Enhanced migration of fibroblasts derived from lungs with fibrotic lesions

Involvement of lysophosphatidic acid-LPA1-YAP signaling in healthy and pathological FAPs migration

Skeletal muscle fibrosis is defined as the excessive accumulation of extracellular matrix (ECM) components and is a hallmark of muscular dystrophies. Fibro-adipogenic progenitors (FAPs) are the main source of ECM, and thus have been strongly implicated in fibrogenesis. In skeletal muscle fibrotic models, including muscular dystrophies, FAPs undergo dysregulations in terms of proliferation, differentiation, and apoptosis, however few studies have explored the impact of FAPs migration. Here, we studied fibroblast and FAPs migration and identified lysophosphatidic acid (LPA), a signaling lipid central to skeletal muscle fibrogenesis, as a significant migration inductor. We identified LPA receptor 1 (LPA1) mediated signaling as crucial for this effect through a mechanism dependent on the Hippo pathway, another pathway implicated in fibrosis across diverse tissues. This cross-talk favors the activation of the Yes-associated protein 1 (YAP) and Transcriptional coactivator with PDZ-binding motif (TAZ), leading to increased expression of fibrosis-associated genes. This study reveals the role of YAP in LPA-mediated fibrotic responses as inhibition of YAP transcriptional coactivator activity hinders LPA-induced migration in fibroblasts and FAPs. Moreover, we found that FAPs derived from the mdx4cv mice, a murine model of Duchenne muscular dystrophy, display a heightened migratory phenotype due to enhanced LPA signaling compared to wild-type FAPs. Remarkably, we found that the inhibition of LPA1 or YAP transcriptional coactivator activity in mdx4cv FAPs reverts this phenotype. In summary, the identified LPA-LPA1-YAP pathway emerges as a critical driver of skeletal muscle FAPs migration and provides insights into potential novel targets to mitigate fibrosis in muscular dystrophies.

Sophocarpine alleviates intestinal fibrosis via inhibition of inflammation and fibroblast into myofibroblast transition by targeting the Sirt1/p65 signaling axis

In this study, we used alkaloids from Sophora flavescens to inhibit the SASP, leading to fibroblast-into-myofibroblast transition (FMT) to maintain intestinal mucosal homeostasis in vitro and in vivo. We used western blotting (WB) and immunofluorescence staining (IF) to assess whether five kinds of alkaloids inhibit the major inflammatory pathways and chose the most effective compound (sophocarpine; SPC) to ameliorate colorectal inflammation in a dextran sulfate sodium (DSS)-induced UC mouse model. IF, Immunohistochemistry staining (IHC), WB, disease activity index (DAI), and enzyme-linked immunosorbent assay (ELISA) were conducted to investigate the mechanism of action of this compound. Next, we detected the pharmacological activity of SPC on the senescence-associated secretory phenotypes (SASP) and FMT in interleukin 6 (IL-6)-induced senescence-like fibroblasts and discussed the mucosal protection ability of SPC on a fibroblast-epithelium/organoid coculture system and organ-on-chip system. Taken together, our results provide evidence that SPC alleviates the inflammatory response, improves intestinal fibrosis and maintains intestinal mucosal homeostasis in vivo. Meanwhile, SPC was able to prevent IL-6-induced SASP and FMT in fibroblasts, maintain the expression of TJ proteins, and inhibit inflammation and genomic stability of colonic mucosal epithelial cells by activating SIRT1 in vitro. In conclusion, SPC treatment attenuates intestinal fibrosis by regulating SIRT1/NF-κB p65 signaling, and it might be a promising therapeutic agent for inflammatory bowel disease.

Dysregulated bidirectional epithelial-mesenchymal crosstalk: a core determinant of lung fibrosis progression

Progressive lung fibrosis is characterised by dysregulated extracellular matrix (ECM) homeostasis. Understanding of disease pathogenesis remains limited and has prevented the development of effective treatments. While an abnormal wound healing response is strongly implicated in lung fibrosis initiation, factors that determine why fibrosis progresses rather than regular tissue repair occurs are not fully explained. Within human lung fibrosis there is evidence of altered epithelial and mesenchymal lung populations as well as cells undergoing epithelial-mesenchymal transition (EMT), a dynamic and reversible biological process by which epithelial cells lose their cell polarity and down-regulate cadherin-mediated cell-cell adhesion to gain migratory properties. This review will focus upon the role of EMT and dysregulated epithelial-mesenchymal crosstalk in progressive lung fibrosis.

Novel bioprinted 3D model to human fibrosis investigation

Fibrosis is shared in multiple diseases with progressive tissue stiffening, organ failure and limited therapeutic options. This unmet need is also due to the lack of adequate pre-clinical models to mimic fibrosis and to be challenged novel by anti-fibrotic therapeutic venues. Here using bioprinting, we designed a novel 3D model where normal human healthy fibroblasts have been encapsulated in type I collagen. After stimulation by Transforming Growth factor beta (TGFβ), embedded cells differentiated into myofibroblasts and enhanced the contractile activity, as confirmed by the high level of α - smooth muscle actin (αSMA) and F-actin expression. As functional assays, SEM analysis revealed that after TGFβ stimulus the 3D microarchitecture of the scaffold was dramatically remolded with an increased fibronectin deposition with an abnormal collagen fibrillar pattern. Picrius Sirius Red staining additionally revealed that TGFβ stimulation enhanced of two logarithm the collagen fibrils neoformation in comparison with control. These data indicate that by bioprinting technology, it is possible to generate a reproducible and functional 3D platform to mimic fibrosis as key tool for drug discovery and impacting on animal experimentation and reducing costs and time in addressing fibrosis.

Fibroblasts are not just fibroblasts: clear differences between dermal and pulmonary fibroblasts' response to fibrotic growth factors

Systemic Sclerosis (SSc) hallmark is skin fibrosis, but up to 80% of the patients have fibrotic involvement in the pulmonary system. Antifibrotic drugs which have failed in a general SSc population have now been approved in patients with SSc-associated interstitial lung disease (ILD). This indicates that the fibrotic progression and regulation of fibroblasts likely depend on local factors specific to the tissue type. This study investigated the difference between dermal and pulmonary fibroblasts in a fibrotic setting, mimicking the extracellular matrix. Primary healthy fibroblasts were grown in a crowded environment and stimulated with TGF-β1 and PDGF-AB. The viability, morphology, migration capacity, extracellular matrix formation, and gene expression were assessed: TGF-β1 only increased the viability in the dermal fibroblasts. PDGF-AB increased the migration capacity of dermal fibroblasts while the pulmonary fibroblasts fully migrated. The morphology of the fibroblasts was different without stimulation. TGF-β1 increased the formation of type III collagen in pulmonary fibroblasts, while PDGF-AB increased it in dermal fibroblasts. The gene expression trend of type VI collagen was the opposite after PDGF-AB stimulation. The fibroblasts exhibit different response profiles to TGF-β1 and PDGF-AB; this suggests that drivers of fibrosis are tissue-dependent, which needs to be considered in drug development.

Mitochondrial fission and bioenergetics mediate human lung fibroblast durotaxis

Pulmonary fibrosis is characterized by stiffening of the extracellular matrix. Fibroblasts migrate in the direction of greater stiffness, a phenomenon termed durotaxis. The mechanically guided fibroblast migration could be a crucial step in the progression of lung fibrosis. In this study, we found primary human lung fibroblasts sense increasing matrix stiffness with a change of mitochondrial dynamics in favor of mitochondrial fission and increased production of ATP. Mitochondria polarize in the direction of a physiologically relevant stiffness gradient, with conspicuous localization to the leading edge, primarily lamellipodia and filopodia, of migrating lung fibroblasts. Matrix stiffness-regulated mitochondrial fission and durotactic lung fibroblast migration are mediated by a dynamin-related protein 1/mitochondrial fission factor-dependent (DRP1/MFF-dependent) pathway. Importantly, we found that the DRP1/MFF pathway is activated in fibrotic lung myofibroblasts in both human IPF and bleomycin-induced mouse lung fibrosis. These findings suggest that energy-producing mitochondria need to be sectioned via fission and repositioned in durotactic lung fibroblasts to meet the higher energy demand. This represents a potentially new mechanism through which mitochondria may contribute to the progression of fibrotic lung diseases. Inhibition of durotactic migration of lung fibroblasts may play an important role in preventing the progression of human idiopathic pulmonary fibrosis.

Epigenetic regulation of IPF fibroblast phenotype by glutaminolysis

OBJECTIVE

Excessive extra-cellular-matrix production and uncontrolled proliferation of the fibroblasts are characteristics of many fibrotic diseases, including idiopathic pulmonary fibrosis (IPF). The fibroblasts have enhanced glutaminolysis with up-regulated glutaminase, GLS1, which converts glutamine to glutamate. Here, we investigated the role of glutaminolysis and glutaminolysis-derived metabolite α-ketoglutarate (α-KG) on IPF fibroblast phenotype and gene expression.

