Biology subjects

Kollias, G.

Publications and source records attributed to Kollias, G..

10 recordsLinked to original sources

bioRxiv2023

Cellular complexity and crosstalk in murine TNF-dependent ileitis: Different fibroblast subsets propel spatially defined ileal inflammation through TNFR1 signalling

Crohns disease represents a persistent inflammatory disorder primarily affecting the terminal ileum. Through the application of single-cell RNA sequencing, we unveil the intricate cellular complexities within murine TNF-dependent ileitis, developing in Tnf{Delta}ARE mice. Detailed immune cell analysis highlights B cell expansion, T cell effector reprogramming, and macrophage lineage shifts during inflammation. Focusing on stromal cells, we reveal a strong pro-inflammatory character, acquired by all fibroblast subsets, which exhibit complex communication patterns with the infiltrating immune and surrounding stromal cells. Interestingly, we identify that Tnf{Delta}ARE-induced ileitis is initiated in the lamina propria via TNFR1 pathway activation in villus-associated fibroblasts (Telocytes and Pdgfralow cells). Furthermore, we unveil separate spatial subsets of fibroblasts acting as exclusive responders to TNF, each orchestrating inflammation in different intestinal layers. Additionally, manipulating the Tnfrsf1a gene exclusively in fibroblast subsets suggests that inflammation is initiated by telocytes and Pdgfralow cells, while trophocytes drive its progression. This introduces novel evidence of spatial regulation of inflammation by fibroblast subsets, inciting and advancing disease in different layers of the gut. These findings underscore the pivotal role of fibroblasts in the inception and advancement of ileitis, proposing that targeting different fibroblast populations could impede the disease development and chronicity of inflammation.

cell biology↗

bioRxiv2023

Dysregulation of γδ intraepithelial lymphocytes precedes Crohn's disease-like ileitis

Intraepithelial lymphocytes expressing the {gamma}{delta} T cell receptor ({gamma}{delta} IELs) provide immunosurveillance of the intestinal barrier. Interestingly, {gamma}{delta} IEL number is reduced in patients with active Crohns disease (CD). Here, we report an underappreciated role for {gamma}{delta} IELs in maintaining mucosal tolerance during the onset and progression of CD-like ileitis using the TNF{Delta}ARE/+ mouse model. Decreased epithelial HNF4G/BTNL expression is followed by a loss of ileal {gamma}{delta} IELs and impaired barrier surveillance prior to the histological onset of disease. A reduction of immunoregulatory CD39+ {gamma}{delta} IELs coincides with the influx of immature, peripheral CD39- {gamma}{delta} T cells into the epithelium leading to an expansion of induced IELs, while an earlier depletion of {gamma}{delta} IELs correlates with accelerated onset of ileal inflammation. Our findings identify multiple layers of {gamma}{delta} IEL dysregulation prior to ileitis development indicating that the loss of tissue-resident immunoregulatory {gamma}{delta} IELs may contribute to the initiation of ileal CD.

immunology↗

bioRxiv2022

SCALA: A web application for multimodal analysis of single cell next generation sequencing data

Analysis and interpretation of high-throughput transcriptional and chromatin accessibility data at single cell resolution are still open challenges in the biomedical field. In this article, we present SCALA, a bioinformatics tool for analysis and visualization of single cell RNA sequencing (scRNA-seq) and Assay for Transposase-Accessible Chromatin using sequencing (ATAC-seq) datasets. SCALA combines standard types of analysis by integrating multiple software packages varying from quality control to identification of distinct cell population and cell states. Additional analysis options enable functional enrichment, cellular trajectory inference, ligand-receptor analysis and regulatory network reconstruction. SCALA is fully parameterizable at every step of the analysis, presenting data in tabular format and produces publication-ready 2D and 3D visualizations including heatmaps, barcharts, scatter, violin and volcano plots. We demonstrate the functionality of SCALA through two use-cases related to TNF-driven arthritic mice, handling data from both scRNA-seq and scATAC-seq experiments. SCALA is mainly developed in R, Shiny and JavaScript and is available as a web application at http://scala.pavlopouloslab.info or https://scala.fleming.gr.

bioinformatics↗

bioRxiv2022

Upregulation of CD55 complement regulator in distinct PBMC subpopulations of COVID-19 patients is associated with suppression of interferon responses.

