The Molecular Basis for Abnormal Human Lung Development

Pulmonary Vascular Phenotypes of Prematurity: The Path to Precision Medicine

Pulmonary hypertension (PH) is associated with significant morbidities and high mortality in preterm infants, yet mechanisms contributing to the pathogenesis of PH, the impact of early pulmonary vascular disease (PVD) on the risk for BPD, the role for PH-targeted drug therapies, and long-term pulmonary vascular sequelae remain poorly understood. PVD is not a homogeneous disease, rather, PVD in the setting of prematurity includes various phenotypes as based on underlying pathophysiology, the severity of associated PH, the timing of disease onset, its contribution to hemodynamic and respiratory status, late outcomes, and other features. As with term newborns, severe hypoxemia with acute respiratory failure (HRF) in preterm infants can be due to marked elevation of pulmonary artery pressure with extrapulmonary shunt, traditionally referred to as persistent pulmonary hypertension of the newborn (PPHN). Transient and less severe levels of PH can also be observed during the early transition after birth without evidence of severe HRF, representing physiologic PH or delayed pulmonary vascular transition in preterm infants. Importantly, echocardiographic evidence of early PH has been strongly associated with the subsequent development of bronchopulmonary dysplasia (BPD), late PH, and chronic respiratory disease during infancy and early childhood. Late PH beyond the first postnatal months in preterm in neonates with established BPD is further associated with poor outcomes, especially as related to BPD severity. In addition, echocardiographic signs of PVD can further persist throughout childhood and may lead to chronic PH of variable severity and cardiac maldevelopment in prematurely born young adults. This review discusses the importance of characterizing diverse pulmonary vascular phenotypes in preterm infants to better guide clinical care and research, and to enhance the development of more precise therapeutic strategies to optimize early and late outcomes of preterm infants.

Negative Transpulmonary Pressure Disrupts Airway Morphogenesis by Suppressing Fgf10

Mechanical forces are increasingly recognized as important determinants of cell and tissue phenotype and also appear to play a critical role in organ development. During the fetal stages of lung morphogenesis, the pressure of the fluid within the lumen of the airways is higher than that within the chest cavity, resulting in a positive transpulmonary pressure. Several congenital defects decrease or reverse transpulmonary pressure across the developing airways and are associated with a reduced number of branches and a correspondingly underdeveloped lung that is insufficient for gas exchange after birth. The small size of the early pseudoglandular stage lung and its relative inaccessibility in utero have precluded experimental investigation of the effects of transpulmonary pressure on early branching morphogenesis. Here, we present a simple culture model to explore the effects of negative transpulmonary pressure on development of the embryonic airways. We found that negative transpulmonary pressure decreases branching, and that it does so in part by altering the expression of fibroblast growth factor 10 (Fgf10). The morphogenesis of lungs maintained under negative transpulmonary pressure can be rescued by supplementing the culture medium with exogenous FGF10. These data suggest that Fgf10 expression is regulated by mechanical stress in the developing airways. Understanding the mechanical signaling pathways that connect transpulmonary pressure to FGF10 can lead to the establishment of novel non-surgical approaches for ameliorating congenital lung defects.

Postnatal morphological lung development of wild type and CD26/DPP4 deficient rat pups in dependency of LPS exposure

BACKGROUND

Rodents are born with morphological immature lungs and an intact surfactant system. CD26/DPP4 is a multifactorial transmembrane integral type II protein, which is involved in physiological and pathophysiological processes and is already expressed during development. CD26/DPP4, called CD26 in the following, is able to enhance or dampen differently triggered inflammation. LPS exposure often used to simulate perinatal infection delays lung development.

OBJECTIVE

A perinatal LPS rat model was used to test the hypothesis that CD26 deficiency modulates LPS-induced retardation in morphological lung development.

METHODS

New born Fischer CD26 positive (CD26⁺) and deficient (CD26^-) rats were exposed to LPS on postnatal day (day post partum, dpp) 3 and 5. Morphological parameters of lung development were determined stereologically. Lung development was analysed in 7, 10 14 and 21day old rats.

RESULTS

Compared to controls LPS application resulted (1) in a mild inflammation independent of the strain, (2) in significantly lower total surface and volume of alveolar septa combined with significantly higher total volume of airspaces and alveolar size on dpp 7 in both substrains. However, compared to controls in LPS treated CD26^- rats significant lower values of total septal surface and volume combined with higher values of total parenchymal airspaces and alveolar size were found until the end of classical alveolarization (dpp14). In LPS treated CD26⁺ rat pups the retardation was abolished already on dpp 10.

CONCLUSION

In absence of CD26, LPS enhances the delay of morphological lung development. Morphological recovery was slower after the end of LPS exposure in CD26 deficient lungs.

Upregulated EFNB2 and EPHB4 promotes lung development in a nitrofen-induced congenital diaphragmatic hernia rat model

Congenital diaphragmatic hernia (CDH) is a common congenital malformation associated with high mortality rates, mainly due to pulmonary hypoplasia and persistent pulmonary hypertension following birth. The present study aimed to investigate abnormal lung development in a rat CDH model, and examine temporal and spatial changes in the expression of ephrin type‑B receptor 4 (EPHB4) and ephrin‑B2 (EFNB2) during fetal lung development, to elucidate the role of these factors during lung morphogenesis. Pregnant rats received nitrofen on embryonic day (E) 8.5 to induce CDH, and fetal lungs were collected on E13.5, E15.5, E17.5, E19.5, and E21.5. The mean linear intercept (MLI) and mean alveolar number (MAN) were observed in fetal lung tissue at E21.5 following hematoxylin and eosin staining. E13.5 fetal lungs were cultured for 96 h in serum‑free medium and branch development was observed under a microscope. The gene and protein expression levels of EPHB4 and EFNB2 were assessed by reverse transcription‑quantitative polymerase chain reaction analysis, and immunoblotting and immunohistochemistry, respectively. The fetal rat lungs were treated with EFNB2 and the activity of key signaling pathways was assessed. The lung index (lung weight/body weight) at E21.5 was significantly lower in the CDH rats, compared with that in the control fetal rats. The MLI and MAN were also lower in the CDH group. The number of lung terminal buds at E13.5 (embryonic stage), and the lung‑explant perimeter and surface were all smaller in the CDH group rats than in the control group at the same age. Pulmonary hypoplasia was observed following 96 h of in vitro culture. No significant differences were found in the expression levels of EFNB2 and EPHB4 between the CDH and control groups at E13.5 (embryonic stage) or E15.5 (pseudoglandular stage), however, EFNB2 and EPHB4 were significantly upregulated at E17.5 (canalicular stage), and at E19.5 and E21.5 (saccular/alveolar stages). EFNB2 stimulated pulmonary branching and EFNB2 supplementation decreased the activity of p38, c‑Jun NH2‑terminal kinase, extracellular signal‑regulated kinase, and signal transducer and activator of transcription. The CDH fetal rats developed pulmonary dysplasia at an early stage of fetal pulmonary development. Upregulated expression of EFNB2 and EPHB4 was observed in the rat lung of nitrofen‑induced CDH, and the increased expression of EFNB2 promoted rat lung development in the nitrofen‑induced CDH model.