METHODS

Reduced glutamine conditions were carried out either using glutamine-free culture medium or silencing the expression of GLS1 with siRNA, with or without α-KG compensation. Cell phenotype has been characterized under these different conditions, and gene expression profile was examined by RNA-Seq. Specific profibrotic genes (Col3A1 and PLK1) expression were examined by real-time PCR and western blots. The levels of repressive histone H3K27me3, which demethylase activity is affected by glutaminolysis, were examined and H3K27me3 association with promoter region of Col3A1 and PLK1 were checked by ChIP assays. Effects of reduced glutaminolysis on fibrosis markers were checked in an animal model of lung fibrosis.

RESULTS

The lack of glutamine in the culture medium alters the profibrotic phenotype of activated fibroblasts. The addition of exogenous and glutaminolysis-derived metabolite α-KG to glutamine-free media barely restores the pro-fibrotic phenotype of activated fibroblasts. Many genes are down-regulated in glutamine-free medium, α-KG supplementation only rescues a limited number of genes. As α-KG is a cofactor for histone demethylases of H3K27me3, the reduced glutaminolysis alters H3K27me3 levels, and enriches H3K27me3 association with Col3A1 and PLK1 promoter region. Adding α-KG in glutamine-free medium depleted H3K27me3 association with Col3A1 promoter region but not that of PLK1. In a murine model of lung fibrosis, mice with reduced glutaminolysis showed markedly reduced fibrotic markers.

CONCLUSIONS

This study indicates that glutamine is critical for supporting pro-fibrotic fibroblast phenotype in lung fibrosis, partially through α-KG-dependent and -independent mechanisms, and supports targeting fibroblast metabolism as a therapeutic method for fibrotic diseases.

FAM111B dysregulation promotes malignancy in fibrosarcoma and POIKTMP and a low-cost method for its mutation screening

INTRODUCTION

Mutations in the uncharacterised human FAM111B gene are associated with POIKTMP, a rare multi-organ fibrosing disease. Recent studies also reported the overexpression of FAM111B in specific cancers. Moreover, FAM111B mutation screening may prove expensive in under-resourced facilities. Therefore, this study investigated its cellular function and dysfunction and described an inexpensive mutation screening method.

MATERIALS AND METHODS

FAM111B expression was assessed in silico and validated in vitro in cell lines and primary skin fibroblasts from a South African POIKTMP-patient with the heterozygous FAM111B gene mutation: NM_198947.4: c.1861T>G (p. Tyr621Asp or Y621D) by qPCR and western blot. The cellular function of FAM111B was studied in HT1080 using various cell-based functional assays, and the Y621D mutation was genotyped by PCR-RFLP.

RESULTS

Expression studies showed upregulated FAM111B mRNA and protein in the cancer cells. High FAM111B expression with robust nuclear localization occurred in HT1080. Additionally, expression data and cell-based assays indicated that FAM111B led to the upregulation of cell migration, decreased cell apoptosis, and modulatory effects on cell proliferation. Y621D mutation showed similar effects on cell migration but minimal impact on cell apoptosis. FAM111B mRNA and protein expression were markedly downregulated (p ≤ 0.05) in the POIKTMP-patient's fibroblasts. The PCR-RFLP method successfully genotyped Y621D gene mutation.

DISCUSSION

FAM111B is a cancer-associated nuclear protein: Its modulation by mutations or overexpression may contribute to the malignancy of cancers and POIKTMP/fibrosis and poor clinical outcomes and represents a viable prognostic marker or therapeutic target. Furthermore, the PCR-RFLP method could prove a valuable tool for FAM111B mutation validation or screening in resource-constrained laboratories.

Caveolin-1 peptide regulates p53-microRNA-34a feedback in fibrotic lung fibroblasts

Idiopathic pulmonary fibrosis (IPF) is a life-threatening disease resulting from dysregulated repair responses to lung injury. Excessive extracellular matrix deposition by expanding myofibroblasts and fibrotic lung fibroblasts (fLfs) has been implicated in the pathogenesis of PF, including IPF. We explored fLfs' microRNA-34a (miR-34a) expression from IPF tissues. Basal miR-34a levels were decreased with reduced binding of p53 to the promoter DNA and 3'UTR mRNA sequences. Overexpression of miR-34a in fLfs increased p53, PAI-1, and reduced pro-fibrogenic markers. The regulatory effects of miR-34a were altered by modifying the p53 expression. Precursor-miR-34a lung transduction reduced bleomycin-induced PF in wild-type mice. fLfs treated with caveolin-1 scaffolding domain peptide (CSP) or its fragment, CSP7, restored miR-34a, p53, and PAI-1. CSP/CSP7 reduced PDGFR-β and pro-fibrogenic markers, which was abolished in fLfs following blockade of miR-34a expression. These peptides failed to resolve PF in mice lacking miR-34a in fLfs, indicating miR-34a-p53-feedback induction required for anti-fibrotic effects.

Arsenic trioxide inhibits the functions of lung fibroblasts derived from patients with idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic and fatal interstitial lung disease. Currently, no treatment can block or reverse the development of lung fibrosis in patients suffering from IPF. Recent studies indicate that arsenic trioxide (ATO), a safe, effective anti-cancer pro-oxidant drug, prevents the differentiation of normal human lung fibroblasts (NHLFs) in vitro and reduces experimental pulmonary fibrosis in vivo. In this context, we investigated the anti-fibrotic effects of ATO on the main fibrosis functions of human lung fibroblasts (HLFs) isolated from patients with IPF. IPF and non-IPF (control) HLFs were incubated with 0.01-1 μM ATO and stimulated with pro-fibrotic factors (PDGF-BB or TGF-β1). We measured their rates of proliferation, migration and differentiation and the cell stress response triggered by ATO. ATO did not affect cell viability but strongly inhibited the proliferation and migration of PDGF-BB-stimulated IPF and control HLFs. ATO also prevented myofibroblastic differentiation, as assessed by the expression of α-smooth muscle actin (α-SMA) and collagen-1, and the phosphorylation of SMAD2/3 in TGF-β1-stimulated HLFs. These antifibrotic effects were associated with increased expression of the transcription factor NRF2 and its target genes NQO1 and HMOX1. Genetic silencing of NRF2 inhibited the ATO-induced cell stress response but did not prevent the ATO-dependent inhibition of α-SMA expression in TGF-β1-stimulated HLFs. The results demonstrate that ATO, at concentrations similar to exposure in blood plasma of ATO-treated cancer patients, counteracted pro-fibrotic activities of HLFs from IPF patients. We propose to consider ATO for clinical exploration to define the therapeutic potential in patients with IPF.

Transient Agarose Spot (TAS) Assay: A New Method to Investigate Cell Migration

Fibroblasts play a central role in diseases associated with excessive deposition of extracellular matrix (ECM), including idiopathic pulmonary fibrosis. Investigation of different properties of fibroblasts, such as migration, proliferation, and collagen-rich ECM production is unavoidable both in basic research and in the development of antifibrotic drugs. In the present study we developed a cost-effective, 96-well plate-based method to examine the migration of fibroblasts, as an alternative approach to the gold standard scratch assay, which has numerous limitations. This article presents a detailed description of our transient agarose spot (TAS) assay, with instructions for its routine application. Advantages of combined use of different functional assays for fibroblast activation in drug development are also discussed by examining the effect of nintedanib—an FDA approved drug against IPF—on lung fibroblasts.

Pathologic Proteolytic Processing of N-Cadherin as a Marker of Human Fibrotic Disease

Prior research has implicated the involvement of cell adhesion molecule N-cadherin in tissue fibrosis and remodeling. We hypothesize that anomalies in N-cadherin protein processing are involved in pathological fibrosis. Diseased tissues associated with fibrosis of the heart, lung, and liver were probed for the precursor form of N-cadherin, pro-N-cadherin (PNC), by immunohistochemistry and compared to healthy tissues. Myofibroblast cell lines were analyzed for cell surface pro-N-cadherin by flow cytometry and immunofluorescent microscopy. Soluble PNC products were immunoprecipitated from patient plasmas and an enzyme-linked immunoassay was developed for quantification. All fibrotic tissues examined show aberrant PNC localization. Cell surface PNC is expressed in myofibroblast cell lines isolated from cardiomyopathy and idiopathic pulmonary fibrosis but not on myofibroblasts isolated from healthy tissues. PNC is elevated in the plasma of patients with cardiomyopathy (p ≤ 0.0001), idiopathic pulmonary fibrosis (p ≤ 0.05), and nonalcoholic fatty liver disease with cirrhosis (p ≤ 0.05). Finally, we have humanized a murine antibody and demonstrate that it significantly inhibits migration of PNC expressing myofibroblasts. Collectively, the aberrant localization of PNC is observed in all fibrotic tissues examined in our study and our data suggest a role for cell surface PNC in the pathogenesis of fibrosis.

