Expression of thyroid transcription factor-1 in congenital cystic adenomatoid malformation of the lung

Integrative analysis of bulk and single-cell RNA sequencing reveals the gene expression profile and the critical signaling pathways of type II CPAM

BACKGROUD

Type II congenital pulmonary airway malformation (CPAM) is a rare pulmonary microcystic developmental malformation. Surgical excision is the primary treatment for CPAM, although maternal steroids and betamethasone have proven effective in reducing microcystic CPAM. Disturbed intercellular communication may contribute to the development of CPAM. This study aims to investigate the expression profile and analyze intercellular communication networks to identify genes potentially associated with type II CPAM pathogenesis and therapeutic targets.

METHODS

RNA sequencing (RNA-seq) was performed on samples extracted from both the cystic area and the adjacent normal tissue post-surgery in CPAM patients. Iterative weighted gene correlation network analysis (iWGCNA) was used to identify genes specifically expressed in type II CPAM. Single-cell RNA-seq (scRNA-seq) was integrated to unveil the heterogeneity in cell populations and analyze the communication and interaction within epithelial cell sub-populations.

RESULTS

A total of 2,618 differentially expressed genes were identified, primarily enriched in cilium-related biological process and inflammatory response process. Key genes such as EDN1, GPR17, FPR2, and CHRM1, involved in the G protein-coupled receptor (GPCR) signaling pathway and playing roles in cell differentiation, apoptosis, calcium homeostasis, and the immune response, were highlighted based on the protein-protein interaction network. Type II CPAM-associated modules, including ciliary function-related genes, were identified using iWGCNA. By integrating scRNA-seq data, AGR3 (related to calcium homeostasis) and SLC11A1 (immune related) were identified as the only two differently expressed genes in epithelial cells of CPAM. Cell communication analysis revealed that alveolar type 1 (AT1) and alveolar type 2 (AT2) cells were the predominant communication cells for outgoing and incoming signals in epithelial cells. The ligands and receptors between epithelial cell subtypes included COLLAGEN genes enriched in PI3K-AKT singaling and involved in epithelial to mesenchymal transition.

CONCLUSIONS

In summary, by integrating bulk RNA-seq data of type II CPAM with scRNA-seq data, the gene expression profile and critical signaling pathways such as GPCR signaling and PI3K-AKT signaling pathways were revealed. Abnormally expressed genes in these pathways may disrupt epithelial-mesenchymal transition and contribute to the development of CPAM. Given the effectiveness of prenatal treatments of microcystic CPAM using maternal steroids and maternal betamethasone administration, targeting the genes and signaling pathways involved in the development of CPAM presents a promising therapeutic strategy.

Integrated bulk and single-cell RNA-sequencing reveals SPOCK2 as a novel biomarker gene in the development of congenital pulmonary airway malformation

BACKGROUND

Congenital pulmonary airway malformation (CPAM) is the most frequent pulmonary developmental malformation and the pathophysiology remains poorly understood. This study aimed to identify the characteristic gene expression patterns and the marker genes essential to CPAM.

METHODS

Tissues from the cystic area displaying CPAM and the area of normal appearance were obtained during surgery. Bulk RNA sequencing (RNA-seq) and single-cell RNA sequencing (scRNA-seq) were performed for integrating analysis. Iterative weighted gene correlation network analysis (iWGCNA) was used to identify specifically expressed genes to CPAM.

RESULTS

In total, 2074 genes were significantly differentially expressed between the CPAM and control areas. Of these differentially expressed genes (DEGs), 1675 genes were up-regulated and 399 genes were down-regulated. Gene ontology analysis revealed these DEGs were specifically enriched in ciliated epithelium and involved in immune response. We also identified several CPAM-related modules by iWGCNA, among them, P15_I4_M3 module was the most influential module for distinguishing CPAMs from controls. By combining the analysis of the expression dataset from RNA-seq and scRNA-seq, SPOCK2, STX11, and ZNF331 were highlighted in CPAM.

CONCLUSIONS

Through our analysis of expression datasets from both scRNA-seq and bulk RNA-seq of tissues obtained from patients with CPAM, we identified the characteristic gene expression patterns associated with the condition. Our findings suggest that SPOCK2 could be a potential biomarker gene for the diagnosis and therapeutic target in the development of CPAM, whereas STX11 and ZNF331 might serve as prognostic markers for this condition. Further investigations with larger samples and function studies are necessary to confirm the involvement of these genes in CPAM.

Developmental Pathways Underlying Lung Development and Congenital Lung Disorders

Lung organogenesis is a highly coordinated process governed by a network of conserved signaling pathways that ultimately control patterning, growth, and differentiation. This rigorously regulated developmental process culminates with the formation of a fully functional organ. Conversely, failure to correctly regulate this intricate series of events results in severe abnormalities that may compromise postnatal survival or affect/disrupt lung function through early life and adulthood. Conditions like congenital pulmonary airway malformation, bronchopulmonary sequestration, bronchogenic cysts, and congenital diaphragmatic hernia display unique forms of lung abnormalities. The etiology of these disorders is not yet completely understood; however, specific developmental pathways have already been reported as deregulated. In this sense, this review focuses on the molecular mechanisms that contribute to normal/abnormal lung growth and development and their impact on postnatal survival.

