Journal of Cerebral Blood Flow & Metabolism

Moderate hypoxia is increasingly recognized as a physiological driver of neuroprotection and neuroregeneration. In this first randomised, double-blind, controlled, four-arm trial, we demonstrate the cognitive and neuroplastic effects of cognitive training under moderate inspiratory hypoxia in humans. Healthy volunteers underwent three weeks of either cognitive or sham training under normobaric hypoxia (12% O2) or normoxia (20% O2) for 3.5 hours daily, six days per week. Participants were assessed at baseline, treatment completion, and one-month follow-up. The primary outcome was change in a broad cognitive composite score. Additional cognitive, blood-based, and neuroimaging outcomes were assessed, including measurement of the presynaptic protein SV2A with [11C]UCB-J positron emission tomography (PET) and neural activity through functional magnetic resonance imaging (fMRI). In total, 126 participants were randomised to hypoxia-cognitive training (H-CT: n=36), hypoxia-sham training (H-ST: n=30), normoxia- cognitive training (N-CT: n=30), or normoxia-sham training (N-ST: n=30). Intention-to-treat analyses showed no effect of H-CT relative to N-ST in the primary outcome at treatment completion (primary endpoint; treatment effect=0.11, 95% CI=[-0.06;0.28], p=0.19), but improvements emerged at follow-up (treatment effect=0.17, 95% CI=[0.01;0.34], p=0.04). N-CT induced transient improvement in the primary outcome at treatment completion (treatment effect=0.20, 95% CI=[0.02;0.38], p=0.03), which rendered non-significant at follow-up. Finally, H-ST showed no significant cognitive change relative to N-ST. Moderate hypoxia was safe and well-tolerated. Cognitive benefits were accompanied by decreased hippocampal presynaptic density measured with [11C]UCB-J PET. In conclusion, three weeks of H-CT can enhance cognition with associated effects on neuroplasticity, although with a delayed onset of effects on cognition.

Cerebral blood flow (CBF) is a quantitative metric for mapping perfusion. While the prototypical MRI approach arterial spin labelling (ASL) is well-validated in humans, the reproducibility of rodent ASL mapping remains poor, limiting translational impact. To address this gap, we used both newly acquired and analysis of previously published data to illustrate biological and physical sources of variation in CBF measured with ASL. Via a meta-analysis, we quantified the variation in CBF reported from the cortex of healthy rodents. A total of 23 mouse studies (343 data points) and 5 rat studies (41 data points) met the inclusion criteria. We demonstrate that reported CBF values exhibit a broad variability (50-400 ml/100g/min) driven primarily by experimental confounds rather than physiological differences. Our meta-analysis explores which factors cause variance in perfusion rates measured. Our experimental data highlight biological factors, particularly the choice of anaesthesia (e.g., isoflurane vs. medetomidine) and strain variations, that alter baseline CBF. Our work, reflecting both state-of-the-art and conventional practice in preclinical imaging, highlights the need to account for multiple sources of variability. Establishing community guidelines for rigorous ASL calibration and physiological monitoring will support improved study design and accelerate translational alignment between rodent and human perfusion measurements.

BackgroundIntracranial steno-occlusive disease (SOD) assessment benefits from hemodynamic imaging, but comprehensive evaluation often relies on contrast- or radiation-based techniques. Arterial spin labeling (ASL) provides a non-invasive alternative for quantifying tissue-level perfusion and cerebrovascular reactivity, yet does not capture upstream arterial flow dynamics. As a result, non-invasive assessment of macrovascular hemodynamics for SOD remains limited. This study evaluates whether quantitative 4D-MRA provides complementary arterial information beyond established ASL-derived metrics. MethodsTwelve SOD patients (7 women; age 42.3{+/-}25.8 years) underwent multi-delay ASL and 4D-MRA before and after acetazolamide. Cerebrovascular reactivity (CVR), arterial transit time (ATT), macrovascular ATT (mATT), and labeled blood volume (LBV) were quantified. Associations and vasodilatory responses were assessed using linear mixed-effects models. ResultsAt baseline, mATT correlated with ATT ({beta}=0.66{+/-}0.08, p<0.001). Both decreased following acetazolamide (mATT: 1.07{+/-}0.03s to 1.01{+/-}0.03s, p=0.029; ATT: 1.63{+/-}0.07s to 1.40{+/-}0.07s, p<0.001). However, changes in mATT and ATT were not associated with CVR. In contrast, CVR was positively associated with {Delta}LBV ({beta}=8.84, SE=2.43, p=0.01). Case analyses further demonstrated artery-level delayed inflow and vascular steal. ConclusionQuantitative 4D-MRA provides complementary macrovascular information to ASL in SOD. {Delta}LBV more consistently reflects cerebrovascular reactivity than transit-based metrics and is sensitive to artery-level delayed inflow and vascular steal. The local Medical Ethical Review Committee declared that the Medical Research Involving Human Subjects Act (WMO) did not apply (internal trial nr. 21-406).

