Rejuvenating fecal microbiota transplant enhances peripheral nerve repair in aged mice by modulating endoneurial inflammation

Peripheral nerve injury (PNI) resulting from trauma or neuropathies can cause significant disability, and its prognosis deteriorates with age. Emerging evidence suggests that gut dysbiosis and reduced fecal short-chain fatty acids (SCFAs) contribute to an age-related systemic hyperinflammation (inflammaging), which hinders nerve recovery after injury. This study thus aimed to evaluate the pro-regenerative effects of a rejuvenating fecal microbiota transplant (FMT) in a preclinical PNI model using aged mice. Aged C57BL/6 mice underwent bilateral crush injuries to their sciatic nerves. Subsequently, they either received FMT from young donors at three and four days after the injury or retained their aged gut microbiota. We analyzed gut microbiome composition and SCFA concentrations in fecal samples. The integrity of the ileac mucosal barrier was assessed by immunofluorescence staining of Claudin-1. Flow cytometry was utilized to examine immune cells and cytokine production in the ileum, spleen, and sciatic nerve. Various assessments, including behavioural tests, electrophysiological studies, and morphometrical analyses, were conducted to evaluate peripheral nerve function and repair following injury. Rejuvenating FMT reversed age-related gut dysbiosis by increasing Actinobacteria, especially Bifidobacteriales genera. This intervention also led to an elevation of gut SCFA levels and mitigated age-related ileac mucosal leakiness in aged recipients. Additionally, it augmented the number of T-helper 2 (Th2) and regulatory T (Treg) cells in the ileum and spleen, with the majority being positive for anti-inflammatory interleukin-10 (IL-10). In sciatic nerves, rejuvenating FMT resulted in increased M2 macrophage counts and a higher IL-10 production by IL-10+TNF-α- M2 macrophage subsets. Ultimately, restoring a youthful gut microbiome in aged mice led to improved nerve repair and enhanced functional recovery after PNI. Considering that FMT is already a clinically available technique, exploring novel translational strategies targeting the gut microbiome to enhance nerve repair in the elderly seems promising and warrants further evaluation.

Neutrophils and Neutrophil Extracellular Traps Cause Vascular Occlusion and Delayed Cerebral Ischemia After Subarachnoid Hemorrhage in Mice

BACKGROUND

After subarachnoid hemorrhage (SAH), neutrophils are deleterious and contribute to poor outcomes. Neutrophils can produce neutrophil extracellular traps (NETs) after ischemic stroke. Our hypothesis was that, after SAH, neutrophils contribute to delayed cerebral ischemia (DCI) and worse outcomes via cerebrovascular occlusion by NETs.

METHODS

SAH was induced via endovascular perforation, and SAH mice were given either a neutrophil-depleting antibody, a PAD4 (peptidylarginine deiminase 4) inhibitor (to prevent NETosis), DNAse-I (to degrade NETs), or a vehicle control. Mice underwent daily neurological assessment until day 7 and then euthanized for quantification of intravascular brain NETs (iNETs). Subsets of mice were used to quantify neutrophil infiltration, NETosis potential, iNETs, cerebral perfusion, and infarction. In addition, NET markers were assessed in the blood of aneurysmal SAH patients.

RESULTS

In mice, SAH led to brain neutrophil infiltration within 24 hours, induced a pro-NETosis phenotype selectively in skull neutrophils, and caused a significant increase in iNETs by day 1, which persisted until at least day 7. Neutrophil depletion significantly reduced iNETs, improving cerebral perfusion, leading to less neurological deficits and less incidence of DCI (16% versus 51.9%). Similarly, PAD4 inhibition reduced iNETs, improved neurological outcome, and reduced incidence of DCI (5% versus 30%), whereas degrading NETs marginally improved outcomes. Patients with aneurysmal SAH who developed DCI had elevated markers of NETs compared with non-DCI patients.

CONCLUSIONS

After SAH, skull-derived neutrophils are primed for NETosis, and there are persistent brain iNETs, which correlated with delayed deficits. The findings from this study suggest that, after SAH, neutrophils and NETosis are therapeutic targets, which can prevent vascular occlusion by NETs in the brain, thereby lessening the risk of DCI. Finally, NET markers may be biomarkers, which can predict which patients with aneurysmal SAH are at risk for developing DCI.

Sex Differences in Perihematomal Edema Volume and Outcome After Intracerebral Hemorrhage

BACKGROUND

Although larger hematoma volume is associated with worse outcome after intracerebral hemorrhage (ICH), the association between perihematomal edema (PHE) volume and outcome remains uncertain, as does the impact of sex on PHE and outcome. Here we aimed to determine whether larger PHE volume is associated with worse outcome and whether PHE volume trajectories differ by sex.

METHODS

We conducted a post hoc analysis of the Factor VIIa for Acute Hemorrhagic Stroke Treatment (FAST) trial, which randomized patients with ICH to receive recombinant activated factor VIIa or placebo. Computerized planimetry calculated PHE and ICH volumes on serial computed tomography (CT) scans (at baseline [within 3 h of onset], at 24 h, and at 72 h). Generalized estimating equations examined interactions between sex, CT time points, and FAST treatment arm on PHE and ICH volumes. Mixed and multivariable logistic models examined associations between sex, PHE, and outcomes.

RESULTS

A total of 781 patients with supratentorial ICH (mean age 65 years) were included. Compared to women (n = 296), men (n = 485) had similar median ICH (14.9 vs. 13.6 mL, p = 0.053) and PHE volumes (11.1 vs. 10.5 mL, p = 0.56) at baseline but larger ICH and PHE volumes at 24 h (19.0 vs. 14.0 mL, p < 0.001; 22.2 vs. 15.7 mL, p < 0.001) and 72 h (16.0 vs. 11.8 mL, p < 0.001; 28.7 vs. 19.9 mL, p < 0.001). Men had higher absolute early PHE expansion (p < 0.001) and more hematoma expansion (growth ≥ 33% or 6 mL at 24 h, 33% vs. 22%, p < 0.001). An interaction between sex and CT time points on PHE volume (p < 0.001), but not on ICH volume, confirmed a steeper PHE trajectory in men. PHE expansion (per 5 mL, odds radio 1.19, 95% confidence interval 1.10-1.28), but not sex, was associated with poor outcome.

CONCLUSIONS

Early PHE expansion and trajectory in men were significantly higher. PHE expansion was associated with poor outcomes independent of sex. Mechanisms leading to sex differences in PHE trajectories merit further investigation.

Mitochondria-containing extracellular vesicles from mouse vs . human brain endothelial cells for ischemic stroke therapy

Ischemic stroke-induced mitochondrial dysfunction in the blood-brain barrier-forming brain endothelial cells ( BECs ) results in long-term neurological dysfunction post-stroke. We previously reported that intravenous administration of human BEC ( hBEC )-derived mitochondria-containing extracellular vesicles ( EVs ) showed a potential efficacy signal in a mouse middle cerebral artery occlusion ( MCAo ) model of stroke. We hypothesized that EVs harvested from donor species homologous to the recipient species ( e.g., mouse) may improve therapeutic efficacy, and therefore, use of mouse BEC ( mBEC )-derived EVs may improve post-stroke outcomes in MCAo mice. We investigated if EVs derived from the same species as the recipient cell (mBEC-EVs and recipient mBECs or hBECs-EVs and recipient hBECs) show a greater EV mitochondria delivery efficiency than cross-species EVs and recipient cells (mBEC-EVs and recipient hBECs or vice versa ). Our results showed that mBEC-EVs outperformed hBEC-EVs in transferring EV mitochondria to the recipient ischemic mBECs, and improved mBEC mitochondrial function via increasing oxygen consumption rate. mBEC-EVs significantly reduced brain infarct volume and improved behavioral recovery compared to vehicle-injected MCAo mice. Our data suggests that mBEC-EVs show superior therapeutic efficacy in a mouse MCAo stroke model compared to hBEC-EVs-supporting the continued use of mBEC-EVs to optimize the therapeutic potential of mitochondria-containing EVs in preclinical studies.

The contribution of age-related changes in the gut-brain axis to neurological disorders

Trillions of microbes live symbiotically in the host, specifically in mucosal tissues such as the gut. Recent advances in metagenomics and metabolomics have revealed that the gut microbiota plays a critical role in the regulation of host immunity and metabolism, communicating through bidirectional interactions in the microbiota-gut-brain axis (MGBA). The gut microbiota regulates both gut and systemic immunity and contributes to the neurodevelopment and behaviors of the host. With aging, the composition of the microbiota changes, and emerging studies have linked these shifts in microbial populations to age-related neurological diseases (NDs). Preclinical studies have demonstrated that gut microbiota-targeted therapies can improve behavioral outcomes in the host by modulating microbial, metabolomic, and immunological profiles. In this review, we discuss the pathways of brain-to-gut or gut-to-brain signaling and summarize the role of gut microbiota and microbial metabolites across the lifespan and in disease. We highlight recent studies investigating 1) microbial changes with aging; 2) how aging of the maternal microbiome can affect offspring health; and 3) the contribution of the microbiome to both chronic age-related diseases (e.g., Parkinson's disease, Alzheimer's disease and cerebral amyloidosis), and acute brain injury, including ischemic stroke and traumatic brain injury.

Estradiol mediates colonic epithelial protection in aged mice after stroke and is associated with shifts in the gut microbiome

The gut is a major source of bacteria and antigens that contribute to neuroinflammation after brain injury. Colonic epithelial cells (ECs) are responsible for secreting major cellular components of the innate defense system, including antimicrobial proteins (AMP) and mucins. These cells serve as a critical regulator of gut barrier function and maintain host-microbe homeostasis. In this study, we determined post-stroke host defense responses at the colonic epithelial surface in mice. We then tested if the enhancement of these epithelial protective mechanisms is beneficial in young and aged mice after stroke. AMPs were significantly increased in the colonic ECs of young males, but not in young females after experimental stroke. In contrast, mucin-related genes were enhanced in young females and contributed to mucus formation that maintains the distance between the host and gut bacteria. Bacterial community profiling was done using universal amplification of 16S rRNA gene sequences. The sex-specific colonic epithelial defense responses after stroke in young females were reversed with ovariectomy and led to a shift from a predominately mucin response to the enhanced AMP expression seen in males after stroke. Estradiol (E2) replacement prior to stroke in aged females increased mucin gene expression in the colonic ECs. Interestingly, we found that E2 treatment reduced stroke-associated neuronal hyperactivity in the insular cortex, a brain region that interacts with visceral organs such as the gut, in parallel to an increase in the composition of Lactobacillus and Bifidobacterium in the gut microbiota. This is the first study demonstrating sex differences in host defense mechanisms in the gut after brain injury.