Development of the lung

To fulfill the task of gas exchange, the lung possesses a huge inner surface and a tree-like system of conducting airways ventilating the gas exchange area. During lung development, the conducting airways are formed first, followed by the formation and enlargement of the gas exchange area. The latter (alveolarization) continues until young adulthood. During organogenesis, the left and right lungs have their own anlage, an outpouching of the foregut. Each lung bud starts a repetitive process of outgrowth and branching (branching morphogenesis) that forms all of the future airways mainly during the pseudoglandular stage. During the canalicular stage, the differentiation of the epithelia becomes visible and the bronchioalveolar duct junction is formed. The location of this junction stays constant throughout life. Towards the end of the canalicular stage, the first gas exchange may take place and survival of prematurely born babies becomes possible. Ninety percent of the gas exchange surface area will be formed by alveolarization, a process where existing airspaces are subdivided by the formation of new walls (septa). This process requires a double-layered capillary network at the basis of the newly forming septum. However, in parallel to alveolarization, the double-layered capillary network of the immature septa fuses to a single-layered network resulting in an optimized setup for gas exchange. Alveolarization still continues, because, at sites where new septa are lifting off preexisting mature septa, the required second capillary layer will be formed instantly by angiogenesis. The latter confirms a lifelong ability of alveolarization, which is important for any kind of lung regeneration.

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.

Loss of Hif-2α Rescues the Hif-1α Deletion Phenotype of Neonatal Respiratory Distress In Mice

Hypoxia is a state of decreased oxygen reaching the tissues of the body. During prenatal development, the fetus experiences localized occurrences of hypoxia that are essential for proper organogenesis and survival. The response to decreased oxygen availability is primarily regulated by hypoxia-inducible factors (HIFs), a family of transcription factors that modulate the expression of key genes involved in glycolysis, angiogenesis, and erythropoiesis. HIF-1α and HIF-2α, two key isoforms, are important in embryonic development, and likely are involved in lung morphogenesis. We have recently shown that the inducible loss of Hif-1α in lung epithelium starting at E4.5 leads to death within an hour of parturition, with symptoms similar to neonatal respiratory distress syndrome (RDS). In addition to Hif-1α, Hif-2α is also expressed in the developing lung, although the overlapping roles of Hif-1α and Hif-2α in this context are not fully understood. To further investigate the independent role of Hif-2α in lung epithelium and its ability to alter Hif-1α-mediated lung maturation, we generated two additional lung-specific inducible Hif-α knockout models (Hif-2α and Hif-1α+Hif-2α). The intrauterine loss of Hif-2α in the lungs does not lead to decreased viability or observable phenotypic changes in the lung. More interestingly, survivability observed after the loss of both Hif-1α and Hif-2α suggests that the loss of Hif-2α is capable of rescuing the neonatal RDS phenotype seen in Hif-1α-deficient pups. Microarray analyses of lung tissue from these three genotypes identified several factors, such as Scd1, Retlnγ, and Il-1r2, which are differentially regulated by the two HIF-α isoforms. Moreover, network analysis suggests that modulation of hormone-mediated, NF-κB, C/EBPα, and c-MYC signaling are central to HIF-mediated changes in lung development.

Impaired pulmonary vascular development in bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD), the chronic lung disease associated with preterm birth, results from the disruption of normal pulmonary vascular and alveolar growth. Though BPD was once described as primarily due to postnatal injury from mechanical ventilation and oxygen therapy after preterm birth, it is increasingly appreciated that BPD results from antenatal and perinatal factors that interrupt lung development in infants born at the extremes of prematurity. The lung in BPD consists of a simplified parenchymal architecture that limits gas exchange and leads to increased cardiopulmonary morbidity and mortality. This review outlines recent advances in the understanding of pulmonary vascular development and describes how the disruption of these mechanisms results in BPD. We point to future therapies that may augment postnatal vascular growth to prevent and treat this severe chronic lung disease.

Antenatally diagnosed lung malformations: a plea for long-term outcome studies

There is a wide variation in the management of infants with antenatally diagnosed lung malformations, with many paediatric surgeons and respiratory paediatricians recommending early investigations for all infants and a surgical excision for the majority of lesions, while others favour a conservative management for all asymptomatic infants. The benefits and risks of a surgical intervention have to be compared with the natural history of the untreated malformation and cohort studies from foetal diagnosis to adult life are required to provide the relevant evidence. Careful and repeated surveillance of identified foetuses is essential as recent advances in foetal medicine and surgery have improved the outcomes for the small minority, who are at risk of developing hydrops.

Glucocorticoid regulation of lung development: lessons learned from conditional GR knockout mice

Glucocorticoid (GC) steroid hormones have well-characterized roles in the regulation of systemic homeostasis, yet less understood is their known role in utero to mature the developing respiratory system in preparation for birth. During late gestation, endogenously produced GCs thin the interstitial tissue of the lung, causing the vasculature and future airspaces to come into close alignment, allowing for efficient gas exchange at birth. More potent synthetic GCs are also used worldwide to reduce the severity of respiratory distress suffered by preterm infants; however, their clinical benefits are somewhat offset by potential detrimental long-term effects on health and development. Here, we review the recent literature studying both global and conditional gene-targeted respiratory mouse models of either GC deficiency or glucocorticoid receptor ablation. Although some discrepancies exist between these transgenic mouse strains, these models have revealed specific roles for GCs in particular tissue compartments of the developing lung and identify the mesenchyme as the critical site for glucocorticoid receptor-mediated lung maturation, particularly for the inhibition of cell proliferation and epithelial cell differentiation. Specific mesenchymal and epithelial cell-expressed gene targets that may potentially mediate the effect of GCs have also been identified in these studies and imply a GC-regulated system of cross talk between compartments during lung development. A better understanding of the specific roles of GCs in specific cell types and compartments of the fetal lung will allow the development of a new generation of selective GC ligands, enabling better therapeutic treatments with fewer side effects for lung immaturity at birth in preterm infants.

