Infiltrating blood-derived macrophages are vital cells playing an anti-inflammatory role in recovery from spinal cord injury in mice

Chemokine CX3CL1 (Fractalkine) Signaling and Diabetic Encephalopathy

Diabetes mellitus (DM) is the most common metabolic disease in humans, and its prevalence is increasing worldwide in parallel with the obesity pandemic. A lack of insulin or insulin resistance, and consequently hyperglycemia, leads to many systemic disorders, among which diabetic encephalopathy (DE) is a long-term complication of the central nervous system (CNS), characterized by cognitive impairment and motor dysfunctions. The role of oxidative stress and neuroinflammation in the pathomechanism of DE has been proven. Fractalkine (CX3CL1) has unique properties as an adhesion molecule and chemoattractant, and by acting on its only receptor, CX3CR1, it regulates the activity of microglia in physiological states and neuroinflammation. Depending on the clinical context, CX3CL1-CX3CR1 signaling may have neuroprotective effects by inhibiting the inflammatory process in microglia or, conversely, maintaining/intensifying inflammation and neurotoxicity. This review discusses the evidence supporting that the CX3CL1-CX3CR1 pair is neuroprotective and other evidence that it is neurotoxic. Therefore, interrupting the vicious cycle within neuron-microglia interactions by promoting neuroprotective effects or inhibiting the neurotoxic effects of the CX3CL1-CX3CR1 signaling axis may be a therapeutic goal in DE by limiting the inflammatory response. However, the optimal approach to prevent DE is simply tight glycemic control, because the elimination of dysglycemic states in the CNS abolishes the fundamental mechanisms that induce this vicious cycle.

Galectin-3 absence alters lymphocytes populations dynamics behavior and promotes functional recovery after spinal cord injury in mice

Spinal cord injury (SCI) results from various mechanisms that damage the nervous tissue and the blood-brain barrier, leading to sensory and motor function loss below the injury site. Unfortunately, current therapeutic approaches for SCI have limited efficacy in improving patients outcomes. Galectin-3, a protein whose expression increases after SCI, influences the neuroinflammatory response by favoring pro-inflammatory M1 macrophages and microglia, while inhibiting pro-regenerative M2 macrophages and microglia, which are crucial for inflammation resolution and tissue regeneration. Previous studies with Galectin-3 knock-out mice demonstrated enhanced motor recovery after SCI. The M1/M2 balance is strongly influenced by the predominant lymphocytic profiles (Th1, Th2, T Reg, Th17) and cytokines and chemokines released at the lesion site. The present study aimed to investigate how the absence of galectin-3 impacts the adaptive immune system cell population dynamics in various lymphoid spaces following a low thoracic spinal cord compression injury (T9-T10) using a 30 g vascular clip for one minute. It also aimed to assess its influence on the functional outcome in wild-type (WT)and Galectin-3 knock-out (GALNEG) mice. Histological analysis with hematoxylin-eosin and Luxol Fast Blue staining revealed that WT and GALNEG animals exhibit similar spinal cord morphology. The absence of galectin-3 does not affect the common neuroanatomy shared between the groups prompting us to analyze outcomes between both groups. Following our crush model, both groups lost motor and sensory functions below the lesion level. During a 42-day period, GALNEG mice demonstrated superior locomotor recovery in the Basso Mouse Scale (BMS) gait analysis and enhanced motor coordination performance in the ladder rung walk test (LRW) compared to WT mice. GALNEG mice also exhibited better sensory recovery, and their electrophysiological parameters suggested a higher number of functional axons with faster nerve conduction. Seven days after injury, flow cytometry of thymus, spleen, and blood revealed an increased number of T Reg and Th2 cells, accompanied by a decrease in Th1 and Th17 cells in GALNEG mice. Immunohistochemistry conducted on the same day exhibited an increased number of Th2 and T Reg cells around the GALNEG's spinal cord lesion site. At 42-day dpi immunohistochemistry analyses displayed reduced astrogliosis and greater axon preservation in GALNEG's spinal cord seem as a reduction of GFAP immunostaining and an increase in NFH immunostaining, respectively. In conclusion, GALNEG mice exhibited better functional recovery attributed to the milder pro-inflammatory influence, compensated by a higher quantity of T Reg and Th2 cells. These findings suggest that galectin-3 plays a crucial role in the immune response after spinal cord injury and could be a potential target for clinical therapeutic interventions.

Anatomical location of injected microglia in different activation states and time course of injury determines survival of retinal ganglion cells after optic nerve crush

Background: Activated microglia release harmful substances to retinal ganglion cells (RGCs), but may also benefit by removing cellular debris and secreting neurotrophic factors. These paradoxical roles remain controversial because the nature and time-course of the injury that defines their role is unknown. The aim of this study was to determine if pharmacological manipulation of microglia to acquire a pro-inflammatory or pro-survival phenotype will exacerbate or enhance neuronal survival after injury.Material and methods: Treated HAP I (highly aggressively proliferating immortalized) microglia were injected into the vitreous or tail vein (T V) of female Sprague-Dawley rats. Retinas were examined at 4-14 days following optic nerve crush (ONC) and the number of surviving RGCs was determined.Results: Injection of untreated HAP I cells resulted in the greater loss of RGCs early after ONC when injected into the vitreous and later after ONC when injected into the T V. LP S activated HAP I cells injected into the vitreous resulted in greater RGC loss with and without injury. When injected into the T V with ONC there was no loss of RGCs 4 days after ONC but greater loss afterwards. Minocycline treated HAP I cells injected into the vitreous resulted in greater RGC survival than untreated HAP I cells. However, when injected into the T V with ONC there was greater loss of RGCs. These results suggest that optic nerve signals attract extrinsic microglia to the retina, resulting in a proinflammatory response.Conclusion: Neuroprotection or cytotoxicity of microglia depends on the type of activation, time course of the injury, and if they act on the axon or cell body.

Elevated phagocytic capacity directs innate spinal cord repair

Immune cells elicit a continuum of transcriptional and functional states after spinal cord injury (SCI). In mammals, inefficient debris clearance and chronic inflammation impede recovery and overshadow pro-regenerative immune functions. We found that, unlike mammals, zebrafish SCI elicits transient immune activation and efficient debris clearance, without causing chronic inflammation. Single-cell transcriptomics and inducible genetic ablation showed zebrafish macrophages are highly phagocytic and required for regeneration. Cross-species comparisons between zebrafish and mammalian macrophages identified transcription and immune response regulator ( tcim ) as a macrophage-enriched zebrafish gene. Genetic deletion of zebrafish tcim impairs phagocytosis and regeneration, causes aberrant and chronic immune activation, and can be rescued by transplanting wild-type immune precursors into tcim mutants. Conversely, genetic expression of human TCIM accelerates debris clearance and regeneration by reprogramming myeloid precursors into activated phagocytes. This study establishes a central requirement for elevated phagocytic capacity to achieve innate spinal cord repair.

Early-wave macrophages control late hematopoiesis

Macrophages constitute the first defense line against the non-self, but their ability to remodel their environment in organ development/homeostasis is starting to be appreciated. Early-wave macrophages (EMs), produced from hematopoietic stem cell (HSC)-independent progenitors, seed the mammalian fetal liver niche wherein HSCs expand and differentiate. The involvement of niche defects in myeloid malignancies led us to identify the cues controlling HSCs. In Drosophila, HSC-independent EMs also colonize the larva when late hematopoiesis occurs. The evolutionarily conserved immune system allowed us to investigate whether/how EMs modulate late hematopoiesis in two models. We show that loss of EMs in Drosophila and mice accelerates late hematopoiesis, which does not correlate with inflammation and does not rely on macrophage phagocytic ability. Rather, EM-derived extracellular matrix components underlie late hematopoiesis acceleration. This demonstrates a developmental role for EMs.

