Keratinocyte Growth Factor Expression by Fibroblasts in Pulmonary Fibrosis

Effect of applying Lactiplantibacillus plantarum subsp. plantarum N793 to the scalps of men and women with thinning hair: a randomized, double-blind, placebo-controlled, parallel-group study

Lactiplantibacillus plantarum subsp. plantarum N793 (N793) is a lactic acid bacterium (LAB) isolated from corn. We previously showed that N793 increases the level of keratinocyte growth factor, which is required for hair growth, in the culture supernatant of human follicle dermal papilla cells. Additionally, an open-label, single-arm study reported that applying a lotion containing N793 to the scalp for 24 weeks improved hair density in men and women with thinning hair. The present study was a double-blind, placebo-controlled, parallel-group study aimed at verifying the efficacy of N793 for thinning hair. A lotion containing N793, and a control lotion (placebo) were applied once daily for 24 weeks to 104 healthy Japanese men and women. Analysis of all participants revealed no difference in hair density between the N793 and placebo groups. However, an additional analysis limited to participants with relatively mild progression of thinning hair showed a significantly better hair density in the N793 group than in the placebo group. These findings suggest that topical application of N793 improves thinning hair in men and women when the condition's progression is relatively mild.

FGF19 is Downregulated in Idiopathic Pulmonary Fibrosis and Inhibits Lung Fibrosis in Mice

IPF is a devastating lung disease with limited therapeutic possibilities. FGF19, an endocrine FGF, was recently shown to decrease liver fibrosis. To ask whether FGF19 had anti-fibrotic properties in the lung and decipher its effects on common features associated with lung fibrogenesis. We assessed, by Elisa, FGF19 levels in plasma and bronchoalveolar lavage fluids (BALF)obtained from controls and IPF patients. In vivo, using an intravenously administered adeno11 associated virus (AAV), we overexpressed FGF19 at the fibrotic phase of two experimental models of murine lung fibrosis and assessed its effect on lung morphology, lung collagen content, fibrosis markers and pro fibrotic mediator expression, at mRNA and protein levels. In vitro, we investigated whether FGF19 could modulate the TGFβ-induced differentiation of primary human lung fibroblast into myofibroblast and the apoptosis of murine alveolar type II cell. While FGF19 was not detected in BALF, FGF19 concentration was decreased in the plasma of IPF patients compared to controls. In vivo, the overexpression of FGF19 was associated with a marked decrease of lung fibrosis and fibrosis markers, with a decrease of pro fibrotic mediator expression and lung collagen content. In vitro, FGF19 decreased alveolar type 2 epithelial cell apoptosis through the decrease of the proapoptotic BIM protein expression and prevented TGF-ß induced myofibroblast differentiation through the inhibition of JNK phosphorylation. Altogether these data identify FGF19 as an anti-fibrotic molecule with a potential therapeutic interest in fibrotic lung disorders.

Adipose Tissue-Derived Mesenchymal Stem Cells Protect Against Amiodarone-Induced Lung Injury in Rats

Pulmonary fibrosis (PF) is a progressive and irreversible lung disease, characterized by poor prognosis with limited treatment options. Mesenchymal stem cells (MSCs) are multi-potent cells having the ability to self-renew and differentiate into multiple tissues, thus considered a novel treatment option. The present study aimed to investigate the possible antifibrotic effect of undifferentiated adipose tissue-derived mesenchymal stem cell (AD-MSC) therapy on PF experimentally induced in rats using amiodarone (AMD). AMD (30 mg/kg) was given orally, once daily for 12 consecutive weeks to induce lung fibrosis. Following the confirmation of lung damage with histopathological examination, AD-MSCs (2 × 10⁶ and 4 × 10⁶ undifferentiated MSCs) were injected once intravenously, followed by 2 months for treatment. AMD induced focal fibroblastic cells proliferation in the peribronchiolar tissue, as well as in between the collapsed emphysematous alveoli. Also, AMD significantly increased serum and lung homogenate fibroblast growth factor-7 (FGF7), Clara cell protein-16 (CC16), and cytokeratin -19 (CK19) levels, as well as the expression of both iNOS and NFкB in the lung alveoli. Moreover, AMD caused excessive collagen deposition and increased alpha smooth muscle actin (α-SMA) expression. All findings significantly regressed on stem cell therapy in both doses, with superior effect of the high dose, providing evidence that adipose tissue-derived MSCs could be a promising approach for the treatment of PF. Graphical Abstract.

Investigation of circular RNAs and related genes in pulmonary fibrosis based on bioinformatics analysis

Pulmonary fibrosis is a lethal inflammatory disease. In this study, we aimed to explore the potential-related circular RNAs (circRNAs) and genes that are associated with pulmonary fibrosis. Pulmonary fibrosis rat models were constructed and the fibrosis deposition was detected using hematoxylin and eosin and Masson staining. The differentially expressed circRNAs were obtained through RNA sequencing. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were further performed to uncover the key function and pathways in pulmonary fibrosis. The interaction networks between circRNAs and their downstream micro RNAs (miRNAs) and genes were constructed by Cytoscape Software. The quantitative polymerase chain reaction was performed to validate the expression of 10 candidate circRNAs and five of them were performed ringwise sequencing in pulmonary fibrosis rats. We further selected five candidate circRNAs target miRNAs and messenger RNAs and validated by real-time polymerase chain reaction. The pulmonary fibrosis models were successfully constructed according to the pathological examination. circRNAs were differentially expressed between the pulmonary fibrosis and normal pulmonary tissues. GO analysis verified that the differentially expressed circRNAs were significantly clustered in the cellular component, molecular function, and biological process. In the KEGG analysis, circRNAs were enriched in the following pathways: antigen processing and presentation, phagosome, PI3K-AKt signaling pathway, HTLV-I infection, and Herpes simplex infection. After validation in pulmonary fibrosis rat models, it was found that five of those circRNAs (chr9:113534327|113546234 [down], chr1:200648164|200672411 [down], chr5:150850432|150865550 [up], chr20:14319170|14326640 [down], and chr10:57634023|57634588 [down]) showed a relatively consistent trend with predictions. Validation of these circRNAs target miRNAs and genes showed that chr9:113534327|113546234, chr20:14319170|14326640, and chr10:57634023|57634588 were implicated in Notch1 activated transforming growth factor-β (TGF-β) signaling pathway. The study demonstrated that a series of circRNAs are differentially expressed in pulmonary fibrosis rats. These circRNAs, especially TGF-β- and Notch1-related circRNAs might play an important role in regulating pulmonary fibrogenesis.