Narrative review of congenital lung lesions

This article reviews the contemporary diagnosis and management of antenatally diagnosed congenital lung lesions. These anomalies, which include congenital pulmonary airway malformation (CPAM) (formerly congenital cystic adenomatoid malformation), bronchopulmonary sequestration (BPS), bronchogenic cyst, and congenital lobar emphysema (CLE), are relatively rare but are increasingly encountered by clinicians because of the improved resolution and enhanced sensitivity of fetal ultrasound. Serial assessment of these lesions throughout pregnancy remains the norm rather than the exception. Perinatal management strategies may differ based on initial size and growth patterns of these masses until delivery. Fetal magnetic resonance imaging and other diagnostic testing can sometimes be helpful in providing additional prognostic information. Over the last decade, maternal steroids have become standard of care in the management of larger lesions at risk for nonimmune hydrops. As a result, fetal surgical procedures, including open resection, thoracoamniotic shunting, and ex utero intrapartum treatment (EXIT), are less uncommonly performed. Decisions regarding whether delivery of these fetuses should occur in a tertiary care center with pediatric surgery coverage versus delivery at a local community hospital are now highly relevant in most prenatal counseling discussions with families. Large lung malformations may require urgent surgical removal in the early postnatal period because of respiratory distress. Other complications, such as recurrent pneumonia, pneumothorax, and cancer, are indications for postnatal lung resection on an elective basis. Many children are good candidates for minimally invasive (thoracoscopic) surgical approaches as an alternative to resection by thoracotomy. In the vast majority of cases, the overall prognosis remains excellent.

Mechanism of lung development in the aetiology of adult congenital pulmonary airway malformations

Congenital pulmonary airway malformations (CPAMs) are rare lung abnormalities that result in cyst formation and are associated with respiratory distress in infants and malignant potential in adults. The pathogenesis of CPAMs remains unknown but data suggest disruption of the normal proximo-distal programme of airway branching and differentiation. Here, we demonstrate that adult human CPAM are lined with epithelium that retains SOX-2 and thyroid transcription factor-1 immunohistochemical markers, characteristic of the developing lung. However, RALDH-1, another key marker, is absent. This suggests a more complex aetiology for CPAM than complete focal arrest of lung development and may provide insight to the associated risk of malignancy.

Early KRAS oncogenic driver mutations in nonmucinous tissue of congenital pulmonary airway malformations as an indicator of potential malignant behavior

The potential for malignant degeneration is the most common reason for some practitioners to resect asymptomatic congenital pulmonary airway malformations (CPAMs). We aimed to investigate the potential of various immunohistochemical (IHC) and genomic biomarkers to predict the presence of mucinous proliferations (MPs) in CPAM. Archival CPAM tissue samples were re-assessed and underwent IHC analysis using a panel of differentiating markers (TTF1/CDX2/CC10/MUC2/MUC5AC/p16/p53/DICER1). In each sample, intensity of IHC staining was assessed separately in normal lung tissue, CPAM, and MP tissue, using a semiquantitative approach. Likewise, next-generation targeted sequencing of known adult lung driver mutations, including KRAS/BRAF/EGFR/ERBB2, was performed in all samples with MP and in control samples of CPAM tissue without MP. We analyzed samples of 25 CPAM type 1 and 25 CPAM type 2 and found MPs in 11 samples. They were all characterized by strong MUC5AC expression, and all carried a KRAS mutation in the MP and adjacent nonmucinous CPAM tissue, whereas the surrounding normal lung tissue was negative. By contrast, in less than half (5 out of 12) control samples lacking MP, the CPAM tissue also carried a KRAS mutation. KRAS mutations in nonmucinous CPAM tissue may identify lesions with a potential for malignant degeneration and may guide histopathological assessment and patient follow-up.

Cancer gene mutations in congenital pulmonary airway malformation patients

Background

Newborns affected with congenital pulmonary airway malformations (CPAMs) may present with severe respiratory distress or remain asymptomatic. While surgical resection is the definitive treatment for symptomatic CPAMs, prophylactic elective surgery may be recommended for asymptomatic CPAMs owing to the risk of tumour development. However, the implementation of prophylactic surgery is quite controversial on the grounds that more evidence linking CPAMs and cancer is needed. The large gap in knowledge of CPAM pathogenesis results in uncertainties and controversies in disease management. As developmental genes control postnatal cell growth and contribute to cancer development, we hypothesised that CPAMs may be underlain by germline mutations in genes governing airways development.

Methods

Sequencing of the exome of 19 patients and their unaffected parents.

