Stephen L. Gans Distinguished Overseas Lecture. The neural crest in pediatric surgery

Retinoic acid receptor beta variant-related colonic hypoganglionosis

Retinoic acid receptor beta (RARB) variants are heavily linked to pathologies of neural crest cell migration. The purpose of this report is to present a 23-month-old male with the previously described R387C RARB gain-of-function variant whose gastrointestinal issues and long-term constipation lead to the discovery of colonic hypoganglionosis. This case further delineates the pattern of malformation associated with RARB variants. The findings are also consistent with the known etiology of aganglionic colon due to failed neural crest cell migration.

Abnormal Sonic hedgehog signaling in the lung of rats with esophageal atresia induced by adriamycin

BACKGROUND

Abnormal lung development was recently described in the rat model of esophageal atresia and tracheoesophageal fistula (EA-TEF). Since in this condition the ventral-to-dorsal switch of Shh expression in the foregut is disturbed, the present study tested the hypothesis that this abnormal expression at the emergence of the tracheobronchial bud might be translated into the developing lung.

METHODS

Pregnant rats received either 1.75 mg/kg i.p. adriamycin or vehicle from E7 to E9. Three groups were studied: control and adriamycin-exposed with and without EA-TEF. Embryos were recovered and the lungs were harvested and processed for reverse transcription polymerase chain reaction and immunofluorescence analysis of the Shh signaling cascade.

RESULTS

Shh signaling was downregulated at the late embryonic stage of lung development (E13) in embryos with EA-TEF. Throughout the subsequent stages of development, the expression of both Shh and its downstream components increased significantly and remained upregulated throughout gestation. Immunofluorescent localization was consistent with these findings.

CONCLUSION

Defective Shh signaling environment in the foregut is present beyond the emergence of lung buds and probably impairs lung development. Later in gestation, lungs exhibited a remarkable ability to upregulate the Shh cascade, suggesting a compensatory response. These findings may be relevant to understand pulmonary disease suffered by children with EA-TEF.

Lung hypoplasia in rats with esophageal atresia and tracheo-esophageal fistula

INTRODUCTION

Survivors of esophageal atresia and tracheo-esophageal fistula (EA-TEF) often suffer chronic respiratory tract disease. EA-TEF results from abnormal emergence of the trachea from the foregut. This study in a rat model tests the hypothesis that primary lung maldevelopment might be a downstream consequence of this defect.

RESULTS

The lung was hypoplastic in rats with EA-TEF although the histological pattern was normal. Maturation and arteriolar wall thickness were unchanged, but mesenchymal control of airway branching was weakened. This branching was deficient from embryonal day (E13) on in adriamycin-treated explants.

DISCUSSION

In conclusion, the lungs were hypoplastic in rats with experimental EA-TEF due to defective embryonal airway branching. However, arteriolar wall and respiratory epithelial patterns remained normal. These findings suggest that similarly defective lung development might contribute to chronic respiratory disease in EA-TEF patients.

METHODS

Pregnant rats received either 1.75 mg/kg i.p. adriamycin or vehicle on E7, E8, and E9. Lungs were recovered at E15, E18, and E2. Lung weight/body weight ratio, total DNA and protein, radial alveolar count, arteriolar wall thickness, lung maturity, and mesenchymal control of airway branching were assessed. E13 lungs were cultured for 72 h and explant airway branching was measured daily. For comparisons, nonparametric tests (*P < 0.05) were used.

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.

Microscopic magnetic resonance imaging of the thoracic venous system in rats with congenital diaphragmatic hernia

BACKGROUND/AIM

Infants and rats with congenital diaphragmatic hernia (CDH) have malformations of the heart and the great arteries caused by neural crest (NC) dysregulation during embryogenesis. Abnormally narrow jugular veins have been found in babies during cannulation for ECMO. However, the venous system has not been examined in depth so far. We hypothesized that abnormal patterning and/or size of the thoracic veins could occur in rats with CDH. This hypothesis was tested by microscopic magnetic resonance imaging (MMRI), a high-resolution tool able to detect subtle changes of vessels in small animals.