Automated Large Vessel Occlusion Detection Software and Thrombectomy Treatment Times: A Cluster Randomized Clinical Trial

Importance

The benefit of endovascular stroke therapy (EVT) in large vessel occlusion (LVO) ischemic stroke is highly time dependent. Process improvements to accelerate in-hospital workflows are critical.

Objective

To determine whether automated computed tomography (CT) angiogram interpretation coupled with secure group messaging can improve in-hospital EVT workflows.

Design, Setting, and Participants

This cluster randomized stepped-wedge clinical trial took place from January 1, 2021, through February 27, 2022, at 4 comprehensive stroke centers (CSCs) in the greater Houston, Texas, area. All 443 participants with LVO stroke who presented through the emergency department were treated with EVT at the 4 CSCs. Exclusion criteria included patients presenting as transfers from an outside hospital (n = 158), in-hospital stroke (n = 39), and patients treated with EVT through randomization in a large core clinical trial (n = 3).

Intervention

Artificial intelligence (AI)-enabled automated LVO detection from CT angiogram coupled with secure messaging was activated at the 4 CSCs in a random-stepped fashion. Once activated, clinicians and radiologists received real-time alerts to their mobile phones notifying them of possible LVO within minutes of CT imaging completion.

Main Outcomes and Measures

Primary outcome was the effect of AI-enabled LVO detection on door-to-groin (DTG) time and was measured using a mixed-effects linear regression model, which included a random effect for cluster (CSC) and a fixed effect for exposure status (pre-AI vs post-AI). Secondary outcomes included time from hospital arrival to intravenous tissue plasminogen activator (IV tPA) bolus in eligible patients, time from initiation of CT scan to start of EVT, and hospital length of stay. In exploratory analysis, the study team evaluated the impact of AI implementation on 90-day modified Rankin Scale disability outcomes.

Results

Among 243 patients who met inclusion criteria, 140 were treated during the unexposed period and 103 during the exposed period. Median age for the complete cohort was 70 (IQR, 58-79) years and 122 were female (50%). Median National Institutes of Health Stroke Scale score at presentation was 17 (IQR, 11-22) and the median DTG preexposure was 100 (IQR, 81-116) minutes. In mixed-effects linear regression, implementation of the AI algorithm was associated with a reduction in DTG time by 11.2 minutes (95% CI, -18.22 to -4.2). Time from CT scan initiation to EVT start fell by 9.8 minutes (95% CI, -16.9 to -2.6). There were no differences in IV tPA treatment times nor hospital length of stay. In multivariable logistic regression adjusted for age, National Institutes of Health Stroke scale score, and the Alberta Stroke Program Early CT Score, there was no difference in likelihood of functional independence (modified Rankin Scale score, 0-2; odds ratio, 1.3; 95% CI, 0.42-4.0).

Conclusions and Relevance

Automated LVO detection coupled with secure mobile phone application-based communication improved in-hospital acute ischemic stroke workflows. Software implementation was associated with clinically meaningful reductions in EVT treatment times.

Trial Registration

ClinicalTrials.gov Identifier: NCT05838456.

Iron overload induces cerebral endothelial senescence in aged mice and in primary culture in a sex-dependent manner

Iron imbalance in the brain negatively affects brain function. With aging, iron levels increase in the brain and contribute to brain damage and neurological disorders. Changes in the cerebral vasculature with aging may enhance iron entry into the brain parenchyma, leading to iron overload and its deleterious consequences. Endothelial senescence has emerged as an important contributor to age-related changes in the cerebral vasculature. Evidence indicates that iron overload may induce senescence in cultured cell lines. Importantly, cells derived from female human and mice generally show enhanced senescence-associated phenotype, compared with males. Thus, we hypothesize that cerebral endothelial cells (CEC) derived from aged female mice are more susceptible to iron-induced senescence, compared with CEC from aged males. We found that aged female mice, but not males, showed cognitive deficits when chronically treated with ferric citrate (FC), and their brains and the brain vasculature showed senescence-associated phenotype. We also found that primary culture of CEC derived from aged female mice, but not male-derived CEC, exhibited senescence-associated phenotype when treated with FC. We identified that the transmembrane receptor Robo4 was downregulated in the brain vasculature and in cultured primary CEC derived from aged female mice, compared with those from male mice. We discovered that Robo4 downregulation contributed to enhanced vulnerability to FC-induced senescence. Thus, our study identifies Robo4 downregulation as a driver of senescence induced by iron overload in primary culture of CEC and a potential risk factor of brain vasculature impairment and brain dysfunction.

Stabilizing histamine release in gut mast cells mitigates peripheral and central inflammation after stroke

Stroke is the most common cause of long-term disability and places a high economic burden on the global healthcare system. Functional outcomes from stroke are largely determined by the extent of ischemic injury, however, there is growing recognition that systemic inflammatory responses also contribute to outcomes. Mast cells (MCs) rapidly respond to injury and release histamine (HA), a pro-inflammatory neurotransmitter that enhances inflammation. The gut serves as a major reservoir of HA. We hypothesized that cromolyn, a mast cell stabilizer that prevents the release of inflammatory mediators, would decrease peripheral and central inflammation, reduce MC trafficking to the brain, and improve stroke outcomes. We used the transient middle cerebral artery occlusion (MCAO) model of ischemic stroke in aged (18 mo) male mice to investigate the role of MC in neuroinflammation post-stroke. After MCAO we treated mice with 25 mg/kg body weight of cromolyn (MC stabilizer) by oral gavage. Cromolyn was administered at 3 h, 10 h, 24 h and every 24 h for 3 days post-stroke. Three control groups were used. One group underwent a sham surgery and was treated with cromolyn, one received sham surgery with PBS vehicle and the third underwent MCAO with PBS vehicle. Mice were euthanized at 24 h and 3 days post-stroke. Cromolyn administration significantly reduced MC numbers in the brain at both 24 h and 3 days post-stroke. Infarct volume was not significantly different between groups, however improved functional outcomes were seen at 3 days post-stroke in mice that received cromolyn. Treatment with cromolyn reduced plasma histamine and IL-6 levels in both the 24-h and 3-day cohorts. Gut MCs numbers were significantly reduced after cromolyn treatment at 24 h and 3 days after stroke. To determine if MC trafficking from the gut to the brain occurred after injury, GFP+MCs were adoptively transferred to c-kit-/- MC knock-out animals prior to MCAO. 24 h after stroke, elevated MC recruitment was seen in the ischemic brain. Preventing MC histamine release by cromolyn improved gut barrier integrity and an improvement in stroke-induced dysbiosis was seen with treatment. Our results show that preventing MC histamine release possesses prevents post-stroke neuroinflammation and improves neurological and functional outcomes.

Pirh2-dependent DNA damage in neurons induced by the G-quadruplex ligand pyridostatin

Noncanonical base pairing between four guanines (G) within single-stranded G-rich sequences leads to formation of а G-quartet. Self-stacking of G-quartets results in a columnar four-stranded DNA structure known as the G-quadruplex (G4 or G4-DNA). In cancer cells, G4-DNA regulates multiple DNA-dependent processes, including transcription, replication, and telomere function. How G4s function in neurons is poorly understood. Here, we performed a genome-wide gene expression analysis (RNA-Seq) to identify genes modulated by a G4-DNA ligand, pyridostatin (PDS), in primary cultured neurons. PDS promotes stabilization of G4 structures, thus allowing us to define genes directly or indirectly responsive to G4 regulation. We found that 901 genes were differentially expressed in neurons treated with PDS out of a total of 18,745 genes with measured expression. Of these, 505 genes were downregulated and 396 genes were upregulated and included gene networks regulating p53 signaling, the immune response, learning and memory, and cellular senescence. Within the p53 network, the E3 ubiquitin ligase Pirh2 (Rchy1), a modulator of DNA damage responses, was upregulated by PDS. Ectopically overexpressing Pirh2 promoted the formation of DNA double-strand breaks, suggesting a new DNA damage mechanism in neurons that is regulated by G4 stabilization. Pirh2 downregulated DDX21, an RNA helicase that unfolds G4-RNA and R-loops. Finally, we demonstrated that Pirh2 increased G4-DNA levels in the neuronal nucleolus. Our data reveal the genes that are responsive to PDS treatment and suggest similar transcriptional regulation by endogenous G4-DNA ligands. They also connect G4-dependent regulation of transcription and DNA damage mechanisms in neuronal cells.

X, but not Y, Chromosomal Complement Contributes to Stroke Sensitivity in Aged Animals

Post-menopausal women become vulnerable to stroke and have poorer outcomes and higher mortality than age-matched men, and previous studies suggested that sex chromosomes play a vital role in mediating stroke sensitivity in the aged. It is unknown if this is due to effects of the X or Y chromosome. The present study used the XY* mouse model (with four genotypes: XX and XO gonadal females and XY and XXY gonadal males) to compare the effect of the X vs. Y chromosome compliment in stroke. Aged (18-20 months) and gonadectomized young (8-12 weeks) mice were subjected to a 60-min middle cerebral artery occlusion. Infarct volume and behavioral deficits were quantified 3 days after stroke. Microglial activation and infiltration of peripheral leukocytes in the aged ischemic brain were assessed by flow cytometry. Plasma inflammatory cytokine levels by ELISA, and brain expression of two X chromosome-linked genes, KDM6A and KDM5C by immunochemistry, were also examined. Both aged and young XX and XXY mice had worse stroke outcomes compared to XO and XY mice, respectively; however, the difference between XX vs. XXY and XO vs. XY aged mice was minimal. Mice with two copies of the X chromosome showed more robust microglial activation, higher brain-infiltrating leukocytes, elevated plasma cytokine levels, and enhanced co-localization of KDM6A and KDM5C with Iba1+ cells after stroke than mice with one X chromosome. The number of X chromosomes mediates stroke sensitivity in aged mice, which might be processed through the X chromosome-linked genes and the inflammatory responses.

