Under pressure: a contribution to the pathogenesis of acquired ileal atresia

Expression and possible role of Smad3 in postnecrotizing enterocolitis stricture

Objective

To investigate the expression of Smad3 (mothers against decapentaplegic homolog 3) protein in postnecrotizing enterocolitis stricture and its possible mechanism of action.

Methods

We used immunohistochemistry to detect the expression characteristics of Smad3 and nuclear factor kappa B (NF-κB) proteins in human postnecrotizing enterocolitis stricture. We cultured IEC-6 (crypt epithelial cells of rat small intestine) in vitro and inhibited the expression of Smad3 using siRNA technique. Quantitative PCR, western blotting, and ELISA were used to detect the changes in transforming growth factor-β1 (TGF-β1), NF-κB, tumor necrosis factor-α (TNF-α), vascular endothelial growth factor (VEGF), and zonula occludens-1 (ZO-1) messenger RNA (mRNA) and protein expressions in IEC-6 cells. CCK8 kit and Transwell cellular migration were used to detect cell proliferation and migration. Changes in epithelial–mesenchymal transition (EMT) markers (E-cadherin and vimentin) in IEC-6 cells were detected by immunofluorescence technique.

Results

The results showed that Smad3 protein and NF-κB protein were overexpressed in narrow intestinal tissues and that Smad3 protein expression was positively correlated with NF-κB protein expression. After inhibiting the expression of Smad3 in IEC-6 cells, the mRNA expressions of NF-κB, TGF-β1, ZO-1, and VEGF decreased, whereas the mRNA expression of TNF-α did not significantly change. TGF-β1, NF-κB, and TNF-α protein expressions in IEC-6 cells decreased, whereas ZO-1 and intracellular VEGF protein expressions increased. IEC-6 cell proliferation and migration capacity decreased. There was no significant change in protein expression levels of EMT markers E-cadherin and vimentin and also extracellular VEGF protein expression.

Conclusions

We suspect that the high expression of Smad3 protein in postnecrotizing enterocolitis stricture may promote the occurrence and development of secondary intestinal stenosis. The mechanism may be related to the regulation of TGF-β1, NF-κB, TNF-α, ZO-1, and VEGF mRNA and protein expression. This may also be related to the ability of Smad3 to promote epithelial cell proliferation and migration.

Clinical features and management of post-necrotizing enterocolitis strictures in infants: A multicentre retrospective study

To explore the clinical features and management of post-necrotizing enterocolitis strictures.Clinical data from 158 patients with post-necrotizing enterocolitis strictures were summarized retrospectively in 4 academic pediatric surgical centers between April 2014 and January 2019. All patients were treated conservatively in the internal medicine department. All patients underwent preoperative X-ray examinations, 146 patients underwent gastrointestinal contrast studies, and 138 patients underwent rectal mucosal biopsies. All of the patients were treated surgically.Of the 158 patients, 40 of them had necrotizing enterocolitis (NEC) Bell stage Ib, 104 had Bell stage IIa, and 14 had Bell stage IIb. In these patients, the clinical signs of intestinal strictures occurred at mean of 47.8 days after NEC. In 158 patients, 146 underwent barium enema examination, 116 demonstrated intestinal strictures, and 10 demonstrated microcolon and poor development. A total of 138 patients underwent rectal mucosal biopsies, and 5 patients had Hirschsprung disease. Intraoperative exploration showed that intestinal post-NEC strictures occurred in the ileal (17.7%, 28/158) and colon (82.3%, 130/158), including ascending colon, transverse colon and descending colon, and multiple strictures were detected in 36.1% (57/158) patients. Surgical resection of stricture segments in the intestine and primary end-to-end anastomosis were performed in 142 patients, and the remaining 16 patients underwent staged surgeries. In the 146 patients with complete follow-up data, 9 had postoperative adhesions: 4 of them received conservative treatment, and the others underwent a second operation. Fifteen patients were hospitalized 1 to 3 times for malnutrition and dehydration due to repeated diarrhea; these patients eventually recovered and were discharged smoothly. All the other patients had uneventful recoveries without stricture recurrence.Post-NEC strictures mostly occurred in the colon, and there were some cases of multiple strictures. A gastrointestinal contrast study was the preferred method of examination. Preoperative rectal mucosal biopsy resulted in a diagnosis of Hirschsprung disease, and then a reasonable treatment protocol was chosen. Surgical resection of stricture segments in the intestine and primary end-to-end anastomosis achieved good therapeutic effects with favorable prognoses in these patients.