Sex differences in the inflammatory response to stroke

Neuroinflammation and acute ischemic stroke: impact on translational research and clinical care

Background

Stroke, encompassing both ischemic and hemorrhagic subtypes, is a leading cause of mortality and disability globally and current treatments remain limited. Neuroinflammation plays a crucial role in the pathophysiology of stroke, influencing both acute injury and long-term recovery.

Objective

This review aims to provide a comprehensive overview of neuroinflammation in stroke, detailing the mechanisms, clinical implications, and potential therapeutic strategies.

Methods

A detailed literature review was conducted, focusing on recent advancements in understanding the neuroinflammatory processes in stroke, including the roles of thromboinflammation, blood-brain barrier (BBB) disruption, and the immune response.

Results

The initial ischemic insult triggers an inflammatory cascade involving both innate and adaptive immune responses. BBB disruption allows peripheral immune cells and neurotoxic substances to infiltrate the brain, exacerbating neuronal damage and increasing the risk of infections such as pneumonia and urinary tract infections. Thromboinflammation, characterized by platelet activation and immune cell interactions, further complicates the ischemic environment. Proteomic studies have identified key biomarkers that offer insights into neuroinflammatory mechanisms and potential therapeutic targets. Advances in imaging techniques, such as PET and MRI, enable real-time monitoring of neuroinflammation, facilitating personalized treatment approaches.

Conclusion

Neuroinflammation significantly impacts stroke outcomes, presenting both challenges and opportunities for treatment. Current immunologic therapeutic strategies are limited. Future research should aim to further elucidate the complex immune interactions in stroke, refine imaging biomarkers for clinical use, and develop effective interventions to mitigate neuroinflammation.

Immunity in neuromodulation: probing neural and immune pathways in brain disorders

Immunity finely regulates brain function. It is directly involved in the pathological processes of neurodegenerative diseases such as Parkinson's and Alzheimer's disease, post-stroke conditions, multiple sclerosis, traumatic brain injury, and psychiatric disorders (mood disorders, major depressive disorder (MDD), anxiety disorders, psychosis disorders and schizophrenia, and neurodevelopmental disorders (NDD)). Neuromodulation is currently a leading therapeutic strategy for the treatment of these disorders, but little is yet known about its immune impact on neuronal function and its precise beneficial or harmful consequences. We review relevant clinical and preclinical studies and identify several specific immune modifications. These data not only provide insights into how neuromodulation acts to optimize immune-brain interactions, but also pave the way for a better understanding of these interactions in pathological processes.

3-Monothiopomalidomide, a new immunomodulatory imide drug (IMiD), blunts inflammation and mitigates ischemic stroke in the rat

An overactive neuroinflammatory response is often evident in the elderly and is a significant contributor to brain tissue damage following acute ischemic stroke. Such an inflammatory response is largely mediated by microglial cells and peripheral blood mononuclear cells (PBMCs). Classical anti-inflammatory agents have not proved clinically effective in mitigating the impact of ischemic stroke but have highlighted targets for new drug development, in particular excessive proinflammatory cytokine release. The immunomodulatory imide drug (IMiD) class has shown potential in reducing neuroinflammation and switching microglial phenotypic expression away from a proinflammatory to a regenerative anti-inflammatory one. 3-Monothiopomalidomide (3-MP), a new IMiD, has a brain/plasma concentration ratio of 0.5 to 0.6, an oral bioavailability of 38.5%, and a monophasic disappearance of half-life 3.2 h following oral administration. 3-MP pretreatment mitigates lipopolysaccharide (LPS)-induced inflammation in cellular human PBMCs and, in rat studies, 3-MP pretreatment lowers proinflammatory cytokine levels in the conditioned media and in plasma and the brain, respectively. Administered systemically to rats challenged with middle cerebral artery occlusion (MCAo) and reperfusion, 3-MP post-MCAo treatment reduced infarction volume; improved body asymmetry, a behavioral measure of stroke impact; and lowered inflammation. In summary, 3-MP exerted neuroprotective effects via anti-inflammatory actions against MCAo-induced ischemic injury and represents a therapeutic that warrants further investigation as a treatment for brain damage and related disorders associated with excessive inflammation.

Salidroside attenuates cognitive deficits induced by chronic cerebral hypoperfusion via modulating microglial phenotypic transformation in mice

BACKGROUND

Chronic cerebral hypoperfusion (CCH) is a significant contributor to vascular cognitive impairment (VCI), often linked to cortical and hippocampal damage. This study investigates the therapeutic potential of salidroside (SLDS) in mitigating CCH-induced brain injury by modulating microglial activation and inflammatory responses.

