Biology subjects

Liesz, A.

Publications and source records attributed to Liesz, A..

18 recordsLinked to original sources

bioRxiv2026

MRI-Compatible Rigid Head Holders for Artifact-Free Multimodal Imaging in Mice

PurposeHigh-resolution intravital microscopy allows cellular-scale analysis of the brain in vivo but is greatly sensitive to physiological motion. Combining optical microscopy with magnetic resonance imaging (MRI) in the same animal could relate cellular and mesoscale functional readout to whole-brain structural information, but this requires head holders that are both mechanically rigid and MRI compatible. Conventional metallic head holders introduce MRI artifacts, whereas many nonmetallic alternatives lack sufficient stability for chronic microscopy. Thus, we developed rigid, MRI-compatible head holders engineered from 3D-printed zirconia ceramics to reduce motion during microscopy while preserving MRI image quality. MethodsHead holders were designed for mouse cranial fixation and fabricated from zirconia ceramics using additive manufacturing. We quantified motion artifacts during two-photon and multimodal widefield imaging of the mouse cortex and assessed their impact on neuronal calcium activity, functional connectivity, and hemodynamic readouts. MRI compatibility was evaluated by measuring image quality in the presence of the head holder. ResultsThe ceramic head holders provided mechanical stability to reduce motion artifacts to micrometer levels during intravital imaging. The head holders produced no detectable susceptibility artifacts in MRI, and image contrast was comparable to control acquisitions performed without head holder. Sequential optical and MRI imaging of the same brain regions established artifact-minimized multimodal data acquisition within the same animal. ConclusionsNon-metallic ceramic head holders support longitudinal multimodal studies that combine high-resolution optical microscopy with whole-brain MRI measurements in the same animal.

neuroscience↗

bioRxiv2025

GluTrooper: a novel reporter mouse line for whole-brain imaging of glutamate dynamics

Glutamate is the primary excitatory neurotransmitter in the mammalian brain. However, tools to image glutamate dynamics in the whole brain with high spatial and temporal resolution are lacking. Therefore, we developed GluTrooper, a novel mouse line engineered for inducible and long-lasting expression of the genetically encoded glutamate sensor iGluSnFR3. GluTrooper mice crossed with Emx1-Cre lines demonstrated uniform and stable sensor expression in excitatory neurons of the cortex, hippocampus, and olfactory bulb. iGluSnFR3 expression remained stable for at least 12 months, enabling longitudinal observations of glutamate dynamics over extended periods. Using multimodal imaging in awake mice, we demonstrated the versatility of GluTrooper across multiple spatial scales: from mesoscale widefield cortical imaging to cellular resolution with two-photon microscopy. Moreover, during cortical spreading depolarization, bilateral whole-brain glutamate dynamics and contralateral cortical disinhibition were detected with high fidelity. Accordingly, the GluTrooper may open new avenues for the better understanding of glutamatergic neurotransmission in the mammalian brain.

neuroscience↗

bioRxiv2025

LipiGo: A Versatile DNA-Lipid Nanoparticle Hybrid for Precision Drug Delivery

Lipid nanoparticles (LNPs) are established carriers for nucleic acid delivery, however, achieving efficient delivery to non-hepatic tissues remains a major challenge. Here, we present LipiGo, a nanocarrier platform engineered by integrating short single stranded DNA molecules into the lipid nanoparticle structure. Using whole body tissue clearing, advanced imaging and AI-based analysis, we show that LipiGo redirects functional mRNA delivery to lymphoid organs, particularly the spleen. Immune cell profiling further reveals enhanced uptake within key immune populations, including antigen-presenting cells, compared to standard LNPs. Beyond passive redistribution, LipiGo leverages DNA hybridization to enable modular attachment of targeting ligands for active targeting as demonstrated by cell-specific delivery to white adipocytes. Overall, the dual-purpose design principle of LipiGo demonstrates high modularity and efficiency, enabling tissue and cell specific delivery beyond hepatic applications. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=100 SRC="FIGDIR/small/676334v2_ufig1.gif" ALT="Figure 1"> View larger version (45K): org.highwire.dtl.DTLVardef@9b69eorg.highwire.dtl.DTLVardef@1b45bd0org.highwire.dtl.DTLVardef@1f7b79dorg.highwire.dtl.DTLVardef@37a673_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2024