Bidirectional epithelial-mesenchymal crosstalk provides self-sustaining profibrotic signals in pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is the prototypic progressive fibrotic lung disease with a median survival of 2 to 4 years. Injury to and/or dysfunction of the alveolar epithelium is strongly implicated in IPF disease initiation, but the factors that determine whether fibrosis progresses rather than normal tissue repair occurs remain poorly understood. We previously demonstrated that zinc finger E-box-binding homeobox 1-mediated epithelial-mesenchymal transition in human alveolar epithelial type II (ATII) cells augments transforming growth factor-β-induced profibrogenic responses in underlying lung fibroblasts via paracrine signaling. Here, we investigated bidirectional epithelial-mesenchymal crosstalk and its potential to drive fibrosis progression. RNA-Seq of lung fibroblasts exposed to conditioned media from ATII cells undergoing RAS-induced epithelial-mesenchymal transition identified many differentially expressed genes including those involved in cell migration and extracellular matrix regulation. We confirmed that paracrine signaling between RAS-activated ATII cells and fibroblasts augmented fibroblast recruitment and demonstrated that this involved a zinc finger E-box-binding homeobox 1-tissue plasminogen activator axis. In a reciprocal fashion, paracrine signaling from transforming growth factor-β-activated lung fibroblasts or IPF fibroblasts induced RAS activation in ATII cells, at least partially through the secreted protein acidic and rich in cysteine, which may signal via the epithelial growth factor receptor via epithelial growth factor-like repeats. Together, these data identify that aberrant bidirectional epithelial-mesenchymal crosstalk in IPF drives a chronic feedback loop that maintains a wound-healing phenotype and provides self-sustaining profibrotic signals.

Osteopontin enhances the migration of lung fibroblasts via upregulation of interleukin-6 through the extracellular signal-regulated kinase (ERK) pathway

Fibrosis is a phenomenon in which parenchyma is replaced with fibrous tissue. Persistent inflammation accompanied by dysregulation of cytokine production and repeated cycles of inflammation-associated tissue-repair induces fibrosis in various organs including the liver, lung, and kidney. In idiopathic pulmonary fibrosis, production of interleukin (IL)-6 and osteopontin (OPN) are dysregulated. Fibrosis leads to qualitative rather than quantitative changes of fibroblasts at the sites of tissue repair, and this leads to enlargement of fibrotic foci. These fibroblasts are immunohistochemically positive for OPN; however, the effect of overexpressed OPN in fibroblasts is not fully understood yet. In this study, we investigated the effect of OPN on IL-6 secretion and on migration and proliferation of fibroblasts. Lung fibroblasts overexpressing exogenous OPN showed that OPN was linked to the enhancement of cell migration through increased IL-6 secretion via the extracellular signal-regulated kinase (ERK) pathway. These results suggest that OPN may exert its pro-fibrotic functions, such as enhancement of fibroblasts migration by cooperating with chemoattractant IL-6, and may be involved in enlargement of fibrotic foci.

Interleukin-11 signaling underlies fibrosis, parenchymal dysfunction, and chronic inflammation of the airway

Interleukin (IL)-11 evolved as part of the innate immune response. In the human lung, IL-11 upregulation has been associated with viral infections and a range of fibroinflammatory diseases, including idiopathic pulmonary fibrosis. Transforming growth factor-beta (TGFβ) and other disease factors can initiate an autocrine loop of IL-11 signaling in pulmonary fibroblasts, which, in a largely ERK-dependent manner, triggers the translation of profibrotic proteins. Lung epithelial cells also express the IL-11 receptor and transition into a mesenchymal-like state in response to IL-11 exposure. In mice, therapeutic targeting of IL-11 with antibodies can arrest and reverse bleomycin-induced pulmonary fibrosis and inflammation. Intriguingly, fibroblast-specific blockade of IL-11 signaling has anti-inflammatory effects, which suggests that lung inflammation is sustained, in part, through IL-11 activity in the stroma. Proinflammatory fibroblasts and their interaction with the damaged epithelium may represent an important but overlooked driver of lung disease. Initially thought of as a protective cytokine, IL-11 is now increasingly recognized as an important determinant of lung fibrosis, inflammation, and epithelial dysfunction.

Genome-Wide Association Study: Functional Variant rs2076295 Regulates Desmoplakin Expression in Airway Epithelial Cells

Rationale: Genetic association studies have identified rs2076295 in association with idiopathic pulmonary fibrosis (IPF). We hypothesized that rs2076295 is the functional variant regulating DSP (desmoplakin) expression in human bronchial epithelial cells, and DSP regulates extracellular matrix-related gene expression and cell migration, which is relevant to IPF development.Objectives: To determine whether rs2076295 regulates DSP expression and the function of DSP in airway epithelial cells.Methods: Using CRISPR (clustered regularly interspaced short palindromic repeat)/Cas9 editing (including regional deletion, indel, CRISPR interference, and single-base editing), we modified rs2076295 and measured DSP expression in edited 16HBE14o- and primary airway epithelial cells. Cellular integrity, migration, and genome-wide gene expression changes were examined in 16HBE14o- single colonies with DSP knockout. The expression of DSP and its relevant matrix genes was measured by quantitative PCR and also analyzed in single-cell RNA-sequencing data from control and IPF lungs.Measurements and Main Results:DSP is expressed predominantly in bronchial and alveolar epithelial cells, with reduced expression in alveolar epithelial cells in IPF lungs. The deletion of the DNA region-spanning rs2076295 led to reduced expression of DSP, and the edited rs2076295GG 16HBE14o- line has lower expression of DSP than the rs2076295TT lines. Knockout of DSP in 16HBE14o- cells decreased transepithelial resistance but increased cell migration, with increased expression of extracellular matrix-related genes, including MMP7 and MMP9. Silencing of MMP7 and MMP9 abolished increased migration in DSP-knockout cells.Conclusions: rs2076295 regulates DSP expression in human airway epithelial cells. The loss of DSP enhances extracellular matrix-related gene expression and promotes cell migration, which may contribute to the pathogenesis of IPF.

Analysis of fibroblast migration dynamics in idiopathic pulmonary fibrosis using image-based scaffolds of the lung extracellular matrix

Idiopathic pulmonary fibrosis (IPF) is characterized by a profound remodeling of the collagen in the extracellular matrix (ECM), where the fibers become both denser and more highly aligned. However, it is unknown how this reconfiguration of the collagen matrix affects disease progression. Here, we investigate the role of specific alterations in collagen fiber organization on cell migration dynamics by using biomimetic image-based collagen scaffolds representing normal and fibrotic lung, where the designs are derived directly from high-resolution second harmonic generation microscopy images. The scaffolds are fabricated by multiphoton-excited (MPE) polymerization, where the process is akin to three-dimensional printing, except that it is performed at much greater resolution (∼0.5 microns) and with collagen and collagen analogs. These scaffolds were seeded with early passaged primary human normal and IPF fibroblasts to enable the decoupling of the effect of cell-intrinsic characteristics (normal vs. IPF) versus ECM structure (normal vs. IPF) on migration dynamics. We found that the highly aligned IPF collagen structure promoted enhanced cell elongation and F-actin alignment along with increased cell migration speed and straightness relative to the normal tissues. Collectively, the data are consistent with an enhanced contact guidance mechanism on the aligned IPF matrix. Although cell intrinsic effects were observed, the aligned collagen matrix morphology had a larger effect on these metrics. Importantly, these biomimetic models of the lung cannot be synthesized by conventional fabrication methods. We suggest that the MPE image-based fabrication method will enable additional hypothesis-based testing studies of cell-matrix interactions in the context of tissue fibrosis.

Regulatory network of two circRNAs and an miRNA with their targeted genes under astilbin treatment in pulmonary fibrosis

Circular RNAs (circRNAs) are becoming new therapeutic drug targets. However, their profiles under astilbin treatment have not been reported yet. In this study, we analysed the global reprogramming of circRNA transcriptome and a regulatory network of circRNAs with their targeted genes under astilbin treatment in pulmonary fibrosis. A total of 145 circRNAs were differentially expressed in the astilbin-treated group compared with the bleomycin-treated group using RNA sequencing. In the bleomycin- and astilbin-treated groups, 29 coexpressed circRNAs were found. The maximum number of circRNAs was distributed on chromosome two, and their length varieties were mainly within 1000 bp. Four differentially expressed circRNAs (circRNA-662, 949, 394 and 986) were tested to validate the RNA sequencing data, and their targeted microRNAs and genes were analysed by qRT-PCR, Western blot, Pearson correlation coefficient, a dual-luciferase reporter system and anti-AGO2 RNA immunoprecipitation. The results showed that circRNA-662 and 949 can act as "miR-29b sponges" targeting Gli2 and STAT3 to exert their functions. Our work suggests that the transcriptome complexity at the circRNA level under astilbin treatment. These circRNAs may be potential molecular targets for drug action.