METHODS

We established a CCH model in mice using the 0.16/0.18 mm bilateral common carotid artery stenosis (BCAS) procedure. We assessed cerebral blood flow (CBF) via laser speckle contrast imaging, while neuropathology was evaluated through Nissl staining and immunofluorescence (IF) experiments. Cognitive deficits were measured using the Morris water maze test. Neuronal apoptosis and neuroinflammation were examined through IF, ELISA, and qRT-PCR.

RESULTS

BCAS-induced hypoperfusion resulted in a marked reduction in CBF, increased neuronal apoptosis, and significant cognitive deficits. SLDS treatment effectively countered these effects by shifting microglial polarization from a pro-inflammatory M1 phenotype to an anti-inflammatory M2 phenotype, reducing pro-inflammatory cytokine levels, and enhancing neuronal survival.

CONCLUSION

SLDS demonstrates strong neuroprotective potential against CCH-induced brain injury by reducing inflammation and preventing neuronal apoptosis. These findings highlight the promise of SLDS as a therapeutic agent for chronic cerebrovascular disorders, warranting further investigation into its molecular mechanisms and clinical applicability.

Molecular heterogeneity in human stroke - What can we learn from the peripheral blood transcriptome?

Stroke is a multifaceted disease with genetic and environmental components like diet and lifestyle. The central nervous and immune systems display complex interactions, with the peripheral immune response participating in brain injury and repair mechanisms following stroke. The bidirectional communication between the injured brain and peripheral blood presents an opportunity to investigate the molecular changes in the latter. There is substantial heterogeneity in stroke pathogenesis, pathophysiology, comorbidities, and response to treatment and outcome. This is captured and underscored by heterogeneity in the peripheral blood transcriptome. The current review highlights the role of the human peripheral blood transcriptome architecture for molecular phenotyping of different stroke etiologies and comorbidities, and for identifying underlying molecular correlates with clinically important variables and outcomes. Specific transcriptome features can potentially provide targets for clinical translation and for prioritizing genes and pathways for evaluation in experimental models. We also propose an approach to study the patient-specific transcriptional architecture and uncover the combinatorial heterogeneity in altered pathways in stroke patients that can also guide the search for treatment and prevention targets. Deciphering the molecular heterogeneity of stroke in a tissue that can be easily accessed and monitored, such as peripheral blood, may improve clinical trial success.

Sex differences in age-associated neurological diseases-A roadmap for reliable and high-yield research

Once taken into consideration, sex differences in neurological diseases emerge in abundance: (i) Stroke severity is significantly higher in females than in males, (ii) Alzheimer's disease (AD) pathology is more pronounced in females, and (iii) conspicuous links with hormonal cycles led to female-specific diagnoses, such as catamenial migraines and epilepsy. While these differences receive increasing attention in isolation, they likely link to similar processes in the brain. Hence, this review aims to present an overview of the influences of sex chromosomes, hormones, and aging on male and female brains across health and disease, with a particular focus on AD and stroke. The focus here on advancements across several fields holds promise to fuel future research and to lead to an enriched understanding of the brain and more effective personalized neurologic care for all.

Glial 'omics in ischemia: Acute stroke and chronic cerebral small vessel disease

Vascular injury and pathologies underlie common diseases including ischemic stroke and cerebral small vessel disease (CSVD). Prior work has identified a key role for glial cells, including microglia, in the multifaceted and temporally evolving neuroimmune response to both stroke and CSVD. Transcriptional profiling has led to important advances including identification of distinct gene expression signatures in ischemia-exposed, flow cytometrically sorted microglia and more recently single cell RNA sequencing-identified microglial subpopulations or clusters. There is a reassuring degree of overlap in the results from these two distinct methodologies with both identifying a proliferative and a separate type I interferon responsive microglial element. Similar patterns were later seen using multimodal and spatial transcriptomal profiling in ischemia-exposed microglia and astrocytes. Methodological advances including enrichment of specific neuroanatomic/functional regions (such as the neurovascular unit) prior to single cell RNA sequencing has led to identification of novel cellular subtypes and generation of new credible hypotheses as to cellular function based on the enhanced cell sub-type specific gene expression patterns. A ribosomal tagging strategy focusing on the cellular translatome analyses carried out in the acute phases post stroke has revealed distinct inflammation-regulating roles for microglia and astrocytes in this setting. Early spatial transcriptomics experiments using cerebral ischemia models have identified regionally distinct microglial cell clusters in ischemic core versus penumbra. There is great potential for combination of these methods for multi-omics approaches to further elucidate glial responses in the context of both acute ischemic stroke and chronic CSVD.