Results

A more than expected number of mutations in cancer genes (false discovery rate q-value <5.01×10⁻⁵) was observed. The co-occurrence, in the same patient, of damaging variants in genes encoding interacting proteins is intriguing, the most striking being thyroglobulin (TG) and its receptor, megalin (LRP2). Both genes are highly relevant in lung development and cancer.

Conclusions

The overall excess of mutations in cancer genes may account for the reported association of CPAMs with carcinomas and provide some evidence to argue for prophylactic surgery by some surgeons.

Congenital pulmonary airway malformation (CPAM) patients have more than expected numbers of damaging variants in genes involved in lung carcinoma; this may provide evidence for clinicians choosing to adopt prophylactic excision in CPAMhttp://ow.ly/h1AE30n4DIe

Expression Analysis of ACSL5 and Wnt2B in Human Congenital Pulmonary Airway Malformations

BACKGROUND

The objective of this study was to determine acyl-CoA synthetase 5 (ACSL5) and Wnt2B expression patterns in human congenital pulmonary airway malformations (CPAMs) and to identify the possible roles of ACSL5 and Wnt2B in the pathogenesis of CPAM.

METHODS

Expression of ACSL5 and Wnt2B was evaluated by immunohistochemical staining, Western blotting, and quantitative real-time polymerase chain reaction, which were performed on surgical specimens of CPAM and adjacent normal lung tissues as controls.

RESULTS

Immunohistochemistry revealed that ACSL5 and Wnt2B immunopositive cells were predominantly detected in the mesenchymal cell nucleus, and there were lower expressions of ACSL5 and Wnt2B immunopositive cells in CPAM tissues than those in adjacent normal lung tissues. Western blotting and quantitative real-time polymerase chain reaction showed that ACSL5 and Wnt2B protein and mRNA expressions were significantly decreased in CPAM tissues as compared to the adjacent normal lung tissues (P < 0.05). In addition, there was a reduced level of ACSL5 relative to that of Wnt2B.

CONCLUSIONS

The decreased ACSL5 and Wnt2B expressions correlated with aberrations in pulmonary development and in the pathogenesis of CPAM, so downregulation of ACSL5 and Wnt2B could play an important role in the development of bronchial-alveolar structures in CPAM.

Congenital pulmonary airway malformation: advances and controversies

Advances in antenatal screening have provided evidence that the prevalence of congenital pulmonary airway malformation is higher than previously thought. This means that, on a global scale, more congenital pulmonary airway malformations will be diagnosed and seen by clinicians across many different specialties. This increase poses new controversies and challenges for clinicians in terms of prenatal and postnatal management. Important and exciting research has begun to emerge in the past decade. This Review describes current understanding of the disease, the latest surgical developments, and highlights management issues and controversies, including the rationale and timing of surgical intervention, the choice of surgical approach, and long-term functional outcomes. In doing so, we attempt to provide a balanced management algorithm for readers.

Congenital Cystic Adenomatoid Malformation Diagnosed During First-Trimester Ultrasound Scan

Patient: Female, 26

Final Diagnosis: Congenital cystic adenomatoid malformation (CCAM)

Symptoms: Inconveniently • polyhydramnios

Medication: —

Clinical Procedure: Termination of pregnancy

Specialty: Obstetrics and Gynecology

Congenital pulmonary airway malformations: state-of-the-art review for pediatrician's use

Congenital pulmonary airway malformations or CPAM are rare developmental lung malformations, leading to cystic and/or adenomatous pulmonary areas. Nowadays, CPAM are diagnosed prenatally, improving the prenatal and immediate postnatal care and ultimately the knowledge on CPAM pathophysiology. CPAM natural evolution can lead to infections or malignancies, whose exact prevalence is still difficult to assess. The aim of this "state-of-the-art" review is to cover the recently published literature on CPAM management whether the pulmonary lesion was detected during pregnancy or after birth, the current indications of surgery or surveillance and finally its potential evolution to pleuro-pulmonary blastoma.

CONCLUSION

Surgery remains the cornerstone treatment of symptomatic lesions but the postnatal management of asymptomatic CPAM remains controversial. There are pros and cons of surgical resection, as increasing rate of infections over time renders the surgery more difficult after months or years of evolution, as well as risk of malignancy, though exact incidence is still unknown. What is known: • Congenital pulmonary airway malformations (CPAM) are rare developmental lung malformations mainly antenatally diagnosed. • While the neonatal management of symptomatic CPAM is clear and includes prompt surgery, controversies remain for asymptomatic CPAM due to risk of infections and malignancies. What is new: • Increased rate of infection over time renders the surgery more difficult after months or years of evolution and pushes for recommendation of early elective surgery. • New molecular or pathological pathways may help in the distinction of type 4 CPAM from type I pleuropulmonary blastoma.