Endogenous viable cells in lyopreserved amnion retain differentiation potential and anti-fibrotic activity in vitro

Human amniotic membrane (AM) has intrinsic anti-inflammatory, anti-fibrotic and antimicrobial properties. Tissue preservation methods have helped to overcome the short shelf life of fresh AM allowing "on demand" use of AM grafts. Cryopreserved AM that retains all native tissue components, including viable cells, has clinical benefits in treating chronic wounds. However, cryopreservation requires ultra-low temperature storage, limiting the use of cryopreserved products. To overcome this limitation, a new lyopreservation method has been developed for ambient storage of living tissues. The goal of this study was to investigate the viability and functionality of AM cells following lyopreservation. Fresh AM and devitalized lyopreserved AM (DLAM) served as positive and negative controls, respectively. Using live/dead staining, we confirmed the presence of living cells in viable lyopreserved AM (VLAM) and showed that these cells persisted up to 21 days in culture medium. The functionality of cells in VLAM was assessed by their differentiation potential and anti-fibrotic activity in vitro. With osteogenic induction, cells in VLAM deposited calcium within the membrane, a marker of osteogenic cells, in a time-dependent manner. The migration of human lung fibrotic fibroblasts in a scratch wound assay was reduced significantly in the presence of VLAM-derived conditioned medium. Quantitative PCR analyses indicated that VLAM reduced the expression of pro-fibrotic factors such as type I collagen and increased the expression of anti-fibrotic factors such as hepatocyte growth factor and anti-fibrotic microRNA in fibrotic fibroblasts. Taken together, these results demonstrate that endogenous cells in VLAM remain viable and functional post-lyophilization. STATEMENT OF SIGNIFICANCE: This study, for the first time, provides direct evidence showing that tissue viability and functional cells can be preserved by lyophilization. Similar to fresh amniotic membrane (AM), viable lyopreserved AM (VLAM) retains viable cells for extended periods of time. More importantly, these cells are functional and maintain their osteogenic differentiation potential and anti-fibrotic activity. Our results confirmed that the novel lyophilization method preserves tissue viability.

S100A12 inhibits fibroblast migration via the receptor for advanced glycation end products and p38 MAPK signaling

The migration of lung fibroblasts plays a pivotal role in wound repair and fibrotic processes in the lung. Although the receptor for advanced glycation end products (RAGE) has been implicated in the pathogenesis of lung diseases, its role in lung fibroblast migration is unclear. The current study examined the effect of three different RAGE ligands, namely, high mobility group box 1 (HMGB1), S100A12, and N-epsilon-(carboxymethyl) lysine (CML), on human fibronectin-directed human fetal lung fibroblast (HFL-1) migration. HMGB1 augmented, whereas S100A12 inhibited, HFL-1 migration in a concentration-dependent manner. CML did not affect HFL-1 migration. The effect of HMGB1 was not through RAGE. However, the effect of S100A12 was mediated by RAGE, but not Toll-like receptor 4. S100A12 did not exert a chemoattractant effect, but inhibited HFL-1 chemotaxis and/or chemokinesis. Moreover, S100A12 mediated HFL-1 migration through p38 mitogen-activated protein kinase (MAPK) but not through nuclear factor-kappa B, protein kinase A, phosphatase and tensin homolog deleted on chromosome 10, or cyclooxygenase. In addition, western blot analysis showed that S100A12 augmented p38 MAPK activity in the presence of human fibronectin. In conclusion, S100A12 inhibits lung fibroblast migration via RAGE-p38 MAPK signaling. This pathway could represent a therapeutic target for pulmonary conditions characterized by abnormal tissue repair and remodeling.

Vimentin intermediate filament assembly regulates fibroblast invasion in fibrogenic lung injury

Idiopathic pulmonary fibrosis (IPF) is a progressive disease, with a median survival of 3-5 years following diagnosis. Lung remodeling by invasive fibroblasts is a hallmark of IPF. In this study, we demonstrate that inhibition of vimentin intermediate filaments (VimIFs) decreases the invasiveness of IPF fibroblasts and confers protection against fibrosis in a murine model of experimental lung injury. Increased expression and organization of VimIFs contribute to the invasive property of IPF fibroblasts in connection with deficient cellular autophagy. Blocking VimIF assembly by pharmacologic and genetic means also increases autophagic clearance of collagen type I. Furthermore, inhibition of expression of collagen type I by siRNA decreased invasiveness of fibroblasts. In a bleomycin injury model, enhancing autophagy in fibroblasts by an inhibitor of VimIF assembly, withaferin A (WFA), protected from fibrotic lung injury. Additionally, in 3D lung organoids, or pulmospheres, from patients with IPF, WFA reduced the invasiveness of lung fibroblasts in the majority of subjects tested. These studies provide insights into the functional role of vimentin, which regulates autophagy and restricts the invasiveness of lung fibroblasts.

The controversial role of mast cells in fibrosis

Fibrosis is a medical condition characterized by an excessive deposition of extracellular matrix compounds such as collagen in tissues. Fibrotic lesions are present in many diseases and can affect all organs. The excessive extracellular matrix accumulation in these conditions can often have serious consequences and in many cases be life-threatening. A typical event seen in many fibrotic conditions is a profound accumulation of mast cells (MCs), suggesting that these cells can contribute to the pathology. Indeed, there is now substantialv evidence pointing to an important role of MCs in fibrotic disease. However, investigations from various clinical settings and different animal models have arrived at partly contradictory conclusions as to how MCs affect fibrosis, with many studies suggesting a detrimental role of MCs whereas others suggest that MCs can be protective. Here, we review the current knowledge of how MCs can affect fibrosis.

Niclosamide alleviates pulmonary fibrosis in vitro and in vivo by attenuation of epithelial-to-mesenchymal transition, matrix proteins & Wnt/β-catenin signaling: A drug repurposing study

Drug repurposing off late has been emerging as an inspiring alternative approach to conventional, exhaustive and arduous process of drug discovery. It is a process of identifying new therapeutic values for a drug already established for the treatment of a certain condition. Our current study is aimed at repurposing the old anti-helimenthic drug Niclosamide as an anti-fibrotic drug against pulmonary fibrosis (PF). PF is most common lethal interstitial lung disease hallmarked by deposition of extracelluar matrix and scarring of lung. Heterogenous nature, untimely diagnosis and lack of appropriate treatment options make PF an inexorable lung disorder. Prevailing void in PF treatment and drug repositioning strategy of drugs kindled our interest to demonstrate the anti-fibrotic activity of Niclosamide. Our study is aimed at investigating the anti-fibrotic potential of Niclosamide in TGF-β1 induced in vitro model of PF and 21-day model of Bleomycin induced PF in vivo respectively. Our study results showed that Niclosamide holds the potential to exert anti-fibrotic effect by hampering fibroblast migration, attenuating EMT, inhibiting fibrotic signaling and by regulating WNT/β-catenin signaling as evident from protein expression studies. Our study findings can give new directions to development of Niclosamide as an anti-fibrotic agent for treatment of pulmonary fibrosis.

Airway remodeling disease: primary human structural cells and phenotypic and pathway assays to identify targets with potential to prevent or reverse remodeling

Airway remodeling is a characteristic of many chronic respiratory diseases and occurs when there are significant changes to the architecture of the small and large airways leading to progressive loss of lung function. Some common features include airway smooth muscle and goblet cell hyperplasia, basement membrane thickening and subepithelial fibrosis. To explore the mechanisms driving airway remodeling and identify novel targets to treat this aspect of respiratory disease, appropriate models must be used that will accurately predict the pathology of disease. Phenotypic assays can be used in primary human lung cells to measure changes in cell behavior that are associated with particular disease pathology. This is becoming increasingly popular when targeting chronic pathologies such as airway remodeling, where phenotypic assays are likely to model disease in vitro more accurately than traditional second messenger assays. Here we review the use of primary human lung structural cells in a range of disease-relevant chronic phenotypic assays, and how they may be used in target identification/validation and drug discovery.

Inhibition of chlorine-induced airway fibrosis by budesonide

Chlorine is a chemical threat agent that can be harmful to humans. Acute inhalation of high levels of chlorine results in the death of airway epithelial cells and can lead to persistent adverse effects on respiratory health, including airway remodeling and hyperreactivity. We previously developed a mouse chlorine exposure model in which animals developed inflammation and fibrosis in large airways. In the present study, examination by laser capture microdissection of developing fibroproliferative lesions in FVB/NJ mice exposed to 240 ppm-h chlorine revealed upregulation of genes related to macrophage function. Treatment of chlorine-exposed mice with the corticosteroid drug budesonide daily for 7 days (30-90 μg/mouse i.m.) starting 1 h after exposure prevented the influx of M2 macrophages and the development of airway fibrosis and hyperreactivity. In chlorine-exposed, budesonide-treated mice 7 days after exposure, large airways lacking fibrosis contained extensive denuded areas indicative of a poorly repaired epithelium. Damaged or poorly repaired epithelium has been considered a trigger for fibrogenesis, but the results of this study suggest that inflammation is the ultimate driver of fibrosis in our model. Examination at later times following 7-day budesonide treatment showed continued absence of fibrosis after cessation of treatment and regrowth of a poorly differentiated airway epithelium by 14 days after exposure. Delay in the start of budesonide treatment for up to 2 days still resulted in inhibition of airway fibrosis. Our results show the therapeutic potential of budesonide as a countermeasure for inhibiting persistent effects of chlorine inhalation and shed light on mechanisms underlying the initial development of fibrosis following airway injury.

