Pathobiology Of Idiopathic Pulmonary Fibrosis Research Articles

Therapeutic Strategies for Idiopathic Pulmonary Fibrosis - Thriving Present and Promising Tomorrow.

Idiopathic pulmonary fibrosis (IPF) is a continuous, progressive, and lethal age-related respiratory disease. It is characterized by condensed and rigid lung tissue, which leads to a decline in the normal functioning of the lungs. The pathophysiology of IPF has still not been completely elucidated, so current strategies are lagging behind with respect to improving the condition of patients with IPF and increasing their survival rate. The desire for a better understanding of the pathobiology of IPF and its early detection has led to the identification of various biomarkers associated with IPF. The use of drugs such as pirfenidone and nintedanib as a safe and effective treatment alternative have marked a new chapter in the treatment of IPF. However, nonpharmacological therapies, involving long-term oxygen therapy, transplantation of the lungs, pulmonary rehabilitation, ventilation, and palliative care for cough and dyspnea, are still considered to be beneficial as supplementary methods for IPF therapy. A major risk factor for IPF is aging, with associated hallmarks such as telomere attrition, senescence, epigenetic drift, stem cell exhaustion, loss of proteostasis, and mitochondrial dysfunction. These are promising earmarks for the development of potential therapy for the disease. In this review, we have discussed current and emerging novel therapeutic strategies for IPF, especially for targets associated with age-related mechanisms.

Lung immune signatures define two groups of end-stage IPF patients

BackgroundThe role of the immune system in the pathobiology of Idiopathic Pulmonary Fibrosis (IPF) is controversial.MethodsTo investigate it, we calculated immune signatures with Gene Set Variation Analysis (GSVA) and applied them to the lung transcriptome followed by unbiased cluster analysis of GSVA immune-enrichment scores, in 109 IPF patients from the Lung Tissue Research Consortium (LTRC). Results were validated experimentally using cell-based methods (flow cytometry) in lung tissue of IPF patients from the University of Pittsburgh (n = 26). Finally, differential gene expression and hypergeometric test were used to explore non-immune differences between clusters.ResultsWe identified two clusters (C#1 and C#2) of IPF patients of similar size in the LTRC dataset. C#1 included 58 patients (53%) with enrichment in GSVA immune signatures, particularly cytotoxic and memory T cells signatures, whereas C#2 included 51 patients (47%) with an overall lower expression of GSVA immune signatures (results were validated by flow cytometry with similar unbiased clustering generation). Differential gene expression between clusters identified differences in cilium, epithelial and secretory cell genes, all of them showing an inverse correlation with the immune response signatures. Notably, both clusters showed distinct features despite clinical similarities.ConclusionsIn end-stage IPF lung tissue, we identified two clusters of patients with very different levels of immune signatures and gene expression but with similar clinical characteristics. Weather these immune clusters differentiate diverse disease trajectories remains unexplored.

Beyond epithelial damage: vascular and endothelial contributions to idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a progressive scarring disease of the lung with poor survival. The incidence and mortality of IPF are rising, but treatment remains limited. Currently, two drugs can slow the scarring process but often at the expense of intolerable side effects, and without substantially changing overall survival. A better understanding of mechanisms underlying IPF is likely to lead to improved therapies. The current paradigm proposes that repetitive alveolar epithelial injury from noxious stimuli in a genetically primed individual is followed by abnormal wound healing, including aberrant activity of extracellular matrix-secreting cells, with resultant tissue fibrosis and parenchymal damage. However, this may underplay the importance of the vascular contribution to fibrogenesis. The lungs receive 100% of the cardiac output, and vascular abnormalities in IPF include (a) heterogeneous vessel formation throughout fibrotic lung, including the development of abnormal dilated vessels and anastomoses; (b) abnormal spatially distributed populations of endothelial cells (ECs); (c) dysregulation of endothelial protective pathways such as prostacyclin signaling; and (d) an increased frequency of common vascular and metabolic comorbidities. Here, we propose that vascular and EC abnormalities are both causal and consequential in the pathobiology of IPF and that fuller evaluation of dysregulated pathways may lead to effective therapies and a cure for this devastating disease.

