Biology subjects

Moro, M. A.

Publications and source records attributed to Moro, M. A..

8 recordsLinked to original sources

bioRxiv2026

Microglial AhR Drives Sex-Biased Amyloid Pathology

Microglia integrate local and systemic signals that can modify their response to amyloid-{beta} (A{beta}), but the molecular pathways connecting these signals to Alzheimer's disease (AD) pathology remain incompletely understood. Here, we identify the aryl hydrocarbon receptor (AhR), a sensor of microbiota- and host-derived metabolites, as a microglial regulator of amyloid pathology. Sustained administration of the AhR agonist indoxyl-3-sulfate (I3S) exacerbated cortical A{beta} deposition and plaque-associated neuritic damage in APPNL-F mice. Conversely, constitutive AhR deficiency reduced amyloid burden, promoted plaque compaction, and preserved behavioural performance, whereas inducible deletion of AhR in microglia was sufficient to reduce plaque accumulation. Single-cell RNA sequencing revealed that AhR loss reprogrammed microglia toward phagolysosomal and A{beta}-recognition states and enhanced microglial A{beta} uptake, with markedly stronger effects in females. APPNL-F mice also exhibited sex-dependent remodelling of the gut microbiota and tryptophan-derived metabolites. Circulating indole-3-aldehyde (IAld) robustly activated AhR and was associated with cortical amyloid pathology. AhR-activating bioactivity was increased in mouse serum, cortex and faecal extracts and was higher in serum from the COGNIBIO12 analytical subcohort than in independently recruited cognitively unimpaired H2H participants. Among amyloid-positive patients, higher serum AhR bioactivity was associated with lower CSF A{beta}42 concentrations. Together, these findings identify microglial AhR as a metabolically responsive regulator linking systemic ligand availability, biological sex, and microglial control of amyloid pathology.

immunology↗

bioRxiv2026

ABERRANT HIPPOCAMPAL NEUROGENESIS IS A CONSERVED RESPONSE TO STROKE IN MICE: A MULTI-CENTER MULTIMODEL STUDY

BackgroundAdult hippocampal neurogenesis is markedly altered after cerebral ischemia. Although stroke increases the production of newborn neurons, many of these cells display aberrant morphological and positional features that impair their functional integration and contribute to long-term cognitive decline. Given the clinical heterogeneity of ischemic stroke and the persistent translational failures of preclinical approaches relying on single-model studies it remains unknown whether post-stroke neurogenic alterations are conserved across different experimental paradigms. This study aimed to define common and model-specific features of hippocampal neurogenesis across complementary focal ischemia models. MethodsWe performed a multi-center, multimodel analysis within the STROKE-IMPaCT consortium using permanent and transient middle cerebral artery occlusion (MCAO) paradigms (MCAO via ligation or cauterization under normoxic (dMCAO) or hypoxic conditions (dMCAO+Hypoxia); and filament-based tMCAO across six international sites. Brains from adult C57BL/6J mice were collected 3 days, 7 days, or 2 months after ischemia, sham, or naive conditions. Hippocampal cell proliferation (Ki67) and neuroblast density (DCX) were quantified, and the morphological maturation of newborn neurons was evaluated using high-resolution analyses of dendritic architecture and somatodendritic polarity. All analyses were performed blind to experimental group. ResultsAcross all stroke models, ischemia induced a robust bilateral increase in hippocampal cell proliferation, most pronounced at 3 days and still elevated at 7 days, with levels returning to baseline by 2 months. Neuroblast density was similarly increased at 7 days, particularly in the ipsilateral hippocampus, but normalized by 2 months. Despite recovery in cell number, long-term morphological analysis revealed a consistent reduction in apical dendrite length and a higher proportion of neurons exhibiting aberrant features including ectopic localization, multipolar or inverted polarity, and abnormal lateral growth across all models. These abnormalities were observed both when pooling data across sites and when analyzing each model or center individually. ConclusionsIschemia induces an early, transient increase in hippocampal neurogenesis across diverse stroke paradigms, but the newborn neurons generated after stroke consistently display maladaptive morphological features. These cross-model, cross-site abnormalities indicate that aberrant hippocampal neurogenesis represents a robust hallmark of post-stroke pathology within the investigated species, independent of ischemia type or surgical approach, despite known differences in the spatial distribution of primary injury across experimental stroke models. Our findings support the concept that maladaptive neurogenesis may contribute to chronic post-stroke cognitive impairment and underscore the need to consider the quality not only the quantity of newborn neurons when developing therapeutic strategies.

animal behavior and cognition↗

bioRxiv2025

Does Infarct Size Influence Gut Barrier Integrity and Bacterial Translocation after Experimental Stroke?

