Fibrotic lung diseases in children

In children, pulmonary fibrosis (PF) is an extremely unusual entity that can be observed in some types of interstitial lung disease (ILD). Defining whether ILD is accompanied by PF is important for targeted therapy. Algorithm for the diagnosis of PF in children is not clearly established. Besides, the clinical, radiological, and histological definitions commonly used to diagnose particularly the cases of idiopathic PF in adult patients, is not applicable to pediatric cases. However, a few studies conducted in children offer good exemplary diagnostic approach to fibrosing ILD. Thorax high resonance computed tomography and/or lung biopsy scanning can provide valuable information about PF. Another issue that has not been clearly established is when to start antifibrotic treatment in pediatric patients with PF. The objective of this current review is to provide a comprehensive overview of pediatric PF by drawing upon adult research, particularly focusing on the areas of uncertainty.

Study on Potential Differentially Expressed Genes in Idiopathic Pulmonary Fibrosis by Bioinformatics and Next-Generation Sequencing Data Analysis

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive lung disease with reduced quality of life and earlier mortality, but its pathogenesis and key genes are still unclear. In this investigation, bioinformatics was used to deeply analyze the pathogenesis of IPF and related key genes, so as to investigate the potential molecular pathogenesis of IPF and provide guidance for clinical treatment. Next-generation sequencing dataset GSE213001 was obtained from Gene Expression Omnibus (GEO), and the differentially expressed genes (DEGs) were identified between IPF and normal control group. The DEGs between IPF and normal control group were screened with the DESeq2 package of R language. The Gene Ontology (GO) and REACTOME pathway enrichment analyses of the DEGs were performed. Using the g:Profiler, the function and pathway enrichment analyses of DEGs were performed. Then, a protein-protein interaction (PPI) network was constructed via the Integrated Interactions Database (IID) database. Cytoscape with Network Analyzer was used to identify the hub genes. miRNet and NetworkAnalyst databaseswereused to construct the targeted microRNAs (miRNAs), transcription factors (TFs), and small drug molecules. Finally, receiver operating characteristic (ROC) curve analysis was used to validate the hub genes. A total of 958 DEGs were screened out in this study, including 479 up regulated genes and 479 down regulated genes. Most of the DEGs were significantly enriched in response to stimulus, GPCR ligand binding, microtubule-based process, and defective GALNT3 causes HFTC. In combination with the results of the PPI network, miRNA-hub gene regulatory network and TF-hub gene regulatory network, hub genes including LRRK2, BMI1, EBP, MNDA, KBTBD7, KRT15, OTX1, TEKT4, SPAG8, and EFHC2 were selected. Cyclothiazide and rotigotinethe are predicted small drug molecules for IPF treatment. Our findings will contribute to identification of potential biomarkers and novel strategies for the treatment of IPF, and provide a novel strategy for clinical therapy.

Lung biopsy in the diagnosis and management of chILD

Children's interstitial and diffuse lung disease (chILD) comprises a large number of diverse entities ranging from disorders of lung development, maturation and function unique in infancy to immune-mediated, environmental, vascular and other conditions overlapping with adult disease. Pathologic evaluation of the lung has played a central role in characterizing many of these disorders, resulting in revised nomenclature and classifications to help guide clinical management(1-4). Technological advancements are rapidly uncovering genetic and molecular underpinnings of these conditions, as well as widening the phenotypes which bridge adult disease, often reducing the perceived need for diagnostic lung biopsy. As such the decision to get a lung biopsy in chILD is frequently for rapid ascertainment of disease in a critically ill child or when clinical presentation, imaging and laboratory studies fail to provide a cohesive diagnosis needed for treatment. While there have been modifications in surgical procedures for lung biopsy that minimize postoperative morbidity, it remains a high-risk invasive procedure, especially in a medically complex patient(5). Thus, it is essential that the lung biopsy be handled properly to maximize diagnostic yield, including close communication between the clinician, radiologist, surgeon, and pathologist before biopsy to determine best sampling site(s) and prioritization of tissue utilization. This review provides an overview of optimal handling and evaluation of a surgical lung biopsy for suspected chILD, with emphasis on specific conditions in which pathologic features play a critical role in providing an integrated diagnosis and guiding management.

European Respiratory Society statement on familial pulmonary fibrosis

Genetic predisposition to pulmonary fibrosis has been confirmed by the discovery of several gene mutations that cause pulmonary fibrosis. Although genetic sequencing of familial pulmonary fibrosis (FPF) cases is embedded in routine clinical practice in several countries, many centres have yet to incorporate genetic sequencing within interstitial lung disease (ILD) services and proper international consensus has not yet been established. An international and multidisciplinary expert Task Force (pulmonologists, geneticists, paediatrician, pathologist, genetic counsellor, patient representative and librarian) reviewed the literature between 1945 and 2022, and reached consensus for all of the following questions: 1) Which patients may benefit from genetic sequencing and clinical counselling? 2) What is known of the natural history of FPF? 3) Which genes are usually tested? 4) What is the evidence for telomere length measurement? 5) What is the role of common genetic variants (polymorphisms) in the diagnostic workup? 6) What are the optimal treatment options for FPF? 7) Which family members are eligible for genetic sequencing? 8) Which clinical screening and follow-up parameters may be considered in family members? Through a robust review of the literature, the Task Force offers a statement on genetic sequencing, clinical management and screening of patients with FPF and their relatives. This proposal may serve as a basis for a prospective evaluation and future international recommendations.

ABCA3

BACKGROUND

The majority of patients with childhood interstitial lung disease (chILD) caused by pathogenic variants in ATP binding cassette subfamily A member 3 (ABCA3) develop severe respiratory insufficiency within their first year of life and succumb to disease if not lung transplanted. This register-based cohort study reviews patients with ABCA3 lung disease who survived beyond the age of 1 year.

METHOD

Over a 21-year period, patients diagnosed as chILD due to ABCA3 deficiency were identified from the Kids Lung Register database. 44 patients survived beyond the first year of life and their long-term clinical course, oxygen supplementation and pulmonary function were reviewed. Chest CT and histopathology were scored blindly.

RESULTS

At the end of the observation period, median age was 6.3 years (IQR: 2.8-11.7) and 36/44 (82%) were still alive without transplantation. Patients who had never received supplemental oxygen therapy survived longer than those persistently required oxygen supplementation (9.7 (95% CI 6.7 to 27.7) vs 3.0 years (95% CI 1.5 to 5.0), p=0.0126). Interstitial lung disease was clearly progressive over time based on lung function (forced vital capacity % predicted absolute loss -1.1% /year) and on chest CT (increasing cystic lesions in those with repetitive imaging). Lung histology pattern were variable (chronic pneumonitis of infancy, non-specific interstitial pneumonia, and desquamative interstitial pneumonia). In 37/44 subjects, the ABCA3 sequence variants were missense variants, small insertions or deletions with in-silico tools predicting some residual ABCA3 transporter function.