MATERIAL/METHODS

Fetuses from pregnant rats fed either 100 mg i.g. nitrofen or vehicle on E9.5 were recovered near term. A 7 T MMRI system with a coronal multislice fast spin echo sequence allowed diagnosis of CDH (n = 19), and T2 SE high-resolution sequences made assessment of the pattern and width of cervico-thoracic veins possible. Values were corrected for body size by dividing them by the length of thoracic vertebrae T3-T5. The results in nitrofen and control (n = 11) groups were compared by non-parametric tests (*p < 0.05).

RESULTS

Congenital diaphragmatic hernia fetuses were smaller than controls (4.5 ± 0.26 vs. 5.3 ± 0.2 g*). The widths (corrected for body size) of left external, both innominate, right superior vena cava and azygos veins were significantly smaller in CDH rats than in controls.

CONCLUSIONS

The cervico-thoracic veins are normally patterned but abnormally narrow (except the internal jugulars) in rats with CDH. The same embryonic NC dysregulation that accounts for cardiovascular malformations could also explain these venous anomalies in CDH.

Microscopic magnetic resonance in congenital diaphragmatic hernia and associated malformations in rats

BACKGROUND/AIM

The research on congenital diaphragmatic hernia (CDH) is often carried out on the nitrofen fetal rat model in which most investigations involve microdissections and fastidious assessment of serial sections of different anatomic areas. Current microscopic magnetic resonance (MMR) equipment allows detailed anatomic studies of alive, fresh or fixed fetuses. The purpose of the present study was to demonstrate that CDH itself and most of the associated malformations are adequately imaged and measured by MMR.

MATERIALS AND METHODS

Fetuses from pregnant rats treated with either i.g. vehicle (control, n = 10) or 100 mg nitrofen (only those with CDH, n = 18) on E9.5 were recovered on E21 (term = E22) and total body was scanned by MMR under sedation in a 7 T MRI system (Bruker Medical, Ettlingen, Germany). CDH was detected with a coronal multislice fast spin echo sequence with a long repetition time and short effective echo time. Oblique MPR and 3D reconstructions were used. All studies were processed with attention to the hernia and its contents and the structure of the tracheobronchial tree and the lung, the heart and great vessels, the thymus and cervico-thoracic vertebrae. The findings in both groups were compared.

RESULTS

Congenital diaphragmatic hernia, lung hypoplasia and parenchymal features were clearly depicted. Tracheal ring anomalies were also demonstrated. The thymus was significantly smaller in CDH pups (2.9 x 1 x 2.4 mm) than in controls (4 x 1.3 x 2.8 mm) (p < 0.01). MRI was particularly performant for imaging cardiovascular anomalies: 4 double aortic arches, 3 Fallots, 3 right aortic arches, 3 ventricular septal defects and 1 aberrant subclavian artery.

CONCLUSIONS

Microscopic magnetic resonance involves refined and expensive equipment but it provides a powerful research tool for the study of CDH and other malformations in rat fetuses. Further work on this area is warranted.

Sonic hedgehog gene expression in nitrofen induced hypoplastic lungs in mice

BACKGROUND

The pathogenesis of congenital diaphragmatic hernia (CDH) is unknown. The sonic hedgehog (Shh) cascade is crucial for the patterning of the early respiratory system in mice. Optical Projection Tomography (OPT) is a new tool for 3D imaging small biological specimens that enables us to visualise both the anatomy of developing organs and gene expression localised in the context of normal or abnormal anatomy. We visualised Shh gene expression patterns in the nitrofen treated and control mouse lung buds at early stages of lung development.

MATERIALS AND METHODS

Time-mated CD1 female mice (n = 5) received oral administration of 100 mg of the herbicide 2,4-dichlorophenyl-p-nitrophenylether (nitrofen) (WAKO Chemical, Osaka, Japan) in 1 ml of olive oil or olive oil alone at 7 days of gestation. Embryos were harvested on gestation days 9-12, and stained following whole mount in situ hybridisation with labelled RNA probes to detect Shh transcripts at each stage. Embryos were scanned by OPT to obtain 3D representations of gene expression domains in the context of the changing morphology of the embryo.