Sex differences in perihematomal edema volume and outcome after intracerebral hemorrhage

Objective

To determine whether in patients with intracerebral hemorrhage (ICH) perihematomal edema (PHE) volume trajectories differ by sex.

Methods

We conducted a post-hoc analysis of the Factor-VII-for-Acute-Hemorrhagic-Stroke-Treatment (FAST) trial that randomized patients with ICH to receive recombinant activated Factor VIIa or placebo. Computerized planimetry calculated PHE and ICH volumes on serial CT scans (at baseline [within 3 hours of onset], at 24, and at 72 hours). Generalized estimating equations examined interactions between sex, CT-timepoints, and FAST treatment-arm on PHE and ICH volumes. Mixed and multivariate logistic models examined associations between sex, PHE, and outcomes.

Results

781 with supratentorial ICH (mean age 65 years) were included. Compared to women (n=296), men (n=485) had similar median ICH (14.9 versus 13.6 ml, p=0.053), and PHE volumes (11.1 versus 10.5 ml, p=0.56) at baseline but larger ICH and PHE at 24 hours (19.0 versus 14.0, p<0.001; 22.2 versus 15.7, p<0.001) and 72 hours (16.0 versus 11.8, p<0.001; 28.7 versus 19.9, p<0.001). Men had higher absolute PHE expansion (p<0.001), and more hematoma expansion (growth ≥33% or 6 mL at 24 hours, 33% versus 22%, p<0.001). An interaction between sex and CT-timepoints on PHE (p<0.001) but not on ICH volumes confirmed a steeper PHE trajectory in men. PHE expansion (per 5mL, odds radio, 1.19, 95%-confidence interval 1.10-1.28), but not sex, was associated with poor outcome.

Conclusions

PHE expansion and trajectory in men were significantly higher. PHE expansion was associated with poor outcomes independent of sex. Mechanisms leading to sex differences in PHE trajectories merit further investigation.

What is already known on this topic

Prior research has reported sex differences in intracerebral hemorrhage (ICH) characteristics and some studies suggest worse outcome after ICH in women. However, we do not have a good understanding whether there are sex differences in perihematomal edema (PHE) volume trajectories, or whether sex, independent of confounders, is associated with poor after ICH.

What this study adds

In this post-hoc analysis of 781 patients with supratentorial ICH from the Factor-VII-for-Acute-Hemorrhagic-Stroke-Treatment (FAST) trial in which patients underwent brain CT imaging time-locked to symptom onset (within 3 hours of symptom onset, at 24 hours, and at 72 hours), men compared to women had similar ICH and PHE volumes at baseline, but larger ICH expansion and PHE expansion on follow up imaging. The PHE but not the ICH volume trajectory across scans was significantly higher in men than in women. While PHE expansion was associated with poor outcome at 90 days, outcome between the sexes was similar at 90 days, and sex was not associated with outcome.

How this study might affect research practice or policy

The finding of heightened early PHE and ICH expansion in men may inform study design, patient recruitment strategies, and pre-specification of subgroup analyses in future interventional trials. The findings of this study also suggest that focusing on sex-specific factors may allow novel mechanistic insight into PHE, a major cause of secondary injury and poor outcome after ICH.

A multi-laboratory preclinical trial in rodents to assess treatment candidates for acute ischemic stroke

Human diseases may be modeled in animals to allow preclinical assessment of putative new clinical interventions. Recent, highly publicized failures of large clinical trials called into question the rigor, design, and value of preclinical assessment. We established the Stroke Preclinical Assessment Network (SPAN) to design and implement a randomized, controlled, blinded, multi-laboratory trial for the rigorous assessment of candidate stroke treatments combined with intravascular thrombectomy. Efficacy and futility boundaries in a multi-arm multi-stage statistical design aimed to exclude from further study highly effective or futile interventions after each of four sequential stages. Six independent research laboratories performed a standard focal cerebral ischemic insult in five animal models that included equal numbers of males and females: young mice, young rats, aging mice, mice with diet-induced obesity, and spontaneously hypertensive rats. The laboratories adhered to a common protocol and efficiently enrolled 2615 animals with full data completion and comprehensive animal tracking. SPAN successfully implemented treatment masking, randomization, prerandomization inclusion and exclusion criteria, and blinded assessment of outcomes. The SPAN design and infrastructure provide an effective approach that could be used in similar preclinical, multi-laboratory studies in other disease areas and should help improve reproducibility in translational science.

A narrative review on treatment strategies for neonatal hypoxic ischemic encephalopathy

Background and Objective

Hypoxic-ischemic encephalopathy (HIE) is a leading cause of death and disability worldwide. Therapeutic hypothermia (TH) represents a significant achievement in the translation of scientific research to clinical application, but it is currently the only neuroprotective treatment for HIE. This review aims to revisit the use of TH for HIE and its longitudinal impact on patient outcomes to readers new to the field of HIE. We discuss how emerging therapies address the broader pathophysiology of injury progression in the neonatal brain days to years after HIE.

Methods

We included full articles and book chapters published in English on PubMed with references to "hypoxic ischemic encephalopathy", "birth asphyxia", "therapeutic hypothermia", or "neonatal encephalopathy". We limited our review to outcomes on term infants and to new therapeutics that are in the second phase of clinical trials.

Key Content and Findings

Despite the use of TH for HIE, mortality remains high. Analysis of longitudinal studies reveals a high incidence of ongoing disability even with the implementation of TH. New therapeutics addressing the secondary phase and the less understood tertiary phase of brain injury are in clinical trials as adjunctive treatments to TH to support additional neurological repair and regeneration.

Conclusions

TH successfully improves outcomes after HIE, and it continues to be optimized. Larger studies are needed to understand its use in mild cases of HIE and if certain factors, such as sex, affect long term outcomes. TH primarily acts in the initial phases of injury, while new pharmaceutical therapies target additional injury pathways into the tertiary phases of injury. This may allow for more effective approaches to treatment and improvement of long-term functional outcomes after HIE.

Women With Large Vessel Occlusion Acute Ischemic Stroke Are Less Likely to Be Routed to Comprehensive Stroke Centers

Background Prehospital routing of patients with large vessel occlusion (LVO) acute ischemic stroke (AIS) to centers capable of performing endovascular therapy may improve clinical outcomes. Here, we explore whether distance to comprehensive stroke centers (CSCs), stroke severity, and sex are associated with direct-to-CSC prehospital routing in patients with LVO AIS. Methods and Results In this cross-sectional study, we identified consecutive patients with LVO AIS from a prospectively collected multihospital registry throughout the greater Houston area from January 2019 to June 2020. Primary outcome was prehospital routing to CSC and was compared between men and women using modified Poisson regression including age, sex, race or ethnicity, first in-hospital National Institutes of Health Stroke Scale score, travel time, and distances to the closest primary stroke center and CSC. Among 503 patients with LVO AIS, 413 (82%) were routed to CSCs, and women comprised 46% of the study participants. Women with LVO AIS compared with men were older (73 versus 65, P<0.01) and presented with greater National Institutes of Health Stroke Scale score (14 versus 12, P=0.01). In modified Poisson regression, women were 9% less likely to be routed to CSCs compared with men (adjusted relative risk [aRR], 0.91 [0.84-0.99], P=0.024) and distance to nearest CSC ≤10 miles was associated with 38% increased chance of routing to CSC (aRR, 1.38 [1.26-1.52], P<0.001). Conclusions Despite presenting with more significant stroke syndromes and living within comparable distance to CSCs, women with LVO AIS were less likely to be routed to CSCs compared with men. Further study of the mechanisms behind this disparity is needed.

Lifelong cerebrovascular disease burden among CADASIL patients: analysis from a global health research network

Introduction

Data reporting on patients with Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL) within the United States population is limited. We sought to evaluate the overt cerebrovascular disease burden among patients with CADASIL.

Methods

Harmonized electronic medical records were extracted from the TriNetX global health research network. CADASIL patients were identified using diagnostic codes and those with/without history of documented stroke sub-types (ischemic stroke [IS], intracerebral hemorrhage [ICH], subarachnoid hemorrhage [SAH] and transient ischemic attack [TIA]) were compared. Adjusted odds ratios (OR) and 95% confidence intervals (CI) of stroke incidence and mortality associated with sex were computed.

Results

Between September 2018 and April 2020, 914 CADASIL patients were identified (median [IQR] age: 60 [50-69], 61.3% females); of whom 596 (65.2%) had documented cerebrovascular events (i.e., CADASIL-Stroke patients). Among CADASIL-Stroke patients, 89.4% experienced an IS, co-existing with TIAs in 27.7% and hemorrhagic strokes in 6.2%; initial stroke events occurred ≤65 years of age in 71% of patients. CADASIL-Stroke patients (vs. CADASIL-non-Stroke) had higher cardiovascular and neurological (migraines, cognitive impairment, epilepsy/seizures, mood disorders) burden. In age- and comorbidity-adjusted models, males had higher associated risk of stroke onset (OR: 1.37, CI: 1.01-1.86). Mortality risk was higher for males (OR: 2.72, CI: 1.53-4.84).

Discussion

Early screening and targeted treatment strategies are warranted to help CADASIL patients with symptom management and risk mitigation.

Stroke-Induced Respiratory Dysfunction Is Associated With Cognitive Decline

BACKGROUND

Respiratory dysfunction is a common complication of stroke, with an incidence of over 60%. Despite the high prevalence of stroke-induced respiratory dysfunction, how disordered breathing influences recovery and cognitive outcomes after ischemic stroke is unknown. We hypothesized that stroke induces chronic respiratory dysfunction, breathing instability, and apnea in mice, which would contribute to higher mortality and greater poststroke cognitive deficits.

METHODS

Mice were subjected to a 60-minute transient middle cerebral artery occlusion or permanent distal middle cerebral artery occlusion. Whole body plethysmography was performed on C57BL/6 young (2-3 months) and aged (20 months) male and female mice. Animals were exposed to a variety of gas conditions to assess the contribution of peripheral and central chemoreceptors. A battery of cognitive tests was performed to examine behavioral function.

RESULTS

Middle cerebral artery occlusion led to disordered breathing characterized by hypoventilation and apneas. Cognitive decline correlated with the severity of disordered breathing. Distal permanent middle cerebral artery occlusion, which produces a smaller cortical infarct, also produced breathing disorders and cognitive impairment but only in aged mice.