The orphan G protein-coupled receptor 141 expressed in myeloid cells functions as an inflammation suppressor

G protein-coupled receptors (GPCRs) regulate many cellular processes in response to various stimuli, including light, hormones, neurotransmitters, and odorants, some of which play critical roles in innate and adaptive immune responses. However, the physiological functions of many GPCRs and the involvement of them in autoimmune diseases of the central nervous system remain unclear. Here, we demonstrate that GPR141, an orphan GPCR belonging to the class A receptor family, suppresses immune responses. High GPR141 messenger RNA levels were expressed in myeloid-lineage cells, including neutrophils (CD11b + Gr1+), monocytes (CD11b + Gr1-Ly6C+ and CD11b + Gr1-Ly6C-), macrophages (F4/80+), and dendritic cells (CD11c+). Gpr141  -/- mice, which we independently generated, displayed almost no abnormalities in myeloid cell differentiation and compartmentalization in the spleen and bone marrow under steady-state conditions. However, Gpr141 deficiency exacerbated disease conditions of experimental autoimmune encephalomyelitis, an autoimmune disease model for multiple sclerosis, with increased inflammation in the spinal cord. Gpr141  -/- mice showed increased CD11b + Gr1+ neutrophils, CD11b + Gr1- monocytes, CD11c+ dendritic cells, and CD4+ T cell infiltration into the experimental autoimmune encephalomyelitis-induced spinal cord compared with littermate control mice. Lymphocytes enriched from Gpr141  -/- mice immunized with myelin oligodendrocyte glycoprotein 35-55 produced high amounts of interferon-γ, interleukin-17A, and interleukin-6 compared with those from wild-type mice. Moreover, CD11c+ dendritic cells (DCs) purified from Gpr141  -/- mice increased cytokine production of myelin oligodendrocyte glycoprotein 35-55-specific T cells. These findings suggest that GPR141 functions as a negative regulator of immune responses by controlling the functions of monocytes and dendritic cells and that targeting GPR141 may be a possible therapeutic intervention for modulating chronic inflammatory diseases.

Blocking the Self-Destruct Program of Dopamine Neurons through Macrophage Migration Inhibitory Factor Nuclease Inhibition

Parkinson's disease (PD) is a progressive neurodegenerative condition that pathognomonically involves the death of dopaminergic neurons in the substantia nigra pars compacta, resulting in a myriad of motor and non-motor symptoms. Given the insurmountable burden of this disease on the population and healthcare system, significant efforts have been put forth toward generating disease modifying therapies. This class of treatments characteristically alters disease course, as opposed to current strategies that focus on managing symptoms. Previous literature has implicated the cell death pathway known as parthanatos in PD progression. Inhibition of this pathway by targeting poly (ADP)-ribose polymerase 1 (PARP1) prevents neurodegeneration in a model of idiopathic PD. However, PARP1 has a vast repertoire of functions within the body, increasing the probability of side effects with the long-term treatment likely necessary for clinically significant neuroprotection. Recent work culminated in the development of a novel agent targeting the macrophage migration inhibitory factor (MIF) nuclease domain, also named parthanatos-associated apoptosis-inducing factor nuclease (PAAN). This nuclease activity specifically executes the terminal step in parthanatos. Parthanatos-associated apoptosis-inducing factor nuclease inhibitor-1 was neuroprotective in multiple preclinical mouse models of PD. This piece will focus on contextualizing this discovery, emphasizing its significance, and discussing its potential implications for parthanatos-directed treatment. © 2024 International Parkinson and Movement Disorder Society.

Clickable Granular Hydrogel Scaffolds for Delivery of Neural Progenitor Cells to Sites of Spinal Cord Injury

Spinal cord injury (SCI) is a serious condition with limited treatment options. Neural progenitor cell (NPC) transplantation is a promising treatment option, and the identification of novel biomaterial scaffolds that support NPC engraftment and therapeutic activity is a top research priority. The objective of this study is to evaluate in situ assembled poly (ethylene glycol) (PEG)-based granular hydrogels for NPC delivery in a murine model of SCI. Microgel precursors are synthesized by using thiol-norbornene click chemistry to react four-armed PEG-amide-norbornene with enzymatically degradable and cell adhesive peptides. Unreacted norbornene groups are utilized for in situ assembly into scaffolds using a PEG-di-tetrazine linker. The granular hydrogel scaffolds exhibit good biocompatibility and do not adversely affect the inflammatory response after SCI. Moreover, when used to deliver NPCs, the granular hydrogel scaffolds supported NPC engraftment, do not adversely affect the immune response to the NPC grafts, and successfully support graft differentiation toward neuronal or astrocytic lineages as well as axonal extension into the host tissue. Collectively, these data establish PEG-based granular hydrogel scaffolds as a suitable biomaterial platform for NPC delivery and justify further testing, particularly in the context of more severe SCI.

Prognostic value of the systemic inflammatory index (SII) and systemic inflammatory response index (SIRI) in patients with traumatic spinal cord injury

PURPOSE

The overwhelming inflammatory response plays a critical role in the secondary injury cascade of traumatic spinal cord injury (tSCI). The systemic immune inflammatory index (SII) and systemic inflammatory response index (SIRI) are two novel inflammatory biomarkers. The SII was calculated based on lymphocyte, neutrophil, and platelet counts, while the SIRI was calculated based on lymphocyte, neutrophil, and monocyte counts. Their prognostic value in patients with tSCI remains unclear.

METHODS

Patients with tSCI admitted within 24 h of trauma were retrospectively and consecutively enrolled. Peripheral blood samples were collected on admission. The primary outcome was American Spinal Injury Association Impairment Scale (AIS) grade conversion at discharge. Multivariable logistic regression analysis was performed to determine the relationship between SII and SIRI and AIS grade conversion. We performed receiver operating characteristic curve (ROC) analysis to assess the discriminative ability of SII, and SIRI in predicting AIS grade conversion.

RESULTS

Among 280 included patients, 77 (27.5%) had improved AIS grade conversion at discharge. After adjustment for confounders, SII was independently associated with AIS grade conversion (per SD, odds ratio [OR], 0.68; 95% confidence interval [CI] 0.47-0.98, p = 0.040), while the association between SIRI and AIS grade conversion was insignificant (per 1 SD, OR, 0.77; 95% CI 0.55-1.08, p = 0.130). The ROC analysis revealed that the SII had the best predictive value for AIS grade conversion (area under curve: 0.608, 95% CI 0.536-0.678).

CONCLUSIONS

Increased SII was independently associated with a decreased likelihood of improved AIS grade conversion.

Inhibition of HDAC6 promotes microvascular endothelial cells to phagocytize myelin debris and reduces inflammatory response to accelerate the repair of spinal cord injury

AIMS

To identify an effective strategy for promoting microvascular endothelial cells (MECs) to phagocytize myelin debris and reduce secretion of inflammatory factors following spinal cord injury (SCI).

METHODS

We established a coculture model of myelin debris and vascular-like structures. The efficiency with which MECs phagocytize myelin debris under different conditions was examined via ELISA, flow cytometry, and immunofluorescence. Tubastatin-A was used to interfere with the coculture model. The anti-inflammatory effects of Tubastatin-A were observed by HE staining, flow cytometry, immunofluorescence, and ELISA.

RESULTS

MECs phagocytized myelin debris via IgM opsonization, and phagocytosis promoted the secretion of inflammatory factors, whereas IgG-opsonized myelin debris had no effect on inflammatory factors. Application of the HDAC6 inhibitor Tubastatin-A increased the IgG levels and decreased the IgM levels by regulating the proliferation and differentiation of B cells. Tubastatin-A exerted a regulatory effect on the HDAC6-mediated autophagy-lysosome pathway, promoting MECs to phagocytize myelin debris, reducing the secretion of inflammatory factors, and accelerating the repair of SCI.

CONCLUSIONS

Inhibition of HDAC6 to regulate the immune-inflammatory response and promote MECs to phagocytize myelin debris may represent a novel strategy in the treatment of SCI.