Disrupted lung development and bronchopulmonary dysplasia: opportunities for lung repair and regeneration

PURPOSE OF REVIEW

Advances in medical therapy have increased survival of extremely premature infants and changed the pathology of bronchopulmonary dysplasia (BPD) from one of acute lung injury to a disease of disrupted lung development. With this evolution, new questions emerge regarding the molecular mechanisms that control postnatal lung development, the effect of early disruptions of postnatal lung development on long-term lung function, and the existence of endogenous mechanisms that permit lung regeneration after injury.

RECENT FINDINGS

Recent data demonstrate that a significant component of alveolarization, the final stage of lung development, occurs postnatally. Further, clinical and experimental studies demonstrate that premature birth disrupts alveolarization, decreasing the gas exchange surface area of the lung and causing BPD. BPD is associated with significant short-term morbidity, and new longitudinal, clinical data demonstrate that survivors of BPD have long-standing deficits in lung function and may be at risk for the development of additional lung disease as adults. Unfortunately, current care is mainly supportive with few effective therapies that prevent or treat established BPD. These studies underscore the need to further elucidate the mechanisms that direct postnatal lung growth and develop innovative strategies to stimulate lung regeneration.

SUMMARY

Despite significant improvements in the care and survival of extremely premature infants, BPD remains a major clinical problem. Although efforts should remain focused on the prevention of preterm labor and BPD, novel research aimed at promoting postnatal alveolarization offers a unique opportunity to develop effective strategies to treat established BPD.

Hypoxic pulmonary hypertension of the newborn

Hypoxic pulmonary hypertension of the newborn is characterized by elevated pulmonary vascular resistance and pressure due to vascular remodeling and increased vessel tension secondary to chronic hypoxia during the fetal and newborn period. In comparison to the adult, the pulmonary vasculature of the fetus and the newborn undergoes tremendous developmental changes that increase susceptibility to a hypoxic insult. Substantial evidence indicates that chronic hypoxia alters the production and responsiveness of various vasoactive agents such as endothelium-derived nitric oxide, endothelin-1, prostanoids, platelet-activating factor, and reactive oxygen species, resulting in sustained vasoconstriction and vascular remodeling. These changes occur in most cell types within the vascular wall, particularly endothelial and smooth muscle cells. At the cellular level, suppressed nitric oxide-cGMP signaling and augmented RhoA-Rho kinase signaling appear to be critical to the development of hypoxic pulmonary hypertension of the newborn.

Prenatal vitamin d supplementation and child respiratory health: a randomised controlled trial

BACKGROUND

Observational studies suggest high prenatal vitamin D intake may be associated with reduced childhood wheezing. We examined the effect of prenatal vitamin D on childhood wheezing in an interventional study.

METHODS

We randomised 180 pregnant women at 27 weeks gestation to either no vitamin D, 800 IU ergocalciferol daily until delivery or single oral bolus of 200,000 IU cholecalciferol, in an ethnically stratified, randomised controlled trial. Supplementation improved but did not optimise vitamin D status. Researchers blind to allocation assessed offspring at 3 years. Primary outcome was any history of wheeze assessed by validated questionnaire. Secondary outcomes included atopy, respiratory infection, impulse oscillometry and exhaled nitric oxide. Primary analyses used logistic and linear regression.

RESULTS

We evaluated 158 of 180 (88%) offspring at age 3 years for the primary outcome. Atopy was assessed by skin test for 95 children (53%), serum IgE for 86 (48%), exhaled nitric oxide for 62 (34%) and impulse oscillometry of acceptable quality for 51 (28%). We found no difference between supplemented and control groups in risk of wheeze [no vitamin D: 14/50 (28%); any vitamin D: 26/108 (24%) (risk ratio 0.86; 95% confidence interval 0.49, 1.50; P = 0.69)]. There was no significant difference in atopy, eczema risk, lung function or exhaled nitric oxide between supplemented groups and controls.

CONCLUSION

Prenatal vitamin D supplementation in late pregnancy that had a modest effect on cord blood vitamin D level, was not associated with decreased wheezing in offspring at age three years.

TRIAL REGISTRATION

Controlled-Trials.com ISRCTN68645785.

Management of prenatally diagnosed lung lesions

Prenatal diagnosis provides insight into the in utero evolution of fetal thoracic lesions such as congenital cystic adenomatoid malformation (CCAM), bronchopulmonary sequestration (BPS), or hybrid lesions. Serial sonographic study of fetuses with thoracic lesions has helped define the natural history of these lesions, determine the pathophysiologic features that affect clinical outcome, and formulate in utero and postnatal management based on prognosis.

MicroRNA-mRNA interactions in a murine model of hyperoxia-induced bronchopulmonary dysplasia

Background

Bronchopulmonary dysplasia is a chronic lung disease of premature neonates characterized by arrested pulmonary alveolar development. There is increasing evidence that microRNAs (miRNAs) regulate translation of messenger RNAs (mRNAs) during lung organogenesis. The potential role of miRNAs in the pathogenesis of BPD is unclear.

Results

Following exposure of neonatal mice to 80% O₂ or room air (RA) for either 14 or 29 days, lungs of hyperoxic mice displayed histological changes consistent with BPD. Comprehensive miRNA and mRNA profiling was performed using lung tissue from both O₂ and RA treated mice, identifying a number of dynamically regulated miRNAs and associated mRNA target genes. Gene ontology enrichment and pathway analysis revealed that hyperoxia modulated genes involved in a variety of lung developmental processes, including cell cycle, cell adhesion, mobility and taxis, inflammation, and angiogenesis. MiR-29 was prominently increased in the lungs of hyperoxic mice, and several predicted mRNA targets of miR-29 were validated with real-time PCR, western blotting and immunohistochemistry. Direct miR-29 targets were further validated in vitro using bronchoalveolar stem cells.

Conclusion

In newborn mice, prolonged hyperoxia induces an arrest of alveolar development similar to that seen in human neonates with BPD. This abnormal lung development is accompanied by significant increases in the levels of multiple miRNAs and corresponding decreases in the levels of predicted mRNA targets, many of which have known or suspected roles in pathways altered in BPD. These data support the hypothesis that dynamic regulation of miRNAs plays a prominent role in the pathophysiology of BPD.

Indispensable role of factor for adipocyte differentiation 104 (fad104) in lung maturation

Factor for adipocyte differentiation 104 (fad104) is a regulator of adipogenesis and osteogenesis. Our previous study showed that fad104-deficient mice died immediately after birth, suggesting fad104 to be essential for neonatal survival. However, the cause of this rapid death is unclear. Here, we demonstrate the role of fad104 in neonatal survival. Phenotypic and morphological analyses showed that fad104-deficient mice died due to cyanosis-associated lung dysplasia including atelectasis. Furthermore, immunohistochemistry revealed that FAD104 was strongly expressed in ATII cells in the developing lung. Most importantly, the ATII cells in lungs were immature, and impaired the expression of surfactant-associated proteins. Collectively, these results indicate that fad104 has an indispensable role in lung maturation, especially the maturation and differentiation of ATII cells.