Female mice exhibit resistance to disease progression despite early pathology in a transgenic mouse model inoculated with alpha-synuclein fibrils

Despite known sex differences in human synucleinopathies such as Parkinson's disease, the impact of sex on alpha-synuclein pathology in mouse models has been largely overlooked. To address this need, we examine sex differences in whole brain signatures of neurodegeneration due to aSyn toxicity in the M83 mouse model using longitudinal magnetic resonance imaging (MRI; T1-weighted; 100 μm3 isotropic voxel; -7, 30, 90 and 120 days post-injection [dpi]; n ≥ 8 mice/group/sex/time point). To initiate aSyn spreading, M83 mice are inoculated with recombinant human aSyn preformed fibrils (Hu-PFF) or phosphate buffered saline in the right striatum. We observe more aggressive neurodegenerative profiles over time for male Hu-PFF-injected mice when examining voxel-wise trajectories. However, at 90 dpi, we observe widespread patterns of neurodegeneration in the female Hu-PFF-injected mice. These differences are not accompanied by any differences in motor symptom onset between the sexes. However, male Hu-PFF-injected mice reached their humane endpoint sooner. These findings suggest that post-motor symptom onset, despite accelerated disease trajectories for male Hu-PFF-injected mice, neurodegeneration may appear sooner in the female Hu-PFF-injected mice (prior to motor symptomatology). These findings suggest that sex-specific synucleinopathy phenotypes urgently need to be considered to improve our understanding of neuroprotective and neurodegenerative mechanisms.

Characterisation of GPR17-expressing oligodendrocyte precursors in human ischaemic lesions and correlation with reactive glial responses

White matter damage and subsequent demyelination significantly contribute to long-term functional impairment after ischaemic stroke. Identifying novel pharmacological targets to restore myelin integrity by promoting the maturation of oligodendrocyte precursor cells (OPCs) into new myelinating oligodendrocytes may open new perspectives for ischaemic stroke treatment. In this respect, previous studies highlighted the role of the G protein-coupled membrane receptor 17 (GPR17) as a key regulator of OPC differentiation in experimental models of brain injury, including ischaemic stroke. To determine the translational value of GPR17 as a possible target in the context of human disease, we exploited immunohistochemistry to characterise the distribution of GPR17-expressing cells in brain tissue samples from ischaemic stroke cases and correlated it with the reactive state of neighbouring glial cells. The results showed that GPR17 specifically decorates a subpopulation of differentiation-committed OPCs, labelled by the peculiar marker breast carcinoma-amplified sequence 1 (BCAS1), that accumulates in the peri-infarct region in the later stages after the ischaemic event. Interestingly, the response of GPR17-expressing cells appears to be paralleled by the switch of reactive microglia/macrophages from a phagocytic to a dystrophic phenotype and by astrocytic scar formation. A negative correlation was found between GPR17-expressing OPCs and reactive microglia/macrophages and astrocytes surrounding chronic ischaemic lesions in female subjects, while the same relationship was less pronounced in males. These results were reinforced by bioinformatic analysis of a publicly available transcriptomic dataset, which implicated a possible role of inflammation and defective neuron-to-OPC communication in remyelination failure after ischaemic damage. Hence, these data strengthen the relevance of GPR17-based remyelinating therapies for the treatment of ischaemic stroke. © 2024 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Impact of peripheral immune cells in experimental neonatal hypoxia-ischemia: A systematic review and meta-analysis

Infiltration of peripheral immune cells into the brain following neonatal hypoxia-ischemia (HI) contributes to increased neuroinflammation and brain injury. However, the specific roles of different immune cell types in neonatal brain injury remain poorly understood. Although existing evidence suggests a potential role for sexual dimorphism in HI outcomes, this aspect has been insufficiently investigated. In this systematic review and meta-analysis, we examined the brain infiltration of peripheral immune cells in rodents of both sexes following neonatal HI. A total of 25 studies were included. Our analysis revealed significant increases in the infiltration of various subtypes of leukocytes after HI, along with increased brain injury, cell death, and neuroinflammation, and reduced neuronal survival. Notably, males exhibited a greater degree of immune cell infiltration and more pronounced neuroinflammation compared to females. These findings suggest that infiltrating leukocytes contribute significantly to the pathophysiology of neonatal HI, with sexually dimorphic responses further influencing the outcomes. It is crucial that future research focuses on elucidating the specific roles of immune cell subtypes to better understand the mechanisms underlying brain damage after HI and identify novel therapeutic targets. Moreover, the observed sex differences highlight the need to consider sex as a key factor when developing strategies for the treatment of neonatal HI.