Spatial quantitative metabolomics enables identification of remote and sustained ipsilateral cortical metabolic reprogramming after stroke

Mass spectrometry imaging (MSI) has become a cornerstone of spatial biology research. However, various factors that are intrinsic to the technology limit quantitative capacity of MSI-based spatial metabolomics and thus reliable interpretation. Here, we developed a quantitative MSI workflow (Q-MSI), based on isotopically 13C-labeled yeast extract as internal standards, to overcome these pitfalls. Using brain and kidney tissue, we demonstrate that this approach allows for (absolute) quantification of hundreds of metabolites and lipids. Applying our workflow to a stroke model allowed us to not only map metabolic remodeling of the infarct and peri-infarct area over time, but also discover hitherto unnoted remote metabolic remodeling in the histologically unaffected ipsilateral sensorimotor cortex. At day 7 post-stroke, increased levels of neuroprotective lysine and reduced excitatory glutamate levels were found compared to the contralateral cortex. By day 28 post-stroke, lysine and glutamate levels had been normalized, while decreased precursor pools of UDP-GlcNAc and linoleate persisted that have previously been associated with vulnerability. Importantly, traditional normalization strategies not employing internal standards were unable to visualize these differences. Using 13C-labeled yeast extracts as a normalization strategy establishes a new paradigm in quantitative MSI-based spatial metabolomics that greatly enhances reliability and interpretive strength.

biochemistry↗

bioRxiv2023

Innate immune memory after brain injury drives inflammatory cardiac dysfunction

The enormous medical burden of stroke is not only due to the brain injury itself and the acute systemic effects, but is largely determined by chronic comorbidities that develop secondarily after stroke. We hypothesized that the high rate of comorbidity developing after a stroke might have a shared immunological cause, however, the chronic effects of brain injury on systemic immunity have so far been barely investigated. Here, we identified myeloid innate immune memory as a cause of remote organ dysfunction after stroke. Using single-cell sequencing, we identified persistent pro-inflammatory transcriptomic changes in resident monocytes/macrophages in multiple organs one month after experimental ischemic brain injury, which was particularly abundant in the heart and associated with the development of cardiac fibrosis and diastolic dysfunction. A similar phenotype was seen in myocardial autopsy samples from stroke versus control patients. We observed chronic functional changes in myeloid hematopoiesis driven by post-stroke IL-1{beta}-mediated epigenetic changes. These alterations could be transplanted to naive recipient mice and were sufficient to induce cardiac dysfunction. By effectively blocking the trafficking of pro-inflammatory monocytes from the bone marrow to the heart using a dual CCR2/5 inhibitor, we successfully prevented post-stroke cardiac dysfunction. This approach holds promising potential as a novel immune-targeted secondary prevention therapy. We anticipate that the epigenetic immune reprogramming mechanisms detailed here for the brain-heart axis could be generalized to provide a novel framework for explaining the development of various comorbidities after acute tissue injury in remote organs.

immunology↗

bioRxiv2023

Single-cell precision nanotechnology in vivo

Targeting nanoparticle therapeutics with cellular accuracy in whole organisms could open breakthrough opportunities in precision medicine. However, evaluating and fine-tuning the biodistribution of such systems in the whole organism at the cellular level remains a major obstacle. Here, we constructed targetable DNA origami, and analyzed biodistribution in transparent mice, in addition to studying tolerability, clearance kinetics, and immune response parameters. Untargeted DNA origami primarily accumulated in the spleen and the liver, while an immune cell-targeting variant successfully attached to immune cells throughout the body. A cancer cell-targeting mimetic co-localized on solid-tumor metastasis in the liver and the lung. These findings indicate that DNA origami can be directed in vivo, providing an important proof-of-concept and highlights the potential of high-resolution tissue-clearing imaging technologies in their development. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=121 SRC="FIGDIR/small/550304v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@ce216borg.highwire.dtl.DTLVardef@f40bb4org.highwire.dtl.DTLVardef@2c6a66org.highwire.dtl.DTLVardef@1fd7fde_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIThis study demonstrates the potential of DNA origami-based drug delivery systems as versatile tool for for targeted delivery, which could be used to treat a range of diseases with applications. C_LIO_LIThe immune compatibility, half-life, targeting efficiency, and the biodistribution evaluation of DNA origami indicate its potential for systemic drug delivery. C_LIO_LIOur approach enables the assessment of biodistribution of nanoparticles in the intact body with a sensitivity to the single-cell level, highlighting the high-resolution tissue clearing technoloies in revealing DNA origamis feasibility for drug targeting. C_LI

