Epithelial repair mechanisms in the lung

Radiation-Induced Lung Fibrosis: Preclinical Animal Models and Therapeutic Strategies

Radiation-induced lung injury (RILI), including acute radiation pneumonitis and chronic radiation-induced lung fibrosis, is the most common side effect of radiation therapy. RILI is a complicated process that causes the accumulation, proliferation, and differentiation of fibroblasts and, finally, results in excessive extracellular matrix deposition. Currently, there are no approved treatment options for patients with radiation-induced pulmonary fibrosis (RIPF) partly due to the absence of effective targets. Current research advances include the development of small animal models reflecting modern radiotherapy, an understanding of the molecular basis of RIPF, and the identification of candidate drugs for prevention and treatment. Insights provided by this research have resulted in increased interest in disease progression and prognosis, the development of novel anti-fibrotic agents, and a more targeted approach to the treatment of RIPF.

The role of the non-ciliated bronchiolar cell in tolerance to inhaled vanadium of the bronchiolar epithelium

The Non-Ciliated Bronchiolar Cell (NCBC) is responsible for the defense and maintenance of the bronchiolar epithelium. Several cellular defense mechanisms have been associated with an increase in the secretion of CC16 and changes in the phenotype of the cell; these mechanisms could be linked to tolerance to the damage due to exposure to inhaled Particulate Matter (PM) of the epithelium. These defense mechanisms have not been sufficiently explored. In this article, we studied the response of the NCBC to inhaled vanadium, an element which adheres to PM. This response was measured by the changes in the phenotype of the NCBC and the secretion of CC16 in a mouse model. Mice were exposed in two phases to different vanadium concentrations; 1.27 mg/m³ in the first phase and 2.56 mg/m³ in the second phase. Mice were sacrificed on the 2nd, 4th, 5th, 6th and 8th weeks. In the second phase, we observed the following: sloughing of the NCBC, hyperplasia and small inflammatory foci remained without changes and that the expression of CC16 was higher in this phase than in phase I. We also observed a change in the phenotype with a slow decrease in both phases. The increase in the secretion of CC16 and the phenotype reversion could be due to the anti-inflammatory activity of CC16. The changes observed in the second phase could be attributed to the tolerance to inhaled vanadium.

What Role Does CFTR Play in Development, Differentiation, Regeneration and Cancer?

One of the key features associated with the substantial increase in life expectancy for individuals with CF is an elevated predisposition to cancer, firmly established by recent studies involving large cohorts. With the recent advances in cystic fibrosis transmembrane conductance regulator (CFTR) modulator therapies and the increased long-term survival rate of individuals with cystic fibrosis (CF), this is a novel challenge emerging at the forefront of this disease. However, the mechanisms linking dysfunctional CFTR to carcinogenesis have yet to be unravelled. Clues to this challenging open question emerge from key findings in an increasing number of studies showing that CFTR plays a role in fundamental cellular processes such as foetal development, epithelial differentiation/polarization, and regeneration, as well as in epithelial–mesenchymal transition (EMT). Here, we provide state-of-the-art descriptions on the moonlight roles of CFTR in these processes, highlighting how they can contribute to novel therapeutic strategies. However, such roles are still largely unknown, so we need rapid progress in the elucidation of the underlying mechanisms to find the answers and thus tailor the most appropriate therapeutic approaches.

Discovery of potential asthma targets based on the clinical efficacy of Traditional Chinese Medicine formulas

ETHNOPHARMACOLOGICAL RELEVANCE

Standard therapy for asthma, a highly heterogeneous disease, is primarily based on bronchodilators and immunosuppressive drugs, which confer short-term symptomatic relief but not a cure. It is difficult to discover novel bronchodilators, although potential new targets are emerging. Traditional Chinese Medicine (TCM) formulas have been used to treat asthma for more than 2000 years, forming the basis for representative asthma treatments.

AIM OF THE STUDY

Based on the efficacy of TCM formulas, anti-asthmatic herbal compounds bind proteins are potential targets for asthma therapy. This analysis will provide new drug targets and discovery strategies for asthma therapy.

MATERIALS AND METHODS

A list of candidate herbs for asthma was selected from the classical formulas (CFs) of TCM for the treatment of wheezing or dyspnea recorded in Treatise on Cold Damage and Miscellaneous Diseases (TCDMD) and from modern herbal formulas identified in the SAPHRON TCM Database using the keywords "wheezing" or "dyspnea". Compounds in the selected herbs and compounds that directly bind target proteins were acquired by searching the Herbal Ingredients' Targets Database (HITD), TCM Data Bank (TCMDB) and TCM Integrated Database (TCMID). Therapeutic targets of conventional medicine (CM) for asthma were collected by searching Therapeutic Target Database (TTD), DrugBank and PubMed as supplements. Finally, the enriched gene ontology (GO) terms of the targets were obtained using the Database for Annotation Visualization and Integrated Discovery (DAVID) and protein-protein interactions (PPI) networks were constructed using Search Tool for the Retrieval of Interacting Genes/Proteins (STRING). The effects of two selected TCM compounds, kaempferol and ginkgolide A, on cellular resistance in human airway smooth muscle cells (ASMCs) and pulmonary resistance in a mouse model were investigated.

RESULTS

The list of 32 candidate herbs for asthma was selected from 10 CFs for the treatment of wheezing or dyspnea recorded in TCDMD and 1037 modern herbal formulas obtained from the SAPHRON TCM Database. A total of 130 compounds from the 32 selected herbs and 68 herbal compounds directly bind target proteins were acquired from HITD and TCMDB. Eighty-eight therapeutic targets of CM for asthma were collected by searching TTD and PubMed as supplements. DAVID and STRING analyses showed targets of TCM formulas are primarily related to cytochrome P450 (CYP) family, transient receptor potential (TRP) channels, matrix metalloproteinases (MMPs) and ribosomal protein. Both TCM formulas and CM act on the same types of targets or signaling pathways, such as G protein-coupled receptors (GPCRs), steroid hormone receptors (SHRs), and JAK-STAT signaling pathway. The proteins directly targeted by herbal compounds, TRPM8, TRPA1, TRPV3, CYP1B1, CYP2B6, CYP1A2, CYP3A4, CYP1A1, PPARA, PPARD, NR1I2, MMP1, MMP2, ESR1, ESR2, RPLP0, RPLP1 and RPLP2, are potential targets for asthma therapy. In vitro results showed kaempferol (1 × 10^-2 mM) and ginkgolide A (1 × 10^-5 mM) significantly increased the cell index (P < 0.05 vs. histamine, n = 3) and therefore relaxed human ASMCs. In vivo results showed kaempferol (145 μg/kg) and ginkgolide A (205 μg/kg) significantly reduced pulmonary resistance (P < 0.05 vs. methacholine, n = 6).

CONCLUSION

Potential target discovery for asthma treatment based on the clinical effectiveness of TCM is a feasible strategy.

A mathematical model describing the localization and spread of influenza A virus infection within the human respiratory tract

Within the human respiratory tract (HRT), virus diffuses through the periciliary fluid (PCF) bathing the epithelium. But virus also undergoes advection: as the mucus layer sitting atop the PCF is pushed along by the ciliated cell's beating cilia, the PCF and its virus content are also pushed along, upwards towards the nose and mouth. While many mathematical models (MMs) have described the course of influenza A virus (IAV) infections in vivo, none have considered the impact of both diffusion and advection on the kinetics and localization of the infection. The MM herein represents the HRT as a one-dimensional track extending from the nose down towards the lower HRT, wherein stationary cells interact with IAV which moves within (diffusion) and along with (advection) the PCF. Diffusion was found to be negligible in the presence of advection which effectively sweeps away IAV, preventing infection from disseminating below the depth at which virus first deposits. Higher virus production rates (10-fold) are required at higher advection speeds (40 μm/s) to maintain equivalent infection severity and timing. Because virus is entrained upwards, upper parts of the HRT see more virus than lower parts. As such, infection peaks and resolves faster in the upper than in the lower HRT, making it appear as though infection progresses from the upper towards the lower HRT, as reported in mice. When the spatial MM is expanded to include cellular regeneration and an immune response, it reproduces tissue damage levels reported in patients. It also captures the kinetics of seasonal and avian IAV infections, via parameter changes consistent with reported differences between these strains, enabling comparison of their treatment with antivirals. This new MM offers a convenient and unique platform from which to study the localization and spread of respiratory viral infections within the HRT.