CAMs in command: aging brain macrophages fine-tune stroke immune responses

Central nervous system-associated macrophages (CAMs) are a unique subset of immune cells located at the interface between the blood and the brain parenchyma. In a recent study in mice, Levard and colleagues found that CAMs regulate immune cell trafficking, endothelial activation, and antigen presentation following stroke exclusively in aged animals, underscoring the importance of using translationally relevant models for studying age-related diseases.

Trends in medically serious suicide attempts before and after COVID-19: a four-year retrospective analysis (2018-2022)

BACKGROUND

Suicide has become a first-order public health concern after the negative impact of COVID-19 on the general population's mental health. Several studies have analyzed the trends in suicide attempts (SA) before and after the onset of the pandemic, but few studies focus on the impact of the pandemic on medically serious suicide attempts (MSSA).

METHODS

Participants were 385 hospitalized individuals ≥ 16 years old who made MSSA identified retrospectively through a review of e-medical records between 2018 and 2022 ("pre-COVID-19" and "COVID" periods). The two groups were compared on sociodemographic and clinical variables using Chi-square or Exact Fisher's tests for categorical variables and a Mann-Whitney test for continuous variables. To study the variation in MSSA over time, MSSA were aggregated monthly. Joinpoint regression analyses were used to assess time trends.

RESULTS

A sample of 161 MSSA patients, 80 women and 81 men, were selected from 385 admissions after a suicide attempt (SA) in the four years (n = 160 pre-COVID period vs. n = 225 COVID period) (OR = 1.41; CI 95% = 1.0003-1.7223, p < 0.001). Sixty-eight patients with MSSA were admitted during the first period, and 93 during the COVID period (OR = 1.4 ; CI 95% = 1-1.9 ; p < 0.05). MSSA patients were more likely to be admitted to an intensive care unit during the COVID period than during the pre-COVID period (OR = 3.5; CI 95% = 1.7-6.9; p < 0.001).

CONCLUSIONS

This study highlights the need for research on suicide risk during and after crisis periods, such as the COVID-19 pandemic. It provides valuable knowledge on the incidence of SA needing hospitalization, MSSA, and highly severe MSSA for four years before and after the pandemic onset.

Early elevations in arterial pressure: a contributor to rapid depressive symptom emergence in female Zucker rats with metabolic disease?

One of the growing challenges to public health and clinical outcomes is the emergence of cognitive impairments, particularly depressive symptom severity, because of chronic elevations in metabolic disease and cerebrovascular disease risk. To more clearly delineate these relationships and to assess the potential for sexual dimorphism, we used lean (LZR) and obese Zucker rats (OZR) of increasing age to determine relationships between internal carotid artery (ICA) hemodynamics, cerebral vasculopathies, and the emergence of depressive symptoms. Male OZR exhibited progressive elevations in perfusion pressure within the ICA, which were paralleled by endothelial dysfunction, increased cerebral arterial myogenic activation, and reduced cerebral cortex microvessel density. In contrast, female OZR exhibited a greater degree of ICA hypertension than male OZR but maintained normal endothelial function, myogenic activation, and microvessel density to an older age range than did males. Although both male and female OZR exhibited significant and progressive elevations in depressive symptom severity, these were significantly worse in females. Finally, plasma cortisol concentration was elevated higher and at a younger age in female OZR as compared with males, and this difference was maintained to final animal usage at ∼17 wk of age. These results suggest that an increased severity of blood pressure waves may penetrate the cerebral circulation more deeply in female OZR than in males, which may predispose the females to a more severe emergence of depressive symptoms with chronic metabolic disease, whereas males may be more predisposed to more direct cerebral vasculopathies (e.g., stroke, transient ischemic attack).NEW & NOTEWORTHY We provide novel insight that the superior maintenance of cerebrovascular endothelial function in female versus male rats with chronic metabolic disease buffers myogenic activation of cerebral resistance arteries/arterioles despite worsening hypertension. As hypertension development is earlier and more severe in females, potentially due to an elevated stress response, the blunted myogenic activation allows greater arterial pressure wave penetrance into the cerebral microcirculation and is associated with accelerated emergence/severity of depressive symptoms in obese female rats.