Complement activation has been verified in COVID-19 patients by both increased serum levels of complement factors C3a and C5b-9 and increased complement deposition at the tissue levels. Complement regulatory proteins (CRPs) CD55, CD46, CD59 and CR1 act to control complement overactivation and eliminate complement deposition and cell lysis. The aim of the study was to investigate the expression of CRPs in COVID-19 in order to identify potential dysregulated expression patterns of CRPs and address whether these may contribute to disease pathogenesis. Single cell RNA-sequencing (scRNA-seq) analysis performed on isolated PBMCs revealed an increase of CD55 expression in severe and critical COVID-19 patients compared to healthy controls. This increase was also detected upon integrated subclustering analysis of the monocyte, T cell and B cell populations. Flow cytometric analysis verified the distinct pattern of upregulated CD55 expression in monocyte and T cell sub populations of severe COVID-19 patients. This upregulation was associated with decreased expression of interferon stimulated genes (ISGs) in patients with severe COVID-19 suggesting a potential suppressor effect of CD55 on interferon responses. The present study identifies a COVID-19 specific CD55 expression pattern in PBMC subpopulations that coincides with reduced interferon responses thus indicating that the complement regulator CD55 may contribute to COVID-19 pathogenesis.

immunology↗

bioRxiv2022

Repurposing of Amisulpride, a known antipsychotic drug, to target synovial fibroblasts activation in arthritis.

Synovial Fibroblasts (SFs) are key pathogenic drivers in arthritis and their in vivo activation by TNF is sufficient to orchestrate full arthritic pathogenesis in animal models. TNF blockade has been efficacious for a large percentage of Rheumatoid Arthritis (RA) patients, although characterized by a plethora of side effects. Novel therapeutic discoveries remain however challenging, especially in optimizing drug safety, side effects, longer-term responses, costs and administration routes. Aiming to find new potent therapeutics, we applied the L1000CDS2 search engine, in order to identify compounds that could potentially reverse the pathogenic expression signature of arthritogenic SFs, derived from the human TNF transgenic mouse model (hTNFtg). We identified a neuroleptic drug, namely Amisulpride, which was validated to reduce SFs inflammatory potential while decreasing the clinical score of hTNFtg polyarthritis. Notably, we found that Amisulpride did not exert its biological activities through its known targets Dopamine receptors 2 and 3 and Serotonin Receptor 7, nor through TNF-TNFRI binding inhibition. By applying a click chemistry approach, novel potential targets of Amisulpride were identified, which were further validated to repress hTNFtg SFs inflammatory potential in vitro (Ascc3 and Sec62), while phosphoproteomics analysis revealed important fibroblast activation pathways, such as adhesion, to be altered upon treatment. Our data support that Amisulpride could provide an additive beneficial effect to patients suffering from RA and comorbid dysthymia, as it may reduce SFs pathogenicity in parallel with its anti-depressive activity. Importantly, Amisulpride may also serve as a "lead" compound for the development of novel, more potent therapeutics against chronic inflammatory diseases.

pharmacology and toxicology↗

bioRxiv2022

miR-221/222 drive synovial fibroblast expansion and pathogenesis of TNF-mediated arthritis

