Blastocyst complementation reveals that NKX2-1 establishes the proximal-peripheral boundary of the airway epithelium.

BACKGROUND: Distinct boundaries between the proximal conducting airways and more peripheral-bronchial regions of the lung are established early in foregut embryogenesis, demarcated in part by the distribution of SOX family and NKX2-1 transcription factors along the cephalo-caudal axis of the lung. We used blastocyst complementation to identify the role of NKX2-1 in the formation of the proximal-peripheral boundary of the airways in mouse chimeric embryos. RESULTS: While Nkx2-1-/- mouse embryos form primordial tracheal cysts, peripheral pulmonary structures are entirely lacking in Nkx2-1-/- mice. Complementation of Nkx2-1-/- embryos with NKX2-1-sufficient embryonic stem cells (ESCs) enabled the formation of all tissue components of the peripheral lung but did not enhance ESC colonization of the most proximal regions of the airways. In chimeric mice, a precise boundary was formed between NKX2-1-deficient basal cells co-expressing SOX2 and SOX9 in large airways and ESC-derived NKX2-1+ SOX9+ epithelial cells of smaller airways. NKX2-1-sufficient ESCs were able to selectively complement peripheral, rather than most proximal regions of the airways. ESC complementation did not prevent ectopic expression of SOX9 but restored ß-catenin signaling in Nkx2-1-/- basal cells of large airways. CONCLUSIONS: NKX2-1 and ß-catenin function in an epithelial cell-autonomous manner to establish the proximal-peripheral boundary along developing airways.

Fetal endoscopic tracheal occlusion reverses the natural history of right-sided congenital diaphragmatic hernia: European multicenter experience.

OBJECTIVE: To evaluate the neonatal outcome of fetuses with isolated right-sided congenital diaphragmatic hernia (iRCDH) based on prenatal severity indicators and antenatal management. METHODS: This was a retrospective review of prospectively collected data on consecutive cases diagnosed with iRCDH before 30 weeks' gestation in four fetal therapy centers, between January 2008 and December 2018. Data on prenatal severity assessment, antenatal management and perinatal outcome were retrieved. Univariate and multivariate logistic regression analysis were used to identify predictors of survival at discharge and early neonatal morbidity. RESULTS: Of 265 patients assessed during the study period, we excluded 40 (15%) who underwent termination of pregnancy, two cases of unexplained fetal death, two that were lost to follow-up, one for which antenatal assessment of lung hypoplasia was not available and six cases which were found to have major associated anomalies or syndromes after birth. Of the 214 fetuses with iRCDH included in the neonatal outcome analysis, 86 were managed expectantly during pregnancy and 128 underwent fetal endoscopic tracheal occlusion (FETO) with a balloon. In the expectant-management group, lung size measured by ultrasound or by magnetic resonance imaging was the only independent predictor of survival (observed-to-expected lung-to-head ratio (o/e-LHR) odds ratio (OR), 1.06 (95% CI, 1.02-1.11); P = 0.003). Until now, stratification for severe lung hypoplasia has been based on an o/e-LHR cut-off of 45%. In cases managed expectantly, the survival rate was 15% (4/27) in those with o/e-LHR ≤ 45% and 61% (36/59) for o/e-LHR > 45% (P = 0.001). However, the best o/e-LHR cut-off for the prediction of survival at discharge was 50%, with a sensitivity of 78% and specificity of 72%. In the expectantly managed group, survivors with severe pulmonary hypoplasia stayed longer in the neonatal intensive care unit than did those with mildly hypoplastic lungs. In fetuses with an o/e-LHR ≤ 45% treated with FETO, survival rate was higher than in those with similar lung size managed expectantly (49/120 (41%) vs 4/27 (15%); P = 0.014), despite higher prematurity rates (gestational age at birth: 34.4 ± 2.7 weeks vs 36.8 ± 3.0 weeks; P < 0.0001). In fetuses treated with FETO, gestational age at birth was the only predictor of survival (OR, 1.25 (95% CI, 1.04-1.50); P = 0.02). CONCLUSIONS: Antenatal measurement of lung size can predict survival in iRCDH. In fetuses with severe lung hypoplasia, FETO was associated with a significant increase in survival without an associated increase in neonatal morbidity. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Genotype-Phenotype Correlation of Tracheal Cartilaginous Sleeves and Fgfr2 Mutations in Mice.