Acute liver damage generates age independent microglia morphology changes in mice

Non-alcoholic fatty liver disease (NAFLD) has emerged as a silent global epidemic, frequently contributing to systemic inflammation. As the primary immune cells of the central nervous system (CNS), microglia undergo morphological changes that serve as critical indicators of CNS health. In this study, we aimed to quantify alterations in microglial morphology within the cortex of young and aged mice with liver damage. Our results demonstrated that hepatic dysfunction leads to a significant increase in total branch length in both young (285.79±68.23 μm) and aged animals (268.67±69.06 μm), compared to their respective controls (164.07±33.05 μm and 140.96±27.18 μm) (p<0.0001). Additionally, aged animals with liver damage exhibited a mean branch length of 5.84±0.66 μm, higher than 2.63±0.19 μm observed in those without liver injury. The number of primary branches in aged mice with liver damage decreased from 6.6±1.2 branches to 3.1±1.5 (p<0.0001). In addition, we have shown a decrease in the number of secondary branches in aged animals with liver damage. This suggests that microglia not only respond to CNS-specific injuries but also to chronic systemic pathologies like NAFLD. These findings highlight the importance of better understanding the liver-brain axis in order to better understand the neuroimmune consequences of systemic diseases.

Advancing Post-Stroke Depression Research: Insights from Murine Models and Behavioral Analyses

Post-stroke depression (PSD) represents a significant neuropsychiatric complication that affects between 39% and 52% of stroke survivors, leading to impaired recovery, decreased quality of life, and increased mortality. This comprehensive review synthesizes our current knowledge of PSD, encompassing its epidemiology, risk factors, underlying neurochemical mechanisms, and the existing tools for preclinical investigation, including animal models and behavioral analyses. Despite the high prevalence and severe impact of PSD, challenges persist in accurately modeling its complex symptomatology in preclinical settings, underscoring the need for robust and valid animal models to better understand and treat PSD. This review also highlights the multidimensional nature of PSD, where both biological and psychosocial factors interplay to influence its onset and course. Further, we examine the efficacy and limitations of the current animal models in mimicking the human PSD condition, along with behavioral tests used to evaluate depressive-like behaviors in rodents. This review also sets a new precedent by integrating the latest findings across multidisciplinary studies, thereby offering a unique and comprehensive perspective of existing knowledge. Finally, the development of more sophisticated models that closely replicate the clinical features of PSD is crucial in order to advance translational research and facilitate the discovery of future effective therapies.

Intermittent fasting induced cerebral ischemic tolerance altered gut microbiome and increased levels of short-chain fatty acids to a beneficial phenotype

Preconditioning-induced cerebral ischemic tolerance is known to be a beneficial adaptation to protect the brain in an unavoidable event of stroke. We currently demonstrate that a short bout (6 weeks) of intermittent fasting (IF; 15 h fast/day) induces similar ischemic tolerance to that of a longer bout (12 weeks) in adult C57BL/6 male mice subjected to transient middle cerebral artery occlusion (MCAO). In addition, the 6 weeks IF regimen induced ischemic tolerance irrespective of age (3 months or 24 months) and sex. Mice subjected to transient MCAO following IF showed improved motor function recovery (rotarod and beam walk tests) between days 1 and 14 of reperfusion and smaller infarcts (T2-MRI) on day 1 of reperfusion compared with age/sex matched ad libitum (AL) controls. Diet influences the gut microbiome composition and stroke is known to promote gut bacterial dysbiosis. We presently show that IF promotes a beneficial phenotype of gut microbiome following transient MCAO compared with AL cohort. Furthermore, post-stroke levels of short-chain fatty acids (SCFAs), which are known to be neuroprotective, are higher in the fecal samples of the IF cohort compared with the AL cohort. Thus, our studies indicate the efficacy of IF in protecting the brain after stroke, irrespective of age and sex, probably by altering gut microbiome and SCFA production.

MMP-3 Knockout Induces Global Transcriptional Changes and Reduces Cerebral Infarction in Both Male and Female Models of Ischemic Stroke

Ischemic stroke followed by reperfusion (IR) leads to extensive cerebrovascular injury characterized by neuroinflammation and brain cell death. Inhibition of matrix metalloproteinase-3 (MMP-3) emerges as a promising therapeutic approach to mitigate IR-induced stroke injury. We employed middle cerebral artery occlusion with subsequent reperfusion (MCAO/R) to model ischemic stroke in adult mice. Specifically, we investigated the impact of MMP-3 knockout (KO) on stroke pathophysiology using RNA sequencing (RNA-seq) of stroke brains harvested 48 h post-MCAO. MMP-3 KO significantly reduced brain infarct size following stroke. Notably, RNA-seq analysis showed that MMP-3 KO altered expression of 333 genes (252 downregulated) in male stroke brains and 3768 genes (889 downregulated) in female stroke brains. Functional pathway analysis revealed that inflammation, integrin cell surface signaling, endothelial- and epithelial-mesenchymal transition (EndMT/EMT), and apoptosis gene signatures were decreased in MMP-3 KO stroke brains. Intriguingly, MMP-3 KO downregulated gene signatures more profoundly in females than in males, as indicated by greater negative enrichment scores. Our study underscores MMP-3 inhibition as a promising therapeutic strategy, impacting multiple cellular pathways following stroke.