The Fabrication and in vitro Evaluation of Retinoic Acid-Loaded Electrospun Composite Biomaterials for Tracheal Tissue Regeneration

Although relatively rare, major trauma to the tracheal region of the airways poses a significant clinical challenge with few effective treatments. Bioengineering and regenerative medicine strategies have the potential to create biocompatible, implantable biomaterial scaffolds, with the capacity to restore lost tissue with functional neo-trachea. The main goal of this study was to develop a nanofibrous polycaprolactone-chitosan (PCL-Chitosan) scaffold loaded with a signaling molecule, all-trans retinoic acid (atRA), as a novel biomaterial approach for tracheal tissue engineering. Using the Spraybase® electrospinning platform, polymer concentration, solvent selection, and instrument parameters were optimized to yield a co-polymer with nanofibers of 181-197 nm in diameter that mimicked tracheobronchial tissue architecture. Thereafter, scaffolds were assessed for their biocompatibility and capacity to induce mucociliary functionalization using the Calu-3 cell line. PCL-Chitosan scaffolds were found to be biocompatible in nature and support Calu-3 cell viability over a 14 day time period. Additionally, the inclusion of atRA did not compromise Calu-3 cell viability, while still achieving an efficient encapsulation of the signaling molecule over a range of atRA concentrations. atRA release from scaffolds led to an increase in mucociliary gene expression at high scaffold loading doses, with augmented MUC5AC and FOXJ1 detected by RT-PCR. Overall, this scaffold integrates a synthetic polymer that has been used in human tracheal stents, a natural polymer generally regarded as safe (GRAS), and a drug with decades of use in patients. Coupled with the scalable nature of electrospinning as a fabrication method, all of these characteristics make the biomaterial outlined in this study amenable as an implantable device for an unmet clinical need in tracheal replacement.

The role of mesenchymal-epithelial transition in endometrial function

BACKGROUND

The human uterine endometrium undergoes significant remodeling and regeneration on a rapid and repeated basis, after parturition, menstruation, and in some cases, injury. The ability of the adult endometrium to undergo cyclic regeneration and differentiation/decidualization is essential for successful human reproduction. Multiple key physiologic functions of the endometrium require the cells of this tissue to transition between mesenchymal and epithelial phenotypes, processes known as mesenchymal-epithelial transition (MET) and epithelial-mesenchymal transition (EMT). Although MET/EMT processes have been widely characterized in embryonic development and in the context of malignancy, mounting evidence demonstrates the importance of MET/EMT in allowing the endometrium the phenotypic and functional flexibility necessary for successful decidualization, regeneration/re-epithelialization and embryo implantation.

OBJECTIVE AND RATIONALE

The objective of this review is to provide a comprehensive summary of the observations concerning MET and EMT and their regulation in physiologic uterine functions, specifically in the context of endometrial regeneration, decidualization and embryo implantation.

SEARCH METHODS

Using variations of the search terms 'mesenchymal-epithelial transition', 'mesenchymal-epithelial transformation', 'epithelial-mesenchymal transition', 'epithelial-mesenchymal transformation', 'uterus', 'endometrial regeneration', 'endometrial decidualization', 'embryo implantation', a search of the published literature between 1970 and 2018 was conducted using the PubMed database. In addition, we searched the reference lists of all publications included in this review for additional relevant original studies.

OUTCOMES

Multiple studies demonstrate that endometrial stromal cells contribute to the regeneration of both the stromal and epithelial cell compartments of the uterus, implicating a role for MET in mechanisms responsible for endometrial regeneration and re-epithelialization. During decidualization, endometrial stromal cells undergo morphologic and functional changes consistent with MET in order to accommodate embryo implantation. Under the influence of estradiol, progesterone and multiple other factors, endometrial stromal fibroblasts acquire epithelioid characteristics, such as expanded cytoplasm and rough endoplasmic reticulum required for greater secretory capacity, rounded nuclei, increased expression of junctional proteins which allow for increased cell-cell communication, and a reorganized actin cytoskeleton. During embryo implantation, in response to both maternal and embryonic-derived signals, the maternal luminal epithelium as well as the decidualized stromal cells acquire the mesenchymal characteristics of increased migration/motility, thus undergoing EMT in order to accommodate the invading trophoblast.

WIDER IMPLICATIONS

Overall, the findings support important roles for MET/EMT in multiple endometrial functions required for successful reproduction. The endometrium may be considered a unique wound healing model, given its ability to repeatedly undergo repair without scarring or loss of function. Future studies to elucidate how MET/EMT mechanisms may contribute to scar-free endometrial repair will have considerable potential to advance studies of wound healing mechanisms in other tissues.

Up-regulation of microRNA-574 attenuates lipopolysaccharide- or cecal ligation and puncture-induced sepsis associated with acute lung injury

Acute lung injury (ALI) is the most vulnerable organ in sepsis, however, its underlying mechanism remains unclear. Cell viability and apoptosis were detected by cell counting kit-8 and flow cytometry. The expressions of miR-574, Complement 3 (C3), glucose regulatory protein 78 (GRP78), C/EBP homologous protein (CHOP) and Caspase-12 were determined using quantitative real time (qRT)-PCR and Western blot. Histopathology of mice was stained by haematoxylin and eosin staining. The levels of tumour necrosis factor-α (TNF-α) and interleukin (IL)-1β were determined using ELISA. The expression of miR-574 was positively correlated with cell viability in lipopolysaccharide (LPS)-treated cells. Cell viability was improved and apoptosis was inhibited by mimics. Meanwhile, the levels of GRP78, CHOP and Caspase-12 were suppressed by mimics and agomir in LPS-treated human bronchial epithelial (HBE) cells and cecal ligation and puncture (CLP)-treated mice. In vivo, lung tissue damages were ameliorated by agomir, which also decreased the levels of neutrophils, macrophages and albumin. C3 was a target gene of miR-574 and could be decreased by mimics. SiC3 enhanced cell viability and inhibited apoptosis, however, it suppressed the mRNA levels of GRP78, CHOP and Caspase-12. Up-regulation of miR-574 attenuated sepsis-induced lung injury may be by promoting C3 down-regulation and reducing sepsis-induced endoplasmic reticulum stress (ERS). SIGNIFICANCE OF THE STUDY: Clinically, the mortality rate of ALI induced by sepsis remains at a high level, thus, clarifying the mechanism of induction of ALI through pathogen infection will provide a new target for clinical treatment of ALI. In this study, up-regulation of miR-574 attenuated sepsis-induced lung injury may be by promoting C3 down-regulation and reducing sepsis-induced ERS. Our study provides a deeper understanding of sepsis.

The Long Noncoding RNA DNM3OS Is a Reservoir of FibromiRs with Major Functions in Lung Fibroblast Response to TGF-β and Pulmonary Fibrosis

Rationale: Given the paucity of effective treatments for idiopathic pulmonary fibrosis (IPF), new insights into the deleterious mechanisms controlling lung fibroblast activation, the key cell type driving the fibrogenic process, are essential to develop new therapeutic strategies. TGF-β (transforming growth factor-β) is the main profibrotic factor, but its inhibition is associated with severe side effects because of its pleiotropic role. Objectives: To determine if downstream noncoding effectors of TGF-β in fibroblasts may represent new effective therapeutic targets whose modulation may be well tolerated. Methods: We investigated the whole noncoding fraction of TGF-β-stimulated lung fibroblast transcriptome to identify new genomic determinants of lung fibroblast differentiation into myofibroblasts. Differential expression of the long noncoding RNA (lncRNA) DNM3OS (dynamin 3 opposite strand) and its associated microRNAs (miRNAs) was validated in a murine model of pulmonary fibrosis and in IPF tissue samples. Distinct and complementary antisense oligonucleotide-based strategies aiming at interfering with DNM3OS were used to elucidate the role of DNM3OS and its associated miRNAs in IPF pathogenesis. Measurements and Main Results: We identified DNM3OS as a fibroblast-specific critical downstream effector of TGF-β-induced lung myofibroblast activation. Mechanistically, DNM3OS regulates this process in trans by giving rise to three distinct profibrotic mature miRNAs (i.e., miR-199a-5p/3p and miR-214-3p), which influence SMAD and non-SMAD components of TGF-β signaling in a multifaceted way. In vivo, we showed that interfering with DNM3OS function not only prevents lung fibrosis but also improves established pulmonary fibrosis. Conclusions: Pharmacological approaches aiming at interfering with the lncRNA DNM3OS may represent new effective therapeutic strategies in IPF.

Effects of cannabis oil extract on immune response gene expression in human small airway epithelial cells (HSAEpC): implications for chronic obstructive pulmonary disease (COPD)

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is commonly associated with both a pro-inflammatory and a T-helper 1 (Th1) immune response. It was hypothesized that cannabis oil extract can alleviate COPD symptoms by eliciting an anti-inflammatory Th2 immune response. Accordingly, the effects of cannabis oil extract on the expression of 84 Th2 and related immune response genes in human small airways epithelial cells (HSAEpC) were investigated.

METHODS

HSAEpC from a single donor were treated with three dilutions of a standardized cannabis oil extract (1:400, 1:800 and 1:1600) along with a solvent control (0.25% [2.5 ul/ml] ethanol) for 24 h. There were four replicates per treatment dilution, and six for the control. RNA isolated from cells were employed in pathway-focused quantitative polymerase chain reaction (qPCR) microarray assays.