OBJECTIVES: To characterize tracheal cartilage morphology in mouse models of fibroblast growth factor receptor (Fgfr2)-related craniosynostosis syndromes. To establish relationships between specific Fgfr2 mutations and tracheal cartilaginous sleeve (TCS) phenotypes in these mouse models. METHODS: Postnatal day 0 knock-in mouse lines with disease-specific genetic variations in the Fgfr2 gene (Fgfr2C342Y/C342Y , Fgfr2C342Y/+ , Fgfr2+/Y394C , Fgfr2+/S252W , and Fgfr2+/P253R ) as well as line-specific controls were utilized. Tracheal cartilage morphology as measured by gross analyses, microcomputed tomography (µCT), and histopathology were compared using Chi-squared and single-factor analysis of variance statistical tests. RESULTS: A greater proportion of rings per trachea were abnormal in Fgfr2C342Y/+ tracheas (63%) than Fgfr2+/S252W (17%), Fgfr2+/P253R (17%), Fgfr2+/Y394C (12%), and controls (10%) (P < .001 for each vs. Fgfr2C342Y/+ ). TCS segments were found only in Fgfr2C342Y/C342Y (100%) and Fgfr2C342Y/+ (72%) tracheas. Cricoid and first-tracheal ring fusion was noted in all Fgfr2C342Y/C342Y and 94% of Fgfr2C342Y/+ samples. The Fgfr2C342Y/C342Y and Fgfr2C342Y/+ groups were found to have greater areas and volumes of cartilage than other lines on gross analysis and µCT. Histologic analyses confirmed TCS among the Fgfr2C342Y/C342Y and Fgfr2C342Y/+ groups, without appreciable differences in cartilage morphology, cell size, or density; no histologic differences were observed among other Fgfr2 lines compared to controls. CONCLUSION: This study found TCS phenotypes only in the Fgfr2C342Y mouse lines. These lines also had increased tracheal cartilage compared to other mutant lines and controls. These data support further study of the Fgfr2 mouse lines and the investigation of other Fgfr2 variants to better understand their role in tracheal development and TCS formation. LEVEL OF EVIDENCE: NA Laryngoscope, 131:E1349-E1356, 2021.

New device permitting non-invasive reversal of fetal endoscopic tracheal occlusion: ex-vivo and in-vivo study.

OBJECTIVE: One of the drawbacks of fetal endoscopic tracheal occlusion (FETO) for congenital diaphragmatic hernia is the need for a second invasive intervention to re-establish airway patency. The 'Smart-TO' device is a new balloon for FETO that deflates spontaneously when placed in a strong magnetic field, therefore overcoming the need for a second procedure. The safety and efficacy of this device have not yet been demonstrated. The aim of this study was to investigate the reversibility, local side effects and occlusiveness of the Smart-TO balloon, both in a simulated in-utero environment and in the fetal lamb model. METHODS: First, the reversibility of tracheal occlusion by the Smart-TO balloon was tested in a high-fidelity simulator. Following videoscopic tracheoscopic balloon insertion, the fetal mannequin was placed within a 1-L water-filled balloon to mimic the amniotic cavity. This was held by an operator in front of their abdomen, and different fetal and maternal positions were simulated to mimic the most common clinical scenarios. Following exposure to the magnetic field generated by a 1.5-T magnetic resonance (MR) machine, deflation of the Smart-TO balloon was assessed by tracheoscopy. In cases of failed deflation, the mannequin was reinserted into a water-filled balloon for additional MR exposure, up to a maximum of three times. Secondly, reversibility, occlusiveness and local effects of the Smart-TO balloon were tested in vivo in fetal lambs. Tracheal occlusion was performed in fetal lambs on gestational day 95 (term, 145 days), either using the balloon currently used in clinical practice (Goldbal2) (n = 5) or the Smart-TO balloon (n = 5). On gestational day 116, the presence of the balloon was assessed by tracheoscopy. Deflation was performed by puncture (Goldbal2) or MR exposure (Smart-TO). Six unoccluded fetal lambs served as controls. Following euthanasia, the lung-to-body-weight ratio (LBWR), lung morphometry and tracheal circumference were assessed. Local tracheal changes were measured using a hierarchical histologic scoring system. RESULTS: Ex vivo, Smart-TO balloon deflation occurred after a single MR exposure in 100% of cases in a maternal standing position with the mannequin at a height of 95 cm (n = 32), 55 cm (n = 8) or 125 cm (n = 8), as well as when the maternal position was 'lying on a stretcher' (n = 8). Three out of eight (37.5%) balloons failed to deflate at first exposure when the maternal position was 'sitting in a wheelchair'. Of these, two balloons deflated after a second MR exposure, but one balloon remained inflated after a third exposure. In vivo, all Smart-TO balloons deflated successfully. The LBWR in fetal lambs with tracheal occlusion by a Smart-TO balloon was significantly higher than that in unoccluded controls, and was comparable with that in the Goldbal2 group. There were no differences in lung morphometry and tracheal circumference between the two balloon types. Tracheal histology showed minimal changes for both balloons. CONCLUSIONS: In a simulated in-utero environment, the Smart-TO balloon was effectively deflated by exposure of the fetus in different positions to the magnetic field of a 1.5-T MR system. There was only one failure, which occurred when the mother was sitting in a wheelchair. In healthy fetal lambs, the Smart-TO balloon is as occlusive as the clinical standard Goldbal2 system and has only limited local side effects. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Chloride channels regulate differentiation and barrier functions of the mammalian airway.