The white matter (WM) cerebrovascular response remains poorly understood compared with grey matter (GM), partly due to technical challenges in perfusion quantification. Previous hypercapnia studies using BOLD MRI have reported reduced or negative WM cerebrovascular reactivity, but whether these findings reflect true reductions in cerebral blood flow (CBF) remains unclear. We used multi-delay pseudo-continuous arterial spin labeling (pCASL) to quantify hypercapnia-induced CBF changes ({Delta}CBF) while accounting for regional variability in arterial transit time. Twenty-five healthy young adults underwent MRI during normocapnia and hypercapnia (inhalation of a 4% CO2 gas mixture). Hypercapnia induced robust positive {Delta}CBF in cortical GM (26.7 {+/-} 13.5%), superficial WM (17.2 {+/-} 12.6%), periventricular regions (13.6 {+/-} 10.6%), and subcortical GM (25.7 {+/-} 14.1%) (all p < 0.0001). In contrast, deep WM exhibited a near-zero group-mean CBF response (1.0 {+/-} 8.9%, p = 0.57), with 10 of 25 participants demonstrating negative {Delta}CBF. Negative responses were consistently localized to the corona radiata, centrum semiovale, and optic radiation. Quality-control analyses showed that deep-WM {Delta}CBF estimates are robust at our long post-labeling delays, supporting the reliability of these findings. Across tissue compartments, higher baseline CBF was associated with reduced hypercapnic responsiveness, and deep-WM responses were strongly coupled with cortical GM responses across individuals. These results demonstrate that hypercapnia-induced perfusion responses are highly heterogeneous across tissue depths and provide evidence that negative CBF responses can occur in healthy deep WM. The findings challenge the assumption of uniformly positive cerebrovascular responses during hypercapnia and support a potential role for flow redistribution arising from regional differences in vascular resistance and reserve capacity.

Accurate assessment of cerebral hemodynamics impairment traditionally relies on arterial metrics, yet often overlooks venous drainage and arteriovenous dynamics, thereby limiting the evaluation of ischemia-induced microvascular dysfunction. To address this limitation, we implemented a signal-averaging framework, combined with co-fluctuation analysis, to extract predominantly arterial and venous hemodynamic signals and construct a dynamic arteriovenous co-fluctuation index that quantifies frame-by-frame coordination between arterial inflow and venous outflow activity. This time-resolved index enables spatial characterization of large-scale cortical arteriovenous coordination beyond conventional static correlation-based analyses. Comparative analyses between healthy controls and acute ischemic stroke mice demonstrated that the arteriovenous co-fluctuation index sensitively detects disruption of vascular coordination, revealing a slower state transition that occurs alongside distinct temporal abnormalities and regional heterogeneity between ischemic core and penumbral regions. These findings underscore the utility of arteriovenous coordination as a sensitive indicator of microcirculatory dysfunction, offering a practical analytical tool for assessing stroke-induced microvascular impairment.

