Genetic and cellular mechanisms of the formation of esophageal atresia and tracheoesophageal fistula

Morphologic changes in the cytoskeleton and adhesion apparatus during the conversion from pseudostratified single columnar to stratified squamous epithelium in the developing mouse esophagus

The apico-basal (AB) polarity of epithelial cells is maintained by organized arrays of the cytoskeleton and adhesion apparatus. We previously reported that mouse embryonic esophageal epithelium exhibits interkinetic nuclear migration (INM), an AB-polarity-based regulatory mechanism of stem-cell proliferation, and suggested that the pseudostratified single columnar epithelium, a hallmark of INM, is converted to stratified squamous epithelium via rearrangement of the cytoskeleton and cell-adhesion apparatus. Here, we chronologically examined morphological changes in the cytoskeleton and adhesion apparatus in the mouse esophageal epithelium at embryonic day (E) 11.5, E13.5, E14.5, and E15.5, during which epithelial conversion has been suggested to occur. We used phalloidin to examine the apical terminal web (ATW), immunofluorescent anti-zonula occludens protein (ZO-1) antibody to reveal ZO-1, and anti-gamma tubulin antibody to detect primary cilia (PC). At E11.5, a thick ATW, apically oriented ZO-1 and apical PC were observed, indicating a pseudostratified single columnar structure. At E13.5 and E14.5, the phalloidin-staining, ZO-1, and PC distribution patterns were not apically localized, and the epithelial cells appeared to have lost the AB polarity, suggesting conversion of the epithelial structure and cessation of INM. At E15.5, light and transmission electron microscope observations revealed the ATW, ZO-1, PC, and tight junction which were localized into two-1ayers: the apical and subapical layers of the epithelium. These findings suggest that dynamic remodeling of the cytoskeleton and adhesion apparatus is involved in the conversion from pseudostratified single columnar to stratified squamous morphology and is closely related with temporal perturbation of the AB-polarity and cessation of INM.

Characterization of mesenchymal stem cells in patients with esophageal atresia

BACKGROUND

Preclinical studies demonstrate that tissue engineering and patient-derived stem cells can regenerate tissue. The goal of this study was to determine whether stem cells from esophageal atresia patients (EA) could be utilized for this purpose.

METHODS

Adipose tissue was obtained from control, esophageal atresia (EA) and long gap esophageal atresia (LGEA) patients. Mesenchymal stem cells (MSCs) were isolated, expanded, characterized and seeded onto tubular scaffolds for 6 days. Scaffolds were characterized for viability, gene expression and cytokine production.

RESULTS

The average weight of tissue from the EA and LGEA patients was 145.8mg compared to 2981 mg in controls. Despite the small amount of tissue obtained from neonatal patients, cells were expanded to cover a scaffold. After incubating 6 days on the scaffold, cells were viable and proliferating with differences in gene expression between groups. VEGFA production in the supernatant was increased in EA and LGEA patients; while IL6 production was significantly increased in the control patients.

CONCLUSIONS

This study demonstrates the ability to utilize small amounts of adipose tissue from esophageal atresia patients as a cell source for regenerative medicine. Future studies will focus on use of these cells for tissue regeneration in vivo.

Histological, immunohistochemical and transcriptomic characterization of human tracheoesophageal fistulas

Esophageal atresia (EA) and tracheoesophageal fistula (TEF) are relatively frequently occurring foregut malformations. EA/TEF is thought to have a strong genetic component. Not much is known regarding the biological processes disturbed or which cell type is affected in patients. This hampers the detection of the responsible culprits (genetic or environmental) for the origin of these congenital anatomical malformations. Therefore, we examined gene expression patterns in the TEF and compared them to the patterns in esophageal, tracheal and lung control samples. We studied tissue organization and key proteins using immunohistochemistry. There were clear differences between TEF and control samples. Based on the number of differentially expressed genes as well as histological characteristics, TEFs were most similar to normal esophagus. The BMP-signaling pathway, actin cytoskeleton and extracellular matrix pathways are downregulated in TEF. Genes involved in smooth muscle contraction are overexpressed in TEF compared to esophagus as well as trachea. These enriched pathways indicate myofibroblast activated fibrosis. TEF represents a specific tissue type with large contributions of intestinal smooth muscle cells and neurons. All major cell types present in esophagus are present-albeit often structurally disorganized-in TEF, indicating that its etiology should not be sought in cell fate specification.