Prenatal and Postnatal Management of Congenital Pulmonary Airway Malformation

Congenital pulmonary airway malformation (CPAM) is one of the most common lung lesions detected prenatally. Despite the research efforts made in the past few years, controversy and lack of clarity in the literature still exist regarding nomenclature, classification, pathogenesis and the management of CPAM. Therefore, it is of greatest importance to delineate the natural history of CPAMs and to create a consensus to guide the management and follow-up of these lesions. This review will focus on classification systems, highlighting the most recent advancements in pathogenesis, and current practice in the prenatal diagnosis of CPAM. Strategies of prenatal management and postnatal management will be reviewed. Long-term follow-up, including lung cancer risk, is discussed and an outcome perspective is presented.

FGF10 Signaling differences between type I pleuropulmonary blastoma and congenital cystic adenomatoid malformation

Background

Type I pleuropulmonary blastoma (PPB) and congenital cystic adenomatoid malformation of the lung (CCAM) are cystic lung diseases of childhood. Their clinical and radiological presentations are often similar, and pathologic discrimination remains difficult in many cases. As a consequence, type I PPB and CCAM are frequently confused, leading to delayed adequate management for type I PPB. Recent studies have suggested a role for fibroblast growth factor (FGF) 10 signal pathway in CCAM pathogenesis. The objective of our study was to determine whether FGF10 signaling differs between CCAM and type I PPB.

Methods

Immunohistochemical studies were performed for expression of FGF10, its receptor FGFR2b, and its inhibitor sonic hedgehog (SHH) in focal type I PPB (n=6), CCAM type I (n=7), CCAM type II (n=7), and control lungs (n=5).

Results

FGF10, FGFR2b, and SHH expressions differed markedly between type I PPB and both types of CCAM. Type I and type II CCAM cystic walls expressed FGF10, FGFR2b, and SHH, whereas staining was absent or poor in type I PBB cystic walls. Expression of FGF10, FGFR2b, and SHH did not differ between CCAM cystic walls and control airway walls.

Conclusions

These findings show that immunohistochemistry with FGF10, FGFR2b, or SHH could be useful in differentiating CCAM from type I PPB, when a child presents with a focal cystic lung lesion. The absence of strong expression of FGF10, FGFR2b, and/or SHH makes the diagnosis of CCAM very doubtful.

[Congenital cystic adenomatoid malformations of the lung: diagnosis, treatment, pathophysiological hypothesis]

Congenital cystic adenomatoid malformations (CCAM) of the lung are the most frequent congenital lung malformations. Their diagnosis is based on histological features. CCAM consist of bronchopulmonary cystic lesions which are classified according to the presence and cysts size. Type I CCAM are composed of large cysts (>2 cm) lined by a columnar pseudostratified epithelium. Type II CCAM contain multiple small cystic lesions (<1 cm) lined by a flattened cuboidal epithelium. Type III CCAM are more solid and contain immature structures resembling the pseudoglandular stage of lung development. Ultrasonography (US) allows early detection during the second trimester of pregnancy as cystic, and/or hyperechoic fetal lung lesions. Although most CCAM remain asymptomatic, CCAM can cause polyhydramnios or fetal hydrops, respiratory distress at birth, infections and pneumothoraces during infancy, and may give rise to malignancies. Serial US allow detection of complications, and planification of delivery. Complicated forms require an urgent treatment. In fetuses with a macrocystic life-threatening lesion, a thoraco-amniotic shunt can be placed. Microcystic compressive forms may respond to prenatal steroids. Post-natal symptomatic lesions require early surgery. The treatment of asymptomatic forms remains controversial. Some recommend a non-operative approach with a long-term clinical and radiological following, whereas other favour a preventive surgical excision. The origin of CCAM remains unknown. Recent advances suggest a transient and focal abnormality in lung development which may result from an airway obstruction. This article reviews the diagnosis, treatment, and pathophysiology of CCAM.

Congenital pulmonary airway malformation (CPAM) [congenital cystic adenomatoid malformation] associated with tracheoesophageal fistula and agensesis of the corpus callosum

Congenital pulmonary airway malformations (CPAM) are a family of hamartomatous disorders due to the uncontrolled overgrowth of the terminal bronchioles. Congenital pulmonary airway malformations can co-exist with cardiovascular and/or urogenital malformations, but their association with thoracopulmonary malformations is extremely rare. We report the first case of CPAM type I, co-existing with tracheo-esophageal fistula and corpus callosum agenesis.

[Congenital lung malformations: natural history and pathophysiological mechanisms]

INTRODUCTION

Congenital lung lesions comprise a broad spectrum of various malformations including congenital cystic adenomatoid malformation (CCAM), bronchopulmonary sequestration (BPS), congenital lobar emphysema, bronchial atresia and bronchogenic cyst. This review aims at the description of their natural history, and of the underlying pathophysiological mechanisms.

STATE OF THE ART

Congenital lung lesions are frequently diagnosed antenatally and many remain asymptomatic after birth. In the absence of antenatal identification, they are usually revealed by the occurrence of infection. In some cases, spontaneous resolution of the malformation can occur. Different pathogenic hypotheses are discussed for the origin of these abnormalities, and common processes appear likely to all of these malformations. Factors involved in the process of branching seem to play a particularly important role.