PurposeTo apply voxel-wise tracer kinetic model selection, characterise the spatial distribution of best-fitting models across the brain, and evaluate whether model selection improves sensitivity for differentiating normal-appearing tissue from pathological tissue compared to the Patlak model. MethodsExtended Tofts, Patlak, and intravascular models were fit to DCE-MRI data from stroke survivors and controls, as well as simulated data. The best-fitting model was chosen for each voxel using the Akaike Information Criterion, and model selection Ktrans (estimates from the best-fitting model for each voxel) compared to Patlak model Ktrans. ResultsIn simulated data, the Extended Tofts model was best-fitting at Ktrans>10-3 min-1, where the Patlak model systematically underestimated Ktrans. Patlak was optimal at Ktrans between 10-4-10-3 min-1, where Extended Tofts estimates had greater variability. The intravascular model was selected for Ktrans[~]10-4 min-1. The Patlak model was chosen in most control voxels. In chronic stroke, the Extended Tofts model was preferred in most cortical and white matter hyperintensity voxels, while the Patlak model was selected in most deep grey matter and normal-appearing white matter voxels. Model selection Ktrans estimates were significantly greater than Patlak estimates in the cortex and white matter hyperintensities, with greater inter-patient variability, likely reflecting biological variability in blood-brain barrier leakage resulting from stroke. ConclusionVoxel-wise model selection may provide more accurate estimates of a wider range of Ktrans values than any single model, revealing greater differences between normal and pathological tissue and offering a more sensitive and physiologically appropriate framework for DCE-MRI analysis of blood-brain barrier dysfunction.

IntroductionChemogenetic tools such as Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) provide a powerful means to causally manipulate defined neuronal populations in vivo. While chemogenetic fMRI studies have consistently demonstrated robust hemodynamic responses following circuit perturbation, considerably less is known about the accompanying metabolic consequences. Functional magnetic resonance spectroscopy (fMRS) offers the potential to probe these neurochemical processes, yet the relationship between hemodynamic and metabolic responses remains poorly understood. Here, we combined chemogenetics, pharmacological fMRI (ph-fMRI), and proton magnetic resonance spectroscopy (1H-MRS/fMRS) at 7 T to investigate the temporal evolution of metabolic and hemodynamic responses in the rat motor cortex. MethodsFemale Fischer rats received viral injections in the motor cortex to express either a pan-neuronal hM3D(Gq) DREADD construct (hSyn-hM3Dq) or an interneuron-targeted construct (hDlx-hM3Dq). Ph-fMRI, fMRS, and 1H-MRS measurements were performed before, during, and following systemic administration of clozapine-N-oxide (CNO, 1 mg/kg). Functional MRS was acquired during the acute response phase (0-60 min post-injection), while conventional 1H-MRS measurements were obtained at a delayed time point (70 min post-injection). ResultsChemogenetic modulation produced robust and opposing hemodynamic responses. Pan-neuronal activation elicited focal positive BOLD responses (+3.5 {+/-} 1.5%), whereas interneuron-targeted activation generated significant negative BOLD responses (-3.3 {+/-} 0.8%). In contrast, acute fMRS measurements revealed no significant changes in Glx or GABA concentrations during the first hour following CNO administration, despite the presence of strong hemodynamic effects. However, delayed metabolic alterations were detected 70 min after CNO administration. Animals expressing the pan-neuronal construct exhibited significant increases in GABA (+14.4%) and total choline compounds (+57.8%), whereas interneuron-targeted animals displayed reductions in several metabolites, including Glx (-15.6%), total NAA (-16.9%), glucose (-25.9%), and total creatine (-25.4%). ConclusionChemogenetic perturbation of cortical circuits produced robust hemodynamic responses but more subtle and temporally complex metabolic effects. The absence of detectable acute changes in Glx and GABA despite strong BOLD responses, together with the emergence of delayed neurochemical alterations, highlights the challenges of interpreting metabolic signals in relation to circuit activity.

Cerebral small vessel disease and neurodegenerative disorders have been associated with increased cerebrovascular pulsatility. Recently, BOLD fMRI-based methods have emerged for assessing pulsatility, however their interpretability is limited because the relation between estimated pulsatility indices (PI) and vascular anatomy and physiology remains poorly understood. To improve interpretability, we introduce a cardiac-specific BOLD fMRI- based PI, investigate its relationship to the cortical vasculature, and validate its sensitivity by introducing the known physiological vascular modulation of hypercapnia. Using high-resolution 7T BOLD fMRI with gradient-echo (GE) and spin-echo (SE) sequences, we disentangled macro- and microvascular contributions to the PI and quantified it across cortical depth. PI maps revealed anatomically plausible patterns, with elevated GE-PI near large veins and in white matter while SE-PI remained largely constant across cortical depth. GE-PI decreased during hypercapnia consistent with altered vascular tone, SE-PI on the other hand did not. PI correlated with cerebrovascular reactivity and venous blood volume suggesting sensitivity to vascular density and vessel mechanics. Our findings demonstrate that BOLD-derived PI provides a spatially and physiologically specific measure of vascular pulsatility. The BOLD fMRI-based PI method is readily applicable to existing datasets and has potential for assessing potential microvascular damage in cerebrovascular and neurodegenerative disease.