Prognostic value of IFN-γ, sCD163, CCL2 and CXCL10 involved in acute exacerbation of idiopathic pulmonary fibrosis

OBJECTIVE

Acute exacerbation of idiopathic pulmonary fibrosis (AE-IPF) is of concern because of its propensity for rapid deterioration and high mortality. Its aetiology and mechanism are still unclear. The aims of this study were to clarify the pathophysiology differences between AE-IPF and stable IPF (S-IPF) by comparing the serum levels of various cytokines and chemokines in the two groups and to identify those involvement in the occurrence of acute exacerbation and associated with mortality.

METHODS

The study included 28 patients with AE-IPF, 32 patients with S-IPF, and 18 healthy control subjects. We measured the serum cytokine and chemokine levels in all cases by multiplex assay. Serum levels of cytokines and chemokines were compared between AE-IPF and S-IPF subjects. Logistic regression analysis was applied to identify the ability of these variables to predict acute exacerbation. Kaplan-Meier curves were used to analyse survival and Cox proportional hazard regression was used to identify predictors of survival.

RESULTS

Levels of several cytokines and chemokines were significantly higher in both patient groups with IPF (with the exception of interleukin-2 [IL-2], chemokine cc-motif ligand 3, and RANTES [regulation upon activation normal T-cell express sequence]) than in healthy controls. Serum IL-1β (p = 0.008) and interferon (IFN)-γ (p = 0.007) levels tended to be higher in patients with AE-IPF than in those with S-IPF. The concentration of chemokine cc-motif ligand (CCL) 2 was significantly higher in bronchoalveolar lavage fluid than in serum (p = 0.001). Higher C-reactive protein, lactate dehydrogenase, percent forced vital capacity, percent diffusing capacity of the lung for carbon monoxide, and IFN-γ values in the patients with IPF were correlated with acute exacerbation status, with respective odds ratios of 1.241 (p = 0.011), 1.050 (p = 0.004), 1.043 (p = 0.001), 0.927 (p = 0.014), and 0.929 (p = 0.020). Acute exacerbation status was associated with an increased risk of mortality (hazard ratio 0.107, 95% confidence interval 0.036-0.314; p < 0.001). Univariate Cox regression demonstrated an association of IFN-γ, CCL2, C-X-C motif chemokine 10 (CXCL10) and sCD163 levels with an increased mortality risk (p = 0.015, p = 0.002, p = 0.001, and p = 0.030, respectively).

CONCLUSIONS

Our data demonstrate that serum levels of some pro-inflammatory cytokines and macrophage chemokines are upregulated during acute exacerbations of IPF and that these exacerbations are associated with the serum IFN-γ level. Chemokines and protein such as sCD163, CCL2, and CXCL10 are associated with activation of macrophages and may have a serious impact on overall survival in patients with IPF.

Idiopathic pulmonary fibrosis (IPF) signaling pathways and protective roles of melatonin

Idiopathic pulmonary fibrosis (IPF) is characterized by the progressive loss of lung function due to tissue scarring. A variety of pro-inflammatory and pro-fibrogenic factors including interleukin‑17A, transforming growth factor β, Wnt/β‑catenin, vascular endothelial growth factor, platelet-derived growth factor, fibroblast growth factors, endotelin‑1, renin angiotensin system and impaired caveolin‑1 function are involved in the IPF pathogenesis. Current therapies for IPF have some limitations and this highlights the need for effective therapeutic agents to treat this fatal disease. Melatonin and its metabolites are broad-spectrum antioxidants that not only remove reactive oxygen and nitrogen species by radical scavenging but also up-regulate the expression and activity of endogenous antioxidants. Via these actions, melatonin and its metabolites modulate a variety of molecular pathways in different pathophysiological conditions. Herein, we review the signaling pathways involved in the pathophysiology of IPF and the potentially protective effects of melatonin on these pathways.

Porcine CD14 gene silencing partially inhibited the bacterial immune response mediated by TLR4 signaling pathway

Cluster of differentiation antigen 14 (CD14) is the membrane receptor protein in Toll-like Receptor 4 (TLR4) signaling pathway, which plays an important regulation role in not only innate immune response but also adaptive immune response. In this study, the pig kidney epithelial cell (PK15) line with CD14 gene silencing mediated by lentivirus was established and cells of CD14-RNAi and NC group were exposed to three kinds of Escherichia coli (E. coli F18ab, E. coli F18ac and E. coli K88ac) and LPS. Then qPCR and western blot were used to detect expression levels of TLR4 signaling pathway-related genes. Finally, ELISA was used to detect the level of proinflammatory cytokines in the cell culture supernatant. The results showed that the expression level of TLR4 signaling pathway-related genes in the entire signal pathway had obvious increases when cells were exposed to the stimulation induced by E. coli and LPS. In addition, the expression levels of CD14-RNAi group were overall significantly lower than NC group (P<0.05 or P<0.01), which was the same with the release levels of proinflammatory cytokines. This study revealed that pig CD14 gene silencing partially inhibited immune response to E. coli F18 invasion mediated by TLR4 signaling pathway.

