up to 7 days after a moderate-severe thoracic contusion SCI (75-kdyn force injury). Fluorescent-activated cell sorting was used in combination with real-time PCR (rtPCR) to evaluate the disposition and activation status of microglia, monocytes, and neutrophils, as well as macrophage phenotype in response to AZM treatment. An open-field locomotor rating scale (Basso Mouse Scale) and gridwalk task were used to determine the effects of AZM treatment on SCI recovery. Bone marrow-derived macrophages (BMDMs) were used to determine the effect of AZM treatment on macrophage phenotype in vitro.

Results

In accordance with our hypothesis, SCI mice exhibited significantly increased anti-inflammatory and decreased pro-inflammatory macrophage activation in response to AZM treatment. In addition, AZM treatment led to improved tissue sparing and recovery of gross and coordinated locomotor function. Furthermore, AZM treatment altered macrophage phenotype in vitro and lowered the neurotoxic potential of pro-inflammatory, M1 macrophages.

Conclusions

Taken together, these data suggest that pharmacologically intervening with AZM can alter SCI macrophage polarization toward a beneficial phenotype that, in turn, may potentially limit secondary injury processes. Given that pro-inflammatory macrophage activation is a hallmark of many neurological pathologies and that AZM is non-invasive and clinically viable, these data highlight a novel approach for treating SCI and other maladaptive neuroinflammatory conditions.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-015-0440-3) contains supplementary material, which is available to authorized users.

Age decreases macrophage IL-10 expression: Implications for functional recovery and tissue repair in spinal cord injury

Macrophages with different activation states are present after spinal cord injury (SCI). M1 macrophages purportedly promote secondary injury processes while M2 cells support axon growth. The average age at the time of SCI has increased in recent decades, however, little is known about how different physiological factors contribute to macrophage activation states after SCI. Here we investigate the effect of age on IL-10, a key indicator of M2 macrophage activation. Following mild-moderate SCI in 4 and 14 month old (MO) mice we detected significantly reduced IL-10 expression with age in the injured spinal cord. Specifically, CD86/IL-10 positive macrophages, also known as M2b or regulatory macrophages, were reduced in 14 vs. 4 MO SCI animals. This age-dependent shift in macrophage phenotype was associated with impaired functional recovery and enhanced tissue damage in 14-month-old SCI mice. In vitro, M2b macrophages release anti-inflammatory cytokines without causing neurotoxicity, suggesting that imbalances in the M2b response in 14-month-old mice may be contributing to secondary injury processes. Our data indicate that age is an important factor that regulates SCI inflammation and recovery even to mild-moderate injury. Further, alterations in macrophage activation states may contribute to recovery and we have identified the M2b phenotype as a potential target for therapeutic intervention.

A Computational, Tissue-Realistic Model of Pressure Ulcer Formation in Individuals with Spinal Cord Injury

People with spinal cord injury (SCI) are predisposed to pressure ulcers (PU). PU remain a significant burden in cost of care and quality of life despite improved mechanistic understanding and advanced interventions. An agent-based model (ABM) of ischemia/reperfusion-induced inflammation and PU (the PUABM) was created, calibrated to serial images of post-SCI PU, and used to investigate potential treatments in silico. Tissue-level features of the PUABM recapitulated visual patterns of ulcer formation in individuals with SCI. These morphological features, along with simulated cell counts and mediator concentrations, suggested that the influence of inflammatory dynamics caused simulations to be committed to "better" vs. "worse" outcomes by 4 days of simulated time and prior to ulcer formation. Sensitivity analysis of model parameters suggested that increasing oxygen availability would reduce PU incidence. Using the PUABM, in silico trials of anti-inflammatory treatments such as corticosteroids and a neutralizing antibody targeted at Damage-Associated Molecular Pattern molecules (DAMPs) suggested that, at best, early application at a sufficiently high dose could attenuate local inflammation and reduce pressure-associated tissue damage, but could not reduce PU incidence. The PUABM thus shows promise as an adjunct for mechanistic understanding, diagnosis, and design of therapies in the setting of PU.

n-3 PUFA supplementation benefits microglial responses to myelin pathology

Microglia represent rational but challenging targets for improving white matter integrity because of their dualistic protective and toxic roles. The present study examines the effect of Omega-3 polyunsaturated fatty acids (n-3 PUFAs) on microglial responses to myelin pathology in primary cultures and in the cuprizone mouse model of multiple sclerosis (MS), a devastating demyelination disease. Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), the two main forms of n-3 PUFAs in the brain, inhibited the release of nitric oxide and tumor necrosis factor-α from primary microglia upon IFN-γ and myelin stimulation. DHA and EPA also enhanced myelin phagocytosis in vitro. Therefore, n-3 PUFAs can inhibit inflammation while at the same time enhancing beneficial immune responses such as microglial phagocytosis. In vivo studies demonstrated that n-3 PUFA supplementation reduced cuprizone-induced demyelination and improved motor and cognitive function. The positive effects of n-3 PUFAs were accompanied by a shift in microglial polarization toward the beneficial M2 phenotype both in vitro and in vivo. These results suggest that n-3 PUFAs may be clinically useful as immunomodulatory agents for demyelinating diseases through a novel mechanism involving microglial phenotype switching.

Grafted bone marrow stromal cells: a contributor to glial repair after spinal cord injury

In the CNS, astrocytes, oligodendrocytes and microglias are involved in not only development but also pathology such as spinal cord injury (SCI). Glial cells play dual roles (negative vs. positive effects) in these processes. After SCI, detrimental effects usually dominate and significantly retard functional recovery, and curbing these effects is critical for promoting neurological improvement. Bone marrow stromal cells (BMSCs) represent a new therapeutic approach for SCI by enabling improved sensory and motor functions in animal models. Although transdifferentiation to spinal neurons was poor, because of their pleiotropic nature, the protective effects of BMSCs are broad and are primarily mediated through modulation of transdifferentiation into host spinal glial components. Transplantation of BMSCs can positively alter the spinal microenvironment and enhance recovery. The objective of this review is to discuss these and other related mechanisms. Since BMSCs transplantation has been applied in other clinical fields, we hope to provide useful clues for the clinical application of BMSCs to treat the SCI in the near future.