Cells In Lung Fibrosis Research Articles

Inhibition of PDIA3 in club cells attenuates osteopontin production and lung fibrosis

BackgroundThe role of club cells in the pathology of idiopathic pulmonary fibrosis (IPF) is not well understood. Protein disulfide isomerase A3 (PDIA3), an endoplasmic reticulum-based redox chaperone required for the...

Active mTOR in Lung Epithelium Promotes Epithelial-Mesenchymal Transition and Enhances Lung Fibrosis.

The mTOR pathway is one of the key signal cascades in the pathogenesis of idiopathic pulmonary fibrosis. Previous studies have mainly focused on this pathway in the fibroblasts and/or myofibroblasts, but not in the epithelial cells. In this study, we sought to investigate the role of the mTOR pathway in lung epithelial cells in lung fibrosis. Using Sftpc-mTORSL1+IT transgenic mice, in which active mTOR is conditionally expressed in lung epithelial cells, we assessed the effects of chronically activated mTOR in lung epithelial cells on lung phenotypes as well as bleomycin-induced lung fibrosis. Furthermore, we isolated alveolar epithelial cell type 2 from mice and performed RNA sequencing. Sftpc-mTORSL1+IT transgenic mice had no obvious abnormal findings, but, after bleomycin administration, showed more severe fibrotic changes and lower lung compliance than control mice. RNA sequencing revealed Angptl4 (angiopoietin-like protein 4) as a candidate downstream gene of the mTOR pathway. In vitro studies revealed that ANGPTL4, as well as mTOR, promoted tight junction vulnerability and epithelial-mesenchymal transition. mTOR activation in lung epithelial cells promoted lung fibrosis and the expression of ANGPTL4, a novel downstream target of the mTOR pathway, which could be related to the etiology of fibrosis.

The highs and lows of CD4+ tissue-resident T cells in lung fibrosis.

Chronic exposure to fungal antigen drives the development of two subsets of CD4+ TRM cells, distinguished by high or low expression of the integrin CD103, with opposing roles in inflammation-induced lung fibrosis.

Attenuation of pulmonary fibrosis in type I collagen-targeted reporter mice with ALK-5 inhibitors

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal disease, and consequently, effective antifibrotic drugs are strongly desired. Although we have previously reported a validated Col1a1-Luc Tg rat model for fibrosis, there are only a few mouse models that enable the evaluation of fibrosis in a short time period and with high sensitivity. Therefore, we generated a Col1a1-internal ribosome entry site (IRES)-Luc knock-in (KI) mouse in which the IRES-luciferase gene construct was inserted into the 3′-UTR of the type I collagen alpha 1 gene (Col1a1). There was a high correlation between luciferase activity and hydroxyproline content in the KI mice, which is similar to the result that we have previously reported for the Col1a1-Luc Tg rat model. In a bleomycin (BLM)-induced lung fibrosis model, luciferase activity in the lung showed a significant increase 3 days after BLM treatment, while only a slight increase was observed in the hydroxyproline content. An ALK-5 inhibitor—R-268712—was effective in inhibiting the luciferase activity in both the in vivo BLM-induced lung fibrosis model and in vitro primary mouse lung fibroblasts. This suggests that fibroblasts are the major collagen-producing cells in lung fibrosis. In human lung fibroblasts, TGF-β stimulation induced α-smooth muscle actin as observed by immunostaining, suggesting that myofibroblast transdifferentiation (MTD) plays an important role in lung fibrosis. Together, these results indicated that ALK-5 inhibitors might affect lung fibrosis mainly via the inhibition of MTD. Thus, the Col1a1-IRES-Luc KI mouse might be useful for the evaluation of antifibrotic effects and their underlying mechanisms.