Inhibition of Raf1 ameliorates bleomycin-induced pulmonary fibrosis through attenuation of TGF-β1 signaling

Idiopathic pulmonary fibrosis (IPF) is a fatal fibrotic lung disease associated with aberrant activation and differentiation of fibroblasts, leading to abnormal extracellular matrix production. Currently, it is still an untreatable disease (except for lung transplantation). Here, we demonstrate that the Raf1 inhibitor GW5074 ameliorates lung fibrosis in bleomycin-induced pulmonary fibrosis. Posttreatment with GW5074 reduced fibronectin (FN) expression, collagen deposition, and inflammatory cell infiltration in bleomycin-challenged mice, suggesting an antifibrotic property of GW5074. To determine the molecular mechanisms by which inhibition of Raf1 ameliorates lung fibrosis, we investigated the role of Raf1 in TGF-β1 signaling in human lung fibroblasts. GW5074 or downregulation of Raf1 by siRNAs significantly attenuated TGF-β1-induced smooth muscle actin, FN, and collagen I expression, whereas overexpression of Raf1 promoted the effects of TGF-β1 in lung fibroblasts. Furthermore, we found that Raf1-promoted TGF-β1 signaling was through the Raf1/ERK/Smad pathway and contributed to the cell proliferation and migration in human lung fibroblasts. This study provides preclinical and mechanistic evidence for development of Raf1 inhibitors as potential antifibrotic drugs for the treatment of IPF.

SIRT-1 regulates TGF-β-induced dermal fibroblast migration via modulation of Cyr61 expression

SIRT1 is a NAD-dependent protein deacetylase that participates in cellular regulation. The increased migration of fibroblasts is an important phenotype in fibroblast activation. The role of SIRT1 in cell migration remains controversial as to whether SIRT1 acts as an activator or suppressor of cell migration. Therefore, we have established the role of SIRT1 in the migration of human dermal fibroblasts and explored targets of SIRT1 during dermal fibroblast migration. SIRT1 and Cyr61 were expressed in human dermal fibroblasts and the stimulation with TGF-β further induced their expression. Treatment with resveratrol (RSV), a SIRT1 agonist, or overexpression of SIRT1 also promoted the expression Cyr61 in human dermal fibroblasts, whereas the inhibition of SIRT1 activity by nicotinamide or knockdown of SIRT1 decreased the level of Cyr61, as well as TGF-β or RSV-induced Cyr61 expression. Blocking of ERK signaling by PD98509 reduced the expression of Cyr61 induced by TGF-β or RSV. TGF-β, RSV, or SIRT1 overexpression enhanced β-catenin as well as Cyr61 expression. This stimulation was reduced by the Wnt inhibitor XAV939. RSV increased migration and nicotinamide attenuated RSV-induced migration of human dermal fibroblasts. Furthermore, SIRT1 overexpression promoted cell migration, whereas blocking Cyr61 attenuated SIRT1-stimulated migration of human dermal fibroblasts. SIRT1 increased cell migration by stimulating Cyr61 expression and the ERK and Wnt/β-catenin signaling. SIRT1-induced Cyr61 activity is very important for human dermal fibroblasts migration.

FK506-binding protein 10 (FKBP10) regulates lung fibroblast migration via collagen VI synthesis

Background

In idiopathic pulmonary fibrosis (IPF), fibroblasts gain a more migratory phenotype and excessively secrete extracellular matrix (ECM), ultimately leading to alveolar scarring and progressive dyspnea. Here, we analyzed the effects of deficiency of FK506-binding protein 10 (FKBP10), a potential IPF drug target, on primary human lung fibroblast (phLF) adhesion and migration.

Methods

Using siRNA, FKBP10 expression was inhibited in phLF in absence or presence of 2ng/ml transforming growth factor-β1 (TGF-β1) and 0.1mM 2-phosphoascorbate. Effects on cell adhesion and migration were monitored by an immunofluorescence (IF)-based attachment assay, a conventional scratch assay, and single cell tracking by time-lapse microscopy. Effects on expression of key players in adhesion dynamics and migration were analyzed by qPCR and Western Blot. Colocalization was evaluated by IF microscopy and by proximity ligation assays.

Results

FKBP10 knockdown significantly attenuated adhesion and migration of phLF. Expression of collagen VI was decreased, while expression of key components of the focal adhesion complex was mostly upregulated. The effects on migration were 2-phosphoascorbate-dependent, suggesting collagen synthesis as the underlying mechanism. FKBP10 colocalized with collagen VI and coating culture dishes with collagen VI, and to a lesser extent with collagen I, abolished the effect of FKBP10 deficiency on migration.

Conclusions

These findings show, to our knowledge for the first time, that FKBP10 interacts with collagen VI and that deficiency of FKBP10 reduces phLF migration mainly by downregulation of collagen VI synthesis. The results strengthen FKBP10 as an important intracellular regulator of ECM remodeling and support the concept of FKBP10 as drug target in IPF.

Epithelial-mesenchymal crosstalk influences cellular behavior in a 3D alveolus-fibroblast model system

Interactions between lung epithelium and interstitial fibroblasts are increasingly recognized as playing a major role in the progression of several lung pathologies, including cancer. Three-dimensional in vitro co-culture systems offer tissue-relevant platforms to study the signaling interplay between diseased and healthy cell types. Such systems provide a controlled environment in which to probe the mechanisms involved in epithelial-mesenchymal crosstalk. To recapitulate the native alveolar tissue architecture, we employed a cyst templating technique to culture alveolar epithelial cells on photodegradable microspheres and subsequently encapsulated the cell-laden spheres within poly (ethylene glycol) (PEG) hydrogels containing dispersed pulmonary fibroblasts. A fibroblast cell line (CCL-210) was co-cultured with either healthy mouse alveolar epithelial primary cells or a cancerous alveolar epithelial cell line (A549) to probe the influence of tumor-stromal interactions on proliferation, migration, and matrix remodeling. In 3D co-culture, cancerous epithelial cells and fibroblasts had higher proliferation rates. When examining fibroblast motility, the fibroblasts migrated faster when co-cultured with cancerous A549 cells. Finally, a fluorescent peptide reporter for matrix metalloproteinase (MMP) activity revealed increased MMP activity when A549s and fibroblasts were co-cultured. When MMP activity was inhibited or when cells were cultured in gels with a non-degradable crosslinker, fibroblast migration was dramatically suppressed, and the increase in cancer cell proliferation in co-culture was abrogated. Together, this evidence supports the idea that there is an exchange between the alveolar epithelium and surrounding fibroblasts during cancer progression that depends on MMP activity and points to potential signaling routes that merit further investigation to determine targets for cancer treatment.

Unique and Redundant Functions of p70 Ribosomal S6 Kinase Isoforms Regulate Mesenchymal Cell Proliferation and Migration in Pulmonary Fibrosis

The p70 ribosomal S6 kinase (p70S6K) is a downstream substrate that is phosphorylated and activated by the mammalian target of rapamycin complex and regulates multiple cellular processes associated with pulmonary fibrogenesis. Two isoforms of the p70S6K have been identified (S6K1 and S6K2), but their relative contributions in mediating pulmonary fibrosis are unknown. To interrogate the roles of the p70S6K isoforms, we overexpressed transforming growth factor (TGF)-α in mice deficient for the S6K1 or S6K2 genes and measured changes in lung histology, morphometry, total lung collagen, lung function, and proliferation between wild-type and isoform-deficient mice. Deficiency of S6K1, but not S6K2, had a significant effect on reducing proliferation in subpleural fibrotic lesions during TGF-α-induced fibrosis. Migration was significantly decreased in mesenchymal cells isolated from the lungs of S6K1 knockout mice compared with wild-type or S6K2 knockout mice. Conversely, increases in subpleural thickening were significantly decreased in S6K2-deficient mice compared with wild type. Deficiency of S6K2 significantly reduced phosphorylation of the downstream S6 ribosomal protein in lung homogenates and isolated mesenchymal cells after TGF-α expression. However, deficiency of neither isoform alone significantly altered TGF-α-induced collagen accumulation or lung function decline in vivo. Furthermore, deficiency in neither isoform prevented changes in collagen accumulation or lung compliance decline after administration of intradermal bleomycin. Together, these findings demonstrate that the p70S6K isoforms have unique and redundant functions in mediating fibrogenic processes, including proliferation, migration, and S6 phosphorylation, signifying that both isoforms must be targeted to modulate p70S6K-mediated pulmonary fibrosis.

