Profibrotic TGFβ responses require the cooperative action of PDGF and ErbB receptor tyrosine kinases

Interstitial Lung Diseases and Non-Small Cell Lung Cancer: Particularities in Pathogenesis and Expression of Driver Mutations

INTRODUCTION

Interstitial lung diseases are a varied group of diseases associated with chronic inflammation and fibrosis. With the emerging and current treatment options, survival rates have vastly improved. Having in mind that the most common type is idiopathic pulmonary fibrosis and that a significant proportion of these patients will develop lung cancer as the disease progresses, prompt diagnosis and personalized treatment of these patients are fundamental.

SCOPE AND METHODS

The scope of this review is to identify and characterize molecular and pathogenetic pathways that can interconnect Interstitial Lung Diseases and lung cancer, especially driver mutations in patients with NSCLC, and to highlight new and emerging treatment options in that view.

RESULTS

Common pathogenetic pathways have been identified in sites of chronic inflammation in patients with interstitial lung diseases and lung cancer. Of note, the expression of driver mutations in EGFR, BRAF, and KRAS G12C in patients with NSCLC with concurrent interstitial lung disease is vastly different compared to those patients with NSCLC without Interstitial Lung Disease.

CONCLUSIONS

NSCLC in patients with Interstitial Lung Disease is a challenging diagnostic and clinical entity, and a personalized medicine approach is fundamental to improving survival and quality of life. Newer anti-fibrotic medications have improved survival in IPF/ILD patients; thus, the incidence of lung cancer is going to vastly increase in the next 5-10 years.

A miniaturized screening platform to identify novel regulators of extracellular matrix alignment

Extracellular matrix alignment contributes to metastasis in a number of cancers and is a known prognostic stromal factor; however, the mechanisms controlling matrix organization remain unclear. Cancer-associated fibroblasts (CAF) play a critical role in this process, particularly via matrix production and modulation of key signaling pathways controlling cell adhesion and contractility. Stroma normalization, as opposed to elimination, is a highly sought strategy, and screening for drugs that effectively alter extracellular matrix (ECM) alignment is a practical way to identify novel CAF-normalizing targets that modulate ECM organization. To meet this need, we developed a novel high-throughput screening platform in which fibroblast-derived matrices were produced in 384-well plates, imaged with automated confocal microscopy, and analyzed using a customized MATLAB script. This platform is a technical advance because it miniaturizes the assay, eliminates costly and time-consuming experimental steps, and streamlines data acquisition and analysis to enable high-throughput screening applications. As a proof of concept, this platform was used to screen a kinase inhibitor library to identify modulators of matrix alignment. A number of novel potential regulators were identified, including several receptor tyrosine kinases (c-MET, tropomyosin receptor kinase 1 (NTRK1), HER2/ERBB2) and the serine/threonine kinases protein kinase A, C, and G (PKA, PKC, and PKG). The expression of these regulators was analyzed in publicly available patient datasets to examine the association between stromal gene expression and patient outcomes.

The EGFR/ErbB inhibitor neratinib modifies the neutrophil phosphoproteome and promotes apoptosis and clearance by airway macrophages

Dysregulated neutrophilic inflammation can be highly destructive in chronic inflammatory diseases due to prolonged neutrophil lifespan and continual release of histotoxic mediators in inflamed tissues. Therapeutic induction of neutrophil apoptosis, an immunologically silent form of cell death, may be beneficial in these diseases, provided that the apoptotic neutrophils are efficiently cleared from the tissue. Previous research in our group identified ErbB inhibitors as able to induce neutrophil apoptosis and reduce neutrophilic inflammation both in vitro and in vivo. Here, we extend that work using a clinical ErbB inhibitor, neratinib, which has the potential to be repurposed in inflammatory diseases. We show that neratinib reduces neutrophilic migration o an inflammatory site in zebrafish larvae. Neratinib upregulates efferocytosis and reduces the number of persisting neutrophil corpses in mouse models of acute, but not chronic, lung injury, suggesting that the drug may have therapeutic benefits in acute inflammatory settings. Phosphoproteomic analysis of human neutrophils shows that neratinib modifies the phosphorylation of proteins regulating apoptosis, migration, and efferocytosis. This work identifies a potential mechanism for neratinib in treating acute lung inflammation by upregulating the clearance of dead neutrophils and, through examination of the neutrophil phosphoproteome, provides important insights into the mechanisms by which this may be occurring.

Protective effect of ebselen on bleomycin-induced lung fibrosis: analysis of the molecular mechanism of lung fibrosis mediated by oxidized diacylglycerol

The molecular mechanisms underlying the development of pulmonary fibrosis remain unknown, and effective treatments have not yet been developed. It has been shown that oxidative stress is involved in lung fibrosis. Oxidized diacylglycerol (DAG) produced by oxidative stress is thought to play an important role in lung fibrosis. This study assessed the effect of oxidized DAG in an animal model of pulmonary fibrosis induced by aspiration of bleomycin (BLM) into the lungs. The inhibitory effect of ebselen on pulmonary fibrosis was also investigated. In lung fibrotic tissue induced by BLM, an increase in lipid peroxides and collagen accumulation was observed. Moreover, the levels of oxidized DAG, which has strong protein kinase C (PKC) activation activity, were significantly increased over time following the administration of BLM. Western blotting showed that phosphorylation of PKCα and δ isoforms was increased by BLM. Oral administration of ebselen significantly suppressed the increase in oxidized DAG induced by BLM and improved lung fibrosis. PKCα and δ phosphorylation were also significantly inhibited. The mRNA expression of α-smooth muscle actin and collagen I (marker molecules for fibrosis), as well as the production of transforming growth factor-β and tumor necrosis factor-α(a potentially important factor in the fibrotic process), were increased by BLM and significantly decreased by ebselen. The administration of BLM may induce lipid peroxidation in lung tissue, while the oxidized DAG produced by BLM may induce overactivation of PKCα and δ, resulting in the induction of lung fibrosis.

EGFR Signaling in Lung Fibrosis

In this review article, we will first provide a brief overview of the ErbB receptor-ligand system and its importance in developmental and physiological processes. We will then review the literature regarding the role of ErbB receptors and their ligands in the maladaptive remodeling of lung tissue, with special emphasis on idiopathic pulmonary fibrosis (IPF). Here we will focus on the pathways and cellular processes contributing to epithelial-mesenchymal miscommunication seen in this pathology. We will also provide an overview of the in vivo studies addressing the efficacy of different ErbB signaling inhibitors in experimental models of lung injury and highlight how such studies may contribute to our understanding of ErbB biology in the lung. Finally, we will discuss what we learned from clinical applications of the ErbB1 signaling inhibitors in cancer in order to advance clinical trials in IPF.

Smad7 effects on TGF-β and ErbB2 restrain myofibroblast activation and protect from postinfarction heart failure

Repair of the infarcted heart requires TGF-β/Smad3 signaling in cardiac myofibroblasts. However, TGF-β-driven myofibroblast activation needs to be tightly regulated in order to prevent excessive fibrosis and adverse remodeling that may precipitate heart failure. We hypothesized that induction of the inhibitory Smad, Smad7, may restrain infarct myofibroblast activation, and we examined the molecular mechanisms of Smad7 actions. In a mouse model of nonreperfused infarction, Smad3 activation triggered Smad7 synthesis in α-SMA+ infarct myofibroblasts, but not in α-SMA-PDGFRα+ fibroblasts. Myofibroblast-specific Smad7 loss increased heart failure-related mortality, worsened dysfunction, and accentuated fibrosis in the infarct border zone and in the papillary muscles. Smad7 attenuated myofibroblast activation and reduced synthesis of structural and matricellular extracellular matrix proteins. Smad7 effects on TGF-β cascades involved deactivation of Smad2/3 and non-Smad pathways, without any effects on TGF-β receptor activity. Unbiased transcriptomic and proteomic analysis identified receptor tyrosine kinase signaling as a major target of Smad7. Smad7 interacted with ErbB2 in a TGF-β-independent manner and restrained ErbB1/ErbB2 activation, suppressing fibroblast expression of fibrogenic proteases, integrins, and CD44. Smad7 induction in myofibroblasts serves as an endogenous TGF-β-induced negative feedback mechanism that inhibits postinfarction fibrosis by restraining Smad-dependent and Smad-independent TGF-β responses, and by suppressing TGF-β-independent fibrogenic actions of ErbB2.