RESULTS

The extract induced significant (P < 0.05) changes in expression of 37 tested genes. Six genes (CSF2, IL1RL1, IL4, IL13RA2, IL17A and PPARG) were up-regulated at all three dilutions. Another two (CCL22 and TSLP) were up-regulated while six (CLCA1, CMA1, EPX, LTB4R, MAF and PMCH) were down-regulated at the 1:400 and 1:800 dilutions. The relationship of differentially-expressed genes of interest to biologic pathways was explored using the Database for Annotation, Visualization and Integrated Discovery (DAVID).

CONCLUSIONS

This exploratory investigation indicates that cannabis oil extract may affect expression of specific airway epithelial cell genes that could modulate pro-inflammatory or Th1 processes in COPD. These results provide a basis for further investigations and have prompted in vivo studies of the effects of cannabis oil extract on pulmonary function.

TRIAL REGISTRATION

NONE (all in vitro experiments).

Curcumin Modulates Paraquat-Induced Epithelial to Mesenchymal Transition by Regulating Transforming Growth Factor-β (TGF-β) in A549 Cells

Paraquat (PQ), a widely used potent herbicide, generates superoxide anions and other free radicals, leading to severe toxicity and acute lung injury. PQ induces pulmonary fibrosis through epithelial to mesenchymal transition (EMT) characterized by increased number of myofibroblasts. Time-dependent PQ-induced EMT has been evaluated in present investigation where intracellular ROS levels were significantly enhanced after 24 h of PQ intoxication. Anti-inflammatory effects of curcumin have been studied where alveolar epithelial cells (A549 cells) were incubated with curcumin (30 μΜ) for 1 and 3 h before PQ intoxication (700 μM). Western blot and immunocytochemistry studies revealed that pretreatment of A549 cells with curcumin for 3 h before PQ exposure has maintained E-cadherin expression and inhibited PQ induced α-smooth-muscle actin (α-SMA) expression. Transforming growth factor-β (TGF-β) that seems to be involved in PQ-induced EMT was enhanced after PQ intoxication, but curcumin pretreatment has effectively inhibited its expression. Immunostaining studies have shown that curcumin pretreatment has significantly reduced matrix metalloproteinase-9 (MMP-9) expressions, which were elevated after PQ intoxication. These results demonstrate that curcumin can regulate PQ-induced EMT by regulating the expression of TGF-β.

Exposure to Dimethyl Selenide (DMSe)-Derived Secondary Organic Aerosol Alters Transcriptomic Profiles in Human Airway Epithelial Cells

Dimethyl selenide (DMSe) is one of the major volatile organoselenium compounds released from aquatic and terrestrial environments through microbial transformation and plant metabolism. The detailed processes of DMSe leading to secondary organic aerosol (SOA) formation and the pulmonary health effects induced by inhalation of DMSe-derived SOA remain largely unknown. In this study, we characterized the chemical composition and formation yields of SOA produced from the oxidation of DMSe with OH radicals and O₃ in controlled chamber experiments. Further, we profiled the transcriptome-wide gene expression changes in human airway epithelial cells (BEAS-2B) after exposure to DMSe-derived SOA. Our analyses indicated a significantly higher SOA yield resulting from the OH-initiated oxidation of DMSe. The oxidative potential of DMSe-derived SOA, as measured by the dithiothreitol (DTT) assay, suggested the presence of oxidizing moieties in DMSe-derived SOA at levels higher than typical ambient aerosols. Utilizing RNA sequencing (RNA-Seq) techniques, gene expression profiling followed by pathway enrichment analysis revealed several major biological pathways perturbed by DMSe-derived SOA, including elevated genotoxicity, DNA damage, and p53-mediated stress responses, as well as downregulated cholesterol biosynthesis, glycolysis, and interleukin IL-4/IL-13 signaling. This study highlights the significance of DMSe-derived SOA as a stressor in human airway epithelial cells.

Serum activity of MMP-2 and MMP-9 and stromielisin-1 concentration as predictors in the pathogenesis of bronchopulmonary dysplasia in preterm neonates

Aim: Bronchopulmonary dysplasia (BPD) is one of the most severe respiratory diseases, mainly related to premature neonates. Previous studies indicated the role of matrix metalloproteinases (MMPs) in the development of BPD. The aim of the study was to determine the relationship between MMP-2, MMP-3, MMP-9 with their tissue inhibitors (TIMP-1 TIMP-2) and BPD occurrence in premature neonates. Material/Methods: Eighty-one patients, divided into four study groups, numbered from 1 to 4, depending on gestational age (25–28; 29–32; 33–36; 37–40 weeks), were enrolled. Venous blood was collected between 5 and 7 days after birth. The activity of MMP-2 and MMP-9 were determined with usage of gelatin zymography, whereas MMP-3, TIMP-1 and TIMP-2 was determined using the immunoassay ELISA. Results: BPD was diagnosed in 50% of patients from group 1 and 11% from group 2. The increase of MMP-2 activity in Group 2, and a decrease in MMP-2/TIMP-2 ratio was noticed in Group 1 compared to Group 2 and 4. A significantly lower incidence of BPD in patients with higher (above the median) values for MMP-2/TIMP-2 (OR = 0.02, CI = 0.00 – 0.55; p <0.05) was noticed in Group 1. The decreased occurrence of BPD in patients with higher MMP-3 concentration, higher MMP-9 activity and the higher value of MMP-9/TIMP-1 did not reach statistical significance. Conclusions: It has been shown that elevated activity of collagenolytic enzyme in serum, especially MMP-2, may have the effect of decreasing the risk of bronchopulmonary dysplasia in premature neonates.

Bronchial thermoplasty decreases airway remodelling by blocking epithelium-derived heat shock protein-60 secretion and protein arginine methyltransferase-1 in fibroblasts

Bronchial thermoplasty (BT) is to date the only therapy that provides a lasting reduction in airway wall remodelling. However, the mechanism of action of BT is not well understood. This study aimed to characterise the changes of remodelling regulating signalling pathways by BT in asthma.Bronchoalveolar lavage fluid (BALF) was obtained from eight patients with severe asthma before and after BT. Primary bronchial epithelial cells were isolated from 23 patients before (n=66) and after (n=62) BT. Epithelial cell culture supernatant (Epi.S) was collected and applied to primary fibroblasts.Epithelial cells obtained from asthma patients after BT proliferated significantly faster compared with epithelial cells obtained before BT. In airway fibroblasts, BALF or Epi.S obtained before BT increased CCAAT enhancer-binding protein-β (C/EBPβ) expression, thereby downregulating microRNA-19a. This upregulated extracellular signal-regulated kinase-1/2 (ERK1/2) expression, protein arginine methyltransferase-1 (PRMT1) expression, cell proliferation and mitochondrial mass. BALF or Epi.S obtained after BT reduced the expression of C/EBPβ, ERK1/2, peroxisome proliferator-activated receptor-γ coactivator-1α (PGC1α), PRMT1 and mitochondrial mass in airway fibroblasts. Proteome and transcriptome analyses indicated that epithelial cell-derived heat shock protein-60 (HSP60) is the main mediator of BT effects on fibroblasts. Further analysis suggested that HSP60 regulated PRMT1 expression, which was responsible for the increased mitochondrial mass and α-smooth muscle actin expression by asthmatic fibroblasts. These effects were ablated after BT. These results imply that BT reduces fibroblast remodelling through modifying the function of epithelial cells, especially by reducing HSP60 secretion and subsequent signalling pathways that regulate PRMT1 expression.We therefore hypothesise that BT decreases airway remodelling by blocking epithelium-derived HSP60 secretion and PRMT1 in fibroblasts.

Microphysiological systems modeling acute respiratory distress syndrome that capture mechanical force-induced injury-inflammation-repair

Complex in vitro models of the tissue microenvironment, termed microphysiological systems, have enormous potential to transform the process of discovering drugs and disease mechanisms. Such a paradigm shift is urgently needed in acute respiratory distress syndrome (ARDS), an acute lung condition with no successful therapies and a 40% mortality rate. Here, we consider how microphysiological systems could improve understanding of biological mechanisms driving ARDS and ultimately improve the success of therapies in clinical trials. We first discuss how microphysiological systems could explain the biological mechanisms underlying the segregation of ARDS patients into two clinically distinct phenotypes. Then, we contend that ARDS-mimetic microphysiological systems should recapitulate three critical aspects of the distal airway microenvironment, namely, mechanical force, inflammation, and fibrosis, and we review models that incorporate each of these aspects. Finally, we recognize the substantial challenges associated with combining inflammation, fibrosis, and/or mechanical force in microphysiological systems. Nevertheless, complex in vitro models are a novel paradigm for studying ARDS, and they could ultimately improve patient care.

