Publications by authors named "Lucas Schirmer"

44 Publications

Spinal cord fractalkine (CX3CL1) signaling is critical for neuronal sensitization in experimental non-specific, myofascial low back pain.

J Neurophysiol 2021 Feb 17. Epub 2021 Feb 17.

Department of Neurophysiology, Mannheim Center for Translational Neurosciences, Medical Faculty Mannheim, Heidelberg University, Germany.

Neuroactive substances released by activated microglia contribute to hyperexcitability of spinal dorsal horn neurons in many animal models of chronic pain. An important feedback loop mechanism is via release of fractalkine (CX3CL1) from primary afferent terminals and dorsal horn neurons and binding to CX3CR1 receptors on microglial cells. We studied the involvement of fractalkine signaling in latent and manifest spinal sensitization induced by two injections of nerve growth factor (NGF) into the lumbar multifidus muscle as a model for myofascial low back pain. Single dorsal horn neurons were recorded in vivo to study their receptive fields and spontaneous activity. Under intrathecal vehicle application, the two NGF injections led to an increased proportion of neurons responding to stimulation of deep tissues (41%), to receptive field expansion into the hind limb (15%), and to resting activity (53%). Blocking fractalkine signaling by continuous intrathecal administration of neutralizing antibodies completely prevented these signs of spinal sensitization to a similar extent as in a previous study with the microglia inhibitor minocycline. Reversely, fractalkine itself induced similar sensitization in a dose dependent manner (for 200 ng/ml: 45% deep tissue responses, 24% receptive field expansion, 45% resting activity) as repeated nociceptive stimulation by intramuscular NGF injections. A subsequent single NGF injection did not have an additive effect. Our data suggest that neuron to microglia signaling via the CX3CL1-CX3CR1 pathway is critically involved in the initiation of non-specific, myofascial low back pain through repetitive nociceptive stimuli.
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http://dx.doi.org/10.1152/jn.00348.2020DOI Listing
February 2021

Diversity and Function of Glial Cell Types in Multiple Sclerosis.

Trends Immunol 2021 Mar 13;42(3):228-247. Epub 2021 Feb 13.

Department of Neurology, Johns Hopkins School of Medicine, Baltimore, MD, USA; Solomon H. Snyder Department of Neuroscience, Johns Hopkins School of Medicine, Baltimore, MD, USA. Electronic address:

Glial subtype diversity is an emerging topic in neurobiology and immune-mediated neurological diseases such as multiple sclerosis (MS). We discuss recent conceptual and technological advances that allow a better understanding of the transcriptomic and functional heterogeneity of oligodendrocytes (OLs), astrocytes, and microglial cells under inflammatory-demyelinating conditions. Recent single cell transcriptomic studies suggest the occurrence of novel homeostatic and reactive glial subtypes and provide insight into the molecular events during disease progression. Multiplexed RNA in situ hybridization has enabled 'mapping back' dysregulated gene expression to glial subtypes within the MS lesion microenvironment. These findings suggest novel homeostatic and reactive glial-cell-type functions both in immune-related processes and neuroprotection relevant to understanding the pathology of MS.
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http://dx.doi.org/10.1016/j.it.2021.01.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7914214PMC
March 2021

Oligodendrocyte precursor cell specification is regulated by bidirectional neural progenitor-endothelial cell crosstalk.

Nat Neurosci 2021 04 28;24(4):478-488. Epub 2021 Jan 28.

European Center for Angioscience, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany.

Neural-derived signals are crucial regulators of CNS vascularization. However, whether the vasculature responds to these signals by means of elongating and branching or in addition by building a feedback response to modulate neurodevelopmental processes remains unknown. In this study, we identified bidirectional crosstalk between the neural and the vascular compartment of the developing CNS required for oligodendrocyte precursor cell specification. Mechanistically, we show that neural progenitor cells (NPCs) express angiopoietin-1 (Ang1) and that this expression is regulated by Sonic hedgehog. We demonstrate that NPC-derived Ang1 signals to its receptor, Tie2, on endothelial cells to induce the production of transforming growth factor beta 1 (TGFβ1). Endothelial-derived TGFβ1, in turn, acts as an angiocrine molecule and signals back to NPCs to induce their commitment toward oligodendrocyte precursor cells. This work demonstrates a true bidirectional collaboration between NPCs and the vasculature as a critical regulator of oligodendrogenesis.
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http://dx.doi.org/10.1038/s41593-020-00788-zDOI Listing
April 2021

Presence of SARS-CoV-2 Transcripts in the Choroid Plexus of MS and Non-MS Patients With COVID-19.

Neurol Neuroimmunol Neuroinflamm 2021 03 27;8(2). Epub 2021 Jan 27.

From the Multiple Sclerosis Center (V.F., L.L., L. Kulsvehagen, L. Kappos), Neurologic Clinic and Policlinic, Departments of Medicine, Clinical Research, and Biomedicine, University Hospital and University of Basel, Switzerland; Department of Neurology (M.K., S.W., L.S.), Medical Faculty Mannheim, Heidelberg University, Germany; Pathology (N.D., A.T., S.F.), Institute of Medical Genetics and Pathology, University Hospital Basel, University of Basel, Switzerland; Department of Neurology (G.R., S.H.), Division of Neuropathology and Neurochemistry, Medical University Vienna, Austria; Mannheim Center for Translational Neuroscience and Institute for Innate Immunoscience (L.S.), Medical Faculty Mannheim, Heidelberg University, Germany; and Interdisciplinary Center for Neurosciences (L.S.), Heidelberg University, Germany.

