Biology subjects

Wendt, S.

Publications and source records attributed to Wendt, S..

6 recordsLinked to original sources

bioRxiv2026

Brain pericytes are an oxidative stress-sensitive cell population damaged through ROS-1 dependent TRPA1 activation.

Oxidative stress is a pathological process driven by an imbalance between the production and clearance of reactive oxygen species (ROS). It is a hallmark of numerous brain disorders, driving neuroinflammation, blood-brain barrier (BBB) disruption, and neurodegeneration. Here, we used two-photon microscopy in rodent brain slices to evaluate cell-type vulnerability to oxidative stress. We identified a microvascular cell population displaying pronounced sensitivity to H2O2 and thiol oxidation. These Pdgfr-{beta} expressing cells were identified as pericytes and perivascular fibroblasts. Because pericytes regulate capillary perfusion and BBB integrity, we examined mechanisms driving their injury. Pericyte damage was independent of apoptosis or necroptosis, but required Ca2+ influx. While blocking voltage-gated Ca2+, TRPC, Orai channels was ineffective, inhibitors of TRPA1 channels reduced pericyte damage. Immunostaining and western blotting showed TRPA1 associated with brain capillaries and pericytes. Functionally, TRPA1 regulated uptake of the pericyte-selective marker NeuroTrace, whereas pericyte GCaMP6f imaging demonstrated that TRPA1 was not the primary driver of cytosolic Ca2+ elevations during oxidative stress. These findings establish pericytes as vulnerable targets of oxidative stress and implicate TRPA1 as a mediator of pericyte structural degeneration. This sensitivity to oxidative stress, mediated by ROS-TRPA1 coupling, could contribute to the pericyte stress and degeneration observed in brain pathology.

neuroscience↗

bioRxiv2024

Microglia-astrocyte interplay mitigates Aβ toxicity in a novel human 3D neurosphere model of Alzheimer's Disease

BackgroundAlzheimers Disease (AD) is characterized by progressive amyloid beta (A{beta}) deposition in the brain, with eventual widespread neurodegeneration. While the cell-specific molecular signature of end-stage AD is reasonably well characterized through autopsy material, less is known about the molecular pathways in the human brain involved in the earliest exposure to A{beta}. Human model systems that not only replicate the pathological features of AD but also the transcriptional landscape in neurons, astrocytes and microglia are crucial for understanding disease mechanisms and for identifying novel therapeutic targets. MethodsIn this study, we used a human 3D iPSC-derived neurosphere model to explore how resident neurons, microglia and astrocytes and their interplay are modified by chronic amyloidosis induced over 3 to 5 weeks by supplementing media with synthetic A{beta}1-42 oligomers. Neurospheres under chronic A{beta} exposure were grown with or without microglia to investigate the functional roles of microglia. Neuronal activity and oxidative stress were monitored using genetically encoded indicators, including GCaMP6f and roGFP1, respectively. Single nuclei RNA sequencing (snRNA-seq) was performed to profile A{beta} and microglia driven transcriptional changes in neurons and astrocytes, providing a comprehensive analysis of cellular responses. ResultsMicroglia efficiently phagocytosed A{beta} inside neurospheres and significantly reduced neurotoxicity, mitigating amyloidosis-induced oxidative stress and neurodegeneration following different exposure times to A{beta}. The neuroprotective effects conferred by the presence of microglia was associated with unique gene expression profiles in astrocytes and neurons, including several known AD-associated genes such as APOE. These findings reveal how microglia can directly alter the molecular landscape of AD. ConclusionsOur human 3D neurosphere culture system with chronic A{beta} exposure reveals how microglia may be essential for the cellular and transcriptional responses in AD pathogenesis. Microglia are not only neuroprotective in neurospheres but also act as key drivers of A{beta}-dependent APOE expression suggesting critical roles for microglia in regulating APOE in the AD brain. This novel, well characterized, functional in vitro platform offers unique opportunities to study the roles and responses of microglia to A{beta} modelling key aspects of human AD. This tool will help identify new therapeutic targets, accelerating the transition from discovery to clinical applications. HighlightsO_LIWell-characterized functional human iPSC-derived 3D neurospheres (hiNS) consisting of neurons and astrocytes can be supplemented with microglia/macrophages (hiMG) C_LIO_LIChronic amyloidosis in the presence of hiMG recapitulate key features and gene expression profiles of AD C_LIO_LIhiMG within the model phagocytose A{beta} and mitigate A{beta}-induced neurotoxicity, reducing oxidative stress and neuronal damage C_LIO_LIhiMG are essential for A{beta} to upregulate AD-like gene expression signatures in astrocytes C_LIO_LIImmunohistochemical analysis reveals hiMG-dependent colocalization of A{beta} and APOE C_LI

neuroscience↗

bioRxiv2024

A microglia-containing cerebral organoid model to study early life immune challenges

