Gail H. Deutsch

Extracellular Matrix Remodeling and Organization in Developing and Diseased Aortic Valves

Heart valve disease is an important cause of morbidity and mortality worldwide. Little is known about valve disease pathogenesis, but increasing evidence implicates a genetic basis for valve disease, suggesting a developmental origin. Although the cellular and molecular processes involved in early valvulogenesis have been well described, less is known about the regulation of valve extracellular matrix (ECM) organization and valvular interstitial cell (VIC) distribution that characterize the mature valve structure. Histochemistry, immunohistochemistry, and electron microscopy were used to examine ECM organization, VIC distribution, and cell proliferation during late valvulogenesis in chicken and mouse. In mature valves, ECM organization is conserved across species, and developmental studies demonstrate that ECM stratification begins during late embryonic cusp remodeling and continues into postnatal life. Cell proliferation decreases concomitant with ECM stratification and VIC compartmentalization. Explanted, stenotic bicuspid aortic valves (BAVs) from pediatric patients were also examined. The diseased valves exhibited disruption of the highly organized ECM and VIC distribution seen in normal valves. Cusps from diseased valves were thickened with increased and disorganized collagens and proteoglycans, decreased and fragmented elastic fibers, and cellular disarray without calcification or cell proliferation. Taken together, these studies show that normal valve development is characterized by spatiotemporal coordination of ECM organization and VIC compartmentalization and that these developmental processes are disrupted in pediatric patients with diseased BAVs.

Different thresholds of fibroblast growth factors pattern the ventral foregut into liver and lung

Cell fate and morphogenesis within the embryo is dependent upon secreted molecules that transduce signals between neighboring tissues. Reciprocal mesenchymal-epithelial interactions have proven essential during branching morphogenesis and cell differentiation within the lung; however, the interactions that result in lung specification from the foregut endoderm, prior to lung bud formation, are poorly understood. In this study, we investigate the tissue requirements and signals necessary for specification of a pulmonary cell fate using embryo tissue explants. We show that NKX2.1, an early transcription factor crucial for lung development, is expressed in the ventral foregut endoderm shortly after albumin and Pdx1, early markers of the liver and pancreas lineages, respectively. Similar to hepatic specification, direct contact of cardiac mesoderm with ventral endoderm is required to induce in vitro expression of NKX2.1 and downstream lung target genes including surfactant protein C and Clara cell secretory protein. In the absence of cardiac mesoderm, ventral foregut endoderm explants respond to exogenous fibroblast growth factor (FGF) 1 and FGF2 in a dose-dependent manner, with lower concentrations activating liver specific genes and higher concentrations activating lung specific genes. This signaling appears to be instructive, as the prospective dorsal midgut endoderm, which predominantly gives rise to the intestinal tract, is competent to respond to FGFs by inducing NKX2.1. Furthermore, the temporal expression and selective inhibition of FGF receptors 1 and 4 present within the endoderm implies that signaling through FGFR4 is involved in specifying lung versus liver. Together, the findings suggest that a concentration threshold of FGFs emanating from the cardiac mesoderm are involved in patterning the foregut endoderm.

In vitro generation of human pluripotent stem cell derived lung organoids

Recent breakthroughs in 3-dimensional (3D) organoid cultures for many organ systems have led to new physiologically complex in vitro models to study human development and disease. Here, we report the step-wise differentiation of human pluripotent stem cells (hPSCs) (embryonic and induced) into lung organoids. By manipulating developmental signaling pathways hPSCs generate ventral-anterior foregut spheroids, which are then expanded into human lung organoids (HLOs). HLOs consist of epithelial and mesenchymal compartments of the lung, organized with structural features similar to the native lung. HLOs possess upper airway-like epithelium with basal cells and immature ciliated cells surrounded by smooth muscle and myofibroblasts as well as an alveolar-like domain with appropriate cell types. Using RNA-sequencing, we show that HLOs are remarkably similar to human fetal lung based on global transcriptional profiles, suggesting that HLOs are an excellent model to study human lung development, maturation and disease. DOI: http://dx.doi.org/10.7554/eLife.05098.001

Congenital Lung Abnormalities: Embryologic Features, Prenatal Diagnosis, and Postnatal Radiologic-Pathologic Correlation

Congenital lung abnormalities are being detected more frequently at routine high-resolution prenatal ultrasonography. The most commonly encountered anomalies include lung agenesis-hypoplasia complex (pulmonary underdevelopment), congenital pulmonary airway malformations, congenital lobar overinflation, bronchial atresia, bronchogenic cysts, congenital high airway obstruction syndrome, scimitar syndrome, and bronchopulmonary sequestration. Recognizing the antenatal and postnatal imaging features of these abnormalities is necessary for optimal prenatal counseling and appropriate peri- and postnatal management. Supplemental material available at http://radiographics.rsna.org/lookup/suppl/doi:10.1148/rg.306105508/-/DC1.