PERSPECTIVES

Prospective follow-up of operated and unoperated children would complete our knowledge about the natural history of these lesions. The contribution of experimental models has led to advances in the understanding of pathogenic mechanisms. Further studies are needed to identify the factors initiating the malformative process.

Aberrant cell adhesion molecule expression in human bronchopulmonary sequestration and congenital cystic adenomatoid malformation

In many organs, integrins and cadherins are partly regulated by Hox genes, but their interactions in airway morphogenesis and congenital lung diseases are unknown. We previously showed that the Hox protein HoxB5 is abnormally increased in bronchopulmonary sequestration (BPS) and congenital cystic adenomatoid malformation (CCAM), congenital lung lesions with abnormal airway branching. We now report on alpha(2)-, alpha(3)-, and beta(1)-integrin and E-cadherin expression in normal human lung and in BPS and CCAM tissue previously shown to have abnormal HoxB5 expression and on the relationship of cell adhesion molecule expression to Hoxb5 regulation. alpha(2)-, alpha(3)-, and beta(1)-integrins and E-cadherin expression in normal human lung and BPS and CCAM were evaluated using Western blot and immunohistochemistry. Fetal mouse lung fibroblasts with Hoxb5-specific siRNA downregulation were evaluated for alpha(2)-integrin protein levels by Western blot. Compared with normal human lung, a previously undetected alpha(2)-integrin isoform potentially lacking essential cytoplasmic sequences was significantly increased in BPS and CCAM, and alpha(2)-integrin spatial and cellular expression was more intense. E-cadherin protein levels were also significantly increased, whereas alpha(3) increased in CCAM compared with canalicular, but not with alveolar, stage lung. beta(1)-integrin levels were unchanged. We conclude that in BPS and CCAM, altered alpha(2)-integrin cytoplasmic signaling contributes to abnormal cellular behavior in these lung lesions. Aberrant cell adhesion molecule and Hox protein regulation are likely part of the mechanism involved in the development of BPS and CCAM.

Immortalization of human alveolar epithelial cells to investigate nanoparticle uptake

Primary human alveolar type 2 (AT2) cells were immortalized by transduction with the catalytic subunit of telomerase and simian virus 40 large-tumor antigen. Characterization by immunochemical and morphologic methods demonstrated an AT1-like cell phenotype. Unlike primary AT2 cells, immortalized cells no longer expressed alkaline phosphatase, pro-surfactant protein C, and thyroid transcription factor-1, but expressed increased caveolin-1 and receptor for advanced glycation end products (RAGE). Live cell imaging using scanning ion conductance microscopy showed that the cuboidal primary AT2 cells were approximately 15 microm and enriched with surface microvilli, while the immortal AT1 cells were attenuated more than 40 microm, resembling these cells in situ. Transmission electron microscopy highlighted the attenuated morphology and showed endosomal vesicles in some immortal AT1 cells (but not primary AT2 cells) as found in situ. Particulate air pollution exacerbates cardiopulmonary disease. Interaction of ultrafine, nano-sized particles with the alveolar epithelium and/or translocation into the cardiovasculature may be a contributory factor. We hypothesized differential uptake of nanoparticles by AT1 and AT2 cells, depending on particle size and surface charge. Uptake of 50-nm and 1-microm fluorescent latex particles was investigated using confocal microscopy and scanning surface confocal microscopy of live cells. Fewer than 10% of primary AT2 cells internalized particles. In contrast, 75% immortal AT1 cells internalized negatively charged particles, while less than 55% of these cells internalized positively charged particles; charge, rather than size, mattered. The process was rapid: one-third of the total cell-associated negatively charged 50-nm particle fluorescence measured at 24 hours was internalized during the first hour. AT1 cells could be important in translocation of particles from the lung into the circulation.

Laser microdissection allows detection of abnormal gene expression in cystic adenomatoid malformation of the lung

BACKGROUND/PURPOSE

Congenital cystic adenomatoid malformation (CCAM) of the lung may result from a localized aberrant epithelial-mesenchymal interaction during lung development. We used laser microdissection (LMD) to isolate the epithelium and mesenchyme of CCAM, and studied candidate gene expression in these pure cell populations.

METHODS

Congenital cystic adenomatoid malformation tissue was obtained from fetal (n = 5) and postnatal (n = 5) surgical specimens. Normal fetal lung (n = 10) was obtained from abortus material, and normal postnatal lung (n = 5) was identified from surgical specimens. Whole tissue was analyzed using immunohistochemistry and reverse transcriptase polymerase chain reaction (RT-PCR). Using LMD, columnar bronchiolar type epithelium and underlying mesenchyme were isolated. Multiplex nested RT-PCR was then used to detect message levels of candidate genes.