CONCLUSIONS

Our data suggest that poststroke apnea is associated with cognitive decline and highlights the influence of aging on breathing disorders after stroke. Therefore, the treatment of respiratory instability may be a viable approach to improving cognitive outcomes after stroke.

Sex differences in the inflammatory response to stroke

Ischemic stroke is a leading cause of morbidity and mortality and disproportionally affects women, in part due to their higher longevity. Older women have poorer outcomes after stroke with high rates of cognitive deficits, depression, and reduced quality of life. Post-stroke inflammatory responses are also sexually dimorphic and drive differences in infarct size and recovery. Factors that influence sex-specific immune responses can be both intrinsic and extrinsic. Differences in gonadal hormone exposure, sex chromosome compliment, and environmental/social factors can drive changes in transcriptional and metabolic profiles. In addition, how these variables interact, changes across the lifespan. After the onset of ischemic injury, necrosis and apoptosis occur, which activate microglia and other glial cells within the central nervous system, promoting the release of cytokines and chemokines and neuroinflammation. Cells involved in innate and adaptive immune responses also have dual functions after stroke as they can enhance inflammation acutely, but also contribute to suppression of the inflammatory cascade and later repair. In this review, we provide an overview of the current literature on sex-specific inflammatory responses to ischemic stroke. Understanding these differences is critical to identifying therapeutic options for both men and women.

Contemporary Antiplatelet and Anticoagulant Therapies for Secondary Stroke Prevention: A Narrative Review of Current Literature and Guidelines

PURPOSE OF REVIEW

Stroke is a leading cause of death and disability worldwide. The annual incidence of new or recurrent stroke is approximately 795,000 cases per year in the United States, of which 87% are ischemic in nature. In addition to the management of modifiable high-risk factors to reduce the risk of recurrent stroke, antithrombotic agents (antiplatelets and anticoagulants) play an important role in secondary stroke prevention. This review will discuss the published literature on the use of antiplatelets and anticoagulants in secondary prevention of acute ischemic stroke and transient ischemic attack (TIA), including their pharmacology, efficacy, and adverse effects. We will also highlight the role of dual antiplatelet therapy (DAPT) in secondary stroke prevention, along with supporting literature.

RECENT FINDINGS

Single antiplatelet therapy (SAPT) with aspirin or clopidogrel reduces the risk of recurrent ischemic stroke in patients with non-cardioembolic ischemic stroke or TIA. However, as shown in recent trials, short-term DAPT with aspirin and clopidogrel or ticagrelor for 21-30 days is more effective than SAPT in patients with minor acute non-cardioembolic stroke or high-risk TIA. Although short-term DAPT is highly effective in preventing recurrent stroke, a more prolonged course can increase bleeding risks without additional benefit. DAPT for 90 days, followed by aspirin monotherapy for patients with large vessel intracranial atherosclerotic disease, is suitable for secondary stroke prevention. However, patients need to be monitored for both minor (e.g., bruising) and major (e.g., intracranial) bleeding complications. Conversely, oral warfarin and newer direct oral anticoagulant (DOACs) such as dabigatran, rivaroxaban, apixaban, and edoxaban are the agents of choice for secondary stroke prevention in patients with non-valvular cardioembolic strokes. DOACs may be preferred over warfarin due to decreased bleeding risks, including ICH, lack of need for international normalized ratio monitoring, no dietary restrictions, and limited drug-drug interactions. The choice between different antiplatelets and anticoagulants for prevention of ischemic stroke depends on the underlying stroke mechanism, cytochrome P450 2C19 polymorphisms, bleeding risk profile, compliance, drug tolerance, and drug resistance. Physicians must carefully weigh each patient's relative benefits and bleeding risks before initiating an antiplatelet/anticoagulant treatment regimen. Further studies are warranted to study the optimal duration of DAPT in symptomatic intracranial atherosclerosis since the benefit is most pronounced in the short term while the bleeding risk remains high during the extended duration of therapy.

Unfractionated heparin versus enoxaparin for venous thromboembolism prophylaxis in intensive care units: a propensity score adjusted analysis

Venous thromboembolism (VTE) is a common complication in hospitalized patients. Pharmacologic prophylaxis is used in order to reduce the risk of VTE events. The main purpose of this study is to compare the prevalence of deep vein thrombosis (DVT) and pulmonary embolism (PE) in patients admitted to the intensive care unit (ICU) who received unfractionated heparin (UFH) versus enoxaparin as VTE prophylaxis. Mortality was evaluated as a secondary outcome. This was a Propensity Score Adjusted Analysis. Patients admitted to neurology, surgical, or medical ICUs and screened with venous doppler ultrasonography or computed tomography angiography for detection of VTE were included in the analysis. We identified 2228 patients in the cohort, 1836 (82.4%) patients received UFH and 392 (17.6%) patients received enoxaparin. Propensity score matching yielded a well-balanced cohort of 950 (74% UFH, 26% enoxaparin) patients. After matching, there was no difference in prevalence of DVT (RR 1.05; 95% CI 0.67-1.64, p = 0.85) and PE (RR 0.76; 95% CI, 0.44-1.30, p = 0.31). No significant differences in location and severity of DVT and PE between the two groups were detected. Hospital and intensive care unit stay was similar between the two groups. Unfractionated heparin was associated with a higher rate of mortality, (HR 2.04; 95% CI, 1.13-3.70; p = 0.019). The use of UFH as VTE prophylaxis in ICU patients was associated with a similar prevalence of DVT and PE compared with enoxaparin, and the site and degree of occlusion were similar. However, a higher mortality rate was seen in the UFH group.

The Tardigrade damage suppressor protein Dsup promotes DNA damage in neurons

Tardigrades are microscopic invertebrates, which are capable of withstanding extreme environmental conditions, including high levels of radiation. A Tardigrade protein, Dsup (Damage Suppressor), protects the Tardigrade's DNA during harsh environmental stress and X-rays. When expressed in cancer cells, Dsup protects DNA from single and double-strand breaks (DSBs) induced by radiation, increases survival of irradiated cells, and protects DNA from reactive oxygen species. These unusual properties of Dsup suggested that understanding how the protein functions may help in the design of small molecules that could protect humans during radiotherapy or space travel. Here, we investigated if Dsup is protective in cortical neurons cultured from rat embryos. We discovered that, in cortical neurons, the codon-optimized Dsup localizes to the nucleus and, surprisingly, promotes neurotoxicity leading to neurodegeneration. Unexpectedly, we found that Dsup expression results in the formation of DNA DSBs in cultured neurons. With electron microscopy, we discovered that Dsup promotes chromatin condensation. Unlike Dsup's protective properties in cancerous cells, in neurons, Dsup promotes neurotoxicity, induces DNA damage, and rearranges chromatin. Taken together, neurons are sensitive to Dsup, and Dsup is a doubtful surrogate for DNA protection in neuronal cells.

Peripheral eosinophil trends and clinical outcomes after non-traumatic subarachnoid hemorrhage

Background/objective

Uncontrolled systemic inflammation after non-traumatic subarachnoid hemorrhage (SAH) is associated with worse outcomes. Changes in the peripheral eosinophil count have been linked to worse clinical outcomes after ischemic stroke, intracerebral hemorrhage, and traumatic brain injury. We aimed to investigate the association of eosinophil counts with clinical outcomes after SAH.

Methods

This retrospective observational study included patients with SAH admitted from January 2009 to July 2016. Variables included demographics, modified Fisher scale (mFS), Hunt-Hess Scale (HHS), global cerebral edema (GCE), and the presence of any infection. Peripheral eosinophil counts were examined as part of routine clinical care on admission and daily for 10 days after aneurysmal rupture. Outcome measures included dichotomized discharge mortality, modified Ranked Scale (mRS) score, delayed cerebral ischemia (DCI), vasospasm, and need for ventriculoperitoneal shunt (VPS). Statistical tests included the chi-square test, Student's t-test, and multivariable logistic regression (MLR) model.

Results

A total of 451 patients were included. The median age was 54 (IQR 45, 63) years, and 295 (65.4%) were female patients. On admission, 95 patients (21.1%) had a high HHS (>4), and 54 (12.0%) had GCE. A total of 110 (24.4%) patients had angiographic vasospasm, 88 (19.5%) developed DCI, 126 (27.9%) had an infection during hospitalization, and 56 (12.4%) required VPS. Eosinophil counts increased and peaked on days 8-10. Higher eosinophil counts on days 3-5 and day 8 were seen in patients with GCE (p < 0.05). Higher eosinophil counts on days 7-9 (p < 0.05) occurred in patients with poor discharge functional outcomes. In multivariable logistic regression models, higher day 8 eosinophil count was independently associated with worse discharge mRS (OR 6.72 [95% CI 1.27, 40.4], p = 0.03).

Conclusion

This study demonstrated that a delayed increase in eosinophils after SAH occurs and may contribute to functional outcomes. The mechanism of this effect and the relationship with SAH pathophysiology merit further investigation.

Middle Cerebral Artery Occlusion in Aged Animal Model

Stroke is a devastating brain injury resulting in high mortality and substantial loss of function, affecting >15 million people worldwide annually; the majority of which are over 65 years old (Feigin et al., Lancet 383:245-254, 2014; Feigin et al., Lancet Neurol 2:43-53, 2003; Benjamin et al., Circulation 135:e146-e603, 2017; Writing Group et al., Circulation 133:447-454, 2016; Roy-O'Reilly, McCullough, Endocrinology 159:3120-3131, 2018). Aging is a significant risk factor for stroke, and older patients have higher mortality and poorer functional recovery after stroke compared with younger patients (Arboix et al., J Am Geriatr Soc 48:36-41, 2000; Rojas et al., Eur J Neurol 14:895-899, 2007). Despite the importance of aging in the pathophysiology of stroke, the vast majority of preclinical studies have only used young animals. Understanding the mechanisms underlying stroke-induced brain damage and post-stroke functional recovery in aged animals is an urgent need. This step is essential to the development of therapeutics for treating stroke patients, most of whom are elderly. To understand the pathophysiology of ischemic injury induced by middle cerebral artery occlusion (MCAO), one of the most common type of stroke seen clinically (Writing Group et al., Circulation 133:e38-360, 2016), it is imperative to include older animals in preclinical testing. The purpose of this chapter is to provide insight on successfully reproducing MCAO injury in translationally relevant aged animals.