Dynamic lineage analysis of embryonic morphogenesis using transgenic quail and 4D multispectral imaging

We describe the development of transgenic quail that express various fluorescent proteins in targeted manners and their use as a model system that integrates advanced imaging approaches with conventional and emerging molecular genetics technologies. We also review the progression and complications of past fate mapping techniques that led us to generate transgenic quail, which permit dynamic imaging of amniote embryogenesis with unprecedented subcellular resolution.

IUGR differentially alters MeCP2 expression and H3K9Me3 of the PPARγ gene in male and female rat lungs during alveolarization

Intrauterine growth restriction (IUGR) increases the risk of postnatal lung disease, with males more affected. In rat lungs, IUGR impairs alveolarization in conjunction with altered expression of peroxisome proliferator-activated receptor gamma (PPARγ). In non-lung cells, PPARγ transcription is regulated in part by the epigenetic modifying enzyme, and the methyl CpG binding protein 2 (MeCP2). However, it is unknown if IUGR affects MeCP2 expression or its interaction with PPARγ in the rat lung during alveolarization. In this study, we hypothesized that the rat lung would be characterized by the presence of MeCP2 short and long mRNA transcripts, MeCP2 protein isoforms, and the MeCP2 regulatory micro RNA, miR132. We further hypothesized that IUGR would, in a gender-specific manner, alter the levels of MeCP2 components in association with changes in PPARγ mRNA, MeCP2 occupancy at the PPARγ promoters, and PPARγ histone 3 lysine 9 trimethylation (H3K9Me3). To test these hypotheses, we used a well-characterized rat model of uteroplacental insufficiency-induced IUGR. We demonstrated the presence of MeCP2 mRNA, protein, and miR132 in the rat lung throughout alveolarization. We also demonstrated that IUGR alters MeCP2 expression and its interaction with PPARγ in a gender-divergent manner. We conclude that IUGR induces gender-specific alterations in the epigenetic milieu in the rat lung. We speculate that in the IUGR rat lung, this altered epigenetic milieu may predispose to gender-specific alterations in alveolarization.

Abnormal development of the enteric nervous system in rat embryos and fetuses with congenital diaphragmatic hernia

BACKGROUND/AIM

Esophageal dilatation, gastroesophageal reflux, and intestinal obstruction have been demonstrated in CDH survivors. Abnormal esophageal and intestinal innervations were recently found in rats and babies with this disease. Our aim was to further characterize these malformations in embryos and fetal rats exposed to nitrofen.

METHODS

Pregnant rats received either 100 mg nitrofen or vehicle on E9.5. Fetuses were recovered at E15, E18, and E21. Sections of esophagus and small bowel were histochemically stained with acetylcholinesterase (AChE) and immunostained for PGP9.5. PGP9.5 gen protein were measured on E21 and PGP9.5 mRNA on E15, E18 and E21. Comparisons between groups were made with non-parametrics tests.

RESULTS

Histochemistry and immunohistochemistry showed deficient innervation in all anatomical areas studied at E15, E18, and E21, and WB confirmed this decrease in E21 fetuses. PGP9.5 messenger was decreased in nitrofen-exposed animals on E18 (esophagus) or E15 (small bowel), and increased on E21 in the esophagus and E18 in small bowel.

CONCLUSIONS

Development of the enteric nervous system of the esophagus, stomach, and small bowel is deficient in rat embryos and fetuses exposed to nitrofen. These anomalies could account in part for the long-term gastrointestinal morbidity observed in CDH survivors.

Disrupted postnatal lung development in heme oxygenase-1 deficient mice

Background

Heme oxygenase (HO) degrades cellular heme to carbon monoxide, iron and biliverdin. The HO-1 isoform is both inducible and cyto-protective during oxidative stress, inflammation and lung injury. However, little is known about its precise role and function in lung development. We hypothesized that HO-1 is required for mouse postnatal lung alveolar development and that vascular expression of HO-1 is essential and protective during postnatal alveolar development.

Methods

Neonatal lung development in wildtype and HO-1 mutant mice was evaluated by histological and molecular methods. Furthermore, these newborn mice were treated with postnatal dexamethasone (Dex) till postnatal 14 days, and evaluated for lung development.

Results

Compared to wildtype littermates, HO-1 mutant mice exhibited disrupted lung alveolar structure including simplification, disorganization and reduced secondary crest formation. These defects in alveolar development were more pronounced when these mice were challenged with Dex treatment. Expression levels of both vascular endothelial and alveolar epithelial markers were also further decreased in HO-1 mutants after Dex treatment.

Conclusions

These experiments demonstrate that HO-1 is required in normal lung development and that HO-1 disruption and dexamethasone exposure are additive in the disruption of postnatal lung growth. We speculate that HO-1 is involved in postnatal lung development through modulation of pulmonary vascular development.

Regulation of the Pulmonary Circulation in the Fetus and Newborn

During the development of the pulmonary vasculature in the fetus, many structural and functional changes occur to prepare the lung for the transition to air breathing. The development of the pulmonary circulation is genetically controlled by an array of mitogenic factors in a temporo-spatial order. With advancing gestation, pulmonary vessels acquire increased vasoreactivity. The fetal pulmonary vasculature is exposed to a low oxygen tension environment that promotes high intrinsic myogenic tone and high vasocontractility. At birth, a dramatic reduction in pulmonary arterial pressure and resistance occurs with an increase in oxygen tension and blood flow. The striking hemodynamic differences in the pulmonary circulation of the fetus and newborn are regulated by various factors and vasoactive agents. Among them, nitric oxide, endothelin-1, and prostaglandin I2 are mainly derived from endothelial cells and exert their effects via cGMP, cAMP, and Rho kinase signaling pathways. Alterations in these signaling pathways may lead to vascular remodeling, high vasocontractility, and persistent pulmonary hypertension of the newborn.

Understanding the sequence of pulmonary injury in the extremely low birth weight, surfactant-deficient infant

Human lung development begins around day 26 postconception and continues throughout early childhood. Many crucial events can affect this delicate tissue as it develops, leading to altered and abnormal growth and development of the lungs, thereby yielding a variety of morbidities and sometimes even mortality. Understanding the pathophysiology of lung injury in the extremely low birth weight neonate is essential when caring for these infants, especially during the first hours of life. This article provides bedside clinicians with foundational information related to acute lung injury and the sequence of events that can ultimately lead to neonatal chronic lung disease and bronchopulmonary dysplasia.