Bioactive lipid lysophosphatidic acid species are associated with disease progression in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive disease with significant mortality. Prognostic biomarkers to identify rapid progressors are urgently needed to improve patient management. Since the lysophosphatidic acid (LPA) pathway has been implicated in lung fibrosis in preclinical models and identified as a potential therapeutic target, we aimed to investigate if bioactive lipid LPA species could be prognostic biomarkers that predict IPF disease progression. LPAs and lipidomics were measured in baseline placebo plasma of a randomized IPF-controlled trial. The association of lipids with disease progression indices were assessed using statistical models. Compared to healthy, IPF patients had significantly higher levels of five LPAs (LPA16:0, 16:1, 18:1, 18:2, 20:4) and reduced levels of two triglycerides species (TAG48:4-FA12:0, -FA18:2) (false discovery rate < 0.05, fold change > 2). Patients with higher levels of LPAs had greater declines in diffusion capacity of carbon monoxide over 52 weeks (P < 0.01); additionally, LPA20:4-high (≥median) patients had earlier time to exacerbation compared to LPA20:4-low (<median) patients (hazard ratio (95% CI)): 5.71 (1.17–27.72) (P = 0.031). Higher baseline LPAs were associated with greater increases in fibrosis in lower lungs as quantified by high-resolution computed tomography at week 72 (P < 0.05). Some of these LPAs were positively associated with biomarkers of profibrotic macrophages (CCL17, CCL18, OPN, and YKL40) and lung epithelial damage (SPD and sRAGE) (P < 0.05). In summary, our study established the association of LPAs with IPF disease progression, further supporting the role of the LPA pathway in IPF pathobiology.

Idiopathic pulmonary fibrosis: state of the art for 2023.

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease characterised by worsening respiratory symptoms and physiological impairment. Increasing awareness of the clinical manifestations of IPF, more widespread use of computed tomography scans and other potential factors have contributed to a rising prevalence of IPF over the last two decades, especially among people over the age of 65 years. Significant advances in the understanding of the pathobiology of IPF have emerged, and multiple genetic and nongenetic contributors have been identified. The individual patient course and the rate of disease progression in IPF are often unpredictable and heterogeneous. The rate of lung function decline is further modified by treatment with antifibrotic therapies, which have been shown to slow down disease progression. The presence of comorbid conditions may increase symptom burden and impact survival. Clinical monitoring at regular intervals to assess for disease progression by worsening symptoms, physiological parameters and/or radiological features is essential to assess the natural disease course and to guide further management, including prompt detection of complications and comorbid conditions that warrant additional treatment considerations, and timely consideration of referral to palliative care and lung transplantation for the appropriate patient. More studies are needed to determine whether early detection of IPF might improve patient outcomes. The purpose of this concise clinical review is to provide an update on IPF diagnosis, epidemiology, natural history and treatment in the context of new knowledge and latest clinical practice guidelines.

Anti-fibrotic strategies and pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) results from the dysregulated process of injury and repair, which promotes scarring of the lung tissue and deposition of collagen-rich extracellular matrix (ECM) components, that make the lung unphysiologically stiff. IPF presents a serious concern as its pathogenesis remains elusive, and current anti-fibrotic treatments are only effective in slowing rather than halting disease progression. The IPF disease pathogenesis is incompletely defined, complex and incorporates interplay between different fibrogenesis signaling pathways. Preclinical IPF experimental models used to validate drug candidates present significant limitations in modeling IPF pathobiology, with their limited time frame, simplicity and inaccurate representation of the disease and the mechanical influences of IPF. Potentially more accurate mimetic disease models that capture the cell-cell and cell-matrix interaction, such as 3D cultures, organoids and precision-cut lung slices (PCLS), may yield more meaningful clinical predictions for drug candidates. Recent advances in developing anti-fibrotic compounds have positioned drug towards targeting components of the fibrogenesis signaling pathway of IPF or the extracellular microenvironment. The major goals in this area of research focus on finding ways to reverse or halt the disease progression by utilizing more disease-relevant experimental models to improve the qualification of potential drug targets for treating pulmonary fibrosis.