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http://dx.doi.org/10.1212/NXI.0000000000000957DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7862096PMC
March 2021

Cell type-specific transcriptomics identifies neddylation as a novel therapeutic target in multiple sclerosis.

Brain 2021 03;144(2):450-461

Weill Institute for Neurosciences, Department of Neurology, University of California San Francisco, San Francisco, CA, USA.

Multiple sclerosis is an autoimmune disease of the CNS in which both genetic and environmental factors are involved. Genome-wide association studies revealed more than 200 risk loci, most of which harbour genes primarily expressed in immune cells. However, whether genetic differences are translated into cell-specific gene expression profiles and to what extent these are altered in patients with multiple sclerosis are still open questions in the field. To assess cell type-specific gene expression in a large cohort of patients with multiple sclerosis, we sequenced the whole transcriptome of fluorescence-activated cell sorted T cells (CD4+ and CD8+) and CD14+ monocytes from treatment-naive patients with multiple sclerosis (n = 106) and healthy subjects (n = 22). We identified 479 differentially expressed genes in CD4+ T cells, 435 in monocytes, and 54 in CD8+ T cells. Importantly, in CD4+ T cells, we discovered upregulated transcripts from the NAE1 gene, a critical subunit of the NEDD8 activating enzyme, which activates the neddylation pathway, a post-translational modification analogous to ubiquitination. Finally, we demonstrated that inhibition of NEDD8 activating enzyme using the specific inhibitor pevonedistat (MLN4924) significantly ameliorated disease severity in murine experimental autoimmune encephalomyelitis. Our findings provide novel insights into multiple sclerosis-associated gene regulation unravelling neddylation as a crucial pathway in multiple sclerosis pathogenesis with implications for the development of tailored disease-modifying agents.
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http://dx.doi.org/10.1093/brain/awaa421DOI Listing
March 2021

Gut microbiota-specific IgA B cells traffic to the CNS in active multiple sclerosis.

Sci Immunol 2020 11;5(53)

Department of Neurology, UCSF Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA 94158, USA.

Changes in gut microbiota composition and a diverse role of B cells have recently been implicated in multiple sclerosis (MS), a central nervous system (CNS) autoimmune disease. Immunoglobulin A (IgA) is a key regulator at the mucosal interface. However, whether gut microbiota shape IgA responses and what role IgA cells have in neuroinflammation are unknown. Here, we identify IgA-bound taxa in MS and show that IgA-producing cells specific for MS-associated taxa traffic to the inflamed CNS, resulting in a strong, compartmentalized IgA enrichment in active MS and other neuroinflammatory diseases. Unlike previously characterized polyreactive anti-commensal IgA responses, CNS IgA cross-reacts with surface structures on specific bacterial strains but not with brain tissue. These findings establish gut microbiota-specific IgA cells as a systemic mediator in MS and suggest a critical role of mucosal B cells during active neuroinflammation with broad implications for IgA as an informative biomarker and IgA-producing cells as an immune subset to harness for therapeutic interventions.
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http://dx.doi.org/10.1126/sciimmunol.abc7191DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8043673PMC
November 2020

Cortical projection neurons as a therapeutic target in multiple sclerosis.

Expert Opin Ther Targets 2020 12 8;24(12):1211-1224. Epub 2020 Nov 8.

Department of Neurology, Medical Faculty Mannheim, MCTN, Heidelberg University , Mannheim, Germany.

Introduction: Multiple sclerosis (MS) is a chronic inflammatory-demyelinating disease of the central nervous system associated with lesions of the cortical gray matter and subcortical white matter. Recently, cortical lesions have become a major focus of research because cortical pathology and neuronal damage are critical determinants of irreversible clinical progression. Recent transcriptomic studies point toward cell type-specific changes in cortical neurons in MS with a selective vulnerability of excitatory projection neuron subtypes.

Areas Covered: We discuss the cortical mapping and the molecular properties of excitatory projection neurons and their role in MS lesion pathology while placing an emphasis on their subtype-specific transcriptomic changes and levels of vulnerability. We also examine the latest magnetic resonance imaging techniques to study cortical MS pathology as a key tool for monitoring disease progression and treatment efficacy. Finally, we consider possible therapeutic avenues and novel strategies to protect excitatory cortical projection neurons. Literature search methodology: PubMed articles from 2000-2020.

Expert Opinion: Excitatory cortical projection neurons are an emerging therapeutic target in the treatment of progressive MS. Understanding neuron subtype-specific molecular pathologies and their exact spatial mapping will help establish starting points for the development of novel cell type-specific therapies and biomarkers in MS.
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http://dx.doi.org/10.1080/14728222.2020.1842358DOI Listing
December 2020

Heparin-based, injectable microcarriers for controlled delivery of interleukin-13 to the brain.

Biomater Sci 2020 Sep;8(18):4997-5004

Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Str. 6, 01069 Dresden, Germany. and School of Pharmacy and Pharmaceutical Sciences, Cardiff University, CF10 3NB, Cardiff, UK.

Interleukin-13 (IL-13) drives cells of myeloid origin towards a more anti-inflammatory phenotype, but delivery to the brain remains problematic. Herein, we show that heparin-based cryogel microcarriers load high amounts of IL-13, releasing it slowly. Intra-striatal injection of loaded microcarriers caused local up-regulation of ARG1 in myeloid cells for pro-regenerative immunomodulation in the brain.
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http://dx.doi.org/10.1039/d0bm01249aDOI Listing
September 2020

The Intratumoral Heterogeneity Reflects the Intertumoral Subtypes of Glioblastoma Multiforme: A Regional Immunohistochemistry Analysis.