Lysyl oxidase activity is dysregulated during impaired alveolarization of mouse and human lungs

RATIONALE

Disordered extracellular matrix production is a feature of bronchopulmonary dysplasia (BPD). The basis of this phenomenon is not understood.

OBJECTIVES

To assess lysyl oxidase expression and activity in the injured developing lungs of newborn mice and of prematurely born infants with BPD or at risk for BPD.

METHODS

Pulmonary lysyl oxidase and elastin gene and protein expression were assessed in newborn mice breathing 21 or 85% oxygen, in patients who died with BPD or were at risk for BPD, and in control patients. Signaling by transforming growth factor (TGF-beta) was preemptively blocked in mice exposed to hyperoxia using TGF-beta-neutralizing antibodies. Lysyl oxidase promoter activity was assessed using plasmids containing the lox or loxl1 promoters fused upstream of the firefly luciferase gene.

MEASUREMENTS AND MAIN RESULTS

mRNA and protein levels and activity of lysyl oxidases (Lox, LoxL1, LoxL2) were elevated in the oxygen-injured lungs of newborn mice and infants with BPD or at risk for BPD. In oxygen-injured mouse lungs, increased TGF-beta signaling drove aberrant lox, but not loxl1 or loxl2, expression. Lox expression was also increased in oxygen-injured fibroblasts and pulmonary artery smooth muscle cells.

CONCLUSIONS

Lysyl oxidase expression and activity are dysregulated in BPD in injured developing mouse lungs and in prematurely born infants. In developing mouse lungs, aberrant TGF-beta signaling dysregulated lysyl oxidase expression. These data support the postulate that excessive stabilization of the extracellular matrix by excessive lysyl oxidase activity might impede the normal matrix remodeling that is required for pulmonary alveolarization and thereby contribute to the pathological pulmonary features of BPD.

The etiology of congenital diaphragmatic hernia: still largely unknown?

Congenital diaphragmatic hernia (CDH) is a severe birth defect characterized by a defect in the diaphragm associated with pulmonary hypoplasia and postnatal pulmonary hypertension. Half of the cases present with other non-pulmonary congenital anomalies (so called non-isolated CDH) and in 5-10% of cases there is a chromosomal etiology. The clinical aspects of CDH are well documented but knowledge on the etiology of CDH is largely lacking. Worldwide many researchers have focused research efforts on CDH. Their findings have led to several hypotheses proposing roles for genetic and environmental factors. In this review we have combined these findings with our own research on the genetics of CDH in results from recent literature and propose a theory on the etiology of CDH. We also propose a protocol for the CDH patient that will help clinicians and researchers to obtain maximal success out of their collaborations that will eventually lead to unravelling the etiology of this intriguing birth defect.

Global and gene-specific translational regulation in rat lung development

During the peripartum period, the lung must respond to dramatic changes in circulating hormones, nutritional factors, and physiologic signals during its transition to becoming the organ of gas exchange. Protein synthesis consumes a significant proportion of metabolic resources and is inhibited by many environmental stresses. We hypothesized that translational control mechanisms play a role in the perinatal lung. Immunoblots of late-gestation (Fetal Day [FD] 17-22) rat lung extracts revealed gradual decreases in phosphorylated forms of the mammalian target of rapamycin effectors, eukaryotic initiation factor (eIF) 4E-binding protein, p70 S6 kinase, and ribosomal protein S6, followed by sharp increases on Postnatal Day 1 (P1). Immunohistochemistry showed phospho-S6 staining was most prominent in epithelial cells of the large and small airways. m(7)GTP-sepharose pulldown experiments showed a decrease in association of translation initiation factor, eIF4E, with its inhibitor, eIF4E-binding protein, and a concomitant increase in eIF4E association with eIF4G immediately after birth, and polysome profiles confirmed a decrease in abundance of large polysomes between FD19 and FD22, which was reversed on P1. Microarray analysis of polysomal versus total RNA from FD19, FD22, and P1 lungs was used to identify specific genes, the association of which with large polysomes changed either pre- or postnatally. RT-PCR and Northern blotting were used to confirm translational changes in selected candidate genes, including a prenatal increase in IL-18 and a postnatal decrease in regulatory subunit 2 of protein phosphatase 1. Translational regulation of IL-18 and protein phosphatase 1 regulatory (inhibitor) subunit 2 is gene-specific, as these changes contrast with the corresponding global changes in polysome abundance.

HIF1alpha is essential for normal intrauterine differentiation of alveolar epithelium and surfactant production in the newborn lung of mice

Neonatal respiratory distress syndrome (RDS) is mainly the result of perturbation in surfactant production and is a common complication seen in premature infants. Normal fetal lung development and alveolar cell differentiation is regulated by a network of transcription factors. Functional loss of any of these factors will alter the developmental program and impact surfactant production and normal gas exchange. During development, the fetus is exposed to varying oxygen concentrations and must be able to quickly adapt to these changes in order to survive. Hypoxia-inducible factor 1alpha (HIF1alpha) is the primary transcription factor that is responsible for regulating the cellular response to changes in oxygen tension and is essential for normal development. Its role in lung maturation is not well defined and to address this knowledge gap, a lung-specific HIF1alpha knock-out model has been developed. Loss of HIF1alpha early in lung development leads to pups that die within hours of parturition, exhibiting symptoms similar to RDS. Lungs from these pups display impaired alveolar epithelial differentiation and an almost complete loss of surfactant protein expression. Ultrastructural analysis of lungs from HIF1alpha deletion pups had high levels of glycogen, aberrant septal development, and decreased expression of several factors necessary for proper lung development, including HIF2alpha, beta-catenin, and vascular endothelial growth factor. These results suggest that HIF1alpha is essential for proper lung maturation and alteration in its normal signaling during premature delivery might explain the pathophysiology of neonatal RDS.

A neonate with coexisting congenital cystic adenomatoid malformation of the lung and alveolar capillary dysplasia: a case report with review of literature

OBJECTIVE

First report of a term neonate with coexistent congenital cystic adenomatoid malformation (CCAM) of the lung and alveolar capillary dysplasia (ACD).

METHODS AND DESIGN

Case report and literature review. Our institutional review board waived the need for consent.

SETTING

We describe a term neonate with antenatally diagnosed CCAM and persistent pulmonary hypertension of the newborn (PPHN) who underwent right upper lobe resection on day 9 of life. Histology confirmed CCAM but closer examination also showed ACD. Postoperatively pulmonary hypertension persisted despite high-frequency oscillation and inhaled nitric oxide, and she was placed on extracorporeal membrane oxygenation. Due to the lack of any improvement, intensive care treatment was withdrawn 4 days later.