The conducting airway forms a protective mucosal barrier and is the primary target of airway disorders. The molecular events required for the formation and function of the airway mucosal barrier, as well as the mechanisms by which barrier dysfunction leads to early onset airway diseases, remain unclear. In this study, we systematically characterized the developmental landscape of the mouse airway using single-cell RNA sequencing and identified remarkably conserved cellular programs operating during human fetal development. We demonstrated that in mouse, genetic inactivation of chloride channel Ano1/Tmem16a compromises airway barrier function, results in early signs of inflammation, and alters the airway cellular landscape by depleting epithelial progenitors. Mouse Ano1-/-mutants exhibited mucus obstruction and abnormal mucociliary clearance that resemble the airway defects associated with cystic fibrosis. The data reveal critical and non-redundant roles for Ano1 in organogenesis, and show that chloride channels are essential for mammalian airway formation and function.

Survival outcome in severe left-sided congenital diaphragmatic hernia with and without fetal endoscopic tracheal occlusion in a country with suboptimal neonatal management.

OBJECTIVE: To evaluate the impact of fetal endoscopic tracheal occlusion (FETO) on improving survival of fetuses with severe left-sided congenital diaphragmatic hernia (CDH), as compared with contemporaneous cases managed expectantly during pregnancy, in a country with suboptimal neonatal management. METHODS: In this prospective cohort study, consecutive fetuses with isolated left-sided CDH, normal karyotype and severe pulmonary hypoplasia (defined as liver herniation and observed/expected lung-to-head circumference ratio below 26%) were selected for FETO at less than 32 weeks of gestation in a single tertiary referral center in Queretaro, Mexico. Postnatal outcome (survival up to 28 days after birth) was compared between fetuses treated with FETO and contemporaneous cases with similar lung size managed expectantly during pregnancy. RESULTS: Twenty-five fetuses with isolated severe left-sided CDH treated with FETO were matched individually with 25 cases managed expectantly during pregnancy. Endotracheal placement of the balloon was performed successfully on the first attempt in all cases. The median gestational age (GA) at balloon placement was 29.1 (range, 25.6-31.8) weeks and 34.1 (range, 30.0-36.1) weeks at balloon removal. There were no technical problems with the introduction or removal of the balloon in any cases. The median GA at delivery was significantly lower in the group treated with FETO than in those managed expectantly (35.3 vs 37.7 weeks; P = 0.04). The survival rate was significantly higher in the group treated with FETO than in those without fetal intervention (32% vs 0%; P < 0.001). CONCLUSION: In settings with suboptimal neonatal management, FETO was associated with improved neonatal survival in fetuses with isolated left-sided CDH and severe pulmonary hypoplasia. Copyright © 2020 ISUOG. Published by John Wiley & Sons Ltd.