CONCLUSION

The natural history of ABCA3-related interstitial lung disease progresses during childhood and adolescence. Disease-modifying treatments are desirable to delay such disease course.

Idiopathic pulmonary fibrosis and the role of genetics in the era of precision medicine

Idiopathic pulmonary fibrosis (IPF) is a chronic, rare progressive lung disease, characterized by lung scarring and the irreversible loss of lung function. Two anti-fibrotic drugs, nintedanib and pirfenidone, have been demonstrated to slow down disease progression, although IPF mortality remains a challenge and the patients die after a few years from diagnosis. Rare pathogenic variants in genes that are involved in the surfactant metabolism and telomere maintenance, among others, have a high penetrance and tend to co-segregate with the disease in families. Common recurrent variants in the population with modest effect sizes have been also associated with the disease risk and progression. Genome-wide association studies (GWAS) support at least 23 genetic risk loci, linking the disease pathogenesis with unexpected molecular pathways including cellular adhesion and signaling, wound healing, barrier function, airway clearance, and innate immunity and host defense, besides the surfactant metabolism and telomere biology. As the cost of high-throughput genomic technologies continuously decreases and new technologies and approaches arise, their widespread use by clinicians and researchers is efficiently contributing to a better understanding of the pathogenesis of progressive pulmonary fibrosis. Here we provide an overview of the genetic factors known to be involved in IPF pathogenesis and discuss how they will continue to further advance in this field. We also discuss how genomic technologies could help to further improve IPF diagnosis and prognosis as well as for assessing genetic risk in unaffected relatives. The development and validation of evidence-based guidelines for genetic-based screening of IPF will allow redefining and classifying this disease relying on molecular characteristics and contribute to the implementation of precision medicine approaches.

Insights into the Pathogenesis of Pulmonary Fibrosis from Genetic Diseases

Pulmonary fibrosis is a disease process associated with significant morbidity and mortality, with limited therapeutic options owing to an incomplete understanding of the underlying pathophysiology. Mechanisms driving the fibrotic cascade have been elucidated through studies of rare and common variants in surfactant-related and telomere-related genes in familial and sporadic forms of pulmonary fibrosis, as well as in multisystem Mendelian genetic disorders that present with pulmonary fibrosis. In this translational review, we outline insights into the pathophysiology of pulmonary fibrosis derived from genetic forms of the disease, with a focus on model systems, shared cellular and molecular mechanisms, and potential targets for therapy.

Hydroxychloroquine, a successful treatment for lung disease in ABCA3 deficiency gene mutation: a case report

Background

Pulmonary surfactant is a complex mixture of lipids and specific proteins that stabilizes the alveoli at the end of expiration. Mutations in the gene coding for the triphosphate binding cassette transporter A3 (ABCA3), which facilitates the transfer of lipids to lamellar bodies, constitute the most frequent genetic cause of severe neonatal respiratory distress syndrome and chronic interstitial lung disease in children. Hydroxychloroquine can be used as an effective treatment for this rare severe condition.

Case presentation

We report a late preterm Bosnian baby boy (36 weeks) who suffered from a severe form of respiratory distress syndrome with poor response to intensive conventional management and whole exome sequencing revealed homozygous ABCA3 mis-sense mutation. The baby showed remarkable improvement of the respiratory condition after the initiation of Hydroxychloroquine, Azithromycin and Corticosteroids with the continuation of Hydroxychloroquine as a monotherapy till after discharge from the hospital.

Conclusion

Outcome in patients with ABCA3 mutations is variable ranging from severe irreversible respiratory failure in early infancy to chronic interstitial lung disease in childhood (ChILD) usually with the need for lung transplantation in many patients surviving this rare disorder. Hydroxychloroquine through its anti-inflammatory effects or alteration of intra-cellular metabolism may have an effect in treating cases of ABCA3 gene mutations.

Fibrosing pneumonia – how to diagnose, and how to recognize the etiology?

Background

Fibrosing pneumonias are a group of interstitial lung diseases with a different etiologic background and divergent prognosis. They are differentiated into usual interstitial pneumonia (UIP), non-specific interstitial pneumonia (NSIP), and organizing pneumonia (OP). Some of these entities were initially described by A. Liebow.

Main

In the 90ties the main differences in survival lead to the separation of UIP/IPF as a disease with dismal outcome, from the prognostically better NSIP and OP. Later it was shown that fibrosing NSIP confers an almost identical worse prognosis. Under the heading of pulmologists a classification was created, where the diagnosis has to be established by a multidisciplinary team, based on pattern recognition done by radiologists and pathologists. A clinical diagnosis has to be established based on the patterns: UIP pattern was the basis for IPF, NSIP pattern for the clinical diagnosis NSIP, and organizing pneumonia pattern for the diagnosis of cryptogenic organizing pneumonia. This created confusion, because the pattern UIP was taken almost as synonymous with idiopathic pulmonary fibrosis (IPF). Later on in many articles and classifications the role of the pathologic diagnosis was diminished, because pulmologists based their diagnosis on CT-scan and clinical presentation. This resulted in less tissue biopsies but also delay and misinterpretation of diseases. Even new techniques in tissue biopsies such as cryobiopsy was regarded as unnecessary.

Conclusion

Tissue analysis in fibrosing pneumonias is still the gold standard in making a diagnosis and also evaluating the etiologic background. After an analysis the findings should be discussed in a multidisciplinary board to establish a final diagnosis and a treatment option for the patient.

Impact of genetic factors on fibrosing interstitial lung diseases. Incidence and clinical presentation in adults

At least 10% of patients with pulmonary fibrosis, whether idiopathic or secondary, present heritable pulmonary fibrosis suspected on familial aggregation of pulmonary fibrosis, specific syndromes or early age of diagnosis. Approximately 30% of those patients have an identified mutation mostly in telomere related genes (TRG) more rarely in surfactant homeostasis or other genes. TRG mutation may be associated with hematological and hepatic diseases that may worsen after lung transplantation requiring a specific care and adapted immunosuppression. Surfactant genes mutations are usually associated with ground-glass opacities and cysts on CT scan and may improve with steroids, hydroxychloroquine or azithromycin. Moreover relatives should benefit from a genetic analysis associated with a clinical evaluation according to the gene involved. Genetics of pulmonary fibrosis raise specific problems from diagnosis, therapy or genetic counseling varying from one gene to another.

Approaching Clinical Trials in Childhood Interstitial Lung Disease and Pediatric Pulmonary Fibrosis

Childhood interstitial lung disease (chILD) comprises a spectrum of rare diffuse lung disorders. chILD is heterogeneous in origin, with different disease manifestations occurring in the context of ongoing lung development. The large number of disorders in chILD, in combination with the rarity of each diagnosis, has hampered scientific and clinical progress within the field. Epidemiologic and natural history data are limited. The prognosis varies depending on the etiology, with some forms progressing to lung transplant or death. There are limited treatment options for patients with chILD. Although U.S. Food and Drug Administration-approved treatments are now available for adult patients with idiopathic pulmonary fibrosis, no clinical trials have been conducted in a pediatric population using agents designed to treat lung fibrosis. This review will focus on progressive chILD disorders and on the urgent need for meaningful objective outcome measures to define, detect, and monitor fibrosis in children.

