Ret heterozygous mice have enhanced intestinal adaptation after massive small bowel resection

Abstract

Intestinal adaptation is an important compensatory response to massive small bowel resection (SBR) and occurs because of a proliferative stimulus to crypt enterocytes by poorly understood mechanisms. Recent studies suggest the enteric nervous system (ENS) influences enterocyte proliferation. We, therefore, sought to determine whether ENS dysfunction alters resection-induced adaptation responses. Ret+/- mice with abnormal ENS function and wild-type (WT) littermates underwent sham surgery or 50% SBR. After 7 days, ileal morphology, enterocyte proliferation, apoptosis, and selected signaling proteins were characterized. Crypt depth and villus height were equivalent at baseline in WT and Ret+/- mice. In contrast after SBR, Ret+/- mice had longer villi (Ret+/- 426.7 ± 46.0 μm vs. WT 306.5 ± 7.7 μm, P < 0.001) and deeper crypts (Ret+/- 119 ± 3.4 μm vs. WT 82.4 ± 3.1 μm, P < 0.001) than WT. Crypt enterocyte proliferation was higher in Ret+/- (48.8 ± 1.3%) than WT (39.9 ± 2.1%; P < 0.001) after resection, but apoptosis rates were similar. Remnant bowel of Ret+/- mice also had higher levels of glucagon-like peptide 2 (6.2-fold, P = 0.005) and amphiregulin (4.6-fold, P < 0.001) mRNA after SBR, but serum glucagon-like peptide 2 protein levels were equal in WT and Ret+/- mice, and there was no evidence of increased c-Fos nuclear localization in submucosal neurons. Western blot confirmed higher crypt epidermal growth factor receptor (EGFR) protein levels (1.44-fold; P < 0.001) and more phosphorylated EGFR (2-fold; P = 0.003) in Ret+/- than WT mice after SBR. These data suggest that Ret heterozygosity enhances intestinal adaptation after massive SBR, likely via enhanced EGFR signaling. Reducing Ret activity or altering ENS function may provide a novel strategy to enhance adaptation attenuating morbidity in patients with short bowel syndrome.

Tissue underlying the intestinal epithelium elicits proliferation of intestinal stem cells following cytotoxic damage

“…6d), the most up-regulated was the EGF family member amphiregulin, (7.53 fold enriched) and the third highest was the BMP antagonist chordin-like 2 (4.5 fold enriched). Given the growing body of literature implicating amphiregulin in intestinal epithelial regulation (Hitch, et al, 2012, Shao and Sheng, 2010), and mounting evidence that ErbB receptor status may regulate ISC activation (Powell, et al, 2012, Wong, et al, 2012), we selected amphiregulin as an attractive candidate to test in culture for its ability to elicit crypt proliferation. Further, in view of the elevated expression of chordin-like 2, we explored the potential beneficial role of concomitant BMP antagonism.…”

Ret receptor tyrosine kinase sustains proliferation and tissue maturation in intestinal epithelia

“…Whilst the contribution of enteric aganglionosis to HSCR is unquestionable, our findings raise the possibility that, if the epithelial expression of Ret is conserved in humans, dysregulation of epithelial signalling may contribute to disorders that, like HSCR, result from Ret mutation. Epithelial Ret signalling might also contribute to other aspects of gastrointestinal physiology previously shown to be affected by reduced Ret function, such as intestinal motility, gut–microbiota interactions and the compensatory response to massive small bowel resection (Gianino et al , 2003; Hitch et al , 2012; Dey et al , 2015). Interestingly, HSCR is typically diagnosed around birth due to defects in gastrointestinal functions.…”

Nutritional strategies to enhance adaptation in intestinal failure

“…Based on findings in two intestinal transplantation cohorts we have found an increased frequency of nucleotide-binding oligomerization domain-containing protein 2 (NOD2) mutations in patients with short bowel syndrome who did not have Crohn's disease, suggesting that NOD2 plays a role in adaptation [19][20][21]. Interestingly and unexpectedly heterozygosity of the transmembrane tyrosine kinase receptor Ret, which is required for development of the enteric nervous system, leads to enhanced intestinal adaptation after massive small bowel resection [22]. This finding not only opens a new aspect of the physiology of intestinal adaptation, that is, the role of the enteric nervous system, but may even be of clinical importance, because 25-50% of patients may harbor a polymorphism, that results in lower levels of Ret protein.…”