Evidence for lung repair and regeneration in humans: key stem cells and therapeutic functions of fibroblast growth factors

Regeneration carries the idea of regrowing partially or completely a missing organ. Repair, on the other hand, allows restoring the function of an existing but failing organ. The recognition that human lungs can both repair and regenerate is quite novel, the concept has not been widely used to treat patients. We present evidence that the human adult lung does repair and regenerate and introduce different ways to harness this power. Various types of lung stem cells are capable of proliferating and differentiating upon injury driving the repair/regeneration process. Injury models, primarily in mice, combined with lineage tracing studies, have allowed the identification of these important cells. Some of these cells, such as basal cells, broncho-alveolar stem cells, and alveolar type 2 cells, rely on fibroblast growth factor (FGF) signaling for their survival, proliferation and/or differentiation. While preclinical studies have shown the therapeutic benefits of FGFs, a recent clinical trial for acute respiratory distress syndrome (ARDS) using intravenous injection of FGF7 did not report the expected beneficial effects. We discuss the potential reasons for these negative results and propose the rationale for new approaches for future clinical trials, such as delivery of FGFs to the damaged lungs through efficient inhalation systems, which may be more promising than systemic exposure to FGFs. While this change in the administration route presents a challenge, the therapeutic promises displayed by FGFs are worth the effort.

Equine bronchial fibroblasts enhance proliferation and differentiation of primary equine bronchial epithelial cells co-cultured under air-liquid interface

Interaction between epithelial cells and fibroblasts play a key role in wound repair and remodelling in the asthmatic airway epithelium. We present the establishment of a co-culture model using primary equine bronchial epithelial cells (EBECs) and equine bronchial fibroblasts (EBFs). EBFs at passage between 4 and 8 were seeded on the bottom of 24-well plates and treated with mitomycin C at 80% confluency. Then, freshly isolated (P0) or passaged (P1) EBECs were seeded on the upper surface of membrane inserts that had been placed inside the EBF-containing well plates and grown first under liquid-liquid interface (LLI) then under air-liquid interface (ALI) conditions to induce epithelial differentiation. Morphological, structural and functional markers were monitored in co-cultured P0 and P1 EBEC monolayers by phase-contrast microscopy, scanning and transmission electron microscopy, hematoxylin-eosin, immunocytochemistry as well as by measuring the transepithelial electrical resistance (TEER) and transepithelial transport of selected drugs. After about 15–20 days of co-culture at ALI, P₀ and P₁ EBEC monolayers showed pseudo-stratified architecture, presence of ciliated cells, typically honeycomb-like pattern of tight junction protein 1 (TJP1) expression, and intact selective barrier functions. Interestingly, some notable differences were observed in the behaviour of co-cultured EBECs (adhesion to culture support, growth rate, differentiation rate) as compared to our previously described EBEC mono-culture system, suggesting that cross-talk between epithelial cells and fibroblasts actually takes place in our current co-culture setup through paracrine signalling. The EBEC-EBF co-culture model described herein will offer the opportunity to investigate epithelial-mesenchymal cell interactions and underlying disease mechanisms in the equine airways, thereby leading to a better understanding of their relevance to pathophysiology and treatment of equine and human asthma.

The effects of oxygen concentration on cell death, anti-oxidant transcription, acute inflammation, and cell proliferation in precision-cut lung slices

Although animal models are often used in drug research, alternative experimental models are becoming more popular as they reduce animal use and suffering. Of particular interest are precision-cut lung slices, which refer to explants – with a reproducible thickness and diameter – that can be cultured ex vivo. Because lung slices (partially) reflect functional and structural features of whole tissue, they are often applied in the field of immunology, pharmacology, toxicology, and virology. Nevertheless, previous research failed to adequately address concerns with respect to the viability of lung slices. For instance, the effect of oxygen concentration on lung slice viability has never been thoroughly investigated. Therefore, the main goal of this study was to investigate the effect of oxygen concentration (20 vs. 80% O₂) on the degree of cell death, anti-oxidant transcription, acute inflammation, and cell proliferation in lung slices. According to the results, slices incubated at 20% O₂ displayed less cell death, anti-oxidant transcription, and acute inflammation, as well as more cell proliferation, demonstrating that these slices were considerably more viable than slices cultured at 80% O₂. These findings expand our knowledge on lung slices and their use as an alternative experimental model in drug research.

RAGE and AXL expression following secondhand smoke (SHS) exposure in mice

Aim and Purpose: Tobacco exposure is one of the top three global health risks leading to the development of chronic obstructive pulmonary disease (COPD). Although there is extensive research into the effects of cigarette smoke, the effect of secondhand smoke (SHS) in the lung remains limited. SHS induces receptors for advanced glycation end-products (RAGE) and an inflammatory response that leads to COPD characteristics. Semi-synthetic glycosaminoglycan ethers (SAGEs) are sulfated polysaccharides derived from hyaluronic acid that inhibit RAGE signaling. The growth arrest-specific 6 (Gas6) protein is known to induce dynamic cellular responses and is correlated with cell function. Gas6 binds to the AXL tyrosine kinase receptor and AXL-mediated signaling is implicated in proliferation and inflammation. This project's purpose was to study the correlation between RAGE, AXL, and Gas6 during SHS exposure in the lung. Methods: C57Bl/6 mice were exposed to SHS alone or SHS + SAGEs for 4 weeks and compared to control animals exposed to room air (RA). Results: Compared to controls we observed: 1) increased RAGE mRNA and protein expression in SHS-exposed lungs which was decreased by SAGEs; 2) decreased expression of total AXL, but highly elevated pAXL expression following exposure; 3) highly elevated Gas6 expression when RAGE was targeted by SAGEs during SHS exposure; 4) SHS-mediated BALF cellularity and inflammatory molecule elaboration; and 5) the induction of both RAGE and AXL by Gas6 in cell culture models. Conclusions: Our results suggest that there is a possible correlation between RAGE and AXL during SHS exposure. Additional research is critically needed that dissects the molecular interplay between these two important signaling cascades. At this point, the current studies provide insight into tobacco-mediated effects in the lung and clarify possible avenues for alleviating complications that could arise during SHS exposure such as those observed during COPD exacerbations.

Lats2-Underexpressing Bone Marrow-Derived Mesenchymal Stem Cells Ameliorate LPS-Induced Acute Lung Injury in Mice

The pathophysiology of the acute lung injury (ALI) is characterized by the damage of alveolar epithelial cells, which can be repaired by exogenous bone marrow-derived mesenchymal stem cells (BMSCs). However, the migration and differentiation abilities of BMSCs are not sufficient for the purpose, and a new approach that could strengthen the repair effects of BMSCs in ALI still needs to be clarified. We have previously proved that in vitro large tumor suppressor kinase 2- (Lats2-) underexpressing BMSCs may enhance their tissue repair effects in ALI; thus, in the present study, we tried to explore whether Lats2-underexpressing BMSCs could rescue lipopolysaccharide- (LPS-) induced ALI in vivo. BMSCs from C57BL/6 mice transfected with Lats2-interfering lentivirus vector or lentivirus blank controls were transplanted intratracheally into LPS-induced ALI mice. The retention and differentiation of BMSCs in the lung were evaluated by in vivo imaging, immunofluorescence staining, and Western blotting. The lung edema and permeability were assessed by lung wet weight/body weight ratio (LWW/BW) and measurements of proteins in bronchoalveolar lavage fluid (BALF) using ELISA. Acute lung inflammation was measured by the cytokines in the lung homogenate and BALF using RT-qPCR and ELISA, respectively. Lung injury was evaluated by HE staining and lung injury scoring. Pulmonary fibrosis was evaluated by Picrosirius red staining, immunohistochemistry for α-SMA and TGF-β1, and hydroxyproline assay and RT-qPCR for Col1α1 and Col3α1. Lats2-mediated inhibition of the Hippo pathway increased the retention of BMSCs and their differentiation toward type II alveolar epithelial cells in the lung. Furthermore, Lats2-underexpressing BMSCs improved lung edema, permeability of the lung epithelium, and lung inflammation. Finally, Lats2-underexpressing BMSCs alleviated lung injury and early pulmonary fibrosis. Our studies suggest that underexpression of Lats2 could further enhance the repair effects of BMSCs against epithelial impair and the therapeutic potential of BMSCs in ALI mice.