MicroRNAs (miRNAs) constitute fine tuners of gene expression and are implicated in a variety of diseases spanning from inflammation to cancer. miRNA expression is deregulated in rheumatoid arthritis (RA), however, their specific role in key arthritogenic cells such as the synovial fibroblast (SF) remains elusive. We have shown in the past that the expression of the miR-221/222 cluster is upregulated in RA SFs. Here, we demonstrate that miR-221/222 activation is downstream of major inflammatory cytokines, such as TNF and IL-1{beta}, which promote miR-221/222 expression independently. miR-221/222 expression in SFs from the huTNFtg mouse model of arthritis correlates with disease progression. Targeted transgenic overexpression of miR-221/222 in SFs of the huTNFtg mouse model led to further expansion of synovial fibroblasts and disease exacerbation. miR-221/222 overexpression altered the transcriptional profile of SFs igniting pathways involved in cell cycle progression and ECM regulation. Validated targets of miR-221/222 included p27 and p57 cell cycle inhibitors, as well as Smarca1 (a chromatin remodeling component). In contrast, complete genetic ablation of miR-221/222 in arthritic mice led to decreased proliferation of fibroblasts, reduced synovial expansion and attenuated disease. scATAC-seq data analysis revealed increased miR-221/222 gene activity in the pathogenic and activated clusters of the intermediate and lining compartment. Taken together, our results establish an SF-specific pathogenic role of the miR-221/222 cluster in arthritis and suggest that its therapeutic targeting in specific subpopulations should inform the design of novel fibroblast-targeted therapies for human disease.

cell biology↗

bioRxiv2021

Single-cell chromatin and transcriptome dynamics of Synovial Fibroblasts transitioning from homeostasis to pathology in modelled TNF-driven arthritis

Synovial fibroblasts (SFs) are specialized cells of the synovium that provide nutrients and lubricants for the maintenance of proper function of diarthrodial joints. Chronic TNF signals are known to trigger activation of SFs and orchestration of arthritic pathology via proinflammatory effector functions, secretion of cartilage degrading proteases and promotion of osteolysis. We performed single-cell (sc) profiling of SFs transcriptome by RNA-sequencing (scRNA-seq) and of chromatin accessibility by scATAC-seq in normal mouse SFs and SFs derived from early and advanced TNF-driven arthritic disease. We describe here distinct subsets of SFs in the homeostatic synovium, serving diverse functions such as chondro- and osteogenesis, tissue repair and immune regulation. Strikingly, development of spontaneous arthritis by transgenic TNF overexpression primes the emergence of distinct pathology-associated SF subtypes. We reveal 7 constitutive and 2 disease-specific SF subtypes. The latter emerge in the early stage, expand in late disease and are localized in areas at the interface between the invasive pannus and the articular bone. The associated transcription profiles are characterized by enhanced inflammatory responses, promigratory behaviour, neovascularization and collagen metabolic processes. Temporal reconstruction of transcriptomic events indicated which specific sublining cells may function as progenitors at the root of trajectories leading to intermediate subpopulations and culminating to a destructive lining inflammatory identity. Integrated analysis of chromatin accessibility and transcription changes revealed key transcription factors such as Bach and Runx1 to drive arthritogenesis. Parallel analysis of human arthritic SF data showed highly conserved core regulatory and transcriptional programs between the two species. Therefore, our study dissects the dynamic SF landscape in TNF-mediated arthritis and sets the stage for future investigations that might address the functions of specific SF subpopulations to understand joint pathophysiology and combat chronic inflammatory and destructive arthritic diseases.

cell biology↗

bioRxiv2021

Col6a1+/CD201+ telocytes regulate intestinal morphogenesis and homeostasis

Intestinal mesenchymal cells encompass multiple subsets, whose origins, functions, and pathophysiological importance are still not clear. Here, we used the Col6a1Cre mouse, which targets telocytes and perivascular cells that can be further distinguished by the combination of the CD201, PDGFR and SMA markers. Developmental studies revealed that the Col6a1Cre mouse also targets mesenchymal aggregates that are crucial for intestinal morphogenesis and patterning, suggesting an ontogenic relationship between them and homeostatic telocytes. Cell depletion experiments in adulthood showed that Col6a1+/CD201+ mesenchymal cells regulate homeostatic enteroendocrine cell differentiation and epithelial proliferation. During acute colitis, they expressed an inflammatory and extracellular matrix remodeling gene signature, but they also retained their properties and topology. Notably, both in homeostasis and tissue regeneration, they were dispensable for normal organ architecture, while CD34+ mesenchymal cells expanded, localised at the top of the crypts and showed increased expression of villous-associated morphogenetic factors, providing thus evidence for the plasticity potential of distinct mesenchymal populations in the intestine. Our results provide a comprehensive analysis of the identities, origin, and functional significance of distinct mesenchymal populations in the intestine.