RESULTS

Reverse transcriptase polymerase chain reaction performed on LMD-isolated tissue, but not whole tissue homogenate, revealed differences between CCAM and normal lung. In this report, we focus on the fibroblast growth factor (FGF) family. By RT-PCR, there was 4-fold more epithelial expression of FGF9 in fetal CCAM vs normal fetal lung (P < .07). This was qualitatively confirmed by immunohistochemistry. We also detected decreased FGF7 expression in CCAM mesenchyme (P < .05) but no significant differences in FGF10 or FGFR2.

CONCLUSIONS

LMD may be used to overcome the limitations of tissue heterogeneity in the study of CCAM. Abnormal growth factor expression may play a role in the etiology of this lesion.

Regulation of alveologenesis: clinical implications of impaired growth

During its development that begins in intrauterine life, the lung is transformed from a simple epithelial lined sac that emerges from the foregut into a complex arrangement of blood vessels, airways, and alveoli that make up the mature lung structure. This remarkable transformation that continues for several years postnatally, is achieved by the influence of several genes, transcription factors, growth factors and hormones upon the cells and proteins of the lung bud. A seminal event in this process is the formation of the air-blood barrier within the alveolar wall, an evolutionary modification that permits independent air-breathing existence in mammals. Molecular biological techniques have enabled elucidation of the mechanistic pathways contributing to alveologenesis and have provided probable molecular bases for examples of impaired alveologenesis encountered by the paediatric pathologist.

Foxp2 inhibits Nkx2.1-mediated transcription of SP-C via interactions with the Nkx2.1 homeodomain

The transcription factor (TF) Foxp2 has been shown to partially repress surfactant protein C (SP-C) transcription, presumably through interaction of an independent repressor domain with a conserved Foxp2 consensus site in the SP-C promoter. We explored the role of interactions between Foxp2 and the homeodomain TF Nkx2.1 that may contribute to the marked reduction in SP-C expression accompanying phenotypic transition of alveolar epithelial type II (AT2) to type I (AT1) cells. Foxp2 dose-dependently inhibited Nkx2.1-mediated activation of SP-C in MLE-15 cells. While electrophoretic mobility shift assays and chromatin immunoprecipitations revealed an interaction between Foxp2 and the conserved consensus motif in the SP-C promoter, Nkx2.1-mediated activation of the 318-bp proximal SP-C promoter (which lacks a Foxp2 consensus) was attenuated by increasing amounts of Foxp2. Co-immunoprecipitation and mammalian two-hybrid assays confirmed a physical interaction between Nkx2.1 and Foxp2 mediated through the Nkx2.1 homeodomain. Formation of an Nkx2.1 complex with an SP-C oligonucleotide was inhibited dose-dependently by recombinant Foxp2. These findings demonstrate that direct interaction between Foxp2 and Nkx2.1 inhibits Nkx2.1 DNA-binding and transcriptional activity and suggest a mechanism for down-regulation of SP-C (and probably other AT2 cell genes) during transition of AT2 cells to an AT1 cell phenotype.

Expression of epidermal growth factor receptor, but not K-RAS mutations, is present in congenital cystic airway malformation/congenital pulmonary airway malformation

Congenital cystic airway malformation/congenital pulmonary airway malformation (CCAM/CPAM) of the lung is a rare but well-described malformative lesion of pulmonary parenchyma characterized by the abnormal maturation of airways along with an increase in terminal respiratory structures, resulting in cysts of variable sizes. Five types have been classified based on morphological analysis. Although the etiology of the lesion is still unclear, recent data suggest that bronchial atresia is a predisposing/associated anomaly. A described association between type 1 CCAM/CPAM and bronchioloalveolar carcinoma suggests that type 1 CCAM/CPAM may predispose to malignant transformation by as yet unidentified tumorigenic mechanisms. Here we studied epidermal growth factor receptor (EGFR) and K-RAS oncogene, 2 biological markers closely associated with tumorigenesis and altered in many types of tumors, including lung carcinomas. For this purpose, we used immunohistochemistry and gene sequencing in paraffin-embedded tissue. Our results demonstrate expression of EGFR in types 1 and 3 CCAM/CPAM, with a distinctive distribution and intensity, compared with that of type 2. Of special interest, mucinous areas in 2 cases of type 1 CCAM/CPAM lacked EGFR expression, whereas adjacent epithelial cystic linings were strongly positive. This supports the hypothesis that mucinous differentiation in CCAM/CPAM, always present in cases with malignant transformation, could be related to other molecular pathways. The K-RAS gene was screened for mutations usually found in lung carcinomas; however, no mutations were present in any of the studied samples. These findings support the notion that EGFR may play an important role in the pathogenesis and phenotype of CCAM/CPAM.