DNA replication in progenitor cells and epithelial regeneration after lung injury requires the oncoprotein MDM2

Depletion of epithelial cells after lung injury prompts proliferation and epithelial mesenchymal transition (EMT) of progenitor cells, and this repopulates the lost epithelial layer. To investigate the cell proliferative function of human oncoprotein MDM2, we generated mouse models targeting human MDM2 expression in either lung Club or alveolar cells after doxycycline treatment. We report that MDM2 expression in lung Club or alveolar cells activates DNA replication specifically in lung progenitor cells only after chemical- or radiation-induced lung injury, irrespective of their p53 status. Activation of DNA replication by MDM2 triggered by injury leads to proliferation of lung progenitor cells and restoration of the lost epithelial layers. Mouse lung with no Mdm2 allele loses its ability to replicate DNA, whereas loss of 1 Mdm2 allele compromises this function, demonstrating the requirement of endogenous MDM2. We show that the p53-independent ability of MDM2 to activate Akt signaling is essential for initiating DNA replication in lung progenitor cells. Furthermore, MDM2 activates the Notch signaling pathway and expression of EMT markers, indicative of epithelial regeneration. This is the first report to our knowledge demonstrating a direct p53-independent participation of MDM2 in progenitor cell proliferation and epithelial repair after lung injury, distinct from a p53-degrading antiapoptotic effect preventing injury.

USP9X promotes LPS-induced pulmonary epithelial barrier breakdown and hyperpermeability by activating an NF-κBp65 feedback loop

NF-κB is a central regulator of inflammatory and immune responses and has been shown to regulate transcription of several inflammatory factors as well as promote acute lung injury. However, the regulation of NF-κB signaling in acute lung injury has yet to be investigated. Human pulmonary alveolar epithelial cells (HPAEpiC) were treated with LPS to establish an acute lung injury model in vitro in which LPS stimulation resulted in pulmonary epithelial barrier breakdown and hyperpermeability. Cell viability was measured by CCK-8, and the transepithelial permeability was examined by measurement of transepithelial electrical resistance (TEER) and the transepithelial flux. Expression of ubiquitin-specific peptidase 9 X-linked (USP9X), zonula occludens (ZO-1), occludin and NF-κBp65, and the secretion of TNF-α and IL-1β were measured by Western blotting and ELISA, respectively. For in vivo studies, mice were intraperitoneally injected with LPS and/or NF-κB inhibitor pyrrolidine dithiocarbamate (PDTC). Lung tissues were harvested for hematoxylin-eosin staining and Western blotting, and bronchoalveolar lavage fluid (BALF) was harvested for ELISA. We found that treatment with LPS in HPAEpiC inhibited cell viability and induced the expression of USP9X. Interestingly, knockdown of USP9X and treatment with PDTC suppressed LPS-induced HPAEpiC injury. USP9X overexpression promoted NF-κB activation, while NF-κB inactivation inhibited USP9X transcription and HPAEpiC injury induced by USP9X overexpression. Furthermore, LPS also induced the expression of USP9X in lungs, which was inhibited by PDTC. Taken together, these results demonstrate a critical role of USP9X-NF-κBp65 loop in mediating LPS-induced acute lung injury and may serve as a potential therapeutic target in acute lung injury.

Insights into Early Recovery from Influenza Pneumonia by Spatial and Temporal Quantification of Putative Lung Regenerating Cells and by Lung Proteomics

During influenza pneumonia, the alveolar epithelial cells of the lungs are targeted by the influenza virus. The distal airway stem cells (DASCs) and proliferating alveolar type II (AT2) cells are reported to be putative lung repair cells. However, their relative spatial and temporal distribution is still unknown during influenza-induced acute lung injury. Here, we investigated the distribution of these cells, and concurrently performed global proteomic analysis of the infected lungs to elucidate and link the cellular and molecular events during influenza pneumonia recovery. BALB/c mice were infected with a sub-lethal dose of influenza H1N1 virus. From 5 to 25 days post-infection (dpi), mouse lungs were subjected to histopathologic and immunofluorescence analysis to probe for global distribution of lung repair cells (using P63 and KRT5 markers for DASCs; SPC and PCNA markers for AT2 cells). At 7 and 15 dpi, infected mouse lungs were also subjected to protein mass spectrometry for relative protein quantification. DASCs appeared only in the damaged area of the lung from 7 dpi onwards, reaching a peak at 21 dpi, and persisted until 25 dpi. However, no differentiation of DASCs to AT2 cells was observed by 25 dpi. In contrast, AT2 cells began proliferating from 7 dpi to replenish their population, especially within the boundary area between damaged and undamaged areas of the infected lungs. Mass spectrometry and gene ontology analysis revealed prominent innate immune responses at 7 dpi, which shifted towards adaptive immune responses by 15 dpi. Hence, proliferating AT2 cells but not DASCs contribute to AT2 cell regeneration following transition from innate to adaptive immune responses during the early phase of recovery from influenza pneumonia up to 25 dpi.

Lipoxin A4 ameliorates lipopolysaccharide-induced lung injury through stimulating epithelial proliferation, reducing epithelial cell apoptosis and inhibits epithelial-mesenchymal transition

Background

Acute respiratory distress syndrome (ARDS) is characterized by alveolar epithelial disruption. Lipoxins (LXs), as so-called “braking signals” of inflammation, are the first mediators identified to have dual anti-inflammatory and inflammatory pro-resolving properties.

Methods

In vivo, lipoxinA₄ was administrated intraperitoneally with 1 μg/per mouse after intra-tracheal LPS administration (10 mg/kg). Apoptosis, proliferation and epithelial–mesenchymal transition of AT II cells were measured by immunofluorescence. In vitro, primary human alveolar type II cells were used to model the effects of lipoxin A₄ upon proliferation, apoptosis and epithelial–mesenchymal transition.

Results

In vivo, lipoxin A₄ markedly promoted alveolar epithelial type II cells (AT II cells) proliferation, inhibited AT II cells apoptosis, reduced cleaved caspase-3 expression and epithelial–mesenchymal transition, with the outcome of attenuated LPS-induced lung injury. In vitro, lipoxin A₄ increased primary human alveolar epithelial type II cells (AT II cells) proliferation and reduced LPS induced AT II cells apoptosis. LipoxinA₄ also inhibited epithelial mesenchymal transition in response to TGF-β₁, which was lipoxin receptor dependent. In addition, Smad3 inhibitor (Sis3) and PI3K inhibitor (LY294002) treatment abolished the inhibitory effects of lipoxinA₄ on the epithelial mesenchymal transition of primary human AT II cells. Lipoxin A₄ significantly downregulated the expressions of p-AKT and p-Smad stimulated by TGF-β₁ in primary human AT II cells.

Conclusion

LipoxinA₄ attenuates lung injury via stimulating epithelial cell proliferation, reducing epithelial cell apoptosis and inhibits epithelial–mesenchymal transition.

Electronic supplementary material

The online version of this article (10.1186/s12931-019-1158-z) contains supplementary material, which is available to authorized users.

Blockade of EGFR Activation Promotes TNF-Induced Lung Epithelial Cell Apoptosis and Pulmonary Injury

Pneumonitis is the leading cause of death associated with the use of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (EGFR-TKIs) against non-small cell lung cancer (NSCLC). However, the risk factors and the mechanism underlying this toxicity have not been elucidated. Tumor necrosis factor (TNF) has been reported to transactivate EGFR in pulmonary epithelial cells. Hence, we aimed to test the hypothesis that EGFR tyrosine kinase activity regulates TNF-mediated bronchial epithelial cell survival, and that inhibition of EGFR activity increases TNF-induced lung epithelial cell apoptosis. We used surfactant protein C (SPC)-TNF transgenic (tg) mice which overexpress TNF in the lungs. In this model, gefitinib, an EGFR-TKI, enhanced lung epithelial cell apoptosis and lymphocytic inflammation, indicating that EGFR tyrosine kinase prevents TNF-induced lung injury. Furthermore, IL-17A was significantly upregulated by gefitinib in SPC-TNF tg mice and p38MAPK activation was observed, indicative of a pathway involved in lung epithelial cell apoptosis. Moreover, in lung epithelial cells, BEAS-2B, TNF stimulated EGFR transactivation via the TNF-α-converting enzyme in a manner that requires heparin binding (HB)-EGF and transforming growth factor (TGF)-α. These novel findings have significant implications in understanding the role of EGFR in maintaining human bronchial epithelial cell homeostasis and in NSCLC treatment.