DIFFERENTIAL EXPRESSION AND STABILITY OF XIAP AND CIAP-1 MAY INFLUENCE THE APOPTOSIS-RESISTANT PHENOTYPE OF LUNG FIBROBLASTS IN IDIOPATHIC PULMONARY FIBROSIS

DIFFERENTIAL EXPRESSION AND STABILITY OF XIAP AND CIAP-1 MAY INFLUENCE THE APOPTOSIS-RESISTANT PHENOTYPE OF LUNG FIBROBLASTS IN IDIOPATHIC PULMONARY FIBROSIS

Longitudinal and Comparative Measures of Serum Chitotriosidase and YKL-40 in Patients With Idiopathic Pulmonary Fibrosis.

BackgroundAlthough chitin is absent in humans, chitinases are present in healthy subjects and show dysregulated expression in a variety of diseases resulting from abnormal tissue injury and repair responses. It was shown that chitotriosidase (chitinase 1/CHIT1) and structurally-related chitinase 3-like 1 protein (CHI3L1/YKL-40) play important roles in the pathobiology of idiopathic pulmonary fibrosis (IPF), however little is known about their longitudinal serum levels and relationship to clinical measures in IPF.MethodsThe present study is the first to evaluate serial measurements of serum CHIT1 activity and YKL-40 concentrations in patients with IPF starting antifibrotic treatment and followed up for 24 months. In addition, baseline serum CHIT1 and YKL-40 were compared between patients with IPF and control subjects, and possible CHIT1 and YKL-40 relationships to longitudinal clinical assessments in IPF were explored.ResultsBaseline serum CHIT1 activity and YKL-40 concentrations were significantly elevated in patients with IPF compared to control subjects and showed similar discriminatory ability in distinguishing IPF from controls. No significant differences between the median serum CHIT1 activity and YKL-40 concentration measured over a study follow-up were noted. We found significantly elevated baseline serum CHIT1 activity in the progressors compared with the stables in the first year, while significantly increased baseline serum CHIT1 activity was noted in the stables compared to the progressors in the second year. Additionally, we observed a significant negative correlation between a change in serum YKL-40 concentration and a change in forced vital capacity (FVC) % predicted (% pred.) in the stables subgroup, whereas, a change in serum CHIT1 activity correlated negatively with a change in FVC% pred. in the progressors subgroup.ConclusionsThis explorative study findings add further evidence that CHIT1 and YKL-40 are upregulated in patients with IPF, and suggest that longitudinally stable serum CHIT1 activity and YKL-40 concentration levels may potentially be associated with the antifibrotic treatment response. In addition, our findings are supporting the possible role of CHIT1 and YKL-40 as candidate diagnostic and prognostic biomarkers in IPF. Further research is needed to validate present study findings.

Understanding idiopathic pulmonary fibrosis - Clinical features, molecular mechanism and therapies.

Idiopathic pulmonary fibrosis (IPF) is a chronic lung fibrosing disease with high prevalence that has a prognosis worse than many cancers. There has been a recent influx of new observations aimed at explaining the mechanisms responsible for the initiation and progression of pulmonary fibrosis. However, despite this, the pathogenesis of the disease is largely unclear. Recent progress has been made in the characterization of specific pathologic and clinical features that have enhanced the understanding of pathologically activated molecular pathways during the onset and progression of IPF. This review highlights several of the advances that have been made and focus on the pathobiology of IPF. The work also details the different factors that are responsible for the disposition of the disease - these may be internal factors such as cellular mechanisms and genetic alterations, or they may be external factors from the environment. The changes that primarily occur in epithelial cells and fibroblasts that lead to the activation of profibrotic pathways are discussed in depth. Finally, a complete repertoire of the treatment therapies that have been used in the past as well as future medications and therapies is provided.

