[Show abstract][Hide abstract] ABSTRACT: Background: Up to 20% of cases of idiopathic interstitial pneumonia (IIP) cluster in families, comprising the syndrome of Familial Interstitial Pneumonia (FIP); however, the genetic basis of FIP remains uncertain in a majority of families. We hypothesized that new disease-causing rare genetic variants could be identified using whole-exome sequencing of affected members from FIP families, providing additional insights into disease pathogenesis. Methods: Affected subjects from 25 kindreds were selected from an ongoing FIP registry for whole-exome sequencing (WES) from genomic DNA. Candidate rare variants were confirmed by Sanger sequencing and co-segregation analysis was performed in families, followed by additional sequencing of affected individuals from another163 kindreds. Results: We identified a potentially damaging rare variant in the gene encoding for regulator of telomere elongation helicase 1 (RTEL1) that segregated with disease and was associated with very short telomeres in peripheral blood mononuclear cells in one of 25 families in our original WES cohort. Evaluation of affected individuals in 163 additional kindreds revealed another 8 families (5%) with heterozygous rare variants in RTEL1 that segregated with clinical FIP. Probands and unaffected carriers of these rare variants had short telomeres (<10% for age) in peripheral blood mononuclear cells and increased T-circle formation, suggesting impaired RTEL1 function. Conclusions: Rare loss-of-function variants in RTEL1 represent a newly defined genetic predisposition for FIP, supporting the importance of telomere-related pathways in pulmonary fibrosis.
American journal of respiratory and critical care medicine. 02/2015; 21.
[Show abstract][Hide abstract] ABSTRACT: Introduction: Asymptomatic relatives of patients with Familial Interstitial Pneumonia (FIP), the inherited form of Idiopathic Interstitial Pneumonia (IIP), carry increased risk for developing interstitial lung disease. Studying these at-risk individuals provides a unique opportunity to investigate early stages of FIP pathogenesis and develop predictive models of disease onset. Methods: Seventy-five asymptomatic first-degree relatives of FIP patients (mean age 50.8 years) underwent blood sampling and high-resolution chest CT (HRCT) scan in an ongoing cohort study; 72 consented to bronchoscopy with bronchoalveolar lavage (BAL) and transbronchial biopsies. Twenty-seven healthy individuals were used as controls. Results: Eleven of 75 at-risk subjects (14%) had evidence of interstitial changes by HRCT while 35.2% had abnormalities on transbronchial biopsies. No differences were noted in inflammatory cells in BAL between at-risk individuals and controls. At-risk subjects had increased herpesvirus DNA in cell-free BAL and evidence of herpesvirus antigen expression in alveolar epithelial cells (AECs), which correlated with expression of endoplasmic reticulum stress markers in AECs. Peripheral blood mononuclear cell and AEC telomere length were shorter in at-risk individuals than healthy controls. The minor allele frequency of the Muc5B rs35705950 promoter polymorphism was increased in at-risk subjects. Levels of several plasma biomarkers differed between at-risk subjects and controls, and correlated with abnormal HRCT scans. Conclusions: Evidence of lung parenchymal remodeling and epithelial dysfunction were identified in asymptomatic individuals at-risk for FIP. Together, these findings offer new insights into the early pathogenesis of IIP and provide an ongoing opportunity to characterize presymptomatic abnormalities that predict progression to clinical disease.
American Journal of Respiratory and Critical Care Medicine 11/2014; · 11.99 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Short telomeres are frequently identified in patients with idiopathic pulmonary fibrosis (IPF) and its inherited form, familial interstitial pneumonia (FIP). We identified an FIP kindred with short telomeres who did not carry a mutation in known FIP genes TERT or hTR. We performed targeted sequencing of other telomere-related genes to identify the genetic basis of FIP in this kindred.