bioengineering↗

bioRxiv2023

Infection-induced vascular inflammation in COVID-19 links focal microglial dysfunction with neuropathologies through IL-1/IL-6-related systemic inflammatory states

COVID-19 is associated with diverse neurological abnormalities, which predict poor outcome in patients. However, the mechanisms whereby infection-induced inflammation could affect complex neuropathologies in COVID-19 are unclear. We hypothesized that microglia, the resident immune cells of brain, are centrally involved in this process. To study this, we developed an autopsy platform allowing the integration of molecular anatomy-, protein- and mRNA data sets in post-mortem mirror blocks of brain and peripheral organ samples from COVID-19 cases. Nanoscale microscopy, single-cell RNA sequencing and analysis of inflammatory and metabolic signatures revealed distinct mechanisms of microglial dysfunction associated with cerebral SARS-CoV-2 infection. We observed focal loss of microglial P2Y12R at sites of virus-associated vascular inflammation together with dysregulated microglia-vascular-astrocyte interactions, Cx3Cr1-fractalkine axis deficits and mitochondrial failure in severely affected medullary autonomic nuclei and other brain areas. Microglial dysfunction occurs at sites of excessive synapse- and myelin phagocytosis and loss of glutamatergic terminals. While central and systemic viral load is strongly linked in individual patients, the regionally heterogenous microglial reactivity in the brain correlated with the extent of central and systemic inflammation related to IL-1 / IL-6 via virus-sensing pattern recognition receptors (PRRs) and inflammasome activation pathways. Thus, SARS-CoV-2-induced central and systemic inflammation might lead to a primarily glio-vascular failure in the brain, which could be a common contributor to diverse COVID-19-related neuropathologies.

immunology↗

bioRxiv2023

Continued dysfunction of capillary pericytes promotes no-reflow after experimental stroke in vivo

Incomplete reperfusion of the microvasculature ("no-reflow") after ischemic stroke damages salvageable brain tissue. Previous ex-vivo studies suggest pericytes are vulnerable to ischemia and may exacerbate no-reflow, but the viability of pericytes and their association with no-reflow remains underexplored in vivo. Using longitudinal in vivo 2-photon single-cell imaging over seven days we show 87% of pericytes constrict during cerebral ischemia, remain constricted post-reperfusion and 50% of the pericyte population are acutely damaged. Moreover, we reveal ischemic pericytes are fundamentally implicated in capillary no-reflow by limiting and arresting blood flow within the first 24 hours post-stroke. Despite sustaining acute membrane damage, we observe up to 80% of cortical pericytes survive ischemia, upregulate unique transcriptomic profiles and replicate. Finally, we demonstrate delayed recovery of capillary diameter by ischemic pericytes after reperfusion predicts vessel reconstriction in the sub-acute phase of stroke. Cumulatively, these findings demonstrate surviving cortical pericytes remain both viable and promising therapeutic targets to counteract no-reflow after ischemic stroke.

neuroscience↗

bioRxiv2023

Stroke induces early recurrent vascular events by inflammasome-dependent atherosclerotic plaque rupture