Major Effect of Oxidative Stress on the Male, but Not Female, SP-A1 Type II Cell miRNome

Pulmonary surfactant protein A (SP-A) plays an important role in surfactant metabolism and lung innate immunity. In humans there are two proteins, SP-A1 and SP-A2, encoded by SFTPA1 and SFTPA2, respectively, which are produced by the alveolar type II cells (T2C). We sought to investigate the differential influence of SP-A1 and SP-A2 in T2C miRNome under oxidative stress (OxS). SP-A knock out (KO) and hTG male and female mice expressing SP-A1 or SP-A2 as well as gonadectomized (Gx) mice were exposed to O₃-induced oxidative stress (OxS) or filtered air (FA). Expression of miRNAs and mRNAs was measured in the T2C of experimental animals. (a) In SP-A1 males after normalizing to KO males, significant changes were observed in the miRNome in terms of sex-OxS effects, with 24 miRNAs being differentially expressed under OxS. (b) The mRNA targets of the dysregulated miRNAs included Ago2, Ddx20, Plcg2, Irs1, Elf2, Jak2, Map2k4, Bcl2, Ccnd1, and Vhl. We validated the expression levels of these transcripts, and observed that the mRNA levels of all of these targets were unaffected in SP-A1 T2C but six of these were significantly upregulated in the KO (except Bcl2 that was downregulated). (c) Gondadectomy had a major effect on the expression of miRNAs and in three of the mRNA targets (Irs1, Bcl2, and Vhl). Ccnd1 was upregulated in KO regardless of Gx. (d) The targets of the significantly changed miRNAs are involved in several pathways including MAPK signaling pathway, cell cycle, anti-apoptosis, and other. In conclusion, in response to OxS, SP-A1 and male hormones appear to have a major effect in the T2C miRNome.

A Modular Cytokine Analysis Method Reveals Novel Associations With Clinical Phenotypes and Identifies Sets of Co-signaling Cytokines Across Influenza Natural Infection Cohorts and Healthy Controls

Cytokines and chemokines are key signaling molecules of the immune system. Recent technological advances enable measurement of multiplexed cytokine profiles in biological samples. These profiles can then be used to identify potential biomarkers of a variety of clinical phenotypes. However, testing for such associations for each cytokine separately ignores the highly context-dependent covariation in cytokine secretion and decreases statistical power to detect associations due to multiple hypothesis testing. Here we present CytoMod-a novel data-driven approach for analysis of cytokine profiles that uses unsupervised clustering and regression to identify putative functional modules of co-signaling cytokines. Each module represents a biosignature of co-signaling cytokines. We applied this approach to three independent clinical cohorts of subjects naturally infected with influenza in which cytokine profiles and clinical phenotypes were collected. We found that in two out of three cohorts, cytokine modules were significantly associated with clinical phenotypes, and in many cases these associations were stronger than the associations of the individual cytokines within them. By comparing cytokine modules across datasets, we identified cytokine "cores"-specific subsets of co-expressed cytokines that clustered together across the three cohorts. Cytokine cores were also associated with clinical phenotypes. Interestingly, most of these cores were also co-expressed in a cohort of healthy controls, suggesting that in part, patterns of cytokine co-signaling may be generalizable. CytoMod can be readily applied to any cytokine profile dataset regardless of measurement technology, increases the statistical power to detect associations with clinical phenotypes and may help shed light on the complex co-signaling networks of cytokines in both health and infection.

Andrographolide antagonizes the cigarette smoke-induced epithelial-mesenchymal transition and pulmonary dysfunction through anti-inflammatory inhibiting HOTAIR

In cells of the lung surface, cigarette smoke (CS) induces inflammatory and epithelial-mesenchymal transition (EMT), effects that are related to pulmonary dysfunction and Chronic obstructive pulmonary disease (COPD). However, the molecular mechanisms involved remain largely unknown, and potential therapeutic approaches are under development. In the present study, with cell culture and animal studies, we showed that CS exposure causes pulmonary dysfunction and airway remodeling with inflammatory cell infiltration. Consistent with these pulmonary lesions, the inflammatory factors interleukin-6 (IL-6) and interleukin-8 (IL-8) were increased in mice exposed to CS for 4 days. Accordingly, downstream signal transducer and activator of transcription 3 (STAT3) was activated, which up-regulated expression of the lncRNA HOTAIR, and enhancer of zeste homolog 2 (EZH2). In addition, CS exposure led to decreased levels of E-cadherin and to increased N-cadherin, vimentin, and α-SMA, indicating that the EMT was induced in mouse lung tissues. These effects, including increases of IL-6 and HOTAIR, were confirmed in human bronchial epithelial (HBE) cells treated with cigarette smoke extract (CSE). Finally, we established that, in HBE cells, andrographolide reversed the CSE-induced EMT via decreasing IL-6 levels and, in an animal model, prevented CS-induced lung inflammation and small airway remodeling, indicating that it has potential clinical application for CS-induced pulmonary dysfunction and COPD.

Andrographolide prevents human nucleus pulposus cells against degeneration by inhibiting the NF-κB pathway

Intervertebral disc degeneration (IDD) is among the most common spinal disorders, pathologically characterized by excessive cell apoptosis and production of proinflammatory factors. Pharmacological targeting of nucleus pulposus (NP) degeneration may hold promise in IDD therapy, but it is limited by adverse side effects and nonspecificity of drugs. In this study, we used a natural compound, andrographolide (ANDRO), which has been widely used to intervene inflammatory and apoptotic diseases in the investigation of NP degeneration based on IDD-patients-derived NP cells by lipopolysaccharide (LPS) treatment for the preservation of degeneration. The results showed that LPS maintained the degeneration status of NP cells as evidenced by a high apoptosis rate and the expression of degenerative and inflammatory mediators after LPS treatment. ANDRO reversed the effects of LPS-caused degeneration of NP cells and maintained the phenotype of NP cells, as demonstrated by flow cytometry, degenerative mediators (ADAMTS4 and ADAMTS5), inflammatory factors (COX2, PGE2, MMP-13, and MMP-3), biomarkers of NP cells (SOX9, ACAN, and COL2A1) expressions, and glycosaminoglycan secretion. We also found the involvement of the nuclear factor kappa-light-chain-enhancer of the activated B cells (NF-κB) pathway in ANDRO treatment, indicating that ANDRO prevented the LPS-preserved degeneration of NP cells by inhibiting the NF-κB pathway. This study may provide a reference for clinic medication of IDD therapy.

Epithelial⁻Mesenchymal Transition in the Pathogenesis of Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a serious disease of the lung, which leads to extensive parenchymal scarring and death from respiratory failure. The most accepted hypothesis for IPF pathogenesis relies on the inability of the alveolar epithelium to regenerate after injury. Alveolar epithelial cells become apoptotic and rare, fibroblasts/myofibroblasts accumulate and extracellular matrix (ECM) is deposited in response to the aberrant activation of several pathways that are physiologically implicated in alveologenesis and repair but also favor the creation of excessive fibrosis via different mechanisms, including epithelial⁻mesenchymal transition (EMT). EMT is a pathophysiological process in which epithelial cells lose part of their characteristics and markers, while gaining mesenchymal ones. A role for EMT in the pathogenesis of IPF has been widely hypothesized and indirectly demonstrated; however, precise definition of its mechanisms and relevance has been hindered by the lack of a reliable animal model and needs further studies. The overall available evidence conceptualizes EMT as an alternative cell and tissue normal regeneration, which could open the way to novel diagnostic and prognostic biomarkers, as well as to more effective treatment options.

Effects of Agricultural Organic Dusts on Human Lung-Resident Mesenchymal Stem (Stromal) Cell Function

Agricultural organic dust exposures trigger harmful airway inflammation, and workers experiencing repetitive dust exposures are at increased risk for lung disease. Mesenchymal stem/stromal cells (MSCs) regulate wound repair processes in the lung, and may contribute to either proresolution or -fibrotic lung responses. It is unknown how organic dust exposures alter lung-resident MSC activation and proinflammatory versus prorepair programs in the lung. To address this gap in knowledge, we isolated human lung-resident MSC from lung tissue. Cells were stimulated with aqueous extracts of organic dusts (DE) derived from swine confinement facilities and were assessed for changes in proliferative and migratory capacities, and production of proinflammatory and prorepair mediators. Through these investigations, we found that DE induces significant release of proinflammatory mediators TNF-α, IL-6, IL-8, and matrix metalloproteases, while also inducing the production of prorepair mediators amphiregulin, FGF-10, and resolvin D1. In addition, DE significantly reduced the growth and migratory capacities of lung-resident MSC. Together, these investigations indicate lung-resident MSC activation and wound repair activities are altered by organic dust exposures. These findings warrant future investigations to assess how organic dusts affect lung-resident mesenchymal stem/stromal cell function and impact airway inflammation, injury, and repair during agricultural aerosol exposures.

