Altered Circulating Immune Cell Distribution in Traumatic Spinal Cord Injury Patients in Relation to Clinical Parameters

Regulation of dynamic spatiotemporal inflammation by nanomaterials in spinal cord injury

Spinal cord injury (SCI) is a common clinical condition of the central nervous system that can lead to sensory and motor impairment below the injury level or permanent loss of function in severe cases. Dynamic spatiotemporal neuroinflammation is vital to neurological recovery, which is collectively constituted by the dynamic changes in a series of inflammatory cells, including microglia, neutrophils, and astrocytes, among others. Immunomodulatory nanomaterials can readily improve the therapeutic effects and simultaneously overcome various drawbacks associated with treatment, such as the off-target side effects and loss of bioactivity of immune agents during circulation. In this review, we discuss the role of dynamic spatiotemporal inflammation in secondary injuries after SCI, elaborate on the mechanism of action and effect of existing nanomaterials in treating SCI, and summarize the mechanism(s) whereby they regulate inflammation. Finally, the challenges and prospects associated with using nanotechnology to modulate immunotherapy are discussed to provide new insights for future treatment. Deciphering the intricate spatiotemporal mechanisms of neuroinflammation in SCI requires further in-depth studies. Therefore, SCI continues to represent a formidable challenge.

The macrophage migration inhibitory factor/CD74 axis in traumatic spinal cord injury: lessons learned from animal and human studies

Traumatic spinal cord injury (SCI) is a severe condition leading to long-term impairment of motor, sensory, and autonomic functions. Following the initial injury, a series of additional events is initiated further damaging the spinal cord. During this secondary injury phase, both an inflammatory and immune modulatory response are triggered that have damaging and anti-inflammatory properties, respectively. The proinflammatory cytokine macrophage migration inhibitory factor (MIF) and its receptor CD74 have been extensively studied in traumatic SCI. MIF expression is increased in spinal cord tissue after experimental SCI, mainly in astrocytes and microglia, as well as in the plasma of SCI patients. Functionally, MIF and CD74 were shown to regulate astrocyte viability, proliferation and cholesterol metabolism, microglia migration, and neuronal viability. Moreover, inhibition of the MIF/CD74 axis improved the functional recovery of SCI animals. We provide a detailed overview of studies analyzing the role of MIF and CD74 in traumatic SCI. We describe results from animal studies, using rat and mouse models for SCI, and human studies. Furthermore, we propose a new path for investigation, focused on B cells, that might lead to a better understanding of how MIF and CD74 contribute to the secondary injury cascade following traumatic SCI.

Peripheral immune reactions following human traumatic spinal cord injury: the interplay of immune activation and suppression

Traumatic spinal cord injury (SCI) damages the nerve tissue of the spinal cord, resulting in loss of motor and/or sensory functions at and below the injury level. SCI provokes a long-lasting immune response that extends beyond the spinal cord and induces changes in the composition and function of the peripheral immune system. Seemingly contradictory findings have been observed, as both systemic immune activation, including inflammation and autoimmunity, and immune suppression have been reported. Differences in the levels and functions of various cell types and components of both the innate and adaptive immune system supporting these changes have been described at (sub)acute and chronic stages post-injury. Further research is needed for a more comprehensive understanding of the peripheral immune reactions following SCI, their possible correlations with clinical characteristics, and how these immune responses could be targeted to facilitate the therapeutic management of SCI. In this review, we provide an overview of the current literature discussing changes in the peripheral immune system and their occurrence over time following a traumatic SCI.

Human monocyte subtype expression of neuroinflammation and regeneration-related genes is linked to age and sex

Stroke is a leading cause of disability and the third cause of death. The immune system plays an essential role in post-stroke recovery. After an ischemic stroke, monocytes infiltrate the injured brain tissue and can exacerbate or mitigate the damage. Ischemic stroke is more prevalent in the aged population, and the aging brain exhibits an altered immune response. There are also sex disparities in ischemic stroke incidence, outcomes, and recovery, and these differences may be hormone-driven and determined by genetic and epigenetic factors. Here, we studied whether human peripheral blood monocyte subtype (classical, intermediate, and non-classical) expression of neuronal inflammation- and regeneration-related genes depends on age and sex. A FACS analysis of blood samples from 44 volunteers (male and female, aged 28 to 98) showed that in contrast to other immune cells, the proportion of natural killer cells increased in females. The proportion of B-cells decreased in both sexes with age, and subtypes of monocytes were not linked to age or sex. Gene expression analysis by qPCR identified several genes differentially correlating with age and sex within different monocyte subtypes. Interestingly, ANXA1 and CD36 showed a consistent increase with aging in all monocytes, specifically in intermediate (CD36) and intermediate and non-classical (ANXA1) subtypes. Other genes (IL-1β, S100A8, TNFα, CD64, CD33, TGFβ1, TLR8, CD91) were differentially changed in monocyte subtypes with increased aging. Most age-dependent gene changes were differentially expressed in female monocytes. Our data shed light on the nuanced interplay of age and sex in shaping the expression of inflammation- and regeneration-related genes within distinct monocyte subtypes. Understanding these dynamics could pave the way for targeted interventions and personalized approaches in post-stroke care, particularly for the aging population and individuals of different sexes.