CONCLUSIONS

This is the first description of an association between these two rare malformations. Although a causative link between CCAM and ACD is possible, it is unlikely. ACD should always be considered as a cause of severe PPHN when persistent beyond 10 days, even if another etiology of PPHN is present.

Chick pulmonary Wnt5a directs airway and vascular tubulogenesis

Wnt5a is an important factor patterning many aspects of early development, including the lung. We find pulmonary non-canonical Wnt5a uses Ror2 to control patterning of both distal air and vascular tubulogenesis (alveolarization). Lungs with mis/overexpressed Wnt5a develop with severe pulmonary hypoplasia associated with altered expression patterns of Shh, L-CAM, fibronectin, VEGF and Flk1. This hypoplastic phenotype is rescued by either replacement of the Shh protein or inhibition of fibronectin function. We find that the effect of Wnt5a on vascular patterning is likely to be through fibronectin-mediated VEGF signaling. These results demonstrate the pivotal role of Wnt5a in directing the essential coordinated development of pulmonary airway and vasculature, by affecting fibronectin levels directly, and by affecting the fibronectin pattern of expression through its regulation of Shh. Data herein suggest that Wnt5a functions in mid-pulmonary patterning (during alveolarization), and is distinct from the Wnt canonical pathway which is more important in earlier lung development.

N-terminal-pro-B type natriuretic peptide as a useful tool to evaluate pulmonary hypertension and cardiac function in CDH infants

OBJECTIVE

In congenital diaphragmatic hernia (CDH) the severity of pulmonary hypertension (PH) is considered, by several authors, determinant of clinical outcome. Plasmatic N-terminal-pro-B type natriuretic peptide (NT-proBNP) might be useful in diagnosis and management of PH in newborns, although its interest in CDH infants remains to be defined. Early NT-proBNP levels were assessed in CDH infants and correlated with cardiovascular echocardiographic parameters.

PATIENTS AND METHODS

28 newborns, CDH and age-matched controls were enrolled in a prospective study. Clinical condition, NT-proBNP plasmatic levels, echo parameters of PH and biventricular function were assessed at 24 h after delivery as well as survival outcome.

RESULTS

Estimated mean pulmonary pressure and NT-proBNP were significantly higher in CDH than control infants. NT-proBNP significantly correlated with estimated pulmonary artery pressure, right ventricular Tei index, and tricuspid E/A ratio. Additionally, we found that CDH infants with NT-proBNP >11,500 pg/ml experienced a worse prognosis.

CONCLUSIONS

We demonstrated that PH is associated with NT-proBNP elevation and diastolic impairment in CDH infants. Early elevations in NT-proBNP levels seem to alert for a subset of CDH infants with worse prognosis.

Serum and glucocorticoid-inducible kinase in pulmonary tissue of preterm fetuses exposed to chorioamnionitis

OBJECTIVES

The interaction between inflammation and transepithelial Na(+) transport is poorly understood. Chorioamnionitis has been shown to be associated with preterm labor and postnatal pulmonary morbidity of preterm infants. The human isoform of serum and glucocorticoid-inducible kinase (SGK1) is upregulated by proinflammatory cytokines and stimulates epithelial Na(+) channel ENaC and the Na(+)/K(+)-ATPase activity, an effect presumably participating in the regulation of transepithelial Na(+) transport.

STUDY DESIGN

Lung tissue sections from 31 stillborn fetuses (range 21-41 weeks of gestational age) with or without chorioamnionitis were analyzed. Macrophages, neutrophils and lymphocytes were stained immunohistochemically. In addition, in situ hybridization for the detection of SGK1 mRNA was performed in fetal lung tissue. Positively labeled cells were compared by semiquantitative assessment.

RESULTS

A marked influx of macrophages into the pulmonary tissue of fetuses exposed to intrauterine inflammation when compared to fetuses without exposure to chorioamnionitis was observed (p < 0.05). There was also a tendency towards an increased density of neutrophils in fetuses exposed to chorioamnionitis. However, only small numbers of lymphocytes were detected in both groups. In fetuses exposed to chorioamnionitis, 6 of 8 fetuses did not express SGK1; however, in the group of fetuses without exposure to intrauterine inflammation 15 of 23 cases exhibited a profound SGK1 detection rate in lung tissue and airway epithelium, independent of the gestational age of the fetuses (p < 0.05).

CONCLUSIONS

Human serine threonine kinase SGK1 mRNA is observed in fetal lung tissue. On the basis of this study, we speculate that exposure to chorioamnionitis is associated with a downregulation of SGK1 in fetal lung tissue. The possible consequences of a decreased rate of SGK1 mRNA could be an impaired ability to clear the lungs from excessive fluid immediately after preterm birth.

The current state of congenital tracheal stenosis

Congenital tracheal stenosis (CTS) is an uncommon condition that has challenged pediatric surgeons for decades. Patients with CTS can present with a wide spectrum of symptoms and varying degrees of severity. In addition, a variety of techniques have been devised to repair this malformation. A review of these procedures and our suggestions for clinical standards and practice guidelines will be presented in this paper. A retrospective review of the literature on CTS from 1964 to 31 March, 2006. There is not one standard technique for the repair of CTS, as individualized approach to each patient and airway lesion is necessary to optimize patient management; nevertheless there is a consensus about segmental resection and anastomosis being best for short segment stenosis while slide tracheoplasty is most effective for the long-segment ones. Conservative management is also an option for select group of patients with careful and close follow up. Survival following surgery over the years has improved, but mortality remained high, particularly in a specific subset of patients presenting at the age less than 1 month with associated cardiac malformations. In conclusion, CTS remains a significant challenge for pediatric surgeons. Additional research is required to improve our understanding of the pathogenesis of CTS, and to develop evidence-based treatment protocols for the entire spectrum of presentation including conservative management.

Linking animal models to human congenital diaphragmatic hernia

BACKGROUND

Congenital diaphragmatic hernia (CDH) is a major life-threatening malformation, occurring in approximately 1 in 3,000 live births. Over the years, different animal models have been used to gain insight into the etiology of this complex congenital anomaly and to develop treatment strategies. However, to date the pathogenic mechanism is still not understood, and treatment remains difficult because of the associated pulmonary hypoplasia and pulmonary hypertension.

METHODS

In this review, data available from several animal models will be discussed. The retinoic acid signaling pathway (RA pathway, retinoid pathway) will be addressed as a developmental pathway that is potentially disrupted in the pathogenesis of CDH. Furthermore, genetic factors involved in diaphragm and lung development will be discussed.

CONCLUSIONS

With this review article, we aim to provide a concise overview of the current most important experimental genetic data available in the field of CDH.

Prenatally diagnosed fetal lung lesions with associated conotruncal heart defects: Is there a genetic association?