Single-cell RNA sequencing reveals peripheral blood leukocyte responses to spinal cord injury in mice with humanised immune systems

Next-generation humanised mouse models and single-cell RNA sequencing (scRNAseq) approaches enable in-depth studies into human immune cell biology. Here we used NSG-SGM3 mice engrafted with human umbilical cord haematopoietic stem cells to investigate how human immune cells respond to and/or are changed by traumatic spinal cord injury (SCI). We hypothesised that the use of such mice could help advance our understanding of spinal cord injury-induced immune depression syndrome (SCI-IDS), and also how human leukocytes change as they migrate from the circulation into the lesion site. Our scRNAseq experiments, supplemented by flow cytometry, demonstrate the existence of up to 11 human immune cell (sub-) types and/or states across the blood and injured spinal cord (7 days post-SCI) of humanised NSG-SGM3 mice. Further comparisons of human immune cell transcriptomes between naïve, sham-operated and SCI mice identified a total of 579 differentially expressed genes, 190 of which were 'SCI-specific' (that is, genes regulated only in response to SCI but not sham surgery). Gene ontology analysis showed a prominent downregulation of immune cell function under SCI conditions, including for T cell receptor signalling and antigen presentation, confirming the presence of SCI-IDS and the transcriptional signature of human leukocytes in association with this phenomenon. We also highlight the activating influence of the local spinal cord lesion microenvironment by comparing the transcriptomes of circulating versus infiltrated human immune cells; those isolated from the lesion site were enriched for genes relating to both immune cell activity and function (e.g., oxidative phosphorylation, T cell proliferation and antigen presentation). We lastly applied an integrated bioinformatics approach to determine where immune responses in humanised NSG-SGM3 mice appear congruent to the native responses of human SCI patients, and where they diverge. Collectively, our study provides a valuable resource and methodological framework for the use of these mice in translational research.

Advanced patient-specific microglia cell models for pre-clinical studies in Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is an incurable neurodegenerative disorder with a rapidly increasing prevalence worldwide. Current approaches targeting hallmark pathological features of AD have had no consistent clinical benefit. Neuroinflammation is a major contributor to neurodegeneration and hence, microglia, the brain's resident immune cells, are an attractive target for potentially more effective therapeutic strategies. However, there is no current in vitro model system that captures AD patient-specific microglial characteristics using physiologically relevant and experimentally flexible culture conditions.

METHODS

To address this shortcoming, we developed novel 3D Matrigel-based monocyte-derived microglia-like cell (MDMi) mono-cultures and co-cultures with neuro-glial cells (ReNcell VM). We used single-cell RNA sequencing (scRNAseq) analysis to compare the transcriptomic signatures of MDMi between model systems (2D, 3D and 3D co-culture) and against published human microglia datasets. To demonstrate the potential of MDMi for use in personalized pre-clinical strategies, we generated and characterized MDMi models from sixteen AD patients and matched healthy controls, and profiled cytokine responses upon treatment with anti-inflammatory drugs (dasatinib and spiperone).

RESULTS

MDMi in 3D exhibited a more branched morphology and longer survival in culture compared to 2D. scRNAseq uncovered distinct MDMi subpopulations that exhibit higher functional heterogeneity and best resemble human microglia in 3D co-culture. AD MDMi in 3D co-culture showed altered cell-to-cell interactions, growth factor and cytokine secretion profiles and responses to amyloid-β. Drug testing assays revealed patient- and model-specific cytokine responses.

CONCLUSION

Our study presents a novel, physiologically relevant and AD patient-specific 3D microglia cell model that opens avenues towards improving personalized drug development strategies in AD.

Spinal Neuronal miR-124 Inhibits Microglial Activation and Contributes to Preventive Effect of Electroacupuncture on Chemotherapy-Induced Peripheral Neuropathy in Mice

Chemotherapy-induced peripheral neuropathy (CIPN) is a persistent and irreversible side effect of antineoplastic agents. Patients with CIPN usually show chronic pain and sensory deficits with glove-and-stocking distribution. However, whether spinal neuronal microRNA (miR)-124 is involved in cisplatin-induced peripheral neuropathy remains to be studied. In this study, miR-124 was significantly reduced in the spinal dorsal horn in CIPN mice. Overexpression of neuronal miR-124 induced by injecting adeno-associated virus with neuron-specific promoter into the spinal cord of mice prevented the development of mechanical allodynia, sensory deficits, and the loss of intraepidermal nerve fibers induced by cisplatin. Meanwhile, cisplatin-induced M1 microglia activation and the release of proinflammatory cytokines were significantly inhibited by overexpression of neuronal miR-124. Furthermore, electroacupuncture (EA) treatment upregulated miR-124 expression in the spinal dorsal horn of CIPN mice. Interestingly, downregulation of spinal neuronal miR-124 significantly inhibited the regulatory effect of EA on CIPN and microglia activity as well as spinal neuroinflammation induced by cisplatin. These results demonstrate that spinal neuronal miR-124 is involved in the prevention and treatment of EA on cisplatin-induced peripheral neuropathy in mice. Our findings suggest that spinal neuronal miR-124 might be a potential target for EA effect, and we provide, to our knowledge, a new experimental basis for EA prevention of CIPN.

Choroid plexus volume is increased in mood disorders and associates with circulating inflammatory cytokines

Depressed patients exhibit altered levels of immune-inflammatory markers both in the peripheral blood and in the cerebrospinal fluid (CSF) and inflammatory processes have been widely implicated in the pathophysiology of mood disorders. The Choroid Plexus (ChP), located at the base of each of the four brain ventricles, regulates the exchange of substances between the blood and CSF and several evidence supported a key role for ChP as a neuro-immunological interface between the brain and circulating immune cells. Given the role of ChP as a regulatory gate between periphery, CSF spaces and the brain, we compared ChP volumes in patients with bipolar disorder (BP) or major depressive disorder (MDD) and healthy controls, exploring their association with history of illness and levels of circulating cytokines. Plasma levels of inflammatory markers and MRI scans were acquired for 73 MDD, 79 BD and 72 age- and sex-matched healthy controls (HC). Patients with either BD or MDD had higher ChP volumes than HC. With increasing age, the bilateral ChP volume was larger in patients, an effect driven by the duration of illness; while only minor effects were observed in HC. Right ChP volumes were proportional to higher levels of circulating cytokines in the clinical groups, including IFN-γ, IL-13 and IL-17. Specific effects in the two diagnostic groups were observed when considering the left ChP, with positive association with IL-1ra, IL-13, IL-17, and CCL3 in BD, and negative associations with IL-2, IL-4, IL-1ra, and IFN-γ in MDD. These results suggest that ChP could represent a reliable and easy-to-assess biomarker to evaluate the brain effects of inflammatory status in mood disorders, contributing to personalized diagnosis and tailored treatment strategies.

The Role of Interleukin-10 in the Pathogenesis and Treatment of a Spinal Cord Injury

Spinal cord injury (SCI) is a devastating condition that often leads to severe and permanent neurological deficits. The complex pathophysiology of an SCI involves a cascade of events, including inflammation, oxidative stress, and secondary injury processes. Among the myriad of molecular players involved, interleukin-10 (IL-10) emerges as a key regulator with the potential to modulate both the inflammatory response and promote neuroprotection. This comprehensive review delves into the intricate interplay of IL-10 in the pathogenesis of an SCI and explores its therapeutic implications in the quest for effective treatments. IL-10 has been found to regulate inflammation, oxidative stress, neuronal apoptosis, and glial scars after an SCI. Its neuroprotective properties have been evaluated in a plethora of animal studies. IL-10 administration, either isolated or in combination with other molecules or biomaterials, has shown neuroprotective effects through a reduction in inflammation, the promotion of tissue repair and regeneration, the modulation of glial scar formation, and improved functional outcomes. In conclusion, IL-10 emerges as a pivotal player in the pathogenesis and treatment of SCIs. Its multifaceted role in modulating inflammation, oxidative stress, neuronal apoptosis, glial scars, and neuroprotection positions IL-10 as a promising therapeutic target. The ongoing research exploring various strategies for harnessing the potential of IL-10 offers hope for the development of effective treatments that could significantly improve outcomes for individuals suffering from spinal cord injuries. As our understanding of IL-10's intricacies deepens, it opens new avenues for innovative and targeted therapeutic interventions, bringing us closer to the goal of alleviating the profound impact of SCIs on patients' lives.