Front Oncol 2020 24;10:494. Epub 2020 Apr 24.

Division of Neuropathology, Technische Universität München, München, Germany.

Glioblastoma multiforme (GBM) is the most frequent and aggressive primary brain tumor in adults. Despite extensive therapy the prognosis for GBM patients remains poor and the extraordinary therapy resistance has been attributed to intertumoral heterogeneity of glioblastoma. Different prognostic relevant GBM tumor subtypes have been identified based on their molecular profile. This approach, however, neglects the heterogeneity within individual tumors, that is, the intratumoral heterogeneity. Here, we detected the regional immunoreactivity by immunohistochemistry and immunofluorescence using nine different markers on resected GBM specimens (IDH wildtype, WHO grade IV). We found repetitive expression profiles, that could be classified into clusters. These clusters could then be assigned to five pathophysiologically relevant groups that reflect the previously described subclasses of GBM, including mesenchymal, classical, and proneural subtype. Our data indicate the presence of tumor differentiations and tumor subclasses that occur within individual tumors, and might therefore contribute to develop adapted, individual-based therapies.
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http://dx.doi.org/10.3389/fonc.2020.00494DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7193089PMC
April 2020

Glycosaminoglycan-based hydrogels with programmable host reactions.

Biomaterials 2020 01 23;228:119557. Epub 2019 Oct 23.

Leibniz-Institut für Polymerforschung Dresden e.V., Max Bergmann Center of Biomaterials Dresden, Hohe Str. 6, 01069, Dresden, Germany; Technische Universität Dresden, Center for Regenerative Therapies Dresden, Fetscherstr, 105, 01307, Dresden, Germany. Electronic address:

Glycosaminoglycan (GAG)-based, biohybrid hydrogels offering far-reaching control over their physical and biomolecular signaling properties have been successfully used in various cell and tissue culture applications. To explore the suitability of the materials for in vivo use, we herein studied the host reaction to in situ-assembling star(PEG)-GAG hydrogel variants upon subcutaneous implantation in immunocompetent C57BL/6J mice for up to 28 days. Specifically, we investigated the immune reaction and the angiogenic response to hydrogels with systematically varied cytokine functionalizations, physical network (and mechanical) properties, cell adhesiveness, and enzymatic degradability. The GAG-based hydrogel elicited only minor foreign body reaction with low immune cell infiltration and collagen deposition compared to similarly implanted medical grade silicone. Adjusting of the physical properties, biofunctionalization, and degradability allowed to program the host response from nearly no degradation and infiltration to fast integration of the gel scaffolds into the tissue within days. The results demonstrate that foreign body reactions and starPEG-GAG hydrogel tissue integration can be effectively controlled by defined adjustments of the hydrogel system, suggesting the in situ-assembling materials as safe and effective for in vivo tissue engineering applications.
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http://dx.doi.org/10.1016/j.biomaterials.2019.119557DOI Listing
January 2020

Modulation of Human CXCL12 Binding Properties to Glycosaminoglycans To Enhance Chemotactic Gradients.

ACS Biomater Sci Eng 2019 Oct 9;5(10):5128-5138. Epub 2019 Sep 9.

Universität Leipzig, Faculty of Life Sciences, Institute of Biochemistry, Brüderstrasse 34, 04103 Leipzig, Germany.

Controlled release of active biomolecules is an attractive approach to modulate chemotactic gradients and accordingly the recruitment of cells, e.g. endothelial progenitor cells to improve wound healing or stimulate angiogenesis after myocardial infarction. Here, we developed variants of hCXCL12, also named stromal cell-derived factor 1α, a chemokine that activates the CXCR4 and consequently recruits tissue specific stem and progenitor cells. hCXCL12 variants were designed to bind to glycosaminoglycans (GAGs) with different affinities in order to modulate its release. Sixteen analogs were recombinantly produced, characterized, and tested for their GAG-binding property. The most promising variants hCXCL12 K24/K27/R41/R47A and hCXCL12 Q48K were used for release studies from starPEG-heparin-hydrogels. The reduced GAG affinity led to a fast release of hCXCL12 K24/K27/R41/R47A, whereas hCXCL12 Q48K was slowly released over 2 weeks due to its increased binding strength compared to wild type hCXCL12. Migration of Jurkat cells and early endothelial progenitor cells was proven to demonstrate the applicability of the approach to endogenously CXCR4 expressing cell types. Thus, this work offers new options for enhancing chemotactic hCXCL12 gradients by a combination of native and modified hCXCL12 variants to improve and prolong the recruitment of CXCR4-positive stem and progenitor cells to injured sites.
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http://dx.doi.org/10.1021/acsbiomaterials.9b01139DOI Listing
October 2019

Neuronal vulnerability and multilineage diversity in multiple sclerosis.

Nature 2019 09 17;573(7772):75-82. Epub 2019 Jul 17.

Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA, USA.

