Morphological, Molecular and Motility Changes in Human Small Intestine After Loop Ileostomy

: Morphological and functional changes occur after loop ileostomy surgery such as villous atrophy and decreased contractility. This study aims to examine the changes in motility of the proximal and distal limbs of the ileostomy. Morphological, molecular and functional approaches of smooth muscle are attempted to elucidate the cause of the changes in motility.

: Full thickness strips of circular muscle were prepared from 25 patients (median age 64 years). Western blot was performed to quantify the expression of contractile proteins. Expression of genes was quantified using quantitative real-time polymerase chain reaction.

: The distal limb showed morphological atrophy and a significant reduction in the contractile response to acetylcholine and potassium chloride, as well as a reduced relaxation response to sodium nitroprusside. However, no changes in the number of platelet derived growth factor receptor-α-positive (PDGFRα⁺) cells and interstitial cell of Cajal (ICC) were observed between the proximal and distal limbs. Western blot analysis confirmed that the expression levels of proteins associated with contraction such as myosin phosphatase targeting subunit 1, protein kinase C-potentiated phosphatase inhibitor protein-17 kDa, and Rho-associated, coiled-coil containing protein kinase 1, were significantly down-regulated in the distal limb. Despite the decrease in the expression of these proteins, neuronal cells and smooth muscle cells were preserved in the distal limb that has been diverted after ileostomy.

: Although morphological, molecular and motility changes including down-regulation of contractile protein expression were observed in the distal loop, number of PDGFRα⁺ cells, ICCs, and neuronal cells were preserved. These results may explain restoration of the bowel motility after ileostomy take-down with low incidence of ileus.