Not just Glia-Dissecting brain macrophages in the mouse

Macrophages have emerged as critical cellular components of the central nervous system (CNS), promoting development, maintenance, and immune defense of the CNS. Here we will review recent advances in our understanding of brain macrophage heterogeneity, including microglia and border-associated macrophages, focusing on the mouse. Emphasis will be given to the discussion of strengths and limitations of the experimental approaches that have led to the recent insights and hold promise to further deepen our mechanistic understanding of brain macrophages that might eventually allow to harness their activities for the management of CNS pathologies.

Signalling Pathways Involved in Microglial Activation in Alzheimer's Disease and Potential Neuroprotective Role of Phytoconstituents

Alzheimer's disease (AD) is a commonly reported neurodegenerative disorder associated with dementia and cognitive impairment. The pathophysiology of AD comprises Aβ, hyperphosphorylated tau protein formation, abrupt cholinergic cascade, oxidative stress, neuronal apoptosis, and neuroinflammation. Recent findings have established the profound role of immunological dysfunction and microglial activation in the pathogenesis of AD. Microglial activation is a multifactorial cascade encompassing various signalling molecules and pathways such as Nrf2/NLRP3/NF-kB/p38 MAPKs/ GSK-3β. Additionally, deposited Aβ or tau protein triggers microglial activation and accelerates its pathogenesis. Currently, the FDA-approved therapeutic regimens are based on the modulation of the cholinergic system, and recently, one more drug, aducanumab, has been approved by the FDA. On the one hand, these drugs only offer symptomatic relief and not a cure for AD. Additionally, no targetedbased microglial medicines are available for treating and managing AD. On the other hand, various natural products have been explored for the possible anti-Alzheimer effect via targeting microglial activation or different targets of microglial activation. Therefore, the present review focuses on exploring the mechanism and associated signalling related to microglial activation and a detailed description of various natural products that have previously been reported with anti-Alzheimer's effect via mitigation of microglial activation. Additionally, we have discussed the various patents and clinical trials related to managing and treating AD.

Development and characterisation of mgTHP-1, a novel in vitro model for neural macrophages with microglial characteristics

Neuroinflammation is primarily characterised by activation of the brain's resident macrophages - the microglia. However, other central nervous system (CNS) cells also contribute to this response, including the astrocytes and endothelial cells. In addition, there is infiltration into the CNS of peripherally derived immune cells. Together these cells mediate inflammation by the production of cytokines, chemokines, reactive oxygen species, and secondary messengers, and enacting of the appropriate response to those signals. However, deciphering the specific contributions of each cell type has been challenging. Studying CNS cell biology is often challenging, as the isolation of primary cells is not always feasible, and differentiation towards microglia-like cells is complex. Here, we demonstrate a novel method whereby THP-1 monocytic cells are differentiated into neural macrophage cells with microglia-like cell characteristics. The cells, designated mgTHP-1, show typical morphological and gene expression patterns of resident CNS macrophages and functionally respond to inflammatory stimuli by producing inflammatory cytokines. Furthermore, with the addition of Vicenin-2 (an anti-inflammatory flavonoid) such responses can be reversed. This novel cell model will allow further investigations, and hence insights, into the neuroinflammatory mechanisms associated with CNS diseases.

Vital role for primary healthcare providers: urgent need to educate the community about daily nutritional self-care to support immune function and maintain health

The importance of self-care to improve health and social well-being is well recognised. Nevertheless, there remains a need to encourage people to better understand how their body works, and how to keep it healthy. Because of its important role, part of this understanding should be based on why the immune system must be supported. This highly complex system is essential for defending against pathogens, but also for maintaining health throughout the body by preserving homeostasis and integrity. Accordingly, the immune system requires active management for optimal functioning and to reduce the risk of chronic diseases. In addition to regular exercise, healthy sleeping patterns, cultivating mental resilience, adequate nutrition through healthy and diverse dietary habits is key to the daily support of immune function. Diet and the immune system are closely intertwined, and a poor diet will impair immunity and increase the risk of acute and chronic diseases. To help elucidate the roles of primary healthcare providers in supporting individuals to engage in self-care, an international group of experts reviewed the evidence for the roles of the immune system in maintaining health and for nutrition in daily immune support, and discussed implications for population health and clinical practice.

Macrophage polarization in spinal cord injury repair and the possible role of microRNAs: A review

The prevention, treatment, and rehabilitation of spinal cord injury (SCI) have always posed significant medical challenges. After mechanical injury, disturbances in microcirculation, edema formation, and the generation of free radicals lead to additional damage, impeding effective repair processes and potentially exacerbating further dysfunction. In this context, inflammatory responses, especially the activation of macrophages, play a pivotal role. Different phenotypes of macrophages have distinct effects on inflammation. Activation of classical macrophage cells (M1) promotes inflammation, while activation of alternative macrophage cells (M2) inhibits inflammation. The polarization of macrophages is crucial for disease healing. A non-coding RNA, known as microRNA (miRNA), governs the polarization of macrophages, thereby reducing inflammation following SCI and facilitating functional recovery. This study elucidates the inflammatory response to SCI, focusing on the infiltration of immune cells, specifically macrophages. It examines their phenotype and provides an explanation of their polarization mechanisms. Finally, this paper introduces several well-known miRNAs that contribute to macrophage polarization following SCI, including miR-155, miR-130a, and miR-27 for M1 polarization, as well as miR-22, miR-146a, miR-21, miR-124, miR-223, miR-93, miR-132, and miR-34a for M2 polarization. The emphasis is placed on their potential therapeutic role in SCI by modulating macrophage polarization, as well as the present developments and obstacles of miRNA clinical therapy.

The role and mechanisms of mesenchymal stem cells regulating macrophage plasticity in spinal cord injury

Spinal Cord Injury (SCI) is a devastating neurological disorder comprising primary mechanical injury and secondary inflammatory response-mediated injury for which an effective treatment is still unavailable. It is well known that secondary inflammatory responses are a significant cause of difficulties in neurological recovery. An immune imbalance between M1/M2 macrophages at the sites of injury is involved in developing and progressing the secondary inflammatory response. Recently, Mesenchymal Stem Cells (MSCs) have shown significant therapeutic potential in tissue engineering and regenerative medicine due to their potential multidirectional differentiation and immunomodulatory properties. Accumulating evidence shows that MSCs can regulate the balance of M1/M2 macrophage polarization, suppress downstream inflammatory responses, facilitate tissue repair and regeneration, and improve the prognosis of SCI. This article briefly overviews the impact of macrophages and MSCs on SCI and repair. It discusses the mechanisms by which MSCs regulate macrophage plasticity, including paracrine action, release of exosomes and apoptotic bodies, and metabolic reprogramming. Additionally, the article summarizes the relevant signaling pathways of MSCs that regulate macrophage polarization.

Brain macrophage development, diversity and dysregulation in health and disease

Brain macrophages include microglia in the parenchyma, border-associated macrophages in the meningeal-choroid plexus-perivascular space, and monocyte-derived macrophages that infiltrate the brain under various disease conditions. The vast heterogeneity of these cells has been elucidated over the last decade using revolutionary multiomics technologies. As such, we can now start to define these various macrophage populations according to their ontogeny and their diverse functional programs during brain development, homeostasis and disease pathogenesis. In this review, we first outline the critical roles played by brain macrophages during development and healthy aging. We then discuss how brain macrophages might undergo reprogramming and contribute to neurodegenerative disorders, autoimmune diseases, and glioma. Finally, we speculate about the most recent and ongoing discoveries that are prompting translational attempts to leverage brain macrophages as prognostic markers or therapeutic targets for diseases that affect the brain.