Gene profile of fibroblasts identify relation of CCL8 with idiopathic pulmonary fibrosis

Background

Idiopathic pulmonary fibrosis (IPF) is characterized by the complex interaction of cells involved in chronic inflammation and fibrosis. Global gene expression of a homogenous cell population will identify novel candidate genes.

Methods

Gene expression of fibroblasts derived from lung tissues (8 IPF and 4 controls) was profiled, and ontology and functional pathway were analyzed in the genes exhibiting >2 absolute fold changes with p-values < 0.05. CCL8 mRNA and protein levels were quantified using real-time PCR and ELISA. CCL8 localization was evaluated by immunofluorescence staining.

Results

One hundred seventy eight genes differentially expressed and 15 genes exhibited >10-fold change. Among them, 13 were novel in relation with IPF. CCL8 expression was 22.8-fold higher in IPF fibroblasts. The levels of CCL8 mRNA and protein were 3 and 9-fold higher in 14 IPF fibroblasts than those in 10 control fibroblasts by real-time PCR and ELISA (p = 0.022 and p = 0.026, respectively). The CCL8 concentrations in BAL fluid was significantly higher in 86 patients with IPF than those in 41 controls, and other interstitial lung diseases including non-specific interstitial pneumonia (n = 22), hypersensitivity pneumonitis (n = 20) and sarcoidosis (n = 19) (p < 0.005, respectively). Cut-off values of 2.29 pg/mL and 0.43 pg/mL possessed 80.2 and 70.7% accuracy for the discrimination of IPF from NC and the other lung diseases, respectively. IPF subjects with CCL8 levels >28.61 pg/mL showed shorter survival compared to those with lower levels (p = 0.012). CCL8 was expressed by α-SMA-positive cells in the interstitium of IPF.

Conclusions

Transcriptome analysis identified several novel IPF-related genes. Among them, CCL8 is a candidate molecule for the differential diagnosis and prediction of survival.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-016-0493-6) contains supplementary material, which is available to authorized users.

Activation of heat shock response augments fibroblast growth factor-1 expression in wounded lung epithelium

We previously showed that coincident exposure to heat shock (HS; 42°C for 2 h) and TNF-α synergistically induces apoptosis in mouse lung epithelium. We extended this work by analyzing HS effects on human lung epithelial responses to clinically relevant injury. Cotreatment with TNF-α and HS induced little caspase-3 and poly(ADP-ribose) polymerase cleavage in human small airway epithelial cells, A549 cells, and BEAS2B cells. Scratch wound closure rates almost doubled when A549 and BEAS2B cells and air-liquid interface cultures of human bronchial epithelial cells were heat shocked immediately after wounding. Microarray, qRT-PCR, and immunoblotting showed fibroblast growth factor 1 (FGF1) to be synergistically induced by HS and wounding. Enhanced FGF1 expression in HS/wounded A549 was blocked by inhibitors of p38 MAPK (SB203580) or HS factor (HSF)-1 (KNK-437) and in HSF1 knockout BEAS2B cells. PCR demonstrated FGF1 to be expressed from the two most distal promoters in wounded/HS cells. Wound closure in HS A549 and BEAS2B cells was reduced by FGF receptor-1/3 inhibition (SU-5402) or FGF1 depletion. Exogenous FGF1 accelerated A549 wound closure in the absence but not presence of HS. In the presence of exogenous FGF1, HS slowed wound closure, suggesting that it increases FGF1 expression but impairs FGF1-stimulated wound closure. Frozen sections from normal and idiopathic pulmonary fibrosis (IPF) lung were analyzed for FGF1 and HSP70 by immunofluorescence confocal microscopy and qRT-PCR. FGF1 and HSP70 mRNA levels were 7.5- and 5.9-fold higher in IPF than normal lung, and the proteins colocalized to fibroblastic foci in IPF lung. We conclude that HS signaling may have an important impact on gene expression contributing to lung injury, healing, and fibrosis.

Age-driven developmental drift in the pathogenesis of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive and usually lethal disease of unknown aetiology. A growing body of evidence supports that IPF represents an epithelial-driven process characterised by aberrant epithelial cell behaviour, fibroblast/myofibroblast activation and excessive accumulation of extracellular matrix with the subsequent destruction of the lung architecture. The mechanisms involved in the abnormal hyper-activation of the epithelium are unclear, but we propose that recapitulation of pathways and processes critical to embryological development associated with a tissue specific age-related stochastic epigenetic drift may be implicated. These pathways may also contribute to the distinctive behaviour of IPF fibroblasts. Genomic and epigenomic studies have revealed that wingless/Int, sonic hedgehog and other developmental signalling pathways are reactivated and deregulated in IPF. Moreover, some of these pathways cross-talk with transforming growth factor-β activating a profibrotic feedback loop. The expression pattern of microRNAs is also dysregulated in IPF and exhibits a similar expression profile to embryonic lungs. In addition, senescence, a process usually associated with ageing, which occurs early in alveolar epithelial cells of IPF lungs, likely represents a conserved programmed developmental mechanism. Here, we review the major developmental pathways that get twisted in IPF, and discuss the connection with ageing and potential therapeutic approaches.

