Age-specific nasal epithelial responses to SARS-CoV-2 infection

Children infected with SARS-CoV-2 rarely progress to respiratory failure. However, the risk of mortality in infected people over 85 years of age remains high. Here we investigate differences in the cellular landscape and function of paediatric (<12 years), adult (30-50 years) and older adult (>70 years) ex vivo cultured nasal epithelial cells in response to infection with SARS-CoV-2. We show that cell tropism of SARS-CoV-2, and expression of ACE2 and TMPRSS2 in nasal epithelial cell subtypes, differ between age groups. While ciliated cells are viral replication centres across all age groups, a distinct goblet inflammatory subtype emerges in infected paediatric cultures and shows high expression of interferon-stimulated genes and incomplete viral replication. In contrast, older adult cultures infected with SARS-CoV-2 show a proportional increase in basaloid-like cells, which facilitate viral spread and are associated with altered epithelial repair pathways. We confirm age-specific induction of these cell types by integrating data from in vivo COVID-19 studies and validate that our in vitro model recapitulates early epithelial responses to SARS-CoV-2 infection.

Long-term functional outcomes and multidisciplinary management after ileorectal Duhamel pull-through for total colonic aganglionosis- 20-year experience in a tertiary surgical center

Introduction Management of patients with total colonic aganglionosis (TCA) is challenging for paediatric surgeons. The purpose of this study was to review our institution's 20-year experience regarding long-term outcomes and multidisciplinary team management of these patients after an Ileorectal Duhamel pull-through procedure. Materials and Methods Retrospective review was conducted for all patients diagnosed with TCA in our tertiary institution. Data was collected on demographics, clinical presentation, complications, need for additional surgery and long-term effects on bowel function. Results Of a total of 202 patients with Hirschsprung's disease (HSCR), 13 were diagnosed with TCA (6.4 %). Clinical presentation was variable. 11 presented in neonatal period with distal bowel obstruction and 2 presented with constipation in early infancy. Ileorectal Duhamel pull-through was performed in all patients. Median follow up was 13 years. 11 are toilet trained, of whom 5 are fully continent. 6 continue to have problems with bowel continence or constipation. 1 developed recurrent episode of Hirschsprung's associated enterocolitis (HAEC). 2 patients had stoma re-established. Patients experiencing difficulties in bowel function are jointly managed by a multidisciplinary team consisting of surgeons, gastroenterologists, paediatric psychologists, and clinical nurse specialists. Conclusions TCA can be associated with significant long-term morbidity. Nearly half of the patients in this series have ongoing problems with bowel continence requiring a permanent stoma in some. Diligent follow-up coupled with inputs of a multidisciplinary team has greatly helped manage these complex patients in our institution.

Engineered Tissue-Stent Biocomposites as Tracheal Replacements

Here we report the creation of a novel tracheal construct in the form of an engineered, acellular tissue-stent biocomposite trachea (TSBT). Allogeneic or xenogeneic smooth muscle cells are cultured on polyglycolic acid polymer-metal stent scaffold leading to the formation of a tissue comprising cells, their deposited collagenous matrix, and the stent material. Thorough decellularization then produces a final acellular tubular construct. Engineered TSBTs were tested as end-to-end tracheal replacements in 11 rats and 3 nonhuman primates. Over a period of 8 weeks, no instances of airway perforation, infection, stent migration, or erosion were observed. Histological analyses reveal that the patent implants remodel adaptively with native host cells, including formation of connective tissue in the tracheal wall and formation of a confluent, columnar epithelium in the graft lumen, although some instances of airway stenosis were observed. Overall, TSBTs resisted collapse and compression that often limit the function of other decellularized tracheal replacements, and additionally do not require any cells from the intended recipient. Such engineered TSBTs represent a model for future efforts in tracheal regeneration.

Esophageal atresia and malrotation: what association?

INTRODUCTION

Esophageal atresia/tracheo-esophageal fistula (EA/TEF) has an incidence of approximately 1:3,500. The incidence of malrotation is thought to be 1:200-500. We attempted to define the incidence of a combination and discuss the implications.

METHODS

This was a retrospective review of all patients admitted to a single institution with a diagnosis of EA or EA/TEF or TEF between April 1981 and January 2013. Patients were included if the position of the duodeno-jejunal flexure (DJF) was determined by upper GI contrast study (UGIS), surgery or post-mortem.

RESULTS

Case notes were reviewed for 235 patients. In the EA type A group, 3/28 (11 %; 95 % CI 3.7-27.2 %) had malrotation, significantly higher than the reported incidence of malrotation in the general population (p = 0.0008). All three patients in this group were symptomatic with one patient found to have a volvulus at emergency surgery. In the type C group, 6/196 (3 %, 95 % CI 1.4-6.5 %) had malrotation, significantly higher than the incidence reported for the general population (p = 0.0033) but not significantly different to that of the type A group (p = 0.0878). There were no patients with malrotation identified in any other EA/TEF type. In total, 9/235 (3.8 %; 95 % CI 2.0-7.2 %) patients with EA had malrotation, significantly higher than the 5/1,050 (0.48 %) reported for the general population (p = 0.0002).

CONCLUSION

There is a high incidence of malrotation in patients with pure EA. In the type A group an attempt to identify the DJF position at gastrostomy siting and/or performance of UGIS in the neonatal period should be undertaken. There should also be a low threshold for UGIS in all EA/TEF patients.

Novel exomphalos genetic mouse model: the importance of accurate phenotypic classification

BACKGROUND

Rodent models of abdominal wall defects (AWD) may provide insight into the pathophysiology of these conditions including gut dysfunction in gastroschisis, or pulmonary hypoplasia in exomphalos. Previously, a Scribble mutant mouse model (circletail) was reported to exhibit gastroschisis. We further characterise this AWD in Scribble knockout mice.

METHOD

Homozygous Scrib knockout mice were obtained from heterozygote matings. Fetuses were collected at E17.5-18.5 with intact amniotic membranes. Three mutants and two control fetuses were imaged by in amnio micro-MRI. Remaining fetuses were dissected, photographed and gut length/weight measured. Ileal specimens were stained for interstitial cells of Cajal (ICC), imaged using confocal microscopy and ICC quantified.

RESULTS

127 fetuses were collected, 15 (12%) exhibited AWD. Microdissection revealed 3 mutants had characteristic exomphalos phenotype with membrane-covered gut/liver herniation into the umbilical cord. A further 12 exhibited extensive AWD, with eviscerated abdominal organs and thin covering membrane (intact or ruptured). Micro-MRI confirmed these phenotypes. Gut was shorter and heavier in AWD group compared to controls but morphology/number of ICC was not different.

DISCUSSION

The Scribble knockout fetus exhibits exomphalos (intact and ruptured), in contrast to the original published phenotype of gastroschisis. Detailed dissection of fetuses is essential ensuring accurate phenotyping and result reporting.