Heterogeneity of Fibroblasts and Myofibroblasts in Pulmonary Fibrosis

PURPOSE OF REVIEW

Idiopathic Pulmonary Fibrosis (IPF) is the most common form of interstitial lung diseases of unknown eathiopathogenesis, mean survival of 3-5 years and limited therapeutics. Characterized by a loss of alveolar type II epithelial cells and aberrant activation of stromal cells, considerable effort was undertaken to characterize the origin and activation mechanisms of fibroblasts and myofibroblasts in IPF lungs. In this review, the origin and contribution of fibroblast and myofibroblasts in lung fibrosis will be summarized.

RECENT FINDINGS

Lineage tracing experiments suggested that interstitial lung fibroblasts and lipofibroblasts, pericytes and mesothelial cells differentiate into myofibroblasts. However, epithelial and bone marrow derived cells may give rise to collagen expressing fibroblasts but do not differentiate into myofibroblasts.

SUMMARY

There is great heterogeneity in fibroblasts and myofibroblasts in fibrotic lungs. Further, there is evidence for the expansion of pericyte derived myofibroblasts and loss of lipofibroblasts and lipofibroblast derived myofibroblasts in IPF.

Matrix stiffness regulates migration of human lung fibroblasts

In patients with pulmonary diseases such as idiopathic pulmonary fibrosis and severe acute respiratory distress syndrome, progressive pulmonary fibrosis is caused by dysregulated wound healing via activation of fibroblasts after lung inflammation or severe damage. Migration of fibroblasts toward the fibrotic lesions plays an important role in pulmonary fibrosis. Fibrotic tissue in the lung is much stiffer than normal lung tissue. Emerging evidence supports the hypothesis that the stiffness of the matrix is not only a consequence of fibrosis, but also can induce fibroblast activation. Nevertheless, the effects of substrate rigidity on migration of lung fibroblasts have not been fully elucidated. We evaluated the effects of substrate stiffness on the morphology, α-smooth muscle actin (α-SMA) expression, and cell migration of primary human lung fibroblasts by using polyacrylamide hydrogels with stiffnesses ranging from 1 to 50 kPa. Cell motility was assessed by platelet-derived growth factor (PDGF)-induced chemotaxis and random walk migration assays. As the stiffness of substrates increased, fibroblasts became spindle-shaped and spread. Expression of α-SMA proteins was higher on the stiffer substrates (25 kPa gel and plastic dishes) than on the soft 2 kPa gel. Both PDGF-induced chemotaxis and random walk migration of fibroblasts precultured on stiff substrates (25 kPa gel and plastic dishes) were significantly higher than those of cells precultured on 2 kPa gel. Transfection of the fibroblasts with short interfering RNA for α-SMA inhibited cell migration. These findings suggest that fibroblast activation induced by a stiff matrix is involved in mechanisms of the pathophysiology of pulmonary fibrosis.

Interaction of Src and Alpha-V Integrin Regulates Fibroblast Migration and Modulates Lung Fibrosis in A Preclinical Model of Lung Fibrosis

Src kinase is known to regulate fibroblast migration. However, the contribution of integrin and Src kinase interaction to lung fibrosis has not been mechanistically investigated. Our data demonstrate that integrin alpha v (αV) recruited Src kinase and that leads to subsequent Src activation in fibroblasts plated on fibrotic matrix, osteopontin. Src interaction with integrin αV is required for integrin αV-mediated Src activation, and the subsequent fibroblast migration. The study identified that β5 and β3 are the major integrins for this effect on osteopontin. In contrast, integrins β1, β6, and β8 did not have a critical role in this phenomenon. Importantly, Src inhibitor significantly reduces fibroblast migration stimulated by PDGF-BB and reduced in vivo lung fibrosis in mice. Src inhibitor reduced Src activation and blocked the signaling transduction by integrin αV, inhibited migration signaling pathways and reduced extracellular matrix protein production, and blocked myofibroblast differentiation in vivo in mouse lung tissues. The present study supports that the interaction of Src Kinase and integrins plays a critical role in the development of lung fibrosis and the signaling involved may present a novel opportunity to target deadly fibrotic diseases.

Matrix-driven Myosin II Mediates the Pro-fibrotic Fibroblast Phenotype

Pro-fibrotic mesenchymal cells are known to be the key effector cells of fibroproliferative disease, but the specific matrix signals and the induced cellular responses that drive the fibrogenic phenotype remain to be elucidated. The key mediators of the fibroblast fibrogenic phenotype were characterized using a novel assay system that measures fibroblast behavior in response to actual normal and fibrotic lung tissue. Using this system, we demonstrate that normal lung promotes fibroblast motility and polarization, while fibrotic lung immobilizes the fibroblast and promotes myofibroblast differentiation. These context-specific phenotypes are surprisingly both mediated by myosin II. The role of myosin II is supported by the observation of an increase in myosin phosphorylation and a change in intracellular distribution in fibroblasts on fibrotic lung, as compared with normal lung. Moreover, loss of myosin II activity has opposing effects on protrusive activity in fibroblasts on normal and fibrotic lung. Loss of myosin II also selectively inhibits myofibroblast differentiation in fibroblasts on fibrotic lung. Importantly, these findings are recapitulated by varying the matrix stiffness of polyacrylamide gels in the range of normal and fibrotic lung tissue. Comparison of the effects of myosin inhibition on lung tissue with that of polyacrylamide gels suggests that matrix fiber organization drives the fibroblast phenotype under conditions of normal/soft lung, while matrix stiffness drives the phenotype under conditions of fibrotic/stiff lung. This work defines novel roles for myosin II as a key regulatory effector molecule of the pro-fibrotic phenotype, in response to biophysical properties of the matrix.

Focal Adhesion Kinase Regulates Fibroblast Migration via Integrin beta-1 and Plays a Central Role in Fibrosis

Lung fibrosis is a major medical problem for the aging population worldwide. Fibroblast migration plays an important role in fibrosis. Focal Adhesion Kinase (FAK) senses the extracellular stimuli and initiates signaling cascades that promote cell migration. This study first examined the dose and time responses of FAK activation in human lung fibroblasts treated with platelet derived growth factor BB (PDGF-BB). The data indicate that FAK is directly recruited by integrin β1 and the subsequent FAK activation is required for fibroblast migration on fibronectin. In addition, the study has identified that α5β1 and α4β1 are the major integrins for FAK-mediated fibroblast migration on fibronect. In contrast, integrins αvβ3, αvβ6, and αvβ8 play a minor but distinct role in fibroblast migration on fibronectin. FAK inhibitor significantly reduces PDGF-BB stimulated fibroblast migration. Importantly, FAK inhibitor protects bleomycin-induced lung fibrosis in mice. FAK inhibitor blocks FAK activation and significantly reduces signaling cascade of fibroblast migration in bleomycin-challenged mice. Furthermore, FAK inhibitor decreases lung fibrotic score, collagen accumulation, fibronectin production, and myofibroblast differentiation in in bleomycin-challenged mice. These data demonstrate that FAK mediates fibroblast migration mainly via integrin β1. Furthermore, the findings suggest that targeting FAK signaling is an effective therapeutic strategy against fibrosis.

Down-regulation of USP13 mediates phenotype transformation of fibroblasts in idiopathic pulmonary fibrosis

Background

Idiopathic pulmonary fibrosis (IPF) is a fatal disease characterized by fibroblastic foci and progressive scarring of the pulmonary parenchyma. IPF fibroblasts display increased proliferation and enhanced migration and invasion, analogous to cancer cells. This transformation-like phenotype of fibroblasts plays an important role in the development of pulmonary fibrosis, but the mechanism for this is not well understood.

Methods

In this study, we compared gene expression profiles in fibrotic lung tissues from IPF patients and normal lung tissues from patients with primary spontaneous pneumothorax using a cDNA microarray to examine the mechanisms involved in the pathogenesis of IPF. In a cDNA microarray, we found that USP13 was decreased in lung tissues from patients with IPF, which was further confirmed by results from immunohistochemistry and western blot assays. Then, we used RNA interference in MRC-5 cells to inhibit USP13 and evaluated its effects by western blot, real-time RT-PCR, bromodeoxyuridine incorporation, and transwell assays. We also used co-immunoprecipitation and immunofluorescence staining to identify the correlation between USP13 and PTEN in IPF.

Results

USP13 expression levels were markedly reduced in fibroblastic foci and primary IPF fibroblast lines. The depletion of USP13 resulted in the transformation of fibroblasts into an aggressive phenotype with enhanced proliferative, migratory, and invasive capacities. Additionally, USP13 interacted with PTEN and mediated PTEN ubiquitination and degradation in lung fibroblasts.

Conclusions

Down-regulation of USP13 mediates PTEN protein loss and fibroblast phenotypic change, and thereby plays a crucial role in IPF pathogenesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-015-0286-3) contains supplementary material, which is available to authorized users.