Multiple sclerosis (MS) is a neuroinflammatory disease with a relapsing-remitting disease course at early stages, distinct lesion characteristics in cortical grey versus subcortical white matter and neurodegeneration at chronic stages. Here we used single-nucleus RNA sequencing to assess changes in expression in multiple cell lineages in MS lesions and validated the results using multiplex in situ hybridization. We found selective vulnerability and loss of excitatory CUX2-expressing projection neurons in upper-cortical layers underlying meningeal inflammation; such MS neuron populations exhibited upregulation of stress pathway genes and long non-coding RNAs. Signatures of stressed oligodendrocytes, reactive astrocytes and activated microglia mapped most strongly to the rim of MS plaques. Notably, single-nucleus RNA sequencing identified phagocytosing microglia and/or macrophages by their ingestion and perinuclear import of myelin transcripts, confirmed by functional mouse and human culture assays. Our findings indicate lineage- and region-specific transcriptomic changes associated with selective cortical neuron damage and glial activation contributing to progression of MS lesions.
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http://dx.doi.org/10.1038/s41586-019-1404-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6731122PMC
September 2019

Single-Cell High-Throughput Technologies in Cerebrospinal Fluid Research and Diagnostics.

Front Immunol 2019 11;10:1302. Epub 2019 Jun 11.

Department of Neurology, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany.

High-throughput single-cell technologies have recently emerged as essential tools in biomedical research with great potential for clinical pathology when studying liquid and solid biopsies. We provide an update on current single-cell methods in cerebrospinal fluid research and diagnostics, focusing on high-throughput cell-type specific proteomic and genomic technologies. Proteomic methods comprising flow cytometry and mass cytometry as well as genomic approaches including immune cell repertoire and single-cell transcriptomic studies are critically reviewed and future directions discussed.
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http://dx.doi.org/10.3389/fimmu.2019.01302DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6579921PMC
July 2020

Single-cell genomics identifies cell type-specific molecular changes in autism.

Science 2019 05;364(6441):685-689

Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, CA 94143, USA.

Despite the clinical and genetic heterogeneity of autism, bulk gene expression studies show that changes in the neocortex of autism patients converge on common genes and pathways. However, direct assessment of specific cell types in the brain affected by autism has not been feasible until recently. We used single-nucleus RNA sequencing of cortical tissue from patients with autism to identify autism-associated transcriptomic changes in specific cell types. We found that synaptic signaling of upper-layer excitatory neurons and the molecular state of microglia are preferentially affected in autism. Moreover, our results show that dysregulation of specific groups of genes in cortico-cortical projection neurons correlates with clinical severity of autism. These findings suggest that molecular changes in upper-layer cortical circuits are linked to behavioral manifestations of autism.
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http://dx.doi.org/10.1126/science.aav8130DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7678724PMC
May 2019

Granular hydrogels: emergent properties of jammed hydrogel microparticles and their applications in tissue repair and regeneration.

Curr Opin Biotechnol 2019 12 24;60:1-8. Epub 2018 Nov 24.

Department of Biomedical Engineering, Duke University, United States; Department of Dermatology, Duke University, United States; Department of Neurology, Duke University, United States. Electronic address:

Granular hydrogels are emerging as a versatile and effective platform for tissue engineered constructs in regenerative medicine. The hydrogel microparticles (HMPs) that compose these materials exhibit particle jamming above a minimum packing fraction, which results in a bulk, yet dynamic, granular hydrogel scaffold. These injectable, microporous scaffolds possess self-assembling, shear-thinning, and self-healing properties. Recently, they have been utilized as cell cultures platforms and extracellular matrix mimics with remarkable success in promoting cellular infiltration and subsequent tissue remodeling in vivo. Furthermore, the modular nature of granular hydrogels accommodates heterogeneous HMP assembly, where varying HMPs have been fabricated to target distinct biological processes or deliver unique cargo. Such multifunctional materials offer enormous potential for capturing the structural and biofunctional complexity observed in native human tissue.
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http://dx.doi.org/10.1016/j.copbio.2018.11.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6534490PMC
December 2019

Personality Traits in Patients with Neuroepithelial Tumors - A Prospective Study.

Sci Rep 2018 11 19;8(1):17055. Epub 2018 Nov 19.

Neurochirurgische Klinik und Poliklinik, Klinikum rechts der Isar, Technische Universität München, Ismaninger Str. 22, 81675, München, Germany.

Aim of this study was to analyze personality traits in patients with neuroepithelial brain tumors. Personality alteration is a common feature in brain tumor patients, but not much is known about associations between specific personality changes and brain tumors. We assessed potential factors influencing personality such as tumor location, tumor grade and tumor volume. Mini-mental state examination (MMSE), Beck's Depression Inventory II (BDI-II), and the NEO Five-Factor Inventory (NEO-FFI) for the five factors of personality were acquired. Patients had lower scores regarding the factor openness and higher scores regarding the BDI-II compared to the norm population. No significant influencing factors (tumor entity, location) were found regarding personality traits. Neuroticism was associated with depression, whereas extraversion showed an opposed association. Patients with intrinsic brain tumors have differences in personality traits compared to the control population, with an emphasis on the factor openness. No significant confounding factors like tumor grade, entity, or location were found for personality traits.
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http://dx.doi.org/10.1038/s41598-018-34980-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6243000PMC
November 2018

Thrombus Permeability in Admission Computed Tomographic Imaging Indicates Stroke Pathogenesis Based on Thrombus Histology.

Stroke 2018 11;49(11):2674-2682

From the Departments of Neuroradiology (M.B., B.F., C.M., S.M., D.H., M.L., C.Z., T.B.-B.), Klinikum rechts der Isar, Technical University of Munich, Germany.