The genetics of interstitial lung diseases

Interstitial lung diseases (ILDs) are a set of heterogeneous lung diseases characterised by inflammation and, in some cases, fibrosis. These lung conditions lead to dyspnoea, cough, abnormalities in gas exchange, restrictive physiology (characterised by decreased lung volumes), hypoxaemia and, if progressive, respiratory failure. In some cases, ILDs can be caused by systemic diseases or environmental exposures. The ability to treat or cure these ILDs varies based on the subtype and in many cases lung transplantation remains the only curative therapy. There is a growing body of evidence that both common and rare genetic variants contribute to the development and clinical manifestation of many of the ILDs. Here, we review the current understanding of genetic risk and ILD.

Common and rare genetic variants contribute to the development and clinical manifestation of many interstitial lung diseaseshttp://bit.ly/31loHLh

Abandoning developmental silos: what can paediatricians and adult interstitial lung disease physicians learn from each other?

PURPOSE OF REVIEW

Interstitial lung disease (ILD) consists of a large and heterogeneous group of disorders that are classified together because of similar clinical, radiographic, physiologic or pathologic manifestations. Overall, although there is overlap between adult and childhood ILD (chILD), there are many differences in disease causes and prevalences.

RECENT FINDINGS

In the last few years, our understanding of adult ILD pathobiology has improved substantially. This is particularly true for idiopathic pulmonary fibrosis, the most common of the idiopathic interstitial pneumonias, wherein recently developed guideline documents provide recommendations for the diagnosis and clinical management of patients. For chILD, similar guidelines are yet to be developed. However, complications and long-term pulmonary outcomes of paediatric disease are better appreciated, which make the implementation of a successful transition program from paediatric to adult care an urgent need. Similarly important is the development of guidelines on performance and interpretation of genetic testing in affected and unaffected relatives of familial cases and in children of adult-onset ILD patients. Lung transplantation appears to be as successful as in adult patients for end-stage disease. Paediatric pulmonologists should engage with the adult multidisciplinary teams and benefit from their much more extensive experience.

SUMMARY

Childhood and adult ILD share a number of aspects, which give children and adult ILD specialists exciting opportunities to collaborate and learn from each other. Such collaborative effort between child and adult ILD experts is crucial for successful future development in the field.

Translational research in pulmonary fibrosis

Pulmonary fibrosis refers to the development of diffuse parenchymal abnormalities in the lung that cause dyspnea, cough, hypoxemia, and impair gas exchange, ultimately leading to respiratory failure. Though pulmonary fibrosis can be caused by a variety of underlying etiologies, ranging from genetic defects to autoimmune diseases to environmental exposures, once fibrosis develops it is irreversible and most often progressive, such that fibrosis of the lung is one of the leading indications for lung transplantation. This review aims to provide a concise summary of the recent advances in our understanding of the genetics and genomics of pulmonary fibrosis, idiopathic pulmonary fibrosis in particular, and how these recent discoveries may be changing the clinical approach to diagnosing and treating patients with fibrotic interstitial lung disease.

Idiopathic pulmonary fibrosis: Epithelial-mesenchymal interactions and emerging therapeutic targets

Idiopathic pulmonary fibrosis (IPF) is a chronic fibrotic disease of the lung that is marked by progressive decline in pulmonary function and ultimately respiratory failure. Genetic and environmental risk factors have been identified that indicate injury to, and dysfunction of the lung epithelium is central to initiating the pathogenic process. Following injury to the lung epithelium, growth factors, matrikines and extracellular matrix driven signaling together activate a variety of repair pathways that lead to inflammatory cell recruitment, fibroblast proliferation and expansion of the extracellular matrix, culminating in tissue fibrosis. This tissue fibrosis then leads to changes in the biochemical and biomechanical properties of the extracellular matrix, which potentiate profibrotic mechanisms through a "feed-forward cycle." This review provides an overview of the interactions of the pathogenic mechanisms of IPF with a focus on epithelial-mesenchymal crosstalk and the extracellular matrix as a therapeutic target for idiopathic pulmonary fibrosis.

Personalised medicine in interstitial lung diseases

Interstitial lung diseases in general, and idiopathic pulmonary fibrosis in particular, are complex disorders with multiple pathogenetic pathways, various disease behaviour profiles and different responses to treatment, all facets that make personalised medicine a highly attractive concept. Personalised medicine is aimed at describing distinct disease subsets taking into account individual lifestyle, environmental exposures, genetic profiles and molecular pathways. The cornerstone of personalised medicine is the identification of biomarkers that can be used to inform diagnosis, prognosis and treatment stratification. At present, no data exist validating a personalised approach in individual diseases. However, the importance of the goal amply justifies the characterisation of genotype and pathway signatures with a view to refining prognostic evaluation and trial design, with the ultimate aim of selecting treatments according to profiles in individual patients.

Hermansky-Pudlak syndrome type 2 manifests with fibrosing lung disease early in childhood

Background

Hermansky-Pudlak syndrome (HPS), a hereditary multisystem disorder with oculocutaneous albinism, may be caused by mutations in one of at least 10 separate genes. The HPS-2 subtype is distinguished by the presence of neutropenia and knowledge of its pulmonary phenotype in children is scarce.

Methods

Six children with genetically proven HPS-2 presented to the chILD-EU register between 2009 and 2017; the data were collected systematically and imaging studies were scored blinded.

Results

Pulmonary symptoms including dyspnea, coughing, need for oxygen, and clubbing started 3.3 years before the diagnosis was made at the mean age of 8.83 years (range 2-15). All children had recurrent pulmonary infections, 3 had a spontaneous pneumothorax, and 4 developed scoliosis. The frequency of pulmonary complaints increased over time. The leading radiographic pattern was ground-glass opacities with a rapid increase in reticular pattern and traction bronchiectasis between initial and follow-up Computer tomography (CT) in all subjects. Honeycombing and cysts were newly detectable in 3 patients. Half of the patients received a lung biopsy for diagnosis; histological patterns were cellular non-specific interstitial pneumonia, usual interstitial pneumonia-like, and desquamative interstitial pneumonia.

Conclusions

HPS-2 is characterized by a rapidly fibrosing lung disease during early childhood. Effective treatments are required.

Electronic supplementary material

The online version of this article (10.1186/s13023-018-0780-z) contains supplementary material, which is available to authorized users.