Comprehensive immune modulation mechanisms of Angong Niuhuang Wan in ischemic stroke: Insights from mass cytometry analysis

BACKGROUND

Angong Niuhuang Wan (AGNHW, ), is a classical medicinal formula in Traditional Chinese Medicine (TCM) that has been appreciated for its neuroprotective properties in ischemic cerebral injuries, yet its intricate mechanisms remain only partially elucidated.

AIMS

This study leverages advanced Mass cytometry (CyTOF) to analyze AGNHW's multifaceted immunomodulation effects in-depth, emphasizing previously underexplored areas.

RESULTS

AGNHW mitigated monocyte-derived macrophages (MoDM) infiltration in the brain, distinguishing its effects on those from microglia. While the vehicle group exhibited elevated inflammatory markers like CD4, CD8a, and CD44 in ischemic brains, the AGNHW-treated group attenuated their expressions, indicating AGNHW's potential to temper the post-ischemic inflammatory response. Systemically, AGNHW modulated fundamental immune cell dynamics, notably augmenting CD8+ T cells, B cells, monocytes, and neutrophil counts in the peripheral blood under post-stroke conditions. Intracellularly, AGNHW exhibited its targeted modulation of the signaling pathways, revealing a remarked inhibition of key markers like IκBα, indicating potential suppression of inflammatory responses in ischemic brain injuries.

CONCLUSION

This study offers a comprehensive portrait of AGNHW's immunomodulation effects on ischemic stroke, illuminating its dual sites of action-both cerebral and systemic-and its nuanced modulation of cellular and molecular dynamics.

Muscle mass as a modifier of stress response in acute ischemic stroke patients

Stroke triggers a systemic inflammatory response over the ensuing days after the cerebral insult. The age and comorbidities of the stroke population make them a vulnerable population for low muscle mass and sarcopenia, the latter being another clinical condition that is closely associated with inflammation, as shown by increased levels of pro-inflammatory biomarkers, including neutrophil-to-lymphocyte ratio (NLR). In this study, we evaluated the relationship between post-stroke NLR changes and muscle mass in a prospective cohort of acute ischemic stroke patients (n = 102) enrolled in the Muscle Assessment in Stroke Study Turkey (MASS-TR). Admission lumbar computed tomography images were used to determine the cross-sectional muscle area of skeletal muscles at L3 vertebra level and calculate the skeletal muscle index (SMI). The median (IQR) SMI was 44.7 (39.1-52.5) cm2/m2, and the NLR at admission and follow-up were 4.2 (3.0-10.5) and 9.4 (5.7-16.2), respectively. While there was no relationship between SMI and admission NLR, a significant inverse correlation was observed between SMI and follow-up NLR (r =  - 0.26; P = 0.007). Lower SMI remained significantly associated (P = 0.036) with higher follow-up NLR levels in multivariate analysis. Our findings highlight the importance of muscle mass as a novel factor related to the level of post-stroke stress response.

Long-Term Alterations in Motor Skills, Neurogenesis and Astrocyte Numbers following Transient Cerebral Ischemia in Mice

Background and Objectives. Neurogenesis is an integral process in post-stroke recovery, involving the recruitment of proliferating neuroblasts from neurogenic niches of the mammal brain. However, the role of neurogenesis in the long-term restoration following ischemic stroke is fragmented. Post-stroke motor dysfunction includes challenges in the proper, coordinated use of hands and is present in roughly two-thirds of human patients. In this study, we investigated chronic behavioral and biochemical alterations after transient cerebral ischemia in adult male mice. Materials and Methods: Twelve-week-old C57BL/6N male mice were used, and fMCAo lasting 60 min was induced. At multiple timepoints after fMCAo induction, a single pellet reaching task was performed. Six months after the procedure, we immunohistochemically determined the number of proliferating neuroblasts (BrdU and DCX-positive) and the number of differentiated astrocytes (GFAP-positive) in both brain hemispheres. Results: The reaching ability of fMCAo mice was impaired from one month to six months after the induction of ischemia. Neuroblast proliferation was increased in the ipsilateral SVZ, whereas GFAP+ cell count was elevated in the hippocampal DG of both hemispheres of the fMCAo group mice. Conclusions: Our current report demonstrates the long-term effects of transient cerebral ischemia on mice functional parameters and neurogenesis progression. Our data demonstrate that transient cerebral ischemia promotes a long-lasting regenerative response in the ipsilateral brain hemisphere, specifically in the neurogenic SVZ and DG regions.