Background and Purpose- Intracranial thrombi can be characterized according to their permeability as measured by contrast agent penetration. Thrombus composition and its associated pathogenesis are important factors affecting treatment and secondary prevention. We aimed to explore the histopathologic factors explaining the heterogeneity of thrombus permeability measures and evaluated potential correlations with stroke pathogenesis. Methods- Thrombus densities were measured in thin-slice noncontrast computed tomography and automatically aligned computed tomographic angiography images of 133 patients with large-vessel occlusions of the middle cerebral artery. Change in thrombus attenuation (Δ) and corrected void fraction (ε; attenuation increase corrected for contralateral artery densities) were calculated. First, these thrombus perviousness measures were correlated with histological thrombus components (especially fractions of fibrin-platelet accumulation and red blood cells) and stroke pathogenesis (n=32). For validation, an association between perviousness and pathogenesis was assessed in a second, independent cohort (n=101). Results- Thrombus perviousness estimates were correlated with both fibrin/platelets fractions (Δ: r=0.43, P=0.016/ε: r=0.45, P=0.01) and inversely with red blood cells counts (Δ: r=-0.46, P=0.01/ε: r=-0.49, P=0.006). In the first cohort, Δ was substantially higher in samples from patients with cardioembolic stroke pathogenesis as compared with noncardioembolic-derived thrombi ( P=0.026). In the validation cohort, thrombus perviousness measures differed significantly between cardioembolic (Δ: median [ interquartile range]=12.53 [8.70-17.90]; ε: median [interquartile range]=0.054 [0.036-0.082]) and noncardioembolic thrombi (Δ: median [interquartile range]=3.2 [2.17-6.44], P<0.001; ε: median [interquartile range]=0.020 [0.011-0.027], P<0.001) and were associated with pathogenesis (Δ: β=0.45, P=0.016/ε: β=83.6, P=0.013) in a binary logistic regression model. Conclusions- Permeable thrombi showed a strong correlation with lower fractions of red blood cells counts and more fibrin/platelets conglomerations, concurrent with an association with cardioembolic origin. This novel information about thrombus perviousness may be valuable as a new and simple to acquire imaging marker for identifying stroke pathogenesis using early and readily available imaging.
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http://dx.doi.org/10.1161/STROKEAHA.118.021873DOI Listing
November 2018

Oligodendrocyte-encoded Kir4.1 function is required for axonal integrity.

Elife 2018 09 11;7. Epub 2018 Sep 11.

Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, California, United States.

Glial support is critical for normal axon function and can become dysregulated in white matter (WM) disease. In humans, loss-of-function mutations of which encodes the inward-rectifying potassium channel KIR4.1, causes seizures and progressive neurological decline. We investigated Kir4.1 functions in oligodendrocytes (OLs) during development, adulthood and after WM injury. We observed that Kir4.1 channels localized to perinodal areas and the inner myelin tongue, suggesting roles in juxta-axonal K removal. Conditional knockout (cKO) of OL- resulted in late onset mitochondrial damage and axonal degeneration. This was accompanied by neuronal loss and neuro-axonal dysfunction in adult OL- cKO mice as shown by delayed visual evoked potentials, inner retinal thinning and progressive motor deficits. Axon pathologies in OL- cKO were exacerbated after WM injury in the spinal cord. Our findings point towards a critical role of OL-Kir4.1 for long-term maintenance of axonal function and integrity during adulthood and after WM injury.
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http://dx.doi.org/10.7554/eLife.36428DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6167053PMC
September 2018

In situ-forming, cell-instructive hydrogels based on glycosaminoglycans with varied sulfation patterns.

Biomaterials 2018 10 30;181:227-239. Epub 2018 Jul 30.

Leibniz Institute of Polymer Research Dresden (IPF), Max Bergmann Center of Biomaterials Dresden (MBC), Hohe Str. 6, 01069 Dresden, Germany. Electronic address:

Glycosaminoglycan (GAG)-based hydrogels were proven highly effective to direct cell fate decisions by modulating the administration of cytokines. The sulfation pattern of the GAG component critically controls its affinity to proteins and thus governs the release of cytokines from GAG-containing gel systems. To apply this principle in the design of in situ assembling materials suitable for cell embedding and injection into tissues, we developed a platform of bio-orthogonally crosslinked star-shaped poly(ethylene glycol) (starPEG)-GAG hydrogels that display variable GAG sulfation patterns. Combining rational design for tuning the hydrogel network properties and a reaction-diffusion model for predicting transport processes within the matrices, we exemplarily applied the resulting materials for tailoring morphogenic and chemotactic gradients of platelet-derived growth factor-BB (PDGF-BB) in 3D. Conditions identified with this approach were demonstrated to effectively control the fate and morphogenesis of embedded mesenchymal stem cells (MSCs). Adjusting the sulfation patterns of glycosamnioglycans used in the preparation of in situ forming hydrogels is thus concluded to create new powerful options for modulating biomolecular signals in cell fate control, paving the way for advanced 3D cultures and precision tissue engineering.
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http://dx.doi.org/10.1016/j.biomaterials.2018.07.056DOI Listing
October 2018

Kir4.1-Dependent Astrocyte-Fast Motor Neuron Interactions Are Required for Peak Strength.

Neuron 2018 04 5;98(2):306-319.e7. Epub 2018 Apr 5.

Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA 94143, USA; Departments of Pediatrics and Neurosurgery, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Paediatrics and Wellcome Trust-MRC Cambridge Stem Cell Institute, University of Cambridge, Cambridge CB20QQ, UK. Electronic address:

Diversified neurons are essential for sensorimotor function, but whether astrocytes become specialized to optimize circuit performance remains unclear. Large fast α-motor neurons (FαMNs) of spinal cord innervate fast-twitch muscles that generate peak strength. We report that ventral horn astrocytes express the inward-rectifying K channel Kir4.1 (a.k.a. Kcnj10) around MNs in a VGLUT1-dependent manner. Loss of astrocyte-encoded Kir4.1 selectively altered FαMN size and function and led to reduced peak strength. Overexpression of Kir4.1 in astrocytes was sufficient to increase MN size through activation of the PI3K/mTOR/pS6 pathway. Kir4.1 was downregulated cell autonomously in astrocytes derived from amyotrophic lateral sclerosis (ALS) patients with SOD1 mutation. However, astrocyte Kir4.1 was dispensable for FαMN survival even in the mutant SOD1 background. These findings show that astrocyte Kir4.1 is essential for maintenance of peak strength and suggest that Kir4.1 downregulation might uncouple symptoms of muscle weakness from MN cell death in diseases like ALS.
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http://dx.doi.org/10.1016/j.neuron.2018.03.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5919779PMC
April 2018

Artificial Stroke Clots: How Wide is the Gap to the Real World?

World Neurosurg 2018 Feb 26;110:e90-e99. Epub 2017 Oct 26.

Department of Neuroradiology, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany.

Objective: Especially since the establishment of mechanical thrombectomy as part of standard stroke therapy, artificial thrombi have become important in the training of interventionalists as well as for the development and testing of devices. So far, these in vitro clots have lacked direct comparisons with ex vivo thrombi. We therefore compared the histologic appearance of dynamically produced clots with that of stroke thrombi acquired during mechanical recanalization.

Methods: Thrombi of 145 consecutive patients with stroke with large-vessel occlusions were histologically compared with 10 artificial clots, dynamically created from human blood and pig's blood using a Chandler loop system. Quantified FP/RBC ratios (fibrin/platelets divided by red blood cell fraction) and white blood cell (WBC) fractions were identified and compared between artificial (human and pig) and ex vivo thrombi obtained from patients with various stroke causes.

Results: There were no significant differences in the analysis of FP/RBC ratios between artificial thrombi and ex vivo thrombi (P = 0.42) or in the more precise analyses considering etiologic subgroups. Distinct differences were observed for the WBC fraction, with lower values in artificial thrombi (median, 1.34%) than in ex vivo thrombi (median, 5%) (P < 0.001).

Conclusions: The main clot components, FP and RBC, are presumably the most influential factors for clot stability and mechanical resistance. Similarities between artificially generated and ex vivo stroke clots (and when considering different stroke subgroups) support the usefulness of these artificial thrombi in the pre-evaluation of thrombus extraction devices and as appropriate training material.
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http://dx.doi.org/10.1016/j.wneu.2017.10.090DOI Listing
February 2018

Impact of histological thrombus composition on preinterventional thrombus migration in patients with acute occlusions of the middle cerebral artery.

Interv Neuroradiol 2018 Feb 23;24(1):70-75. Epub 2017 Oct 23.

1 Department of Neuroradiology, 27190 Klinikum rechts der Isar, Technical University of Munich , Munich, Germany.

Purpose The occurrence of thrombus migration (TM) in middle cerebral arteries (MCAs) prior to mechanical thrombectomy (MT) in patients suffering from acute ischemic strokes is a crucial aspect as TM is associated with lower rates of complete reperfusion and worse clinical outcomes. In this study, we sought to clarify whether histological thrombus composition influences TM. Methods We included 64 patients with acute MCA occlusions who had undergone MT. In 11 of the cases (17.2%) we identified TM prior to the interventions. The extracted clots were collected and histologically examined. The hematoxylin and eosin-stained specimens were quantitatively analyzed in terms of the relative fractions of the main constituents (red and white blood cells and fibrin/platelets). The histologic patterns were correlated with the occurrence of TM. Results Patients in whom TM could be observed were more often treated in a drip-and-ship fashion (90.9% vs 41.5%, p = 0.003). Stroke etiology did not differ between migrated and stable thrombi. A weak tendency for higher RBC and lower F/P content could be observed in thrombi that had migrated when compared with stable thrombi (RBC: median 41% vs 37%, p = 0.022 and F/P: median 54% vs 57%, p = 0.024). When using a cut-off of 60% RBC content for the definition of RBC-rich thrombi, a higher portion of RBC-rich thrombi could be identified in the migrated group as opposed to the stable group (36.4% vs 5.7%, p = 0.003). Conclusion Preinterventional TM may be influenced by the histological thrombus composition in a way that RBC-rich thrombi are more prone to migrate.
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http://dx.doi.org/10.1177/1591019917733733DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5772536PMC
February 2018

Reactive astrocyte COX2-PGE2 production inhibits oligodendrocyte maturation in neonatal white matter injury.

Glia 2017 12 30;65(12):2024-2037. Epub 2017 Aug 30.

Department of Pediatrics and Division of Neonatology.