Fibrotic Idiopathic Interstitial Lung Disease: The Molecular and Cellular Key Players

Interstitial lung diseases (ILDs) that are known as diffuse parenchymal lung diseases (DPLDs) lead to the damage of alveolar epithelium and lung parenchyma, culminating in inflammation and widespread fibrosis. ILDs that account for more than 200 different pathologies can be divided into two groups: ILDs that have a known cause and those where the cause is unknown, classified as idiopathic interstitial pneumonia (IIP). IIPs include idiopathic pulmonary fibrosis (IPF), non-specific interstitial pneumonia (NSIP), cryptogenic organizing pneumonia (COP) known also as bronchiolitis obliterans organizing pneumonia (BOOP), acute interstitial pneumonia (AIP), desquamative interstitial pneumonia (DIP), respiratory bronchiolitis-associated interstitial lung disease (RB-ILD), and lymphocytic interstitial pneumonia (LIP). In this review, our aim is to describe the pathogenic mechanisms that lead to the onset and progression of the different IIPs, starting from IPF as the most studied, in order to find both the common and standalone molecular and cellular key players among them. Finally, a deeper molecular and cellular characterization of different interstitial lung diseases without a known cause would contribute to giving a more accurate diagnosis to the patients, which would translate to a more effective treatment decision.

Dissecting the Role of Mesenchymal Stem Cells in Idiopathic Pulmonary Fibrosis: Cause or Solution

Idiopathic pulmonary fibrosis (IPF) is one of the most aggressive forms of idiopathic interstitial pneumonias, characterized by chronic and progressive fibrosis subverting the lung's architecture, pulmonary functional decline, progressive respiratory failure, and high mortality (median survival 3 years after diagnosis). Among the mechanisms associated with disease onset and progression, it has been hypothesized that IPF lungs might be affected either by a regenerative deficit of the alveolar epithelium or by a dysregulation of repair mechanisms in response to alveolar and vascular damage. This latter might be related to the progressive dysfunction and exhaustion of the resident stem cells together with a process of cellular and tissue senescence. The role of endogenous mesenchymal stromal/stem cells (MSCs) resident in the lung in the homeostasis of these mechanisms is still a matter of debate. Although endogenous MSCs may play a critical role in lung repair, they are also involved in cellular senescence and tissue ageing processes with loss of lung regenerative potential. In addition, MSCs have immunomodulatory properties and can secrete anti-fibrotic factors. Thus, MSCs obtained from other sources administered systemically or directly into the lung have been investigated for lung epithelial repair and have been explored as a potential therapy for the treatment of lung diseases including IPF. Given these multiple potential roles of MSCs, this review aims both at elucidating the role of resident lung MSCs in IPF pathogenesis and the role of administered MSCs from other sources for potential IPF therapies.

ZNF416 is a pivotal transcriptional regulator of fibroblast mechanoactivation

Matrix stiffness is a central regulator of fibroblast function. However, the transcriptional mechanisms linking matrix stiffness to changes in fibroblast phenotype are incompletely understood. Here, we evaluated the effect of matrix stiffness on genome-wide chromatin accessibility in freshly isolated lung fibroblasts using ATAC-seq. We found higher matrix stiffness profoundly increased global chromatin accessibility relative to lower matrix stiffness, and these alterations were in close genomic proximity to known profibrotic gene programs. Motif analysis of these regulated genomic loci identified ZNF416 as a putative mediator of fibroblast stiffness responses. Genome occupancy analysis using ChIP-seq confirmed that ZNF416 occupies a broad range of genes implicated in fibroblast activation and tissue fibrosis, with relatively little overlap in genomic occupancy with other mechanoresponsive and profibrotic transcriptional regulators. Using loss- and gain-of-function studies, we demonstrated that ZNF416 plays a critical role in fibroblast proliferation, extracellular matrix synthesis, and contractile function. Together, these observations identify ZNF416 as novel mechano-activated transcriptional regulator of fibroblast biology.

Cross-talk between Janus kinase-signal transducer and activator of transcription pathway and transforming growth factor beta pathways and increased collagen1A1 production in uterine leiomyoma cells

OBJECTIVE

To characterize the potential interaction between interleukin-6 (IL6), Janus kinase (JAK)-signal transducer and activator of transcription (STAT)-3 (JAK/STAT3) pathway, and Transforming growth factor beta (TGFβ)-3 , and to determine whether such cross-talk was a contributing factor in the dysregulation of type I collagen production in leiomyomas.

DESIGN

Laboratory study.

SETTING

University research laboratory.

PATIENTS

None.

INTERVENTIONS

Exposure of leiomyoma and myometrial cell lines to IL6 and STAT3 activators/inhibitors. Western immunoblot analysis and immunohistochemistry.

MAIN OUTCOME MEASURES

Expression of STAT3, pSTAT3, SOCS3, COL1A1, and TGFb3.

RESULTS

We observed that IL6 increased pSTAT3 as well as collagen1A1 in uterine leiomyoma cells. Direct activation of the JAK/STAT3 pathway increased collagen1A1 production in leiomyoma cells, whereas inhibition of the pathway significantly decreased collagen1A1 production. We further observed that modulation of the JAK/STAT3 pathway also increased the expression of TGFβ3 protein. Leiomyoma cells exposed to TGFβ3 demonstrated a significant decrease in pSTAT3 protein. Myometrial cells demonstrated a less sensitive response to STAT3 modulation and collagen production.

CONCLUSION

Cross-talk between the TGFβ pathway and JAK/STAT3 pathway contributes to the fibrotic nature of uterine leiomyomas.

Exposed CendR Domain in Homing Peptide Yields Skin-Targeted Therapeutic in Epidermolysis Bullosa

Systemic skin-selective therapeutics would be a major advancement in the treatment of diseases affecting the entire skin, such as recessive dystrophic epidermolysis bullosa (RDEB), which is caused by mutations in the COL7A1 gene and manifests in transforming growth factor-β (TGF-β)-driven fibrosis and malignant transformation. Homing peptides containing a C-terminal R/KXXR/K motif (C-end rule [CendR] sequence) activate an extravasation and tissue penetration pathway for tumor-specific drug delivery. We have previously described a homing peptide CRKDKC (CRK) that contains a cryptic CendR motif and homes to angiogenic blood vessels in wounds and tumors, but it cannot penetrate cells or tissues. In this study, we demonstrate that removal of the cysteine from CRK to expose the CendR sequence confers the peptide novel ability to home to normal skin. Fusion of the truncated CRK (tCRK) peptide to the C terminus of an extracellular matrix protein decorin (DCN), a natural TGF-β inhibitor, resulted in a skin-homing therapeutic molecule (DCN-tCRK). Systemic DCN-tCRK administration in RDEB mice led to inhibition of TGF-β signaling in the skin and significant improvement in the survival of RDEB mice. These results suggest that DCN-tCRK has the potential to be utilized as a novel therapeutic compound for the treatment of dermatological diseases such as RDEB.