Role of miR-34a in TGF-β1- and Drug-Induced Epithelial-Mesenchymal Transition in Alveolar Type II Epithelial Cells

Epithelial-mesenchymal transition (EMT) of alveolar type II epithelial cells may play an important role in the pulmonary fibrosis induced by drugs such as bleomycin (BLM) and methotrexate (MTX). In this study, we examined the role of microRNAs (miRNAs) in drug-induced EMT using RLE/Abca3, a cell line having alveolar type II cell-like phenotype. Based on the screening using miRNA microarray analysis, it was found that the expression of some miRNAs, such as miR-34a, was increased by transforming growth factor (TGF)-β1 and BLM. An increase in miR-34a expression due to TGF-β1, BLM, and MTX was also observed in real-time PCR analysis. Therefore, miR-34a was focused upon in further studies. The expression of nectin-1 mRNA and protein, a possible target of miR-34a, was decreased by the treatment with TGF-β1, BLM, and MTX. In addition, when RLE/Abca3 cells were transfected with miR-34a mimic, the expression of nectin-1 mRNA and Abca3 mRNA, another target of miR34a, decreased significantly. Furthermore, the mRNA expression of cytokeratin 19, an epithelial marker, decreased, whereas that of α-smooth muscle actin, a mesenchymal marker, increased in the cells transfected with miR-34a mimic. These results suggest that miR-34a is involved in drug-induced EMT in alveolar epithelial cells, and possibly in lung fibrosis.

The biology of the ABCA3 lipid transporter in lung health and disease

The lipid transporter, ATP-binding cassette class A3 (ABCA3), is a highly conserved multi-membrane-spanning protein that plays a critical role in the regulation of pulmonary surfactant homeostasis. Mutations in ABCA3 have been increasingly recognized as one of the causes of inherited pulmonary diseases. These monogenic disorders produce familial lung abnormalities with pathological presentations ranging from neonatal surfactant-deficiency-induced respiratory failure to childhood or adult diffuse parenchymal lung diseases for which specific treatment modalities remain limited. More than 200 ABCA3 mutations have been reported to date with approximately three quarters of patients presenting as compound heterozygotes. Recent advances in our understanding of the molecular basis underlying normal ABCA3 biosynthesis and processing and of the mechanisms of alveolar epithelial cell dysregulation caused by the expression of its mutant forms are beginning to emerge. These insights and the role of environmental factors and modifier genes are discussed in the context of the considerable variability in disease presentation observed in patients with identical ABCA3 gene mutations. Moreover, the opportunities afforded by an enhanced understanding of ABCA3 biology for targeted therapeutic strategies are addressed.

Tissue remodelling in pulmonary fibrosis

Many lung diseases result in fibrotic remodelling. Fibrotic lung disorders can be divided into diseases with known and unknown aetiology. Among those with unknown aetiology, idiopathic pulmonary fibrosis (IPF) is a common diagnosis. Because of its progressive character leading to a rapid decline in lung function, it is a fatal disease with poor prognosis and limited therapeutic options. Thus, IPF has motivated many studies in the last few decades in order to increase our mechanistic understanding of the pathogenesis of the disease. The current concept suggests an ongoing injury of the alveolar epithelium, an impaired regeneration capacity, alveolar collapse and, finally, a fibroproliferative response. The origin of lung injury remains elusive but a diversity of factors, which will be discussed in this article, has been shown to be associated with IPF. Alveolar epithelial type II (AE2) cells play a key role in lung fibrosis and their crucial role for epithelial regeneration, stabilisation of alveoli and interaction with fibroblasts, all known to be responsible for collagen deposition, will be illustrated. Whereas mechanisms of collagen deposition and fibroproliferation are the focus of many studies in the field, the awareness of other mechanisms in this disease is currently limited to biochemical and imaging studies including quantitative assessments of lung structure in IPF and animal models assigning alveolar collapse and collapse induration crucial roles for the degradation of the lung resulting in de-aeration and loss of surface area. Dysfunctional AE2 cells, instable alveoli and mechanical stress trigger remodelling that consists of collapsed alveoli absorbed by fibrotic tissue (i.e., collapse induration).

Fatal respiratory disease due to a homozygous intronic ABCA3 mutation: a case report

Background

Pulmonary surfactant is a complex mixture of lipids and proteins. Mutations in surfactant protein-C, surfactant protein-D, and adenosine triphosphate-binding cassette subfamily A member 3 have been related to surfactant dysfunction and neonatal respiratory failure in full-term babies. Adenosine triphosphate-binding cassette subfamily A member 3 facilitates the transfer of lipids to lamellar bodies. We report the case of patient with a homozygous intronic ABCA3 mutation.

Case presentation

We describe a newborn full-term Colombian baby boy who was the son of non-consanguineous parents of mixed race ancestry (Mestizo), who was delivered with severe respiratory depression. Invasive treatment was unsuccessful and diagnosis was uncertain. Exons 4 and 5 of the SP-C gene showed heterozygous Thr138Asn polymorphism and homozygous Asn186Asn polymorphism respectively. At intron 25 at position –98 from exon 26 a homozygous C>T transition mutation was detected in ABCA3 gene.

Conclusions

The clinical presentation and the histopathological findings of this case are consistent with a case of neonatal respiratory failure due to surfactant deficiency. Analysis of the five coding SP-C exons does not support surfactant deficiency. An analysis of the mutation IVS25-98 T was performed and a homozygous mutation responsible for our case’s neonatal respiratory failure was detected. The findings suggest an autosomic recessive pattern of inheritance. Genetic counseling was provided and the relatives are now informed of the recurrence risks and treatment options.

Diffuse Lung Disease in Biopsied Children 2 to 18 Years of Age. Application of the chILD Classification Scheme

RATIONALE

Children's Interstitial and Diffuse Lung Disease (chILD) is a heterogeneous group of disorders that is challenging to categorize. In previous study, a classification scheme was successfully applied to children 0 to 2 years of age who underwent lung biopsies for chILD. This classification scheme has not been evaluated in children 2 to 18 years of age.

OBJECTIVES

This multicenter interdisciplinary study sought to describe the spectrum of biopsy-proven chILD in North America and to apply a previously reported classification scheme in children 2 to 18 years of age. Mortality and risk factors for mortality were also assessed.

METHODS

Patients 2 to 18 years of age who underwent lung biopsies for diffuse lung disease from 12 North American institutions were included. Demographic and clinical data were collected and described. The lung biopsies were reviewed by pediatric lung pathologists with expertise in diffuse lung disease and were classified by the chILD classification scheme. Logistic regression was used to determine risk factors for mortality.

MEASUREMENTS AND MAIN RESULTS

A total of 191 cases were included in the final analysis. Number of biopsies varied by center (5-49 biopsies; mean, 15.8) and by age (2-18 yr; mean, 10.6 yr). The most common classification category in this cohort was Disorders of the Immunocompromised Host (40.8%), and the least common was Disorders of Infancy (4.7%). Immunocompromised patients suffered the highest mortality (52.8%). Additional associations with mortality included mechanical ventilation, worse clinical status at time of biopsy, tachypnea, hemoptysis, and crackles. Pulmonary hypertension was found to be a risk factor for mortality but only in the immunocompetent patients.

CONCLUSIONS

In patients 2 to 18 years of age who underwent lung biopsies for diffuse lung disease, there were far fewer diagnoses prevalent in infancy and more overlap with adult diagnoses. Immunocompromised patients with diffuse lung disease who underwent lung biopsies had less than 50% survival at time of last follow-up.