The risk of early recurrent events after stroke remains high despite currently established secondary prevention strategies. Risk is particularly high in patients with atherosclerosis, with more than 10% of patients experiencing early recurrent events. However, despite the enormous medical burden of this clinical phenomenon, the underlying mechanisms leading to increased vascular risk and recurrent stroke are largely unknown. Here, using a novel mouse model of stroke-induced recurrent ischemia, we show that stroke leads to activation of the AIM2 inflammasome in vulnerable atherosclerotic plaques via an increase of circulating cell-free DNA from the ischemic tissue. Enhanced plaque inflammation post-stroke results in plaque destabilization and atherothrombosis, finally leading to arterio-arterial embolism and recurrent stroke within days after the index stroke. We confirm key steps of plaque destabilization also after experimental myocardial infarction and in carotid artery plaque samples from patients with acute stroke. Neutralization of cell-free DNA by DNase treatment or inhibition of inflammasome activation reduced the rate of stroke recurrence after experimental stroke. Our findings present an explanation for the high recurrence rate after incident ischemic events in atherosclerotic patients. The detailed mechanisms uncovered here provide so far clinically uncharted therapeutic targets for which we show high efficacy to prevent recurrent events. Targeting DNA-mediated inflammasome activation after remote tissue injury represents a promising avenue for further clinical development in the prevention of early recurrent events.

immunology↗

bioRxiv2022

Discovery of an AIM2 inflammasome inhibitor for the treatment of DNA-driven inflammatory disease.

Inflammation driven by DNA sensors is now understood to be central to disease pathogenesis. Here we describe new inhibitors of pathogenic DNA sensing, primarily of the inflammasome forming sensor AIM2. Molecular modelling and biochemistry has revealed potent inhibitors of AIM2 that work by binding competitively to the DNA binding site. Though less potent, these AIM2 inhibitors, 4-sulfonic calixarenes, also inhibit DNA sensors cGAS and TLR9 demonstrating a broad utility against pathogenic DNA-driven inflammatory responses. The 4-sulfonic calixarenes inhibited AIM2 dependent post-stroke T cell death, highlighting a proof of concept that the 4-sulfonic calixarenes could be effective at combatting post-stroke immunosuppression. By extension, we propose a broad utility against DNA driven inflammation in disease. Finally, we reveal that the ancient drug suramin, by virtue of its structural similarities, is an excellent inhibitor of DNA-dependent inflammation and propose that suramin could be rapidly repurposed to meet an ever increasing clinical need.

immunology↗

bioRxiv2022

T cells induce interferon-responsive oligodendrocytes during white matter aging

A hallmark of nervous system aging is a decline of white matter volume and function, but the underlying mechanisms leading to white matter pathology are unknown. Here, we found age-related alterations of oligodendrocytes with a reduction of total oligodendrocyte density in the aging murine white matter. Using single-cell RNA sequencing, we identify interferon-responsive oligodendrocytes, which localize in proximity of CD8+ T cells in the aging white matter. Absence of functional lymphocytes decreased oligodendrocyte reactivity and rescued oligodendrocyte loss, while T-cell checkpoint inhibition worsened the aging affect. In summary, we provide evidence that T cells induced interferon-responsive oligodendrocytes are important modifiers of white matter aging.

neuroscience↗

bioRxiv2021

T cells modulate the microglial response to brain ischemia

Neuroinflammation after stroke is characterized by the activation of resident microglia and the invasion of circulating leukocytes into the brain. Although lymphocytes infiltrate the brain in small number, they have been consistently demonstrated to be the most potent leukocyte subpopulation contributing to secondary inflammatory brain injury. However, the exact mechanism how this minimal number of lymphocytes can profoundly affect stroke outcome is still largely elusive. Here, using a mouse model for ischemic stroke, we demonstrated that early activation of microglia in response to stroke is differentially regulated by distinct T cell subpopulations. Acute treatment with engineered T cells overexpressing IL-10 administered into the cisterna magna after stroke induces a switch of microglial gene expression to a profile associated with pro-regenerative functions. These findings substantiate the role of T cells in stroke with large impact on the cerebral inflammatory milieu by polarizing the microglial phenotype. Targeting T cell-microglia interactions can have direct translational relevance for further development of immune-targeted therapies for stroke and other neuroinflammatory conditions. SummaryThe crosstalk between brain infiltrating T cells and microglia in response to stroke remains elusive. Benakis et al. report that transcriptional signature of the stroke-associated microglia is reprogrammed by distinct T cell subpopulations. Engineered T cells overexpressing IL-10 administered four hours after stroke reinitiate microglial function inducing a pro-regenerative environment.

