Early ultrastructural adaptive changes of ileal enterocytes after proximal small bowel resection as determined morphometrically

Abstract

The aim of the present study was to evaluate in terms of quantitative measurements whether the well-known histomorphological and functional adaptive changes in the intestinal mucosa after small bowel resection are accompanied by alterations on the ultrastructural level. Therefore, samples of the ileal remnants after a 60% proximal resection were processed for ultrastructural evaluation and analyzed employing point counting planimetry and direct measurements. Microvillus surface area increased from the bottom of the crypts to the villus tips in both resected and sham-operated animals. This increase in microvillus surface area from the crypt to the villus was significantly less pronounced after proximal resection, while there were no changes in the crypt compartment. No significant differences of the relative areas of the nuclei, mitochondria, and the rough endoplasmic reticulum were observed when comparing the different positions along the villus crypt axis in normal and hyperplastic mucosa. In agreement with functional and enzyme histochemical results, these ultrastructural findings provide further evidence for an altered pattern of enterocyte maturation after proximal resection, which is most probably due to an increase in the migration rate of the enterocytes.

The effect of epidermal growth factor on brush border surface area and function in the distal remnant following resection in the rabbit

“…2 6 Indeed, a similar increase in brush border surface area due to an increase in microvillus height has been reported in a rat model of proximal small bowel resection eight weeks postsurgery 10. In contrast, Zeitz and colleagues28 showed a significant decrease in brush border surface area in rats two, six, and 12 days postresection. The reason for this discrepancy is not clear but may be the result of differences in species and study design.…”

Patterns, Mechanisms and Signals for Intestinal Adaptation

“…Following resection there are increased cell migration rates [66. 67], but the life span of the cells may be unchanged [68] or shortened [69], If this decreased life span can be inter preted in terms of a diminished maturation of the enterocytes, the results [70] of a de creased microvillus surface area in the villus compartment may be the morphological re flection of an immature cell state. Quantita tive histochemical data [71] point in the same direction: after proximal resection, en zyme activities of two disaccharidases did not change at the base of the villi, whereas in the case of a-glucosidase the Vmax values were reduced at the transition zone between the middle and apical third of the villi in the hypoplastic mucosa, while other enzyme ac tivities remain unchanged.…”