Long noncoding RNA H19X is a key mediator of TGF-beta-driven fibrosis

TGFβ is a master regulator of fibrosis, driving the differentiation of fibroblasts into apoptosis resistant myofibroblasts and sustaining the production of extracellular matrix (ECM) components. Here, we identify the nuclear lncRNA H19X as a master regulator of TGFβ-driven tissue fibrosis. H19X was consistently upregulated in a wide variety of human fibrotic tissues and diseases and was strongly induced by TGFβ, particularly in fibroblasts and fibroblast-related cells. Functional experiments following H19X silencing revealed that H19X is an obligatory factor for the TGFβ-induced ECM synthesis as well as differentiation and survival of ECM-producing myofibroblasts. We showed that H19X regulates DDIT4L gene expression, specifically interacting with a region upstream of DDIT4L gene and changing the chromatin accessibility of a DDIT4L enhancer. These events resulted in transcriptional repression of DDIT4L and, in turn, in increased collagen expression and fibrosis. Our results shed light on key effectors of the TGFβ-induced ECM remodeling and fibrosis

The AP1 transcription factor Fosl2 promotes systemic autoimmunity and inflammation by repressing treg development

Regulatory T cells (Tregs) represent a major population in the control of immune homeostasis and autoimmunity. Here we show that Fos-like 2 (Fosl2), a TCR-induced AP1 transcription factor, represses Treg development and controls autoimmunity. Mice overexpressing Fosl2 (Fosl2$^{tg}$) indeed show a systemic inflammatory phenotype, with immune infiltrates in multiple organs. This phenotype is absent in Fosl2$^{tg}$ × Rag2$^{-/-}$ mice lacking T and B cells, and Fosl2 induces T cell-intrinsic reduction of Treg development that is responsible for the inflammatory phenotype. Fosl2$^{tg}$ T cells can transfer inflammation, which is suppressed by the co-delivery of Tregs, while Fosl2 deficiency in T cells reduces the severity of autoimmunity in the EAE model. We find that Fosl2 could affect expression of FoxP3 and other Treg development genes. Our data highlight the importance of AP1 transcription factors, in particular Fosl2, during T cell development to determine Treg differentiation and control autoimmunity

Sustained mechanical tension governs fibrogenic activation of tendon stromal cells in systemic sclerosis

Fibrosis is a pathological outcome of aberrant repair responses in systemic sclerosis and affects many tissues, including tendons. Progressive matrix stiffening is a key feature of this pathological remodeling. How dysregulated tissue mechanics contribute to the persistence of the fibrotic phenotype has been obscured by limited availability of experimental tissue models that are both controllable and capture essential aspects of the tendon biophysical niche. Here, we developed a modular, cantilever-based platform that allows culture of 3D tendon-like constructs under easily variable static tension, emulating this central tendon-specific structure function relationship. The system reveals that elevated matrix tension instigates fibroblast-to-myofibroblast activation eliciting scar-like phenotypes in vitro. By using this mechano-culture system and preclinical and clinical models of systemic sclerosis, we further show that 3D matrix stiffness is inversely correlated with the transcription of major pro-fibrotic collagens, but positively correlate with the expression of markers of stromal-immune interactions. Co-culture of tendon stromal fibroblasts and bone marrow-derived macrophages override stiffness-mediated downregulation of matrix transcription, suggesting that normal tension mediated checkpoints are superseded by the local tissue immune state. Our study highlights the power of 3D reductionist approaches in dissecting the contribution of the elevated matrix tension to the positive feedforward loops between activated fibroblasts and progressive ECM stiffening in systemic sclerosis

Targeting the tumour microenvironment with an enzyme-responsive drug delivery system for the efficient therapy of breast and pancreatic cancers

International audienc

High-resolution profiling of MHC II peptide presentation capacity reveals SARS-CoV-2 CD4 T cell targets and mechanisms of immune escape