Abstract WMP92: Presentation Blood Glucose Is Associated With CTP Core Volume Overestimations In Acute Ischemic Stroke Patients With Large Vessel Occlusion

Background: CT Perfusion (CTP) predictions of infarct core play a large role in determination of treatment eligibility in large vessel occlusion (LVO) acute ischemic stroke (AIS). Prior studies have demonstrated that glucose can affect cerebral blood flow (CBF). Here we evaluate the influence of acute and chronic glucose levels on CTP over-estimation (OE) of infract core, leading to potential undertreatment.

Methods: From our prospectively collected multicenter observational cohort, we identified AIS LVO patients evaluated with non-contrast CT, CTA and concurrent CTP who underwent endovascular therapy with substantial reperfusion (TICI2b-3), and also had MRI 48-72 hours post-treatment. OE was defined as a difference of at least 20 mL between CTP-RAPID (IschemaView, Stanford CA) predicted infarct core and DWI final infarct volume (FIV). The primary outcome was the association of glucose and HgbA1c on OE and was measured using multivariable logistic regression to control for other patient level factors.

Results: Among 256 patients meeting inclusion criteria, median age was 67 [IQR 57-77] and 51.6% were female. Median CTP-predicted core was 6 mL [IQR 0-30], median DWI FIV was 14 mL [IQR 6-43] with median difference of 12 mL [IQR 5-35]. 28 patients (10.9%) had OE, with median difference in infarct size of 40 mL [24-56]. In univariable analysis, early time window (<6 hours from last known well), absence of diabetes, normal HgbA1c, and normal admission glucose were associated with OE. In multivariate analysis, early time window (aOR 2.87, p=0.025) and lower/normal glucose (aOR 3.01, p=0.02) were independent predictors of OE. Among 65 patients with higher HgbA1c and blood glucose levels (>6.5, >126), 27 patients (42%) had CTP core under-estimation (UE).

Conclusions: Acute and chronic changes in glycemic state affect automated CTP interpretations. These findings may be related to previously described effects on cerebral blood flow.

Abstract TMP113: Kynurenine-3-monooxygenase Inhibition Confers Neuroprotection After Ischemic Stroke In Aged Mice

Background: The kynurenine pathway (KP) is the major route of tryptophan catabolism in mammals. KP branches into two major pathways - one (dependent on the kynurenine aminotransferases) implicated in neuroprotection, the other (dependent on the enzyme kynurenine-3-monooxygenase (KMO) in neurotoxicity. Under physiological conditions, the neuroprotective branch is more active, but under inflammatory conditions, such as seen in stroke, metabolism is shifted through the KP via KMO to produce toxic metabolites, including quinolinic acid. Recent studies have demonstrated that stroke leads to the activation of the KP. Here we tested whether inhibiting KMO activity after stroke could prevent and/or minimize the neuronal death and improve outcomes.

Methods: WT C57Bl6 aged male mice were subjected to a 60-minute reversible middle cerebral artery occlusion (MCAO). Tissues collected from a sub-cohort of these mice was used for metabolomics. Other sub-cohort of mice was used for pharmacological studies. For this, mice received either an inhibitor of KMO (Ro 61-8048, 40mg/kg/day i.p) or vehicle immediately after stroke, and infarct was evaluated at day 3 post-stroke. Neurological deficit scores and open field analysis was performed to assess recovery. A separate cohort of aged WT and KMO knockout (KMO-/-) mice was also subjected to MCAO and assessed for infarct and recovery at 3 days after stroke to further evaluate the involvement of KMO on outcome.

Results: Stroke caused significant reduction in the aged brain kynurenic acid/quinolinic acid (KYNA/QUIN) ratio, suggesting activation of the neurotoxic/KMO branch of the KP pathway. KMOi treatment administered immediately after the stroke reduced ischemic infarct size (p<.05; n=8 mice/grp) and also improved spontaneous locomotor activity by 72h after stroke compared to vehicle treatment. We also found that genetic deletion of KMO reduces ischemic injury size (p<.05; n=6-7mice/grp) and improves neurological deficit scores.

Conclusions: Inhibition or deletion of KMO reduces neuronal death and improves motor function after stroke in aged male mice. Further studies are needed to ascertain if beneficial effects of KMOi on post-stroke recovery is not due to smaller injury, using aged animals of both sexes.

Abstract WMP114: Changes In Gut Microbiome Precede Cognitive Impairment In A Mouse Model Of Vascular Cognitive Impairment And Dementia

Introduction: Vascular cognitive impairment (VCI) is the second most common cause of clinical dementia after Alzheimer’s disease. VCI results from injury to the cerebral blood vessels. Cerebral perfusion is diminished in elderly individuals and additional reduction of cerebral blood flow increases the risk of developing VCI. These findings have been successfully modeled in mice with bilateral common carotid artery stenosis (BCAS). Age is associated with gut dysbiosis and transplantation of aged microbiome leads to cognitive decline in young animals. However, there are large gaps in our understanding of the molecular mechanisms induced by chronic hypoperfusion contributes to impaired cognitive function.

Methods: C57Bl6 aged (~18m) male mice were subjected to a sham or a BCAS surgery using 0.18mm titanium coils placed on both common carotid arteries. Mice were followed for 90d after surgery to assess both gut microbial content and behavioral changes. 16S ribosomal RNA (rRNA) sequencing analysis was performed on fecal samples collected from aged baseline, sham and BCAS animals at 7 and 28 days. Cognition was assessed using Y-maze. Tissues were collected at the time of euthanasia for metabolomics and histological analysis.

Results: BCAS resulted in significant reduction of cerebral blood flow, measured using laser speckle (p<0.05; n=4/grp; t test). 16s rRNA analysis revealed BCAS led to a remarkable shift in bacterial diversity as early as day 7 in aged male mice, measured by using unweighted UniFrac analysis. These differences remained significant (p<0.05; n=4/grp) in BCAS compared to sham mice on day 28. In depth analysis revealed significant changes at the genus level between both groups. Interestingly, BCAS mice did not show significant difference in Y-maze at day 14, but significant cognitive impairment was found at day 90 compared to sham mice (n=8-9/grp).

Conclusions: We found that chronic cerebral hypoperfusion is associated with significant changes in gut microbiome and cognitive impairment in aged mice. Importantly, shifts in the microbiome preceded cognitive decline. These findings suggest that targeting these detrimental changes in the gut microbiome might be a novel therapeutic strategy to delay or prevent progression of VCI.

Abstract 20: Gut Microbiota-derived Indole Metabolites Influence Outcomes After Neonatal-Hypoxic Ischemic Encephalopathy

Introduction: Neonatal Hypoxic Ischemic Encephalopathy (nHIE) is a leading cause of infant mortality and morbidity worldwide. Males are at greater risk than females, and survivors of nHIE suffer from major disability with limited therapeutic options. Growing clinical and pre-clinical evidence shows neurological injury adversely alters the microbial populations in the gut (dysbiosis) and depletes anti-inflammatory metabolites exclusively made by the gut microbiota. Replacing key microbially-derived beneficial metabolites improves cognitive outcomes in pre-clinical models of adult stroke. However, changes in the gut microbiota and its metabolites after nHIE have not been explored and may lay the foundation for future therapies.

Hypothesis: nHIE leads to gut dysbiosis and reduces microbial-derived metabolites, which worsens neurological outcomes in males and females.

Methods: A modified Rice Vannucci Model on PND9 C57BL/6 mice was used to model nHIE. Fecal, plasma, gut, and brain samples were collected acutely (24hrs) and chronically (7wks) after injury.

Results: We found a significant decrease in 3-indolepropionic acid (p=0.0190, n=4-6), inoxyl-3-sulfate (p=0.0098, n=4-6) and indoxyl acetate (p=0.0096, n=4-6) in the plasma of male mice 24hrs after HIE compared to sham controls, with no significant changes in female plasma. There was a significant increase in indole metabolites in the ischemic hemisphere in both males and females 24hrs after HIE. 7wks after nHIE, there was a significant increase in anxiety-like behavior in males (decrease in % of time immobile during tail suspension=0.018, n=6) and decreased functional ability (nest building score p=0.0147, n=6) in males with HIE compared to sham controls. No significant changes were observed in females. 16S rRNA sequencing data showed dysbiotic microbiota composition after nHIE, consistent with the microbial-metabolite changes found by mass spectroscopy analysis.

Conclusion: nHIE induced brain injury results in gut dysbiosis, with sex-specific alterations in circulating indole metabolites and behavioral deficits. This supports our hypothesis that a sex-specific reduction in bioavailability of microbial-metabolites worsens CNS damage after nHIE.

Mitochondria-containing extracellular vesicles (EV) reduce mouse brain infarct sizes and EV/HSP27 protect ischemic brain endothelial cultures

Ischemic stroke causes brain endothelial cell (BEC) death and damages tight junction integrity of the blood-brain barrier (BBB). We harnessed the innate mitochondrial load of BEC-derived extracellular vesicles (EVs) and utilized mixtures of EV/exogenous 27 kDa heat shock protein (HSP27) as a one-two punch strategy to increase BEC survival (via EV mitochondria) and preserve their tight junction integrity (via HSP27 effects). We demonstrated that the medium-to-large (m/lEV) but not small EVs (sEV) transferred their mitochondrial load, that subsequently colocalized with the mitochondrial network of the recipient primary human BECs. Recipient BECs treated with m/lEVs showed increased relative ATP levels and mitochondrial function. To determine if the m/lEV-meditated increase in recipient BEC ATP levels was associated with m/lEV mitochondria, we isolated m/lEVs from donor BECs pre-treated with oligomycin A (OGM, mitochondria electron transport complex V inhibitor), referred to as OGM-m/lEVs. BECs treated with naïve m/lEVs showed a significant increase in ATP levels compared to untreated OGD cells, OGM-m/lEVs treated BECs showed a loss of ATP levels suggesting that the m/lEV-mediated increase in ATP levels is likely a function of their innate mitochondrial load. In contrast, sEV-mediated ATP increases were not affected by inhibition of mitochondrial function in the donor BECs. Intravenously administered m/lEVs showed a reduction in brain infarct sizes compared to vehicle-injected mice in a mouse middle cerebral artery occlusion model of ischemic stroke. We formulated binary mixtures of human recombinant HSP27 protein with EVs: EV/HSP27 and ternary mixtures of HSP27 and EVs with a cationic polymer, poly (ethylene glycol)-b-poly (diethyltriamine): (PEG-DET/HSP27)/EV. (PEG-DET/HSP27)/EV and EV/HSP27 mixtures decreased the paracellular permeability of small and large molecular mass fluorescent tracers in oxygen glucose-deprived primary human BECs. This one-two punch approach to increase BEC metabolic function and tight junction integrity may be a promising strategy for BBB protection and prevention of long-term neurological dysfunction post-ischemic stroke.