Resultado de supervivencia en una hernia diafragmática congénita grave del lado izquierdo, con y sin oclusión traqueal endoscópica fetal en un país con un tratamiento neonatal subóptimo OBJETIVO: Evaluar el impacto de la oclusión traqueal endoscópica fetal (OTEF) en la mejora de la supervivencia de los fetos con hernia diafragmática congénita (HDC) grave del lado izquierdo, en comparación con los casos actuales tratados como embarazo gestante, en un país con un tratamiento neonatal subóptimo. MÉTODOS: En este estudio prospectivo de cohortes, se seleccionaron fetos consecutivos con HDC aislada del lado izquierdo, cariotipo normal e hipoplasia pulmonar grave (definida como hernia hepática y una proporción observada/esperada de la circunferencia pulmonar-cabeza inferior al 26%) para una OTEF antes de las 32 semanas de gestación, en un único centro de medicina especializada terciaria en Querétaro (México). El resultado postnatal (supervivencia hasta los 28 días después del nacimiento) se comparó entre fetos tratados con OTEF y los casos contemporáneos con tamaño pulmonar similar, tratados como embarazo gestante. RESULTADOS: Veinticinco fetos con HDC grave aislada del lado izquierdo que habían sido tratados con OTEF fueron emparejados individualmente con 25 casos tratados como embarazo gestante. La colocación endotraqueal del globo se realizó con éxito en el primer intento en todos los casos. La mediana de la edad gestacional (EG) en el momento de la colocación del globo fue de 29,1 (rango, 25,6-31,8) semanas y 34,1 (rango, 30,0-36,1) semanas cuando se retiró el globo. En ningún caso hubo problemas técnicos con la introducción o la retirada del globo. La mediana de la EG en el momento del parto fue significativamente menor en el grupo tratado con OTEF que en el grupo tratado como gestante (35,3 vs 37,7 semanas; P=0,04). La tasa de supervivencia fue significativamente más alta en el grupo tratado con OTEF que en los casos sin intervención fetal (32% vs 0%; P<0,001). CONCLUSIÓN: En los entornos con un tratamiento neonatal subóptimo, la OTEF se asoció con una mejora de la supervivencia neonatal en los fetos con HDC aislada del lado izquierdo y con hipoplasia pulmonar grave. Copyright © 2020 ISUOG. Published by John Wiley & Sons Ltd.

Two-step regulation of trachealess ensures tight coupling of cell fate with morphogenesis in the Drosophila trachea.

During organogenesis, inductive signals cause cell differentiation and morphogenesis. However, how these phenomena are coordinated to form functional organs is poorly understood. Here, we show that cell differentiation of the Drosophila trachea is sequentially determined in two steps and that the second step is synchronous with the invagination of the epithelial sheet. The master gene trachealess is dispensable for the initiation of invagination, while it is essential for maintaining the invaginated structure, suggesting that tracheal morphogenesis and differentiation are separately induced. trachealess expression starts in bipotential tracheal/epidermal placode cells. After invagination, its expression is maintained in the invaginated cells but is extinguished in the remaining sheet cells. A trachealess cis-regulatory module that shows both tracheal enhancer activity and silencer activity in the surface epidermal sheet was identified. We propose that the coupling of trachealess expression with the invaginated structure ensures that only invaginated cells canalize robustly into the tracheal fate.

FGF10 is an essential regulator of tracheal submucosal gland morphogenesis.

Mucus secretion and mucociliary clearance are crucial processes required to maintain pulmonary homeostasis. In the trachea and nasal passages, mucus is secreted by submucosal glands (SMGs) that line the airway, with an additional contribution from goblet cells of the surface airway epithelium. The SMG mucus is rich in mucins and antimicrobial enzymes. Defective tracheal SMGs contribute to hyper-secretory respiratory diseases, such as cystic fibrosis, asthma, and chronic obstructive pulmonary disease, however little is known about the signals that regulate their morphogenesis and patterning. Here, we show that Fgf10 is essential for the normal development of murine tracheal SMGs, with gland development arresting at the early bud stage in the absence of FGF10 signalling. As Fgf10 knockout mice are lethal at birth, inducible knockdown of Fgf10 at late embryonic stages was used to follow postnatal gland formation, confirming the essential role of FGF10 in SMG development. In heterozygous Fgf10 mice the tracheal glands formed but with altered morphology and restricted distribution. The reduction in SMG branching in Fgf10 heterozygous mice was not rescued with time and resulted in a reduction in overall tracheal mucus secretion. Fgf10 is therefore a key signal in SMG development, influencing both the number of glands and extent of branching morphogenesis, and is likely, therefore, to play a role in aspects of SMG-dependent respiratory health.

QuBiT: a quantitative tool for analyzing epithelial tubes reveals unexpected patterns of organization in the Drosophila trachea.