New insights into the pathogenesis of Peyronie's disease: A narrative review

Peyronie's disease (PD) is a benign, progressive fibrotic disorder characterized by scar or plaques within the tunica albuginea (TA) of the penis. This study provides new insights into the pathogenesis of PD based on data from different studies regarding the roles of cytokines, cell signaling pathways, biochemical mechanisms, genetic factors responsible for fibrogenesis. A growing body of literature has shown that PD is a chronically impaired, localized, wound healing process within the TA and the Smith space. It is caused by the influence of different pathological stimuli, most often the effects of mechanical stress during sexual intercourse in genetically sensitive individuals with unusual anatomical TA features, imbalanced matrix metalloproteinase/tissue inhibitor of metalloproteinase (MMP/TIMP), and suppressed antioxidant systems during chronic inflammation. Other intracellular signal cascades are activated during fibrosis along with low expression levels of their negative regulators and transforming growth factor-β1 signaling. The development of multikinase agents with minimal side effects that can block several signal cell pathways would significantly improve fibrosis in PD tissues by acting on common downstream mediators.

SIRT7-mediated modulation of glutaminase 1 regulates TGF-β-induced pulmonary fibrosis

In the current work we show that the profibrotic actions of TGF-β are mediated, at least in part, through a metabolic maladaptation in glutamine metabolism and how the inhibition of glutaminase 1 (GLS1) reverses pulmonary fibrosis. GLS1 was found to be highly expressed in fibrotic vs normal lung fibroblasts and the expression of profibrotic targets, cell migration, and soft agar colony formation stimulated by TGF-β required GLS1 activity. Moreover, knockdown of SMAD2 or SMAD3 as well as inhibition of PI3K, mTORC2, and PDGFR abrogated the induction of GLS1 by TGF-β. We further demonstrated that the NAD-dependent protein deacetylase, SIRT7, and the FOXO4 transcription factor acted as endogenous brakes for GLS1 expression, which are inhibited by TGF-β. Lastly, administration of the GLS1 inhibitor CB-839 attenuated bleomycin-induced pulmonary fibrosis. Our study points to an exciting and unexplored connection between epigenetic and transcriptional processes that regulate glutamine metabolism and fibrotic development in a TGF-β-dependent manner.

IPF pathogenesis is dependent upon TGFβ induction of IGF-1

Pathogenic fibrotic diseases, including idiopathic pulmonary fibrosis (IPF), have some of the worst prognoses and affect millions of people worldwide. With unclear etiology and minimally effective therapies, two-thirds of IPF patients die within 2-5 years from this progressive interstitial lung disease. Transforming Growth Factor Beta (TGFβ) and insulin-like growth factor-1 (IGF-1) are known to promote fibrosis; however, myofibroblast specific upregulation of IGF-1 in the initiation and progression of TGFβ-induced fibrogenesis and IPF have remained unexplored. To address this, the current study (1) documents the upregulation of IGF-1 via TGFβ in myofibroblasts and fibrotic lung tissue, as well as its correlation with decreased pulmonary function in advanced IPF; (2) identifies IGF-1's C1 promoter as mediating the increase in IGF-1 transcription by TGFβ in pulmonary fibroblasts; (3) determines that SMAD2 and mTOR signaling are required for TGFβ-dependent Igf-1 expression in myofibroblasts; (4) demonstrates IGF-1R activation is essential to support TGFβ-driven profibrotic myofibroblast functions and excessive wound healing; and (5) establishes the effectiveness of slowing the progression of murine lung fibrosis with the IGF-1R inhibitor OSI-906. These findings expand our knowledge of IGF-1's role as a novel fibrotic-switch, bringing us one step closer to understanding the complex biological mechanisms responsible for fibrotic diseases and developing effective therapies.

Systemically Administered, Target-Specific, Multi-Functional Therapeutic Recombinant Proteins in Regenerative Medicine

Growth factors, chemokines and cytokines guide tissue regeneration after injuries. However, their applications as recombinant proteins are almost non-existent due to the difficulty of maintaining their bioactivity in the protease-rich milieu of injured tissues in humans. Safety concerns have ruled out their systemic administration. The vascular system provides a natural platform for circumvent the limitations of the local delivery of protein-based therapeutics. Tissue selectivity in drug accumulation can be obtained as organ-specific molecular signatures exist in the blood vessels in each tissue, essentially forming a postal code system ("vascular zip codes") within the vasculature. These target-specific "vascular zip codes" can be exploited in regenerative medicine as the angiogenic blood vessels in the regenerating tissues have a unique molecular signature. The identification of vascular homing peptides capable of finding these unique "vascular zip codes" after their systemic administration provides an appealing opportunity for the target-specific delivery of therapeutics to tissue injuries. Therapeutic proteins can be "packaged" together with homing peptides by expressing them as multi-functional recombinant proteins. These multi-functional recombinant proteins provide an example how molecular engineering gives to a compound an ability to home to regenerating tissue and enhance its therapeutic potential. Regenerative medicine has been dominated by the locally applied therapeutic approaches despite these therapies are not moving to clinical medicine with success. There might be a time to change the paradigm towards systemically administered, target organ-specific therapeutic molecules in future drug discovery and development for regenerative medicine.

Hexokinase 2 couples glycolysis with the profibrotic actions of TGF-β

Metabolic dysregulation in fibroblasts is implicated in the profibrotic actions of transforming growth factor-β (TGF-β). Here, we present evidence that hexokinase 2 (HK2) is important for mediating the fibroproliferative activity of TGF-β both in vitro and in vivo. Both Smad-dependent and Smad-independent TGF-β signaling induced HK2 accumulation in murine and human lung fibroblasts through induction of the transcription factor c-Myc. Knockdown of HK2 or pharmacological inhibition of HK2 activity with Lonidamine decreased TGF-β-stimulated fibrogenic processes, including profibrotic gene expression, cell migration, colony formation, and activation of the transcription factors YAP and TAZ, with no apparent effect on cellular viability. Fibroblasts from patients with idiopathic pulmonary fibrosis (IPF) exhibited an increased abundance of HK2. In a mouse model of bleomycin-induced lung fibrosis, Lonidamine reduced the expression of genes encoding profibrotic markers (collagenΙα1, EDA-fibronectin, α smooth muscle actin, and connective tissue growth factor) and stabilized or improved lung function as assessed by measurement of peripheral blood oxygenation. These findings provide evidence of how metabolic dysregulation through HK2 can be integrated within the context of profibrotic TGF-β signaling.

Transforming growth factor beta induces fibroblasts to express and release the immunomodulatory protein PD-L1 into extracellular vesicles

Transforming growth factor-beta (TGFβ) is an enigmatic protein with various roles in healthy tissue homeostasis/development as well as the development or progression of cancer, wound healing, fibrotic disorders, and immune modulation, to name a few. As TGFβ is causal to various fibroproliferative disorders featuring localized or systemic tissue/organ fibrosis as well as the activated stroma observed in various malignancies, characterizing the pathways and players mediating its action is fundamental. In the current study, we found that TGFβ induces the expression of the immunoinhibitory molecule Programed death-ligand 1 (PD-L1) in human and murine fibroblasts in a Smad2/3- and YAP/TAZ-dependent manner. Furthermore, PD-L1 knockdown decreased the TGFβ-dependent induction of extracellular matrix proteins, including collagen Iα1 (colIα1) and alpha-smooth muscle actin (α-SMA), and cell migration/wound healing. In addition to an endogenous role for PD-L1 in profibrotic TGFβ signaling, TGFβ stimulated-human lung fibroblast-derived PD-L1 into extracellular vesicles (EVs) capable of inhibiting T cell proliferation in response to T cell receptor stimulation and mediating fibroblast cell migration. These findings provide new insights and potential targets for a variety of fibrotic and malignant diseases.