immunology↗

bioRxiv2021

Loss of TREM2 reduces hyperactivation of progranulin deficient microglia but not lysosomal pathology

GRN haploinsufficiency causes frontotemporal lobar degeneration and results in microglial hyperactivation, lysosomal dysfunction and TDP-43 deposition. To understand the contribution of microglial hyperactivation to pathology we evaluated genetic and pharmacological approaches suppressing TREM2 dependent transition of microglia from a homeostatic to a disease associated state. Trem2 deficiency in Grn KO mice led to a reduction of microglia activation. To explore antibody-mediated pharmacological modulation of TREM2-dependent microglial states, we identified antagonistic TREM2 antibodies. Treatment of macrophages from GRN-FTLD patients with these antibodies allowed a complete rescue of elevated levels of TREM2 together with increased shedding and reduction of TREM2 signaling. Furthermore, antibody-treated PGRN deficient hiMGL showed dampened microglial hyperactivation, reduced TREM2 signaling and phagocytic activity, however, lack of rescue of lysosomal dysfunction. Similarly, lysosomal dysfunction, lipid dysregulation and glucose hypometabolism of Grn KO mice were not rescued by TREM2 ablation. Furthermore, NfL, a biomarker for neurodegeneration, was elevated in the Grn/Trem2 KO. These findings suggest that microglia hyperactivation is not necessarily contributing to neurotoxicity, and instead demonstrates that TREM2 exhibits neuroprotective potential in this model.

neuroscience↗

bioRxiv2020

Microbiota-derived short chain fatty acids promote Aβ plaque deposition

Previous studies have identified a crucial role of the gut microbiome in modifying Alzheimers disease (AD) progression. However, the mechanisms of microbiome-brain interaction in AD, including the microbial mediators and their cellular targets in the brain, were so far unknown. Here, we identify microbiota-derived short chain fatty acids (SCFA) as key metabolites along the gut-brain axis in AD. Germ-free (GF) AD mice exhibit a substantially reduced A{beta} plaque load and markedly reduced SCFA plasma concentrations; conversely, SCFA supplementation to GF AD mice was sufficient to increase the A{beta} plaque load to levels of conventionally colonized animals. While A{beta} generation was only mildly affected, we observed strong microglial activation and upregulation of ApoE upon the SCFA supplementation. Taken together, our results demonstrate that microbiota-derived SCFA are the key mediators along the gut-brain axis resulting in increased microglial activation, ApoE upregulation and A{beta} deposition.

neuroscience↗

bioRxiv2019

Fibrillar Aβ triggers microglial proteome alterations and dysfunction in Alzheimer mouse models

Microglial dysfunction is a key pathological feature of Alzheime[r]s disease (AD), but little is known about proteome-wide changes in microglia during the course of AD pathogenesis and their functional consequences. Here, we performed an in-depth and time-resolved proteomic characterization of microglia in two mouse models of amyloid {beta} (A{beta}) pathology, the overexpression APPPS1 and the knock-in APP-NL-G-F (APP-KI) model. We identified a large panel of Microglial A{beta} Response Proteins (MARPs) that reflect a heterogeneity of microglial alterations during early, middle and advanced stages of A{beta} deposition. Although both mouse models display severe microglial alterations at late stages of amyloid pathology, MARP signatures occur earlier in the APPPS1 mice. Strikingly, the kinetic differences in proteomic profiles correlated with the presence of fibrillar A{beta}, rather than dystrophic neurites, suggesting that fibrillar A{beta} aggregates are the main drivers of the AD-associated microglial phenotype and the observed functional decline. The identified microglial proteomic fingerprints of AD provide a valuable resource for functional studies of novel molecular targets and potential biomarkers for monitoring AD progression or therapeutic efficacy.

neuroscience↗

bioRxiv2019

Microglia monitor and protect neuronal function via specialized somatic purinergic junctions