PurposeLeft ventricular hypertrophy (LVH) is a major complication of chronic hypertension and an independent risk factor for cardiovascular morbidity and mortality. There are currently no clinically validated markers available to identify hypertensive individuals at risk for developing LVH. In hearts of hypertensive rats, we previously described metabolic changes that precede LVH development, including in branched-chain amino acid (BCAA) metabolism. This study investigated whether cardiac leucine uptake, measured with dynamic 5-[18F]fluoroleucine positron emission tomography-computed tomography ([18F]FLE-PET/CT), was impaired and could serve as an in vivo marker for hypertension-induced LVH development. ProceduresWe synthesized [18F]FLE following established radiochemistry protocols and performed dynamic [18F]FLE-PET/CT imaging in 3-month-old spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) control rats (n = 4 per group). Cardiac magnetic resonance (CMR) imaging was conducted on the same animals for structural co-registration. A dual-output reversible two-tissue compartment model with spill-over (SP) and partial volume (PV) corrections was developed to quantify the first-pass rate constant (K1) and total distribution volume (Vt = K1/k2) for [18F]FLE. Protein expression of L-type amino acid transporter 1 (LAT1) and branched-chain keto acid dehydrogenase (BCKDH) phosphorylation status were assessed by immunoblotting of isolated heart tissue. ResultsSHR demonstrated markedly lower first-pass leucine uptake rates (K1) and total distribution volumes (Vt) compared with WKY rats, consistent with reduced cardiac BCAA uptake. Concurrently, LAT1 (SLC7A5) expression was significantly reduced in SHR hearts compatible with decreased leucine uptake. Elevated BCKDH phosphorylation at Ser293 in SHR hearts indicated diminished BCKDH enzymatic activity and impaired BCAA catabolism. ConclusionsDynamic cardiac [18F]FLE-PET imaging successfully detects decreased leucine uptake in hypertensive rat hearts at 3 months of age, before LVH is established at 5 months. Reduced cardiac leucine uptake may thus serve as a surrogate marker for impaired cardiac BCAA metabolism and early in vivo indicator of cardiometabolic dysfunction that precedes LVH. The imaging approach holds translational potential for identifying hypertensive patients at risk for LVH progression.

Recent advances in neurophysiology highlighted the potential of high temporal resolution in Blood-Oxygen Level Dependent (BOLD) functional MRI (fMRI), although it is not yet standard practice. We demonstrated that fast BOLD fMRI can detect single-subject, single-stimulus visually evoked responses to brief stimuli at 3T. We used fast fMRI in patients with Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL), a genetic form of cerebral small vessel disease (cSVD). Using 2- and 10-second visual stimuli, we probed different neurovascular coupling regimes and showed that different regions of interest detect different facets of vascular dynamics. CADASIL patients showed significant changes in the amplitude and timing of the BOLD response, indicating early-age neurovascular impairment unrelated to anatomical lesions, and providing strong discriminative and generalization performance. These findings resolve prior inconsistencies in fMRI studies of CADASIL, supporting the use of fast fMRI to develop non-invasive biomarkers for cSVD and other neurodegenerative disorders.

