Small-bowel transplantation in the rat with a nonsuture cuff technique. Technical and immunological considerations

Difficulties, guidelines and review of developing an acute rejection model after rat intestinal transplantation

Experimental small bowel transplantation (SBT) in rats has been proven to be a useful tool for the study of ischemia-reperfusion and immunological aspects related to solid organ transplantation. However, the model is not completely refined, specialized literature is scarce and complex technical details are typically omitted or confusing. Most studies related to acute rejection (AR) use the orthotopic standard, with small sample sizes due to its high mortality, whereas those studying chronic rejection (CR) use the heterotopic standard, which allows longer term survival but does not exactly reflect the human clinical scenario. Various animal strains have been used, and the type of rejection and the timing of its analysis differ among authors. The double purpose of this study was to develop an improved unusual AR model of SBT using the heterotopic technique, and to elaborate a guide useful to implement experimental models for studying AR. We analyzed the model's technical details and expected difficulties in overcoming the learning curve for such a complex microsurgical model, identifying the potential problem areas and providing a step-by-step protocol and reference guide for future surgeons interested in the topic. We also discuss the historic and more recent options in the literature.

Improved technique of vascular anastomosis for small intestinal transplantation in rats

AIM: To establish a new improved vascular anastomotic technique to simplify the surgical technique and increase the survival rate of small intestinal transplantation in rats.

METHODS: The graft removed enbloc consisted of entire small intestine, portal vein and aortic segment with superior mesenteric artery. The graft was perfused in situ and the gut lumen was irrigated during the operation. Heterotopic small bowel transplantation was performed by microvascular end-to-side anastomosis between the donor aortic segment with superior mesenteric artery and the recipient abdominal aorta, and by the formation of a “Cuff” anastomos is between the donor portal vein and the recipient left renal vein. Both ends of the grafts were exteriorized as stomas.

RESULTS: A total of 189 intestinal transplantations were performed in rats, 33 of which were involved in the formal experimental group, with a survival rate of 84.8%. The average time for the donor surgery was 80 min ± 10 min; for graft repair 10 min ± 3 min; and for recipient surgery 95 min ± 15 min. The average time for the arterial anastomosis and the vein anastomosis was 18 min ± 5 min and 1 min, respectively. The warm ischemic time and cold ischemic time were 22 min ± 5 min and less than 60 min, respectively. The whole operation was completed by a single surgeon, the operative time being about 3 h.

CONCLUSION: The vascular anastomosis used in this study could simplify surgical technique, reduce the operative time and elevate the survival rate of small intestinal transplantation in rats.

Vascular anastomotic techniques for experimental intestinal transplantation

A comparison of two techniques for the vascular anastomosis of intestinal transplants in the rat suggests that the use of an aortic segment with the graft leads to reduced operative time and improved technical success.

Small bowel transplantation in rats: endoscopic and histological evaluation of graft rejection

Heterotopic small bowel transplantation was performed using the cuff technique in DA(RT1a) to PVG(RT1c) rat fully allogeneic combination. In this model, the rejection course of the grafted intestine was evaluated endoscopically via double stomata and was classified into four stages. Early changes appeared on postoperative day 3. Stage I: The mucosa of the grafted intestine showed patchy paleness and loss of the capillary fine network patterns, accompanied by microerosions. Closer examination revealed irregularity of the epithelial height and arrangement. Stage II: The damage spread progressively over the entire mucosa on day 4-5. Stage III: On day 6-7, the necrotic epithelium became detached, showing multiple ulcers which provoked hemorrhagic enteritis. Stage IV: Graft rejection was completed with total necrosis and white scar tissue formation by day 10-14. These endoscopic findings of the mucosa of the grafted intestine corresponded closely to the time course of pathological examinations. We conclude that endoscopic examination of grafted intestine may be an effective diagnostic tool to detect the rejection phenomenon at an early stage, as well as a simple tool to use for postoperative follow-up in combination with pathological examination.

Immunomorphology of graft-versus-host disease after small bowel transplantation in the rat

The process of graft-versus-host disease (GVHD) elicited by small bowel semi-syngeneic grafts in Lewis rats was studied by an immunohistochemical staining technique for analysis of MHC (major histocompatibility complex) class II antigen expression and of T-cell subpopulations in different organs. Specimens from the graft, native bowel, brain, testis, liver, kidney, and skin were taken on days 5, 10, and 15. All the investigated organs displayed strong class II antigen induction during the course of GVHD. In the native bowel of semi-syngeneically transplanted animals, only discrete morphological changes were noted, whereas the graft displayed a generalized serosal reaction with large infiltrates of rounded and polygonal cells expressing class II antigens. This was not observed in the graft of syngeneically transplanted animals. In the lamina propria of the semisyngeneic graft, 'free' lymphocyte-like cells were depleted and, at the same time, localized aggregates of these cells were observed. Crypt cell class II expression in the native bowel, and to some extent in the graft, was increased during GVHD. However, pronounced intraindividual variations in MHC class II antigen expression were noted, and class II expression was therefore not considered to be a good marker for GVHD.