BackgroundIschemic stroke (IS) triggers brain injury and systemic changes, including gut dysbiosis, intestinal barrier dysfunction (IBD), and bacterial translocation (BT). Although larger infarcts are associated with higher infection risk, it is unclear whether lesion size directly influences gut barrier integrity or bacterial dissemination. MethodsMale C57BL/6 mice underwent permanent middle cerebral artery occlusion (MCAO) proximally or distally to generate large or small infarcts. Seventy-two hours post-ischemia, infarct volume was measured by MRI, and BT was assessed in mesenteric lymph nodes, liver, spleen, and lungs. ZO-1 and MMP9 expression were used to evaluate intestinal barrier integrity. Peripheral and central inflammation were assessed by flow cytometry and immunofluorescence. ResultsProximal MCAO produced larger infarcts than distal MCAO. The proportion of animals exhibiting BT was lower in distal MCAO, but this difference was not statistically significant. ZO-1 expression did not differ between groups, while MMP9 was increased only in animals with BT, independent of infarct size. BT was associated with more pronounced lymphopenia and enhanced microglial activation and T-cell infiltration in the brain. The composition of translocated bacteria was similar across groups. ConclusionsInfarct size alone does not determine IBD or BT, although BT is linked to intestinal and cerebral inflammation. This study evaluates for the first time the effect of lesion magnitude on IBD and BT, highlighting the complex interplay between cerebral injury and gut-systemic interactions.

neuroscience↗

bioRxiv2025

Sub-strain-Dependent Differences in Gut Barrier Permeability, Bacterial Translocation and Post-Stroke Inflammation in Wistar Rats

BackgroundStroke induces profound neuroinflammation and systemic immune dysregulation, including disturbances in gut homeostasis. Experimental evidence suggests that intestinal barrier permeability (IBP) and bacterial translocation (BT) critically influence stroke outcomes. However, biological variability among commonly used rodent sub-strains has received limited attention. MethodsIn this pilot study, we compared post-stroke immune responses in two Wistar rat sub-strains obtained from different suppliers: RccHan (Envigo) and RjHan (Janvier). Following transient middle cerebral artery occlusion, animals were assessed 72 hours later and stratified according to the presence or absence of BT. Immune cell populations in blood and bone marrow were analyzed by flow cytometry, and leukocyte infiltration into ischemic brain tissue was quantified by immunohistochemistry. ResultsBoth sub-strains developed significant infarcts and neurological deficits. RccHan rats displayed larger infarct volumes and more extensive BT across multiple organs. In contrast, RjHan rats exhibited BT mainly confined to mesenteric lymph nodes but showed greater IBP. Although dissemination was broader in RccHan rats, overall bacterial burden was slightly lower compared with RjHan, and extra-intestinal bacterial composition differed between groups. Notably, RjHan rats presented stronger systemic and central immune activation, with marked alterations in lymphocyte and monocyte populations and enhanced granulocyte and T cell infiltration within ischemic lesions. ConclusionsThese findings demonstrate that sub-strain origin profoundly influences post-stroke intestinal barrier integrity, bacterial dissemination, and immune responses. Considering sub-strain-related variability is essential to improve reproducibility and translational relevance in preclinical stroke research.

neuroscience↗

bioRxiv2025

Assessing post-stroke cognition in pre-clinical models: lessons and recommendations from a multi-center study

Cognitive decline is a significant long-term consequence of stroke and has no available treatments. To aid in therapy development, we sought to achieve robust detection of cognitive performance after stroke in a multi-site design. Ischemic stroke was induced in adult and middle-aged male C57BL/6J mice utilizing three well-established models: distal middle cerebral artery occlusion (dMCAO), dMCAO with hypoxia and transient MCAO. Cognitive outcomes were assessed via Novel Object Recognition (NOR) and Barnes Maze (BM) tests prior to surgery, and during sub-acute (1-2 weeks) and chronic (8 weeks) phases post-stroke. Histology and immunostaining were used to assess infarct size, tissue damage and neuronal loss, and plasma neurofilament light was quantified. We did not detect a reliable cognitive deficit after stroke using NOR but saw a promising signal from BM (single site tested only). Overall, our study highlights the often-encountered challenges in detecting post-stroke cognitive impairment within the pre-clinical stroke community, as well as a number of complexities in the design and execution of pre-clinical stroke cognition studies, particularly as applied to a multi-site structure. We provide recommendations and suggest important aspects of stroke cognition studies to consider in the future, whether operating as an individual lab or a multi-site group.