The function of non-coding RNAs in idiopathic pulmonary fibrosis.

Non-coding ribonucleic acids (ncRNAs) are a diverse group of RNA molecules that are mostly not translated into proteins after transcription, including long non-coding RNAs (lncRNAs) with longer than 200 nucleotides non-coding transcripts and microRNAs (miRNAs) which are only 18–22 nucleotides. As families of evolutionarily conserved ncRNAs, lncRNAs activate and repress genes via a variety of mechanisms at both transcriptional and translational levels, whereas miRNAs regulate protein-coding gene expression mainly through mRNA silencing. ncRNAs are widely involved in biological functions, such as proliferation, differentiation, migration, angiogenesis, and apoptosis. Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease with a poor prognosis. The etiology of IPF is still unclear. Increasing evidence shows the close correlations between the development of IPF and aberrant expressions of ncRNAs than thought previously. In this study, we provide an overview of ncRNAs participated in pathobiology of IPF, seeking the early diagnosis biomarker and aiming for potential therapeutic applications for IPF.

Translational pharmacology of TD139, an inhaled small molecule galectin‐3 (Gal‐3) inhibitor for the treatment of idiopathic pulmonary fibrosis (IPF)

IntroductionGal‐3 is a pro‐fibrotic β‐galactoside‐binding lectin highly expressed in the lungs of IPF patients 1. TD139 is an inhaled, small molecule Gal‐3 inhibitor in development for IPF[2]. In this study the translational pharmacology of TD139 from pre‐clinical to clinical studies are presented.MethodsTD139 was evaluated in pre‐clinical studies investigating Gal‐3 in vitro and in vivo in naïve and bleomycin‐treated mice (male C57/Bl6 mice) 1, 2. A randomized, double‐blind, multi‐centre, placebo‐controlled, phase IIa study was completed to assess safety, tolerability, and PK/PD of TD139 in 24 patients with IPF. Inhaled TD139 was delivered at 0.3 mg, 3 mg or 10 mg QD to IPF patients (8 patients/cohort, 5:3 ratio (active:placebo)) for 14 days. Patients underwent bronchoalveolar lavage (BAL) prior to dosing and after 14 days. TD139 drug concentration was measured in the BAL fluid, BAL macrophages and plasma. Gal‐3 expression on BAL macrophages was measured by flow cytometry and systemic biomarkers of Gal‐3 inhibition and fibrosis measured in plasma.ResultsTD139 demonstrated high affinity (KD = 2.1 ± 0.1 nM (mean ± SD, n=4)) in vitro and reduced Gal‐3 expression ex vivo on IPF macrophages (IC50 = 361 ± 108 nM (mean ± SD, n=3 patients)). TD139 in vivo attenuated mechanistic PD (BAL Gal‐3) and fibrotic endpoints (total lung collagen/histology) in bleomycin‐treated mice with duration driven by lung retention. Clinically, inhaled TD139 was well tolerated at all doses with concentrations in BAL macrophages &gt;567‐fold higher than systemic exposure. Gal‐3 expression on BAL macrophages was significantly lower in the 3 mg (% change −52.52%, 95% CI −85.43% to −4.74%, P=0.023) and 10 mg (% change −78.60%, 95% CI −110.48% to −29.78%, P&lt;0.0001) dose groups compared to placebo, with a concentration‐dependent inhibition. Reduced Gal‐3 expression on BAL macrophages was associated with lower plasma biomarkers relevant to IPF pathobiology (PAI‐1, YKL‐40 and PDGF‐BB).ConclusionTD139 is safe and well tolerated in man and demonstrates low systemic exposure coupled with high lung concentrations resulting in suppression of Gal‐3 on BAL macrophages and decreased plasma biomarkers associated with IPF progression. Pre‐clinical in vitro and in vivo studies have shown to be clinically translatable. This study supported the progression of TD139 into a phase IIb IPF study 3.Support or Funding InformationAll studies were funded by Galecto Biotech AB.

The senescence-associated matricellular protein CCN1 in plasma of human subjects with idiopathic pulmonary fibrosis.