The role of astrocytes response triggered by hyperglycaemia during spinal cord injury

Objective: This manuscript aimed to provide a comprehensive overview of the physiological, molecular, and cellular mechanisms triggered by reactive astrocytes (RA) in the context of spinal cord injury (SCI), with a particular focus on cases involving hyperglycaemia.Methods: The compilation of articles related to astrocyte responses in neuropathological conditions, with a specific emphasis on those related to SCI and hyperglycaemia, was conducted by searching through databases including Science Direct, Web of Science, and PubMed.Results and Conclusions: This article explores the dual role of astrocytes in both neurophysiological and neurodegenerative conditions within the central nervous system (CNS). In the aftermath of SCI and hyperglycaemia, astrocytes undergo a transformation into RA, adopting a distinct phenotype. While there are currently no approved therapies for SCI, various therapeutic strategies have been proposed to alleviate the detrimental effects of RAs following SCI and hyperglycemia. These strategies show promising potential in the treatment of SCI and its likely comorbidities.

Administration of recombinant FOXN1 protein attenuates Alzheimer's pathology in mice

BACKGROUND

Alzheimer's disease (AD) is the most common cause of dementia in older adults and characterized by progressive loss of memory and cognitive functions that are associated with amyloid-beta (Aβ) plaques and neurofibrillary tangles. Immune cells play an important role in the clearance of Aβ deposits and neurofibrillary tangles. T cells are the major component of the immune system. The thymus is the primary organ for T cell generation. T cell development in the thymus depends on thymic epithelial cells (TECs). However, TECs undergo both qualitative and quantitative loss over time. We have previously reported that a recombinant (r) protein containing FOXN1 and a protein transduction domain can increase the number of TECs and subsequently increases the number of T cells in mice. In this study we determined the ability of rFOXN1 to affect cognitive performance and AD pathology in mice.

METHODS

Aged 3xTg-AD and APP/PS1 AD mice were injected with rFOXN1 or control protein. Cognitive performance, AD pathology, the thymic microenvironment and immune cells were then analyzed.

RESULTS

Administration of rFOXN1 into AD mice improves cognitive performance and reduces Aβ plaque load and phosphorylated tau in the brain. This is related to rejuvenating the aged thymic microenvironment, which results in enhanced T cell generation in the thymus, leading to increased number of T cells, especially IFNγ-producing T cells, in the spleen and the choroid plexus (CP), enhanced expression of immune cell trafficking molecules in the CP, and increased migration of monocyte-derived macrophages into the brain. Furthermore, the production of anti-Aβ antibodies in the serum and the brain, and the macrophage phagocytosis of Aβ are enhanced in rFOXN1-treated AD mice.

CONCLUSIONS

Our results suggest that rFOXN1 protein has the potential to provide a novel approach to treat AD patients.

The NF-κB Pathway: a Focus on Inflammatory Responses in Spinal Cord Injury

Spinal cord injury (SCI) is a type of central nervous system trauma that can lead to severe nerve injury. Inflammatory reaction after injury is an important pathological process leading to secondary injury. Long-term stimulation of inflammation can further deteriorate the microenvironment of the injured site, leading to the deterioration of neural function. Understanding the signaling pathways that regulate responses after SCI, especially inflammatory responses, is critical for the development of new therapeutic targets and approaches. Nuclear transfer factor-κB (NF-κB) has long been recognized as a key factor in regulating inflammatory responses. The NF-κB pathway is closely related to the pathological process of SCI. Inhibition of this pathway can improve the inflammatory microenvironment and promote the recovery of neural function after SCI. Therefore, the NF-κB pathway may be a potential therapeutic target for SCI. This article reviews the mechanism of inflammatory response after SCI and the characteristics of NF-κB pathway, emphasizing the effect of inhibiting NF-κB on the inflammatory response of SCI to provide a theoretical basis for the biological treatment of SCI.

Beyond the amyloid hypothesis: how current research implicates autoimmunity in Alzheimer's disease pathogenesis

The amyloid hypothesis has so far been at the forefront of explaining the pathogenesis of Alzheimer's Disease (AD), a progressive neurodegenerative disorder that leads to cognitive decline and eventual death. Recent evidence, however, points to additional factors that contribute to the pathogenesis of this disease. These include the neurovascular hypothesis, the mitochondrial cascade hypothesis, the inflammatory hypothesis, the prion hypothesis, the mutational accumulation hypothesis, and the autoimmunity hypothesis. The purpose of this review was to briefly discuss the factors that are associated with autoimmunity in humans, including sex, the gut and lung microbiomes, age, genetics, and environmental factors. Subsequently, it was to examine the rise of autoimmune phenomena in AD, which can be instigated by a blood-brain barrier breakdown, pathogen infections, and dysfunction of the glymphatic system. Lastly, it was to discuss the various ways by which immune system dysregulation leads to AD, immunomodulating therapies, and future directions in the field of autoimmunity and neurodegeneration. A comprehensive account of the recent research done in the field was extracted from PubMed on 31 January 2022, with the keywords "Alzheimer's disease" and "autoantibodies" for the first search input, and "Alzheimer's disease" with "IgG" for the second. From the first search, 19 papers were selected, because they contained recent research on the autoantibodies found in the biofluids of patients with AD. From the second search, four papers were selected. The analysis of the literature has led to support the autoimmune hypothesis in AD. Autoantibodies were found in biofluids (serum/plasma, cerebrospinal fluid) of patients with AD with multiple methods, including ELISA, Mass Spectrometry, and microarray analysis. Through continuous research, the understanding of the synergistic effects of the various components that lead to AD will pave the way for better therapeutic methods and a deeper understanding of the disease.

Dexamethasone Liposomes Alleviate Osteoarthritis in miR-204/-211-Deficient Mice by Repolarizing Synovial Macrophages to M2 Phenotypes

We undertook this study to investigate the effects and mechanisms of dexamethasone liposome (Dex-Lips) on alleviating destabilization of the medial meniscus (DMM)-induced osteoarthritis (OA) in miR-204/-211-deficient mice. Dex-Lips was prepared by the thin-film hydration method. The characterization of Dex-Lips was identified by the mean size, zeta potential, drug loading, and encapsulation efficiencies. Experimental OA was established by DMM surgery in miR-204/-211-deficient mice, and then Dex-Lips was treated once a week for 3 months. Von Frey filaments was used to perform the pain test. The inflammation level was evaluated with quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assay. Polarization of macrophages was evaluated by immunofluorescent staining. X-ray, micro-CT scanning, and histological observations were conducted in vivo on DMM mice to describe the OA phenotype. We found that miR-204/-211-deficient mice displayed more severe OA symptoms than WT mice after DMM surgery. Dex-Lips ameliorated DMM-induced OA phenotype and suppressed pain and inflammatory cytokine expressions. Dex-Lips could attenuate pain by regulating PGE2. Dex-Lips treatments reduced the expression of TNF-α, IL-1β, and IL-6 in DRG. Moreover, Dex-Lips could reduce inflammation in the cartilage and serum. Additionally, Dex-Lips repolarize synovial macrophages to M2 phenotypes in miR-204/-211-deficient mice. In conclusion, Dex-Lips inhibited the inflammatory response and alleviated the pain symptoms of OA by affecting the polarization of macrophages.

Age-dependent immune and lymphatic responses after spinal cord injury

Spinal cord injury (SCI) causes lifelong debilitating conditions. Previous works demonstrated the essential role of the immune system in recovery after SCI. Here, we explored the temporal changes of the response after SCI in young and aged mice in order to characterize multiple immune populations within the mammalian spinal cord. We revealed substantial infiltration of myeloid cells to the spinal cord in young animals, accompanied by changes in the activation state of microglia. In contrast, both processes were blunted in aged mice. Interestingly, we discovered the formation of meningeal lymphatic structures above the lesion site, and their role has not been examined after contusive injury. Our transcriptomic data predicted lymphangiogenic signaling between myeloid cells in the spinal cord and lymphatic endothelial cells (LECs) in the meninges after SCI. Together, our findings delineate how aging affects the immune response following SCI and highlight the participation of the spinal cord meninges in supporting vascular repair.