Neuroendocrine Cell Hyperplasia of Infancy: Diagnosis With High-Resolution CT

OBJECTIVE Neuroendocrine cell hyperplasia of infancy is a form of childhood interstitial lung disease originally reported as persistent tachypnea of infancy. Reports of small series of cases and anecdotal experience have suggested that this disorder may have a consistent CT pattern. The purpose of this study was to review the CT findings in children with neuroendocrine cell hyperplasia of infancy to determine the findings at high-resolution CT, the diagnostic accuracy of CT compared with biopsy, and interrater reliability. MATERIALS AND METHODS Images from 23 CT examinations of children with biopsy-proven neuroendocrine cell hyperplasia of infancy and six CT examinations of children with other childhood interstitial lung diseases were reviewed by two pediatric radiologists with special expertise in thoracic imaging. Identifying digital data were removed, and images were reviewed without clinical data. A CT assessment form was completed for each patient. RESULTS Ground-glass opacification was the most common finding in patients with neuroendocrine cell hyperplasia of infancy. The right middle lobe and lingula were most commonly involved. Air trapping with a mosaic pattern was the second most common finding. Interrater reliability was very good with a kappa value of 0.93. The sensitivity and specificity of CT in the diagnosis of neuroendocrine cell hyperplasia of infancy were at least 78% and 100%. CONCLUSION Neuroendocrine cell hyperplasia of infancy can have a characteristic appearance on high-resolution CT scans, the imaging findings being useful in differentiating neuroendocrine cell hyperplasia of infancy from other types of childhood interstitial lung disease. The appearance aids radiologists in suggesting a specific diagnosis but does not exclude this diagnosis; in 17-22% of cases, the readers in this study did not suggest the diagnosis of neuroendocrine cell hyperplasia of infancy when it was present.

Usual Interstitial Pneumonia in an Adolescent With ABCA3 Mutations

Many diverse and frequently idiopathic disorders cause interstitial lung disease (ILD) in children. Although the histologic patterns of ILD in children and adults share similar features, important differences exist in etiology, clinical manifestations, and outcome. Usual interstitial pneumonia (UIP) is the most frequent histologic pattern in adult ILD; however, the characteristic histologic features of UIP have yet to be demonstrated in a child. We report a 15-year-old boy with the UIP pattern of pulmonary fibrosis who had mutations in the adenosine triphosphate-binding-cassette-A3 gene. Discovery of how genetic mutations of proteins involved in surfactant biosynthesis lead to progressive fibrosis will have implications for the understanding of the pathogenesis and clinical manifestations of ILD in both adults and children.

A protocol for the handling of tissue obtained by operative lung biopsy: recommendations of the chILD pathology co-operative group.

This is the first of a series on pediatric pulmonary disease that will appear as Perspectives in Pediatric Pathology over the coming months. The series will include practical issues, such as this protocol for handling lung biopsies and another on bronchoalveolar lavage in childhood, as well as reviews of advances in various areas in pediatric pulmonary pathology. It has been 11 years since the last Perspectives on pulmonary disease. Much has happened since then in this area, and this collection will highlight some emerging and rapidly advancing areas in pediatric lung disease. These will include a review of molecular mechanisms of lung development, and another of mechanisms of pulmonary vascular development. The surfactant system and its disorders, as well as recent advances in the biology of the pulmonary neuroendocrine system and mechanisms of respiratory viral disease, will be addressed. Articles on pulmonary hypertension, pulmonary neoplasia, and pediatric lung transplantation, with their implications for the pediatric pathologist, are also planned. The contributors to this series are a diverse group with special interests and expertise in these areas. As Dr. William Thurlbeck noted in his foreword to the previous volume, Pulmonary Disease, volume 18 of Perspectives in Pediatric Pathology, pediatric pathology had been largely concerned with phenomenology, rather than with mechanisms, model systems, and experimental investigation. I think he would have been pleased to see the changes that have occurred over the past 10 years in pediatric lung biology and pathology in particular, because these were particularly favored interests of his later years.

