Diabetes is an established driver of microvascular disease, causing complications such as retinopathy, nephropathy, and neuropathy. However, the mechanisms whereby diabetes disrupts brain microvascular function remain poorly understood. Diabetes is strongly associated with cognitive impairments, including Alzheimer's Disease (AD), in which pericyte pathology is implicated in cerebrovascular dysfunction. Pericytes are critical regulators of blood-brain barrier integrity and capillary blood flow, yet their behavior during early diabetes remains uncharacterized. Using a 14-day streptozotocin (STZ) mouse model of early hyperglycemia, we demonstrate two distinct phenotypic changes in the brain prior to pericyte loss. First, tissue clearing and 3D imaging reveal significantly increased pericyte-vessel bridging across multiple brain regions, including the entorhinal cortex and hippocampus, regions among the earliest and most affected in AD. Second, longitudinal two-photon microscopy demonstrates that brain pericytes constrict capillaries in a manner correlated with blood-glucose levels. Capillary constriction occurs at pericyte soma and is associated with significantly reduced red blood cell velocity. Pericytes exhibiting early constriction predominantly maintain this phenotype rather than transitioning to a bridging state, suggesting these represent distinct disease-associated behaviors. These findings indicate that early pericyte pathology may contribute to cerebrovascular dysfunction in diabetes, with implications for understanding microvascular mechanisms linking diabetes and AD.
OBJECTIVE:To analyze clinical characteristics, risk factors, and a predictive model for non-aspiration stroke-associated infections (NASAI) in acute ischemic stroke (AIS) patients receiving intravenous alteplase thrombolysis. METHODS:This prospective cohort study included AIS patients from the DATIS cohort (Jan 2018-Jul 2024) who received rt-PA thrombolysis. NASAI was defined as stroke-associated infection without evidence of aspiration. Patients were randomized 7:3 into training (n=1171) and validation (n=503) sets. LASSO and logistic regression were used to select predictors. Model performance was assessed by ROC curve, calibration curve (CC), and decision curve analysis (DCA). RESULTS:Among 1828 patients, NASAI prevalence was 10.72% (196/1828), accounting for 56% of all SAI cases. Independent risk factors included older age (OR 1.62), hypertension (1.64), higher admission NIHSS (4.03), heart rate (1.06), and white blood cell count (1.16). The nomogram showed AUCs of 0.80 (training) and 0.78 (validation), with good calibration and net benefit on DCA. CONCLUSION:A nomogram based on five easily accessible variables demonstrated strong predictive performance for NASAI, offering a practical tool for early risk assessment in thrombolyzed AIS patients.
Hemolysis products are very highly cerebrotoxic. However, surgical approaches to evacuate hematoma-containing hemolysis products after intracerebral hemorrhage (ICH) surprisingly showed mixed therapeutic effects. Thus, alternative non-invasive approaches, e.g., those that improve hematoma clearance by endogenous phagocytes, have been experimentally tested and, to date, show highly promising therapeutic benefit for post-ICH recovery. Resident microglia (MG) and monocyte-derived macrophages (together MΦ), important components of the innate immune system, are two highly related professional scavenger cell types that mediate hematoma clearance after ICH. MΦ readily conduct phagocytosis/endocytosis of extravasated blood components, dead/apoptotic cells, and various cellular debris. Unless removed from the brain, these elements induce cytotoxicity and lingering inflammation and form a physical barrier to neuronal re-connectivity, thereby impeding recovery after ICH. Hence, evaluating new therapeutic approaches to improve the efficacy of MΦ-mediated hematoma cleanup could provide a promising strategy to promote post-ICH repair and recovery. The mechanistic bases for these cleanup approaches include: (1) enhancing the expression of scavenger receptors and other phagocytosis-assisting proteins in the MΦ'; (2) blocking the molecules that provide "do not eat me" (anti-phagocytic) signals presenting on the surface of apoptotic cells/debris to be phagocytosed; and (3) protecting the intra-MΦ "health" to sustain effective debris engulfment and degradation, without injuring the phagocytes themselves. We will primarily focus on MΦ-mediated erythrophagocytosis and the detoxification of hemolytic products (hemoglobin, heme, and iron) in the ICH-affected brain. By providing numerous pre-clinical examples, we will demonstrate that the regulation of cleanup is a potential clinically relevant therapeutic target for ICH.