DNA was isolated from peripheral blood mononuclear cells or paraffin-embedded lung block and PCR-based sequencing of DKC1, NOP10, TINF2 and NHP2 was performed. Peripheral blood mononuclear cell telomere length was measured by southern blot. Alveolar epithelial cell (AEC) telomere length was measured by fluorescence-in-situ-hydridization. Dyskerin and hTR expression in lymphoblastoid cell lines were measured by qPCR.
The proband was a 69 year-old man with dyspnea, restrictive pulmonary function tests and reticular changes on high-resolution CT. An older male sibling had died from IPF. The proband had markedly shortened telomeres in peripheral blood and undetectably short telomeres in alveolar epithelial cells. Sequencing of dyskerin (DKC1) revealed that both affected siblings shared a novel A to G 1213 transition near the hTR binding domain that is predicted to encode a Thr405Ala amino acid substitution. hTR levels were decreased out of proportion to DKC1 expression in the T405A DKC1 proband, suggesting this mutation destabilizes hTR and impairs telomerase function.
This DKC1 variant represents the third telomere-related gene identified as a genetic cause of FIP. Further investigation into mechanism by which dyskerin contributes to the development of lung fibrosis is warranted.
[Show abstract][Hide abstract] ABSTRACT: Although in some cases clinical and radiographic features may be sufficient to establish a diagnosis of diffuse parenchymal lung disease (DPLD), surgical lung biopsy is frequently required. Recently a new technique for bronchoscopic lung biopsy has been developed using flexible cryo-probes. In this study we describe our clinical experience using bronchoscopic cryobiopsy for diagnosis of diffuse lung disease.
A retrospective study of subjects who had undergone bronchoscopic cryobiopsy for evaluation of DPLD at an academic tertiary care center from January 1, 2012 through January 15, 2013 was performed. The procedure was performed using a flexible bronchoscope to acquire biopsies of lung parenchyma. H&E stained biopsies were reviewed by an expert lung pathologist.
Twenty-five eligible subjects were identified. With a mean area of 64.2 mm(2), cryobiopsies were larger than that typically encountered with traditional transbronchial forceps biopsy. In 19 of the 25 subjects, a specific diagnosis was obtained. In one additional subject, biopsies demonstrating normal parenchyma were felt sufficient to exclude diffuse lung disease as a cause of dyspnea. The overall diagnostic yield of bronchoscopic cryobiopsy was 80% (20/25). The most frequent diagnosis was usual interstitial pneumonia (UIP) (n = 7). Three of the 25 subjects ultimately required surgical lung biopsy. There were no significant complications.
In patients with suspected diffuse parenchymal lung disease, bronchoscopic cryobiopsy is a promising and minimally invasive approach to obtain lung tissue with high diagnostic yield.
PLoS ONE 11/2013; 8(11):e78674. · 3.53 Impact Factor
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[Show abstract][Hide abstract] ABSTRACT: The median survival of patients with idiopathic pulmonary fibrosis continues to be approximately 3 years from the time of diagnosis, underscoring the lack of effective medical therapies for this disease. In the United States alone, approximately 40,000 patients die of this disease annually. In November 2012, the National Heart, Lung and Blood Institute held a workshop aimed at coordinating research efforts and accelerating the development of idiopathic pulmonary fibrosis therapies. Basic, translational and clinical researchers gathered with representatives from the National Heart Lung and Blood Institute, patient advocacy groups, pharmaceutical companies and the Food and Drug Administration to review the current state of idiopathic pulmonary fibrosis research and identify priority areas, opportunities for collaborations and directions for future research. The workshop was organized into groups that were tasked with assessing and making recommendations to promote progress in one of the following six critical areas of research: 1) biology of alveolar epithelial injury and aberrant repair, 2) role of extracellular matrix, 3) preclinical modeling, 4) the role of inflammation and immunity, 5) genetic, epigenetic and environmental determinants, 6) translation of discoveries into diagnostics and therapeutics. The workshop recommendations provide a basis for directing future research and strategic planning by scientific, professional and patient communities and the National Heart Lung and Blood Institute.