Mucinous Cells in Type 1 Pulmonary Congenital Cystic Adenomatoid Malformation as Mucinous Bronchioloalveolar Carcinoma Precursors

Type 1 congenital cystic adenomatoid malformation (CCAM), the most frequent malformation of the lung, is the only type to present intracystic mucinous cell clusters, which may form beyond the cysts extracystic mucinous proliferation resembling mucinous bronchioloalveolar carcinomas (BACs). As mucinous BACs are increasingly described in the literature in young patients with CCAM, we hypothesized that type 1 CCAM mucinous cells could represent BAC precursors. We reviewed 7 cases of type 1 CCAM including 6 with intracystic mucinous cell clusters, 3 with extracystic mucinous proliferations, and 4 with mucinous BAC or mixed adenocarcinoma with predominant BAC. K-ras mutations at codon 12 were detected in 3/3 intracystic mucinous cell clusters, in 2/3 extracystic mucinous proliferations, and in 3/4 BAC. Loss of heterozygosity (LOH) at p16(INK4) locus, with microsatellite alterations in 3 cases, was observed in 2/3 intracystic mucinous cell clusters, in 2/3 extracystic mucinous proliferations, and in all BAC. Two extracystic mucinous proliferations showed LOH at FHIT and Rb loci, respectively. P16(INK4) expression was lost in 2 intracystic mucinous cell clusters, 1 extracystic mucinous proliferation, and 1 BAC. Neither epidermal growth factor receptor mutation on exons 18, 19, and 21 nor P53 accumulation was observed. All lesions expressed MUC5AC, but were negative for MUC2, CDX2, and TTF-1. In conclusion, type 1 CCAM mucinous cells share the same differentiation profile with corresponding mucinous BAC, consistent with a common bronchial origin. Moreover, the high frequency of K-ras mutation and LOH and/or microsatellite alterations at p16(INK4) locus presented by these mucinous cells justifies their consideration as BAC precursors.

Twin-twin transfusion syndrome: cerebral ischemia is not the only fetal MR imaging finding

BACKGROUND

Twin-twin transfusion syndrome (TTTS) is a complication of monochorionic/diamniotic twin pregnancies. An imbalance of blood flow occurs through placental anastomoses, causing potentially significant morbidity and mortality in both twins. Although the sonographic findings of TTTS are well documented, we believe that MR imaging is a valuable adjunct.

OBJECTIVE

We describe the fetal MR imaging findings associated with TTTS.

MATERIALS AND METHODS

From 2003 to 2005, 37 consecutive MR imaging studies were performed on multiple-gestation pregnancies. Of the 37, 25 were consistent with TTTS, correlated and confirmed by sonographic criteria. MR fetal abnormalities were documented.

RESULTS

Cerebral ischemia, which could not be demonstrated by sonography, was delineated well by MR imaging. New findings noted on fetal MR imaging were enlargement of cerebral venous sinuses in both twins, dilatation of the renal collecting system in the recipient, lung lesions in the recipient and cerebral malformations in the donor.

CONCLUSION

MR imaging is an important adjunct in TTTS imaging. Its benefit over sonography is its clear definition of cerebral pathology, which is important for intervention and counseling. The new findings, particularly in the urinary tract and cerebral venous sinuses, also help support the diagnosis of TTTS and might reveal additional consequences of the altered hemodynamics that occur in TTTS.

Similarities and dissimilarities of branching and septation during lung development

The lungs of small premature babies are at a developmental stage of finalizing their airway tree by a process called branching morphogenesis, and of creating terminal gas exchange units by a mechanism called septation. If the branching process is disturbed, the lung has a propensity to be hypoplastic. If septation is impaired, the terminal gas exchange units, the alveoli, tend to be enlarged and reduced in number, an entity known as bronchopulmonary dysplasia. Here, we review current knowledge of key molecules influencing branching and septation. In particular, we discuss the molecular similarities and dissimilarities between the two processes of airspace enlargement. Understanding of the molecular mechanisms regulating branching and septation may provide perinatologists with targets for improving lung growth and maturation.

Congenital pulmonary airway malformation (congenital cystic adenomatoid malformation) with multiple extrapulmonary anomalies: autopsy report of a fetus at 19 weeks of gestation

Congenital pulmonary airway malformation, or congenital cystic adenomatoid malformation, is postulated to be a disorder of pulmonary airway morphogenesis and encompasses 5 different types with distinct levels or stages of tracheobronchial development. We present a unique case of type 2 congenital pulmonary airway malformation with a previously undocumented combination of multiple extrapulmonary anomalies, featuring ipsilateral multicystic renal dysgenesis, contralateral renal agenesis, and ovarian germ cell hypoplasia, diagnosed in a 19-week gestational age fetus by autopsy. Epithelial cells comprising the pulmonary lesions were positive for thyroid transcription factor-1, surfactant protein-B, and cytokeratin-7 but negative for cytokeratin-20 immunostainings, with the pattern seen in normal terminal bronchioles. Chromosomal analysis showed a normal female karyotype, despite a high estimated risk for Down syndrome suggested by the low maternal serum alpha-fetoprotein level.