BACKGROUND/HYPOTHESIS:Glucose oxidation is the brain's main way of producing the energy needed for neuronal signaling and essential maintenance tasks. When the brain cannot produce or use energy efficiently, neurons become less functional and more vulnerable. Although ageing is thought to affect brain metabolism, precise measurements of oxidative glucose use are still limited. METHODS/RESULTS:This review brings together current evidence on how brain energy metabolism changes during healthy ageing, dementia, and major neurological disorders, using absolute measurements of oxygen consumption. Overall, the data show that oxidative glucose metabolism stays stable in healthy brain ageing. In contrast, it drops by up to ~40% in Alzheimer's disease, more with greater disease severity, and by ~ 25% in multiple sclerosis and hydrocephalus. These declines reduce the amount of ATP available for both signaling and basic cellular functions, which are essential for perception and cognition. Metabolic water production is proportionately reduced when CMRO2 decreases in diseased brain, and its secretion into interstitial fluid is diminished. CONCLUSION/INTERPRETATION:In disease, lower oxidative metabolic activity reduces metabolic water production, which may in turn affect brain fluid dynamics, including processes involved in neuroprotection and waste clearance.
Germinal matrix hemorrhage (GMH) is a localized form of developmental cerebral microvascular failure and a major cause of mortality and long-term neurological disability in preterm infants. The GM is a highly angiogenic, protease-active developmental niche that operates near the limits of vascular stability under tightly regulated intrauterine conditions. Preterm birth disrupts this balance by removing late-gestational immune modulation and exposing protease-primed GM vessels to exaggerated inflammatory activation. Dysregulated innate immune responses amplify endothelial junctional cleavage and basement-membrane degradation and reprogram the local myeloid environment toward neutrophil-derived protease release. We propose a unified protease-threshold framework in which GMH occurs when inflammatory amplification drives proteolytic activity beyond the structural resilience of the immature GM vasculature. This model may help account for the timing, localization, and heterogeneity of GMH and provides a testable framework for studying developmental neurovascular vulnerability, biomarker discovery, and preventive strategies.
Electrophysiological recordings such as electroencephalogram (EEG) are gold standards for measuring neuronal activity, which requires substantial oxidative metabolism (CMRO2) for support. Although EEG-CMRO2 links have long been assumed or measured qualitatively, quantitative characterization in humans remains limited, hindering our understanding of neurometabolic mechanisms and the utility of electrophysiological biomarkers in brain disease. Given that the neurometabolic process is sensitive to baseline perfusion and aerobic glycolysis, we hypothesized EEG-CMRO2 associations would show strong network and sex dependence, as these factors strongly influence perfusion and glycolytic activity. Here, we quantified EEG-CMRO2 associations and their underlying profiles (with cerebral blood flow and oxygen extraction fraction) across brain networks and between sexes. We further investigated how the EEG-CMRO2 association influenced resting-state functional magnetic resonance imaging (rs-fMRI) measurements. Our main findings suggest: (1) globally, CMRO2 only partially mediated EEG-fMRI relationships, revealing O2-independent coupling pathways; (2) EEG-CMRO2 associations varied significantly across functional networks; (3) sex differences in EEG-CMRO2 associations showed minimal network dependence and (4) high-frequency and low-frequency EEG bands exhibited opposite-polarities CMRO2 associations between males and females. These findings demonstrate that neurometabolic coupling differs across functional networks, frequency bands, and importantly, across biological sexes, with important implications for interpreting developing electrophysiological biomarkers and rs-fMRI measurements.