Characterization of human PDGFR-β-positive pericytes from IPF and non-IPF lungs

Pericytes are key regulators of the microvasculature through their close interactions with the endothelium. However, pericytes play additional roles in tissue homeostasis and repair, in part by transitioning into myofibroblasts. Accumulation of myofibroblasts is a hallmark of fibrotic diseases such as idiopathic pulmonary fibrosis (IPF). To understand the contribution and role of pericytes in human lung fibrosis, we isolated these cells from non-IPF control and IPF lung tissues based on expression of platelet-derived growth factor receptor-β (PDGFR-β), a common marker of pericytes. When cultured in a specialized growth medium, PDGFR-β+ cells retain the morphology and marker profile typical of pericytes. We found that IPF pericytes migrated more rapidly and invaded a basement membrane matrix more readily than control pericytes. Exposure of cells to transforming growth factor-β, a major fibrosis-inducing cytokine, increased expression of α-smooth muscle actin and extracellular matrix genes in both control and IPF pericytes. Given that pericytes are uniquely positioned in vivo to respond to danger signals of both systemic and tissue origin, we stimulated human lung pericytes with agonists having pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs). Both control and IPF lung pericytes increased expression of proinflammatory chemokines in response to specific PAMPs and DAMPs released from necrotic cells. Our results suggest that control and IPF lung pericytes are poised to react to tissue damage, as well as microbial and fibrotic stimuli. However, IPF pericytes are primed for migration and matrix invasion, features that may contribute to the function of these cells in lung fibrosis.

Human alveolar epithelial cells type II are capable of TGF\u03b2-dependent epithelial-mesenchymal-transition and collagen-synthesis

BackgroundThe origin of collagen-producing cells in lung fibrosis is unclear. The involvement of embryonic signaling pathways has been acknowledged and trans-differentiation of epithelial cells is discussed critically. The work presented here investigates the role of TGFB in cytoskeleton remodeling and the expression of Epithelial-Mesenchymal-Transition markers by Alveolar Epithelial Cells Type II and tests the hypothesis if human alveolar epithelial cells are capable of trans-differentiation and production of pro-fibrotic collagen.MethodsPrimary human alveolar epithelial cells type II were extracted from donor tissues and stimulated with TGFβ and a TGFβ-inhibitor. Transcriptome and pathway analyses as well as validation of results on protein level were conducted.ResultsA TGFβ-responsive fingerprint was found and investigated for mutual interactions. Interaction modules exhibited enrichment of genes that favor actin cytoskeleton remodeling, differentiation processes and collagen metabolism. Cross-validation of the TGFβ-responsive fingerprint in an independent IPF dataset revealed overlap of genes and supported the direction of regulated genes and TGFβ-specificity.ConclusionsPrimary human alveolar epithelial cells type II seem undergo a TGFβ-dependent phenotypic change, exhibit differential expression of EMT markers in vitro and acquire the potential to produce collagen.

Activated human T lymphocytes inhibit TGFβ-induced fibroblast to myofibroblast differentiation via prostaglandins D2 and E2.

In pulmonary fibrosis (PF), fibroblasts and myofibroblasts proliferate and deposit excessive extracellular matrix in the interstitium, impairing normal lung function. Because most forms of PF have a poor prognosis and limited treatment options, PF represents an urgent unmet need for novel, effective therapeutics. Although the role of immune cells in lung fibrosis is unclear, recent studies suggest that T lymphocyte (T cell) activation may be impaired in PF patients. Furthermore, we have previously shown that activated T cells can produce prostaglandins with anti-scarring potential. Here, we test the hypothesis that activated T cells directly inhibit myofibroblast differentiation using a coculture system. Coculture with activated primary blood-derived T cells, from both healthy human donors and PF patients, inhibited transforming growth factor β-induced myofibroblast differentiation in primary human lung fibroblasts isolated from either normal or PF lung tissue. Coculture supernatants contained anti-fibrotic prostaglandins D2 and E2, and the inhibitory effect of coculture on myofibroblast differentiation was largely reversed when prostaglandin production was abrogated either by resting the T cells before coculture or via specific pharmacological inhibitors. Moreover, coculture conditions induced COX-2 in HLFs but not in T cells, suggesting that T cells deliver an activating signal to HLFs, which in turn produce anti-fibrotic prostaglandins. We show for the first time that coculture with activated primary human T lymphocytes strongly inhibits myofibroblast differentiation, revealing a novel cell-to-cell communication network with therapeutic implications for fibrotic lung diseases.

