Fig. 1.

Illustration of the surgical procedure. a–d Selected steps of surgery on anesthetized mouse in supine position after median laparotomy. Photographed through operating microscope. a Blunt separation of the mesocolon (white arrow) with mesenteric vessels from the intestine after the large and small intestine have been mobilized. b Vessel-sparing dissection of the colon. c Placement of first suture to adapt the two colonic ends. In total one mesenteric and one antimesenteric holding suture are tied. d Completed anastomosis before cropping the holding sutures (white arrows). Between them, the dorsal row of five single stitches (black arrowheads) can be seen. Final anastomosis made up of a total of 12 full thickness single stitches (2 holding sutures, 5 anterior, and 5 posterior stitches). e Overview of the experimental timeline. The experiment starts with an acclimatization phase followed by induction of colitis. DSS colitis is induced by continuous exposure to DSS in ad libitum drinking water. TNBS colitis is induced by rectal administration of TNBS 7 days after cutaneous presensibilization. In both colitis models, this phase is followed by colonoscopy to assess colitis and integrity of the colon, then by surgery, both under general anesthesia. Mice are allowed to recover while monitored, scored, and provided with pain medication until evaluation. Evaluation can take place on postoperative day 3 (POD3), POD7, or POD14 depending on the focus of research being early or late healing phases. f Everted mucosal layer after transection of the colon (black arrows)