Biology subjects

Tatler, A. L.

Publications and source records attributed to Tatler, A. L..

5 recordsLinked to original sources

bioRxiv2024

Multiscale single-cell assessment of the fibrotic niche in idiopathic pulmonary fibrosis

BackgroundIdiopathic pulmonary fibrosis (IPF) is a progressive, fatal disease characterised by excessive extracellular matrix deposition within the lung. Recent advances in single-cell RNA sequencing have identified distinct fibrotic populations, yet their origins and spatial relationships remain incompletely understood. MethodsUsing spatial transcriptomics and Hyperion imaging mass cytometry we compared the cellular composition in formalin fixed paraffin embedded fibrotic lesions (n=9 patients) with control lung (n=9), and cellular interactions were inferred using CellChat V2 ligand-receptor analysis. Monolayers of airway epithelial cells were used to identify changes in keratin (KRT) expression following cell detachment and cyclical mechanical stretch. ResultsSpatial multiomics profiling of human lung cells confirmed the in situ localisation of previously described IPF-enriched populations, and identified a previously unrecognized KRT5low/KRT17 epithelial population derived from airway basal cells that progressively acquiring molecular features of aberrant basaloid cells, forming a unique fibrotic niche enriched with the Secreted Phosphoprotein 1 (SPP1) positive macrophages. Functional studies demonstrated that epithelial detachment and cyclical mechanical stretch drive KRT5 reduction, providing a mechanism for the emergence of this transitional state. In addition, we also identified distinct immune-stromal niches enriched in lymphocytes and alveolar fibroblasts. ConclusionThese findings delineate distinct fibrotic epithelial niches in IPF and support a model in which epithelial loss induces aberrant basaloid differentiation and fibroblast activation, with subsequent airway traction and epithelial detachment generating a secondary niche enriched in basal-derived KRT5low/KRT17 cells and SPP1 macrophages.

molecular biology↗

bioRxiv2022

Differential remodelling in small and large murine airways revealed by novel whole lung airway analysis.

Airway remodelling occurs in chronic asthma leading to increased airway smooth muscle (ASM) mass and extra-cellular matrix (ECM) deposition. Whilst extensively studied in murine airways; studies report only selected larger airways at one time point meaning the spatial distribution and resolution of remodelling are poorly understood. Here we use a new method allowing comprehensive assessment of the spatial and temporal changes in ASM, ECM and epithelium in large numbers of murine airways after allergen challenge. Using image processing to analyse 20-50 airways from a whole lung section revealed increases in ASM and ECM after allergen challenge were greater in small and large rather than intermediate airways. ASM predominantly accumulated adjacent to the basement membrane whereas ECM was distributed across the airway wall. Epithelial hyperplasia was most marked in small and intermediate airways. Post challenge, ASM changes resolved over seven days whereas ECM and epithelial changes persisted. The new method suggests large and small airways remodel differently and the long-term consequences of airway inflammation may depend more on ECM and epithelial changes than ASM. The method reduces the number of animals needed, reveals important spatial differences in remodelling and could set new analysis standards for murine asthma models.

physiology↗

bioRxiv2020

Lysyl oxidase-like 2 (LOXL2) is Increased in Asthma and Contributes to Asthmatic Airway Remodelling

Airway smooth muscle cells (ASM) are fundamental to asthma pathogenesis, influencing bronchoconstriction, airway hyper-responsiveness, and airway remodelling. Extracellular matrix (ECM) can influence tissue remodelling pathways, however, to date no study has investigated the effect of ASM ECM stiffness and crosslinking on the development of asthmatic airway remodelling. We hypothesised that TGF{beta} activation by ASM is influenced by ECM in asthma and sought to investigate the mechanisms involved. This study combines in vitro and in vivo approaches: human ASM cells were used in vitro to investigate basal TGF{beta} activation and expression of ECM crosslinking enzymes. Human bronchial biopsies from asthmatic and non-asthmatic donors were used to confirm LOXL2 expression ASM. A chronic ovalbumin model of asthma was used to study the effect of LOXL2 inhibition on airway remodelling. We found that ASM cells from asthmatics activated more TGF{beta} basally than non-asthmatic controls and that diseased cell-derived ECM influences levels of TGF{beta} activated. Our data demonstrate that the ECM crosslinking enzyme LOXL2 is increased in asthmatic ASM cells and in bronchial biopsies. Crucially, we show that LOXL2 inhibition reduces ECM stiffness and TGF{beta} activation in vitro, and can reduce subepithelial collagen deposition and ASM thickness, two features of airway remodelling, in an ovalbumin mouse model of asthma. These data are the first to highlight a role for LOXL2 in the development of asthmatic airway remodelling and suggest that LOXL2 inhibition warrants further investigation as a potential therapy to reduce remodelling of the airways in severe asthma.