Background: Mu-opioid receptors (MORs) are expressed throughout the body including in the brain and gastrointestinal (GI) tract. Total-body PET imaging of the brain and GI tract offers a promising approach for cross-sectional in vivo evaluation of the MOR brain-GI axis. However, intestinal motility and bladder filling introduce motion throughout the GI tract over the scan window. Here we establish analysis methodology to account for motion for dynamic imaging of the brain-GI axis, to further characterize peripheral MORs throughout the body and provide a framework for semi-automatic total-body PET modeling. Methods: 4 subjects underwent 90-min dynamic [11C]-carfentanil (cfn) total-body PET acquisitions at baseline, after intravenous naloxone (central antagonist) administration, and after orally administered loperamide (peripheral agonist and P-glycoprotein substrate). Thalamic MOR availability was measured using the Logan reference tissue model. Using CT-based segmentation, the GI tract was subdivided into anatomical segments, in addition to other peripheral organs (e.g., liver, psoas muscle). Frame-by-frame semi-automatic motion correction was performed with three distinct reference frames (11-14 min post-injection, p.i., 35-40 min p.i., and 85-90 min p.i.). The performance of these three were compared to manual correction. Compartment modeling and Logan graphical analysis were performed to estimate relevant kinetic parameters (K1, VT, VTLogan). Results: Across the 4 subjects and regions, kinetic parameter estimates were highly correlated (r>0.7) for K1, VT and VT Logan when comparing semi-automatic (reference frame at 35-40 min p.i.) and manual correction. With semi-automatic motion correction, graphical-based estimation of VTLogan in the gastrointestinal tract was significantly decreased with loperamide relative to baseline (p<0.05). As expected, naloxone decreased brain thalamic MOR availability but loperamide did not. Conclusions: With semi-automatic motion correction and [11C]-cfn total-body PET, pharmacologic perturbations of MOR brain-GI axis can be quantitatively characterized, reducing the burden of image analysis for these studies.

BackgroundMagnetic resonance imaging (MRI) is critical for acute stroke triage, but time-consuming, and often requires contrast injection for perfusion imaging. This study aimed to synthesize T-map perfusion maps from routinely available, non-contrast DWI and FLAIR using deep generative models. We hypothesized that relevant perfusion information could be inferred from these modalities to streamline imaging and reduce reliance on dynamic susceptibility contrast perfusion. MethodsAcute MRI data from 355 patients with anterior circulation stroke, including dynamic susceptibility contrast perfusion, were retrospectively collected from two European centers (Heidelberg: 2010-2018; Bordeaux: 2021-2022). Six versions of a denoising diffusion probabilistic model (DDPM) and a GAN architecture were trained to generate synthetic T-max perfusion maps from DWI, FLAIR, and infarct core mask as inputs. Performance was assessed by comparing synthetic and ground truth T-max maps using image similarity metrics. Regions with T-max >6s were compared using Dice coefficients, and mismatch volume distributions were analyzed. An ablation study quantified the contribution of each input. ResultsThe best performance was achieved by a DDPM with a 2.5D architecture using DWI, FLAIR, infarct core mask, and a perfusion-weighted loss function. It produced synthetic perfusion T-max maps with high similarity to ground truth under 110 seconds. The model showed strong spatial overlap for T-max >6s regions in internal validation (average Dice = 0.82, SD = 0.08), and external validation average (Dice 0.59, SD = 0.13), respectively. Synthetic maps closely matched ground-truth mismatch distributions, capturing key perfusion patterns. The infarct core mask played a critical role in model performance, alongside DWI and FLAIR inputs. ConclusionsWe propose a non-invasive, scalable framework to generate synthetic T-max perfusion maps from non-contrast MRI. This approach could expand access to perfusion data in acute stroke, shorten imaging protocols, and accelerate treatment decisions by eliminating the need for contrast-enhanced acquisition. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/684079v2_ufig1.gif" ALT="Figure 1"> View larger version (94K): org.highwire.dtl.DTLVardef@164235forg.highwire.dtl.DTLVardef@14e5489org.highwire.dtl.DTLVardef@190214eorg.highwire.dtl.DTLVardef@17a9e3a_HPS_FORMAT_FIGEXP M_FIG C_FIG