Crumbs3 Is Essential for Proper Epithelial Development and Viability

ABSTRACT First identified in Drosophila, the Crumbs (Crb) proteins are important in epithelial polarity, apical membrane formation, and tight junction (TJ) assembly. The conserved Crb intracellular region includes a FERM (band 4.1/ezrin/radixin/moesin) binding domain (FBD) whose mammalian binding partners are not well understood and a PDZ binding motif that interacts with mammalian Pals1 (protein associated with lin seven) (also known as MPP5). Pals1 binds Patj (Pals1-associated tight-junction protein), a multi-PDZ-domain protein that associates with many tight junction proteins. The Crb complex also binds the conserved Par3/Par6/atypical protein kinase C (aPKC) polarity cassette that restricts migration of basolateral proteins through phosphorylation. Here, we describe a Crb3 knockout mouse that demonstrates extensive defects in epithelial morphogenesis. The mice die shortly after birth, with cystic kidneys and proteinaceous debris throughout the lungs. The intestines display villus fusion, apical membrane blebs, and disrupted microvilli. These intestinal defects phenocopy those of Ezrin knockout mice, and we demonstrate an interaction between Crumbs3 and ezrin. Taken together, our data indicate that Crumbs3 is crucial for epithelial morphogenesis and plays a role in linking the apical membrane to the underlying ezrin-containing cytoskeleton.

Key Mechanisms of Early Lung Development

Lung morphogenesis requires the integration of multiple regulatory factors, which results in a functional air-blood interface required for gas exchange at birth. The respiratory tract is composed of endodermally derived epithelium surrounded by cells of mesodermal origin. Inductive signaling between these 2 tissue compartments plays a critical role in formation and differentiation of the lung, which is mediated by evolutionarily conserved signaling families used reiteratively during lung formation, including the fibroblast growth factor, hedgehog, retinoic acid, bone morphogenetic protein, and Wnt signaling pathways. Cells coordinate their response to these signaling proteins largely through transcription factors, which determine respiratory cell fate and pattern formation via the activation and repression of downstream target genes. Gain- and loss-of-function studies in null mutant and transgenic mice models have greatly facilitated the identification and hierarchical classification of these molecular programs. In this review, we highlight select molecular events that drive key phases of pulmonary development, including specification of a lung cell fate, primary lung bud formation, tracheoesophageal septation, branching morphogenesis, and proximal-distal epithelial patterning. Understanding the genetic pathways that regulate respiratory tract development is essential to provide insight into the pathogenesis of congenital anomalies and to develop innovative strategies to treat inherited and acquired lung disease.

Neuroendocrine Cell Distribution and Frequency Distinguish Neuroendocrine Cell Hyperplasia of Infancy From Other Pulmonary Disorders

BACKGROUND The diagnostic gold standard for neuroendocrine cell hyperplasia of infancy (NEHI) is demonstration of increased numbers of neuroendocrine cells (NECs) amid otherwise near-normal lung histology. Typical clinical and radiographic features often are present. However, NECs are also increased after lung injury and in other disorders, which can complicate biopsy specimen interpretation and diagnosis of suspected NEHI. Our objective was to determine whether NEC prominence is specific for the diagnosis of NEHI. METHODS Bombesin immunoreactivity was quantified in lung biopsy specimens from 13 children with characteristic clinical presentation and imaging appearance of NEHI. The primary comparison group was 13 age-matched patients selected from children with lung disorders that are known to be associated with NEC prominence. RESULTS Bombesin-immunopositive epithelial area was significantly increased in NEHI compared with other diseases. Patchy bronchiolar inflammation or fibrosis was frequently observed in NEHI, with no direct association between airway histopathology and bombesin-immunopositive area. NEC prominence correlated with severity of small airway obstruction demonstrated on infant pulmonary function testing. Immunohistochemical colocalization of bombesin with Ki67 did not reveal active NEC proliferation. There was wide intra- and intersubject variability in NEC number, which did not relate to radiographic appearance of the region biopsied. CONCLUSIONS Our findings demonstrate that NEC prominence is a distinguishing feature of NEHI independent of airway injury. The extent of intrasubject variability and potential for overlap with control subjects suggest that clinical-radiologic-pathologic correlation is required for diagnosis and that the abundance of NECs may not fully explain the disease pathogenesis.