Early-phase rotator training impairs tissue repair and functional recovery after spinal cord injury

Spinal cord injury (SCI) is a devastating disorder that often results in severe sensorimotor function impairment with limited recovery of function. In recent years, rehabilitation training for spinal cord injury has gradually emerged, and some of them play an important role in the repair of spinal cord injury However, the optimal training regimen for SCI remains to be determined. In this study, we explore the effects of rotarod training (began at 7 days post-injury) on the recovery of motor function after SCI, as well as its possible repair mechanism from the aspects of function and histopathological changes, the behaviors of specific trophic factors and cytokines, and the expression profile of specific genes. Multiple functional assessments showed that rotarod training initiated at 7 days post-injury is unsuitable for promoting neuro-electrophysiological improvement and trunk stability, but impaired functional coordination and motor recovery. In addition, rotarod training has negative effects on spinal cord repair after SCI, which is manifested as an increase of lesion area, a decrease in neuronal viability, a deterioration in immuno-microenvironment and remyelination, a significant reduction in the expression of trophic factors and an increase in the expression of pro-inflammatory factors. RNA sequencing suggested that the genes associated with angiogenesis and synaptogenesis were significantly downregulated and the PI3K-AKT pathway was inhibited, which was detrimental to spinal cord repair and impeded nerve regeneration. These results indicate that immediate rotarod training after SCI is currently unsuitable for rehabilitation in mice.

Endothelial progenitor cell-derived exosomes promote anti-inflammatory macrophages via SOCS3/JAK2/STAT3 axis and improve the outcome of spinal cord injury

BACKGROUND

Macrophage in the spinal cord injury (SCI) area imparts a chronic pro-inflammation effect that challenges the recovery of SCI. Previously, endothelial progenitor cell-produced exosomes (EPC-EXOs) have been noticed to facilitate revascularization and inflammation control after SCI. However, their effects on macrophage polarization remained unclear. This study aimed to investigate the EPC-EXOs' role in macrophage polarization and reveal its underlying mechanism.

METHODS

We extracted the macrophages and EPC from the bone marrow suspension of C57BL/L mice by centrifugation. After cell identification, the EPC-EXOs were collected by ultra-high-speed centrifugation and exosome extraction kits and identified by transmission electron microscopy and nanoparticle tracking analysis. Then, macrophages were cultured with EPC-EXOs in different concentrations. We labeled the exosome to confirm its internalization by macrophage and detected the macrophage polarization marker level both in vitro and in vivo. We further estimated EPC-EXOs' protective effects on SCI by mice spinal cord tissue H&E staining and motor behavior evaluation. Finally, we performed RT-qPCR to identify the upregulated miRNA in EPC-EXOs and manipulate its expression to estimate its role in macrophage polarization, SOCS3/JAK2/STAT3 pathway activation, and motor behavior improvement.

RESULTS

We found that EPC-EXOs decreased the macrophages' pro-inflammatory marker expression and increased their anti-inflammatory marker expression on the 7 and 14 days after SCI. The spinal cord H&E staining results showed that EPC-EXOs raised the tissue-sparing area rate significantly after 28 days of SCI and the motor behavior evaluation indicated an increased BMS score and motor-evoked potential by EPC-EXOs treatment after SCI. The RT-qPCR assay identified that miR-222-3P upregulated in EPC-EXOs and its miRNA-mimic also decreased the pro-inflammatory macrophages and increased the anti-inflammatory macrophages. Additionally, miR-222-3P mimic activated the SOCS3/JAK2/STAT3 pathway, and SOCS3/JAK2/STAT3 pathway inhibition blocked miR-2223P's effects on macrophage polarization and mouse motor behavior.

CONCLUSION

Comprehensively, we discovered that EPC-EXOs-derived miR-222-3p affected macrophage polarization via SOCS3/JAK2/STAT3 pathway and promoted mouse functional repair after SCI, which reveals EPC-EXOs' role in modulation of macrophage phenotype and will provide a novel interventional strategy to induce post-SCI recovery.

Immune stimulation recruits a subset of pro-regenerative macrophages to the retina that promotes axonal regrowth of injured neurons

The multifaceted nature of neuroinflammation is highlighted by its ability to both aggravate and promote neuronal health. While in mammals retinal ganglion cells (RGCs) are unable to regenerate following injury, acute inflammation can induce axonal regrowth. However, the nature of the cells, cellular states and signalling pathways that drive this inflammation-induced regeneration have remained elusive. Here, we investigated the functional significance of macrophages during RGC de- and regeneration, by characterizing the inflammatory cascade evoked by optic nerve crush (ONC) injury, with or without local inflammatory stimulation in the vitreous. By combining single-cell RNA sequencing and fate mapping approaches, we elucidated the response of retinal microglia and recruited monocyte-derived macrophages (MDMs) to RGC injury. Importantly, inflammatory stimulation recruited large numbers of MDMs to the retina, which exhibited long-term engraftment and promoted axonal regrowth. Ligand-receptor analysis highlighted a subset of recruited macrophages that exhibited expression of pro-regenerative secreted factors, which were able to promote axon regrowth via paracrine signalling. Our work reveals how inflammation may promote CNS regeneration by modulating innate immune responses, providing a rationale for macrophage-centred strategies for driving neuronal repair following injury and disease.

Tackling the glial scar in spinal cord regeneration: new discoveries and future directions

Axonal regeneration and functional recovery are poor after spinal cord injury (SCI), typified by the formation of an injury scar. While this scar was traditionally believed to be primarily responsible for axonal regeneration failure, current knowledge takes a more holistic approach that considers the intrinsic growth capacity of axons. Targeting the SCI scar has also not reproducibly yielded nearly the same efficacy in animal models compared to these neuron-directed approaches. These results suggest that the major reason behind central nervous system (CNS) regeneration failure is not the injury scar but a failure to stimulate axon growth adequately. These findings raise questions about whether targeting neuroinflammation and glial scarring still constitute viable translational avenues. We provide a comprehensive review of the dual role of neuroinflammation and scarring after SCI and how future research can produce therapeutic strategies targeting the hurdles to axonal regeneration posed by these processes without compromising neuroprotection.

Architecture-Engineered Electrospinning Cascade Regulates Spinal Microenvironment to Promote Nerve Regeneration

The inflammatory cascade after spinal cord injury (SCI) causes necrotizing apoptosis of local stem cells, which limits nerve regeneration. Therefore, coordinating the inflammatory immune response and neural stem cell (NSC) functions is key to promoting the recovery of central nervous system function. In this study, a hydrogel "perfusion" system and electrospinning technology are integrated, and a "concrete" composite support for the repair of nerve injuries is built. The hydrogel's hydrophilic properties activate macrophage integrin receptors to mediate polarization into anti-inflammatory subtypes and cause a 10% increase in polarized M2 macrophages, thus reprogramming the SCI immune microenvironment. Programmed stromal cell-derived factor-1α and brain-derived neurotrophic factor released from the composite increase recruitment and neuronal differentiation of NSCs by approximately four- and twofold, respectively. The fiber system regulates the SCI immune inflammatory microenvironment, recruits endogenous NSCs, promotes local blood vessel germination and maturation, and improves nerve function recovery in a rat SCI model. In conclusion, the engineering fiber composite improves the local inflammatory response. It promotes nerve regeneration through a hydrophilic programmed cytokine-delivery system, which further improves and supplements the immune response mechanism regulated by the inherent properties of the biomaterial. The new fiber composite may serve as a new treatment approach for SCI.

The Role of T Cells in Alzheimer's Disease Pathogenesis

Alzheimer's disease (AD) is a progressive neurodegenerative disorder associated with memory decline and cognitive impairment, which is related to hallmark protein aggregates, amyloid-β (Аβ) plaques and neurofibrillary tangles; the latter are accumulated with hyperphosphorylated Tau protein. Immune cells play an important role in AD pathogenesis. Although the role of T cells in AD remains controversial, studies have shown that T cell deficiency is associated with increased AD pathology. In contrast, transplantation of T cells reduces AD pathology. T cells can help B cells generate anti-Аβ antibody to neutralize the toxin of Аβ and hyperphosphorylated Tau. T cells also activate macrophages to phagocytose misfolded proteins including Аβ and Tau. Recent data have also shown that AD animals have a damaged thymic microenvironment, especially thymic epithelial cells (TECs), resulting in decreased T cell numbers, which contribute to AD pathology. Therefore, regulation of T cell regeneration, for example by rejuvenating the thymic microenvironment, has the potential to be used in the treatment of AD.