Cellular senescence has been linked to the pathogenesis of idiopathic pulmonary fibrosis (IPF). CCN1 is a matricellular protein that has been shown to induce cellular senescence and contribute to lung fibrosis in pre-clinical models. In this report, we determined plasma CCN1 levels in patients with IPF and its potential role in clinical outcomes. We evaluated 88 patients diagnosed with IPF at the University of Alabama at Birmingham. CCN1 levels were measured in plasma specimens by ELISA. The primary outcome measure was transplant-free survival (TFS) duration. High-CCN1 levels were associated with a lower transplant-free survival independent of %FVC and %DLCO compared to patients with low plasma CCN1 (HR=2.15; 95%CI 1.04-4.45, p=0.04). This study demonstrates that plasma levels of CCN1 may be predictive of survival in IPF. Given the plausible role of CCN1 in cellular senescence and pathobiology of IPF, the predictive value of CCN1 in disease progression among patients with IPF warrants further investigation.

Telomere Abnormalities in the Pathobiology of Idiopathic Pulmonary Fibrosis.

Idiopathic pulmonary fibrosis (IPF) occurs primarily in older adults and the incidence is clearly associated with aging. This disease seems to be associated with several hallmarks of aging, including telomere attrition and cellular senescence. Increasing evidence suggests that abnormalities involving telomeres and their proteome play a significant role in the pathobiology of IPF. The aim of this study is to summarize present knowledge in the field, as well as to discuss its possible clinical implications. Numerous mutations in genes associated with telomere functioning were studied in the context of IPF, mainly for Telomerase Reverse Transcriptase (TERT) and Telomerase RNA Component (TERC). Such mutations may lead to telomere shortening, which seems to increase the risk of IPF, negatively influence disease progression, and contribute to worse prognosis after lung transplantation. Some evidence indicates the possibility for the use of telomerase activators as potential therapeutic agents in pulmonary fibrosis. To sum up, increasing evidence suggests the role of telomere abnormalities in the pathobiology of IPF, natural history and prognosis of the disease. There are also possibilities for telomerase targeting in the potential development of new treatment agents. However, all these aspects require further research.

Redox Imbalance in Idiopathic Pulmonary Fibrosis: A Role for Oxidant Cross-Talk Between NADPH Oxidase Enzymes and Mitochondria.

Significance: Idiopathic pulmonary fibrosis (IPF) is a progressive age-related lung disease with a median survival of only 3 years after diagnosis. The pathogenic mechanisms behind IPF are not clearly understood, and current therapeutic approaches have not been successful in improving disease outcomes. Recent Advances: IPF is characterized by increased production of reactive oxygen species (ROS), primarily by NADPH oxidases (NOXes) and mitochondria, as well as altered antioxidant defenses. Recent studies have identified the NOX isoform NOX4 as a key player in various important aspects of IPF pathology. In addition, mitochondrial dysfunction is thought to enhance pathological features of IPF, in part by increasing mitochondrial ROS (mtROS) production and altering cellular metabolism. Recent findings indicate reciprocal interactions between NOX enzymes and mitochondria, which affect regulation of NOX activity as well as mitochondrial function and mtROS production, and collectively promote epithelial injury and profibrotic signaling. Critical Issues and Future Directions: The precise molecular mechanisms by which ROS from NOX or mitochondria contribute to IPF pathology are not known. This review summarizes the current knowledge with respect to the various aspects of ROS imbalance in the context of IPF and its proposed roles in disease development, with specific emphasis on the importance of inappropriate NOX activation, mitochondrial dysfunction, and the emerging evidence of NOX-mitochondria cross-talk as important drivers in IPF pathobiology.

Idiopathic Pulmonary Fibrosis: New and Emerging Treatment Options.