Abstract TP18: Iron Overload Induces Cognitive Deficits And Autophagy Impairment In The Brains Of Aged Mice In A Sex-Dependent Manner

Iron deposits have been observed in postmortem brain samples from Alzheimer’s disease patients. Different iron overload models have been used to study neurodegeneration in young mice. However, the effects of excess iron with aging, which is a critical factor for Alzheimer’s disease and iron deposition in the brain, remain unexplored. In addition, iron metabolism is regulated by autophagy, a cellular process that degrades intracellular components. Brain autophagy is downregulated with aging and in females, and autophagy impairment occurs in many neurodegenerative disorders. Thus, we hypothesized that sex differences exist in autophagy in the brains of aged mice treated with iron overload. We treated aged (18-20 months) WT mice of both sexes with iron overload (5% ferric citrate, FC, 3 days/week/6 weeks), or a vehicle, by oral gavage. We found that aged females showed impairment in conditioning memory (Fear conditioning), but not aged males. Aged females treated with FC also showed significant increase of iron deposition in their brains, compared with control females. However, we did not find significant differences between control and treated male mice. Furthermore, the brain lysates of aged females treated with iron overload showed increased levels of the early autophagy marker BECLIN1 (in both sexes), and enhanced levels of the autophagy cargo p62 (in both sexes) and the lysosomal marker LAMP1 (only in females), compared with control mice. This suggests that iron overload induces the initial stage of autophagy in both sexes, but impairs late autophagy, mainly in female mice, compared with control mice. Furthermore, in primary culture of cerebral endothelial cells (CEC) isolated from aged mice, we found that CEC treated with ferric citrate exhibit enhanced DNA damage and reduced cell proliferation in a dose-dependent manner. Importantly, CEC derived from female mice showed reduced autophagy flux, compared with male CEC. This suggests that iron overload may be more detrimental in the cerebrovasculature of aged female mice than in males, and this could explain iron overload-induced memory deficiency in aged female mice, but not in males.

Upregulation of PD-L1 by SARS-CoV-2 promotes immune evasion

Patients with severe COVID-19 often suffer from lymphopenia, which is linked to T-cell sequestration, cytokine storm, and mortality. However, it remains largely unknown how severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) induces lymphopenia. Here, we studied the transcriptomic profile and epigenomic alterations involved in cytokine production by SARS-CoV-2-infected cells. We adopted a reverse time-order gene coexpression network approach to analyze time-series RNA-sequencing data, revealing epigenetic modifications at the late stage of viral egress. Furthermore, we identified SARS-CoV-2-activated nuclear factor-κB (NF-κB) and interferon regulatory factor 1 (IRF1) pathways contributing to viral infection and COVID-19 severity through epigenetic analysis of H3K4me3 chromatin immunoprecipitation sequencing. Cross-referencing our transcriptomic and epigenomic data sets revealed that coupling NF-κB and IRF1 pathways mediate programmed death ligand-1 (PD-L1) immunosuppressive programs. Interestingly, we observed higher PD-L1 expression in Omicron-infected cells than SARS-CoV-2 infected cells. Blocking PD-L1 at an early stage of virally-infected AAV-hACE2 mice significantly recovered lymphocyte counts and lowered inflammatory cytokine levels. Our findings indicate that targeting the SARS-CoV-2-mediated NF-κB and IRF1-PD-L1 axis may represent an alternative strategy to reduce COVID-19 severity.

Abstract WMP111: MicroRNAs As A Therapeutic Target To Reduce Microglial Activation After Post-stroke Social Isolation

Introduction: Social isolation (SI) and loneliness are linked to all-cause mortality, as well as mortality from stroke and other vascular diseases. However, the mechanisms mediating the effects of social factors on stroke recovery are unknown. We hypothesized that differential expression of miRNAs contributes to the deleterious effects of post-stroke SI.

Methods: Aged (18-20 months) C57BL/6 male mice were used to examine the detrimental effects of post-stroke SI on miRNA profiles in the brain. Mice were randomly assigned to either pair housing (PH), or single housing (SI) three days after a 60-minute transient right middle cerebral artery occlusion (MCAO). At this time point (post-stroke day 3), the infarct is complete, and was equivalent between groups, avoiding potential changes seen with differing infarct sizes. Temporal miRNA profiling of the ipsilateral hemisphere was assessed at two-time points (post-stroke SI D4 and D27). Brain cells were analyzed by flow cytometry.

Results: Post-stroke SI resulted in significant alterations of distinct miRNA profiles within the brain across both acute and chronic time points (n=4/grp, FDR adjusted * p <0.05). MiRNA-mRNA interactional analysis revealed miR-10a-5p and miR-10b-5p as pivotal nodes within the pool of miRNAs that interacted with the largest subset of miRNAs for post-stroke at SI D4 and D27, respectively. Downstream pathway analysis utilizing an independent repository, the KEGG pathway showed 4 days of isolation resulted in the enrichment of pathways related to microglial activation and 27 days of isolation lead to the activation of neuronal-specific pathways that regulate cognition and motivation (FDR adjusted * p <0.05). Independent validation cohorts demonstrated significant activation of microglia at post-stroke SI D4 as assessed by the median fluorescence intensity (MFI) of purinergic receptor P2Y12 (P2RY12), in CD45 int CD11b + P2RY12 + cells in the brain. MFI of P2RY12 was significantly downregulated in post-stroke SI mice at D4 (n=7-8/grp, * p <0.05) compared to PH mice.

Conclusions: These results support our hypothesis that post-stroke SI exacerbates microglia activation, and results in the differential expression of microglial pathway-related miRNAs.

Abstract 40: Gut Dysbiosis Exacerbates Neuroinflammation By Activation Of B Cells In A Mouse Model Of Cerebral Amyloid Angiopathy

Introduction: Cerebral amyloid angiopathy (CAA) is a debilitating disease that leads to intracerebral hemorrhage, white matter disease, and progressive cognitive decline in patients >50 years of age. Studies investigating the neuroimmune landscape in CAA are sparse. Here, we investigate the role of B cells in CAA.

Methods: Pre-symptomatic (2 months) and symptomatic (10-13 months) male Tg-SwDI mice (CAA mice) harboring Swedish, Dutch, and Iowa mutations of human amyloid precursor protein (APP) were used as a mouse model of CAA. Single cells isolated from the brain were analyzed using flow cytometry to characterize neuroinflammation and cognitive impairment was assessed using fear conditioning. Fecal microbiota transplantation (FMT) of the microbiome from pre-symptomatic and symptomatic CAA mice into young wild-type (WT) recipient male mice (2 months) was performed to determine if CAA-induced gut dysbiosis contributes to brain B cell activation.

Results: Cognitive assessment using fear conditioning indicated a significantly lower delta inactive state in symptomatic CAA mice (n=4/grp, * P <0.05) compared to pre-symptomatic CAA mice. Symptomatic CAA mice had a significantly lower relative frequency of microglia (CD45 int CD11b + , n=11-13/grp, ** P <0.01) and significant infiltration of lymphoid (CD45 high CD11b - , n=11-13/grp, *** P <0.001) cells in the brain, as compared to pre-symptomatic CAA mice. Symptomatic CAA mice had significantly higher B cells in the brain (n=10-13/grp, * P <0.05. Further, activated B cells as assessed by the expression level of CD11b showed that CD11b + B cells were significantly higher in the symptomatic CAA brain (n=10-13/grp, * P <0.05). Interestingly, this phenotype was recapitulated in young WT recipients reconstituted with pre-symptomatic CAA and CAA microbiome through FMT. Young WT recipients with CAA biome had significantly higher relative frequency of CD11b + B cells in the brain compared to young recipients with pre-CAA biome (n=7-9/grp, *** P <0.001).

Conclusions: These results suggest that the aberrant activation of B cells in the brain may be influenced by CAA-induced gut dysbiosis. Further investigations upon the functional role of CD11b + B cells in the vascular deposition of Aβ are warranted.

Abstract 105: Sex Differences In The Response To Global Cerebral Hypo-Perfusion In A Mouse Model Of Cerebral Amyloid Angiopathy

Cerebral amyloid angiopathy (CAA) is a disease of small and medium-sized vessels, characterized by amyloid deposition. The incidence of CAA increases with age and evidence reveals worsened cognition in females compared to males. Cerebral hypoperfusion, or a decrease in cerebral blood flow (CBF), changes the integrity of the blood brain barrier and contributes to microhemorrhages, cerebral atrophy, and white matter loss. However, the link between vascular amyloid deposition and hypoperfusion remains understudied. We induced global cerebral hypoperfusion with bilateral carotid artery stenosis (BCAS) in CAA mice of both sexes and examined cognitive deficits, white matter loss, and cerebral gliosis. We hypothesize that chronic cerebral hypoperfusion will accelerate cognitive decline in CAA, increase white matter damage, and induce gliotic changes in the brain.Using a mouse model of CAA (Tg-SwDI), male and female mice (3 months of age) were randomized to either BCAS (n=15) or sham (n=11) surgery using 0.18mm coils to induce global cerebral hypoperfusion. Cognitive (Y-maze (YM), NORT, Water Maze (WM)) and motor function (Open Field (OF)) testing was performed by a blinded investigator prior to surgery (baseline) and at regular intervals until tissue harvest 6 months post-BCAS (PB). The brain and brainstem were harvested for immunohistochemical (IHC) analysis (Kluver-Barrera (KB), Iba-1, GFAP, Myelin Basic Protein (MBP)).Sex-specific changes in spatial memory (YM) and learning (NORT/WM) were present in BCAS mice. Female BCAS mice displayed greater deficits in cognition (NORT) at 3 (p=.0028), 4 (YM, p=.0007), and 5-months PB (NORT, p=.0149). Male BCAS mice demonstrated similar cognitive deficits, but at a later timepoint of 5 months PB (NORT, p=.0007). Both female and male BCAS mice had poorer cognition (WM) and motor function (OF, p=.0011/.0055) 6 months PB. IHC demonstrated increased demyelination (MBP) (p=.0038) and atrophy (KB) in the anterior corpus collosum (p=.0447) and significant gliosis (p=.0230).This study shows that chronic global hypoperfusion accelerates cognitive deficits in a CAA model, an effect that is accelerated in female mice. BCAS led to gliotic changes and demyelination associated with white matter damage in the brain.