Tracheal Smooth Muscle Cells Stimulated by Stem Cell Factor-c-Kit Coordinate the Production of Transforming Growth Factor-β1 and Fibroblast Growth Factor-2 Mediated by Chemokine (C-C Motif) Ligand 3

The aim of this study was to evaluate the mechanism involved in the stem cell factor (SCF)-induced production of fibroblast growth factor-2 (FGF-2), transforming growth factor-β1 (TGF-β1), and chemokine (C-C motif) ligand 3 (CCL3) in tracheal smooth muscle cells (tSMCs) and the signaling pathway involved in the process. tSMC primary cultures were stimulated with SCF and evaluated at 24 h. Cells treated with specific antibodies did not show any immunolabeling for cytokeratin or fibroblast activation protein, but were positive for α-smooth muscle actin, indicating the purity of the primary cell line. Western blot analysis showed constitutive phosphorylation of c-Kit, as well as increased total protein and phosphorylated c-Kit levels in tSMCs after SCF stimulation. Flow cytometry analysis also showed an increase in cell-surface c-Kit expression in the presence of SCF. SCF induced TGF-β mRNA expression in tSMCs, as well as the production of TGF-β1, CCL3, and FGF-2. Pretreatment with anti-CCL3 antibody blocked TGF-β1 expression and partially inhibited FGF-2 production. On the other hand, anti-c-Kit antibody blocked TGF-β1 expression and FGF-2 production. Thus, TGF-β1 and FGF-2 production were mediated by CCL3 production through c-Kit. Pretreatment with mitogen-activated protein kinase kinase 1, p38, and Jun N-terminal kinase inhibitors showed that the effects mediated by SCF were involved with the modulation of mitogen-activated protein kinase (MAPK) pathways. Development of inhibitors targeting CCL3 through MAPK activation could thus be an attractive strategy to inhibit tSMC activation during asthma.

Exogenous pulmonary surfactant prevents the development of intra-abdominal adhesions in rats

Intra-abdominal adhesions are major post-operative complications for which no effective means of prevention is available. We aimed to evaluate the efficacy of exogenous pulmonary surfactant administration in the prevention of post-operative abdominal adhesions. Rats were randomly assigned to undergo laparotomy (L) or gastroenterostomy (GE) and then treated with surfactant (groups L-S and GE-S, respectively). Intra-abdominal adhesions, collagen fibre content, metalloproteinase (MMP)-9, expression of growth factors (TGF-β, KGF and VEGF), type III procollagen (PCIII) and pro-caspase 3, as well as isolectin B4 and ED1-positive cells expressing MMP-9, were evaluated. Groups treated with surfactant (GE-S and L-S) exhibited fewer adhesions. A significant reduction in collagen fibre content was observed in GE-S compared to GE animals (P < 0.001). In situ and gelatin zymography analysis showed higher MMP-9 expression and activity in the GE-S group compared to the GE group (P < 0.05). ED1-positive cell counts were significantly higher in the GE-S group (P < 0.001) than in the GE group. Virtually all cells positive for ED1 were MMP-9+. Double-labelling of MMP-9 with IB4 showed no significant differences between GE-S and GE groups. TGF-β, KGF, PCIII and pro-caspase-3 mRNA expression decreased significantly in GE-S compared to GE animals (P < 0.05). Surfactant administration also reduced apoptosis in the GE-S group. These findings suggest that surfactant reduces the intra-abdominal adhesions triggered by laparotomy and gastrointestinal anastomosis, thus preventing fibrosis formation at the peritoneal surfaces. This preclinical study suggests an innovative treatment strategy for intra-abdominal adhesions with surfactant and to endorse its putative mechanism of action.

Increased FGF1-FGFRc expression in idiopathic pulmonary fibrosis

Background

Recent clinical studies show that tyrosine kinase inhibitors slow the rate of lung function decline and decrease the number of acute exacerbations in patients with Idiopathic Pulmonary Fibrosis (IPF). However, in the murine bleomycin model of fibrosis, not all tyrosine kinase signaling is detrimental. Exogenous ligands Fibroblast Growth Factor (FGF) 7 and 10 improve murine lung repair and increase survival after injury via tyrosine kinase FGF receptor 2b-signaling. Therefore, the level and location of FGF/FGFR expression as well as the exogenous effect of the most highly expressed FGFR2b ligand, FGF1, was analyzed on human lung fibroblasts.

Methods

FGF ligand and receptor expression was evaluated in donor and IPF whole lung homogenates using western blotting and qPCR. Immunohistochemistry for FGF1 and FGFR1/2/3/4 were performed on human lung tissue. Lastly, the effects of FGF1, a potent, multi-FGFR ligand, were studied on primary cultures of IPF and non-IPF donor fibroblasts. Western blots for pro-fibrotic markers, proliferation, FACS for apoptosis, transwell assays and MetaMorph analyses on cell cultures were performed.

Results

Whole lung homogenate analyses revealed decreased FGFR b-isoform expression, and an increase in FGFR c-isoform expression. Of the FGFR2b-ligands, FGF1 was the most significantly increased in IPF patients; downstream targets of FGF-signaling, p-ERK1/2 and p-AKT were also increased. Immunohistochemistry revealed FGF1 co-localization within basal cell sheets, myofibroblast foci, and Surfactant protein-C positive alveolar epithelial type-II cells as well as co-localization with FGFR1, FGFR2, FGFR3, FGFR4 and myofibroblasts expressing the migratory marker Fascin. Both alone and in the presence of heparin, FGF1 led to increased MAPK-signaling in primary lung fibroblasts. While smooth muscle actin was unchanged, heparin + FGF1 decreased collagen production in IPF fibroblasts. In addition, FGF1 + heparin increased apoptosis and cell migration. The FGFR inhibitor (PD173074) attenuated these effects.

Conclusions

Strong expression of FGF1/FGFRs in pathogenic regions of IPF suggest that aberrant FGF1-FGFR signaling is increased in IPF patients and may contribute to the pathogenesis of lung fibrosis by supporting fibroblast migration and increased MAPK-signaling.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-015-0242-2) contains supplementary material, which is available to authorized users.

