Molecular Changes Implicate Angiogenesis and Arterial Remodeling in Systemic Sclerosis-Associated and Idiopathic Pulmonary Hypertension.

Background: Pulmonary hypertension (PH) is a common complication of systemic sclerosis (SSc) and a leading cause of mortality among patients with this disease. PH can also occur as an idiopathic condition (idiopathic pulmonary arterial hypertension). Investigation of transcriptomic alterations in vascular populations is critical to elucidating cellular mechanisms underlying pathobiology of SSc-associated and idiopathic PH.

Fibronectin-EDA accumulates via reduced ubiquitination downstream of Toll-like receptor 9 activation in SSc-ILD fibroblasts.

Accumulation of excessive extracellular matrix (ECM) components from lung fibroblasts is a feature of systemic sclerosis-associated interstitial lung disease (SSc-ILD), and there is increasing evidence that innate immune signaling pathways contribute to these processes. Toll-like receptors (TLRs) are innate immune sensors activated by danger signals derived from pathogens or host molecular patterns. Several damage-associated molecular pattern (DAMP) molecules are elevated in SSc-ILD plasma, including ligands that activate TLR9, an innate immune sensor recently implicated in driving profibrotic responses in fibroblasts.

Epigenetic Regulation of Profibrotic Macrophages in Systemic Sclerosis-Associated Interstitial Lung Disease.

Objective: Systemic sclerosis-associated interstitial lung disease (SSc-ILD) is the leading cause of death in patients with SSc with unclear pathogenesis and limited treatment options. Evidence strongly supports an important role for profibrotic secreted phosphoprotein 1 (SPP1)-expressing macrophages in SSc-ILD. This study was undertaken to define the transcriptome and chromatin structural changes of SPP1 SSc-ILD macrophages in order to better understand their role in promoting fibrosis and to identify transcription factors associated with open chromatin driving their altered phenotype.

A Pilot Study of Dimethyl Fumarate in Pulmonary Arterial Hypertension Associated with Systemic Sclerosis.

Introduction: Given the poor treatment options for pulmonary arterial hypertension associated systemic sclerosis (SSc-PAH) patients, we sought to determine clinical safety and efficacy of Dimethylfumarate (DMF), an Nrf2 agonist, and the effects on biomarkers of oxidative stress on SSc-PAH in an exploratory interventional clinical trial.

Objectives: The primary objectives were to assess the safety and efficacy of treatment with DMF in patients with SSc-PAH.

Methods: This was an investigator-initiated, double-blind, randomized, placebo-controlled trial conducted at two sites in the United States.

Expansion of Fcγ Receptor IIIa-Positive Macrophages, Ficolin 1-Positive Monocyte-Derived Dendritic Cells, and Plasmacytoid Dendritic Cells Associated With Severe Skin Disease in Systemic Sclerosis.

Objective: In this study, we sought a comprehensive understanding of myeloid cell types driving fibrosis in diffuse cutaneous systemic sclerosis (dcSSc) skin.

Methods: We analyzed the transcriptomes of 2,465 myeloid cells from skin biopsy specimens from 12 dcSSc patients and 10 healthy control subjects using single-cell RNA sequencing. Monocyte-derived dendritic cells (mo-DCs) were assessed using immunohistochemical staining and immunofluorescence analyses targeting ficolin-1 (FCN-1).

Kelch-like protein 42 is a profibrotic ubiquitin E3 ligase involved in systemic sclerosis.

Systemic scleroderma (SSc) is an autoimmune disease that affects over 2.5 million people globally. SSc results in dysfunctional connective tissues with excessive profibrotic signaling, affecting skin, cardiovascular, and particularly lung tissue.

Transcriptome landscape of myeloid cells in human skin reveals diversity, rare populations and putative DC progenitors.

Background: The heterogeneous functions of dermal myeloid cells in antigen presentation, and scavenging pathogens and cell debris places them centrally in cutaneous inflammation. Single cell transcriptomics can provide new understanding of the heterogeneity and function of yet incompletely understood human dermal myeloid cell subsets.

Objective: Investigate the transcriptome landscape of myeloid cells in healthy human skin.

Single-cell analysis reveals fibroblast heterogeneity and myofibroblasts in systemic sclerosis-associated interstitial lung disease.

Objectives: Myofibroblasts are key effector cells in the extracellular matrix remodelling of systemic sclerosis-associated interstitial lung disease (SSc-ILD); however, the diversity of fibroblast populations present in the healthy and SSc-ILD lung is unknown and has prevented the specific study of the myofibroblast transcriptome. We sought to identify and define the transcriptomes of myofibroblasts and other mesenchymal cell populations in human healthy and SSc-ILD lungs to understand how alterations in fibroblast phenotypes lead to SSc-ILD fibrosis.

Methods: We performed droplet-based, single-cell RNA-sequencing with integrated canonical correlation analysis of 13 explanted lung tissue specimens (56 196 cells) from four healthy control and four patients with SSc-ILD, with findings confirmed by cellular indexing of transcriptomes and epitopes by sequencing in additional samples.

Proliferating SPP1/MERTK-expressing macrophages in idiopathic pulmonary fibrosis.