Cellular Communications in the Heart

Heart failure is one of the leading causes of morbidity and mortality worldwide. Cardiac remodelling is first an adaptive, becoming a maladaptive, compensatory mechanism that finally causes ventricular dysfunction independently of the etiology of the initial insult. In the present article the authors describe the elements of the human heart, examining their basic functions and their inter-communication under both normal and pathological circumstances. Cardiac myocytes carry out mechanical and electrical functions of the heart and cardiac fibroblasts maintain its structural integrity. Several factors can affect fibroblast activation and under pathological stress they transdifferentiate into myofibroblasts. Endothelial cells have complex biological functions, including the control of vascular permeability, vasomotion, regulation of haemostasis, immune responses and angiogenesis. The extracellular matrix is a complex architectural network consisting of a variety of proteins. Various routes using a plethora of products and mediators contribute to the cross-talk of the myocytes with endothelial cells, extracellular matrix and cardiac fibroblasts. A better understanding of the entire mechanism of cellular communication by the established or the more recently discovered agents will certainly emerge promising new perspectives when looking at the prevention of heart failure and leading to more substantial therapeutic interventions.

Lipoxin A4 Attenuates Constitutive and TGF-β1-Dependent Profibrotic Activity in Human Lung Myofibroblasts

Idiopathic pulmonary fibrosis (IPF) is a common, progressive, and invariably lethal interstitial lung disease with no effective therapy. The key cell driving the development of fibrosis is the myofibroblast. Lipoxin A₄ (LXA₄) is an anti-inflammatory lipid, important in the resolution of inflammation, and it has potential antifibrotic activity. However, the effects of LXA₄ on primary human lung myofibroblasts (HLMFs) have not previously been investigated. Therefore, the aim of this study was to examine the effects of LXA₄ on TGF-β1–dependent responses in IPF- and nonfibrotic control (NFC)–derived HLMFs. HLMFs were isolated from IPF and NFC patients and grown in vitro. The effects of LXA₄ on HLMF proliferation, collagen secretion, α-smooth muscle actin (αSMA) expression, and Smad2/3 activation were examined constitutively and following TGF-β1 stimulation. The LXA₄ receptor (ALXR) was expressed in both NFC- and IPF-derived HLMFs. LXA₄ (10⁻¹⁰ and 10⁻⁸ mol) reduced constitutive αSMA expression, actin stress fiber formation, contraction, and nuclear Smad2/3, indicating regression from a myofibroblast to fibroblast phenotype. LXA₄ also significantly inhibited FBS-dependent proliferation and TGF-β1–dependent collagen secretion, αSMA expression, and Smad2/3 nuclear translocation in IPF-derived HLMFs. LXA₄ did not inhibit Smad2/3 phosphorylation. In summary, LXA₄ attenuated profibrotic HLMF activity and promoted HLMF regression to a quiescent fibroblast phenotype. LXA₄ or its stable analogs delivered by aerosol may offer a novel approach to the treatment of IPF.

Phosphatase and tensin homolog deleted on chromosome 10 contributes to phenotype transformation of fibroblasts in idiopathic pulmonary fibrosis via multiple pathways

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal disease and considered as a cancer-like disease. The phosphatase and tensin homologue deleted on chromosome 10 (PTEN) tumor suppressor has drawn attention in the pathogenesis of IPF. However, the role of PTEN in phenotypic transformation of lung fibroblasts, particularly in the migratory and invasive phenotype, is still elusive. Our data showed that PTEN expression was markedly reduced in both fibroblasts and myofibroblasts from IPF patients. Furthermore, loss of PTEN led to the transformation of normal fibroblasts to myofibroblasts and increased proliferation, apoptosis resistance, and migration/invasion activities. PTEN deficiency upregulated hyaluronan synthase 2 expression and thereby enhanced the invasion ability of fibroblasts. Cross-talk between PTEN and the transforming growth factor β1 (TGF-β1) pathway and PTEN reduction by hypoxia were observed. These findings suggest that PTEN is implicated in multiple pathways and plays a crucial role in the pathogenesis of IPF.

Sustained activation of toll-like receptor 9 induces an invasive phenotype in lung fibroblasts: possible implications in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is characterized by excessive scarring of the lung parenchyma, resulting in a steady decline of lung function and ultimately respiratory failure. The disease course of IPF is extremely variable, with some patients exhibiting stability of symptoms for prolonged periods of time, whereas others exhibit rapid progression and loss of lung function. Viral infections have been implicated in IPF and linked to disease severity; however, whether they directly contribute to progression is unclear. We previously classified patients as rapid and slow progressors on the basis of clinical features and expression of the pathogen recognition receptor, Toll-like receptor 9 (TLR9). Activation of TLR9 in vivo exacerbated IPF in mice and induced differentiation of myofibroblasts in vitro, but the mechanism of TLR9 up-regulation and progression of fibrosis are unknown. Herein, we investigate whether transforming growth factor (TGF)-β, a pleiotropic cytokine central to IPF pathogenesis, regulates TLR9 in lung myofibroblasts. Results showed induction of TLR9 expression by TGF-β in lung myofibroblasts and a distinct profibrotic myofibroblast phenotype driven by stimulation with the TLR9 agonist, CpG-DNA. Chronic TLR9 stimulation resulted in stably differentiated α-smooth muscle actin(+)/platelet-derived growth factor receptor α(+)/CD44(+)/matrix metalloproteinase-14(+)/matrix metalloproteinase-2(+) myofibroblasts, which secrete inflammatory cytokines, invade Matrigel toward platelet-derived growth factor, and resist hypoxia-induced apoptosis. These results suggest a mechanism by which TGF-β and TLR9 responses in myofibroblasts collaborate to drive rapid progression of IPF.

Plasminogen activator inhibitor-1 suppresses profibrotic responses in fibroblasts from fibrotic lungs

Idiopathic pulmonary fibrosis (IPF) is a fatal lung disease characterized by progressive interstitial scarification. A hallmark morphological lesion is the accumulation of myofibroblasts or fibrotic lung fibroblasts (FL-fibroblasts) in areas called fibroblastic foci. We previously demonstrated that the expression of both urokinase-type plasminogen activator (uPA) and the uPA receptor are elevated in FL-fibroblasts from the lungs of patients with IPF. FL-fibroblasts isolated from human IPF lungs and from mice with bleomycin-induced pulmonary fibrosis showed an increased rate of proliferation compared with normal lung fibroblasts (NL-fibroblasts) derived from histologically "normal" lung. Basal expression of plasminogen activator inhibitor-1 (PAI-1) in human and murine FL-fibroblasts was reduced, whereas collagen-I and α-smooth muscle actin were markedly elevated. Conversely, alveolar type II epithelial cells surrounding the fibrotic foci in situ, as well as those isolated from IPF lungs, showed increased activation of caspase-3 and PAI-1 with a parallel reduction in uPA expression. Transduction of an adenovirus PAI-1 cDNA construct (Ad-PAI-1) suppressed expression of uPA and collagen-I and attenuated proliferation in FL-fibroblasts. On the contrary, inhibition of basal PAI-1 in NL-fibroblasts increased collagen-I and α-smooth muscle actin. Fibroblasts isolated from PAI-1-deficient mice without lung injury also showed increased collagen-I and uPA. These changes were associated with increased Akt/phosphatase and tensin homolog proliferation/survival signals in FL-fibroblasts, which were reversed by transduction with Ad-PAI-1. This study defines a new role of PAI-1 in the control of fibroblast activation and expansion and its role in the pathogenesis of fibrosing lung disease and, in particular, IPF.

The angiotensin-converting enzyme 2/angiotensin (1-7)/Mas axis protects against lung fibroblast migration and lung fibrosis by inhibiting the NOX4-derived ROS-mediated RhoA/Rho kinase pathway

Reactive oxygen species (ROS) generated by NADPH oxidase-4 (NOX4) have been shown to initiate lung fibrosis. The migration of lung fibroblasts to the injured area is a crucial early step in lung fibrosis. The angiotensin-converting enzyme 2 (ACE2)/angiotensin (1-7) [Ang(1-7)]/Mas axis, which counteracts the ACE/angiotensin II (AngII)/angiotensin II type 1 receptor (AT1R) axis, has been shown to attenuate pulmonary fibrosis. Nevertheless, the exact molecular mechanism remains unclear.

AIMS

To investigate the different effects of the two axes of the renin-angiotensin system (RAS) on lung fibroblast migration and extracellular matrix accumulation by regulating the NOX4-derived ROS-mediated RhoA/Rho kinase (Rock) pathway.

RESULTS

In vitro, AngII significantly increased the NOX4 level and ROS production in lung fibroblasts, which stimulated cell migration and α-collagen I synthesis through the RhoA/Rock pathway. These effects were attenuated by N-acetylcysteine (NAC), diphenylene iodonium, and NOX4 RNA interference. Moreover, Ang(1-7) and lentivirus-mediated ACE2 (lentiACE2) suppressed AngII-induced migration and α-collagen I synthesis by inhibiting the NOX4-derived ROS-mediated RhoA/Rock pathway. However, Ang(1-7) alone exerted analogous effects on AngII. In vivo, constant infusion with Ang(1-7) or intratracheal instillation with lenti-ACE2 shifted the RAS balance toward the ACE2/Ang(1-7)/Mas axis, alleviated bleomycin-induced lung fibrosis, and inhibited the RhoA/Rock pathway by reducing NOX4-derived ROS.