Epithelium-dependent profibrotic milieu in the pathogenesis of idiopathic pulmonary fibrosis: current status and future directions

BACKGROUND AND AIM

Idiopathic pulmonary fibrosis (IPF) is characterized by hyperplasia of type II alveolar epithelial cells, aggregation of activated (myo)fibroblasts and excessive deposition of extracellular matrix, which will ultimately lead to lung architecture destruction with no proven effective therapies. Despite a significant increase in our understanding on the etiology and pathogenesis of IPF, the real triggers that initiate epithelial cell injury and promote fibrosis evolution are still elusive. We wanted to discuss the evolution of hypothesis on IPF pathogenesis and to suggest some new directions which need to be further elucidated.

METHODS

We have done a literature search in PubMed database by using the term 'idiopathic pulmonary fibrosis' AND (pathogenesis OR inflammation OR wound healing OR apoptosis OR extracellular matrix OR animal model).

RESULTS

Inflammatory hypothesis had been the dominant idea for several decades which suggests that chronic inflammation drives the onset and advance of the fibrotic process. However, it is seriously challenged nowadays because lung tissues from IPF patients exhibit little inflammatory lesions. Also, anti-inflammation therapy failed to exert a beneficial effect to IPF patients. Furthermore, experimental lung fibrosis can be realized independent of inflammation. Today, modern paradigm suggests that IPF is mainly driven by the profibtic milieu formed by epithelial injury/ disability and dysregulated epithelial mesenchymal interaction.

CONCLUSIONS

Epithelium-dependent profibrotic milieu formation and mesenchymal activation is the current view on the pathogenesis of IPF. New evidence from more analogous animal models may emerge and shift our thinking to a new and more faithful concept in the future.

Idiopathic pulmonary fibrosis: from epithelial injury to biomarkers--insights from the bench side

Idiopathic pulmonary fibrosis (IPF) is the most frequent fibrotic diffuse parenchymal lung disease. Its prognosis is devastating: >50% of the patients die within 3 years after diagnosis. Options for the treatment of IPF are limited and lung transplantation is the only 'curative' therapy. Currently, in the absence of validated indicators of disease progression/activity and diagnostic tools, the clinical management of IPF remains a major challenge. A better understanding of the pathogenesis of IPF is critical for the identification of new therapeutic targets as well as molecules that may serve as surrogate markers for clinically significant endpoints. The current paradigm on the mechanisms leading from a normal to a fibrotic lung postulates that chronic epithelial lesion leads to aberrant wound healing activation, which is characterized by deregulated fibroblast proliferation and activation together with an uncontrolled extracellular matrix synthesis. In this review, we shed light on the role of epithelial cell damage in the pathogenesis of fibrosis. Finally, we examine the markers of epithelial damage and their potential use as biomarkers and the future of this continuously expanding field.

Hepatocyte growth factor and lung fibrosis

Idiopathic pulmonary fibrosis is currently believed to be driven by alveolar epithelial cells, with abnormally activated alveolar epithelial cells accumulating in an attempt to repair injured alveolar epithelium (1). Thus, targeting the alveolar epithelium to prevent or inhibit the development of pulmonary fibrosis might be an interesting therapeutic option in this disease. Hepatocyte growth factor (HGF) is a growth factor for epithelial and endothelial cells, which is secreted by different cell types, especially fibroblasts and neutrophils. HGF has mitogenic, motogenic, and morphogenic properties and exerts an antiapoptotic action on epithelial and endothelial cells. HGF has also proangiogenic effect. In vitro, HGF inhibits epithelial-to-mesenchymal cell transition and promotes myofibroblast apoptosis. In vivo, HGF has antifibrotic properties demonstrated in experimental models of lung, kidney, heart, skin, and liver fibrosis. Hence, the modulation of HGF may be an attractive target for the treatment of lung fibrosis.

The hedgehog system machinery controls transforming growth factor-β-dependent myofibroblastic differentiation in humans: involvement in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a devastating disease of unknown cause. Key signaling developmental pathways are aberrantly expressed in IPF. The hedgehog pathway plays a key role during fetal lung development and may be involved in lung fibrogenesis. We determined the expression pattern of several Sonic hedgehog (SHH) pathway members in normal and IPF human lung biopsies and primary fibroblasts. The effect of hedgehog pathway inhibition was assayed by lung fibroblast proliferation and differentiation with and without transforming growth factor (TGF)-β1. We showed that the hedgehog pathway was reactivated in the IPF lung. Importantly, we deciphered the cross talk between the hedgehog and TGF-β pathway in human lung fibroblasts. TGF-β1 modulated the expression of key components of the hedgehog pathway independent of Smoothened, the obligatory signal transducer of the pathway. Smoothened was required for TGF-β1-induced myofibroblastic differentiation of control fibroblasts, but differentiation of IPF fibroblasts was partially resistant to Smoothened inhibition. Furthermore, functional hedgehog pathway machinery from the primary cilium, as well as GLI-dependent transcription in the nucleus, was required for the TGF-β1 effects on normal and IPF fibroblasts during myofibroblastic differentiation. These data identify the GLI transcription factors as potential therapeutic targets in lung fibrosis.

Radiation-induced ICAM-1 expression via TGF-β1 pathway on human umbilical vein endothelial cells; comparison between X-ray and carbon-ion beam irradiation

Adhesion of inflammatory cells to endothelial cells is considered to be involved in the process of radiation-induced damage and fibrosis. Intercellular adhesion molecule-1 (ICAM-1) and transforming growth factor-beta1 (TGF-β1) are thought to play important roles in this process. In this study, radiation-induced ICAM-1 expression on endothelial cells was investigated with the use of an inhibitor of TGF-β1 receptor kinase (SB431542) and the effects of X-ray and carbon-ion beam were compared. Cell cultures of human umbilical vein endothelial cells (HUVE cells) were incubated with TGF-β1 and irradiated with 140 KV X-ray. Next, HUVE cells were irradiated with X-ray and 220 MeV carbon-ion beam with or without SB431542. Immunofluorescence analysis was used to quantify ICAM-1 expression. The expression of ICAM-1 on HUVE cells was significantly increased by the stimulation with TGF-β1. Expression of ICAM-1 was increased by X-ray and carbon-ion beam irradiation and decreased significantly with SB431542 after both irradiations. The expression of ICAM-1 by 2 Gy of carbon-ion beam irradiation was 6.7 fold higher than that of non-irradiated cells, while 5 Gy of X-ray irradiation increased the expression of ICAM-1 by 2.5 fold. According to ICAM-1 expression, the effect of carbon-ion beam irradiation was about 2.2, 4.4 and 5.0 times greater than that of the same doses of X-ray irradiation (1, 2 and 5 Gy, respectively). The present results suggested that radiation-induced ICAM-1 expression on HUVE cells was, at least partially, regulated by TGF-β1. Carbon-ion beam induced significantly higher ICAM-1 expression than X-ray.