Pharmacology Study of the Multiple Angiogenesis Inhibitor RC28-E on Anti-Fibrosis in a Chemically Induced Lung Injury Model

Background: Disease-related injury in any organ triggers a complex cascade of cellular and molecular responses that culminate in tissue fibrosis, inflammation, and angiogenesis simultaneously. Multiple cell angiogenesis is an essential part of the tissue damage response, which is involved in fibrosis development. RC28-E is a novel recombinant dual decoy receptor lgG1 Fc-fusion protein that can block vascular endothelial growth factor (VEGFA), platelet-derived growth factor (PDGF), and fibroblast growth factor-2 (FGF-2) simultaneously. This protein has stepped into clinical trials (NCT03777254) for the treatment of pathological neovascularization-related diseases. Here, we report on the role of RC28-E during anti-fibrosis and its potential multitarget function in regulating fibrosis. Methods: A bleomycin-induced pulmonary fibrosis C57BL/6 mouse model was established. Hematoxylin and eosin staining (HE) and Masson staining (Masson’s) were performed to evaluate the pulmonary fibrosis based on the scoring from, Ashcroft score. Fibrosis related factors and inflammatory cytokines including HYP, α-SMA, procollagen, ICAM, IL-6, IL-1, and TNF-α were also determined at the protein and mRNA levels to characterize the fibrosis. Both mRNA and protein levels of VEGF, FGF, and transforming growth factor (TGF)-β were detected by quantitative real-time PCR (qRT-PCR) and immunohistochemical (IHC) analysis, respectively. Pulmonary fibrosis and related cytokines were re-evaluated in vivo after 3 doses of RC28-E (5 mg/kg, 15 mg/kg, and 50 mg/kg, ip. Tiw × 9) in comparison with a mono-target antagonist treatment (VEGF or FGF blocking). RC28-E attenuated the activation of TGF-β induced fibroblasts in vitro. Expression levels of α-SMA and collagen I, as well as proliferation and migration, were determined with the human skin fibroblast cell line Detroit 551 and primary murine pulmonary fibroblast cells. The mechanism of RC28-E via the TGF-β/Smad pathway was also investigated. Results: RC28-E exhibits significant anti-fibrosis effects on Idiopathic pulmonary fibrosis (IPF) in vivo. Moreover, TGF-β induced fibroblast activation in vitro via the inhibition of the TGF-β downstream Smad pathway, thus providing potential therapeutics for clinical disease-related fibrosis-like IPF as well as chemotherapy-induced fibrosis in cancer therapy.

BMP7 antagonizes proliferative vitreoretinopathy through retinal pigment epithelial fibrosis in vivo and in vitro

The major pathogenesis of proliferative vitreoretinopathy (PVR) is that retinal pigment epithelial (RPE) cells undergo epithelial-mesenchymal transition (EMT) because of disordered growth factors, such as TGF-β, in the vitreous humor. Bone morphogenetic proteins (BMPs) are pluripotent growth factors. In this study, we identified the antifibrotic activity of BMP7 in a PVR model both in vivo and in vitro. BMP7 expression was confirmed on the PVR proliferative membranes. BMP7 was down-regulated in the PVR vitreous humor and TGF-β-induced RPE cell EMT. In the in vivo studies, BMP7 injection attenuated PVR progression in the eyes of the rabbit model. Additionally, BMP7 treatment maintained RPE cell phenotypes and relieved TGF-β2-induced EMT, migration, and gel contraction in vitro. BMP7 inhibited the TGF-β2-induced up-regulation of fibronectin and α-smooth muscle actin and the down-regulation of E-cadherin and zona occludens-1 by balancing the TGF-β2/Smad2/3 and BMP7/Smad1/5/9 pathways. These findings provide direct evidence of the ability of BMP7 in PVR inhibition and the potential of BMP7 for use in PVR therapeutic intervention.-Yao, H., Ge, T., Zhang, Y., Li, M., Yang, S., Li, H., Wang, F. BMP7 antagonizes proliferative vitreoretinopathy through retinal pigment epithelial fibrosis in vivo and in vitro.

Identification of differentially expressed genes and signaling pathways using bioinformatics in interstitial lung disease due to tyrosine kinase inhibitors targeting the epidermal growth factor receptor

Interstitial lung disease (ILD) is a rare but lethal adverse effect of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) treatment. The specific mechanism of this disease is not fully understood. To systematically analyze genes associated with EGFR-TKI induced ILD, gene data of EGFR-TKI induced ILD were extracted initially using text mining, and then the intersection between genes from text mining and Gene Expression Omnibus (GEO) dataset was taken for further protein-protein interaction (PPI) analysis using String-bd database. Go ontology (GO) and pathway enrichment analysis was also conducted based on Database of Annotation, Visualization and Integrated Discovery (DAVID) platform. The PPI network generated by STRING was visualized by Cytoscape, and the topology scores, functional regions and gene annotations were analyzed using plugins of CytoNCA, molecular complex detection (MCODE) and ClueGo. 37 genes were identified as EGFR-TKI induced ILD related. Gene enrichment analysis yield 18 enriched GO terms and 12 associated pathways. A PPI network that included 199 interactions for a total of 35 genes was constructed. Ten genes were selected as hub genes using CytoNCA plugin, and four highly connected clusters were identified using MCODE plugin. GO and pathway annotation analysis for the cluster one revealed that five genes were associated with either response to dexamethasone or with lung fibrosis, including CTGF, CCL2, IGF1, EGFR and ICAM1. Our data might be useful to reveal the pathological mechanisms of EGFR-TKI induced ILD and provide evidence for the diagnosis and treatment in the future.

Fatty acid synthase is required for profibrotic TGF-β signaling

Evidence is provided that the fibroproliferative actions of TGF-β are dependent on a metabolic adaptation that sustains pathologic growth. Specifically, profibrotic TGF-β signaling is shown to require fatty acid synthase (FASN), an essential anabolic enzyme responsible for the de novo synthesis of fatty acids. With the use of pharmacologic and genetic approaches, we show that TGF-β-stimulated FASN expression is independent of Smad2/3 and is mediated via mammalian target of rapamycin complex 1. In the absence of FASN activity or protein, TGF-β-driven fibrogenic processes are reduced with no apparent toxicity. Furthermore, as increased FASN expression was also observed to correlate with the degree of lung fibrosis in bleomycin-treated mice, inhibition of FASN was examined in a murine-treatment model of pulmonary fibrosis. Remarkably, inhibition of FASN not only decreased expression of profibrotic targets, but lung function was also stabilized/improved, as assessed by peripheral blood oxygenation.-Jung, M.-Y., Kang, J.-H., Hernandez, D. M., Yin, X., Andrianifahanana, M., Wang, Y., Gonzalez-Guerrico, A., Limper, A. H., Lupu, R., Leof, E. B. Fatty acid synthase is required for profibrotic TGF-β signaling.