The good or the bad: an overview of autoantibodies in traumatic spinal cord injury

Infections remain the most common cause of death after traumatic spinal cord injury, likely due to a developing immune deficiency syndrome. This, together with a somewhat contradictory development of autoimmunity in many patients, are two major components of the maladaptive systemic immune response. Although the local non-resolving inflammation in the lesioned spinal cord may lead to an antibody formation against autoantigens of the injured spinal cord tissue, there are also natural (pre-existing) autoantibodies independent of the injury. The way in which these autoantibodies with different origins affect the neuronal and functional outcome of spinal cord-injured patients is still controversial.

Patients with Chronic Spinal Cord Injury Display a Progressive Alteration over the Years of the Activation Stages of the T Lymphocyte Compartment

Spinal cord injury (SCI) is a serious medical condition associated with severe morbidities and disability. Chronic SCI patients present an enhanced susceptibility to infections and comorbidities with inflammatory pathogenesis. Chronic SCI appears to be associated with a systemic dysfunction of the immune system. We investigated the alteration of the pivotal CD4+ and CD8+ T lymphocytes in patients with chronic SCI at different years of evolution. A clinically homogenous population of 105 patients with chronic SCI (31 with time of evolution less than 5 years (SCI SP); 32 early chronic (SCI ECP) with time of evolution between 5 and 15 years; and 42 late chronic (SCI LCP) with time of evolution more than 15 years) and 38 healthy controls were enrolled. SCI ECP and SCI LCP patients showed significant CD4+ and CD8+ T lymphopenia, ascribed to a reduction in naïve and CM subsets. Furthermore, SCI ECP and SCI LCP patients showed a significant reduction in the expression of CD28 on CD8+ T lymphocytes. The expression of CCR6 by CD4+ T lymphocytes was decreased during the evolution of chronic SCI, but on CD8+ T lymphocytes, it was observed during the first 15 years of evolution. In conclusion, the chronic SCI course with severe damage to T lymphocytes mainly worsens over the years of disease evolution.

Aging with spinal cord injury: A narrative review of consequences and challenges

Given the increase in life expectancy, aging with a pre-existing spinal cord injury (SCI) is becoming more common. This condition is challenging as compromised health status and functional independence can worsen. We aimed to provide an updated overview of the consequences of aging with SCI, highlighting the main challenges facing this population in a narrative review of the current literature we retrieved from the PubMed database from 2000 to 2022 on any aspect related to aging in persons with SCI. Here we address adverse circumstances that increase disability and hinder an active lifestyle, such as progressive physical deterioration, secondary health conditions, limitations in personal activity, changes in family and social support structures, aging of caregivers, and depletion of economic resources. Favorable changes are also observed, including psychosocial adjustments that improve quality of life. Additionally, various interventions are discussed to promote well-being, health, and social participation. Due to the relevance of this issue, people with SCI and all those who take care of them must have up-to-date information to carry out the necessary measures to promote healthy aging in a more inclusive social environment.

Immunological Response to Exercise in Athletes with Disabilities: A Narrative Review of the Literature

For a person with a disability, participating in sports activities and/or competitions can be a challenge for the immune system. The relationship between exercise and immunity response in disabled athletes is, indeed, extremely complex for several reasons, including (1) the chronic low-grade inflammatory and immunodepression-"secondary immune deficiency"-state imposed by the disability/impairment; (2) the impact of the disability on an array of variables, spanning from physical fitness to well-being, quality of life, sleep, and nutritional aspects, among others, which are known to mediate/modulate the effects of exercise on human health; (3) the variability of the parameters related to the exercise/physical activity (modality, frequency, intensity, duration, training versus competition, etc.); and (4) the intra- and inter-individual variability of the immunological response to exercise. In able-bodied athletes, previously published data described several exercise-induced changes affecting various immunological subsets and subpopulations, ranging from neutrophils to lymphocytes, and monocytes. Broadly, moderate intensity workout is accompanied by optimal immunity and resistance to infections such as upper respiratory tract infections (URTI) in athletes. Periods of intense training with insufficient recovery can cause a temporary state of immunosuppression, which should end with a few days of rest/recovery from exercise. Disabled athletes are relatively overlooked and understudied with respect to their able-bodied counterparts. Findings from the few studies available on paralympic and disabled athletes are here summarized and analyzed utilizing a narrative approach to review and determine the major features of the immunological and inflammatory responses to exercise in this specific population. Moreover, a few studies have reported behavioral, dietary, and training strategies that can be adopted to limit exercise-induced immunosuppression and reduce the risk of infection in people with disabilities. However, given the paucity of data and contrasting findings, future high-quality investigations on paralympic and disabled athletes are urgently needed.

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.

Immune Regulatory Functions of Macrophages and Microglia in Central Nervous System Diseases

Macrophages can be characterized as a very multifunctional cell type with a spectrum of phenotypes and functions being observed spatially and temporally in various disease states. Ample studies have now demonstrated a possible causal link between macrophage activation and the development of autoimmune disorders. How these cells may be contributing to the adaptive immune response and potentially perpetuating the progression of neurodegenerative diseases and neural injuries is not fully understood. Within this review, we hope to illustrate the role that macrophages and microglia play as initiators of adaptive immune response in various CNS diseases by offering evidence of: (1) the types of immune responses and the processes of antigen presentation in each disease, (2) receptors involved in macrophage/microglial phagocytosis of disease-related cell debris or molecules, and, finally, (3) the implications of macrophages/microglia on the pathogenesis of the diseases.