Prenatal infections and activation of the maternal immune system have been proposed to contribute to causing neurodevelopmental disorders (NDDs), chronic conditions often linked to brain abnormalities. Microglia are the resident immune cells of the brain and play a key role in neurodevelopment. Disruption of microglial functions can lead to brain abnormalities and increase the risk of developing NDDs. How the maternal as well as the fetal immune system affect human neurodevelopment and contribute to NDDs remains unclear. An important reason for this knowledge gap is the fact that the impact of exposure to prenatal risk factors has been challenging to study in the human context. Here, we characterized a model of cerebral organoids (CO) with integrated microglia (COiMg). These organoids express typical microglial markers and respond to inflammatory stimuli. The presence of microglia influences cerebral organoid development, including cell density and neural differentiation, and regulates the expression of several ciliated mesenchymal cell markers. Moreover, COiMg and organoids without microglia show similar but also distinct responses to inflammatory stimuli. Additionally, IFN-{gamma} induced significant transcriptional and structural changes in the cerebral organoids, that appear to be regulated by the presence of microglia. Specifically, interferon-gamma (IFN-{gamma}) was found to alter the expression of genes linked to autism. This model provides a valuable tool to study how inflammatory perturbations and microglial presence affect neurodevelopmental processes.

neuroscience↗

bioRxiv2019

Labelling effect in insects: cue associations influence perceived food value in ants

Humans usually assess things not in terms of absolute value, but relative to reference points. The framing of alternatives can strongly affect human decision-making, leading to different choices depending on the context within which options are presented. Similar reference-point effects have been recently reported in ants, in which foragers show a contrast effect: ants overvalue a medium-quality food source if they were expecting a poor one, and vice versa for expectations of good food. However, studies of human consumer psychology have demonstrated that expectations, for example from product labels, can drive value perception in the other direction via assimilation. For example, an expensive bottle of wine is perceived as more enjoyable compared to a cheaper bottle, even if the wine is the same. In this study, we demonstrate a similar labelling-association effect in an insect: ants showed assimilation effects by spending twice as long drinking at a medium quality food source if it was scented with an odour previously associated with high quality than if it was scented with a poor-quality label. The presence of odour cues in the food during consumption and evaluation is critical, as without them, odour-driven expectations of quality result in contrast, not assimilation effects. The addition of a quality label in the food thus reverses contrast effects and causes value to be aligned with expectations, rather than being contrasted against them. As value judgement is a key element in decision-making, relative value perception strongly influences which option is chosen, and ultimately how choices are made.

animal behavior and cognition↗

bioRxiv2018

Relative value perception in an insect: positive and negative incentive contrasts in ants

Humans tend to value things not on their absolute values, but relative to reference points such as former experience or expectations. People rate the quality of a new salary relative to their previous salary and the salaries of their peers, instead of appreciating its absolute value. Here, we demonstrate a similar effect in an insect: ants, which had previously experienced a low quality food source, showed higher acceptance of medium quality food (e.g. 0.1M then 0.5M; positive contrast) than if they had received the medium food all along (e.g. 0.5M then 0.5M; control), and vice versa for high expectations. Further experiments demonstrate that these contrast effects arise from cognitive rather than mere sensory or pre-cognitive perceptual causes. Pheromone deposition also correlates with perceived reward value, and ants showed successive contrasts in their pheromone deposition. Relative value perception can therefore be expected to have strong effects not only on individual behaviour, but also on collective decision-making. Contrast effects were also social: the quality of food received from other ants affected the perceived value of food found later. Value judgement is a key element in decision making, and thus relative value perception will strongly influence how animals interact with their environment.

animal behavior and cognition↗

bioRxiv2016

Standard Issue: Copy number heterogeneity of JC virus standards discovered through next-generation sequencing

Quantitative PCR is a diagnostic mainstay of clinical virology, and accurate quantitation of viral load among labs requires the use of international standards. However, the use of multiple passages of viral isolates to obtain sufficient material for international standards may result in genomic changes that complicate their use as quantitative standards. We performed next-generation sequencing to gain single-nucleotide resolution and relative copy number of JC virus (JCV) clinical standards. Strikingly, the WHO international standard and ExactTM v1/v2 prototype standards for JCV showed 8-fold and 4-fold variation in genomic coverage between different loci in the viral genome, respectively, due to large deletions in the large T-antigen region. No such variation was seen for a clinical sample with high copy-number of JCV nor a plasmid control. Intriguingly, several of the JCV standards sequenced in this study with large T-antigen deletions were cultured in cell lines immortalized using SV40 T-antigen, suggesting the possibility of trans-complementation in cell culture. Using a cut-off of 2% variant allele fraction for junctional reads to define the presence of a strain, 11 different strains were present in the WHO standard. In summary, targeting of different regions of the same international standard could result in up to an 8-fold difference in quantitation. We recommend the use of next-generation sequencing to validate standards in clinical virology.

microbiology↗