Myeloid cell populations and fibrogenic parameters in bleomycin- and HOCl-induced fibrosis

Mouse models resembling systemic sclerosis can be chemically induced by application of bleomycin or hypochloric acid (HOCl). To date, little is known about inflammatory cells and their potential role in scleroderma (Scl)-related fibrosis. Therefore, we compared both Scl models to define the early immune cell subsets in relation to fibrosis-related parameters. Both agents induced a significant increase in dermal thickness and collagen deposition after 4 weeks, as hallmarks of Scl. However, clinical skin thickness, densely packed, sirius red-stained collagen bundles and collagen cross-links were more pronounced in HOCl-induced Scl. In parallel, there was a significant upregulation of procollagen α1(I), α-SMA and TGF-β transcripts in HOCl animals, whereas IL-1β and MMP-13 mRNA levels were significantly increased in bleomycin-treated mice. Flow cytometric analysis of the Scl skin demonstrated an early cellular infiltrate containing mainly CD19⁺ B cells, CD4⁺ T cells, CD11c⁺ DC and CD11b⁺ myeloid cells, the latter ones being significantly more prominent after HOCl injection. Subanalysis revealed that Scl mice exhibited a significant increase of inflammatory myeloid CD11b⁺  Ly6C^low-high  CD64^low-high cells (HOCl>bleomycin). In particular, in the HOCl model, activated dermal macrophages (CCR2^low  MHCII^high ) and monocyte-derived DC (CCR2^high MHCII^high ) predominated over less activated CD11b⁺ myeloid cells. In conclusion, the two models differ in certain aspects of the murine and human scleroderma but in the HOCl model, myeloid CD11b⁺  MHCII^high cells correlate with some fibrosis-related parameters. Therefore, analysis of both models is suggested to cover a comprehensive profile of Scl symptoms but with focus on the HOCl model when the role of early myeloid immune cells will be evaluated.

Cell-penetrating peptides selectively targeting SMAD3 inhibit profibrotic TGF-β signaling

TGF-β is considered a master switch in the pathogenesis of organ fibrosis. The primary mediators of this activity are the SMAD proteins, particularly SMAD3. In the current study, we have developed a cell-penetrating peptide (CPP) conjugate of the HIV TAT protein that is fused to an aminoterminal sequence of sorting nexin 9 (SNX9), which was previously shown to bind phosphorylated SMAD3 (pSMAD3). We determined that specifically preventing the nuclear import of pSMAD3 using the TAT-SNX9 peptide inhibited profibrotic TGF-β activity in murine cells and human lung fibroblasts as well as in vivo with no demonstrable toxicity. TGF-β signaling mediated by pSMAD2, bone morphogenetic protein 4 (BMP4), EGF, or PDGF was unaffected by the TAT-SNX9 peptide. Furthermore, while the TAT-SNX9 peptide prevented TGF-β's profibrotic activity in vitro as well as in 2 murine treatment models of pulmonary fibrosis, a 3-amino acid point mutant that was unable to bind pSMAD3 proved ineffective. These findings indicate that specifically targeting pSMAD3 can ameliorate both the direct and indirect fibroproliferative actions of TGF-β.

Blocking fibrotic signaling in fibroblasts from patients with carpal tunnel syndrome

Fibrosis of the subsynovial connective tissue (SSCT) in carpal tunnel syndrome (CTS) patients is increasingly recognized as an important aspect of CTS pathophysiology. In this study, we evaluated the effect of blocking profibrotic pathways in fibroblasts from the SSCT in CTS patients. Fibroblasts were stimulated with transforming growth factor β1 (TGF-β1), and then treated either with a specific fibrosis pathway inhibitor targeting TGF-β receptor type 1 (TβRI), platelet-derived growth factor receptor (PDGFR), epidermal growth factor receptor (EGFR), or vascular endothelial growth factor receptor (VEGFR). Fibrosis array and quantitative real-time polymerase chain reaction of fibrotic genes were evaluated. Array gene expression analysis revealed significant down-regulation of multiple fibrotic genes after treatment with TβRI, PDGFR, and VEGFR inhibitors. No array fibrotic genes were significantly down-regulated with EGFR inhibition. Further gene expression analysis of known CTS fibrosis markers collagen type I A2 (Col1), collagen type III A1 (Col3), connective tissue growth factor (CTGF), and SERPINE1 showed significantly down-regulation after TβRI inhibition. In contrast, VEGFR inhibition significantly down-regulated CTGF and SERPINE1, whereas, PDGFR and EGFR inhibition significantly down-regulated Col3. Taken together the inhibition of TβRI appears to be the primary mediator of fibrotic gene expression in fibroblasts from CTS patients. TGF-β/Smad activity was further evaluated, and as expected inhibition of Smad activity was significantly down-regulated after inhibition of TβRI, but not with PDGFR, VEGFR, or EGFR inhibition. These results indicate that local therapies specifically targeting TGF-β signaling alone or in combination offer the potential of a novel local antifibrosis therapy for patients with CTS.

PHF14: an innate inhibitor against the progression of renal fibrosis following folic acid-induced kidney injury

PHF14 is a newly identified regulator of mesenchyme growth in embryonic tissues. Previous studies have shown that phf14-null mutants die just after birth due to interstitial tissue hyperplasia in major organs, including the kidneys. The aim of this study was to investigate PHF14 function in renal fibrosis. By studying the chronic kidney injury mouse model, we found that PHF14 was upregulated in fibrotic kidneys after renal insults induced by folic acid administration. Compared with wild-type mice, PHF14-null mice showed more severe renal fibrosis after pro-fibrotic stimuli. Moreover, PHF14 in rat renal fibroblasts was upregulated by transforming growth factor-β (TGF-β) stimulation; while this upregulation was inhibited when smad3 phosphorylation was blocked. A chromatin immunoprecipitation (ChIP) assay further indicated that phospho-smad3 (p-smad3) acted as a transcription factor to enhance PHF14 expression. A lack of PHF14 expression enhanced collagen I and α-smooth muscle actin (α-SMA) synthesis induced by TGF-β in vitro. PHF14 was involved in inhibition of platelet-derived growth factor (PDGF) signaling overactivation by selectively repressing PDGF receptor-α (PDGFR-α) transcription. In summary, PHF14 expression was upregulated in fibrotic models in vivo and in vitro, and the TGF-β/smad3/PHF14 pathway acted as a self-limiting mechanism in the TGF-β-dominated renal pro-fibrotic process by suppressing PDGFR-α expression.

Human Fibrotic Diseases: Current Challenges in Fibrosis Research

Human fibrotic diseases constitute a major health problem worldwide owing to the large number of affected individuals, the incomplete knowledge of the fibrotic process pathogenesis, the marked heterogeneity in their etiology and clinical manifestations, the absence of appropriate and fully validated biomarkers, and, most importantly, the current void of effective disease-modifying therapeutic agents. The fibrotic disorders encompass a wide spectrum of clinical entities including systemic fibrotic diseases such as systemic sclerosis (SSc), sclerodermatous graft vs. host disease, and nephrogenic systemic fibrosis, as well as numerous organ-specific disorders including radiation-induced fibrosis and cardiac, pulmonary, liver, and kidney fibrosis. Although their causative mechanisms are quite diverse and in several instances have remained elusive, these diseases share the common feature of an uncontrolled and progressive accumulation of fibrotic tissue in affected organs causing their dysfunction and ultimate failure. Despite the remarkable heterogeneity in the etiologic mechanisms responsible for the development of fibrotic diseases and in their clinical manifestations, numerous studies have identified activated myofibroblasts as the common cellular element ultimately responsible for the replacement of normal tissues with nonfunctional fibrotic tissue. Critical signaling cascades, initiated primarily by transforming growth factor-β (TGF-β), but also involving numerous cytokines and signaling molecules which stimulate profibrotic reactions in myofibroblasts, offer potential therapeutic targets. Here, we briefly review the current knowledge of the molecular mechanisms involved in the development of tissue fibrosis and point out some of the most important challenges to research in the fibrotic diseases and to the development of effective therapeutic approaches for this often fatal group of disorders. Efforts to further clarify the complex pathogenetic mechanisms of the fibrotic process should be encouraged to attain the elusive goal of developing effective therapies for these serious, untreatable, and often fatal disorders.