Abstract WMP109: Aged Maternal Biome Impairs Offspring Health

Background: The gut and its microbiome have become highlighted because of their holistic effect on the body in health and disease. The bi-directional communication of the gut-brain axis is highly involved in, among others, the immune response. Additionally, the maternal gut microbiome affects offspring brain, immune system, and gut microbiome formation and development. Therefore, an aged and unhealthy maternal biome that is may increase both stroke risk factors among offspring.

Method: Young female C57B6 mice 3-month (M) of age had their host gut bacteria cleared via antibiotic treatment prior to recolonization via fecal microbiome transplants from 3M control, and 18M reproductively senescent female mice. The subsequent offspring was aged to 18 months, followed by behavioral tests, glucose tolerance, and blood pressure measurement, prior to a transient 90-minute middle cerebral artery occlusion (MCAO).

Results: Compared to control females with 3M biome, females with an aged biome had decreased fecundity from 26.4 days to 54.75 days at the onset of breeding to birth of pups (p=0.0018). There was no change in estrus cycle between the groups. The offspring gut microbiome had been affected in a sex specific manner. Female pups from dysbiotic, aged, biome mothers differed significantly in terms of b-diversity compared to those from control mothers (p=0.009) with pathogenic increases to firmicutes shifting the F:B ratio. There was a less pronounced trend in male offspring (p=0.241). Interestingly, no weight differences were observed in offspring depending on the maternal biome. At 2M of age, a depressive phenotype in tail suspension test was noted for male(p=0.0001) and female (p=0.0059). However, at 6M and older, the depressive phenotype subsided. Male offspring at 18M demonstrated a significant change (p=0.0001) in Glucose tolerance test compared to age matched females.

Conclusion: The maternal microbiome has a significant impact on offspring biome composition and health. Mice from mothers with aged microbiome exhibited early life depressive phenotypes, slower glucose metabolism, and a pathogenic gut microbiome composition. Therefore, maternal gut has transgenerational health effects which may be exacerbating stroke risk and potentially outcome.

Abstract TP170: Heterochronic Parabiosis Lowers Microglia Activation And Myeloid Infiltration In Aged Parabiont

Introduction: Of the 795,000 people who suffer strokes annually, 75% are over the age of 65. Aging is a major risk factor for stroke. The risk of stroke doubles every decade after the age of 55. Aging leads to dramatic changes in peripheral myeloid cells and increases the activation state of microglia in the brain. Although age is an important determinant of stroke susceptibility and outcome, the contribution from the aged immune system remains unclear.

Hypothesis: We hypothesize that aged mice (18-22 mo) parabionts paired with a young parabiont (2-3 mo) would have less microglia activation due to exposure to systemic factors from young mice when compared to aged mice paired with aged mice (18-22 mo).

Methods: Young Pep-boy mice (haplotype CD45.1) were surgically paired with aged mice (haplotype CD45.2) for two months. The brains of these mice were then subjected to flow cytometry analysis. Brain single cell suspensions were isolated and immunophenotyped with a microglia specific panel.

Results: Our results show that myeloid infiltration was decreased in the aged parabiont (paired with a young mouse) compared to its naïve counterpart (n=3-6/ grp, p = 0.0036). Microglia activation was assessed utilizing a homeostatic marker, P2RY12, and a microglia specific marker, Tmem119. Interestingly, the expression of Tmem119 on CD45 int CD11b + cells was significantly increased in the aged parabionts compared to aged, naïve mice (n=3-6/ grp, p =0.0006), however, P2RY12 trended upward in the aged parabiont (n=3/6 /grp, p =0.0742). This suggests that the shared circulation created between the heterochronic pair led to a reduction in immune activation in the aged parabiont. Thus, the young parabiont allows the aged parabiont access to rejuvenating factors through the shared flow of blood which reduced neuroinflammation.

Conclusion: Future studies are needed to identify the specific factors contributing to reduced microglial activation and lowered infiltration of peripheral immune cells induced by pairing with young animals. Studies examining the immune response to stroke in young and aged parabionts are needed.

Effects of Objective and Perceived Social Isolation on Cardiovascular and Brain Health: A Scientific Statement From the American Heart Association

Background Social isolation, the relative absence of or infrequency of contact with different types of social relationships, and loneliness (perceived isolation) are associated with adverse health outcomes. Objective To review observational and intervention research that examines the impact of social isolation and loneliness on cardiovascular and brain health and discuss proposed mechanisms for observed associations. Methods We conducted a systematic scoping review of available research. We searched 4 databases, PubMed, PsycInfo, Cumulative Index of Nursing and Allied Health, and Scopus. Findings Evidence is most consistent for a direct association between social isolation, loneliness, and coronary heart disease and stroke mortality. However, data on the association between social isolation and loneliness with heart failure, dementia, and cognitive impairment are sparse and less robust. Few studies have empirically tested mediating pathways between social isolation, loneliness, and cardiovascular and brain health outcomes using appropriate methods for explanatory analyses. Notably, the effect estimates are small, and there may be unmeasured confounders of the associations. Research in groups that may be at higher risk or more vulnerable to the effects of social isolation is limited. We did not find any intervention studies that sought to reduce the adverse impact of social isolation or loneliness on cardiovascular or brain health outcomes. Conclusions Social isolation and loneliness are common and appear to be independent risk factors for worse cardiovascular and brain health; however, consistency of the associations varies by outcome. There is a need to develop, implement, and test interventions to improve cardiovascular and brain health for individuals who are socially isolated or lonely.

Revisiting regulatory T cells for stroke therapy

Stroke is a leading cause of death and long-term disability. T cells have been extensively studied for their dual role in regulating immunity and inflammation following stroke. In this issue of the JCI, Cai, Shi, et al. demonstrated that CD8+ regulatory-like T cells (CD8+ TRLs) are one of the earliest lymphocyte subtypes to enter the brain after experimental ischemic stroke. Using a mouse model of stroke and comprehensive experimental approaches, the authors found that CD8+ TRLs reduced both brain damage and functional deficits in both young and aged mice. These unique early responding regulatory T cells may also play a role in a wide array of other T cell-mediated neurological disorders.

Dendrimer nanotherapy for severe COVID-19 attenuates inflammation and neurological injury markers and improves outcomes in a phase2a clinical trial

Hyperinflammation triggered by SARS-CoV-2 is a major cause of disease severity, with activated macrophages implicated in this response. OP-101, a hydroxyl-polyamidoamine dendrimer-N-acetylcysteine conjugate that specifically targets activated macrophages, improves outcomes in preclinical models of systemic inflammation and neuroinflammation. In this multicenter, randomized, double-blind, placebo-controlled, adaptive phase 2a trial, we evaluated safety and preliminary efficacy of OP-101 in patients with severe COVID-19. Twenty-four patients classified as having severe COVID-19 with a baseline World Health Organization seven-point ordinal scale of ≥5 were randomized to receive a single intravenous dose of placebo (n = 7 patients) or OP-101 at 2 (n = 6), 4 (n = 6), or 8 mg/kg (n = 5 patients). All study participants received standard of care, including corticosteroids. OP-101 at 4 mg/kg was better than placebo at decreasing inflammatory markers; OP-101 at 4 and 8 mg/kg was better than placebo at reducing neurological injury markers, (neurofilament light chain and glial fibrillary acidic protein). Risk for the composite outcome of mechanical ventilation or death at 30 and 60 days after treatment was 71% (95% CI: 29%, 96%) for placebo and 18% (95% CI: 4%, 43%; P = 0.021) for the pooled OP-101 treatment arms. At 60 days, 3 of 7 patients given placebo and 14 of 17 OP-101-treated patients were surviving. No drug-related adverse events were reported. These data show that OP-101 was well tolerated and may have potential to treat systemic inflammation and neuronal injury, reducing morbidity and mortality in hospitalized patients with severe COVID-19.

CD11bhigh B Cells Increase after Stroke and Regulate Microglia

Recent studies have highlighted the deleterious contributions of B cells to post-stroke recovery and cognitive decline. Different B cell subsets have been proposed on the basis of expression levels of transcription factors (e.g., T-bet) as well as specific surface proteins. CD11b (α-chain of integrin) is expressed by several immune cell types and is involved in regulation of cell motility, phagocytosis, and other essential functions of host immunity. Although B cells express CD11b, the CD11b^high subset of B cells has not been well characterized, especially in immune dysregulation seen with aging and after stroke. Here, we investigate the role of CD11b^high B cells in immune responses after stroke in young and aged mice. We evaluated the ability of CD11b^high B cells to influence pro- and anti-inflammatory phenotypes of young and aged microglia (MG). We hypothesized that CD11b^high B cells accumulate in the brain and contribute to neuroinflammation in aging and after stroke. We found that CD11b^high B cells are a heterogeneous subpopulation of B cells predominantly present in naive aged mice. Their frequency increases in the brain after stroke in young and aged mice. Importantly, CD11b^high B cells regulate MG phenotype and increase MG phagocytosis in both ex vivo and in vivo settings, likely by production of regulatory cytokines (e.g., TNF-α). As both APCs and adaptive immune cells with long-term memory function, B cells are uniquely positioned to regulate acute and chronic phases of the post-stroke immune response, and their influence is subset specific.

Abstract 5279: Prognostic serum biomarkers in cancer patients with COVID-19: A systematic review

Purpose: COVID-19 has led to 4 million deaths worldwide since 2019. COVID-19 patients with cancers likely express biomarker changes in circulation. While many biomarker studies focused on COVID-19 diagnosis and prognosis, the panel of biomarkers used in SARS-CoV-2 infected cancer patients for COVID-19 severity and prognosis are largely unclear. Therefore, this systematic review aims to determine what biomarkers have been measured in cancer patients with COVID-19 and their prognostic utility.

Methods: A systematic literature review in PubMed, Embase, and Scopus was performed on June 16th, 2021. The search keywords coronavirus, neoplasm, biomarkers, and disease progression were used to filter out 17 eligible studies, which were then carefully evaluated.

