Intrauterine villus hypertrophy with jejunoileal atresia

Does small intestinal atresia affect epithelial protein expression in human newborns?

OBJECTIVES

Bowel segments distal to a congenital intestinal obstruction have been suggested to be immature. In other words, luminal components such as amniotic fluid (before birth) and/or enteral nutrition (after birth) may be required to activate intestinal epithelial protein expression, thereby influencing epithelial differentiation. We investigated cell-type-specific protein expression proximal and distal to jejunal and ileal atresias in human newborns.

PATIENTS AND METHODS

We immunohistochemically studied intestinal tissue specimens of 16 newborns who had undergone surgery for jejunal or ileal atresia. Sections were taken from both the proximal and distal sides of the atresias.

RESULTS

For all patients, the enterocyte-specific markers lactase, sucrase-isomaltase, sodium glucose cotransporter 1, glucose transporters 2 and 5, intestinal fatty acid-binding protein and alkaline phosphatase were expressed at a mean 3 +/- 1 days after birth, both proximal and distal to jejunal and ileal atresias. Expression of goblet cell-specific markers mucin 2 and trefoil factor 3 and that of the Paneth cell marker lysozyme was maintained at either side of the atretic segment.

CONCLUSIONS

With respect to the markers used, the human small intestinal epithelium is already differentiated shortly after birth. The absence of intestinal continuity in case of a jejunal or ileal atresia does not affect epithelial protein expression. This would seem to indicate that the developing small intestinal epithelium matures independently of luminal components.

Restriction of nutrition in utero selectively inhibits gastrointestinal growth in fetal sheep

This study examined the effects of reduced nutrition on fetal growth over the first half of gestation. Reduced nutrition was achieved by a combination of reduced maternal food intake and carunclectomy, a procedure which restricts the development of the placenta. There were no major effects of restriction on fetal body, tissue or organ growth, except for the gastrointestinal tract (GIT). Total GIT weight was lower in restricted fetuses than in controls. More specifically, it was growth of the small and large intestine which was compromised. Small intestinal weight was significantly lower, both in absolute terms and relative to body weight. The intestinal diameter and mucosal area were significantly lower in both small and large intestine of restricted fetuses. Maturation of enterocytes was also delayed in nutrient-restricted fetuses. In addition, there were focal lesions of the brush border present, indicating abnormal epithelial differentiation. By term, in growth-retarded fetuses, growth deficits in many organs were present, including the GIT. The present study suggests that GIT growth deficits may have a long-term etiology, including at their onset, abnormal cellular differentiation. These results could explain why GIT function in intrauterine growth-retarded infants is more likely to be compromised than in premature or term infants.

Altered intestinal development after jejunal ligation in fetal sheep

Experimental obstruction of the fetal small intestine resulted in massive hypertrophy of the segment proximal to the site of obstruction. Villus morphology was grossly abnormal. Enterocytes developed many irregular features, most notably cytoplasmic extensions (pseudopods, or blebs) from their apical surface. Distal to the site of obstruction, morphological anomalies which resembled those seen after experimental oesophageal ligation were found. These included delayed disappearance of the apical endocytic network, disrupted or absent microvilli, glycogen accumulation and inappropriate cell extrusion. Proximal to the obstruction, where stasis of swallowed fluid occurs, distension and abnormal intestinal development ensues. Distal to the obstruction where the intestine develops in the absence of swallowed fluid, development is also abnormal. The anomalies resemble those noted after oesophageal ligation in utero, and possibly are the results of reduced cellular nutrition. These results suggest that fetal ingestion provides the developing gastrointestinal tract with an important stimulus for normal growth.

Mucosal morphology in experimental intestinal atresia: studies in the chick embryo

Lesions identical to those observed in human intestinal atresia (IA) have been experimentally reproduced in several mammal models by either mesenteric vessels or intestinal wall injury. The recent availability of an avian model led us to investigate whether the same lesions could be studied at less expense. An intestinal loop within the body stalk hernia was coagulated on the 12th incubation day in 427 chick embryos (group 3), the lesions were studied in survivors 4 days later under light and scanning electronmicroscopy (EM), and the findings were compared with those in 12 control embryos (group 1) and 14 sham-operated ones (group 2). Types I or II atresias were obtained in 61 (73.4%) of the 83 survivors in group 3. Seromuscular layers were normal at both ends of the lesion; there was some flattening of villi at the proximal, dilated end, and hyperplasia with apparently lengthened, branched villi at the distal, unused one. Mucosal pattern under light microscopy was strikingly close to that observed in human IA and in the fetal lamb experimental model. On the other hand, scanning EM showed that in this model there were no villi as such, but rather prominent mucosal folds that were regularly arranged in a tire-rubber pattern in the normal intestine, flattened and distended in the dilated one, and again roughly normal in the distal unused gut. High-power magnification scanning EM showed that enterocytes were normal at all levels but, in agreement with previous findings in the fetal lamb model, that intercellular spaces were widened in the dilated portion adjacent to the obstruction.(ABSTRACT TRUNCATED AT 250 WORDS)

Antenatal intestinal adaptation with experimental jejunoileal atresia

Jejunoileal atresia without significant shortening of total intestinal length, was created in five date-bred Dorset ewes by devascularizing a 15 cm segment of fetal intestine at 90-100 days gestation. Light microscopy showed mucosal hypertrophy distal to the atresia with almost total obliteration of the lumen by tail, feathery-shaped villi similar to those observed in newborns with jejunal atresia. Scanning electron microscopic views of the proximal mucosa showed the villi to be thicker, more segmented and tended to congregate compared to normal villi and those distal to the atresia. No evidence of microvillus, intracellular or capillary membrane change or injury could be identified to explain the functional secretory state.