A comprehensive understanding of the changes in gene expression in cell types involved in idiopathic pulmonary fibrosis (IPF) will shed light on the mechanisms underlying the loss of alveolar epithelial cells and development of honeycomb cysts and fibroblastic foci. We sought to understand changes in IPF lung cell transcriptomes and gain insight into innate immune aspects of pathogenesis.We investigated IPF pathogenesis using single-cell RNA-sequencing of fresh lung explants, comparing human IPF fibrotic lower lobes reflecting late disease, upper lobes reflecting early disease and normal lungs.

Single Cell RNA Sequencing Identifies HSPG2 and APLNR as Markers of Endothelial Cell Injury in Systemic Sclerosis Skin.

The mechanisms that lead to endothelial cell (EC) injury and propagate the vasculopathy in Systemic Sclerosis (SSc) are not well understood. Using single cell RNA sequencing (scRNA-seq), our goal was to identify EC markers and signature pathways associated with vascular injury in SSc skin. We implemented single cell sorting and subsequent RNA sequencing of cells isolated from SSc and healthy control skin.

SFRP2/DPP4 and FMO1/LSP1 Define Major Fibroblast Populations in Human Skin.

Fibroblasts produce matrix, regulate inflammation, mediate reparative processes, and serve as pluripotent mesenchymal cells. Analyzing digested normal human skin by single-cell RNA sequencing, we explored different fibroblast populations. T-distributed stochastic neighbor embedding and clustering of single-cell RNA sequencing data from six biopsy samples showed two major fibroblast populations, defined by distinct genes, including SFRP2 and FMO1, expressed exclusively by these two major fibroblast populations.

IRF5 distinguishes severe asthma in humans and drives Th1 phenotype and airway hyperreactivity in mice.

Severe asthma (SA) is a significant problem both clinically and economically, given its poor response to corticosteroids (CS). We recently reported a complex type 1-dominated (IFN-γ-dominated) immune response in more than 50% of severe asthmatics despite high-dose CS treatment. Also, IFN-γ was found to be critical for increased airway hyperreactivity (AHR) in our model of SA.

The mito-DAMP cardiolipin blocks IL-10 production causing persistent inflammation during bacterial pneumonia.

Bacterial pneumonia is a significant healthcare burden worldwide. Failure to resolve inflammation after infection precipitates lung injury and an increase in morbidity and mortality. Gram-negative bacteria are common in pneumonia and increased levels of the mito-damage-associated molecular pattern (DAMP) cardiolipin can be detected in the lungs.

Mitochondrial H2O2 in Lung Antigen-Presenting Cells Blocks NF-κB Activation to Prevent Unwarranted Immune Activation.

Inhalation of environmental antigens such as allergens does not always induce inflammation in the respiratory tract. While antigen-presenting cells (APCs), including dendritic cells and macrophages, take up inhaled antigens, the cell-intrinsic molecular mechanisms that prevent an inflammatory response during this process, such as activation of the transcription factor NF-κB, are not well understood. Here, we show that the nuclear receptor PPARγ plays a critical role in blocking NF-κB activation in response to inhaled antigens to preserve immune tolerance.

High IFN-γ and low SLPI mark severe asthma in mice and humans.

Severe asthma (SA) is a challenge to control, as patients are not responsive to high doses of systemic corticosteroids (CS). In contrast, mild-moderate asthma (MMA) is responsive to low doses of inhaled CS, indicating that Th2 cells, which are dominant in MMA, do not solely orchestrate SA development. Here, we analyzed broncholalveolar lavage cells isolated from MMA and SA patients and determined that IFN-γ (Th1) immune responses are exacerbated in the airways of individuals with SA, with reduced Th2 and IL-17 responses.

Cutting Edge: MMP-9 inhibits IL-23p19 expression in dendritic cells by targeting membrane stem cell factor affecting lung IL-17 response.

We reported previously that c-kit ligation by membrane-bound stem cell factor (mSCF) boosts IL-6 production in dendritic cells (DCs) and a Th17-immune response. However, Th17 establishment also requires heterodimeric IL-23, but the mechanisms that regulate IL-23 gene expression in DCs are not fully understood. We show that IL-23p19 gene expression in lung DCs is dependent on mSCF, which is regulated by the metalloproteinase MMP-9.

Early infection with respiratory syncytial virus impairs regulatory T cell function and increases susceptibility to allergic asthma.

Immune tolerance is instituted early in life, during which time regulatory T (T(reg)) cells have an important role. Recurrent infections with respiratory syncytial virus (RSV) in early life increase the risk for asthma in adult life. Repeated infection of infant mice tolerized to ovalbumin (OVA) through their mother's milk with RSV induced allergic airway disease in response to OVA sensitization and challenge, including airway inflammation, hyper-reactivity and higher OVA-specific IgE, as compared to uninfected tolerized control mice.

Stimulus-specific adaptation in specialized neurons in the inferior colliculus of the big brown bat, Eptesicus fuscus.

The inferior colliculus (IC) of the big brown bat (Eptesicus fuscus) contains specialized neurons that respond exclusively to highly specific spectrotemporal patterns such as sinusoidally frequency modulated (SFM) signals or directional frequency modulated sweeps (FM). Other specialized cells with I-shaped frequency response areas (FRAs) are tuned to very narrow frequency bands (1-2 kHz) in an amplitude-tolerant manner. In contrast, non-specialized neurons respond to any stimulus with energy in their frequency response area.