Hypoxia-targeted BOLD MRI is a novel technique, which probes oxygenation physiology in response to a controlled transient hypoxia stimulus. In glioblastoma, the signal response is spatially and temporally heterogeneous. We developed a voxel-wise temporal decomposition framework for hypoxia-targeted BOLD MRI that separates the arrival of responses, transition phases, and steady state during controlled isocapnic hypoxia. Twenty healthy controls underwent 3-T BOLD MRI during a double hypoxic step challenge to establish a normative reference. Three patients with newly diagnosed glioblastoma were included as proof-of-concept cases. For each voxel, we estimated response arrival delay (Delaycorr), delay to plateau, delay to return and an O2-normalized steady-state response (HypoxiaSS). Healthy-control maps were used to construct a voxel-wise normative atlas and, for HypoxiaSS, a global-response-adjusted model for patient deviation mapping. In healthy controls, HypoxiaSS showed lower supratentorial between-subject variabilitythan both whole-stimulus comparators (coefficient of variation: 1.77 versus 2.36 for Hypoxiaavg) and higher voxel-level step-to-step agreement (ICC(2,1): median 0.951 versus 0.792 for Hypoxiaavg). Whole-stimulus averaging exhibited a systematic step-2 signal amplification present in 19 of 20 subjects, which was absent from HypoxiaSS. Asingle global response scalar explained a median 72.5% of voxel-wise between-subject variance in HypoxiaSS. In proof-of-concept patient analyses, G-adjusted HypoxiaSS deviation maps and timing maps identified spatially coherentabnormalities that were partly complementary and extended beyond conventional MRI-defined lesion margins.Temporal decomposition improves the stability and interpretability of hypoxia-targeted BOLD MRI and provides a practical framework for population-referenced physiological mapping and atlas-based deviation mapping in glioblastoma.

Ultrafast ultrasound offers a unique route to cross-scale neurovascular phenotyping by integrating functional ultrasound (fUS), ultrasound localization microscopy (ULM), and functional ULM (fULM). Yet the baseline variability, longitudinal stability, and biological safety of such multimodal imaging in awake animals remain insufficiently defined, limiting its use for detecting subtle disease-associated neurovascular changes. Here, an awake longitudinal fUS-ULM-fULM framework is established and validated in mice over five months. Structural vascularity, microvascular flow velocity, mesoscale hemodynamic responses, and microvascular functional responses are repeatedly quantified in the same animals during monthly imaging sessions. Across all metrics, no significant longitudinal drift is detected (p > 0.60). Structural and flow-derived measures are markedly more reproducible than functional readouts, with within-subject coefficients of variation of 5.1% for mean flow velocity and 7.3% for vascularity, compared with 25.0% for fUS-derived cerebral blood volume responses and 53.2% for fULM-derived microvascular functional responses. Mean flow velocity shows the strongest longitudinal consistency (ICC = 0.70) and the lowest detection threshold. Behavioral testing and GFAP/Iba1 staining further reveal no memory impairment or chronic neuroinflammation. This study defines quantitative baselines, reproducibility limits, and safety evidence for awake cross-scale ultrasound imaging, providing a reference framework for longitudinal neurovascular phenotyping in preclinical disease models.

BackgroundApolipoprotein E (APOE) has been implicated in blood-brain barrier (BBB) dysfunction and may influence ischaemic cerebrovascular disease and cerebral small-vessel disease (cSVD). This study examined associations between APOE genotype, BBB permeability, and infarct distribution in patients with mild ischemic stroke. MethodsWe recruited patients with mild ischemic stroke who underwent structural and dynamic contrast-enhanced MRI (DCE-MRI) and APOE genotyping. Infarct type and location, white matter hyperintensities (WMH), and perivascular spaces (PVS) were assessed. BBB-related metrics were quantified using fractional plasma volume (vP) and permeability-surface area product (PS) across five brain regions of interest: deep grey matter (DGM), hippocampus, thalamus, normal-appearing white matter (NAWM), and WMH. Associations between genotype, BBB metrics, vascular risk factors, and age were evaluated using linear mixed-effects models. Binary logistic regression was also applied to assess the association between APOE status and infarct location by vascular territory (anterior vs posterior circulation). ResultsAmong 147 patients with APOE genotype and BBB measures, APOE4 carriers (n=44) demonstrated a greater proportion of posterior circulation infarcts than E3/E3 individuals (n=80; 56.4% versus 32.9%), including higher frequencies of posterior cerebral artery cortical, posterior borderzone, and thalamic infarcts. Mean PS and vP did not differ significantly by genotype. Increasing age was associated with lower PS across multiple regions and lower vP in WMH, while higher vascular risk burden was associated with lower vP in NAWM and WMH. Inclusion of regional BBB metrics did not substantially alter APOE4 effect estimates in infarct-location models. ConclusionsAPOE4 carriers showed a posterior-predominant infarct distribution despite similar BBB permeability and vascularity measures. Age and vascular risk burden were more strongly associated with BBB-related imaging metrics than APOE genotype. These findings add to evidence suggesting that APOE genotype may influence regional cerebrovascular vulnerability and that this effect is unlikely to be fully explained by DCE-MRI-derived measures of BBB permeability and vascularity alone.