Understanding peptide presentation by specific MHC alleles is fundamental for controlling physiological functions of T cells and harnessing them for therapeutic use. However, commonly used in silico predictions and mass spectroscopy have their limitations in precision, sensitivity, and throughput, particularly for MHC class II. Here, we present MEDi, a novel mammalian epitope display that allows an unbiased, affordable, high-resolution mapping of MHC peptide presentation capacity. Our platform provides a detailed picture by testing every antigen-derived peptide and is scalable to all the MHC II alleles. Given the urgent need to understand immune evasion for formulating effective responses to threats such as SARS-CoV-2, we provide a comprehensive analysis of the presentability of all SARS-CoV-2 peptides in the context of several HLA class II alleles. We show that several mutations arising in viral strains expanding globally resulted in reduced peptide presentability by multiple HLA class II alleles, while some increased it, suggesting alteration of MHC II presentation landscapes as a possible immune escape mechanism.ISSN:2375-254

The AP-1 transcription factor Fosl-2 drives cardiac fibrosis and arrhythmias under immunofibrotic conditions

Fibrotic changes in the myocardium and cardiac arrhythmias represent fatal complications in systemic sclerosis (SSc), however the underlying mechanisms remain elusive. Mice overexpressing transcription factor Fosl-2 (Fosl-2tg) represent animal model of SSc. Fosl-2tg mice showed interstitial cardiac fibrosis, disorganized connexin-43/40 in intercalated discs and deregulated expression of genes controlling conduction system, and developed higher heart rate (HR), prolonged QT intervals, arrhythmias with prevalence of premature ventricular contractions, ventricular tachycardias, II-degree atrio-ventricular blocks and reduced HR variability. Following stimulation with isoproterenol Fosl-2tg mice showed impaired HR response. In contrast to Fosl-2tg, immunodeficient Rag2-/-Fosl-2tg mice were protected from enhanced myocardial fibrosis and ECG abnormalities. Transcriptomics analysis demonstrated that Fosl-2-overexpression was responsible for profibrotic signature of cardiac fibroblasts, whereas inflammatory component in Fosl-2tg mice activated their fibrotic and arrhythmogenic phenotype. In human cardiac fibroblasts FOSL-2-overexpression enhanced myofibroblast signature under proinflammatory or profibrotic stimuli. These results demonstrate that under immunofibrotic conditions transcription factor Fosl-2 exaggerates myocardial fibrosis, arrhythmias and aberrant response to stress.ISSN:2399-364

The AP-1 transcription factor Fosl-2 drives cardiac fibrosis and arrhythmias under immunofibrotic conditions

Fibrotic changes in the myocardium and cardiac arrhythmias represent fatal complications in systemic sclerosis (SSc), however the underlying mechanisms remain elusive. Mice overexpressing transcription factor Fosl-2 (Fosl-2$^{tg}$) represent animal model of SSc. Fosl-2$^{tg}$ mice showed interstitial cardiac fibrosis, disorganized connexin-43/40 in intercalated discs and deregulated expression of genes controlling conduction system, and developed higher heart rate (HR), prolonged QT intervals, arrhythmias with prevalence of premature ventricular contractions, ventricular tachycardias, II-degree atrio-ventricular blocks and reduced HR variability. Following stimulation with isoproterenol Fosl-2$^{tg}$ mice showed impaired HR response. In contrast to Fosl-2$^{tg}$, immunodeficient Rag2$^{-/-}$Fosl-2$^{tg}$ mice were protected from enhanced myocardial fibrosis and ECG abnormalities. Transcriptomics analysis demonstrated that Fosl-2-overexpression was responsible for profibrotic signature of cardiac fibroblasts, whereas inflammatory component in Fosl-2$^{tg}$ mice activated their fibrotic and arrhythmogenic phenotype. In human cardiac fibroblasts FOSL-2-overexpression enhanced myofibroblast signature under proinflammatory or profibrotic stimuli. These results demonstrate that under immunofibrotic conditions transcription factor Fosl-2 exaggerates myocardial fibrosis, arrhythmias and aberrant response to stress