Modular deconvolution of tissue transcriptomes: pitfalls and solutions

BackgroundMaking hypothesis-led interrogations of whole-genome transcriptomic datasets is a challenge. Transcriptional modules define specific biological processes, but multiple modules have now been published with overlapping annotations. In this study we aimed to generate and validate the modular discrimination index (MDI) score, ranking the accuracy and resolution of any cell type specific module to assess cellular enrichment in tissues from transcriptional datasets. MethodsWe made use of publicly available transcriptomic datasets of purified immune cell types to compare the expression of modules annotated to reflect the expression of different immune cells. MDI scores were derived from the relative expression of each module in its annotated cell type, relative to all other cells. Independent datasets from human tissue and blood samples were then used to validate the MDI score in relation to the relative enrichment of different modules' gene expression. FindingsWe found that 26 T-cell modules varied both in their composition and in their gene expression in a tuberculin skin test, a prototypical T cell driven cell inflammatory process. To address this heterogeneity, we assessed the accuracy of cell-type modules, by calculating MDI scores for all published T cell, B cell, natural killer cell and neutrophil modules. MDI scores strongly predicted each module's ability to show histologically proven cellular enrichment in a variety of independent tissue samples: T cells in psoriatic skin, B cells in lung fibrosis, and neutrophils in erythema nodosum leprosum skin lesions. In addition, MDI scores were also validated in relation to changes in cell frequency in blood: modules with the greatest MDI score were most predictive of each module's association with cell numbers for both high frequency cells (neutrophils r2=0·545, p=0·01) and low frequency cells (B cells r2=0·865, p=0·01) in blood. Finally, we showed that modules with the highest MDI score elicited the T cell enrichment seen in the tuberculin skin test, whereas this was most often not detected by low MDI scoring modules. InterpretationThis study shows that MDI scoring provides a robust and reproducible assessment of a transcriptional module's accuracy and resolution, and should be determined before using modular deconvolution of tissue samples. The MDI scoring framework can be extended and applied across a range of disciplines for which annotated modules could be used to interrogate transcriptional datasets. FundingWellcome Trust.

The role of CCR2+ CD4 T cells in lung fibrosis

Introduction: T cells have been suggested to play important roles in the development of lung fibrosis. Chemokine receptor 2 (CCR2), the receptor of macrophage chemoattractant protein-1 (MCP-1), is expressed by many immune cell types including T cells. The broad inhibition of CCR2-dependent signaling was shown to attenuate the development of pulmonary fibrosis in animal models. However, the specific role of CCR2+CD4+ T cells in pulmonary fibrosis is unknown.

HGF Expressing Stem Cells in Usual Interstitial Pneumonia Originate from the Bone Marrow and Are Antifibrotic

BackgroundPulmonary fibrosis may result from abnormal alveolar wound repair after injury. Hepatocyte growth factor (HGF) improves alveolar epithelial wound repair in the lung. Stem cells were shown to play a major role in lung injury, repair and fibrosis. We studied the presence, origin and antifibrotic properties of HGF-expressing stem cells in usual interstitial pneumonia.MethodsImmunohistochemistry was performed in lung tissue sections and primary alveolar epithelial cells obtained from patients with usual interstitial pneumonia (UIP, n = 7). Bone marrow derived stromal cells (BMSC) from adult male rats were transfected with HGF, instilled intratracheally into bleomycin injured rat lungs and analyzed 7 and 14 days later.ResultsIn UIP, HGF was expressed in specific cells mainly located in fibrotic areas close to the hyperplastic alveolar epithelium. HGF-positive cells showed strong co-staining for the mesenchymal stem cell markers CD44, CD29, CD105 and CD90, indicating stem cell origin. HGF-positive cells also co-stained for CXCR4 (HGF+/CXCR4+) indicating that they originate from the bone marrow. The stem cell characteristics were confirmed in HGF secreting cells isolated from UIP lung biopsies. In vivo experiments showed that HGF-expressing BMSC attenuated bleomycin induced pulmonary fibrosis in the rat, indicating a beneficial role of bone marrow derived, HGF secreting stem cells in lung fibrosis.ConclusionsHGF-positive stem cells are present in human fibrotic lung tissue (UIP) and originate from the bone marrow. Since HGF-transfected BMSC reduce bleomycin induced lung fibrosis in the bleomycin lung injury and fibrosis model, we assume that HGF-expressing, bone-marrow derived stem cells in UIP have antifibrotic properties.