Biological tubes are essential for animal survival, and their functions are dependent on tube shape. Analyzing the contributions of cell shape and organization to the morphogenesis of small tubes has been hampered by the limitations of existing programs in quantifying cell geometry on highly curved tubular surfaces and calculating tube-specific parameters. We therefore developed QuBiT (Quantitative Tool for Biological Tubes) and used it to analyze morphogenesis of the embryonic Drosophila trachea (airway). In the main tube, we find previously unknown anterior-to-posterior (A-P) gradients of cell apical orientation and aspect ratio, and periodicity in the organization of apical cell surfaces. Inferred cell intercalation during development dampens an A-P gradient of the number of cells per cross-section of the tube, but does not change the patterns of cell connectivity. Computationally 'unrolling' the apical surface of wild-type trachea and the hindgut reveals previously unrecognized spatial patterns of the apical marker Uninflatable and a non-redundant role for the Na+/K+ ATPase in apical marker organization. These unexpected findings demonstrate the importance of a computational tool for analyzing small diameter biological tubes.

Fetal endoscopic tracheal occlusion reduces pulmonary hypertension in severe congenital diaphragmatic hernia.

OBJECTIVE: Fetal endoscopic tracheal occlusion (FETO) is associated with increased perinatal survival and reduced need for extracorporeal membrane oxygenation (ECMO) in fetuses with severe congenital diaphragmatic hernia (CDH). This study evaluates the impact of FETO on the resolution of pulmonary hypertension (PH) in fetuses with isolated CDH. METHODS: We reviewed retrospectively the medical records of all fetuses evaluated for CDH between January 2004 and July 2017 at a single institution. Fetuses with additional major structural or chromosomal abnormalities were excluded. CDH cases were classified retrospectively into mild, moderate and severe groups based on prenatal magnetic resonance imaging indices (observed-to-expected total fetal lung volume and percentage of intrathoracic liver herniation). Presence of PH was determined based on postnatal echocardiograms. Logistic regression analyses were performed to evaluate the relationship between FETO and resolution of PH by 1 year of age while controlling for side of the CDH, use of ECMO, gestational age at diagnosis, gestational age at delivery, fetal gender, sildenafil use at discharge and CDH severity. Resolution of PH by 1 year of age was compared between a cohort of fetuses with severe CDH that underwent FETO and a cohort that did not have the procedure (non-FETO). A subanalysis was performed restricting the analysis to isolated left CDH. Parametric and non-parametric tests were used for comparisons. RESULTS: Of 257 CDH cases evaluated, 72% (n = 184) had no major structural or chromosomal anomalies of which 58% (n = 107) met the study inclusion criteria. The FETO cohort consisted of 19 CDH cases and the non-FETO cohort (n = 88) consisted of 31 (35%) mild, 32 (36%) moderate and 25 (28%) severe CDH cases. All infants with severe CDH, regardless of whether they underwent FETO, had evidence of neonatal PH. FETO (OR, 3.57; 95% CI, 1.05-12.10; P = 0.041) and ECMO (OR, 5.01; 95% CI, 2.10-11.96; P < 0.001) were independent predictors of resolution of PH by 1 year of age. A higher proportion of infants with severe CDH that underwent FETO had resolution of PH by 1 year after birth compared with infants with severe CDH in the non-FETO cohort (69% (11/16) vs 28% (7/25); P = 0.017). Similar results were observed when the analysis was restricted to cases with left-sided CDH (PH resolution in 69% (11/16) vs 28% (5/18); P = 0.032). CONCLUSION: In infants with severe CDH, FETO and ECMO are independently associated with increased resolution of PH by 1 year of age. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Anisotropic Crb accumulation, modulated by Src42A, is coupled to polarised epithelial tube growth in Drosophila.

The control of the size of internal tubular organs, such as the lungs or vascular system, is critical for proper physiological activity and to prevent disease or malformations. This control incorporates the intrinsic physical anisotropy of tubes to generate proportionate organs that match their function. The exact mechanisms underlying tube size control and how tubular anisotropy is translated at the cellular level are still not fully understood. Here we investigate these mechanisms using the Drosophila tracheal system. We show that the apical polarity protein Crumbs transiently accumulates anisotropically at longitudinal cell junctions during tube elongation. We provide evidence indicating that the accumulation of Crumbs in specific apical domains correlates with apical surface expansion, suggesting a link between the anisotropic accumulation of Crumbs at the cellular level and membrane expansion. We find that Src42A is required for the anisotropic accumulation of Crumbs, thereby identifying the first polarised cell behaviour downstream of Src42A. Our results indicate that Src42A regulates a mechanism that increases the fraction of Crb protein at longitudinal junctions, and genetic interaction experiments are consistent with Crb acting downstream of Src42A in controlling tube size. Collectively, our results suggest a model in which Src42A would sense the inherent anisotropic mechanical tension of the tube and translate it into a polarised Crumbs accumulation, which may promote a bias towards longitudinal membrane expansion, orienting cell elongation and, as a consequence, longitudinal growth at the tissue level. This work provides new insights into the key question of how organ growth is controlled and polarised and unveils the function of two conserved proteins, Crumbs and Src42A, with important roles in development and homeostasis as well as in disease, in this biological process.