Congenital lung malformation can easily be diagnosed by prenatal ultrasound. Associated extrapulmonary malformations such as heart defects and chromosomal aberrations are rare.

OBJECTIVE

The objective of this study was to describe the natural history, outcome and other associated malformations in fetuses with lung lesions and an associated heart defect.

METHODS

Retrospective analysis of 4 cases of prenatally diagnosed fetal CCAMs and hybrid lesions with an associated heart defect and review of 8 cases in the literature.

RESULTS

At a single referral center 1.9% of the fetuses with Congenital cystic adenomatoid malformation (CCAM) were diagnosed with an associated heart defect. Seven of the total 12 cases (58%) reviewed had a conotruncal heart abnormality. Chromosomal abnormalities were found in 5 (42%) of the cases.

CONCLUSION

This retrospective review shows that karyotyping in fetal lung lesions with an associated heart defect or isolated large lung lesions is indicated. It also suggests that there is a subpopulation of fetuses with CCAMs who have conotruncal heart defects. This finding may suggest a common genetic background.

Does bronchopulmonary dysplasia change the postoperative outcome of herniorrhaphy in premature babies?

BACKGROUND

Inguinal hernia is a common surgical condition in premature neonates. Because of physiological immaturity, they can present with lung-related diseases, such as bronchopulmonary dysplasia (BPD), which may influence the time for operation and the postoperative outcome after hernia repair. The aim of this study was to analyze the role of BPD in the outcome of premature infants who underwent herniorrhaphy.

METHODS

Fifty-two premature infants who underwent hernia repair from 1996 to 2004 at CAISM-UNICAMP were included in this study. Seventeen babies had BPD and 35 did not. The features reviewed included: (i) associated preoperative morbidity; (ii) birth data and the hernia; and (iii) hernia diagnosis, surgery and postoperative outcome data. Three sets of analysis were undertaken. The first compared features with and without BPD. The second was an univariate analysis to detect associations between those features and postoperative complications. Finally, a multivariate analysis to determine the effect of BPD when adjusted for other factors.

RESULTS

Some features were different between the studied groups, such as birth weight, age at herniorrhaphy and time of preoperative mechanical ventilation. There was no statistical difference in weight at surgery, duration of postoperative ventilation and weight at discharge between those with BPD and those without. Univariate and multivariate analysis found no association between different studied variables, including BPD, and incidence of postoperative respiratory complications.

CONCLUSION

These data suggest that all premature infants, with or without BPD, should be treated with equal concern regarding the possibility of postoperative pulmonary complications.

Experiences in the Perinatal Management of Congenital Diaphragmatic Hernia during the Last 15 Years in a Tertiary Referral Institute

OBJECTIVE

Review of cases of perinatally diagnosed congenital diaphragmatic hernias with special regard to time of diagnosis, organs herniated into the thorax, associated malformations, and outcomes.

METHODS

We analyzed the data of 106 cases between July 1, 1990, and June 30, 2005. The observation period was analyzed in two parts.

RESULTS

Prenatal ultrasound was performed in 89.6% (95/106) of the cases. 51.7% (46/89) of the pre- and postnatally verified congenital diaphragmatic hernia cases were diagnosed before the 24th week of gestation. 11% (11/100) of the hernias were identified postnatally. 71% (71/100) of the cases were associated with other malformations. The hernia was on the left side in 86% (86/100) and bilateral in 5% (5/100) of the cases. Between 1990 and 1997, the proportion of right-sided hernias was 4.3% (2/46), while during the second period it was 13% (7/54). 27.5% (14/51) of the newborns survived the perinatal period. The survival rate of the newborns delivered by caesarean section was three times higher than that of infants delivered vaginally. In the latter group, the rate of premature deliveries was considerably higher. The pregnancy was terminated in 45% (40/89) of the cases. 15% (6/40) of the terminated cases were isolated. Intrauterine or intrapartum deaths occurred in 5.6% (5/89) of the prenatally diagnosed cases. Simultaneous thoracic herniation of liver, spleen, or stomach decreased the survival rate. In these cases, the discharge rate was between 6 and 22%.

CONCLUSIONS

According to the analysis of 15-year data, the herniated organs, multiple malformations, as well as the mode of delivery influence the survival in a large number of cases. Early diagnosis predicts a large hernia, a higher malformation rate, and a less favourable prognosis.

Predicting inadequate long-term lung development in children with congenital diaphragmatic hernia: an analysis of longitudinal changes in ventilation and perfusion

PURPOSE

Infants born with congenital diaphragmatic hernia (CDH) demonstrate a wide variability in postnatal catch-up lung growth. The goals of this study were to assess the pulmonary development of children born with CDH using sequential ventilation-perfusion (V/Q) scintigraphy and to identify the perinatal factors that correspond to a progressive V/Q mismatch.

METHODS

The records of 137 patients seen between 1990 and 2005 in a multidisciplinary CDH clinic were reviewed. Changes in the ipsilateral V/Q quotient were compared in 46 patients who had 2 or more studies with the following variables: sex, patch repair, laterality, gestational age, and use of extracorporeal membrane oxygenation. An abnormal V/Q quotient was defined as greater than 1.2 (reference range, 0.8-1.2).

RESULTS

Abnormal V/Q scans were identified in 28 (61%) of the 46 patients at the time of the last V/Q study. Patients who underwent a patch repair had nearly 7 times the risk (P < .001) of developing an ipsilateral V/Q mismatch. The use of extracorporeal membrane oxygenation had a variable effect on the probability of an abnormal V/Q study finding. No other variable was significant.

CONCLUSIONS

Many children with CDH develop significant and progressive V/Q mismatches. Although some perinatal variables appear to be predictive of this phenomenon, they may simply be surrogates for a greater degree of pulmonary hypoplasia present at birth. This subpopulation of CDH survivors is an identifiable group clearly at risk and thus requires long-term follow-up.

The Respiratory System

One of the most critical events of birth is the conversion of the fluid-filled lung, unimportant to fetal intrauterine existence, into a hollow organ distended with air and capable of gaseous exchange sufficient to support life. Indeed, it has been argued that the major determinant of perinatal survival is respiratory function (Wigglesworth and Desai 1982).

The failure to make this conversion adequately may lead, directly or indirectly, to infant death, and the pathologist often needs to assess the contribution made by respiratory inadequacy to the sequence of events leading to death. In the preterm infant, problems are mainly related to pulmonary immaturity and associated therapy. In the mature infant, birth asphyxia primarily results in cerebral damage but can engender significant respiratory complications when associated with aspiration of meconium. Even in stillbirths, where primary pulmonary pathology is rarely a cause of death, lung pathology may provide clues to antecedent events. Poor lung growth and maturation may point to the presence of pathology elsewhere. Consequently, adequate pathological investigation of the fetal or infant respiratory system is critical in any perinatal autopsy.

