Biology subjects

Brezzo, G.

Publications and source records attributed to Brezzo, G..

6 recordsLinked to original sources

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

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

Prominent white matter related abnormalities associated with diverse molecular alterations in a mouse model of Col4a1 cerebral small vessel disease.

White matter abnormalities are a hallmark of cerebral small vessel disease (cSVD) and are closely linked to cognitive decline and dementia. However, despite their clinical importance, underlying mechanisms remain poorly understood. Collagen IV, encoded by genes COL4A1/COL4A2, is a major component of the basement membrane, a specialised extracellular matrix (ECM) structure. Mutations in these genes cause a genetic form of cSVD. We tested the hypothesis that ECM defects caused by a Col4a1 mutation lead to white matter pathology using an established mouse model of cSVD (Col4a1+/Svc). Behavioural testing with magnetic resonance diffusion tensor imaging, pathology and ultrastructural investigations of white matter were studied. The studies revealed that Col4a1+/Svc mice have cognitive impairments, reduced myelinating oligodendrocyte pools, axonal myelination defects, and altered white matter structural integrity. Proteomic analysis, of isolated white matter from Col4a1+/Svcmice, identified extensive changes to ECM composition and endoplasmic reticulum (ER) biology including ER stress induction. We also demonstrated that targeting protein folding to promote collagen secretion and reduce ER stress, increased myelinating oligodendrocytes and axon-glial integrity in Col4a1+/Svc mice. These data provide novel insight into the pathomolecular mechanisms of white matter abnormalities in cSVD and identify a modifiable pathway as a putative therapeutic target for cSVD.

neuroscience↗

bioRxiv2023

Cholinergic Modulation of Neurovascular Coupling and Neuroimaging Signals

The use of non-invasive functional neuroimaging methods to discriminate levels or patterns of brain activity between different groups, across different time points, or in response to drug treatment, depends on an understanding of neurovascular coupling relationships and how they themselves are affected by the factors of interest. For instance, Alzheimers disease (AD) features cerebral blood flow (CBF) and neurovascular unit changes as well as being characterised by a cholinergic dysfunction which impacts upon CBF regulation. The present study investigated the acute neurovascular effects of cholinergic agonist and antagonist treatment in a rat model utilising a multimodal measurement approach. Drugs were administered to rats during concurrent imaging of cortical CBF and recording of local field potential responses to somatosensory stimulation. Analysis of concurrent neuronal and vascular measures revealed a pronounced loss of neurovascular coupling following treatment with the cholinergic antagonist scopolamine. Separate analysis of CBF and neuronal responses reveal an interaction effect of stimulus input and drug treatment for both cholinergic agonist and antagonist treatment, as well as an augmentation of both neuronal and haemodynamic response magnitudes after treatment with the clinically prescribed cholinergic agonist donepezil. These findings have implications for the use and interpretation of functional neuroimaging data acquired in individuals with disease-related or pharmacological manipulations of cholinergic function.

neuroscience↗

bioRxiv2018

Acute effects of systemic inflammation upon neurovascular unit and cerebrovascular function.

Background: Brain health relies on a tightly regulated system known as neurovascular function whereby the cellular constituents of the neurovascular unit (NVU) regulate cerebral haemodynamics in accordance with neuronal metabolic demand. Disruption of neurovascular function impairs brain health and is associated with the development of disease, including Alzheimer's disease (AD). The NVU is the site of action of neuroinflammatory responses and contributes to the transition of systemic inflammation to neuroinflammatory processes. Thus, systemic inflammatory challenges may cause a shift in the NVU focus, prioritising neuroimmune over neurovascular actions leading to altered neurovascular function. Methods: Rats were injected with lipopolysaccharide (LPS) (2mg/kg) or vehicle and haemodynamic responses to sensory and non-sensory (hypercapnia) stimuli were assessed in vivo. Following imaging, animals were perfused and their brain extracted to histologically characterise components of the NVU to determine the association between underlying pathology to altered blood flow regulation in vivo. Results: LPS-treated animals showed altered haemodynamic function and cerebrovascular dynamics 6 hours after LPS administration. Histological assessment identified a significant increase in astrogliosis, microgliosis and endothelial activation in LPS-treated animals. Conclusions: Our data shows that an acutely induced systemic inflammatory response is able to rapidly alter in-vivo haemodynamic function and is associated with significant changes in the cellular constituents of the NVU. We suggest that these effects are initially mediated by endothelial cells, which are directly exposed to the circulating inflammatory stimulus and have been implicated in regulating functional hyperaemia.

neuroscience↗

bioRxiv2018

The Time Course of Recognition Memory Impairment and Glial Pathology in the hApp-J20 Mouse Model of Alzheimer’s Disease

The role of cellular changes in the neurovascular unit is increasingly being investigated to understand the pathogenesis of Alzheimers disease. The aim of the current study was to determine the time course of recognition memory impairment in the J20 mouse model of AD, in relation to neuroinflammatory responses and the pathology of A{beta}.\n\nMale hAPP-J20 and wild-type mice were assessed at 3, 6, 9, and 12 months of age. The spontaneous object recognition (SOR) task provided a measure of memory, with assessment of both a short delay (1 min) and a long delay (4 hrs). Immunohistochemistry was used to characterise A{beta}-deposition, and quantify astrocyte and microglial responses.\n\nAt all ages tested J20 mice had impaired long-term, but preserved short-term, recognition memory. Wild-types demonstrated preserved long-term memory up to 9 months of age, and preserved short-term memory at all ages tested. Plaque pathology in the J20 mice was present from 6 months onwards, with co-localisation of reactive microglia and activated astrocytes. Reactive microglia and astrocyte activation in the hippocampus were significantly greater in the J20 mice at 9 months, compared to wild-types.\n\nThis study contributes to our understanding of the pathological and cognitive mechanisms at play in AD. J20 mice showed impairment in retaining information over longer periods from an early age, preceding the deposition of A{beta} and glial activation. Defining early physiological changes in relation to cognitive decline could provide insight into new therapeutic targets early in the disease process, when intervention is most likely to effectively slow disease progression.

neuroscience↗