Inflammation is a major risk factor for neonatal white matter injury (NWMI), which is associated with later development of cerebral palsy. Although recent studies have demonstrated maturation arrest of oligodendrocyte progenitor cells (OPCs) in NWMI, the identity of inflammatory mediators with direct effects on OPCs has been unclear. Here, we investigated downstream effects of pro-inflammatory IL-1β to induce cyclooxygenase-2 (COX2) and prostaglandin E2 (PGE2) production in white matter. First, we assessed COX2 expression in human fetal brain and term neonatal brain affected by hypoxic-ischemic encephalopathy (HIE). In the developing human brain, COX2 was expressed in radial glia, microglia, and endothelial cells. In human term neonatal HIE cases with subcortical WMI, COX2 was strongly induced in reactive astrocytes with "A2" reactivity. Next, we show that OPCs express the EP1 receptor for PGE2, and PGE2 acts directly on OPCs to block maturation in vitro. Pharmacologic blockade with EP1-specific inhibitors (ONO-8711, SC-51089), or genetic deficiency of EP1 attenuated effects of PGE2. In an IL-1β-induced model of NWMI, astrocytes also exhibit "A2" reactivity and induce COX2. Furthermore, in vivo inhibition of COX2 with Nimesulide rescues hypomyelination and behavioral impairment. These findings suggest that neonatal white matter astrocytes can develop "A2" reactivity that contributes to OPC maturation arrest in NWMI through induction of COX2-PGE2 signaling, a pathway that can be targeted for neonatal neuroprotection.
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http://dx.doi.org/10.1002/glia.23212DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5753598PMC
December 2017

Head and neck giant cell arteritis: an autoimmune disease with many faces.

Acta Otolaryngol 2017 Sep 25;137(9):986-991. Epub 2017 Apr 25.

a Department of Otolaryngology - Head and Neck Surgery , Klinikum rechts der Isar, Technical University of Munich , Munich , Germany.

Conclusion: A high rate of infrequent presentations of giant cell arteritis were seen in the ENT department and should be anticipated as a differential diagnosis in every older patient with odynophagia with high CRP values without cause in thorough ENT examination.

Objective: To describe the clinical manifestation of head and neck giant cell arteritis and to derive a diagnostic pathway covering atypical cases.

Method: Single-center, retrospective analysis of cases with GCA in the head and neck region (HN-GCA) (2002-2012) to describe the clinical presentation and to derive a diagnostic pathway covering manifestations presenting to an ENT department.

Results: Sixty-five patients were newly diagnosed with HN-GCA in the department of otolaryngology, ophthalmology and neurology. The most frequent symptoms were loss of vision (83%) and new onset headache (63%). Eight patients (12%) presented with infrequent manifestations, predominantly in the department of otorhinolaryngology. The most common atypical presentation (50%) was odynophagia in conjunction with high CRP values misleading to an infectious cause and delaying diagnosis. A diagnostic pathway for GCA was derived based on the ACR classification criteria and the clinical findings.
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http://dx.doi.org/10.1080/00016489.2017.1314010DOI Listing
September 2017

Glycosaminoglycan-based hydrogels capture inflammatory chemokines and rescue defective wound healing in mice.

Sci Transl Med 2017 04;9(386)

Collaborative Research Center (SFB-TR67) "Functional Biomaterials for Controlling Healing Processes in Bone and Skin-From Material Science to Clinical Application," Leipzig and Dresden, Germany.

Excessive production of inflammatory chemokines can cause chronic inflammation and thus impair cutaneous wound healing. Capturing chemokine signals using wound dressing materials may offer powerful new treatment modalities for chronic wounds. Here, a modular hydrogel based on end-functionalized star-shaped polyethylene glycol (starPEG) and derivatives of the glycosaminoglycan (GAG) heparin was customized for maximal chemokine sequestration. The material is shown to effectively scavenge the inflammatory chemokines MCP-1 (monocyte chemoattractant protein-1), IL-8 (interleukin-8), and MIP-1α (macrophage inflammatory protein-1α) and MIP-1β (macrophage inflammatory protein-1β) in wound fluids from patients suffering from chronic venous leg ulcers and to reduce the migratory activity of human monocytes and polymorphonuclear neutrophils. In an in vivo model of delayed wound healing (db/db mice), starPEG-GAG hydrogels outperformed the standard-of-care product Promogran with respect to reduction of inflammation, as well as increased granulation tissue formation, vascularization, and wound closure.
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http://dx.doi.org/10.1126/scitranslmed.aai9044DOI Listing
April 2017

The CD31 molecule: a possible neuroprotective agent in acute ischemic stroke?

Thromb J 2017 13;15:11. Epub 2017 Apr 13.

Department of Neurology, University Hospital Rechts der Isar, Technical University Munich, Ismaninger Str. 22, 81675 Munich, Germany.

Background: The transmembrane receptor molecule CD31 is known to have immunomodulatory functions, suggesting a possible neuroprotective effect in the context of acute ischemic stroke by restricting an over-activation of secondary immunological processes. This study examines the density of CD31 cells in mechanically extracted thrombi of stroke patients with the aim to test whether the occurrence of CD31 cells was associated with a beneficial clinical outcome in those patients.

Methods: Thrombi of 122 consecutive patients with large anterior circulation stroke were collected during intracranial mechanical recanalization. Out of these, 86 immunostained specimens of adequate quality could be analysed. The density of CD31 cells was quantified and compared with clinical outcome data of the affected patients.

Results: The density of CD31 cells was positively related to early patient improvement (ΔNIHSS,  = 0.283,  = 0,012) with an even clearer relationship after exclusion of patients who died in the early hospital phase ( = 0.371,  = 0.001). This finding stayed stable also in the multivariate analysis after corrrection for other outcome-influencing factors ( = 0.049).