Idiopathic pulmonary fibrosis (IPF) is a progressive and debilitating, scarring lung disease with a worse prognosis than some cancers. The incidence of IPF is increasing and while current antifibrotic therapies slow disease progression, they do not offer a cure. The pathobiology of IPF is complex and is driven by aging-associated cellular dysfunction, epithelial injury, and an aberrant wound-healing response characterised by fibroblast activation and extracellular matrix accumulation (ECM) in the interstitium. As understanding of the underlying mechanisms has evolved, new targets for pharmacotherapy have emerged. Novel drugs currently in development for pulmonary fibrosis have diverse molecular properties and mechanisms of action, as well as different routes of administration. A shared primary goal of these agents is reduction of the profibrotic activity of fibroblasts and limitation of ECM deposition, which hinders gas exchange and ultimately leads to respiratory failure. This article provides an overview of some promising new therapeutic options for IPF and considers the challenges for future drug development.

Focus on Idiopathic Pulmonary Fibrosis: Advancing Approaches to Diagnosis, Prognosis, and Treatment

As seen in this CME online activity (available at http://courses.elseviercme.com/694), idiopathic pulmonary fibrosis (IPF) is a specific form of chronic, progressive, fibrotic lung disease of unknown cause that is associated with substantial health-care utilization and high rates of mortality. The clinical symptoms of IPF are nonspecific and overlap with many pulmonary and cardiac diseases making differential diagnosis challenging. The American Thoracic Society/European Respiratory Society/Japanese Respiratory Society/Latin American Thoracic Association (ATS/ERS/JRS/ALAT) guidelines strongly recommend a multidisciplinary approach to the diagnosis of interstitial lung diseases; however, there are several limitations to the feasibility of this approach in clinical practice. Although early diagnosis is relevant to any chronic, progressive, and irreversible disorder, it is crucially important that effective treatments for IPF are prescribed without delay. A window of opportunity may exist during which time treatment can have optimal outcomes. Evidence on the clinical management of IPF is rapidly evolving, and key updates were made to the most recent ATS/ERS/JRS/ALAT guidelines. The widely used combination of prednisone, azathioprine, and N-acetylcysteine has now been associated with increased risk of hospitalization and death compared with placebo in patients with IPF. These treatments and others for IPF have been mostly supportive, but recently pirfenidone and nintedanib have demonstrated efficacy in reducing functional decline and disease progression in IPF. A pooled analysis of three phase 3 studies of pirfenidone found a significant 48%reduction in all-cause mortality, and a pooled analysis of a phase 2 and two phase 3 studies of nintedanib found a significant 43%reduction in on-treatment mortality. As patient exposure to these two new drugs increases, data continue to emerge on how and when to use these medications and on how to manage their side effects. Finally, several medications targeting the fibrotic pathobiology of IPF are currently in development. Given the limited treatment options for IPF, enrollment in a clinical trial may be the best chance to delay or prevent progression of IPF. This CME-certified expert video roundtable from CHEST reviews the ATS/ERS/JRS/ALAT guidelines with a specific focus on accurate and timely diagnosis of IPF and the latest data on the treatment of IPF.

Targeted Therapy for Idiopathic Pulmonary Fibrosis: Where To Now?

Idiopathic pulmonary fibrosis (IPF) is an aging-associated, recalcitrant lung disease with historically limited therapeutic options. The recent approval of two drugs, pirfenidone and nintedanib, by the US Food and Drug Administration in 2014 has heralded a new era in its management. Both drugs have demonstrated efficacy in phaseIII clinical trials by retarding the rate of progression of IPF; neither drug appears to be able to completely arrest disease progression. Advances in the understanding of IPF pathobiology have led to an unprecedented expansion in the number of potential therapeutic targets. Drugs targeting several of these are under investigation in various stages of clinical development. Here, we provide a brief overview of the drugs that are currently approved and others in phaseII clinical trials. Future therapeutic opportunities that target novel pathways, including some that are associated with the biology of aging, are examined. A multi-targeted approach, potentially with combination therapies, and identification of individual patients (or subsets of patients) who may respond more favourably to specific agents are likely to be more effective.