Breakdown of Epithelial Barrier Integrity and Overdrive Activation of Alveolar Epithelial Cells in the Pathogenesis of Acute Respiratory Distress Syndrome and Lung Fibrosis

Individual alveolar epithelial cells (AECs) collaboratively form a tight barrier between atmosphere and fluid-filled tissue to enable normal gas exchange. The tight junctions of AECs provide intercellular sealing and are integral to the maintenance of the AEC barrier integrity. Disruption and failure of reconstitution of AEC barrier result in catastrophic consequences, leading to alveolar flooding and subsequent devastating fibrotic scarring. Recent evidences reveal that many of the fibrotic lung diseases involve AECs both as a frequent target of injury and as a driver of ongoing pathological processes. Aberrantly activated AECs express most of the growth factors and chemokines responsible for the proliferation, migration, and activation of fibroblasts. Current evidences suggest that AECs may acquire overdrive activation in the initial step of fibrosis by several mechanisms, including abnormal recapitulation of the developmental pathway, defects of the molecules essential for epithelial integrity, and acceleration of aging-related properties. Among these initial triggering events, epithelial Pten, a multiple phosphatase that negatively regulates the PI3K/Akt pathway and is crucial for lung development, is essential for the prevention of alveolar flooding and lung fibrosis through the regulation of AEC barrier integrity after injury. Reestablishment of AEC barrier integrity also involves the deployment of specialized stem/progenitor cells.

Diseases of pulmonary surfactant homeostasis

Advances in physiology and biochemistry have provided fundamental insights into the role of pulmonary surfactant in the pathogenesis and treatment of preterm infants with respiratory distress syndrome. Identification of the surfactant proteins, lipid transporters, and transcriptional networks regulating their expression has provided the tools and insights needed to discern the molecular and cellular processes regulating the production and function of pulmonary surfactant prior to and after birth. Mutations in genes regulating surfactant homeostasis have been associated with severe lung disease in neonates and older infants. Biophysical and transgenic mouse models have provided insight into the mechanisms underlying surfactant protein and alveolar homeostasis. These studies have provided the framework for understanding the structure and function of pulmonary surfactant, which has informed understanding of the pathogenesis of diverse pulmonary disorders previously considered idiopathic. This review considers the pulmonary surfactant system and the genetic causes of acute and chronic lung disease caused by disruption of alveolar homeostasis.

ABCA3 protects alveolar epithelial cells against free cholesterol induced cell death

Diffuse parenchymal lung diseases (DPLDs) are characterized by chronic inflammation and fibrotic remodeling of the interstitial tissue. A small fraction of DPLD cases can be genetically defined by mutations in certain genes, with ABCA3 being the gene most commonly affected. However, the pathomechanisms underlying ABCA3-induced DPLD are far from clear. To investigate whether ABCA3 plays a role in cellular cholesterol homeostasis, phospholipids, free cholesterol, and cholesteryl esters were quantified in cells stably expressing ABCA3 using mass spectrometry. Cellular free cholesterol and lipid droplets were visualized by filipin or oil red staining, respectively. Expression of SREBP regulated genes was measured using qPCR. Cell viability was assessed using the XTT assay. We found that wild type ABCA3 reduces cellular free cholesterol levels, induces the SREBP pathway, and renders cells more resistant to loading with exogenous cholesterol. Moreover, ABCA3 mutations found in patients with DPLD interfere with this protective effect of ABCA3, resulting in free cholesterol induced cell death. We conclude that ABCA3 plays a previously unrecognized role in the regulation of cellular cholesterol levels. Accumulation of free cholesterol as a result of a loss of ABCA3 export function represents a novel pathomechanism in ABCA3-induced DPLD.

Clinical and ultrastructural spectrum of diffuse lung disease associated with surfactant protein C mutations

Genetic defects of surfactant metabolism are associated with a broad range of clinical manifestations, from neonatal respiratory distress syndrome to adult interstitial lung disease. Early therapies may improve symptoms but diagnosis is often delayed owing to phenotype and genotype variability. Our objective was to characterize the cellular/ultrastructural correlates of surfactant protein C (SP-C) mutations in children with idiopathic diffuse lung diseases. We sequenced SFTPC - the gene encoding SP-C - SFTPB and ABCA3, and analyzed morphology, ultrastructure and SP expression in lung tissue when available. We identified eight subjects who were heterozygous for SP-C mutations. Median age at onset and clinical course were variable. None of the mutations were located in the mature peptide-encoding region, but were either in the pro-protein BRICHOS or linker C-terminal domains. Although lung morphology was similar to other genetic surfactant metabolism disorders, electron microscopy studies showed specific anomalies, suggesting surfactant homeostasis disruption, plus trafficking defects in the four subjects with linker domain mutation and protein misfolding in the single BRICHOS mutation carrier in whom material was available. Immunolabeling studies showed increased proSP-C staining in all cases. In two cases, amyloid deposits could be identified. Immunochemistry and ultrastructural studies may be useful for diagnostic purposes and for genotype interpretation.

Respiratory failure in a term infant with cis and trans mutations in ABCA3

A full-term female neonate presented with persistent respiratory failure and radiologic studies consistent with surfactant deficiency. Sequencing of the ATP-binding cassette transporter A3 gene (ABCA3) revealed three mutations: R280C, V1399M and Q1589X. The infant underwent bilateral lung transplantation at 9 months of age and is alive at 3 years of age. Parental sequencing demonstrated that two of the mutations (R280C and Q1589X) were oriented on the same allele (cis), whereas V1399M was oriented on the opposite allele (trans). As more than one mutation in ABCA3 can be present on the same allele, parental studies are needed to determine allelic orientation to inform clinical decision making and future reproductive counseling.

Analysis of TGF-β1- and drug-induced epithelial-mesenchymal transition in cultured alveolar epithelial cell line RLE/Abca3

In this study, we examined the induction of epithelial-mesenchymal transition (EMT) by transforming growth factor (TGF)-β1 and drugs in genetically engineered type II alveolar epithelial cell line RLE/Abca3. Treatment of RLE/Abca3 cells with TGF-β1 induced marked changes in cell morphology from epithelial-like to elongated fibroblast-like morphology. With these morphological changes, mRNA expression of epithelial markers such as cytokeratin 19 (CK19) decreased, while that of mesenchymal markers such as α-smooth muscle actin (α-SMA) increased. TGF-β1 treatment also decreased the mRNA expression of Abca3, a type II cell marker, and formation of lamellar body structures. Interestingly, the effect of TGF-β1 on Abca3 mRNA expression was observed in RLE/Abca3 cells, but not in wild-type RLE-6TN, A549, and H441 cells. Treatment of RLE/Abca3 cells with bleomycin (BLM) and methotrexate (MTX) induced similar morphological and mRNA expression changes. In addition, the increase in α-SMA and the decrease in Abca3 mRNA expression by these drugs were observed only in RLE/Abca3 cells. These findings suggest that, like TGF-β1, BLM and MTX induce EMT in RLE/Abca3 cells, and RLE/Abca3 cells would be a good model to study drug-induced EMT. The effect of pirfenidone, an antifibrotic and anti-inflammatory drug, on EMT induced by TGF-β1 was also discussed.