Development pattern of tracheal cartilage in human embryos

INTRODUCTION

Congenital tracheal anomalies are associated with high morbidity and mortality. The etiology of congenital tracheal anomalies is not well understood, but often attributed to malformed tracheal cartilage. The development of tracheal cartilage has not been described in detail. In this study, we aimed to investigate the development pattern and timing of normal tracheal cartilage to better understand the etiology of tracheal anomalies.

MATERIALS AND METHODS

The development of tracheal cartilage was examined by studying the trachea in histological sections of 14 healthy human embryos from the Carnegie collection. Two specimens for Carnegie Stages 17-23 (42-60 days of embryological development) were studied.

RESULTS

At Carnegie Stages 17-19 (42-51 days), a continuous mesenchymal condensation was observed ventral to the tracheal lumen. At Stages 20 and 21 (51-54 days), this pre-tracheal mesenchyme showed sites of increased condensation indicative of future tracheal rings. Furthermore, growth centers were identified both proximally and distally in the trachea. Characteristic horseshoe shaped tracheal rings were apparent at Carnegie Stages 22 and 23 (54-60 days).

CONCLUSIONS

In human embryos, tracheal rings arise from growth centers in the ventral mesenchyme at approximately 51-54 days of embryological development. The observation of proximal and distal growth centers suggests a centripetal growth gradient, potentially contributing to occurrence of complete tracheal ring deformity (CTRD). Although this study shows new insights on tracheal cartilage development, the exact origin of congenital tracheal defects has yet to be elucidated.

Infantile hypertrophic pyloric stenosis in patients with esophageal atresia

BACKGROUND

Patients born with esophageal atresia (EA) have a higher incidence of infantile hypertrophic pyloric stenosis (IHPS), suggestive of a relationship. A shared etiology makes sense from a developmental perspective as both affected structures are foregut derived. A genetic component has been described for both conditions as single entities and EA and IHPS are variable components in several monogenetic syndromes. We hypothesized that defects disturbing foregut morphogenesis are responsible for this combination of malformations.

METHODS

We investigated the genetic variation of 15 patients with both EA and IHPS with unaffected parents using exome sequencing and SNP array-based genotyping, and compared the results to mouse transcriptome data of the developing foregut.

RESULTS

We did not identify putatively deleterious de novo mutations or recessive variants. However, we detected rare inherited variants in EA or IHPS disease genes or in genes important in foregut morphogenesis, expressed at the proper developmental time-points. Two pathways were significantly enriched (p < 1 × 10^-5 ): proliferation and differentiation of smooth muscle cells and self-renewal of satellite cells.

CONCLUSIONS

None of our findings could fully explain the combination of abnormalities on its own, which makes complex inheritance the most plausible genetic explanation, most likely in combination with mechanical and/or environmental factors. As we did not find one defining monogenetic cause for the EA/IHPS phenotype, the impact of the corrective surgery could should be further investigated.

E3 ubiquitin ligase MDM2 acts through p53 to control respiratory progenitor cell number and lung size

The respiratory lineage initiates from the specification of NKX2-1⁺ progenitor cells that ultimately give rise to a vast gas-exchange surface area. How the size of the progenitor pool is determined and whether this directly impacts final lung size remains poorly understood. Here, we show that epithelium-specific inactivation of Mdm2, which encodes an E3 ubiquitin ligase, led to lethality at birth with a striking reduction of lung size to a single vestigial lobe. Intriguingly, this lobe was patterned and contained all the appropriate epithelial cell types. The reduction of size can be traced to the progenitor stage, when p53, a principal MDM2 protein degradation target, was transiently upregulated. This was followed by a brief increase of apoptosis. Inactivation of the p53 gene in the Mdm2 mutant background effectively reversed the lung size phenotype, allowing survival at birth. Together, these findings demonstrate that p53 protein turnover by MDM2 is essential for the survival of respiratory progenitors. Unlike in the liver, in which genetic reduction of progenitors triggered compensation, in the lung, respiratory progenitor number is a key determinant factor for final lung size.