American Journal of Respiratory and Critical Care Medicine 10/2013; · 11.04 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: PGI2 signaling through IP inhibits allergen-induced inflammatory responses in mice. We reported previously that PGI2 analogs decreased proinflammatory cytokine and chemokine production by mature BMDCs. However, whether PGI2 modulates the function of immature DCs has not been investigated. We hypothesized that PGI2 negatively regulates immature DC function and investigated the effect of PGI2 analogs on immature BMDC antigen uptake and migration in vitro and in vivo. Immature BMDCs were obtained from WT and IPKO mice, both on a C57BL/6 background. The PGI2 analog cicaprost decreased FITC-OVA uptake by immature BMDCs. In addition, cicaprost increased immature BMDC podosome dissolution, pro-MMP-9 production, cell surface CCR7 expression, and chemotactic migration toward CCL19 and CCL21, as well as chemokinesis, in an IP-specific fashion. These in vitro results suggested that cicaprost promotes migration of immature DCs from mucosal surface to draining LNs. This concept was supported by the finding that migration of immature GFP(+) BMDCs to draining LNs was enhanced by pretreatment with cicaprost. Further, migration of immature lung DCs labeled with PKH26 was enhanced by intranasal cicaprost administration. Our results suggest PGI2-IP signaling increases immature DC migration to the draining LNs and may represent a novel mechanism by which this eicosanoid inhibits immune responses.
Journal of leukocyte biology 04/2013; · 4.99 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Interstitial lung fibrosis can develop as a consequence of occupational or medical exposures, as a result of genetic defects, following trauma or acute lung injury leading to fibroproliferative acute respiratory distress syndrome (ARDS) or can develop in an idiopathic manner. The pathogenesis of each of these forms of lung fibrosis is poorly understood. They each result in progressive loss of lung function with increasing dyspnea and ultimately, most forms result in mortality. To better understand the pathogenesis of lung fibrotic disorders, multiple animal models have been developed. This review summarizes common and emerging models of lung fibrosis to highlight their usefulness for understanding cell-cell and soluble mediator interactions which drive fibrotic responses. Recent advances have allowed for development of models to study targeted injury of type II alveolar epithelial cells, fibroblast autonomous effects and targeted genetic defects. Repetitive dosing in some models has more closely mimicked the pathology of human fibrotic lung disease. We also have a much better understanding of the fact that the aged lung increases susceptibility to fibrosis. Each of these models reviewed in this report offer a powerful tool to study some aspect of fibrotic lung disease.
American Journal of Respiratory Cell and Molecular Biology 03/2013; · 4.15 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Aquaporin 11 (Aqp11) is a newly described member of the protein family of transport channels. Aqp11 associates with the endoplasmic reticulum (ER) and is highly expressed in proximal tubular epithelial cells in the kidney. Previously, we identified and characterized a recessive mutation of the highly conserved Cys227 to Ser227 in mouse Aqp11 that caused proximal tubule (PT) injury and kidney failure in mutant mice. The current study revealed induction of ER stress, unfolded protein response, and apoptosis as molecular mechanisms of this PT injury. Cys227Ser mutation interfered with maintenance of Aqp11oligomeric structure. Aqp11 is abundantly expressed in the S1 PT segment, a site of major renal glucose flux, and Aqp11 mutant mice developed PT-specific mitochondrial injury. Glucose increased Aqp11 protein expression in wild type kidney and up-regulation of Aqp11 expression by glucose in vitro was prevented by phlorizin, an inhibitor of sodium-dependent glucose transport across PT. Total Aqp11 levels in heterozygotes were higher than in wild type mice but were not further increased in response to glucose. In Aqp11 insufficient PT cells, glucose potentiated increases in reactive oxygen species (ROS) production. ROS production was also elevated in Aqp11 mutation carriers. Phenotypically normal mice heterozygous for the Aqp11 mutation repeatedly treated with glucose showed increased blood urea nitrogen levels that was prevented by the antioxidant sulforaphane or by phlorizin. Our results indicate an important role for Aqp11 to prevent glucose-induced oxidative stress in proximal tubules.