Association of Matrix Metalloproteinase 9 (MMP-9) Polymorphisms with Asthma Risk: A Meta-Analysis

Published data on the association between MMP-9 polymorphisms (−1562 C > T, rs3918242; Gln279Arg, rs17576 Arg668Gln, rs17577) and asthma susceptibility are inconclusive. To derive a more precise estimation of this association, a meta-analysis was performed. A literature search was conducted in PubMed, Web of Science, EMBASE, Wanfang, and China National Knowledge Infrastructure (CNKI) databases to identify eligible studies. The pooled odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were used to calculate the strength of association. Sensitivity analysis was performed to evaluate the influence of individual studies on the overall effect estimates, and funnel plots and Egger's test were inspected for indication of publication bias. Seven studies with 1592 asthma patients and 1987 controls were finally identified. Overall, we found no significant association between −1562 C > T, rs3918242 polymorphism, and asthma susceptibility in any of the genetic model comparisons. After categorizing studies into different subgroups on the basis of ethnicity and age, there is still no significant association. For the Gln279Arg, rs17576 polymorphism, there seems to be a significant association in the allelic genetic model in regard to the P value (OR = 1.11, 95% CI = 1.00–1.22, I² = 0%, P_(Z)=0.044); however, the value of lower 95% CI is 1.0. For the Arg668Gln, rs17577 polymorphism, a high significant association was observed in the dominant model comparison (OR = 1.65, 95% CI = 1.28–2.11, I² = 22.50%, P_(Z)=0), recessive model comparison (OR = 2.40, 95% CI = 1.23–4.72, I² = 0%, P_(Z)=0.011), homozygote genotype comparison (OR = 2.69, 95% CI = 1.36–5.33, I² = 0%, P_(Z)=0.004), and allelic genetic model (OR = 1.59, 95% CI = 1.29–1.97, I² = 36.9%, P_(Z)=0). Sensitivity analysis demonstrated the stability of our results, and publication bias was not evident. The present meta-analysis suggests that MMP-9 Arg668Gln, rs17577 polymorphism may be the risk factor for asthma susceptibility.

Alveolar-Capillary Membrane-Related Pulmonary Cells as a Target in Endotoxin-Induced Acute Lung Injury

The main function of the lungs is oxygen transport from the atmosphere into the blood circulation, while it is necessary to keep the pulmonary tissue relatively free of pathogens. This is a difficult task because the respiratory system is constantly exposed to harmful substances entering the lungs by inhalation or via the blood stream. Individual types of lung cells are equipped with the mechanisms that maintain pulmonary homeostasis. Because of the clinical significance of acute respiratory distress syndrome (ARDS) the article refers to the physiological role of alveolar epithelial cells type I and II, endothelial cells, alveolar macrophages, and fibroblasts. However, all these cells can be damaged by lipopolysaccharide (LPS) which can reach the airspaces as the major component of the outer membrane of Gram-negative bacteria, and lead to local and systemic inflammation and toxicity. We also highlight a negative effect of LPS on lung cells related to alveolar-capillary barrier and their response to LPS exposure. Additionally, we describe the molecular mechanism of LPS signal transduction pathway in lung cells.

Spatial and Temporal Mapping of Human Innate Lymphoid Cells Reveals Elements of Tissue Specificity

Innate lymphoid cells (ILC) play critical roles in regulating immunity, inflammation, and tissue homeostasis in mice. However, limited access to non-diseased human tissues has hindered efforts to profile anatomically-distinct ILCs in humans. Through flow cytometric and transcriptional analyses of lymphoid, mucosal, and metabolic tissues from previously healthy human organ donors, here we have provided a map of human ILC heterogeneity across multiple anatomical sites. In contrast to mice, human ILCs are less strictly compartmentalized and tissue localization selectively impacts ILC distribution in a subset-dependent manner. Tissue-specific distinctions are particularly apparent for ILC1 populations, whose distribution was markedly altered in obesity or aging. Furthermore, the degree of ILC1 population heterogeneity differed substantially in lymphoid versus mucosal sites. Together, these analyses comprise a comprehensive characterization of the spatial and temporal dynamics regulating the anatomical distribution, subset heterogeneity, and functional potential of ILCs in non-diseased human tissues.

Building and Regenerating the Lung Cell by Cell

The unique architecture of the mammalian lung is required for adaptation to air breathing at birth and thereafter. Understanding the cellular and molecular mechanisms controlling its morphogenesis provides the framework for understanding the pathogenesis of acute and chronic lung diseases. Recent single-cell RNA sequencing data and high-resolution imaging identify the remarkable heterogeneity of pulmonary cell types and provides cell selective gene expression underlying lung development. We will address fundamental issues related to the diversity of pulmonary cells, to the formation and function of the mammalian lung, and will review recent advances regarding the cellular and molecular pathways involved in lung organogenesis. What cells form the lung in the early embryo? How are cell proliferation, migration, and differentiation regulated during lung morphogenesis? How do cells interact during lung formation and repair? How do signaling and transcriptional programs determine cell-cell interactions necessary for lung morphogenesis and function?

Epithelial cells exert differential traction stress in response to substrate stiffness

Epithelial wound healing is essential for maintaining the function and clarity of the cornea. Successful repair after injury involves the coordinated movements of cell sheets over the wounded region. While collective migration has been the focus of studies, the effects that environmental changes have on this form of movement are poorly understood. To examine the role of substrate compliancy on multi-layered epithelial sheet migration, we performed traction force and confocal microscopy to determine differences in traction forces and to examine focal adhesions on synthetic and biological substrates. The leading edges of corneal epithelial sheets undergo retraction or contraction prior to migration, and alterations in the sheet's stiffness are affected by the amount of force exerted by cells at the leading edge. On substrates of 30 kPa, cells exhibited greater and more rapid movement than on substrates of 8 kPa, which are similar to that of the corneal basement membrane. Vinculin and its phosphorylated residue Y1065 were prominent along the basal surface of migrating cells, while Y822 was prominent between neighboring cells along the leading edge. Vinculin localization was diffuse on a substrate where the basement membrane was removed. Furthermore, when cells were cultured on fibronectin-coated acrylamide substrates of 8 and 50 kPa and then wounded, there was an injury-induced phosphorylation of Y1065 and substrate dependent changes in the number and size of vinculin containing focal adhesions. These results demonstrate that changes in substrate stiffness affected traction forces and vinculin dynamics, which potentially could contribute to the delayed healing response associated with certain corneal pathologies.

A pilot study of blood microRNAs and lung function in young healthy adults with fine particulate matter exposure

Fine particulate exposure (PM_2.5) is a risk factor of pulmonary diseases such as chronic obstructive pulmonary disease (COPD), but the mechanism underlying was not clear. Recent studies found blood microRNAs (miRNAs) are potential indicators of either COPD or PM_2.5 exposure, but these results had no unified conclusions. We suggested it was more targeted to find disease related miRNAs first and then observe them during PM_2.5 exposure. Firstly, in order to screen COPD associated miRNAs, we identified differentially expressed blood miRNAs contrasting COPD participants (n=6) without diagnose of COPD or related treatment before and matched control (n=6). In total, 21 miRNAs were differentially expressed in COPD individuals and expression of miR-495-3p, miR-223-5p and miR-194-3p were further validated using qRT-PCR. The results showed miR-495-3p and miR-223-5p significantly increased whereas miR-194-3p decreased marginally (P=0.058) in COPD participants. Secondly, in order to recognize the relevance between these miRNAs and PM_2.5 exposure, we designed an independent time-series study nested within "low-high-low" pollution levels. The expression of blood miR-495-3p, miR-223-5p and miR-194-3p were detected before and after exposure (n=8). The results showed expression of miR-223-5p increased significantly while expression of miR-194-3p decreased significantly after exposure. The Pearson analysis showed only miR-194-3p showed a positive statistically correlation with lag0-1 forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) during exposure of PM_2.5. So miR-194-3p might be a potential regulator in the toxicological pathways of both PM_2.5 exposure and COPD. As this was a pilot study, formal and large-scale studies should be planned in the future.

IL-13 signaling through IL-13 receptor α2 mediates airway epithelial wound repair

Asthma is an airway inflammatory disease characterized by epithelial barrier dysfunction and airway remodeling. Interleukin-13 (IL-13) is a pleiotropic cytokine shown to contribute to features of airway remodeling. We have previously demonstrated that IL-13 is an important mediator of normal airway epithelial repair and health. The role of IL-13 signaling via its receptor subunits (IL-13Rα1/IL-4Rα and IL-13Rα2) in airway epithelial repair and restoration of intact barrier function is not well understood and was investigated in this study using in vitro models. The blocking of IL-13 signaling via IL-13Rα2 significantly reduced airway epithelial repair by 24 h post-mechanical wounding in 1HAEo^- cells. Expression and release of repair-mediating growth factor, heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF), and subsequent activation of EGF receptor (EGFR) were also significantly reduced in response to wounding when IL-13Rα2 was blocked. Our data support that IL-13 signals via IL-13Rα2 to mediate normal airway epithelial repair via HB-EGF-dependent activation of EGFR. In human donor lung tissues, we observed that airway epithelium of asthmatics expressed significantly decreased levels of IL-13Rα2 and increased levels of IL-13Rα1 compared with nonasthmatics. Dysregulated expression of IL-13 receptor subunits in the airways of asthmatics may thus contribute to the epithelial barrier dysfunction observed in asthma.-Yang, S. J., Allahverdian, S., Saunders, A. D. R., Liu, E., Dorscheid, D. R. IL-13 signaling through IL-13 receptor α2 mediates airway epithelial wound repair.