Revisiting the immune landscape post spinal cord injury: More than black and white

Spinal cord injury (SCI) induced catastrophic neurological disability is currently incurable, especially in elderly patients. Due to the limited axon regeneration capacity and hostile microenvironment in the lesion site, essential neural network reconstruction remains challenging. Owing to the blood-spinal cord barrier (BSCB) created immune cells and cytokines isolation, the immune elements were incorrectly recognized as innocent bystanders during the SCI pathological process traditionally. Emerging evidence demonstrated that the central nervous system (CNS) is an "immunological quiescent" rather than "immune privileged" area, and the CNS-associated immune response played mixed roles which dedicate beneficial and detrimental contributions throughout the SCI process. Consequently, coordinating double-edged immunomodulation is vital to promote tissue repair and neurological recovery post-SCI. The comprehensive exploration and understanding of the immune landscape post-SCI are essential in establishing new avenues for further basic and clinical studies. In this context, this review summarizes the recent significant breakthroughs in key aspects of SCI-related immunomodulation, including innate and adaptive immune response, immune organ changes, and holistic immune status modification. Moreover, the currently existing immune-oriented therapies for SCI will be outlined.

Restoration of spinal cord injury: From endogenous repairing process to cellular therapy

Spinal cord injury (SCI) disrupts neurological pathways and impacts sensory, motor, and autonomic nerve function. There is no effective treatment for SCI currently. Numerous endogenous cells, including astrocytes, macrophages/microglia, and oligodendrocyte, are involved in the histological healing process following SCI. By interfering with cells during the SCI repair process, some advancements in the therapy of SCI have been realized. Nevertheless, the endogenous cell types engaged in SCI repair and the current difficulties these cells confront in the therapy of SCI are poorly defined, and the mechanisms underlying them are little understood. In order to better understand SCI and create new therapeutic strategies and enhance the clinical translation of SCI repair, we have comprehensively listed the endogenous cells involved in SCI repair and summarized the six most common mechanisms involved in SCI repair, including limiting the inflammatory response, protecting the spared spinal cord, enhancing myelination, facilitating neovascularization, producing neurotrophic factors, and differentiating into neural/colloidal cell lines.

Targeting the immune system towards novel therapeutic avenues to fight brain aging and neurodegeneration

The incidence of age-related dementia is growing with increased longevity, yet there are currently no disease-modifying therapies for these devastating disorders. Studies over the last several years have led to an evolving awareness of the role of the immune system in supporting brain maintenance and repair, displaying a diverse repertoire of functions while orchestrating the crosstalk between the periphery and the brain. Here, we provide insights into the current understanding of therapeutic targets that could be adopted to modulate immune cell fate, either systemically or locally, to defeat brain aging and neurodegeneration.

Proteomic characterization of spontaneously regrowing spinal cord following injury in the teleost fish Apteronotus leptorhynchus, a regeneration-competent vertebrate

In adult mammals, spontaneous repair after spinal cord injury (SCI) is severely limited. By contrast, teleost fish successfully regenerate injured axons and produce new neurons from adult neural stem cells after SCI. The molecular mechanisms underlying this high regenerative capacity are largely unknown. The present study addresses this gap by examining the temporal dynamics of proteome changes in response to SCI in the brown ghost knifefish (Apteronotus leptorhynchus). Two-dimensional difference gel electrophoresis (2D DIGE) was combined with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and tandem mass spectrometry (MS/MS) to collect data during early (1 day), mid (10 days), and late (30 days) phases of regeneration following caudal amputation SCI. Forty-two unique proteins with significant differences in abundance between injured and intact control samples were identified. Correlation analysis uncovered six clusters of spots with similar expression patterns over time and strong conditional dependences, typically within functional families or between isoforms. Significantly regulated proteins were associated with axon development and regeneration; proliferation and morphogenesis; neuronal differentiation and re-establishment of neural connections; promotion of neuroprotection, redox homeostasis, and membrane repair; and metabolism or energy supply. Notably, at all three time points examined, significant regulation of proteins involved in inflammatory responses was absent.

Hematopoietic Cells Influence Vascular Development in the Retina

Hematopoietic cells play a crucial role in the adult retina in health and disease. Monocytes, macrophages, microglia and myeloid angiogenic cells (MACs) have all been implicated in retinal pathology. However, the role that hematopoietic cells play in retinal development is understudied. The temporal changes in recruitment of hematopoietic cells into the developing retina and the phenotype of the recruited cells are not well understood. In this study, we used the hematopoietic cell-specific protein Vav1 to track and investigate hematopoietic cells in the developing retina. By flow cytometry and immunohistochemistry, we show that hematopoietic cells are present in the retina as early as P0, and include microglia, monocytes and MACs. Even before the formation of retinal blood vessels, hematopoietic cells localize to the inner retina where they eventually form networks that intimately associate with the developing vasculature. Loss of Vav1 lead to a reduction in the density of medium-sized vessels and an increased inflammatory response in retinal astrocytes. When pups were subjected to oxygen-induced retinopathy, hematopoietic cells maintained a close association with the vasculature and occasionally formed 'frameworks' for the generation of new vessels. Our study provides further evidence for the underappreciated role of hematopoietic cells in retinal vasculogenesis and the formation of a healthy retina.

How the immune system shapes neurodegenerative diseases

Neurodegenerative diseases are a major cause of death and disability worldwide and are influenced by many factors including age, genetics, and injuries. While these diseases are often thought to result from the accumulation and spread of aberrant proteins, recent studies have demonstrated that they can be shaped by the innate and adaptive immune system. Resident myeloid cells typically mount a sustained response to the degenerating CNS, but peripheral leukocytes such as T and B cells can also alter disease trajectories. Here, we review the sometimes-dichotomous roles played by immune cells during neurodegenerative diseases and explore how brain trauma can serve as a disease initiator or accelerant. We also offer insights into how failure to properly resolve a CNS injury might promote the development of a neurodegenerative disease.

Potential role of IGF-1/GLP-1 signaling activation in intracerebral hemorrhage

IGF-1 and GLP-1 receptors are essential in all tissues, facilitating defense by upregulating anabolic processes. They are abundantly distributed throughout the central nervous system, promoting neuronal proliferation, survival, and differentiation. IGF-1/GLP-1 is a growth factor that stimulates neurons' development, reorganization, myelination, and survival. In primary and secondary brain injury, the IGF-1/GLP-1 receptors are impaired, resulting in further neuro complications such as cerebral tissue degradation, neuroinflammation, oxidative stress, and atrophy. Intracerebral hemorrhage (ICH) is a severe condition caused by a stroke for which there is currently no effective treatment. While some pre-clinical studies and medications are being developed as symptomatic therapies in clinical trials, there are specific pharmacological implications for improving post-operative conditions in patients with intensive treatment. Identifying the underlying molecular process and recognizing the worsening situation can assist researchers in developing effective therapeutic solutions to prevent post-hemorrhagic symptoms and the associated neural dysfunctions. As a result, in the current review, we have addressed the manifestations of the disease that are aggravated by the downregulation of IGF-1 and GLP-1 receptors, which can lead to ICH or other neurodegenerative disorders. Our review summarizes that IGF-1/GLP-1 activators may be useful for treating ICH and its related neurodegeneration.

