Severe mucosal tissue damage requiring efficient wound healing is a main feature of inflammatory bowel disease but excessive tissue repair promotes fibrosis. The clinical investigation of fibrosis is confined to the limited amount of biological material available from patients. This makes the establishment of a new animal model, a highly desirable goal. We investigated whether intestinal fibrosis occurs after heterotopic transplantation of small bowel resections in rats.
Donor (Brown Norway or Lewis rats) small bowel resections were transplanted subcutaneously into the neck of recipients (Lewis rats). Grafts were explanted 2, 7, 14, and 21 days after transplantation.
Heterotopic intestinal transplants remained viable for 21 days. Rapid loss of crypt structures at day 2 after intestinal transplantation was followed by lymphocyte infiltration and obliteration of the intestinal lumen by fibrous tissue at day 21. Loss of the intestinal epithelium was confirmed by the lack of cytokeratin staining in immunohistochemistry. Collagen expression was increased with time after transplantation as confirmed by real-time PCRs, Elastica van Gieson, and Sirius Red staining. Lumen obliteration was connected with increased expression of potent mediators of fibrosis such as α5β6 integrin, interleukin (IL)-13, and transforming growth factor β. Myofibroblast phenotype was demonstrated by the presence of both α-smooth muscle actin and vimentin in the obliterated lumen.
We established a method for heterotopic transplantation of small bowel resections. A variety of histologic and molecular features of fibrosis were observed in the heterotopic intestinal grafts which suggests, that this new in vivo model will be instrumental in studying pathogenesis and treatment of intestinal fibrosis.
Article first published online 5 September 2013Supplemental Digital Content is Available in the Text.
*Department of Internal Medicine, Clinic of Gastroenterology and Hepatology, and
†Division of Pulmonology, University Hospital Zürich, Zurich, Switzerland.
Reprints: Martin Hausmann, PhD, Department of Internal Medicine, Clinic of Gastroenterology and Hepatology, University Hospital Zürich, 8091 Zurich, Switzerland (e-mail: firstname.lastname@example.org).
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Supported by grants from the Swiss National Science Foundation to M. Hausmann (SNF 31003A_127247) and G. Rogler (SNF 310030 120312) by the Deutsche Forschungsgemeinschaft (RO 1236/13-1) and the BMBF Kompetenznetz CED. G. Rogler received grant support from Abbott, Ardeypharm, Essex, FALK, Flamentera, Novartis, Roche, Tillots, UCB and Zeller. M. Hausmann was supported by Broad Medical Research Foundation (IBD-0324), G. Rogler by Swiss Inflammatory Bowel Disease Cohort Study (SIBDC), and M. Hausmann and G. Rogler were supported by the Zurich Center for Integrative Human Physiology (ZIHP).
The other authors have no conflicts of interest to disclose.
Received June 19, 2013
Accepted July 24, 2013