Hypoxia-inducible factors in the first trimester human lung

Lung development takes place in a relatively low-oxygen environment, which is beneficial for lung organogenesis, including vascular development. Hypoxia-inducible factor (HIF)-1 plays an important role in mediating oxygen-regulated events. HIF-1 is stable and initiates gene transcription under hypoxia, whereas in normoxia, interaction with the von Hippel-Lindau (VHL) tumor suppressor protein leads to rapid degradation of the HIF-1alpha subunit. Interaction with VHL requires hydroxylation of HIF-1alpha proline residues by prolyl hydroxylases (PHDs). We investigated the expression of the various components regulating HIF-1alpha stability in first trimester (8-14 weeks) human lungs. Spatial expression was assessed by immunohistochemistry and temporal expression by quantitative PCR. Immunoreactivity for PHD1, PHD3, and seven in absentia homolog (SIAH)1 was noted in the pulmonary epithelium. PHD2 was not expressed in the airway epithelium, but in the lung parenchyma. HIF-1alpha and vascular endothelial growth factor (VEGF) immunoreactivity were primarily detected in the branching epithelium. HIF-2alpha and ARNT proteins localized to the developing epithelium as well as mesenchymal, most likely vascular, structures in the parenchyma. VEGF receptor 2 (VEGFR2) was found in the subepithelium as well as in vascular structures of the mesenchyme. All components of the VEC complex (VHL, NEDD8, and Cullin2) were found in the epithelium. Quantitative PCR analysis demonstrated that VEGF, VEGFR1, HIF-1alpha, HIF-2alpha, ARNT, PHD1, PHD2, PHD3, and SIAH1 gene expression was constant during early pulmonary organogenesis. Cumulatively, the data suggest that the lung develops in a low-oxygen environment that allows for proper vascular development through HIF-regulated pathways.

Bronchial atresia is common to extralobar sequestration, intralobar sequestration, congenital cystic adenomatoid malformation, and lobar emphysema

Congenital cystic adenomatoid malformation (CCAM), intralobar sequestration (ILS), extralobar sequestration (ELS), and lobar emphysema (LE) are well-accepted entities; however, certain findings are common to all, particularly the parenchymal maldevelopment characterizing CCAM. Isolated reports have described bronchial atresia (BA) in some specimens in all 4 entities, but this finding has not been evaluated in a prospective manner. With the aid of a dissecting microscope, we prospectively examined 47 lung specimens resected during the past 4 years and submitted with the clinical impression of ELS (n=11), ILS (n=11), CCAM (n=20), LE (n=4), and airway-esophageal communication (n=1). Most lesions were detected by prenatal ultrasound and were resected during infancy. The clinical impression and pathologic findings were compared. Pathologic examination revealed atresia of a lobar, segmental, or subsegmental bronchus in 100% of ELS, 82% of ILS, 70% of CCAM, and 50% of LE (those clinically recognized to have BA or minor CCAM) cases. Parenchymal maldevelopment that characterizes CCAM was present in 100% of CCAM cases (as expected by definition) as well as in 91% of ELS, 91% of ILS, and 50% of LE (those with BA) cases. Bronchial atresia is present in all ELS, most ILS and CCAM, and some LE cases, and its detection is greatly enhanced with the dissecting microscope. Bronchial atresia and CCAM nearly always coexist. It may be that both have the same etiopathogenesis with anatomic differences accounted for by aberrant genetic programs or other insults, perhaps modified by time of onset or duration.

Cystic adenomatoid malformation of the lung: review of genetics, prenatal diagnosis, and in utero treatment

Prenatal identification of lung abnormalities has increased with prenatal surveillance. Treatment usually requires serial ultrasound observation but in rare situations in utero therapy may be required for fetal survival. We review the genetics, prenatal evaluation, and treatment of lung abnormalities with congenital cystic adenomatoid malformation (CCAM). Other lung lesions, bronchopulmonary sequestration (BPS), hybrid lesions involving both malformations, congenital lobar emphysema (CLE), are briefly included as differential diagnosis options. Outcome of fetuses identified to have CCAM lung abnormalities resulting in fetal hydrops and having in utero therapy (thoracoamniotic shunting, fetal thoracotomy, EXIT delivery) are discussed. In the appropriate situation, this maternal fetal surgery approach for CCAM is life-saving for the affected fetus with acceptable maternal morbidity risks in the present and future pregnancies.

Spontaneous regression of congenital cystic adenomatoid malformation of the lung: longitudinal examinations by magnetic resonance imaging

We report a case of large cystic adenomatoid malformation of the lung (CCAM), which occupied almost the entire left lung with a prominent mediastinal shift at 24 weeks of gestation. The volume of the lesion, determined by magnetic resonance imaging (MRI), was 27.0 cm3. Subsequent MRI and ultrasound examinations revealed a spontaneous resolution of the lesion at 32 and 36 weeks of gestation without a mediastinal shift, when the lesion volume was 12.8 cm3 and 5.6 cm3, respectively. At 37 weeks of gestation, a mature male baby weighing 2638 g with an Apgar score of 7 was delivered by elective cesarean section. A lobectomy of the left upper lobe of the lung was carried out at 3 days of age, due to an enlargement of the CCAM after birth.

l7Rn6 encodes a novel protein required for clara cell function in mouse lung development

The highly secretory Clara cells play a pivotal role in protecting the lung against inflammation and oxidative stress. This study reports the positional cloning of a novel protein required for Clara cell physiology in mouse lung development. The perinatal lethal N-ethyl-N-nitrosourea-induced l7Rn6(4234SB) allele contained a nonsense mutation in the previously hypothetical gene NM_026304 on chromosome 7. Whereas l7Rn6 mRNA levels were indistinguishable from wild type, l7Rn6(4234SB) homozygotes exhibited decreased expression of the truncated protein, suggesting protein instability. During late gestation, l7Rn6 was widely expressed in the cytoplasm of lung epithelial cells, whereas perinatal expression was restricted to the bronchiolar epithelium. Homozygosity for the l7Rn6(4234SB) allele did not affect early steps in lung patterning, growth, or cellular differentiation. Rather, mutant lungs demonstrated severe emphysematous enlargement of the distal respiratory sacs at birth. Clara cell pathophysiology was evident from decreased cytoplasmic CCSP and SP-B protein levels, enlargement and disorganization of the Golgi complex, and formation of aberrant vesicular structures. Additional support for a role in the secretory pathway derived from l7Rn6 localization to the endoplasmic reticulum. Thus, l7Rn6 represents a novel protein required for organization and/or function of the secretory apparatus in Clara cells in mouse lung.