RESULTS

OPT analysis of Shh transcript distribution clearly revealed gene expression in both groups. In treated embryos, there were no significant changes in Shh transcript distribution in lung buds in comparison with control embryos.

CONCLUSION

Although altered Shh expression in the hypoplastic lung has been reported in late gestation, the present study did not reveal any significant alterations in pulmonary Shh spatial transcript distribution or gene expression level during the early gestation in nitrofen CDH model. It would be of great interest in future studies to use OPT approach to investigate pulmonary expression of Shh and other regulatory genes both during early and late stages of lung development in order to provide new insights into the pathogenesis of pulmonary hypoplasia.

Abnormal intrinsic esophageal innervation in congenital diaphragmatic hernia: a likely cause of motor dysfunction

PURPOSE

Patients with congenital diaphragmatic hernia (CDH) often have dilated esophagus and gastroesophageal reflux. Sparse intrinsic esophageal innervation has been described in rats with CDH, but this issue has not been investigated in patients with CDH. The present study tests the hypothesis that innervatory anomalies could account for motor dysfunction in human CDH.

METHODS

The esophagi of CDH (n = 6) and control babies dead of other causes (n = 6) were included in paraffin, transversally sectioned, and immunostained with antineurofilament and anti-S-100 antibodies. The proportion of the section surface occupied by neural structures, the ganglionar surface, and the number of neurons per ganglion were measured in 2 to 5 low-power fields from the proximal and distal esophagus with the assistance of image analysis software. Mann-Whitney tests were used for comparing the results using a threshold of significance of P < .05.

RESULTS

The percentage of neural/muscle surface was similar in the upper esophagus in both groups, but it was significantly decreased in the lower esophagus of patients with CDH in comparison with controls. There was a relative scarcity of neural tissue in the intermuscular plexus of the lower esophagus. On the other hand, the ganglionar surface and the number of neurons per ganglion were identical in both groups. These results were similar with both immunostainings.

CONCLUSION

Intrinsic innervation of the lower esophagus in CDH is abnormal in terms of decreased density of neural structures in the intermuscular plexus. These neural crest-derived anomalies could explain in part the esophageal dysfunction in survivors of CDH.

Esophageal atresia and tracheo-esophageal fistula associated with coarctation of the aorta, CHARGE association, and DiGeorge syndrome: a case report and literature review

CHARGE association and DiGeorge syndrome (DGS) rarely occur together and only eight cases have been reported in the English literature. Two were associated with esophageal atresia (EA) and severe congenital heart anomalies. We report a third case of EA with tracheoesophageal fistula (EA-TEF) associated with coarctation of the aorta (CoA), CHARGE association, and DGS. The challenge for management in this complicated case is the background DGS which influences surgical outcome because of Ca++ imbalance and immune deficiency that can be life-threatening and require bone marrow transplantation.

Management of congenital diaphragmatic hernia

PURPOSE OF REVIEW

To evaluate the impact of recent research on the management of congenital diaphragmatic hernia in the light of new theories on embryological development, earlier antenatal diagnosis, fetal and postnatal interventions together with advances in perinatal intensive care.

RECENT FINDINGS

The year 2007 provided in excess of 200 publications that address various aspects of congenital diaphragmatic hernia. The genetic basis and the causes of pulmonary hypoplasia at the molecular level are slowly being unravelled. Fetal MRI of lung volume, lung-head ratio, liver position and size of diaphragmatic defect have all been evaluated as early predictors of outcome and with a view to prenatal counselling. The impact of fetal interventions such as fetal endoluminal tracheal occlusion, the mode of delivery, the surgical techniques and agents for treating pulmonary hypertension were evaluated. The influence of associated anomalies and therapeutic interventions on the outcome and quality of life of survivors continue to be appraised.

SUMMARY

Deferred surgery after stabilization with gentle ventilation and reversal of pulmonary hypertension remain the cornerstones of management. Optimal presurgery and postsurgery ventilatory settings remain unproven. Continued improvement in neonatal intensive care raises the bar against which any intervention such as fetal endoluminal tracheal occlusion and extracorporeal membrane oxygenation will be judged.