Genotype-phenotype correlations for infants and children with ABCA3 deficiency

RATIONALE

Recessive mutations in the ATP-binding cassette transporter A3 (ABCA3) cause lethal neonatal respiratory failure and childhood interstitial lung disease. Most ABCA3 mutations are private.

OBJECTIVES

To determine genotype-phenotype correlations for recessive ABCA3 mutations.

METHODS

We reviewed all published and unpublished ABCA3 sequence and phenotype data from our prospective genetic studies of symptomatic infants and children at Washington and Johns Hopkins Universities. Mutations were classified based on their predicted disruption of protein function: frameshift and nonsense mutations were classified as "null," whereas missense, predicted splice site mutations, and insertion/deletions were classified as "other." We compared age of presentation and outcomes for the three genotypes: null/null, null/other, and other/other.

MEASUREMENTS AND MAIN RESULTS

We identified 185 infants and children with homozygous or compound heterozygous ABCA3 mutations and lung disease. All of the null/null infants presented with respiratory failure at birth compared with 75% of infants with null/other or other/other genotypes (P = 0.00011). By 1 year of age, all of the null/null infants had died or undergone lung transplantation compared with 62% of the null/other and other/other children (P < 0.0001).

CONCLUSIONS

Genotype-phenotype correlations exist for homozygous or compound heterozygous mutations in ABCA3. Frameshift or nonsense ABCA3 mutations are predictive of neonatal presentation and poor outcome, whereas missense, splice site, and insertion/deletions are less reliably associated with age of presentation and prognosis. Counseling and clinical decision making should acknowledge these correlations.

Interstitial lung disease in children

PURPOSE OF REVIEW

There has been tremendous progress in the approach to childhood interstitial lung diseases (chILD), with particular recognition that interstitial lung disease (ILD) in infants is often distinct from the forms that occur in older children and adults. Diagnosis is challenging because of the rarity of ILD and the fact that the presenting symptoms of ILD often overlap those of common respiratory disorders. This review summarizes the newly published recommendations for diagnosis and management, and highlights the recent scientific advances in several specific forms of chILD.

RECENT FINDINGS

Clinical practice guidelines emphasize the role for chest computed tomography, genetic testing, and lung biopsy in the diagnostic evaluation of children with suspected ILD. Recent studies have better defined the characteristics and molecular understanding of several different forms of ILD, including neuroendocrine cell hyperplasia of infancy and ILD, due to mutations in genes affecting surfactant production and metabolism. Despite significant progress, definitive therapies are often lacking.

SUMMARY

chILD encompasses a collection of rare, diffuse lung diseases. Timely recognition of children with suspected ILD and initiation of appropriate diagnostic evaluations will facilitate medical management. Systematic approaches to clinical care and further studies are needed to improve the outcomes of children with these rare disorders.

Ultrastructural characterization of genetic diffuse lung diseases in infants and children: a cohort study and review

Pediatric diffuse lung diseases are rare disorders with an onset in the neonatal period or in infancy, characterized by chronic respiratory symptoms and diffuse interstitial changes on imaging studies. Genetic disorders of surfactant homeostasis represent the main etiology. Surfactant protein B and ABCA3 deficiencies typically cause neonatal respiratory failure, which is often lethal within a few weeks or months. Although heterozygous ABCA3 mutation carriers are mostly asymptomatic, there is growing evidence that monoallelic mutations may affect surfactant homeostasis. Surfactant protein C mutations are dominant or sporadic disorders leading to a broad spectrum of manifestations from neonatal respiratory distress syndrome to adult pulmonary fibrosis. The authors performed pathology and ultrastructural studies in 12 infants who underwent clinical lung biopsy. One carried a heterozygous SP-B mutation, 3 carried SP-C mutations, and 7 carried ABCA3 mutations (5 biallelic and 2 monoallelic). Optical microscopy made it possible to distinguish between surfactant-related disorders and other forms. One of the ABCA3 monoallelic carriers had morphological features of alveolar capillary dysplasia, a genetic disorder of lung alveolar, and vascular development. One patient showed no surfactant-related anomalies but had pulmonary interstitial glycogenosis, a developmental disorder of unknown origin. Electron microscopy revealed specific lamellar bodies anomalies in all SP-B, SP-C, and ABCA3 deficiency cases. In addition, the authors showed that heterozygous ABCA3 mutation carriers have an intermediate ultrastructural phenotype between homozygous carriers and normal subjects. Lung biopsy is an essential diagnostic procedure in unexplained diffuse lung disorders, and electron microscopy should be performed systematically, since it may reveal specific alterations in genetic disorders of surfactant homeostasis.

A large kindred of pulmonary fibrosis associated with a novel ABCA3 gene variant

Background

Interstitial lung disease occurring in children is a condition characterized by high frequency of cases due to genetic aberrations of pulmonary surfactant homeostasis, that are also believed to be responsible of a fraction of familial pulmonary fibrosis. To our knowledge, ABCA3 gene was not previously reported as causative agent of fibrosis affecting both children and adults in the same kindred.

Methods

We investigated a large kindred in which two members, a girl whose interstitial lung disease was first recognized at age of 13, and an adult, showed a diffuse pulmonary fibrosis with marked differences in terms of morphology and imaging. An additional, asymptomatic family member was detected by genetic analysis. Surfactant abnormalities were investigated at biochemical, and genetic level, as well as by cell transfection experiments.

Results

Bronchoalveolar lavage fluid analysis of the patients revealed absence of surfactant protein C, whereas the gene sequence was normal. By contrast, sequence of the ABCA3 gene showed a novel homozygous G > A transition at nucleotide 2891, localized within exon 21, resulting in a glycine to aspartic acid change at codon 964. Interestingly, the lung specimens from the girl displayed a morphologic usual interstitial pneumonitis-like pattern, whereas the specimens from one of the two adult patients showed rather a non specific interstitial pneumonitis-like pattern.

Conclusions

We have detected a large kindred with a novel ABCA3 mutation likely causing interstitial lung fibrosis affecting either young and adult family members. We suggest that ABCA3 gene should be considered in genetic testing in the occurrence of familial pulmonary fibrosis.

Novel ABCA3 mutations as a cause of respiratory distress in a term newborn

We report here the case of a term female newborn that developed severe respiratory distress soon after birth. She was found to be a compound heterozygote for both novel mutations in the ABCA3 gene. ABCA3 deficiency should be considered in mature babies who develop severe respiratory distress syndrome.

Diffuse lung disease in infancy and childhood: expanding the chILD classification

AIMS

Diffuse parenchymal lung diseases (DPLD) in children comprise a wide spectrum of rare disorders. In 2007 the Children's Interstitial Lung Disease (chILD) Research Cooperative proposed a classification system for DPLD in children <2 years of age. The aims of our study were to determine the utility and reproducibility of this system in children <2 years of age, and test its extension to 18 years of age.