Hepatocyte growth factor in lung repair and pulmonary fibrosis

Pulmonary remodeling is characterized by the permanent and progressive loss of the normal alveolar architecture, especially the loss of alveolar epithelial and endothelial cells, persistent proliferation of activated fibroblasts, or myofibroblasts, and alteration of extracellular matrix. Hepatocyte growth factor (HGF) is a pleiotropic factor, which induces cellular motility, survival, proliferation, and morphogenesis, depending upon the cell type. In the adult, HGF has been demonstrated to play a critical role in tissue repair, including in the lung. Administration of HGF protein or ectopic expression of HGF has been demonstrated in animal models of pulmonary fibrosis to induce normal tissue repair and to prevent fibrotic remodeling. HGF-induced inhibition of fibrotic remodeling may occur via multiple direct and indirect mechanisms including the induction of cell survival and proliferation of pulmonary epithelial and endothelial cells, and the reduction of myofibroblast accumulation.

Hepatocyte growth factor in lung repair and pulmonary fibrosis

Pulmonary remodeling is characterized by the permanent and progressive loss of the normal alveolar architecture, especially the loss of alveolar epithelial and endothelial cells, persistent proliferation of activated fibroblasts, or myofibroblasts, and alteration of extracellular matrix. Hepatocyte growth factor (HGF) is a pleiotropic factor, which induces cellular motility, survival, proliferation, and morphogenesis, depending upon the cell type. In the adult, HGF has been demonstrated to play a critical role in tissue repair, including in the lung. Administration of HGF protein or ectopic expression of HGF has been demonstrated in animal models of pulmonary fibrosis to induce normal tissue repair and to prevent fibrotic remodeling. HGF-induced inhibition of fibrotic remodeling may occur via multiple direct and indirect mechanisms including the induction of cell survival and proliferation of pulmonary epithelial and endothelial cells, and the reduction of myofibroblast accumulation.

Activation of vascular endothelial growth factor receptor 2 in a cellular model of loricrin keratoderma

Loricrin is a major constituent of the epidermal cornified cell envelope. Recently, heterozygous loricrin gene mutations have been identified in two dominantly inherited skin diseases, Vohwinkel syndrome with ichthyosis and progressive symmetric erythrokeratoderma, collectively termed loricrin keratoderma. We generated stable HaCaT cell lines that express wild-type (WT) loricrin and a mutant form found in Vohwinkel syndrome with ichthyosis, using an ecdysone-inducible promoter system. The cells expressing the mutant loricrin grew more rapidly than those expressing WT loricrin after induction for 5 days. Confocal immunofluorescence microscopy revealed that phospho-Akt occurred in the nucleolus where the mutant loricrin was also located. The level of activity of Akt kinase was about nine times higher in cells with the mutant than in those with WT loricrin. ERK1/2, the epidermal growth factor receptor, vascular endothelial growth factor (VEGF) receptor 2 and Stat3 were all phosphorylated in cells with the mutant loricrin. The docking proteins, Gab1 and c-Cbl, were also tyrosine-phosphorylated in these cells. Furthermore, chromatin immunoprecipitation assays showed that Stat3 protein bound to the VEGF promoter in cells with the mutant. Thus, this study suggests that VEGF release and the subsequent activation of VEGF receptor 2 link loricrin gene mutations to rapid cell proliferation in a cellular model of loricrin keratoderma.

Innovative approaches to the therapy of fibrosis

PURPOSE OF REVIEW

The lung in systemic sclerosis (scleroderma) is susceptible to fibrosis and the ensuing respiratory insufficiency contributes to significant morbidity and mortality in this disease. The lack of effective therapies for pulmonary fibrosis has spurred a re-evaluation of pathobiological paradigms and therapeutic strategies in scleroderma-associated interstitial lung disease and in idiopathic pulmonary fibrosis. The purpose of this review is to examine emerging new therapeutic targets that modulate pro-fibrotic phenotypes of tissue-resident cells and the associated aberrant tissue remodeling responses in fibrotic disorders.

RECENT FINDINGS

Progressive forms of tissue fibrosis, including scleroderma, are characterized by an accumulation of activated mesenchymal cells and their secreted extracellular matrix proteins in association with dysrepair of epithelial and endothelial cells. Recent studies suggest that emergence of cellular phenotypes that perpetuate loss of cellular homeostasis is characteristic of many fibrosis-related clinical syndromes.

SUMMARY

Therapeutic strategies that modulate the fate/phenotype of reparative structural cells, including epithelial, endothelial, and mesenchymal cells, offer new opportunities for the development of more effective drugs for the treatment of fibrosis.

Identification of keratinocyte growth factor as a target of microRNA-155 in lung fibroblasts: implication in epithelial-mesenchymal interactions

BACKGROUND

Epithelial-mesenchymal interactions are critical in regulating many aspects of vertebrate embryo development, and for the maintenance of homeostatic equilibrium in adult tissues. The interactions between epithelium and mesenchyme are believed to be mediated by paracrine signals such as cytokines and extracellular matrix components secreted from fibroblasts that affect adjacent epithelia. In this study, we sought to identify the repertoire of microRNAs (miRNAs) in normal lung human fibroblasts and their potential regulation by the cytokines TNF-alpha, IL-1beta and TGF-beta.