[Show abstract][Hide abstract] ABSTRACT: RATIONALE: Alveolar epithelial cells (AECs) play central roles in the response to lung injury and the pathogenesis of pulmonary fibrosis. OBJECTIVES: We aimed to determine the role of β-catenin in alveolar epithelium during bleomycin induced lung fibrosis. METHODS: Genetically modified mice were developed to selectively delete β-catenin in AECs and were crossed to cell fate reporter mice that express β-galactosidase (βgal) in cells of AEC lineage. Mice were given intratracheal bleomycin (0.04 units) and assessed for AEC death, inflammation, lung injury, and fibrotic remodeling. Mouse lung epithelial cells (MLE12) with siRNA knockdown of β-catenin underwent evaluation for wound closure, proliferation, and bleomycin induced cytotoxicity. MEASUREMENTS AND MAIN RESULTS: Increased β-catenin expression was noted in lung parenchyma following bleomycin. Mice with selective deletion of β-catenin in AECS had greater AEC death at 1 week following bleomycin, followed by increased numbers of fibroblasts and enhanced lung fibrosis as determined by semiquantitative histological scoring and total collagen content. However, no differences in lung inflammation or protein levels in bronchoalveolar lavage were noted. In vitro, β-catenin deficient AECs showed increased bleomycin induced cytotoxicity, as well as reduced proliferation and impaired wound closure. Consistent with these findings, mice with AEC β-catenin deficiency showed delayed recovery after bleomycin. CONCLUSIONS: β-catenin in the alveolar epithelium protects against bleomycin induced fibrosis. Our studies suggest that AEC survival and wound healing are enhanced through β-catenin dependent mechanisms. Activation of the developmentally important β-catenin pathway in AECs appears to contribute to epithelial repair following epithelial injury.
American Journal of Respiratory and Critical Care Medicine 01/2013; · 11.04 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Idiopathic pulmonary fibrosis (IPF) is a progressive and often fatal lung disease for which there is no known treatment. Although the traditional paradigm of IPF pathogenesis emphasized chronic inflammation as the primary driver of fibrotic remodeling, more recent insights have challenged this view. Linkage analysis and candidate gene approaches have identified four genes that cause the inherited form of IPF, familial interstitial pneumonia (FIP). These four genes encode two surfactant proteins, surfactant protein C (encoded by SFTPC) and surfactant protein A2 (SFTPA2), and two components of the telomerase complex, telomerase reverse transcriptase (TERT) and the RNA component of telomerase (TERC). In this review, we discuss how investigating these mutations, as well as genetic variants identified in other inherited disorders associated with pulmonary fibrosis, are providing new insights into the pathogenesis of common idiopathic interstitial lung diseases, particularly IPF. Studies in this area have highlighted key roles for epithelial cell injury and dysfunction in the development of lung fibrosis. In addition, genetic approaches have uncovered the importance of several processes - including endoplasmic reticulum stress and the unfolded protein response, DNA-damage and -repair pathways, and cellular senescence - that might provide new therapeutic targets in fibrotic lung diseases.
Disease Models and Mechanisms 01/2013; 6(1):9-17. · 4.96 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Current evidence suggests a prominent role for endoplasmic reticulum (ER) stress and activation of the unfolded protein response (UPR) in fibrotic conditions affecting a number of internal organs, including the lungs, liver, GI tract, kidney, and heart. ER stress enhances the susceptibility of structural cells, in most cases the epithelium, to pro-fibrotic stimuli. Studies suggest that ER stress facilitates fibrotic remodeling through activation of pro-apoptotic pathways, induction of epithelial-mesenchymal transition, and promotion of inflammatory responses. While genetic mutations that lead to ER stress underlie some cases of fibrosis, including lung fibrosis secondary to mutations in surfactant protein C (SFTPC), a variety of other factors can cause ER stress. These ER stress inducing factors include metabolic abnormalities, oxidative stress, viruses, and environmental exposures. Interestingly, the ability of the ER to maintain homeostasis under stress diminishes with age, potentially contributing to the fact that fibrotic disorders increase in incidence with aging. Taken together, underlying ER stress and UPR pathways are emerging as important determinants of fibrotic remodeling in different forms of tissue fibrosis. Further work is needed to better define the mechanisms by which ER stress facilitates progressive tissue fibrosis. In addition, it remains to be seen whether targeting ER stress and the UPR could have therapeutic benefit. This article is part of a Special Issue entitled: Fibrosis: Translation of basic research to human disease.