Cardiopulmonary and histological characterization of an acute rat lung injury model demonstrating safety of mesenchymal stromal cell infusion

BACKGROUND AIMS

In the field of cellular therapy, potential cell entrapment in the lungs following intravenous administration in a compromised or injured pulmonary system is an important concern that requires further investigation. We developed a rat model of inflammatory and fibrotic lung disease to mimic the human clinical condition of obliterative bronchiolitis (OB) and evaluate the safety of intravenous infusion of mesenchymal stromal cells (MSCs). This model was used to obtain appropriate safety information and functional characterization to support the translation of an ex vivo-generated cellular product into human clinical trials. To overcome spontaneous recovery and size limitations associated with current animal models, we used a novel multiple dose bleomycin strategy to induce lasting lung injury in rats.

METHODS

Intratracheal instillation of bleomycin was administered to rats on multiple days. MSCs were intravenously infused 7 days apart. Detailed pulmonary function tests including forced expiratory volume, total lung capacity, and invasive hemodynamic measurements were conducted to define the representative disease model and monitor cardiopulmonary hemodynamic consequences of the cell infusion. Post-euthanasia assessments included a thorough evaluation of lung morphology and histopathology.

RESULTS

The double dose bleomycin instillation regimen resulted in severe and irreversible lung injury and fibrosis. Cardiopulmonary physiological monitoring reveled that no adverse events could be attributed to the cell infusion process.

DISCUSSION

Although our study did not show the infusion of MSCs to result in an improvement in lung function or rescue of damaged tissue this study does confirm the safety of MSC infusion into damaged lungs.

Profibrotic up-regulation of glucose transporter 1 by TGF-β involves activation of MEK and mammalian target of rapamycin complex 2 pathways

TGF-β plays a central role in the pathogenesis of fibroproliferative disorders. Defining the exact underlying molecular basis is therefore critical for the development of viable therapeutic strategies. Here, we show that expression of the facilitative glucose transporter 1 (GLUT1) is induced by TGF-β in fibroblast lines and primary cells and is required for the profibrotic effects of TGF-β. In addition, enhanced GLUT1 expression is observed in fibrotic areas of lungs of both patients with idiopathic pulmonary fibrosis and mice that are subjected to a fibrosis-inducing bleomycin treatment. By using pharmacologic and genetic approaches, we demonstrate that up-regulation of GLUT1 occurs via the canonical Smad2/3 pathway and requires autocrine activation of the receptor tyrosine kinases, platelet-derived and epidermal growth factor receptors. Engagement of the common downstream effector PI3K subsequently triggers activation of the MEK and mammalian target of rapamycin complex 2, which cooperate in regulating GLUT1 expression. Of note, inhibition of GLUT1 activity and/or expression is shown to impair TGF-β-driven fibrogenic processes, including cell proliferation and production of profibrotic mediators. These findings provide new perspectives on the interrelation of metabolism and profibrotic TGF-β signaling and present opportunities for potential therapeutic intervention.-Andrianifahanana, M., Hernandez, D. M., Yin, X., Kang, J.-H., Jung, M.-Y., Wang, Y., Yi, E. S., Roden, A. C., Limper, A. H., Leof, E. B. Profibrotic up-regulation of glucose transporter 1 by TGF-β involves activation of MEK and mammalian target of rapamycin complex 2 pathways.

Contribution of the anaphylatoxin receptors, C3aR and C5aR, to the pathogenesis of pulmonary fibrosis

Complement activation, an integral arm of innate immunity, may be the critical link to the pathogenesis of idiopathic pulmonary fibrosis (IPF). Whereas we have previously reported elevated anaphylatoxins-complement component 3a (C3a) and complement component 5a (C5a)-in IPF, which interact with TGF-β and augment epithelial injury in vitro, their role in IPF pathogenesis remains unclear. The objective of the current study is to determine the mechanistic role of the binding of C3a/C5a to their respective receptors (C3aR and C5aR) in the progression of lung fibrosis. In normal primary human fetal lung fibroblasts, C3a and C5a induces mesenchymal activation, matrix synthesis, and the expression of their respective receptors. We investigated the role of C3aR and C5aR in lung fibrosis by using bleomycin-injured mice with fibrotic lungs, elevated local C3a and C5a, and overexpression of their receptors via pharmacologic and RNA interference interventions. Histopathologic examination revealed an arrest in disease progression and attenuated lung collagen deposition (Masson's trichrome, hydroxyproline, collagen type I α 1 chain, and collagen type I α 2 chain). Pharmacologic or RNA interference-specific interventions suppressed complement activation (C3a and C5a) and soluble terminal complement complex formation (C5b-9) locally and active TGF-β1 systemically. C3aR/C5aR antagonists suppressed local mRNA expressions of tgfb2, tgfbr1/2, ltbp1/2, serpine1, tsp1, bmp1/4, pdgfbb, igf1, but restored the proteoglycan, dcn Clinically, compared with pathologically normal human subjects, patients with IPF presented local induction of C5aR, local and systemic induction of soluble C5b-9, and amplified expression of C3aR/C5aR in lesions. The blockade of C3aR and C5aR arrested the progression of fibrosis by attenuating local complement activation and TGF-β/bone morphologic protein signaling as well as restoring decorin, which suggests a promising therapeutic strategy for patients with IPF.-Gu, H., Fisher, A. J., Mickler, E. A., Duerson, F., III, Cummings, O. W., Peters-Golden, M., Twigg, H. L., III, Woodruff, T. M., Wilkes, D. S., Vittal, R. Contribution of the anaphylatoxin receptors, C3aR and C5aR, to the pathogenesis of pulmonary fibrosis.

New frontiers in fibrotic disease therapies: The focus of the Joan and Joel Rosenbloom Center for Fibrotic Diseases at Thomas Jefferson University

Fibrotic diseases constitute a world-wide major health problem, but research support remains inadequate in comparison to the need. Although considerable understanding of the pathogenesis of fibrotic reactions has been attained, no completely effective therapies exist. Although fibrotic disorders are diverse, it is universally appreciated that a particular cell type with unique characteristics, the myofibroblast, is responsible for replacement of functioning tissue with non-functional scar tissue. Understanding the cellular and molecular mechanisms responsible for the creation of myofibroblasts and their activities is central to the development of therapies. Critical signaling cascades, initiated primarily by TGF-β, but also involving other cytokines which stimulate pro-fibrotic reactions in the myofibroblast, offer potential therapeutic targets. However, because of the multiplicity and complex interactions of these signaling pathways, it is very unlikely that any single drug will be successful in modifying a major fibrotic disease. Therefore, we have chosen to examine the effectiveness of administration of several drug combinations in a mouse pneumoconiosis model. Such treatment proved to be effective. Because fibrotic diseases that tend to be chronic, are difficult to monitor, and are patient variable, implementation of clinical trials is difficult and expensive. Therefore, we have made efforts to identify and validate non-invasive biomarkers found in urine and blood. We describe the potential utility of five such markers: (i) the EDA form of fibronectin (Fn(EDA)), (ii) lysyl oxidase (LOX), (iii) lysyl oxidase-like protein 2 (LoxL2), (iv) connective tissue growth factor (CTGF, CCNII), and (v) the N-terminal propeptide of type III procollagen (PIIINP).