BACKGROUND:Stroke is a major cause of long-term disability, yet the effects of cortical injury on downstream spinal and peripheral neuromuscular systems remain incompletely understood and have not been comprehensively evaluated in translational models. We aimed to longitudinally characterize post-stroke neuromotor dysfunction across cortical, spinal, and peripheral levels using clinically derived electrophysiological biomarkers in a mouse model of focal ischemia. METHODS:Adult male C57BL/6J mice underwent 60-minute transient middle cerebral artery occlusion (tMCAO) or sham surgery. Electrophysiological assessments, including motor-evoked potentials (MEPs), H-reflexes, compound muscle action potentials (CMAP), and motor unit number estimation (MUNE), were performed at days 7 and 21 after stroke. RESULTS:Stroke was associated with early suppression of infarct-side cortical output, reflected by reduced MEP amplitudes at day 7, while contralateral cortical excitability increased over time. Spinal excitability increased persistently after stroke and correlated with infarct size (r = 0.67, p = 0.024). At day 7, infarct-side MEP amplitudes were inversely associated with H-reflex (r = -0.66, p = 0.029). MUNE declined at day 7, followed by reduced CMAP amplitudes at day 21. CONCLUSIONS:Stroke was associated with temporally ordered neuromotor abnormalities across cortical, spinal, and peripheral systems, supporting a translational electrophysiological framework for testing recovery strategies.
Perihematomal (PH) edema (PHE) is an unvarying sequel of intracerebral hemorrhage (ICH). In contrast to cerebral ischemia, wherein the consequences of edema are incontrovertible, the effects of PHE on clinical outcome after ICH are uncertain. We performed a critical review of publications on the natural history of PHE. We review mechanisms of formation, including clot contraction during the hyperacute phase, and the prognostic utility of PHE. Although data support the hypothesis that PHE adversely affects clinical outcome, data interpretation is hampered by key factors: (1) Since PHE is formed by clot contraction that releases serum (interstitial edema), and blood-brain barrier dysfunction that releases plasma (vasogenic edema), PHE quantification is complex. (2) Although the apparent diffusion coefficient (ADC) is touted as distinguishing vasogenic from cytotoxic (cellular) edema, cellular changes that decrease ADC can be masked by increases in extracellular fluid. (3) Decreased ADC occurs with cytotoxic edema as well as other conditions with increase cellular water, including glial activation, inflammatory cell infiltration and heme degradation products. (4) Decreased ADC often is attributed to tissue ischemia, but assessments have largely failed to demonstrate severe ischemia of PH tissues. PHE is an acceptable predictor of outcome in ICH.
Mechanical thrombectomy has made angiographic reperfusion routine for large-vessel occlusion stroke, yet functional recovery remains inconsistent. Growing evidence links this therapeutic ceiling to the no-reflow phenomenon, defined as persistent tissue-level hypoperfusion despite proximal patency. No-reflow may arise from ischemia-reperfusion microvascular injury and distal microembolization, creating conditions that may promote immunothrombotic obstruction. Neutrophil-platelet cooperation, endothelial activation, and neutrophil extracellular traps represent candidate mechanisms linking capillary failure to futile reperfusion. Future trials should prospectively phenotype no-reflow with early perfusion imaging, integrate mechanistic biomarkers, and test microvascular-facing adjuncts that convert macrovascular recanalization into durable tissue reperfusion.
BACKGROUND:Intracranial atherosclerotic disease (ICAD) is a leading cause of ischemic stroke, yet how post-stenotic cerebral hemodynamics regulate endothelial phenotype remains poorly defined. We tested whether focal post-stenotic low wall shear stress (WSS) in patient-specific middle cerebral artery (MCA) stenoses associates with endothelial proliferation and pro-thrombotic activation. METHODS:CTA-derived geometries from SAMMPRIS participants were reconstructed for computational fluid dynamics (CFD) analysis (n=33 paired MCAs). A subset of stenotic and contralateral control models was 3D-printed, endothelialized with Human Umbilical Vein Endothelial Cells (HUVECs), and perfused under physiologic flow (n=8 pairs). Anatomically matched regions were analyzed for proliferation (Ki-67), biglycan (BGN), cell morphology, and pro-thrombotic mediators (LPCAT2, PAI1) using confocal imaging and automated segmentation. RESULTS:Stenotic MCAs exhibited significantly greater post-stenotic low-WSS area ratios than paired controls (p<0.0001). Distal low-WSS area correlated with increased proliferation (r=0.688, p=0.013) and BGN expression (r=0.580, p=0.046), confirmed by bootstrapping (p<0.001). Low-WSS regions demonstrated reduced cell area (0.85-fold, p=0.0013) and elevated LPCAT2 (1.34-fold) and PAI1 (1.41-fold) expression (both p<0.0001), which inversely correlated with particle-flow linearity (p≤0.031). CONCLUSIONS:Patient-specific cerebral stenoses generate focal low-WSS environments that can induce endothelial proliferation and pro-thrombotic signaling, supporting a mechanistic link between intracranial hemodynamics and endothelial dysfunction in ICAD.