Biochimica et Biophysica Acta 11/2012; · 4.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: Systemic blockade of tissue factor (TF) attenuates acute lung injury (ALI) in animal models of sepsis but the effects of global TF deficiency are unknown. We used mice with complete knockout of mouse TF and low levels (∼1%) of human TF (LTF mice) to test the hypothesis that global TF deficiency attenuates lung inflammation in direct lung injury. METHODS: LTF mice were treated with 10 μg of lipopolysaccharide (LPS) or vehicle administered by direct intratracheal injection and studied at 24 h. RESULTS: Contrary to our hypothesis, LTF mice had increased lung inflammation and injury as measured by bronchoalveolar lavage cell count (3.4×10(5) wild-type (WT) LPS vs 3.3×10(5) LTF LPS, p=0.947) and protein (493 μg/ml WT LPS vs 1014 μg/ml LTF LPS, p=0.006), proinflammatory cytokines (TNF-α, IL-10, IL-12, p<0.035 WT LPS vs LTF LPS) and histology compared with WT mice. LTF mice also had increased haemorrhage and free haemoglobin in the airspace accompanied by increased oxidant stress as measured by lipid peroxidation products (F(2) isoprostanes and isofurans). CONCLUSIONS: These findings indicate that global TF deficiency does not confer protection in a direct lung injury model. Rather, TF deficiency causes increased intra-alveolar haemorrhage following LPS leading to increased lipid peroxidation. Strategies to globally inhibit TF may be deleterious in patients with ALI.
[Show abstract][Hide abstract] ABSTRACT: In addition to parenchymal fibrosis, fibrotic remodeling of the distal airways has been reported in interstitial lung diseases. Mechanisms of airway wall remodeling, which occurs in a variety of chronic lung diseases, are not well defined and current animal models are limited. The authors quantified airway remodeling in lung sections from subjects with idiopathic pulmonary fibrosis (IPF) and controls. To investigate intratracheal bleomycin as a potential animal model for fibrotic airway remodeling, the authors evaluated lungs from C57BL/6 mice after bleomycin treatment by histologic scoring for fibrosis and peribronchial inflammation, morphometric evaluation of subepithelial connective tissue volume density, TUNEL (terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling) assay, and immunohistochemistry for transforming growth factor β1 (TGFβ1), TGFβ2, and the fibroblast marker S100A4. Lung mechanics were determined at 3 weeks post bleomycin. IPF lungs had small airway remodeling with increased bronchial wall thickness compared to controls. Similarly, bleomycin-treated mice developed dose-dependent airway wall inflammation and fibrosis and greater airflow resistance after high-dose bleomycin. Increased TUNEL(+) bronchial epithelial cells and peribronchial inflammation were noted by 1 week, and expression of TGFβ1 and TGFβ2 and accumulation of S100A4(+) fibroblasts correlated with airway remodeling in a bleomycin dose-dependent fashion. IPF is characterized by small airway remodeling in addition to parenchymal fibrosis, a pattern also seen with intratracheal bleomycin. Bronchial remodeling from intratracheal bleomycin follows a cascade of events including epithelial cell injury, airway inflammation, profibrotic cytokine expression, fibroblast accumulation, and peribronchial fibrosis. Thus, this model can be utilized to investigate mechanisms of airway remodeling.
Experimental Lung Research 04/2012; 38(3):135-46. · 1.75 Impact Factor