The Air Sac Primordium of Drosophila: A Model for Invasive Development.

The acquisition of invasive properties preceding tumor metastasis is critical for cancer progression. This phenomenon may result from mutagenic disruption of typical cell function, but recent evidence suggests that cancer cells frequently co-opt normal developmental programs to facilitate invasion as well. The signaling cascades that have been implicated present an obstacle to identifying effective therapeutic targets because of their complex nature and modulatory capacity through crosstalk with other pathways. Substantial efforts have been made to study invasive behavior during organogenesis in several organisms, but another model found in Drosophilamelanogaster has not been thoroughly explored. The air sac primordium (ASP) appears to be a suitable candidate for investigating the genes and morphogens required for invasion due to the distinct overlap in the events that occur during its normal growth and the development of metastatic tumor cells. Among these events are the conversion of larval cells in the trachea into a population of mitotically active cells, reduced cell⁻cell contact along the leading edge of the ASP, and remodeling of the extracellular matrix (ECM) that surrounds the structure. Here, we summarize the development of ASPs and invasive behavior observed therein.

Pediatric airway surgery.

Pediatric airway surgery is a challenging field in pediatric surgery. Laryngotracheal stenosis has a variety of congenital and acquired conditions that require precise assessment and tailored treatment for each individual patient. About 90% of acquired conditions are represented by subglottic stenosis (SGS) resulting as a complication of tracheal intubation. Congenital tracheal stenosis (CTS) is a rare and life-threatening malformation, usually associated with complete tracheal rings along a variable length of the trachea. Tracheomalacia (TM) is a process characterized by flaccidity of the supporting tracheal cartilage, widening of the posterior membranous wall, and reduced anterior-posterior airway caliber. The clinical presentation can vary from almost asymptomatic patients to near fatal airway obstruction. There is considerable variation in both the morphologic subtypes and the prognosis of pediatric airway. The patients are divided into three clinical groups (mild, moderate, and severe). A further division was proposed according to the presence or absence of associated anomalies. The definitive diagnosis of pediatric airway was made by means of rigid bronchoscope and computed tomography scan with three-dimensional reconstruction (3D-CT). Rigid bronchoscopy and 3D-CT confirmed the diagnosis in all the cases. Other associated anomalies include congenital heart disease, vascular anomalies, and BPFM (maldevelopment of aerodigestive tract). After definitive diagnosis of pediatric airway lesions, surgical intervention should be considered. Surgical strategy was presented on each lesion.

Cartilage rings contribute to the proper embryonic tracheal epithelial differentiation, metabolism, and expression of inflammatory genes.

The signaling cross talk between the tracheal mesenchyme and epithelium has not been researched extensively, leaving a substantial gap of knowledge in the mechanisms dictating embryonic development of the proximal airways by the adjacent mesenchyme. Recently, we reported that embryos lacking mesenchymal expression of Sox9 did not develop tracheal cartilage rings and showed aberrant differentiation of the tracheal epithelium. Here, we propose that tracheal cartilage provides local inductive signals responsible for the proper differentiation, metabolism, and inflammatory status regulation of the tracheal epithelium. The tracheal epithelium of mesenchyme-specific Sox9Δ/Δ mutant embryos showed altered mRNA expression of various epithelial markers such as Pb1fa1, surfactant protein B (Sftpb), secretoglobulin, family 1A, member 1 (Scgb1a1), and trefoil factor 1 (Tff1). In vitro tracheal epithelial cell cultures confirmed that tracheal chondrocytes secrete factors that inhibit club cell differentiation. Whole gene expression profiling and ingenuity pathway analysis showed that the tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), and transforming growth factor-ß (TGF-ß) signaling pathways were significantly altered in the Sox9 mutant trachea. TNF-α and IFN-γ interfered with the differentiation of tracheal epithelial progenitor cells into mature epithelial cell types in vitro. Mesenchymal knockout of Tgf-ß1 in vivo resulted in altered differentiation of the tracheal epithelium. Finally, mitochondrial enzymes involved in fat and glycogen metabolism, cytochrome c oxidase subunit VIIIb (Cox8b) and cytochrome c oxidase subunit VIIa polypeptide 1 (Cox7a1), were strongly upregulated in the Sox9 mutant trachea, resulting in increases in the number and size of glycogen storage vacuoles. Our results support a role for tracheal cartilage in modulation of the differentiation and metabolism and the expression of inflammatory-related genes in the tracheal epithelium by feeding into the TNF-α, IFN-γ, and TGF-ß signaling pathways.