Intralobar sequestration of the lung is a congenital anomaly: anatomopathological analysis of four cases diagnosed in fetal life

The origin of intralobar sequestration of the lung (ILS)-whether congenital or acquired--has often been controversial, since firm anatomical evidence of prenatal origin has been sparse. We describe four cases in which anomalous arterial supply from the aorta to abnormally echogenic lower lung lobes was demonstrated on routine antenatal ultrasound examination, and the diagnosis of ILS was subsequently confirmed by postmortem examination including bronchography of the fetuses at between 20 and 23 wk. One right-sided lesion was supplied from a branch of the coeliac axis, and three left-sided lesions were supplied from the thoracic aorta. In two cases, the arterial supply was shown to be multiple. All lesions were situated in the lower lobes. They showed a cystic transformation of the affected lung tissue which was histologically indistinguishable from cases diagnosed as congenital cystic adenomatoid lesion (CCAM) at the same gestational age, but clearly different from that seen in bronchial obstruction due to laryngeal stenosis at that age. Similar vascular lesions have been reported in otherwise normal lungs. The character of the anomalous arterial vessels is consistent with origin from the embryonic splanchnic plexus. The precise sequence of pathogenetic events is unclear but there appears to be a close relationship of this condition not only with CCAM but also with the condition of anomalous arterial supply to the lower lobe.

Thyroid transcription factor-1 expression during normal human lung development and in patients with congenital diaphragmatic hernia

BACKGROUND/PURPOSE

Thyroid transcription factor-1 (TTF-1) was detected in human respiratory epithelial cells from 11 weeks of gestation. TTF-1 is involved in both lung morphogenesis and in the regulation of surfactant proteins. Recently, low expression of TTF-1 in the nitrofen rat model of congenital diaphragmatic hernia (CDH) was shown and restoration of this downregulation by antenatal glucocorticolds (CS) was reported. The aim of this study was to investigate the expression of TTF-1 as a marker of lung morphogenesis in normal human lung development and in age-matched controls of human lung specimen in hypoplastic lungs of human CDH and other forms of lung hypoplasia.

METHODS

Immunohistochemistry by a monoclonal TTF-1 antibody was performed on paraffin sections of human fetal and neonatal lung tissues. The so-called developmental group (12 weeks' gestation to full term) included 47 lung specimens. The congenital hypoplasia group included 8 full-term CDH patients who died within 12 hours after birth, 3 full-term CDH patients who had antenatal CS therapy, and 4 full-term CDH patients after extracorporeal membrane oxygenation (ECMO) therapy. For comparison, 6 full-term born patients, who died of other forms of pulmonary hypoplasia, were used as comparative specimen. Immunohistochemical localization of TTF-1 was evaluated by light microscopy for 3 different areas of the airways including intrapulmonary bronchi, intermediate airways so-called terminal bronchioles, distal airways, and later sacculi and alveoli.

RESULTS

Nuclear TTF-1 staining was observed in the progenitor cells of the developing bronchiolar cells early in the human lung developmental series. At full term, TTF-1 was expressed in both type II epithelial cells and in subsets of respiratory nonciliated bronchiolar epithelial cells in a pattern similar in all studied groups. No TTF-1 expression was detected at the level of the intrapulmonary bronchi.

CONCLUSIONS

No difference in TTF-1 expression was observed in the developing early fetal and full-term neither in hypoplastic human lungs. This expression did not change with antenatal CS and postnatal ECMO treatment. Although TTF-1 appears to play an important role in lung morphogenesis, a pivotal role in human lung development is not likely.

Increased expression of thyroid transcription factor-1 (TTF-1) in respiratory epithelial cells inhibits alveolarization and causes pulmonary inflammation

Thyroid transcription factor-1 (TTF-1), a member of the Nkx2 family of homeodomain-containing transcription factors, is expressed in the epithelium of the lung. TTF-1 is a critical regulator of transcription for the surfactant proteins (SP) A, B, and C and is essential for lung morphogenesis. Sites and levels of TTF-1 expression vary during lung morphogenesis and following injury. In order to determine the role of TTF-1 in lung formation, transgenic mice were generated in which TTF-1 was expressed in respiratory epithelial cells of wild-type and Ttf1 null mutant (-/-) mice, using the lung-specific SP-C promoter. The SP-C-Ttf1 transgene did not rescue the severe pulmonary hypoplasia characteristic of the Ttf1 (-/-) mice. Increased expression of TTF-1, however, caused dose-dependent alterations in postnatal lung morphology of wild-type mice. Modest overexpression of TTF-1 caused type II cell hyperplasia and increased the cellular content of SP-B. In contrast, higher expression levels of TTF-1 disrupted alveolar septation, causing emphysema. In mice with the highest transgene expression, TTF-1 caused severe inflammation, pulmonary fibrosis, respiratory failure, and death, associated with eosinophil infiltration and increased expression of eotaxin and IL-6. Increased expression of TTF-1 altered alveolarization and caused chronic pulmonary inflammation, demonstrating that precise regulation of TTF-1 is critical for homeostasis in the postnatal lung.