Brain arteriovenous malformations (bAVMs) are high-risk vascular lesions prone to intracranial hemorrhage, with unclear upstream regulatory mechanisms. We integrated 5-methylcytosine (m5C) RNA methylation sequencing and transcriptomics in ruptured and unruptured bAVMs to identify differentially methylated non-coding RNAs. Functional validation was performed in human tissues, HUVECs, and zebrafish models. m5C profiling revealed global methylation remodeling in ruptured bAVMs, with enrichment of EndMT and Wnt/β-catenin pathways. USP2-AS1 emerged as a key lncRNA showing increased methylation and expression, predominantly in endothelial cells. In HUVECs, USP2-AS1 promoted EndMT-like changes and migration, while its knockdown had opposite effects. NSUN6 was identified as the primary methyltransferase mediating m5C modification of USP2-AS1. NSUN6-driven methylation enhanced endothelial plasticity in vitro and induced vascular abnormalities and hemorrhage in zebrafish. Mechanistically, USP2-AS1 activated Wnt/β-catenin signaling, which was essential for these effects and reversible by pathway inhibition. These findings identify a NSUN6-USP2-AS1-Wnt/β-catenin axis that drives endothelial dysfunction and bAVM rupture, suggesting potential therapeutic targets for vascular stabilization.
Physiological factors, such as cerebral blood flow, blood pressure, respiratory rate, and body temperature are critical determinants of ischemic stroke pathophysiology, infarct development, and overall outcomes, and vice versa. However, despite long-standing guidelines recommending rigorous monitoring of key physiological factors, this aspect is not always incorporated into experimental designs and is generally underreported. Further, even when collected it is not always clear whether the data are integrated into the interpretation of results, potentially affecting translation. This review outlines the importance of monitoring, reporting and interpreting key physiological parameters in experimental stroke models, including the cardiovascular and respiratory systems, metabolism, temperature, circadian rhythm and intracranial pressure. Our aim is to provide researchers with an understanding of 1) different aspects of physiology that can affect experimental outcomes; 2) why and when it is important to monitor animal physiology in the context of ischemic stroke; 3) potential options for monitoring equipment and procedures; and 4) why accurate and transparent reporting and deliberate incorporation of physiological data into interpretation will enhance experimental rigor and strengthen future translational outcomes.
BACKGROUND:Previous studies have indicated associations between imaging markers of cerebral small vessel disease (CSVD), but their genetic correlations remain largely unknown. METHODS:We analyzed large-scale GWAS summary data for lacunar stroke (6,030 cases; 248,929 controls), cerebral microbleeds (N=25,862), white matter hyperintensities (WMH; 18,381 population-based subjects and 2,850 stroke patients), perivascular spaces (PVS; N=40,095), and brain volume (N=33,224). Linkage disequilibrium score regression (LDSR) was used to estimate heritability and genetic correlations. Bidirectional Mendelian randomization (MR) and mediation MR were performed to assess causal relationships. RESULTS:Except for cerebral microbleeds, all other CSVD imaging markers showed significant heritability, with decreased brain volume being the most prominent. MR analyses provided evidence supporting potential unidirectional causal relationships where lacunar stroke increased the risk of WMH, PVS and decreased brain volume. MR identified a potential bidirectional causal relationship between WMH and decreased brain volume. Mediation analysis revealed that lacunar stroke mediated the effects of hypertension on various imaging markers. CONCLUSION:Cerebral microbleeds appear genetically distinct from other CSVD markers. Lacunar stroke acts as a key upstream factor linking multiple imaging features, while WMH and brain atrophy exhibit a potential bidirectional causal relationship. These findings provide insight into the heterogeneous mechanisms underlying CSVD imaging markers.