Maternal phenylketonuria in Turkey: outcomes of 71 pregnancies and issues in management

Untreated phenylketonuria (PKU) in pregnancy causes a severe embryopathy called maternal PKU syndrome. Here, we aimed to assess management issues and pregnancy outcomes in the first published series of PKU pregnancies from the developing world. Data were collected retrospectively in a single center from 71 pregnancies and 45 live births of 32 women with PKU, 11 of whom were diagnosed in adulthood after having an affected child. Microcephaly, intellectual disability, and dysmorphic facies were more prevalent in offspring of untreated than treated pregnancies with classical PKU (100% vs. 0%, 91% vs. 0%, and 73% vs. 23% with p < 0.001, p < 0.001, and p = 0.037, respectively). In treated pregnancies, phenylalanine levels were higher during weeks 6-14 than other periods of gestation (4.38 vs. 3.93, 2.00 and 2.28 mg/dl; p < 0.05). Poor compliance correlated with higher phenylalanine levels (ρ = - 0.64, p = 0.019) and fluctuations (ρ = - 0.66, p = 0.014).Conclusion: More frequent phenylalanine measurements during late first trimester are crucial to improve outcomes in treated pregnancies. In order to prevent untreated pregnancies via detecting undiagnosed adults, countries where significantly many women of childbearing age were not screened as newborns may consider pre-pregnancy PKU screening. Microcephaly in the newborn should prompt screening for PKU in the mother. What Is Known •Untreated phenylketonuria during pregnancy causes maternal phenylketonuria syndrome in the newborn. •Effective treatment throughout pregnancy can prevent adverse fetal outcomes. What Is New: •Metabolic control is related to frequency of follow-up and worsens during late first trimester. Closer follow-up during this period may improve metabolic control. •In order to prevent untreated pregnancies, pre-pregnancy phenylketonuria screening may be considered if many women of childbearing age were not screened as newborns.

Maternal hyperthyroidism increases the prevalence of foregut atresias in fetal rats exposed to adriamycin

PURPOSE

Gastrointestinal malformations such as esophageal atresia with tracheoesophageal fistula (EA/TEF) and duodenal atresia (DA) have been reported in infants born to hyperthyroid mothers or with congenital hypothyroidism. The present study aimed to test whether maternal thyroid status during embryonic foregut division has any influence on the prevalence of EA/TEF and DA in an accepted rat model of these malformations.

METHODS

Pregnant rats received either vehicle or 1.75 mg/kg i.p. adriamycin on gestational days 7, 8 and 9. Transient maternal hyper or hypothyroidism was induced by oral administration of levothyroxine (LT4, 50 μg/kg/day) or propylthiouracil (PTU, 2 mg/kg/day), respectively, on days 7 to 12 of gestation. Plasma cholesterol, total T3, free T4 and TSH were measured at gestational days 7, 12, and 21. At the end of gestation, the mothers were sacrificed and embryo-fetal mortality was recorded. Fetuses were dissected to determine the prevalence of esophageal and intestinal atresias.

RESULTS

At gestational day 12, mothers treated with LT4 or PTU had hyper or hypothyroid status, respectively; plasma cholesterol levels were similar. In the adriamycin-exposed fetuses from hyperthyroid mothers, the embryonal resorption rate and the prevalence of both EA/TEF and DA were significantly higher than in the other groups; maternal hypothyroidism during the same period did not have significant effect on the prevalence of atresias.

CONCLUSIONS

Maternal hyperthyroidism during the embryonic window corresponding to foregut cleavage increased the prevalence of both EA/TEF and duodenal atresia in fetal rats exposed to adriamycin. This suggests that maternal thyroid hormone status might be involved in the pathogenesis of foregut atresias and invites further research on this likely clinically relevant issue in humans.