Combined inhibition of TGFβ and PDGF signaling attenuates radiation-induced pulmonary fibrosis

Background: Radiotherapy (RT) is a mainstay for the treatment of lung cancer, but the effective dose is often limited by the development of radiation-induced pneumonitis and pulmonary fibrosis. Transforming growth factor β (TGFβ) and platelet-derived growth factor (PDGF) play crucial roles in the development of these diseases, but the effects of dual growth factor inhibition on pulmonary fibrosis development remain unclear. Methods: C57BL/6 mice were treated with 20 Gy to the thorax to induce pulmonary fibrosis. PDGF receptor inhibitors SU9518 and SU14816 (imatinib) and TGFβ receptor inhibitor galunisertib were applied individually or in combinations after RT. Lung density and septal fibrosis were measured by high-resolution CT and MRI. Lung histology and gene expression analyses were performed and Osteopontin levels were studied. Results: Treatment with SU9518, SU14816 or galunisertib individually attenuated radiation-induced pulmonary inflammation and fibrosis and decreased radiological and histological signs of lung damage. Combining PDGF and TGFβ inhibitors showed to be feasible and safe in a mouse model, and dual inhibition significantly attenuated radiation-induced lung damage and extended mouse survival compared to blockage of either pathway alone. Gene expression analysis of irradiated lung tissue showed upregulation of PDGF and TGFβ-dependent signaling components by thoracic irradiation, and upregulation patterns show crosstalk between downstream mediators of the PDGF and TGFβ pathways. Conclusion: Combined small-molecule inhibition of PDGF and TGFβ signaling is a safe and effective treatment for radiation-induced pulmonary inflammation and fibrosis in mice and may offer a novel approach for treatment of fibrotic lung diseases in humans. Translational statement: RT is an effective treatment modality for cancer with limitations due to acute and chronic toxicities, where TGFβ and PDGF play a key role. Here, we show that a combined inhibition of TGFβ and PDGF signaling is more effective in attenuating radiation-induced lung damage compared to blocking either pathway alone. We used the TGFβ-receptor I inhibitor galunisertib, an effective anticancer compound in preclinical models and the PDGFR inhibitors imatinib and SU9518, a sunitinib analog. Our signaling data suggest that the reduction of TGFβ and PDGF signaling and the attenuation of SPP1 (Osteopontin) expression may be responsible for the observed benefits. With the clinical availability of similar compounds currently in phase-I/II trials as cancer therapeutics or already approved for certain cancers or idiopathic lung fibrosis (IPF), our study suggests that the combined application of small molecule inhibitors of TGFβ and PDGF signaling may offer a promising approach to treat radiation-associated toxicity in RT of lung cancer.

Activation of annexin A1 signalling in renal fibroblasts exerts antifibrotic effects

AIM

The anti-inflammatory protein annexin A1 (AnxA1) and its formyl peptide receptor 2 (FPR2) have protective effects in organ fibrosis. Their role in chronic kidney disease (CKD) has not yet been elucidated. Our aim was to characterize the AnxA1/FPR2 system in models of renal fibrosis.

METHODS

Rats were treated with angiotensin receptor antagonist during the nephrogenic period (ARAnp) to induce late-onset hypertensive nephropathy and fibrosis. Localization and regulation of AnxA1 and FPR2 were studied by quantitative real-time PCR and double labelling immunofluorescence. Biological effects of AnxA1 were studied in cultured renal fibroblasts from AnxA1(-/-) and wild-type mice.

RESULTS

Angiotensin receptor antagonist during the nephrogenic period kidneys displayed matrix foci containing CD73(+) fibroblasts, alpha-smooth muscle actin (a-SMA)(+) myofibroblasts and CD68(+) macrophages. TGF-β and AnxA1 mRNAs were ~threefold higher than in controls. AnxA1 was localized to macrophages and fibroblasts; myofibroblasts were negative. FPR2 was localized to fibroblasts, myofibroblasts, macrophages and endothelial cells. AnxA1 and FPR2 immunoreactive signals were increased in the foci, with fibroblasts and macrophages expressing both proteins. AnxA1(-/-) fibroblasts revealed higher α-SMA (sevenfold) and collagen 1A1 (Col1A1; 144-fold) mRNA levels than controls. Treatment of murine WT fibroblasts with TGF-β (22.5 ng mL 24 h(-1)) increased mRNA levels of α-SMA (9.3-fold) and Col1A1 (fourfold). These increases were greatly attenuated upon overexpression of AnxA1 (1.5- and 1.7-fold, respectively; P < 0.05). Human fibroblasts reacted similarly when receiving the FPR2 inhibitor WRW4.

CONCLUSION

Our results demonstrate that AnxA1 and FPR2 are abundantly expressed in the renal interstitium and modulate fibroblast phenotype and extracellular matrix synthesis activity.

Systemically Administered, Target Organ-Specific Therapies for Regenerative Medicine

Growth factors and other agents that could potentially enhance tissue regeneration have been identified, but their therapeutic value in clinical medicine has been limited for reasons such as difficulty to maintain bioactivity of locally applied therapeutics in the protease-rich environment of regenerating tissues. Although human diseases are treated with systemically administered drugs in general, all current efforts aimed at enhancing tissue repair with biological drugs have been based on their local application. The systemic administration of growth factors has been ruled out due to concerns about their safety. These concerns are warranted. In addition, only a small proportion of systemically administered drugs reach their intended target. Selective delivery of the drug to the target tissue and use of functional protein domains capable of penetrating cells and tissues could alleviate these problems in certain circumstances. We will present in this review a novel approach utilizing unique molecular fingerprints (“Zip/postal codes”) in the vasculature of regenerating tissues that allows target organ-specific delivery of systemically administered therapeutic molecules by affinity-based physical targeting (using peptides or antibodies as an “address tag”) to injured tissues undergoing repair. The desired outcome of targeted therapies is increased local accumulation and lower systemic concentration of the therapeutic payload. We believe that the physical targeting of systemically administered therapeutic molecules could be rapidly adapted in the field of regenerative medicine.

Nintedanib: evidence for its therapeutic potential in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive disease with poor prognosis. The molecular mechanisms involved in the progression of IPF are not fully understood; however, the platelet-derived growth factor (PDGF)/PDGF receptor pathway is thought to play a critical role in fibrogenesis of the lungs. Other growth factors, including fibroblast growth factor and vascular endothelial growth factor, are also thought to contribute to the pathogenesis of pulmonary fibrosis. Nintedanib is an inhibitor of multiple tyrosine kinases, including receptors for PDGF, fibroblast growth factor, and vascular endothelial growth factor. In the Phase II TOMORROW trial, treatment with 150 mg of nintedanib twice daily showed a trend to slow the decline in lung function and significantly decrease acute exacerbations in patients with IPF, while showing an acceptable safety profile. The Phase III INPULSIS trials demonstrated a significant decrease in the annual rate of decline in forced vital capacity in IPF patients treated with 150 mg nintedanib twice daily. In the INPULSIS-2 trial, the time to the first acute exacerbation significantly increased in IPF patients who were treated with 150 mg of nintedanib twice daily. Pirfenidone, another antifibrotic drug, was shown to limit the decline in pulmonary function in patients with IPF in the ASCEND trial. Combination therapy with nintedanib and pirfenidone is anticipated, although further evaluation of its long-term safety is needed. There is limited evidence for the safety of the combination therapy although a Phase II trial conducted in Japan demonstrated that combination therapy with nintedanib and pirfenidone was tolerable for 1 month. Available antifibrotic agents (ie, pirfenidone and N-acetylcysteine) have limited efficacy as single therapies for IPF; therefore, further study of combination therapy with antifibrotic agents is needed.