Acute brain injury and nanomedicine: sex as a biological variable

Sex as a biological variable has been recognized for decades to be a critical aspect of the drug development process, as differences in drug pharmacology and toxicity in female versus male subjects can drive the success or failure of new therapeutics. These concepts in development of traditional drug systems have only recently begun to be applied for advancing nanomedicine systems that are designed for drug delivery or imaging in the central nervous system (CNS). This review provides a comprehensive overview of the current state of two fields of research - nanomedicine and acute brain injury-centering on sex as a biological variable. We highlight areas of each field that provide foundational understanding of sex as a biological variable in nanomedicine, brain development, immune response, and pathophysiology of traumatic brain injury and stroke. We describe current knowledge on female versus male physiology as well as a growing number of empirical reports that directly address sex as a biological variable in these contexts. In sum, the data make clear two key observations. First, the manner in which sex affects nanomedicine distribution, toxicity, or efficacy is important, complex, and depends on the specific nanoparticle system under considerations; second, although field knowledge is accumulating to enable us to understand sex as a biological variable in the fields of nanomedicine and acute brain injury, there are critical gaps in knowledge that will need to be addressed. We anticipate that understanding sex as a biological variable in the development of nanomedicine systems to treat acute CNS injury will be an important determinant of their success.

Engineered extracellular vesicles for ischemic stroke: a systematic review and meta-analysis of preclinical studies

BACKGROUND

This systematic review and meta-analysis aimed to evaluate the efficacy of engineered extracellular vesicles (EEVs) in the treatment of ischemic stroke (IS) in preclinical studies and to compare them with natural extracellular vesicles (EVs). The systematic review provides an up-to-date overview of the current state of the literature on the use of EEVs for IS and informs future research in this area.

METHODS

We searched PubMed, EMBASE, Web of Science, Cochrane Library, and Scopus databases for peer-reviewed preclinical studies on the therapeutic effect of EEVs on IS.Databases ranged from the inception to August 1, 2023. The outcome measures included infarct volumes, neurological scores, behavioral scores, apoptosis rates, numbers of neurons, and levels of IL-1β, IL-6, and TNF-α. The CAMARADES checklist was used to assess the quality and bias risks of the studies. All statistical analyses were performed using RevMan 5.4 software.

RESULTS

A total of 28 studies involving 1760 animals met the inclusion criteria. The results of the meta-analysis showed that compared to natural EVs, EEVs reduced infarct volume (percentage: SMD = -2.33, 95% CI: -2.92, -1.73; size: SMD = -2.36, 95% CI: -4.09, -0.63), improved neurological scores (mNSS: SMD = -1.78, 95% CI: -2.39, -1.17; Zea Longa: SMD = -2.75, 95% CI: -3.79, -1.71), promoted behavioral recovery (rotarod test: SMD = 2.50, 95% CI: 1.81, 3.18; grid-walking test: SMD = -3.45, 95% CI: -5.15, -1.75; adhesive removal test: SMD = -2.60, 95% CI: -4.27, -0.93; morris water maze test: SMD = -3.91, 95% CI: -7.03, -0.79), and reduced the release of proinflammatory factors (IL-1β: SMD = -2.02, 95% CI: -2.77, -1.27; IL-6: SMD = -3.01, 95% CI: -4.47, -1.55; TNF-α: SMD = -2.72, 95% CI: -4.30, -1.13), increasing the number of neurons (apoptosis rate: SMD = -2.24, 95% CI: -3.32, -1.16; the number of neurons: SMD = 3.70, 95% CI: 2.44, 4.96). The funnel plots for the two main outcome measures were asymmetric, indicating publication bias. The median score on the CAMARADES checklist was 7 points (IQR: 6-9).

CONCLUSIONS

This meta-analysis shows that EEVs are superior to natural EVs for the treatment of IS. However, research in this field is still at an early stage, and more research is needed to fully understand the potential therapeutic mechanism of EEVs and their potential use in the treatment of IS.

PROSPERO REGISTRATION NUMBER

CRD42022368744.

Neuroinflammation in Acute Ischemic and Hemorrhagic Stroke

PURPOSE OF REVIEW

This review aims to provide an overview of neuroinflammation in ischemic and hemorrhagic stroke, including recent findings on the mechanisms and cellular players involved in the inflammatory response to brain injury.