Results: A total of 4,168 patients from 17 eligible articles were included in this study. Sixteen types of cancer and 60 biomarkers were identified. The majority of changed biomarkers in the cancer patients with COVID-19 compared to the healthy group and non-cancer patients with COVID-19 were biochemical and inflammatory markers. The up-regulated markers, including CRP, D-dimer, ferritin, IL-2R, IL-6, LDH, and PCT, were identified in eligible studies. Albumin and hemoglobin were significantly down-regulated in cancer patients with COVID-19. Additionally, we observed that the SARS-CoV-2 infected cancer patients with lower levels of CRP, ferritin, and LDH successfully survived from antiviral drug and immunotherapy for COVID-19 treatments.

Conclusion: Several important clinical biomarkers, such as CRP, ferritin, and LDH, may serve as the prognostic markers to predict the outcomes following COVID-19 treatment and monitor the deterioration of COVID-19 in cancer patients.

Citation Format: Yun-Ju Lai, Te-An Lee, Shih-Han Wang, Chia-Wei Li, Louise D. McCullough, Dhimiter Bello. Prognostic serum biomarkers in cancer patients with COVID-19: A systematic review [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5279.

Toward a Better Understanding of Sex- and Gender-Related Differences in Endovascular Stroke Treatment: A Scientific Statement From the American Heart Association/American Stroke Association

There are many unknowns when it comes to the role of sex in the pathophysiology and management of acute ischemic stroke. This is particularly true for endovascular treatment (EVT). It has only recently been established as standard of care; therefore, data are even more scarce and conflicting compared with other areas of acute stroke. Assessing the role of sex and gender as isolated variables is challenging because they are closely intertwined with each other, as well as with patients' cultural, ethnic, and social backgrounds. Nevertheless, a better understanding of sex- and gender-related differences in EVT is important to develop strategies that can ultimately improve individualized outcome for both men and women. Disregarding patient sex and gender and pursuing a one-size-fits-all strategy may lead to suboptimal or even harmful treatment practices. This scientific statement is meant to outline knowledge gaps and unmet needs for future research on the role of sex and gender in EVT for acute ischemic stroke. It also provides a pragmatic road map for researchers who aim to investigate sex- and gender-related differences in EVT and for clinicians who wish to improve clinical care of their patients undergoing EVT by accounting for sex- and gender-specific factors. Although most EVT studies, including those that form the basis of this scientific statement, report patient sex rather than gender, open questions on gender-specific EVT differences are also discussed.

Clostridium difficile Infection Does Not Impact Outcomes in Stroke Patients

BACKGROUND

Data are limited for Clostridium difficile infection (CDI) in stroke patients. This study investigates incidence, patient characteristics, clinical features, and outcomes of CDI following stroke, including ischemic stroke (IS), intracerebral hemorrhage (ICH), and aneurysmal subarachnoid hemorrhage (SAH).

METHODS

The hospital database was queried for all patients with IS, ICH, or SAH from 2010 through 2014. Patients who underwent testing for C. difficile testing (CDT) through polymerase chain reaction were assessed. Demographics, risk factors, clinical features, and outcomes were recorded. Fever was defined as temperature >101°F.

RESULTS

CDT was obtained in 555/4004 patients and was positive in 99, for CDI incidence of 2.5% [SAH 6.5% (26/402) vs. 2.9% in ICH (21/730) and 1.8% in IS (52/2872)]. There were no differences in demographics, severity [ICH score, National Institutes for Health Stroke Scale (NIHSS), Hunt Hess (HH), Glasgow coma scale (GCS)], mechanical ventilation, neurosurgical procedures, stress ulcer prophlyaxis or antibiotic use. Steroid use (P=0.0273) and male sex (P=0.0112) were associated with a positive CDT. On the day of diagnosis, 61% of CDT-positive patients had white blood cell <12, and 71% were afebrile. Length of stay, discharge disposition, mortality, and 3-month and 12-month modified Rankin, were not impacted by CDT results. Two patients with CDI required bowel resection.

CONCLUSION

CDI incidence following stroke was low and most common with SAH. Male sex and steroid use were associated with a positive result. Leukocytosis and fever occurred in under half of infected patients. Outcome measures were not impacted by CDI.

Aging augments type 2 cytokine responses in ILC2s leading to reparative, M2-like microglia

Aging affects immunologic responses by a global suppression of the immune system, including dysregulation of cytokine mediators, leading to increased inflammation throughout all systems, termed inflammaging. However, understanding mechanisms of healthy aging can bypass this effect. Inflammaging also leads to poor outcomes during brain injury, making immune-targeting therapeutics tantamount to overall brain health and longevity. Two candidate immune cells microglia and group 2 innate lymphoid cells (ILC2s) may control immune responses in the aged brain Therefore, we hypothesized that ILC2s are the brains’ gatekeepers of microglia polarization to a reparative, M2-like phenotype under: (1) homeostatic conditions and (2) with aging. To address this, we used flow cytometry to quantify ILC2s between young and aged male and female C57Bl6/J mice, showing an age-related increase in aged males. Moreover, when we stimulated ILC2s, the data indicated an age-related increase in cytokine production in males. We also utilized conditioned media transfer experiments from stimulated young and aged ILC2s to quiescent microglia and assessed their morphologic, genomic, proteomic, and functional changes using microscopy, qRT-PCR, Western immunoblotting, and phagocytosis assays. We showed more complex microglia morphology (indicating microglial priming) and an increase in reparative mRNA, proteins, and phagocytic function in microglia, which was augmented by aged ILC2s. Taken together, we have defined the capacity of ILC2 soluble factors to polarize microglia to a reparative phenotype and maintain this in aging.

Supported by the NIH NINDS F31NS118983

The Stroke Preclinical Assessment Network: Rationale, Design, Feasibility, and Stage 1 Results

Cerebral ischemia and reperfusion initiate cellular events in brain that lead to neurological disability. Investigating these cellular events provides ample targets for developing new treatments. Despite considerable work, no such therapy has translated into successful stroke treatment. Among other issues-such as incomplete mechanistic knowledge and faulty clinical trial design-a key contributor to prior translational failures may be insufficient scientific rigor during preclinical assessment: nonblinded outcome assessment; missing randomization; inappropriate sample sizes; and preclinical assessments in young male animals that ignore relevant biological variables, such as age, sex, and relevant comorbid diseases. Promising results are rarely replicated in multiple laboratories. We sought to address some of these issues with rigorous assessment of candidate treatments across 6 independent research laboratories. The Stroke Preclinical Assessment Network (SPAN) implements state-of-the-art experimental design to test the hypothesis that rigorous preclinical assessment can successfully reduce or eliminate common sources of bias in choosing treatments for evaluation in clinical studies. SPAN is a randomized, placebo-controlled, blinded, multilaboratory trial using a multi-arm multi-stage protocol to select one or more putative stroke treatments with an implied high likelihood of success in human clinical stroke trials. The first stage of SPAN implemented procedural standardization and experimental rigor. All participating research laboratories performed middle cerebral artery occlusion surgery adhering to a common protocol and rapidly enrolled 913 mice in the first of 4 planned stages with excellent protocol adherence, remarkable data completion and low rates of subject loss. SPAN stage 1 successfully implemented treatment masking, randomization, prerandomization inclusion/exclusion criteria, and blinded assessment to exclude bias. Our data suggest that a large, multilaboratory, preclinical assessment effort to reduce known sources of bias is feasible and practical. Subsequent SPAN stages will evaluate candidate treatments for potential success in future stroke clinical trials using aged animals and animals with comorbid conditions.

Sex-Specific Immune Responses in Stroke

In both acute and chronic diseases, functional differences in host immune responses arise from a multitude of intrinsic and extrinsic factors. Two of the most important factors affecting the immune response are biological sex and aging. Ischemic stroke is a debilitating disease that predominately affects older individuals. Epidemiological studies have shown that older women have poorer functional outcomes compared with men, in part due to the older age at which they experience their first stroke and the increased comorbidities seen with aging. The immune response also differs in men and women, which could lead to altered inflammatory events that contribute to sex differences in poststroke recovery. Intrinsic factors including host genetics and chromosomal sex play a crucial role both in shaping the host immune system and in the neuroimmune response to brain injury. Ischemic stroke leads to altered intracellular communication between astrocytes, neurons, and resident immune cells in the central nervous system. Increased production of cytokines and chemokines orchestrate the infiltration of peripheral immune cells and promote neuroinflammation. To maintain immunosurveillance, the host immune and central nervous system are highly regulated by a diverse population of immune cells which are strategically distributed within the neurovascular unit and become activated with injury. In this review, we provide a comprehensive overview of sex-specific host immune responses in ischemic stroke.

Aging Microbiota-Gut-Brain Axis in Stroke Risk and Outcome

The microbiota-gut-brain-axis (MGBA) is a bidirectional communication network between gut microbes and their host. Many environmental and host-related factors affect the gut microbiota. Dysbiosis is defined as compositional and functional alterations of the gut microbiota that contribute to the pathogenesis, progression and treatment responses to disease. Dysbiosis occurs when perturbations of microbiota composition and function exceed the ability of microbiota and its host to restore a symbiotic state. Dysbiosis leads to dysfunctional signaling of the MGBA, which regulates the development and the function of the host's immune, metabolic, and nervous systems. Dysbiosis-induced dysfunction of the MGBA is seen with aging and stroke, and is linked to the development of common stroke risk factors such as obesity, diabetes, and atherosclerosis. Changes in the gut microbiota are also seen in response to stroke, and may impair recovery after injury. This review will begin with an overview of the tools used to study the MGBA with a discussion on limitations and potential experimental confounders. Relevant MGBA components are introduced and summarized for a better understanding of age-related changes in MGBA signaling and its dysfunction after stroke. We will then focus on the relationship between the MGBA and aging, highlighting that all components of the MGBA undergo age-related alterations that can be influenced by or even driven by the gut microbiota. In the final section, the current clinical and preclinical evidence for the role of MGBA signaling in the development of stroke risk factors such as obesity, diabetes, hypertension, and frailty are summarized, as well as microbiota changes with stroke in experimental and clinical populations. We conclude by describing the current understanding of microbiota-based therapies for stroke including the use of pre-/pro-biotics and supplementations with bacterial metabolites. Ongoing progress in this new frontier of biomedical sciences will lead to an improved understanding of the MGBA's impact on human health and disease.