Germinal matrix hemorrhage (GMH) remains a major intracranial complication with significant mortality and lifelong neurodevelopmental deficits in preterm infants. Disruption of the fragile germinal matrix neurovascular unit interferes with the natural course of brain maturation, resulting in both gray and white matter injury as well as persistent motor and cognitive dysfunction. Currently, no disease-modifying therapy is available to reverse established GMH or prevent its long-term neurological sequelae, although several preventive strategies can reduce the risk of hemorrhage in selected clinical contexts. Given the clear need for effective therapeutics, experimental models are essential for elucidating the cellular and molecular mechanisms underlying the etiology and pathophysiological progression of GMH. This review highlights recent preclinical advances in GMH, including its underlying causes and natural history, the development of animal models, and the identification of potential therapeutic targets.
Deficits in the synaptic vesicle protein 2A (SV2A) have been reported in various neurodegenerative diseases including Alzheimer’s and Huntington’s disease (HD). SV2A levels can be investigated using positron emission tomography (PET) radioligands such as [ 11 C]UCB-J, [ 18 F]UCB-J, and [ 18 F]SynVesT-1. To compare the in vivo performance of the PET radioligands [ 18 F]UCB-J and [ 18 F]SynVesT-1 in terms of brain penetration, binding profile, and SV2A quantification, we here report a head-to-head study in a mouse model of HD. Dynamic µPET/CT scans (60 min) were acquired in 17-month-old heterozygous (HET, n = 20) zQ175DN and wild-type (WT, n = 19) mice. Brain time-activity curves and image-derived input function were extracted and kinetic modeling was performed using Logan and the two-tissue compartmental model (2TCM). Intra-animal comparison between both radioligands revealed significantly higher K 1 ( p < 0.01) but equal k 2 for [ 18 F]SynVesT-1 compared to [ 18 F]UCB-J. V T(IDIF) (Logan) quantification found significantly higher values for [ 18 F]SynVesT-1 compared to [ 18 F]UCB-J regardless of genotype (e.g. striatum WT: 22.4 ± 2.7 vs 18.6 ± 1.8 mL/cm 3 ). Regional analyses comparing the average V T(IDIF) between genotypes showed no significant differences; however, voxel-based V T(IDIF) analyses revealed significant SV2A alterations in several subregions of the brain for both radioligands. Overall, [ 18 F]SynVesT-1 and [ 18 F]UCB-J showed agreement across analyses, demonstrating the equal applicability of both radioligands for SV2A PET imaging.
Background: Motor performance declines with aging, yet how somatotopic subregions of the primary motor cortex (M1) and corticospinal tract (CST) show region-specific structural and functional changes during aging remains unclear. Methods: We analyzed T1- and T2-weighted MRI, multi-delay arterial spin labeling, and multi-shell diffusion data from 339 right-handed adults in the Human Connectome Project–Aging database. Measures included M1 cerebral blood flow (CBF), arterial transit time (ATT), intracortical myelin (T1/T2 ratio), and CST integrity. M1 was divided into face, upper-limb, and lower-limb subregions using mrGrad, and corresponding CST subdivisions were reconstructed. Results: Across age groups, CBF was highest in upper-limb M1 and lowest in lower-limb M1, while myelin content was highest in lower-limb regions of both M1 and CST. Aging was associated with prolonged ATT, reduced CBF, and altered T1/T2 ratio across all subregions, whereas the upper-limb CST showed relatively preserved microstructure. These imaging features of M1 and CST were linked to somatic motor performance. Conclusion: M1 and CST exhibit distinct somatotopic gradients in structure and function. Aging affects motor homunculus subregions and their pathways in region-specific ways. Multiparametric MRI has potential to characterize early motor decline and provides insights into neural mechanisms underlying somatotopic motor functions in older adults.