BackgroundPeripheral microvascular abnormalities may reflect systemic microvascular dysfunction relevant to cerebral small vessel disease (cSVD), yet their relationship to individual neuroimaging markers and overall cSVD burden remains unclear. We evaluated whether abnormalities in nailfold capillaroscopy (NFC) are associated with specific cSVD markers and with the total cSVD score in a population-based cohort. MethodsAtahualpa residents aged [&ge;]60 years underwent NFC and brain MRI. Capillary tortuosities, dilatations, density, and megacapillaries were quantified using automated software with expert validation. Neuroimaging markers included white matter hyperintensities (WMH), lacunes, deep cerebral microbleeds (CMB), and enlarged basal ganglia perivascular spaces (BG-PVS). Logistic regression models assessed associations between NFC abnormalities and cSVD markers. Poisson regression was used to model the total cSVD score. All models were adjusted for demographics, educational attainment, and cardiovascular risk factors. ResultsAmong 289 participants (mean age 71.3 {+/-} 7.5 years; 51% women), lower capillary density was independently associated with CMB (OR: 0.70; 95% C.I.: 0.51-0.96) and lacunes (OR: 0.67; 95% C.I.: 0.50-0.91), with a borderline association for WMH (p=0.062). Megacapillaries were independently associated with moderate-to-severe WMH (OR: 5.01; 95% C.I.: 1.42-17.68). Tortuosities and dilatations showed no significant associations. Higher capillary density was inversely associated with the total cSVD score ({beta}: -0.179; 95% C.I.: -0.283 to -0.075). ConclusionsReduced capillary density and megacapillaries track with the burden of cSVD. NFC may provide a noninvasive window into cerebral microvascular health and could inform risk stratification for cSVD progression and related outcomes.

Background The ischemic penumbra, a metabolically compromised yet potentially salvageable region surrounding the ischemic core, is a prime target for acute stroke intervention. Yet an objective molecular definition of the penumbra, particularly during the earliest stages of ischemia, remains lacking. Methods and Results We applied principal component analysis (PCA) followed by k-means clustering to high-resolution mass spectrometry imaging data covering multiple metabolic pathways to identify a metabolically defined penumbra in a mouse model of hyperacute stroke (45 min middle cerebral artery occlusion, MCAO). Targeted spatial metabolomic profiling by matrix-assisted laser desorption/ionization (MALDI) and desorption electrospray ionization (DESI) reveals a distinct penumbral metabolic profile, marked by relative preservation of high-energy phosphates, comparable lactate accumulation, and reduced succinate accumulation relative to the core. Spatial transcriptomics revealed selective induction of immediate-early genes, including Npas4, Fos and Junb, within the penumbra. Consistently, imaging mass cytometry shows enrichment of phospho-histone H3 (pHH3) within the penumbra, suggesting a chromatin-associated response potentially linked to immediate-early gene activation. Conclusion Together, these findings provide a multimodal molecular atlas of the hyperacute metabolically defined penumbra and reveal molecular features that facilitates its identification and inform future therapeutic strategies.

IntroductionCoronary artery disease (CAD) increases the risk of cerebrovascular events, yet early brain injury in this population remains poorly characterized. White matter hyperintensities (WMHs), a biomarker of cerebrovascular lesions, are prevalent in CAD and are linked to risk of stroke. Beyond total burden, spatial distribution of WMHs carries pathological significance and is critical for understanding CAD-related injury. While clinical outcomes including coronary revascularization procedure and myocardial infarction influence CAD prognosis, their impact on WMH burden remains unclear. MethodsThis study investigated regional WMH burden in CAD and its relationship with clinical characteristics. 82 adults over 50 years participated, including 44 individuals with CAD and 38 controls. WMHs were segmented from fluid attenuated inversion recovery and T1-weighted MRI and categorized as total, periventricular, deep, and superficial regions. History of myocardial infarction and coronary revascularization (coronary artery bypass grafting (CABG) and percutaneous coronary intervention (PCI)), was obtained from medical files. ResultsIndividuals with CAD exhibited higher total, periventricular, and deep WMH volumes than controls. Participants who underwent CABG had higher superficial WMH volumes than those with PCI, suggesting greater disease severity influences WMH burden. ConclusionCAD is characterized by a distinct pattern of cerebrovascular vulnerability, with revascularization procedures influencing WMH burden