Microglia are the main immune cells in the brain with emerging roles in brain homeostasis and neurological diseases, while mechanisms underlying microglia-neuron communication remain elusive. Here, we identify a novel site of interaction between neuronal cell bodies and microglial processes in mouse and human brain. Somatic microglia-neuron junctions possess specialized nanoarchitecture optimized for purinergic signaling. Activity of neuronal mitochondria is linked with microglial junction formation, which is rapidly induced in response to neuronal activation and blocked by inhibition of P2Y12-receptors (P2Y12R). Brain injury-induced changes at somatic junctions trigger P2Y12R-dependent microglial neuroprotection, regulating neuronal calcium load and functional connectivity. Collectively, our results suggest that microglial processes at these junctions are in ideal position to monitor and protect neuronal functions in both the healthy and injured brain.\n\nOne-sentence summaryNeuronal cell bodies possess specialized, pre-formed sites, through which microglia monitor their status and exert neuroprotection.

neuroscience↗

bioRxiv2018

In vivo widefield calcium imaging of the mouse cortex for analysis of network connectivity in health and brain disease

The organization of brain areas in functionally connected networks, their dynamic changes, and perturbations in disease states are subject of extensive investigations. Research on functional networks in humans predominantly uses functional magnetic resonance imaging (fMRI). However, adopting fMRI and other functional imaging methods to mice, the most widely used model to study brain physiology and disease, poses major technical challenges and faces important limitations. Hence, there is great demand for alternative imaging modalities for network characterization. Here, we present a refined protocol for in vivo widefield calcium imaging of both cerebral hemispheres in mice expressing a calcium sensor in excitatory neurons. We implemented a stringent protocol for minimizing anesthesia and excluding movement artifacts which both imposed problems in previous approaches. We further adopted a method for unbiased identification of functional cortical areas using independent component analysis (ICA) on resting-state imaging data. Biological relevance of identified components was confirmed using stimulus-dependent cortical activation. To explore this novel approach in a model of focal brain injury, we induced photothrombotic lesions of the motor cortex, determined changes in inter- and intrahemispheric connectivity at multiple time points up to 56 days post-stroke and correlated them with behavioral deficits. We observed a severe loss in interhemispheric connectivity after stroke, which was partially restored in the chronic phase and associated with corresponding behavioral motor deficits. Taken together, we present an improved widefield calcium imaging tool accounting for anesthesia and movement artifacts, adopting an advanced analysis pipeline based on human fMRI algorithms and with superior sensitivity to recovery mechanisms in mouse models compared to behavioral tests. This tool will enable new studies on interhemispheric connectivity in murine models with comparability to human imaging studies for a wide spectrum of neuroscience applications in health and disease.

neuroscience↗

bioRxiv2018

Panoptic vDISCO imaging reveals neuronal connectivity, remote trauma effects and meningeal vessels in intact transparent mice

Analysis of entire transparent rodent bodies could provide holistic information on biological systems in health and disease. However, it has been challenging to reliably image and quantify signal from endogenously expressed fluorescent proteins in large cleared mouse bodies due to the low signal contrast. Here, we devised a pressure driven, nanobody based whole-body immunolabeling technology to enhance the signal of fluorescent proteins by up to two orders of magnitude. This allowed us to image subcellular details in transparent mouse bodies through bones and highly autofluorescent tissues, and perform quantifications. We visualized for the first-time whole-body neuronal connectivity of an entire adult mouse and discovered that brain trauma induces degeneration of peripheral axons. We also imaged meningeal lymphatic vessels and immune cells through the intact skull and vertebra in naive animals and trauma models. Thus, our new approach can provide an unbiased holistic view of biological events affecting the nervous system and the rest of the body.\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=151 SRC=\"FIGDIR/small/374785_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (62K):\norg.highwire.dtl.DTLVardef@8fad72org.highwire.dtl.DTLVardef@c41ed5org.highwire.dtl.DTLVardef@1c470eaorg.highwire.dtl.DTLVardef@1d144cb_HPS_FORMAT_FIGEXP M_FIG C_FIG Note: Manuscript videos are available at Supplementary material section of BioRxiv and at the following link http://vdisco.isd-muc.de/

neuroscience↗