METHODOLOGY/PRINCIPAL FINDINGS

MiR-155 was significantly induced by inflammatory cytokines TNF-alpha and IL-1beta while it was down-regulated by TGF-beta. Ectopic expression of miR-155 in human fibroblasts induced modulation of a large set of genes related to "cell to cell signalling", "cell morphology" and "cellular movement". This was consistent with an induction of caspase-3 activity and with an increase in cell migration in fibroblasts tranfected with miR-155. Using different miRNA bioinformatic target prediction tools, we found a specific enrichment for miR-155 predicted targets among the population of down-regulated transcripts. Among fibroblast-selective targets, one interesting hit was keratinocyte growth factor (KGF, FGF-7), a member of the fibroblast growth factor (FGF) family, which owns two potential binding sites for miR-155 in its 3'-UTR. Luciferase assays experimentally validated that miR-155 can efficiently target KGF 3'-UTR. Site-directed mutagenesis revealed that only one out of the 2 potential sites was truly functional. Functional in vitro assays experimentally validated that miR-155 can efficiently target KGF 3'-UTR. Furthermore, in vivo experiments using a mouse model of lung fibrosis showed that miR-155 expression level was correlated with the degree of lung fibrosis.

CONCLUSIONS/SIGNIFICANCE

Our results strongly suggest a physiological function of miR-155 in lung fibroblasts. Altogether, this study implicates this miRNA in the regulation by mesenchymal cells of surrounding lung epithelium, making it a potential key player during tissue injury.

Overexpression of fibroblast growth factor-10 during both inflammatory and fibrotic phases attenuates bleomycin-induced pulmonary fibrosis in mice

RATIONALE

Fibroblast growth factor-10 (FGF10) controls survival, proliferation, and differentiation of distal-alveolar epithelial progenitor cells during lung development.

OBJECTIVES

To test for the protective and regenerative effect of Fgf10 overexpression in a bleomycin-induced mouse model of pulmonary inflammation and fibrosis.

METHODS

In SP-C-rtTA; tet(O)Fgf10 double-transgenic mice, lung fibrosis was induced in 2-month-old transgenic mice by subcutaneous delivery of bleomycin (BLM), using an osmotic minipump for 1 week. Exogenous Fgf10 expression in the alveolar epithelium was induced for 7 days with doxycycline during the first, second, and third weeks after bleomycin pump implantation, and lungs were examined at 28 days.

MEASUREMENTS AND MAIN RESULTS

Fgf10 overexpression during Week 1 (inflammatory phase) resulted in increased survival and attenuated lung fibrosis score and collagen deposition. In these Fgf10-overexpressing mice, an increase in regulatory T cells and a reduction in both transforming growth factor-beta(1) and matrix metalloproteinase-2 activity were observed in bronchoalveolar lavage fluids whereas the number of surfactant protein C (SP-C)-positive, alveolar epithelial type II cells (AEC2) was markedly elevated. Analysis of SP-C and TUNEL (terminal deoxynucleotidyltransferase dUTP nick end labeling) double-positive cells and isolation of AEC2 from lungs overexpressing Fgf10 demonstrated increased AEC2 survival. Expression of Fgf10 during Weeks 2 and 3 (fibrotic phase) showed significant attenuation of the lung fibrosis score and collagen deposition.

CONCLUSIONS

In the bleomycin model of lung inflammation and fibrosis, Fgf10 overexpression during both the inflammatory and fibrotic phases results in a greatly reduced extent of lung fibrosis, suggesting that FGF10 may be useful as a novel approach to the treatment of pulmonary fibrosis.

Dendritic Cells Accumulate in Human Fibrotic Interstitial Lung Disease

RATIONALE

There is growing evidence that resident cells, such as fibroblasts and epithelial cells, can drive the persistent accumulation of dendritic cells (DCs) in chronically inflamed tissue, leading to the organization and the maintenance of ectopic lymphoid aggregates. This phenomenon, occurring through a chemokine-mediated retention mechanism, has been documented in various disorders, but not in fibrotic interstitial lung disorders in which the presence of organized lymphoid follicles has been documented.

OBJECTIVES

To characterize the distribution of DCs in fibrotic lung, and to analyze the expression of the main chemokines known to regulate DC recruitment.

METHODS

Lung resection tissue (lungs with idiopathic pulmonary fibrosis; n = 12; lungs with nonspecific interstitial pneumonia, n = 5; control lungs, n = 5) was snap-frozen for subsequent immunohistochemical techniques on serial sections and reverse transcriptase-polymerase chain reaction analysis.

MEASUREMENTS AND MAIN RESULTS

Results were similar in idiopathic pulmonary fibrosis and nonspecific interstitial pneumonia lungs, which were heavily infiltrated by immature DCs in established fibrosis and in areas of epithelial hyperplasia. Altered epithelial cells and fibroblasts, particularly in fibroblastic foci, frankly expressed all chemokines (CCL19, CCL20, CCL22, and CXCL12) susceptible to favor the recruitment of immune cells. Lymphoid follicles were infiltrated by maturing DCs, which could originate from the pool of DCs accumulating in their vicinity.

CONCLUSIONS

These findings suggest that resident cells in pulmonary fibrosis can sustain chronic inflammation by driving the accumulation of DCs with the potential to mature locally within ectopic lymphoid follicles. Future strategies should consider DCs or chemokines as therapeutic targets in the treatment of pulmonary fibrosis.