BackgroundPreexisting factors are among the strongest predictors of recovery following traumatic brain injury (TBI), with chronic stress closely associated with permanent disability and worse long-term outcomes. While chronic cerebrovascular dysfunction is linked to these poor trajectories, as impaired blood flow regulation drives secondary disease progression, the mechanisms regulating this vascular failure remain incompletely understood. Crucially, how premorbid chronic stress and TBI disrupt the fundamental coordination of the cerebrovascular network post-injury remains unknown. MethodsTo elucidate this coordination at rest and in response to increased neuronal activity, we used a model of three repeated moderate closed cortical impacts comorbid with chronic stress induced by social isolation (SI) post-weaning. Our previously developed vascular analysis pipeline (NOVAS3D) was employed to estimate changes in vascular radii across cerebrovasculature proximal to neuronal activation. Arteries and veins were annotated in the imaged volumes to allow for blood flow simulations. ResultsUsing graph-based network analysis, we demonstrate that TBI, when compounded with chronic stress, critically disrupts the long-range coordination of the capillary network. Specifically, the functional coordination of radius changes between nearby, non-adjacent capillaries was reduced by 40{+/-}20% in TBI+SI mice relative to controls. Consequently, simulations estimated that the vascular networks in TBI+SI mice experienced a 68{+/-}7% reduction in arterial red blood cell velocity (VRBC) responses to neuronal activation. These network-wide impairments were fundamentally driven by severely blunted vessel reactivity, including a 28{+/-}7% decrease in the magnitude of arteriolar dilations and a 47{+/-}7% decrease in the magnitude of arteriolar constrictions. ConclusionThese findings provide a mechanistic foundation for worse clinical outcomes seen in TBI patients with comorbid chronic stress, identifying arteriolar reactivity and long-range capillary coordination as critical therapeutic targets to mitigate secondary injury and improve long-term recovery.

Trimethylamine n-oxide (TMAO) is a plasma metabolite linked to adverse cardiometabolic health with complex regulation involving diet, sex, and host genetics. We explored the role of these factors in the genetic regulation of TMAO by performing a primary-level meta-analysis in 1,482 female and male Diversity Outbred (DO) mice from five distinct studies conducted in various regions of the United States. We identified a quantitative trait locus (QTL) associated with TMAO concentration at [~]86 megabase pairs on mouse chromosome 12 with a highly significant LOD score of 67.67. Alleles at the chromosome 12 QTL inherited from the Cast/EiJ (CAST) and PWK/PhJ (PWK) mouse strains primarily drove the association with reduced TMAO concentrations. The chromosome 12 QTL remained significant in sex-stratified analyses and the mode of inheritance appeared additive; furthermore, the QTL was regulated by sex-by-genotype and sex-by-diet interactions. Using a CAST/EiJ X C57BL/6J F2 cross, positional candidates were prioritized by eQTL analysis. Further analysis in a study utilizing the eight DO founding strains identified that Acyp1 was differentially expressed in hepatic tissue from CAST mice, prompting investigation into its genetic regulation. Acyp1 demonstrated relevant cis- and trans-regulation and was significantly correlated with TMAO and hepatic Fmo3. However, no significant relationships between Acyp1 and TMAO were identified in mice inactivated for Acyp1 or with AAV overexpression of Acyp1 in the liver. Genes within the chromosome 12 QTL have synteny with humans and may translate to the genetic regulation of human plasma TMAO concentrations and atherosclerosis. Author SummaryWe explored the roles of diet, sex, and genetics on the regulation of fasting plasma trimethylamine n-oxide (TMAO) concentration by performing a meta-analysis in 1,482 female and male Diversity Outbred (DO) mice from five unique studies. We identified a QTL associated with TMAO concentration on chromosome 12 at [~]86 mega base pair (Mb) with a highly significant LOD score of 67.67. The locus is modified by both sex and diet.