Failure to Burrow and Tunnel Reveals Roles for jim lovell in the Growth and Endoreplication of the Drosophila Larval Tracheae.

The Drosophila protein Jim Lovell (Lov) is a putative transcription factor of the BTB/POZ (Bric- a-Brac/Tramtrack/Broad/ Pox virus and Zinc finger) domain class that is expressed in many elements of the developing larval nervous system. It has roles in innate behaviors such as larval locomotion and adult courtship. In performing tissue-specific knockdown with the Gal4-UAS system we identified a new behavioral phenotype for lov: larvae failed to burrow into their food during their growth phase and then failed to tunnel into an agarose substratum during their wandering phase. We determined that these phenotypes originate in a previously unrecognized role for lov in the tracheae. By using tracheal-specific Gal4 lines, Lov immunolocalization and a lov enhancer trap line, we established that lov is normally expressed in the tracheae from late in embryogenesis through larval life. Using an assay that monitors food burrowing, substrate tunneling and death we showed that lov tracheal knockdown results in tracheal fluid-filling, producing hypoxia that activates the aberrant behaviors and inhibits development. We investigated the role of lov in the tracheae that initiates this sequence of events. We discovered that when lov levels are reduced, the tracheal cells are smaller, more numerous and show lower levels of endopolyploidization. Together our findings indicate that Lov is necessary for tracheal endoreplicative growth and that its loss in this tissue causes loss of tracheal integrity resulting in chronic hypoxia and abnormal burrowing and tunneling behavior.

Congenital diaphragmatic hernia-influence of fetoscopic tracheal occlusion on outcomes and predictors of survival.

UNLABELLED: The morbidity of infants with congenital diaphragmatic hernia (CDH) who had undergone foetal endoscopic tracheal occlusion (FETO) to those who had not was compared and predictors of survival regardless of antenatal intervention were identified. FETO was undertaken on the basis of the lung to head ratio or the position of the liver. A retrospective review of the records of 78 CDH infants was undertaken to determine the lung-head ratio (LHR) at referral and prior to birth, maximum oxygen saturation in the labour suite and neonatal outcomes. The 43 FETO infants were born earlier (mean 34 versus 38 weeks) (p < 0.001). They had a lower mean LHR at referral (0.65 versus 1.24) (p < 0.001) but not prior to birth and did not have a higher mortality than the 35 non-FETO infants. The FETO infants required significantly longer durations of ventilation (median: 15 versus 6 days) and supplementary oxygen (28 versus 8 days) and hospital stay (29 versus 16 days). Overall, the best predictor of survival was the OI in the first 24 h. CONCLUSION: The FETO group had increased morbidity, but not mortality. The lowest oxygenation index in the first 24 h was the best predictor of survival regardless of antenatal intervention. WHAT IS KNOWN: • Randomised controlled trials have demonstrated that foetal endotracheal occlusion (FETO) in high risk infants with congenital diaphragmatic hernia is associated with a higher survival rate. • Mortality is greater in foetuses who underwent FETO and delivered prior to 35 weeks of gestation. What is New: • Infants who had undergone FETO compared to those who had not had significantly longer durations of mechanical ventilation, supplementary oxygen and hospital stay. • Regardless of antenatal intervention, the lowest oxygenation index in the first 24 h was the best predictor of survival.

A feedback mechanism converts individual cell features into a supracellular ECM structure in Drosophila trachea.