The role of tyrosine kinases in the pathogenesis of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease with a median survival time from diagnosis of 2-3 years. Although the pathogenic pathways have not been fully elucidated, IPF is believed to be caused by persistent epithelial injury in genetically susceptible individuals. Tyrosine kinases are involved in a range of signalling pathways that are essential for cellular homeostasis. However, there is substantial evidence from in vitro studies and animal models that receptor tyrosine kinases, such as the platelet-derived growth factor receptor, vascular endothelial growth factor receptor and fibroblast growth factor receptor, and non-receptor tyrosine kinases, such as the Src family, play critical roles in the pathogenesis of pulmonary fibrosis. For example, the expression and release of tyrosine kinases are altered in patients with IPF, while specific tyrosine kinases stimulate the proliferation of lung fibroblasts in vitro. Agents that inhibit tyrosine kinases have shown anti-fibrotic and anti-inflammatory effects in animal models of pulmonary fibrosis. Recently, the tyrosine kinase inhibitor nintedanib has shown positive results in two phase III trials in patients with IPF. Here, we summarise the evidence for involvement of specific tyrosine kinases in the pathogenesis of IPF and the development of tyrosine kinase inhibitors as treatments for IPF.

Targeting CTGF, EGF and PDGF pathways to prevent progression of kidney disease

Chronic kidney disease (CKD) is a major health and economic burden with a rising incidence. During progression of CKD, the sustained release of proinflammatory and profibrotic cytokines and growth factors leads to an excessive accumulation of extracellular matrix. Transforming growth factor β (TGF-β) and angiotensin II are considered to be the two main driving forces in fibrotic development. Blockade of the renin-angiotensin-aldosterone system has become the mainstay therapy for preservation of kidney function, but this treatment is not sufficient to prevent progression of fibrosis and CKD. Several factors that induce fibrosis have been identified, not only by TGF-β-dependent mechanisms, but also by TGF-β-independent mechanisms. Among these factors are the (partially) TGF-β-independent profibrotic pathways involving connective tissue growth factor, epidermal growth factor and platelet-derived growth factor and their receptors. In this Review, we discuss the specific roles of these pathways, their interactions and preclinical evidence supporting their qualification as additional targets for novel antifibrotic therapies.

Role of epidermal growth factor receptor in vascular structure and function

PURPOSE OF THE REVIEW

The epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase with a wide implication in tumor biology, wound healing and development. Besides acting as a growth factor receptor activated by ligands such as EGF, the EGFR can also be transactivated and thereby mediate cross-talk with different signaling pathways. The aim of this review is to illustrate the Janus-faced function of the EGFR in the vasculature with its relevance for vascular biology and disease.

RECENT FINDINGS

Over recent years, the number of identified signaling partners of the EGFR has steadily increased, as have the biological processes in which the EGFR is thought to be involved. Recently, new models have allowed investigation of EGFR effects in vivo, shedding some light on the overall function of the EGFR in the vasculature. At the same time, EGFR inhibitors and antibodies have become increasingly established in cancer therapy, providing potential therapeutic tools for decreasing EGFR signaling.

SUMMARY

The EGFR is a versatile signaling pathway integrator associated with vascular homeostasis and disease. In addition to modulating basal vascular tone and tissue homeostasis, the EGFR also seems to be involved in proinflammatory, proliferative, migratory and remodeling processes, with enhanced deposition of extracellular matrix components, thereby promoting vascular diseases such as hypertension or atherosclerosis.

Inhibition of the αvβ6 integrin leads to limited alteration of TGF-α-induced pulmonary fibrosis

A number of growth factors and signaling pathways regulate matrix deposition and fibroblast proliferation in the lung. The epidermal growth factor receptor (EGFR) family of receptors and the transforming growth factor-β (TGF-β) family are active in diverse biological processes and are central mediators in the initiation and maintenance of fibrosis in many diseases. Transforming growth factor-α (TGF-α) is a ligand for the EGFR, and doxycycline (Dox)-inducible transgenic mice conditionally expressing TGF-α specifically in the lung epithelium develop progressive fibrosis accompanied with cachexia, changes in lung mechanics, and marked pleural thickening. Although recent studies demonstrate that EGFR activation modulates the fibroproliferative effects involved in the pathogenesis of TGF-β induced pulmonary fibrosis, in converse, the direct role of EGFR induction of the TGF-β pathway in the lung is unknown. The αvβ6 integrin is an important in vivo activator of TGF-β activation in the lung. Immunohistochemical analysis of αvβ6 protein expression and bronchoalveolar analysis of TGF-β pathway signaling indicates activation of the αvβ6/TGF-β pathway only at later time points after lung fibrosis was already established in the TGF-α model. To determine the contribution of the αvβ6/TGF-β pathway on the progression of established fibrotic disease, TGF-α transgenic mice were administered Dox for 4 wk, which leads to extensive fibrosis; these mice were then treated with a function-blocking anti-αvβ6 antibody with continued administration of Dox for an additional 4 wk. Compared with TGF-α transgenic mice treated with control antibody, αvβ6 inhibition significantly attenuated pleural thickening and altered the decline in lung mechanics. To test the effects of genetic loss of the β6 integrin, TGF-α transgenic mice were mated with β6-null mice and the degree of fibrosis was compared in adult mice following 8 wk of Dox administration. Genetic ablation of the β6 integrin attenuated histological and physiological changes in the lungs of TGF-α transgenic mice although a significant degree of fibrosis still developed. In summary, inhibition of the β6 integrin led to a modest, albeit significant, effect on pleural thickening and lung function decline observed with TGF-α-induced pulmonary fibrosis. These data support activation of the αvβ6/TGF-β pathway as a secondary effect contributing to TGF-α-induced pleural fibrosis and suggest a complex contribution of multiple mediators to the maintenance of progressive fibrosis in the lung.

Targeting EGFR signalling in chronic lung disease: therapeutic challenges and opportunities

Chronic respiratory diseases, including pulmonary fibrosis, chronic obstructive pulmonary disease (COPD) and lung cancer, are the second leading cause of death among Europeans. Despite this, there have been only a few therapeutic advances in these conditions over the past 20 years. In this review we provide evidence that targeting the epidermal growth factor receptor (EGFR) signalling pathway may represent a novel therapeutic panacea for treating chronic lung disease. Using evidence from human patient samples, transgenic animal models, and cell and molecular biology studies we highlight the roles of this signalling pathway in lung development, homeostasis, repair, and disease ontogeny. We identify mechanisms underlying lung EGFR pathway regulation and suggest how targeting these mechanisms using new and existing therapies has the potential to improve future lung cancer, COPD and pulmonary fibrosis patient outcomes.

Transforming growth factor β and platelet-derived growth factor modulation of myofibroblast development from corneal fibroblasts in vitro

The purpose of this study was to test the hypotheses that development of mature vimentin+/α-smooth muscle actin+/desmin+ (V+A+D+) myofibroblasts from corneal fibroblasts is regulated by transforming growth factor (TGF) β and platelet-derived growth factor (PDGF); and that myofibroblast development in vitro follows a similar developmental pathway as it does in vivo. Mouse corneal stromal fibroblasts (MSF) were isolated from the corneas of Swiss Webster mice and cultured in serum-free media augmented with DMEM/F12 and varying doses of TGFβ (0.1-2.0 ng/ml), with and without mouse PDGF-AA and/or PDGF-BB (2.0 ng/ml), to study the transition of the MSF to V+A+D+ myofibroblasts. The mean percentage of vimentin+, α-SMA+ and desmin+ cells was determined at each time point (2-15 days), with each growth factor concentration. MSF in vitro were noted to undergo the same developmental transition from V+A-D- to V+A+D- to V+A+D+ myofibroblasts as precursors undergo in vivo. TGFβ at a dose of 0.5 ng/ml and 1.0 ng/ml with 2.0 ng/ml PDGF-AA and 2.0 ng/ml PDGF-BB in DMEM/F12 serum-free media was optimal for the development of V+A+D+ myofibroblasts. This study defines optimal in vitro conditions to monitor the development of MSF into myofibroblasts. The combined effects of TGFβ and PDGF promote the full development of V+A+D+ myofibroblasts from MSF.