RECENT FINDINGS

Neuroinflammation is a crucial process following acute ischemic stroke (AIS) and hemorrhagic stroke (HS). In AIS, neuroinflammation is initiated within minutes of the ischemia onset and continues for several days. In HS, neuroinflammation is initiated by blood byproducts in the subarachnoid space and/or brain parenchyma. In both cases, neuroinflammation is characterized by the activation of resident immune cells, such as microglia and astrocytes, and infiltration of peripheral immune cells, leading to the release of pro-inflammatory cytokines, chemokines, and reactive oxygen species. These inflammatory mediators contribute to blood-brain barrier disruption, neuronal damage, and cerebral edema, promoting neuronal apoptosis and impairing neuroplasticity, ultimately exacerbating the neurologic deficit. However, neuroinflammation can also have beneficial effects by clearing cellular debris and promoting tissue repair. The role of neuroinflammation in AIS and ICH is complex and multifaceted, and further research is necessary to develop effective therapies that target this process. Intracerebral hemorrhage (ICH) will be the HS subtype addressed in this review. Neuroinflammation is a significant contributor to brain tissue damage following AIS and HS. Understanding the mechanisms and cellular players involved in neuroinflammation is essential for developing effective therapies to reduce secondary injury and improve stroke outcomes. Recent findings have provided new insights into the pathophysiology of neuroinflammation, highlighting the potential for targeting specific cytokines, chemokines, and glial cells as therapeutic strategies.

Sex and interferon gamma signaling regulate microglia migration in the adult mouse cortex in vivo

Although microglia possess the unique ability to migrate, whether mobility is evident in all microglia, is sex dependent, and what molecular mechanisms drive this, is not well understood in the adult brain. Using longitudinal in vivo two-photon imaging of sparsely labeled microglia, we find a relatively small population of microglia (~5%) are mobile under normal conditions. Following injury (microbleed), the fraction of mobile microglia increased in a sex-dependent manner, with male microglia migrating significantly greater distances toward the microbleed relative to their female counterparts. To understand the signaling pathways involved, we interrogated the role of interferon gamma (IFNγ). Our data show that in male mice, stimulating microglia with IFNγ promotes migration whereas inhibiting IFNγ receptor 1 signaling inhibits them. By contrast, female microglia were generally unaffected by these manipulations. These findings highlight the diversity of microglia migratory responses to injury, its dependence on sex and the signaling mechanisms that modulate this behavior.

Potential regulatory effects of stem cell exosomes on inflammatory response in ischemic stroke treatment

The high incidence and disability rates of stroke pose a heavy burden on society. Inflammation is a significant pathological reaction that occurs after an ischemic stroke. Currently, therapeutic methods, except for intravenous thrombolysis and vascular thrombectomy, have limited time windows. Mesenchymal stem cells (MSCs) can migrate, differentiate, and inhibit inflammatory immune responses. Exosomes (Exos), which are secretory vesicles, have the characteristics of the cells from which they are derived, making them attractive targets for research in recent years. MSC-derived exosomes can attenuate the inflammatory response caused by cerebral stroke by modulating damage-associated molecular patterns. In this review, research on the inflammatory response mechanisms associated with Exos therapy after an ischemic injury is discussed to provide a new approach to clinical treatment.

Neuroinflammation and Brain Disease

Starting from the perspective of an immune-privileged site, our knowledge of the inflammatory processes within the central nervous system has increased rapidly over the last 30 years, leading to a rather puzzling picture today. Of particular interest is the emergence of disease- and injury-specific inflammatory responses within the brain, which may form the basis for future therapeutic approaches. To advance this important topic, we invite authors to contribute research and clinical papers to the Collection "Neuroinflammation and Brain Disease".

Acupuncture treatment for post-stroke depression: Intestinal microbiota and its role

Stroke-induced depression is a common complication and an important risk factor for disability. Besides psychiatric symptoms, depressed patients may also exhibit a variety of gastrointestinal symptoms, and even take gastrointestinal symptoms as the primary reason for medical treatment. It is well documented that stress may disrupt the balance of the gut microbiome in patients suffering from post-stroke depression (PSD), and that disruption of the gut microbiome is closely related to the severity of the condition in depressed patients. Therefore, maintaining the balance of intestinal microbiota can be the focus of research on the mechanism of acupuncture in the treatment of PSD. Furthermore, stroke can be effectively treated with acupuncture at all stages and it may act as a special microecological regulator by regulating intestinal microbiota as well. In this article, we reviewed the studies on changing intestinal microbiota after acupuncture treatment and examined the existing problems and development prospects of acupuncture, microbiome, and poststroke depression, in order to provide new ideas for future acupuncture research.