INNOVATION

This study suggests that the ACE2/Ang(1-7)/Mas axis may be targeted by novel pharmacological antioxidant strategies to treat lung fibrosis induced by AngII-mediated ROS.

CONCLUSION

The ACE2/Ang(1-7)/Mas axis protects against lung fibroblast migration and lung fibrosis by inhibiting the NOX4-derived ROS-mediated RhoA/Rock pathway.

Prostaglandin E2 switches from a stimulator to an inhibitor of cell migration after epithelial-to-mesenchymal transition

Epithelial-mesenchymal transition (EMT) is critical for embryonic development, and this process is recapitulated in adults during wound healing, tissue regeneration, fibrosis and cancer progression. Cell migration is believed to play a key role in both normal wound repair and in abnormal tissue remodeling. Prostaglandin E2 (PGE2) inhibits fibroblast chemotaxis, but stimulates chemotaxis in airway epithelial cells. The current study was designed to explore the role of PGE2 and its four receptors on airway epithelial cell migration following EMT using both the Boyden blindwell chamber chemotaxis assay and the wound closure assay. EMT in human bronchial epithelial cells (HBECs) was induced by TGF-β1 and a mixture of cytokines (IL-1β, TNF-α, and IFN-γ). PGE2 and selective agonists for all four EP receptors stimulated chemotaxis and wound closure in HBECs. Following EMT, the EP1 and EP3 agonists were without effect, while the EP2 and EP4 agonists inhibited chemotaxis as did PGE2. The effects of the EP2 and EP4 receptors on HBEC and EMT cell migration were further confirmed by blocking the expected signaling pathways. Taken together, these results demonstrate that PGE2 switches from a stimulator to an inhibitor of cell migration following EMT of airway epithelial cells and that this inhibition is mediated by an altered effect of EP2 and EP4 signaling and an apparent loss of the stimulatory effects of EP1 and EP3. Change in the PGE2 modulation of chemotaxis may play a role in repair following injury.

Fibroblasts that resist cigarette smoke-induced senescence acquire profibrotic phenotypes

This study assessed the effect of extended exposure to cigarette smoke extract (CSE) on tissue repair functions in lung fibroblasts. Human fetal (HFL-1) and adult lung fibroblasts were exposed to CSE for 14 days. Senescence-associated β-galactosidase (SA β-gal) expression, cell proliferation, and tissue repair functions including chemotaxis and gel contraction were assessed. HFL-1 proliferation was inhibited by CSE and nearly half of the CSE-exposed cells were SA β-gal positive after 14 days exposure, whereas 33% of adult lung fibroblasts were SA β-gal positive in response to 10% CSE exposure. The SA β-gal-positive cells did not proliferate as indicated by bromodeoxyuridine incorporation. In contrast, cells negative for SA β-gal after CSE exposure proliferated faster than cells never exposed to CSE. These nonsenescent cells migrated more and contracted collagen gels more than control cells. CSE exposure stimulated TGF-β1 production, and both inhibition of TGF-β receptor kinase and TGF-β1 siRNA blocked CSE modulation of fibroblast function. Extended exposure to CSE might induce two different fibroblast phenotypes, a senescent and a profibrotic phenotype. The fibroblasts that resist CSE-induced cellular senescence may contribute to the pathogenesis of idiopathic pulmonary fibrosis and could contribute to fibrotic lesions in chronic obstructive pulmonary disease acting through a TGF-β1-mediated pathway. In contrast, the senescent cells may contribute to the pathogenesis of emphysema.

Ceramide kinase is required for a normal eicosanoid response and the subsequent orderly migration of fibroblasts

In these studies, the role of ceramide-1-phosphate (C1P) in the wound-healing process was investigated. Specifically, fibroblasts isolated from mice with the known anabolic enzyme for C1P, ceramide kinase (CERK), ablated (CERK^−/− mice) and their wild-type littermates (CERK^+/+) were subjected to in vitro wound-healing assays. Simulation of mechanical trauma of a wound by scratching a monolayer of fibroblasts from CERK^+/+ mice demonstrated steadily increasing levels of arachidonic acid in a time-dependent manner in stark contrast to CERK^−/− fibroblasts. This observed difference was reflected in scratch-induced eicosanoid levels. Similar, but somewhat less intense, changes were observed in a more complex system utilizing skin biopsies obtained from CERK-null mice. Importantly, C1P levels increased during the early stages of human wound healing correlating with the transition from the inflammatory stage to the peak of the fibroplasia stage (e.g., proliferation and migration of fibroblasts). Finally, the loss of proper eicosanoid response translated into an abnormal migration pattern for the fibroblasts isolated from CERK^−/−. As the proper migration of fibroblasts is one of the necessary steps of wound healing, these studies demonstrate a novel requirement for the CERK-derived C1P in the proper healing response of wounds.

Up-regulation of heparan sulfate 6-O-sulfation in idiopathic pulmonary fibrosis

Heparan sulfate proteoglycans (HSPGs) are integral components of the lung. Changes in HSPGs have been documented in idiopathic pulmonary fibrosis (IPF). Many of the biological functions of HSPGs are mediated by heparan sulfate (HS) side chains, and little is understood about these side chains in the pathogenesis of IPF. The aims of this study were to compare HS structure between normal and IPF lungs and to examine how changes in HS regulate the fibrotic process. HS disaccharide analysis revealed that HS 6-O-sulfation was significantly increased in IPF lungs compared with normal lungs, concomitant with overexpression of HS 6-O-sulfotransferases 1 and 2 (HS6ST1/2) mRNA. Immunohistochemistry revealed that HS6ST2 was specifically expressed in bronchial epithelial cells, including those lining the honeycomb cysts in IPF lungs, whereas HS6ST1 had a broad expression pattern. Lung fibroblasts in the fibroblastic foci of IPF lungs expressed HS6ST1, and overexpression of HS6ST1 mRNA was observed in primary lung fibroblasts isolated from IPF lungs compared with those from normal lungs. In vitro, small interference RNA-mediated silencing of HS6ST1 in primary normal lung fibroblasts resulted in reduced Smad2 expression and activation and in reduced expression of collagen I and α-smooth muscle actin after TGF-β1 stimulation. Similar results were obtained in primary IPF lung fibroblasts. Furthermore, silencing of HS6ST1 in normal and IPF lung fibroblasts resulted in significant down-regulation of TβRIII (betaglycan). In summary, HS 6-O-sulfation is up-regulated in IPF with overexpression of HS6ST1 and HS6ST2, and overexpression of HS6ST1 in lung fibroblasts may regulate their fibrotic responses to TGF-β1.

Cellular mechanisms of tissue fibrosis. 7. New insights into the cellular mechanisms of pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a devastating disease characterized by severe and progressive scar formation in the gas-exchange regions of the lung. Despite years of research, therapeutic treatments remain elusive and there is a pressing need for deeper mechanistic insights into the pathogenesis of the disease. In this article, we review our current knowledge of the triggers and/or perpetuators of pulmonary fibrosis with special emphasis on the alveolar epithelium and the underlying mesenchyme. In doing so, we raise a number of questions highlighting critical voids and limitations in our current understanding and study of this disease.

Urokinase-type plasminogen activator receptor (uPAR) ligation induces a raft-localized integrin signaling switch that mediates the hypermotile phenotype of fibrotic fibroblasts

The urokinase-type plasminogen activator receptor (uPAR) is a glycosylphosphatidylinositol-linked membrane protein with no cytosolic domain that localizes to lipid raft microdomains. Our laboratory and others have documented that lung fibroblasts from patients with idiopathic pulmonary fibrosis (IPF) exhibit a hypermotile phenotype. This study was undertaken to elucidate the molecular mechanism whereby uPAR ligation with its cognate ligand, urokinase, induces a motile phenotype in human lung fibroblasts. We found that uPAR ligation with the urokinase receptor binding domain (amino-terminal fragment) leads to enhanced migration of fibroblasts on fibronectin in a protease-independent, lipid raft-dependent manner. Ligation of uPAR with the amino-terminal fragment recruited α5β1 integrin and the acylated form of the Src family kinase, Fyn, to lipid rafts. The biological consequences of this translocation were an increase in fibroblast motility and a switch of the integrin-initiated signal pathway for migration away from the lipid raft-independent focal adhesion kinase pathway and toward a lipid raft-dependent caveolin-Fyn-Shc pathway. Furthermore, an integrin homologous peptide as well as an antibody that competes with β1 for uPAR binding have the ability to block this effect. In addition, its relative insensitivity to cholesterol depletion suggests that the interactions of α5β1 integrin and uPAR drive the translocation of α5β1 integrin-acylated Fyn signaling complexes into lipid rafts upon uPAR ligation through protein-protein interactions. This signal switch is a novel pathway leading to the hypermotile phenotype of IPF patient-derived fibroblasts, seen with uPAR ligation. This uPAR dependent, fibrotic matrix-selective, and profibrotic fibroblast phenotype may be amenable to targeted therapeutics designed to ameliorate IPF.