cell biology↗

bioRxiv2020

Stretch Regulates Alveologenesis Via Mesenchymal Gαq/11-Mediated TGFβ2 Activation

Alveolar development and repair require tight spatiotemporal regulation of numerous signalling pathways that are influenced by chemical and mechanical stimuli. Mesenchymal cells play key roles in numerous developmental processes. Transforming growth factor-{beta} (TGF{beta}) is essential for alveologenesis and lung repair, and the G protein subunits Gq and G11 (Gq/11) transmit mechanical and chemical signals to activate TGF{beta} in epithelial cells. To understand the role of mesenchymal Gq/11 in lung development, we generated constitutive (Pdgfrb-Cre+/-;Gnaqfl/fl;Gna11-/-) and inducible (Pdgfrb-Cre/ERT2+/-;Gnaqfl/fl;Gna11-/-) mesenchymal Gq/11 deleted mice. Mice with constitutive Gq/11 gene deletion exhibited abnormal alveolar development, with suppressed myofibroblast differentiation, altered mesenchymal cell synthetic function, and reduced lung TGF{beta}2 deposition, as well as kidney abnormalities. Tamoxifen-induced mesenchymal Gq/11 gene deletion in adult mice resulted in emphysema associated with reduced TGF{beta}2 and elastin deposition. Cyclical mechanical stretch-induced TGF{beta} activation required Gq/11 signalling and serine protease activity, but was independent of integrins, suggesting an isoform-specific role for TGF{beta}2. These data highlight a previously undescribed mechanism of cyclical stretch-induced Gq/11-dependent TGF{beta}2 signalling in mesenchymal cells, which is imperative for normal alveologenesis and maintenance of lung homeostasis. Summary statementMesenchymal cell Gq/11 signalling regulates myofibroblast function and stretch-mediated TGF{beta}2 signalling, which are important for alveologenesis and organ homeostasis. These mechanisms are relevant to both developmental and adult lung disease.

developmental biology↗

bioRxiv2019

Loss of ELK1 has differential effects on age-dependent organ fibrosis and integrin expression

ETS domain-containing protein-1 (ELK1) is a transcriptional repressor important in regulating v{beta}6 integrin expression. v{beta}6 integrins activate the profibrotic cytokine Transforming Growth Factor {beta}1 (TGF{beta}1) and are increased in the alveolar epithelium in Idiopathic Pulmonary Fibrosis (IPF). IPF is a disease associated with ageing and therefore we hypothesised that aged animals lacking Elk1 globally would develop spontaneous fibrosis in organs where v{beta}6-mediated TGF{beta} activation has been implicated.\n\nHere we identify that Elk1-knockout (Elk1-/0) mice aged to one year developed spontaneous fibrosis in the absence of injury in both the lung and the liver but not in the heart or kidneys. The lungs of Elk1-/0 aged mice demonstrated increased collagen deposition, in particular collagen 31, located in small fibrotic foci and thickened alveolar walls. Despite the liver having relatively low global levels of ELK1 expression, Elk1-/0 animals developed hepatosteatosis and fibrosis. The loss of Elk1 also had differential effects on Itgb1, Itgb5 and Itgb6 genes expression in the four organs potentially explaining the phenotypic differences in these organs. To understand the potential causes of reduced ELK1 in human disease we exposed human cells and murine lung slices to cigarette smoke extract which lead to reduced ELK1 expression which may explain the loss of ELK1 in human disease.\n\nThese data support a fundamental role for ELK1 in protecting against the development of progressive fibrosis via transcriptional regulation of beta integrin subunit genes, and demonstrate that loss of ELK1 can be caused by cigarette smoke.

pathology↗