An Official American Thoracic Society Workshop Report: Comparative Pathobiology of Fibrosing Lung Disorders in Humans and Domestic Animals

The clinical outcome of idiopathic pulmonary fibrosis (IPF) is poor, with a 50% survival rate at 3 years. Furthermore, current treatments provide little amelioration of symptoms. Despite significant advances in understanding the clinical features and pathobiology of IPF, further advances have been hampered by a lack of suitable animal models of the disease. Interestingly, spontaneously occurring disorders with a similarity to IPF have been recognized in the dog, cat, horse, and donkey. These disorders share clinical and pathologic features with human IPF and are emerging diseases of veterinary importance. To improve awareness about these disorders in domestic animals and stimulate interactions between disciplines, and to facilitate the elucidation of mechanisms of fibrosing lung disorders using a comparative natural-occurrence disease model approach. A 1-day meeting joined physicians, veterinarians, pathologists, researchers, and advocacy experts to discuss information available in this area. A review of the literature was conducted, and an executive committee discussed the findings and prepared a summary statement during subsequent meetings. Clinical, diagnostic, and treatment opportunities were identified, and common areas of interest where collaborative efforts could accelerate discovery regarding etiological factors, methods for early detection, determinants of disease progression, and novel therapies were defined. Comparing fibrosing lung disorders in humans and domestic animals will allow for a better understanding of the similarities and differences among species and may offer novel insights into the underlying mechanisms of spontaneously occurring fibrotic lung diseases.

Epigenetic Regulation of miR-17∼92 Contributes to the Pathogenesis of Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a disease of progressive lung fibrosis with a high mortality rate. In organ repair and remodeling, epigenetic events are important. MicroRNAs (miRNAs) regulate gene expression post-transcriptionally and can target epigenetic molecules important in DNA methylation. The miR-17~92 miRNA cluster is critical for lung development and lung epithelial cell homeostasis and is predicted to target fibrotic genes and DNA methyltransferase (DNMT)-1 expression. We investigated the miR-17~92 cluster expression and its role in regulating DNA methylation events in IPF lung tissue. Expression and DNA methylation patterns of miR-17~92 were determined in human IPF lung tissue and fibroblasts and fibrotic mouse lung tissue. The relationship between the miR-17~92 cluster and DNMT-1 expression was examined in vitro. Using a murine model of pulmonary fibrosis, we examined the therapeutic potential of the demethylating agent, 5'-aza-2'-deoxycytidine. Compared with control samples, miR-17~92 expression was reduced in lung biopsies and lung fibroblasts from patients with IPF, whereas DNMT-1 expression and methylation of the miR-17~92 promoter was increased. Several miRNAs from the miR-17~92 cluster targeted DNMT-1 expression resulting in a negative feedback loop. Similarly, miR-17~92 expression was reduced in the lungs of bleomycin-treated mice. Treatment with 5'-aza-2'-deoxycytidine in a murine bleomycin-induced pulmonary fibrosis model reduced fibrotic gene and DNMT-1 expression, enhanced miR-17~92 cluster expression, and attenuated pulmonary fibrosis. This study provides insight into the pathobiology of IPF and identifies a novel epigenetic feedback loop between miR-17~92 and DNMT-1 in lung fibrosis.

STAT3

Pulmonary fibrosis is a devastating, relentlessly progressive, and lethal disease. There is a significant unmet need for effective treatment since currently no FDA-approved therapies exist. Current thinking suggests that idiopathic pulmonary fibrosis (IPF) is initiated by pathways similar to normal wound healing, but relentless fibrosis occurs secondary to absent or defective inhibitory mechanisms that normally terminate wound healing. The heterogeneous pathological presentation of fibrosis suggests that the anatomic location and origin of fibroblasts and other cells might be critical for their phenotype and function and will impact on strategies to prevent or treat fibrotic lung diseases. This review summarizes our current understanding of the pathobiology of IPF, with a specific focus on the role of STAT3 in regulating cellular responses that may contribute to or inhibit pro-fibrotic processes. An improved understanding of the complex cell-type specific roles that this transcription factor plays in normal lung and in fibrosis is required to determine its suitability as an effective therapeutic target.