Transplantation of Human Intestine Into the Mouse: A Novel Platform for Study of Inflammatory Enterocutaneous Fistulas.

BACKGROUND AND AIMS: Enteric fistulas represent a severe and medically challenging comorbidity commonly affecting Crohn's disease [CD] patients. Gut fistulas do not develop in animal models of the disease. We have used transplantation of the human fetal gut into mice as a novel platform for studying inflammatory enterocutaneous fistulas. METHODS: Human fetal gut segments were transplanted subcutaneously into mature SCID mice, where they grew and fully developed over the course of several months. We first analysed the resident immune cells and inflammatory response elicited by systemic lipopolysaccharide [LPS] in normal, fully developed human gut xenografts. Thereafter, we used immunostaining to analyse fully developed xenografts that spontaneously developed enterocutaneous fistulas. RESULTS: Resident human innate and adaptive immune cells were demonstrated in gut xenografts during steady state and inflammation. The expression of human IL-8, IL-1ß, IL-6, TNF-α, A20, and IkBα was significantly elevated in response to LPS, with no change in IL-10 gene expression. Approximately 17% [19/110] of fully developed subcutaneous human gut xenografts spontaneously developed enterocutaneous fistulas, revealing striking histopathological similarities with CD fistula specimens. Immunohistochemical analyses of fistulating xenografts revealed transmural lymphocytic enteritis associated with massive expansion of resident human CD4+ lymphocytes and their migration into the intraepithelial compartment. Regionally, mucosal epithelial cells assumed spindle-shaped mesenchymal morphology and formed fistulous tracts towards chronic non-healing wounds in the host mouse skin overlying the transplants. CONCLUSIONS: Inflammation and fistulas developed in human gut xenografts lacking IL-10 gene response. This novel model system will enable systematic studies of the inflamed and fistulating human gut in live animals.

Eribulin Does Not Prevent Epithelial-to-Mesenchymal Transition in HT-29 Intestinal Epithelial Cells.

BACKGROUND: Fistula formation affects up to 50$ of Crohn's disease (CD) patients and causes considerable morbidity. Current pharmacological management mainly includes antibiotics, immunosuppressives, and anti-TNF antibodies. CD fistulas develop from intestinal epithelial cells undergoing epithelial-to-mesenchymal transition (EMT). TGFß, the most important inducer of EMT, is detectable around CD fistula tracts and induces expression of the EMT-associated transcription factors SNAIL1 and SLUG as well as of IL-13. Conversely, together with TNF, IL-13 induces the expression of the transcription factor Ets-1 and ß6-integrin, which are associated with cell invasiveness. Eribulin is a synthetic derivative of halichondrin B, a large polyether macrolide, which reverses EMT in triple-negative breast cancer (TNBC) cells. Here, we investigated whether Eribulin might be a potential therapeutic option for CD fistulas via the inhibition of EMT. SUMMARY: Chronic treatment with high concentrations of Eribulin (> 5 ng/ml) is toxic for intestinal epithelial cells (IEC), and Eribulin treatment does not decrease the mRNA expression of EMT markers in HT-29 monolayers nor prevent EMT in HT-29 spheroids. Together with TNF, Eribulin induces the expression of vimentin and SLUG mRNA in HT-29 spheroids but concomitantly also promotes E-cadherin expression. KEY MESSAGES: Our data suggest that the previously reported antimetastatic effect of Eribulin in TNBC by reversing EMT does not apply to IEC. Interestingly, Eribulin promotes E-cadherin expression, suggesting an additional mechanism. The increase of E-cadherin might point towards the described role for Eribulin in reversing EMT. Taken together, our data do not support a role for Eribulin as treatment option for CD-associated fistulas.