Combat sports provide a unique human model in which cerebral ischaemia-reperfusion stress, adaptive neuroprotection, and impact-induced neurodegenerative risk coexist. Across striking and grappling disciplines, exercise-induced metabolic and redox stress, repetitive head impacts and transient cerebral ischaemia-reperfusion during vascular neck restraints expose the brain to competing adaptive and injurious stimuli. Cerebral ischaemic preconditioning (cIPC) research demonstrates that brief, sublethal reductions in cerebral blood flow (CBF) activate a conserved hormetic programme involving modulation of oxidative-inflammatory-nitrosative stress (OXINOS), reduced glutamate excitotoxicity, mitochondrial stabilisation, anti-apoptotic and autophagic pathways, and metabolic reprogramming. These responses preserve glucose-and lactate-dependent bioenergetics, neurovascular unit integrity, and cognitive function. Repetitive sportive strangulations may engage cIPC-like mechanisms, potentially explaining elevated basal CBF reported in elite Brazilian jiu-jitsu athletes (~500 pre-syncopal exposures per year). In contrast, repetitive impacts and rotational shear in boxing and mixed martial arts initiate neurometabolic cascades marked by axonal injury, exaggerated OXINOS, mitochondrial dysfunction, and neurovascular disruption, promoting tau pathology associated with chronic traumatic encephalopathy. By integrating cerebral bioenergetics, hormesis, ischaemic tolerance and traumatic brain injury, this review positions combat sports as a translational model for defining cerebral resilience and the balance between adaptive neuroprotection and cumulative neurological risk.
Susceptibility alterations in deep gray matter (DGM) across clinical stages of cerebral small vessel disease (CSVD) remain unclear. In this case-control study, we used 7-Tesla magnetic resonance imaging quantitative susceptibility mapping (QSM) with source separation (APART-QSM) to characterize stage-related changes in normal controls, preclinical CSVD, and symptomatic CSVD. Compared with controls, CSVD showed increased QSM in the basal ganglia, particularly the putamen and globus pallidus, whereas small-magnitude QSM reductions were observed in selected thalamic and amygdalar subregions (all p < 0.05). Source separation revealed that basal ganglia abnormalities were mainly associated with increased paramagnetic components, whereas some thalamic alterations may involve increased diamagnetic components, suggesting distinct susceptibility contributions. Lower MoCA scores were associated with higher QSM and paramagnetic values in the globus pallidus, as well as higher diamagnetic values across the thalamus, putamen, and nucleus accumbens (all p < 0.05). Notably, right anterior globus pallidus QSM discriminated symptomatic CSVD from controls with the highest accuracy (AUC = 0.818). These findings reveal DGM susceptibility patterns associated with cognitive impairment, suggesting that 7 T QSM and susceptibility source separation may provide complementary information for early CSVD characterization and future longitudinal evaluation.
Cerebrovascular reactivity (CVR), a promising marker of neurovascular responsiveness, is commonly measured using blood-oxygenation-level-dependent magnetic resonance imaging (BOLD-MRI) during a vasoactive gas challenge. While CVR magnitude (vascular response strength) has been widely studied, CVR delay (response time) is comparatively underexplored yet may provide valuable insight into vascular dysfunction across several neurological conditions. We systematically reviewed publications assessing delay using gas-challenge BOLD-MRI up to October 2025, identifying 200 relevant papers. Only 44 (22%) papers investigated delay in detail; the remainder only applied delay correction to improve CVR magnitude accuracy. Findings in disease were mixed and often limited by small sample sizes and methodological differences. Hypercapnic stimuli, typically delivered via fixed-inspired or fixed-expired methods, were most commonly used. While cross-correlation was the most popular delay estimation method, several alternatives, including haemodynamic response function fitting and Fourier analysis, have been proposed, but systematic comparisons against standard delay estimation methods remain limited, especially in clinical populations. Our review highlights inconsistencies in delay measurement and interpretation, with delay mostly treated as a confounder rather than a meaningful physiological parameter. Greater methodological validation and harmonisation are needed to realise the potential of CVR delay as a novel biomarker of brain health and disease.