animal behavior and cognition↗

bioRxiv2025

CIRCADIAN MODULATION OF NEUTROPHIL FUNCTION DETERMINES COLLATERAL PERFUSION AND OUTCOME AFTER ISCHEMIC STROKE

Stroke is a leading cause of mortality and disability, driven by complex and time-dependent mechanisms that aggravate ischemic damage. Among them, collateral perfusion determines the initial size of the ischemic core, the rate of its expansion, and the extent of the penumbra both at stroke onset and over time. Insufficiency of collaterals may occur due to genetic factors or other determinants, such as aging or cardiovascular risk factors, which reduce the number of collaterals or the diameter of those that remain. But aspects of less structural nature could also affect the effectiveness of these pathways by decreasing their patency. We hereby show that diurnal fluctuations in infarct volume in ischemic stroke mouse models are neutrophil phenotype-dependent, since differences in infarct volumes were abolished by depleting neutrophils or blocking their circadian clock, and linked to the collateral circulation: during the inactive phase of mice (daytime), collateral perfusion in the ipsilesional hemisphere was reduced, coinciding with an increase in intravascular neutrophil accumulation, suggestive of microvascular stalling. Single-cell transcriptomics, ex vivo functional assays and in vivo pharmacological and genetic strategies confirmed enhanced neutrophil extracellular traps (NETs) formation at this time. Importantly, in a cohort of human stroke patients, we identified diurnal oscillations in neutrophil and NET-related biomarkers, peaking during the human inactive phase (evening/night), and similarly associated with reduced collateral flow and poorer clinical outcomes. These findings underscore the critical role of neutrophils, their circadian dynamics and NET release in driving collateral insufficiency and ischemic brain damage, suggesting novel personalized therapeutic strategies based on circadian rhythms for the treatment of stroke.

immunology↗

bioRxiv2024

Impact of bacterial translocation in stroke outcome. Soluble CD14 as early clinical marker and effect of TLR4

Bacterial infections are among the most common complications in stroke patients. While some factors triggering these infections are well established, bacterial translocation (BT) from the intestine to other organs represents another significant factor to consider. In our study, we observed a high percentage of animals with intestinal barrier dysfunction (GBD) and BT following stroke, with typical intestinal bacteria even detected in the lungs. Moreover, this process not only exacerbates peripheral/central inflammation but also increases lesion size. In this context, our data in stroke patients demonstrate the presence of GBD, associated with elevated levels of soluble CD14 as a marker, and its strong correlation with neurological status, infarct volume, and the development of infections. Finally, our findings highlight the neuroprotective effects of the absence or pharmacological inhibition of TLR4 using ApTOLL, which not only reduces infarct volume and inflammation but also mitigates GBD/BT processes following experimental stroke.

neuroscience↗

bioRxiv2022

IPSILESIONAL HIPPOCAMPAL GABA CORRELATES WITH COGNITIVE IMPAIRMENT AND MALADAPTIVE NEUROGENESIS AFTER STROKE IN MICE

BackgroundCognitive dysfunction is a frequent stroke sequela but its pathogenesis and treatment remain unresolved. Involvement of aberrant hippocampal neurogenesis and maladaptive circuitry remodelling has been proposed but their mechanisms are unknown. Our aim was to evaluate potential underlying molecular/cellular events implicated. MethodsStroke was induced by permanent occlusion of the middle cerebral artery (MCAO) in 2-month-old C57BL/6 male mice. Hippocampal metabolites/neurotransmitters were analysed longitudinally by in vivo magnetic resonance spectroscopy (MRS). Cognitive function was evaluated with the contextual fear conditioning test. Microglia, astrocytes, neuroblasts and interneurons were analysed by immunofluorescence. ResultsApproximately 50% of mice exhibited progressive post-MCAO cognitive impairment. Notably, immature hippocampal neurons in the impaired group displayed more severe aberrant phenotypes than those from the non-impaired group. Using MRS, significant bilateral changes in hippocampal metabolites such as myo-Inositol (mIns) or N-acetylaspartic acid (NAA) were found that correlated, respectively, with numbers of glia and immature neuroblasts in the ischemic group. Importantly, some metabolites were specifically altered in the ipsilateral hippocampus suggesting its involvement in aberrant neurogenesis and remodelling processes. Specifically, MCAO animals with higher hippocampal GABA levels displayed worse cognitive outcome. Implication of GABA in this setting was supported by the amelioration of ischemia-induced memory deficits and aberrant hippocampal neurogenesis after blocking pharmacologically GABAergic neurotransmission. These data suggest that GABA exerts its detrimental effect, at least partly, by affecting morphology and integration of newborn neurons into the hippocampal circuits. ConclusionsHippocampal GABAergic neurotransmission could be considered a novel diagnostic and therapeutic target for post-stroke cognitive impairment.

animal behavior and cognition↗