The extracellular matrix (ECM), a structure contributed to and commonly shared by many cells in an organism, plays an active role during morphogenesis. Here, we used the Drosophila tracheal system to study the complex relationship between the ECM and epithelial cells during development. We show that there is an active feedback mechanism between the apical ECM (aECM) and the apical F-actin in tracheal cells. Furthermore, we reveal that cell-cell junctions are key players in this aECM patterning and organisation and that individual cells contribute autonomously to their aECM. Strikingly, changes in the aECM influence the levels of phosphorylated Src42A (pSrc) at cell junctions. Therefore, we propose that Src42A phosphorylation levels provide a link for the ECM environment to ensure proper cytoskeletal organisation.

Tracheobronchial Branching Abnormalities: Lobe-based Classification Scheme.

Boyden's nomenclature, which was based on postmortem specimens and published in 1955 prior to the advent of computed tomography (CT), is commonly used to describe the normal segmental bronchial anatomy and various abnormalities. However, several additional anomalies have been recognized since that time, and there is some confusion over the names used to describe these anomalies. Several congenital branching anomalies affecting the trachea, main bronchi, and intermediate bronchus have been reported, all of which can be recognized at chest CT but are often overlooked. These anomalies, which probably occur early in fetal life, can be either supernumerary, with defects occurring at 29-30 days gestation, or displaced, with defects occurring later. Tracheobronchial positional anomalies are often associated with other congenital abnormalities but may be isolated. They often are asymptomatic but can be responsible for pulmonary symptoms such as dyspnea, recurrent pneumonia, and hemoptysis. It is essential that these anomalies are recognized prior to lung resection to avoid complications, especially when video-assisted thoracoscopic surgery is performed. In addition, bronchoscopists should be aware of these anomalies before performing diagnostic or therapeutic bronchoscopic procedures. Awareness of a few key bronchial anatomic principles and use of a lobe-based classification scheme will facilitate recognition of tracheobronchial positional anomalies.

Tracheal Atresia with Segmental Esophageal Duplication: An Unusual Anatomic Arrangement.

An unusual anatomic configuration of segmental tracheal agenesis/atresia with esophageal duplication on autopsy in a fetus that demised in utero at 29 weeks is reported. The mother was scanned initially for a cardiac anomaly at 20 weeks and on follow-up scan at 27 weeks had polyhydramnios and underwent amnioreduction. The final autopsy diagnosis was vertebral, ano-rectal, cardiac, tracheoesophageal, renal, and limb malformations (VACTERL). We discuss the autopsy findings along with the embryological mechanisms and compare the configuration with Floyd's classification for tracheal agenesis. The difficulties in prenatal diagnosis are discussed.

Notochord manipulation does not impact oesophageal and tracheal formation from isolated foregut in 3D explant culture.

BACKGROUND: Tracheo-oesophageal malformations result from disturbed foregut separation during early development. The notochord, a specialised embryonic structure, forms immediately adjacent to the dividing foregut. In the Adriamycin mouse model of oesophageal atresia, foregut and notochord abnormalities co-exist, and the site and severity of foregut malformations closely correlate to the position and extent of the notochord defects. Notochord and foregut abnormalities also co-exist in the Noggin Knockout mouse as well in a small number of human cases. The notochord is a source of powerful molecular signals during early embryogenesis, being particularly important for neural crest development. The influence of notochord signaling on the adjacent foregut is not known. The purpose of this study was to examine the impact of notochord manipulation on foregut separation using a robust 3D explant method for culturing isolated foregut which permits oeosphageal and tracheal formation in vitro. METHODS: Foregut was micro-dissected from embryonic day 9 mice (License B100/4447 Irish Medicines Board), embedded in collagen and cultured for 48 h with native notochord intact (n = 6), notochord removed (n = 10) or additional notochord transplanted from stage matched controls (n = 8). Specimens were analysed for foregut morphology and molecular patterning using immunohistochemistry for Hnf3b (an endoderm marker) and Sox2 (a notochord and oesophageal marker) on cryosections. RESULTS: Foregut separation into distinct oesophagus and trachea was observed in isolated foregut specimens with or without their native notochord. In specimens with additional notochord transplants, foregut morphology and molecular patterning were comparable to controls whether or not the native notochord was maintained. In particular foregut separation was not disrupted by the transplantation of additional notochord at the dorsal foregut endoderm. CONCLUSION: The relationship between the embryonic foregut and notochord is complex and ill-defined; however, the notochord does not contribute essentially to oesophagus and trachea formation beyond E9 in the mouse, and the transplantation of additional notochord does not disrupt foregut separation in 3D explant culture.