cell biology↗

bioRxiv2020

Ectopic bone formation and systemic bone loss in a transmembrane TNF-driven model of human spondyloarthritis

Background The transmembrane-TNF transgenic mouse, TgA86, has been shown to develop spontaneously peripheral arthritis with signs of axial involvement. To assess similarity to human spondyloarthritis we performed detailed characterization of the axial, peripheral and comorbid pathologies of this model.Methods TgA86 bone pathologies were assessed at different ages using CT imaging of the spine, tail vertebrae and hind limbs and characterized in detail by histopathological and immunohistochemical analysis. Cardiac function was examined by echocardiography and electrocardiography and bone structural parameters by µCT analysis. The response of TgA86 mice to either early or late anti-TNF treatment was evaluated clinically, histopathologically and by µCT analysis.Results TgA86 mice developed with 100% penetrance spontaneous axial and peripheral pathology which progressed with time and manifested as reduced body weight and body length, kyphosis, tail bendings as well as swollen and distorted hind joints. Whole body CT analysis at advanced ages revealed bone erosions of sacral and caudal vertebrae as well as of sacroiliac joints and hind limps, and also, new ectopic bone formation and eventually vertebral fusion. The pathology of these mice highly resembled that of SpA patients, as it evolved through an early inflammatory phase, evident as enthesitis and synovitis in the affected joints, characterized by mesenchymal cell accumulation and neutrophilic infiltration. Subsequently, regression of inflammation was accompanied by ectopic bone formation, leading to ankylosis. In addition, both systemic bone loss and comorbid heart valve pathology were evident. Importantly, early anti-TNF treatment, similar to clinical treatment protocols, significantly reduced the inflammatory phase of both the axial and peripheral pathology of TgA86 mice.Conclusions The TgA86 mice develop a spontaneous peripheral and axial biphasic pathology accompanied by comorbid heart valvular dysfunction and osteoporosis, overall faithfully reproducing the progression of pathognomonic features of human spondyloarthritis. Therefore, the TgA86 mouse represents a valuable model for deciphering the pathogenic mechanisms of spondyloarthritis and for assessing the efficacy of human therapeutics targeting different phases of the disease.Competing Interest StatementProf. George Kollias participates in the BoD of Biomedcode; Dr. Florian Meier has received grants from Pfizer. All other authors declare no competing interests.List of abbreviationsASAnkylosing SpondylitisCTComputed TomographyCVDCardiovascular DiseaseEDTAEthylenediaminetetraacetic acidH&EHematoxylin&EosinIBDInflammatory Bowel DiseaseMRIMagnetic Resonance ImagingOPOsteoporosisOPNOsteopontinPsAPsoriatic arthritisRARheumatoid ArthritisReAReactive arthritiss/oSafranin/OSpASpondyloarthritisTgtransgenictmTNFtransmembrane mouseTNF TNF-αTumor Necrosis Factor αTRAPTartrate-resistant acid phosphataseUTRUntranslated RegionwtWild TypeµCTmicro CTView Full Text

pathology↗

bioRxiv2019

Genetic deletion of Autotaxin from CD11b+ cells decreases the severity of experimental autoimmune encephalomyelitis

Autotaxin (ATX) is a secreted lysophospholipase D catalyzing the extracellular production of lysophosphatidic acid (LPA), a growth factor-like signaling lysophospholipid. ATX and LPA signaling have been incriminated in the pathogenesis of different chronic inflammatory diseases and various types of cancer. In this report, deregulated ATX and LPA levels were detected in the spinal cord and plasma of mice during the development of experimental autoimmune encephalomyelitis (EAE). Among the different sources of ATX expression in the inflamed spinal cord, F4/80+CD11b+ cells, mostly activated macrophages and microglia, were found to express ATX, further suggesting an autocrine role for ATX/LPA in their activation, an EAE hallmark. Accordingly, ATX genetic deletion from CD11b+ cells attenuated the severity of EAE, thus proposing a pathogenic role for the ATX/LPA axis in neuroinflammatory disorders.

immunology↗