Conclusion: This study shows a stable relation between CD31 cells and early clinical improvement of patients with acute ischemic stroke. This finding is in line with recent reports showing immunomodulatory and potential neuroprotective effects of CD31, suggesting that CD31 may be a promising neuroprotective agent in stroke patients.
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http://dx.doi.org/10.1186/s12959-017-0134-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5390341PMC
April 2017

Olig1 is required for noggin-induced neonatal myelin repair.

Ann Neurol 2017 Apr;81(4):560-571

Department of Pediatrics, Eli and Edythe Broad Center for Stem Cell Research and Regeneration Medicine, University of California, San Francisco, San Francisco, CA.

Objective: Neonatal white matter injury (NWMI) is a lesion found in preterm infants that can lead to cerebral palsy. Although antagonists of bone morphogenetic protein (BMP) signaling, such as Noggin, promote oligodendrocyte precursor cell (OPC) production after hypoxic-ischemic (HI) injury, the downstream functional targets are poorly understood. The basic helix-loop-helix protein, oligodendrocyte transcription factor 1 (Olig1), promotes oligodendrocyte (OL) development and is essential during remyelination in adult mice. Here, we investigated whether Olig1 function is required downstream of BMP antagonism for response to injury in the neonatal brain.

Methods: We used wild-type and Olig1-null mice subjected to neonatal stroke and postnatal neural progenitor cultures, and we analyzed Olig1 expression in human postmortem samples from neonates that suffered HI encephalopathy (HIE).

Results: Olig1-null neonatal mice showed significant hypomyelination after moderate neonatal stroke. Surprisingly, damaged white matter tracts in Olig1-null mice lacked Olig2 OPCs, and instead proliferating neuronal precursors and GABAergic interneurons were present. We demonstrate that Noggin-induced OPC production requires Olig1 function. In postnatal neural progenitors, Noggin governs production of OLs versus interneurons through Olig1-mediated repression of Dlx1/2 transcription factors. Additionally, we observed that Olig1 and the BMP signaling effector, phosphorylated SMADs (Sma- and Mad-related proteins) 1, 5, and 8, were elevated in the subventricular zone of human infants with HIE compared to controls.

Interpretation: These findings indicate that Olig1 has a critical function in regulation of postnatal neural progenitor cell production in response to Noggin. Ann Neurol 2017;81:560-571.
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http://dx.doi.org/10.1002/ana.24907DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5401646PMC
April 2017

Neurotoxic reactive astrocytes are induced by activated microglia.

Nature 2017 01 18;541(7638):481-487. Epub 2017 Jan 18.

Department of Neurobiology, Stanford University, School of Medicine, Stanford, California 94305, USA.

Reactive astrocytes are strongly induced by central nervous system (CNS) injury and disease, but their role is poorly understood. Here we show that a subtype of reactive astrocytes, which we termed A1, is induced by classically activated neuroinflammatory microglia. We show that activated microglia induce A1 astrocytes by secreting Il-1α, TNF and C1q, and that these cytokines together are necessary and sufficient to induce A1 astrocytes. A1 astrocytes lose the ability to promote neuronal survival, outgrowth, synaptogenesis and phagocytosis, and induce the death of neurons and oligodendrocytes. Death of axotomized CNS neurons in vivo is prevented when the formation of A1 astrocytes is blocked. Finally, we show that A1 astrocytes are abundant in various human neurodegenerative diseases including Alzheimer's, Huntington's and Parkinson's disease, amyotrophic lateral sclerosis and multiple sclerosis. Taken together these findings help to explain why CNS neurons die after axotomy, strongly suggest that A1 astrocytes contribute to the death of neurons and oligodendrocytes in neurodegenerative disorders, and provide opportunities for the development of new treatments for these diseases.
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http://dx.doi.org/10.1038/nature21029DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5404890PMC
January 2017

StarPEG-Heparin Hydrogels to Protect and Sustainably Deliver IL-4.

Adv Healthc Mater 2016 12 8;5(24):3157-3164. Epub 2016 Nov 8.

Leibniz Institute of Polymer Research Dresden (IPF), Max Bergmann Center of Biomaterials Dresden (MBC), Hohe Str. 6, 01069, Dresden, Germany.

A major limitation for the therapeutic applications of cytokines is their short half-life time. Glycosaminoglycans (GAGs), known to complex and stabilize cytokines in vivo, are therefore used to form 3D-biohybrid polymer networks capable of aiding the effective administration of Interleukin-4, a key regulator of the inflammatory response. Mimicking the in vivo situation of a protease-rich inflammatory milieu, star-shaped poly(ethylene glycol) (starPEG)-heparin hydrogels and starPEG reference hydrogels without heparin are loaded with Interleukin-4 and subsequently exposed to trypsin as a model protease. Heparin-containing hydrogels retain significantly higher amounts of the Interleukin-4 protein thus exhibiting a significantly higher specific activity than the heparin-free controls. StarPEG-heparin hydrogels are furthermore shown to enable a sustained delivery of the cytokine for time periods of more than two weeks. Primary murine macrophages adopt a wound healing supporting (M2) phenotype when conditioned with Interleukin-4 releasing starPEG-heparin hydrogels. The reported results suggest that GAG-based hydrogels offer valuable options for the effective administration of cytokines in protease-rich proinflammatory milieus such as chronic wounds of diabetic patients.
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http://dx.doi.org/10.1002/adhm.201600797DOI Listing
December 2016