Linking Physiological Biomarkers of Ventilator-Induced Lung Injury to a Rich-Get-Richer Mechanism of Injury Progression

Mechanical ventilation is a crucial tool in the management of acute respiratory distress syndrome, yet it may itself also further damage the lung in a phenomenon known as ventilator-induced lung injury (VILI). We have previously shown in mice that volutrauma and atelectrauma act synergistically to cause VILI. We have also postulated that this synergy arises because of a rich-get-richer mechanism in which repetitive lung recruitment generates initial small holes in the blood-gas barrier which are then expanded by over-distension in a manner that favors large holes over small ones. In order to understand the causal link between this process and the derangements in lung mechanics associated with VILI, we developed a mathematical model that incorporates both atelectrauma and volutrauma to predict how the propensity of the lung to derecruit depends on the accumulation of plasma-derived fluid and proteins in the airspaces. We found that the model accurately predicts derecruitment in mice with experimentally induced VILI.

Characterizing well-differentiated culture of primary human nasal epithelial cells for use in wound healing assays

The nasal epithelium is the initial contact between the external environment and the respiratory tract and how it responds to noxious stimuli and repairs epithelial damage is important. Growing airway epithelial cells in culture at air-liquid interface allows for a physiologically relevant model of the human upper airways. The aim of the present study was to characterize human primary nasal epithelial cells grown at the air-liquid interface and establish a model for use in wound healing assays. This study determined the time required for full differentiation of nasal epithelial cells in an air-liquid interface culture to be at least 7 weeks using the standardized B-ALI media. Also, a model was established that studied the response to wounding and the effect of EGFR inhibition on this process. Nasal epithelial cultures from healthy subjects were differentiated at air-liquid interface and manually wounded. Wounds were monitored over time to complete closure using a time lapse imaging microscope with cultures identified to have a rate of wound healing above 2.5%/h independent of initial wound size. EGFR inhibition caused the rate of wound healing to drop a significant 4.6%/h with there being no closure of the wound after 48 h. The robust model established in this study will be essential for studying factors influencing wound healing, including host disease status and environmental exposures in the future.

Cytokines and radiation-induced pulmonary injuries

Radiation therapy is one of the most common treatment strategies for thorax malignancies. One of the considerable limitations of this therapy is its toxicity to normal tissue. The lung is the major dose-limiting organ for radiotherapy. That is because ionizing radiation produces reactive oxygen species that induce lesions, and not only is tumor tissue damaged, but overwhelming inflammatory lung damage can occur in the alveolar epithelium and capillary endothelium. This damage may result in radiation-induced pneumonitis and/or fibrosis. While describing the lung response to irradiation generally, the main focus of this review is on cytokines and their roles and functions within the individual stages. We discuss the relationship between radiation and cytokines and their direct and indirect effects on the formation and development of radiation injuries. Although this topic has been intensively studied and discussed for years, we still do not completely understand the roles of cytokines. Experimental data on cytokine involvement are fragmented across a large number of experimental studies; hence, the need for this review of the current knowledge. Cytokines are considered not only as molecular factors involved in the signaling network in pathological processes, but also for their diagnostic potential. A concentrated effort has been made to identify the significant immune system proteins showing positive correlation between serum levels and tissue damages. Elucidating the correlations between the extent and nature of radiation-induced pulmonary injuries and the levels of one or more key cytokines that initiate and control those damages may improve the efficacy of radiotherapy in cancer treatment and ultimately the well-being of patients.

Lung Repair and Regeneration in ARDS: Role of PECAM1 and Wnt Signaling

ARDS is an acute inflammatory pulmonary process triggered by severe pulmonary and systemic insults to the alveolar-capillary membrane. This causes increased vascular permeability and the development of interstitial and alveolar protein-rich edema, leading to acute hypoxemic respiratory failure. Supportive treatment includes the use of lung-protective ventilatory strategies that decrease the work of breathing, can improve oxygenation, and minimize ventilator-induced lung injury. Despite substantial advances in supportive measures, there are no specific pharmacologic treatments for ARDS, and the overall hospital mortality rate remains about 40% in most series. The pathophysiology of ARDS involves interactions among multiple mechanisms, including immune cell infiltration, cytokine storm, alveolar-capillary barrier disruption, cell apoptosis, and the development of fibrosis. Here we review some new developments in the molecular basis of lung injury, with a focus on possible novel pharmacologic interventions aimed at improving the outcomes of patients with ARDS. Our focus is on platelet-endothelial cell adhesion molecule-1, which contributes to the maintenance and restoration of vascular integrity following barrier disruption. We also highlight the wingless-related integration site signaling pathway, which appears to be a central mechanism for lung healing as well as for fibrotic development.

Selective activation and proliferation of a quiescent stem cell population in the neuroepithelial body microenvironment

BACKGROUND

The microenvironment (ME) of neuroepithelial bodies (NEBs) harbors densely innervated groups of pulmonary neuroendocrine cells that are covered by Clara-like cells (CLCs) and is believed to be important during development and for adult airway epithelial repair after severe injury. Yet, little is known about its potential stem cell characteristics in healthy postnatal lungs.

METHODS

Transient mild lung inflammation was induced in mice via a single low-dose intratracheal instillation of lipopolysaccharide (LPS). Bronchoalveolar lavage fluid (BALF), collected 16 h after LPS instillation, was used to challenge the NEB ME in ex vivo lung slices of control mice. Proliferating cells in the NEB ME were identified and quantified following simultaneous LPS instillation and BrdU injection.

RESULTS

The applied LPS protocol induced very mild and transient lung injury. Challenge of lung slices with BALF of LPS-treated mice resulted in selective Ca²⁺-mediated activation of CLCs in the NEB ME of control mice. Forty-eight hours after LPS challenge, a remarkably selective and significant increase in the number of divided (BrdU-labeled) cells surrounding NEBs was observed in lung sections of LPS-challenged mice. Proliferating cells were identified as CLCs.

CONCLUSIONS

A highly reproducible and minimally invasive lung inflammation model was validated for inducing selective activation of a quiescent stem cell population in the NEB ME. The model creates new opportunities for unraveling the cellular mechanisms/pathways regulating silencing, activation, proliferation and differentiation of this unique postnatal airway epithelial stem cell population.

Downregulation of microRNA‑30a in bronchoalveolar lavage fluid from idiopathic pulmonary fibrosis patients

MicroRNAs (miRs) are short, highly conserved small noncoding RNA molecules with fundamental roles in regulating gene expression. To identify miR biomarkers associated with idiopathic pulmonary fibrosis (IPF), the expression pattern of miRs in exosomes from bronchoalveolar lavage fluid (BALF) of elderly patients with IPF were evaluated. High‑throughput quantitative detection of miR expression using a microarray indicated that miR‑125b, miR‑128, miR‑21, miR‑100, miR‑140‑3p and miR‑374b were upregulated in patients with IPF, while let‑7d, miR‑103, miR‑26 and miR‑30a‑5p were downregulated. The expression level of miR‑30a‑5p was further examined, and its potential target genes were predicted using target gene prediction analysis software. A direct regulatory association was confirmed between miR‑30a‑5p and TGF‑β activated kinase 1/MAP3K7 binding protein 3 (TAB3) via a dual‑luciferase reporter assay. Overexpression of miR‑30a‑5p decreased TAB3, α‑smooth muscle actin and fibronectin expression in A549 cells with or without transforming growth factor‑β1 treatment. The decreased expression of miR‑30a in the BALF of patients with IPF, along with the consequential increase in TAB3 expression, may be a crucial factor in IPF progression.

Temporal differentiation of bovine airway epithelial cells grown at an air-liquid interface

There is an urgent need to develop improved, physiologically-relevant in vitro models of airway epithelia with which to better understand the pathological processes associated with infection, allergies and toxicological insults of the respiratory tract of both humans and domesticated animals. In the present study, we have characterised the proliferation and differentiation of primary bovine bronchial epithelial cells (BBECs) grown at an air-liquid interface (ALI) at three-day intervals over a period of 42 days from the introduction of the ALI. The differentiated BBEC model was highly representative of the ex vivo epithelium from which the epithelial cells were derived; a columnar, pseudostratified epithelium that was highly reflective of native airway epithelium was formed which comprised ciliated, goblet and basal cells. The hallmark defences of the respiratory tract, namely barrier function and mucociliary clearance, were present, thus demonstrating that the model is an excellent mimic of bovine respiratory epithelium. The epithelium was fully differentiated by day 21 post-ALI and, crucially, remained healthy and stable for a further 21 days. Thus, the differentiated BBEC model has a three-week window which will allow wide-ranging and long-term experiments to be performed in the fields of infection, toxicology or general airway physiology.