Mechanisms of tissue inhibitor of metalloproteinase 1 augmentation by IL-13 on TGF-beta 1-stimulated primary human fibroblasts

BACKGROUND

TGF-beta induces expression of tissue inhibitor of metalloproteinase 1 (TIMP-1), a potent inhibitor of matrix metalloproteinases that controls extracellular matrix metabolism and deposition. IL-13 alone does not induce TIMP-1, but in combination with TGF-beta it augments TIMP-1 expression. Although these interactions have implications for remodeling in asthma, little is understood regarding the mechanisms controlling TIMP-1 product.

OBJECTIVE

To explore the role of Smads and mitogen-activated protein kinase kinase (MEK)-extracellular signal-regulated kinase (ERK) in the TIMP-1 augmentation by IL-13+TGF-beta1 in primary human airway fibroblasts.

METHODS

Real-time PCR, Western blot, ELISA, and transient transfection were used to evaluate the mechanisms of TIMP-1 augmentation.

RESULTS

IL-13 enhanced TGF-beta1-induced Smad-2 and Smad-3 phosphorylation, transient transfection with dominant-negative Smad-2 or Smad-3 decreased TIMP-1 mRNA expression in the presence of TGF-beta1 and IL-13+TGF-beta1 through inhibition of Smad-2 or Smad-3 phosphorylation. ERK phosphorylation was increased by IL-13 and IL-13+TGF-beta1. MEK-ERK inhibition decreased TIMP-1 mRNA/protein to a greater degree after IL-13+TGF-beta1 stimulation versus TGF-beta1 alone. MEK-ERK inhibition also significantly increased Akt phosphorylation under all conditions and decreased Smad-3 phosphorylation in the presence of IL-13+TGF-beta1. In contrast, phosphoinositide-3 kinase-Akt inhibition increased phosphorylation of ERK and Smads, leading to increased TIMP-1.

CONCLUSION

These results indicate that IL-13 augments TGF-beta1-induced TIMP-1 expression through increased Smad phosphorylation. These increases occur as TGF-beta1 downregulates IL-13-induced phosphoinositide-3 kinase activation while leaving the positive effect of IL-13-induced ERK on Smad signaling.

CLINICAL IMPLICATIONS

This augmentation of TGF-beta1-induced TIMP-1 by IL-13 could contribute to the fibrosis and airway remodeling seen in the presence of T(H)2 inflammation in asthma.

Epithelial-mesenchymal interactions in pulmonary fibrosis

Pulmonary fibrosis represents the sequelae of a variety of acute and chronic lung injuries of known and unknown etiologies. Tissue specimens obtained from patients with pulmonary fibrosis, regardless of the etiology, consistently show evidence of an ongoing wound-repair response. Epithelial-mesenchymal interactions have critical roles in normal lung development, tissue repair processes, and fibrosis. Current hypotheses propose that dysregulated function of, and impaired communication between, epithelial and mesenchymal cells prevent resolution of the wound-repair response and contribute to the pathobiology of pulmonary fibrosis. This hypothesis is supported by abundant evidence from patients, animal models, and cell-culture studies demonstrating abnormalities in epithelial cell and mesenchymal cell activities including proliferation, differentiation, and survival. This article reviews the aberrant epithelial and mesenchymal cellular phenotypes found in the context of pulmonary fibrosis and discusses the mechanisms that perpetuate these cellular phenotypes.

Defect of Pro-Hepatocyte Growth Factor Activation by Fibroblasts in Idiopathic Pulmonary Fibrosis

RATIONALE AND OBJECTIVES

Hepatocyte growth factor (HGF) protects against lung fibrosis in several animal models. Pro-HGF activation to HGF is subjected to regulation by its activator (HGFA), a serine protease, and HGFA-specific inhibitors (HAI-1 and HAI-2). Our hypothesis was that fibroblasts from patients with idiopathic pulmonary fibrosis (IPF) had an altered capacity to activate pro-HGF in vitro compared with control fibroblasts.

METHODS

We measured the kinetics of pro-HGF activation in human lung fibroblasts from control subjects and from patients with IPF by Western blot. HGFA, HAI-1, and HAI-2 expression was evaluated by immunohistochemistry, RNA protection assay, and Western blot. We evaluated the effect of TGF-beta(1) and PGE(2) on pro-HGF activation and HGFA, HAI-1, and HAI-2 expression.

MAIN RESULTS

Lung fibroblasts activated pro-HGF in vitro. Pro-HGF activation was inhibited by serine protease inhibitors, by an anti-HGFA antibody, as well as by HAI-1 and HAI-2. Pro-HGF activation by IPF fibroblasts was reduced compared with control fibroblasts. In IPF fibroblasts, HGFA expression was lower and HAI-1 and HAI-2 expression was higher compared with control fibroblasts. PGE(2) stimulated pro-HGF activation through increased expression of HGFA and decreased expression of its inhibitor HAI-2. In contrast, TGF-beta(1) reduced the ability of lung fibroblasts to activate pro-HGF through decreased expression of HGFA and increased expression of its inhibitors.

CONCLUSIONS

IPF fibroblasts have a low capacity to activate pro-HGF in vitro via a low level of HGFA expression and high levels of HAI-1 and HAI-2 expression, and PGE(2) is able to partially correct this defect.

Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and usually fatal pulmonary disease for which there are no proven drug therapies. Anti-inflammatory and immunosuppressive agents have been largely ineffective. The precise relationship of IPF to other idiopathic interstitial pneumonias (IIPs) is not known, despite the observation that different histopathologic patterns of IIP may coexist in the same patient. We propose that these different histopathologic 'reaction' patterns may be determined by complex interactions between host and environmental factors that alter the local alveolar milieu. Recent paradigms in IPF pathogenesis have focused on dysregulated epithelial-mesenchymal interactions, an imbalance in T(H)1/T(H)2 cytokine profile and potential roles for aberrant angiogenesis. In this review, we discuss these evolving concepts in disease pathogenesis and emerging therapies designed to target pro-fibrogenic pathways in IPF.