METHODS AND RESULTS

Of 211 cases, 93 were <2 years of age at presentation and 58% were included in the chILD classification. In 118 cases aged between 2 and 18 years there was a wider distribution of disorders, overlapping with those seen in adults, necessitating expansion of the chILD classification types to encompass all reviewed cases, in particular patients with 'adult' diffuse lung diseases. Many cases showed mixed histological patterns, overlap often being between groups of disorders more prevalent in infancy. Concordance between reporting pathologists was 90%.

CONCLUSIONS

The chILD scheme allows classification of conditions more common in children <2 years of age. It can be applied to children of any age, although additional entities need to be included. We propose a more histologically based system for use when assessing biopsies in this context.

Variable clinical outcome of ABCA3 deficiency in two siblings

This case report describes an unusual outcome of ABCA3 deficiency with resolution of symptoms, normalization of chest imaging and lung function in a 9-year-old child whose sibling died of the same disease in infancy.

Interstitial lung disease in two brothers with novel compound heterozygous ABCA3 mutations

Mutations in genes critical for surfactant metabolism, including surfactant protein C (SP-C) and ABCA3, are well-recognized causes of interstitial lung disease. Recessive mutations in ABCA3 were first attributed to fatal respiratory failure in full-term neonates, but they are also increasingly being recognized as a cause of respiratory disorders with less severe phenotypes in older children and also adults. Here, we report a 20-month-old boy with interstitial lung disease caused by two distinct ABCA3 mutations. Initial treatment with methylprednisolone was unsuccessful, but the additional administration of hydroxychloroquine was effective. The family history revealed that the patient's older brother had died of idiopathic interstitial lung disease at 6 months of age, suggesting a genetic etiology of the disease. Sequence analyses of SP-C and ABCA3 genes were performed using DNA samples from the patient himself, his parents, and his brother. These analyses revealed novel compound heterozygous mutations in the coding exons of ABCA3 in both the patient and his brother: c.2741A > G, of paternal origin, and c.3715_3716insGGGGGG, of maternal origin. Conclusion Since ABCA3 mutations seem to be a heterogeneous entity with various phenotypes, we recommend genetic testing for mutations in SP-C and ABCA3 genes to be considered in children with unexplained interstitial lung disease.

Genome-wide association study identifies multiple susceptibility loci for pulmonary fibrosis

We performed a genome-wide association study in non-Hispanic white subjects with fibrotic idiopathic interstitial pneumonias (N=1616) and controls (N=4683); replication was assessed in 876 cases and 1890 controls. We confirmed association with TERT and MUC5B on chromosomes 5p15 and 11p15, respectively, the chromosome 3q26 region near TERC, and identified 7 novel loci (P_Meta = 2.4×10⁻⁸ to P_Meta = 1.1×10⁻¹⁹). The novel loci include FAM13A (4q22), DSP (6p24), OBFC1 (10q24), ATP11A (13q34), DPP9 (19p13), and chromosomal regions 7q22 and 15q14-15. Our results demonstrate that genes involved in host defense, cell-cell adhesion, and DNA repair contribute to the risk of fibrotic IIP.

Implicating exudate macrophages and Ly-6C(high) monocytes in CCR2-dependent lung fibrosis following gene-targeted alveolar injury

The alveolar epithelium is characteristically abnormal in fibrotic lung disease, and we recently established a direct link between injury to the type II alveolar epithelial cell (AEC) and the accumulation of interstitial collagen. The mechanisms by which damage to the epithelium induces lung scarring remain poorly understood. It is particularly controversial whether an insult to the type II AEC initiates an inflammatory response that is required for the development of fibrosis. To explore whether local inflammation occurs following a targeted epithelial insult and contributes to lung fibrosis, we administered diphtheria toxin to transgenic mice with type II AEC-restricted expression of the diphtheria toxin receptor. We used immunophenotyping techniques and diphtheria toxin receptor-expressing, chemokine receptor-2-deficient (CCR2(-/-)) mice to determine the participation of lung leukocyte subsets in pulmonary fibrogenesis. Our results demonstrate that targeted type II AEC injury induces an inflammatory response that is enriched for CD11b(+) nonresident exudate macrophages (ExM) and their precursors, Ly-6C(high) monocytes. CCR2 deficiency abrogates the accumulation of both cell populations and protects mice from fibrosis, weight loss, and death. Further analyses revealed that the ExM are alternatively activated and that ExM and Ly-6C(high) monocytes express mRNA for IL-13, TGF-β, and the collagen genes, COL1A1 and COLIIIA1. Furthermore, the accumulated ExM and Ly-6C(high) monocytes contain intracellular collagen, as detected by immunostaining. Together, these results implicate CCR2 and the accumulation of ExM and Ly-6C(high) monocytes as critical determinants of pulmonary fibrosis induced by selective type II AEC injury.

New coding in the International Classification of Diseases, Ninth Revision, for children's interstitial lung disease

The term "children's interstitial lung disease" (chILD) refers to a heterogeneous group of rare and diffuse lung diseases associated with significant morbidity and mortality. These disorders include neuroendocrine cell hyperplasia of infancy, pulmonary interstitial glycogenosis, surfactant dysfunction mutations, and alveolar capillary dysplasia with misalignment of pulmonary veins. Diagnosis can be challenging, which may lead to a delay in recognition and treatment of these disorders. Recently, International Classifications of Diseases, Ninth Revision codes have been added for several of the chILD disorders. The purpose of this article is to give an overview of the chILD disorders and appropriate diagnostic coding.

Familial forms of nonspecific interstitial pneumonia/idiopathic pulmonary fibrosis: clinical course and genetic background

PURPOSE OF REVIEW

Familial pulmonary fibrosis has long been recognized and suggests that pulmonary fibrosis may have a genetic origin in some cases with an autosomal dominant transmission.

RECENT FINDINGS

Mutations in the telomerase complex and in the surfactant pathways have been discovered in the last decade. Almost 20% of the cases of familial pulmonary fibrosis are related to known functional mutations in one of these systems. A polymorphism in the promoter of the MUC5B gene has been associated with both sporadic and familial forms of idiopathic pulmonary fibrosis; however, the impact of this association remains to be determined.

SUMMARY

These genes point to alveolar epithelium injury and repair as a major component of the fibrotic process.

Surfactant protein B amount and kinetics in newborn infants: an optimized procedure

Surfactant protein B (SP-B) plays a key role in surfactant homeostasis affecting its biophysical properties and physiological function. Recently, a method to measure SP-B amount and kinetics from tracheal aspirates (TAs) became available. The main objective of this study was to improve the critical steps of the procedure to obtain a better SP-B sensitivity. We administered a 24 h continuous infusion of 1 mg/kg/h of 1(13)C-leucine to ten newborn infants. SP-B was isolated from serial TAs and its fractional synthesis rate, secretion time, peak time and half life were derived from (13)C enrichment curves obtained by gas chromatography mass spectrometry. SP-B amount in TAs was also assessed. During the extraction step, acidification and organic solvent ratio optimization doubled the recovery of SP-B from TAs, so did the elongation of the propylation time (from 20 min to 1 h) with enhanced leucine derivatization yield. Measurement of (13)C leucine enrichments, and therefore all SP-B kinetics parameters, were successfully calculated in all TAs samples due to the increase of SP-B yield. SP-B amount was 0.29 (0.16-0.41) % of total phospholipids with a minimum value of 0.08% belonging to one of the respiratory distress syndrome (RDS) patients. In conclusion, this new procedure enables accurate determination of SP-B kinetics even in the presence of low protein amount like in preterm RDS patients.