Macrophages as a therapeutic target to promote diabetic wound healing

It is well‏ ‏established that macrophages are key regulators of wound healing, displaying impressive plasticity and an evolving phenotype, from an aggressive pro-inflammatory or "M1" phenotype to a pro-healing or "M2" phenotype, depending on the wound healing stage, to ensure proper healing. Because dysregulated macrophage responses have been linked to impaired healing of diabetic wounds, macrophages are being considered as a therapeutic target for improved wound healing. In this review, we first discuss the role of macrophages in a normal skin wound healing process and discuss the aberrations that occur in macrophages under diabetic conditions. Next we provide an overview of recent macrophage-based therapeutic approaches, including delivery of ex-vivo-activated macrophages and delivery of pharmacological strategies aimed at eliminating or re-educating local skin macrophages. In particular, we focus on strategies to silence key regulator genes to repolarize wound macrophages to the M2 phenotype, and we provide a discussion of their potential future clinical translation.

The therapeutic potential of bone marrow-derived macrophages in neurological diseases

Circulating monocytes are precursors of both tissue macrophages and dendritic cells, and they can infiltrate the central nervous system (CNS) where they transform into bone marrow-derived macrophages (BMDMs). BMDMs play essential roles in various CNS diseases, thus modulating BMDMs might be a way to treat these disorders because there are currently no efficient therapeutic methods available for most of these neurological diseases. Moreover, BMDMs can serve as promising gene delivery vehicles following bone marrow transplantation for otherwise incurable genetic CNS diseases. Understanding the distinct roles that BMDMs play in CNS diseases and their potential as gene delivery vehicles may provide new insights and opportunities for using BMDMs as therapeutic targets or delivery vehicles. This review attempts to comprehensively summarize the neurological diseases that might be treated by modulating BMDMs or by delivering gene therapies via BMDMs after bone marrow transplantation.

Recent Advances in Cell and Functional Biomaterial Treatment for Spinal Cord Injury

Spinal cord injury (SCI) is a devastating central nervous system disease caused by accidental events, resulting in loss of sensory and motor function. Considering the multiple effects of primary and secondary injuries after spinal cord injury, including oxidative stress, tissue apoptosis, inflammatory response, and neuronal autophagy, it is crucial to understand the underlying pathophysiological mechanisms, local microenvironment changes, and neural tissue functional recovery for preparing novel treatment strategies. Treatment based on cell transplantation has become the forefront of spinal cord injury therapy. The transplanted cells provide physical and nutritional support for the damaged tissue. At the same time, the implantation of biomaterials with specific biological functions at the site of the SCI has also been proved to improve the local inhibitory microenvironment and promote axonal regeneration, etc. The combined transplantation of cells and functional biomaterials for SCI treatment can result in greater neuroprotective and regenerative effects by regulating cell differentiation, enhancing cell survival, and providing physical and directional support for axon regeneration and neural circuit remodeling. This article reviews the pathophysiology of the spinal cord, changes in the microenvironment after injury, and the mechanisms and strategies for spinal cord regeneration and repair. The article will focus on summarizing and discussing the latest intervention models based on cell and functional biomaterial transplantation and the latest progress in combinational therapies in SCI repair. Finally, we propose the future prospects and challenges of current treatment regimens for SCI repair, to provide references for scientists and clinicians to seek better SCI repair strategies in the future.

Microglia coordinate cellular interactions during spinal cord repair in mice

Traumatic spinal cord injury (SCI) triggers a neuro-inflammatory response dominated by tissue-resident microglia and monocyte derived macrophages (MDMs). Since activated microglia and MDMs are morphologically identical and express similar phenotypic markers in vivo, identifying injury responses specifically coordinated by microglia has historically been challenging. Here, we pharmacologically depleted microglia and use anatomical, histopathological, tract tracing, bulk and single cell RNA sequencing to reveal the cellular and molecular responses to SCI controlled by microglia. We show that microglia are vital for SCI recovery and coordinate injury responses in CNS-resident glia and infiltrating leukocytes. Depleting microglia exacerbates tissue damage and worsens functional recovery. Conversely, restoring select microglia-dependent signaling axes, identified through sequencing data, in microglia depleted mice prevents secondary damage and promotes recovery. Additional bioinformatics analyses reveal that optimal repair after SCI might be achieved by co-opting key ligand-receptor interactions between microglia, astrocytes and MDMs.

The PI3K/AKT signalling pathway in inflammation, cell death and glial scar formation after traumatic spinal cord injury: Mechanisms and therapeutic opportunities

Objects

Traumatic spinal cord injury (TSCI) causes neurological dysfunction below the injured segment of the spinal cord, which significantly impacts the quality of life in affected patients. The phosphoinositide 3kinase/serine‐threonine kinase (PI3K/AKT) signaling pathway offers a potential therapeutic target for the inhibition of secondary TSCI. This review summarizes updates concerning the role of the PI3K/AKT pathway in TSCI.

Materials and Methods

By searching articles related to the TSCI field and the PI3K/AKT signaling pathway, we summarized the mechanisms of secondary TSCI and the PI3K/AKT signaling pathway; we also discuss current and potential future treatment methods for TSCI based on the PI3K/AKT signaling pathway.

Results

Early apoptosis and autophagy after TSCI protect the body against injury; a prolonged inflammatory response leads to the accumulation of pro‐inflammatory factors and excessive apoptosis, as well as excessive autophagy in the surrounding normal nerve cells, thus aggravating TSCI in the subacute stage of secondary injury. Initial glial scar formation in the subacute phase is a protective mechanism for TSCI, which limits the spread of damage and inflammation. However, mature scar tissue in the chronic phase hinders axon regeneration and prevents the recovery of nerve function. Activation of PI3K/AKT signaling pathway can inhibit the inflammatory response and apoptosis in the subacute phase after secondary TSCI; inhibiting this pathway in the chronic phase can reduce the formation of glial scar.

Conclusion

The PI3K/AKT signaling pathway has an important role in the recovery of spinal cord function after secondary injury. Inducing the activation of PI3K/AKT signaling pathway in the subacute phase of secondary injury and inhibiting this pathway in the chronic phase may be one of the potential strategies for the treatment of TSCI.

The Translational Potential of Microglia and Monocyte-Derived Macrophages in Ischemic Stroke

The immune response to ischemic stroke is an area of study that is at the forefront of stroke research and presents promising new avenues for treatment development. Upon cerebral vessel occlusion, the innate immune system is activated by danger-associated molecular signals from stressed and dying neurons. Microglia, an immune cell population within the central nervous system which phagocytose cell debris and modulate the immune response via cytokine signaling, are the first cell population to become activated. Soon after, monocytes arrive from the peripheral immune system, differentiate into macrophages, and further aid in the immune response. Upon activation, both microglia and monocyte-derived macrophages are capable of polarizing into phenotypes which can either promote or attenuate the inflammatory response. Phenotypes which promote the inflammatory response are hypothesized to increase neuronal damage and impair recovery of neuronal function during the later phases of ischemic stroke. Therefore, modulating neuroimmune cells to adopt an anti-inflammatory response post ischemic stroke is an area of current research interest and potential treatment development. In this review, we outline the biology of microglia and monocyte-derived macrophages, further explain their roles in the acute, subacute, and chronic stages of ischemic stroke, and highlight current treatment development efforts which target these cells in the context of ischemic stroke.

The past, present, and future of traumatic spinal cord injury therapies: a review

This review provides a concise outline of the advances made in the care of patients and to the quality of life after a traumatic spinal cord injury (SCI) over the last century. Despite these improvements reversal of the neurological injury is not yet possible. Instead, current treatment is limited to providing symptomatic relief, avoiding secondary insults and preventing additional sequelae. However, with an ever-advancing technology and deeper understanding of the damaged spinal cord, this appears increasingly conceivable. A brief synopsis of the most prominent challenges facing both clinicians and research scientists in developing functional treatments for a progressively complex injury are presented. Moreover, the multiple mechanisms by which damage propagates many months after the original injury requires a multifaceted approach to ameliorate the human spinal cord. We discuss potential methods to protect the spinal cord from damage, and to manipulate the inherent inhibition of the spinal cord to regeneration and repair. Although acute and chronic SCI share common final pathways resulting in cell death and neurological deficits, the underlying putative mechanisms of chronic SCI and the treatments are not covered in this review.