Molecular mechanisms in progressive idiopathic pulmonary fibrosis

There is clear evidence that environmental exposures and genetic predisposition contribute to the pathogenesis of idiopathic pulmonary fibrosis (IPF). Cigarette smoking increases the risk of developing IPF several-fold, as do other exposures such as metal-fume and wood-dust exposure. Occupations that increase the risk of IPF are agricultural work, hairdressing, and stone polishing, supporting the role of environmental exposure in disease pathogenesis. Genetic predisposition to IPF is evident from its familial aggregation and the fact that pulmonary fibrosis develops in several rare genetic disorders. Mutations in surfactant proteins lead to pulmonary fibrosis and are associated with endoplasmic reticulum stress in alveolar type II epithelial cells. Mutations in telomerase have been found in several families with IPF, and shortened telomeres are found in sporadic cases of IPF. A common variant in mucin 5B predisposes to both familial and sporadic IPF and is present in the majority of cases, indicating sporadic IPF occurs in those with genetic predisposition.

Neonatal oxygen increases sensitivity to influenza A virus infection in adult mice by suppressing epithelial expression of Ear1

Oxygen exposure in premature infants is a major risk factor for bronchopulmonary dysplasia and can impair the host response to respiratory viral infections later in life. Similarly, adult mice exposed to hyperoxia as neonates display alveolar simplification associated with a reduced number of alveolar epithelial type II cells and exhibit persistent inflammation, fibrosis, and mortality when infected with influenza A virus. Because type II cells participate in innate immunity and alveolar repair, their loss may contribute to oxygen-mediated sensitivity to viral infection. A genomewide screening of type II cells identified eosinophil-associated RNase 1 (Ear1). Ear1 was also detected in airway epithelium and was reduced in lungs of mice exposed to neonatal hyperoxia. Electroporation-mediated gene delivery of Ear1 to the lung before infection successfully reduced viral replication and leukocyte recruitment during infection. It also diminished the enhanced morbidity and mortality attributed to neonatal hyperoxia. These findings demonstrate that novel epithelial expression of Ear1 functions to limit influenza A virus infection, and its loss contributes to oxygen-associated epithelial injury and fibrosis after infection. People born prematurely may have defects in epithelial innate immunity that increase their risk for respiratory viral infections.

A national internet-linked based database for pediatric interstitial lung diseases: the French network

BACKGROUND

Interstitial lung diseases (ILDs) in children represent a heterogeneous group of rare respiratory disorders that affect the lung parenchyma. After the launch of the French Reference Centre for Rare Lung Diseases (RespiRare®), we created a national network and a web-linked database to collect data on pediatric ILD.

METHODS

Since 2008, the database has been set up in all RespiRare® centres. After patient's parents' oral consent is obtained, physicians enter the data of children with ILD: identity, social data and environmental data; specific aetiological diagnosis of the ILD if known, genetics, patient visits to the centre, and all medical examinations and tests done for the diagnosis and/or during follow up. Each participating centre has a free access to his own patients' data only, and cross-centre studies require mutual agreement. Physicians may use the system as a daily aid for patient care through a web-linked medical file, backed on this database.

RESULTS

Data was collected for 205 cases of ILD. The M/F sex ratio was 0.9. Median age at diagnosis was 1.5 years old [0-16.9]. A specific aetiology was identified in 149 (72.7%) patients while 56 (27.3%) cases remain undiagnosed. Surfactant deficiencies and alveolar proteinosis, haemosiderosis, and sarcoidosis represent almost half of the diagnoses. Median length of follow-up is 2.9 years [0-17.2].

CONCLUSIONS

We introduce here the French network and the largest national database in pediatric ILDs. The diagnosis spectrum and the estimated incidence are consistent with other European databases. An important challenge will be to reduce the proportion of unclassified ILDs by a standardized diagnosis work-up. This database is a great opportunity to improve patient care and disease pathogenesis knowledge. A European network including physicians and European foundations is now emerging with the initial aim of devising a simplified European database/register as a first step to larger European studies.

Familial interstitial pulmonary fibrosis: a large family with atypical clinical features

A large kindred of familial pulmonary fibrosis is reported. Six members from the first two generations of this particular kindred were described more than 40 years previously; six more individuals from the third and fourth generations have also been evaluated. The proband, now 23 years of age, has mild disease; the other 11 documented affected family members all died from their disease at an average age of 37 years (range 25 to 50 years). The pathology was that of usual interstitial pneumonia, as is typical in idiopathic pulmonary fibrosis. However, the initial radiographic pattern in many of these individuals was upper lobe and nodular and, along with the young age, was atypical for idiopathic pulmonary fibrosis. Several genetic abnormalities have been associated with familial pulmonary fibrosis. The present study examined the genes coding for surfactant protein-C, ATPbinding cassette protein A3 and telomerase, and found no abnormalities.

Respiratory syncytial virus potentiates ABCA3 mutation-induced loss of lung epithelial cell differentiation

ATP-binding cassette transporter A3 (ABCA3) is a lipid transporter active in lung alveolar epithelial type II cells (ATII) and is essential for their function as surfactant-producing cells. ABCA3 mutational defects cause respiratory distress in newborns and interstitial lung disease (ILD) in children. The molecular pathomechanisms are largely unknown; however, viral infections may initiate or aggravate ILDs. Here, we investigated the impact of the clinically relevant ABCA3 mutations, p.Q215K and p.E292V, by stable transfection of A549 lung epithelial cells. ABCA3 mutations strongly impaired expression of the ATII differentiation marker SP-C and the key epithelial cell adhesion proteins E-cadherin and zonula occludens-1. Concurrently, cells expressing ABCA3 mutation acquired mesenchymal features as observed by increased expression of SNAI1, MMP-2 and TGF-β1, and elevated phosphorylation of Src. Infection with respiratory syncytial virus (RSV), the most common viral respiratory pathogen in small children, potentiated the observed mutational effects on loss of epithelial and acquisition of mesenchymal characteristics. In addition, RSV infection of cells harboring ABCA3 mutations resulted in a morphologic shift to a mesenchymal phenotype. We conclude that ABCA3 mutations, potentiated by RSV infection, induce loss of epithelial cell differentiation in ATII. Loss of key epithelial features may disturb the integrity of the alveolar epithelium, thereby comprising its functionality. We suggest the impairment of epithelial function as a mechanism by which ABCA3 mutations cause ILD.