Functional, histological, and inflammatory changes in chronically rejecting small bowel transplants

Update on Chronic Rejection After Intestinal Transplant: An Overview From Experimental Settings to Clinical Outcomes

Chronic rejection affects the long-term survival of solid-organ transplants, accounting for an incidence of between 5% and 10% after intestinal/multivisceral transplant. Because of unclear symptoms and signs and endoscopic findings, the diagnosis is often delayed. Presently, allograft removal represents the only available therapy due to the absence of effective pharmacologic approaches. Extensive research, through animal models, has been performed over the past 20 years to clarify the complex immune- and nonimmune-mediated mechanisms behind the development of chronic allograft enteropathy, with the aim of elucidating how to avert chronic rejection. The role of donor-specific antibodies and the way to challenge them in the clinic have gained acceptance among transplant centers as one of the main steps to prevent chronic rejection, although no common protocol exists that can be applied in a systematic fashion. The adjunct of a liver graft when retrans planting is needed in a sensitized recipient due to its protective effect against humoral immunity. Multicenter studies and clinical trials are required to better understand the pathogenesis of chronic rejection and to find the therapeutic answer to this clinical query.

[Small intestine, pancreas and islet cell transplantation]

The past decade has seen substantial improvements in patient and graft survival after intestinal transplantation. This improvement has been achieved by advances in donor and recipient selection, patient management, immunosuppression and surgical techniques. Intestinal transplantation is therefore considered a therapeutic option in the treatment of short bowel syndrome. Mile stones include the development of the calcineurin inhibitor Tacrolimus for immunosuppression as well as induction therapy using immune modulating substances like interleukin-2 receptor antagonists and antilymphocyte preparations. In addition to improvements in immunosuppression, antimicrobial prophylaxis and diagnosis of rejection, advances in surgical techniques have been crucial to achieving increased graft survival. Pancreas transplantation, generally with simultaneous kidney transplantation, is now available as a treatment option for patients with labile diabetes mellitus (usually type 1). Allogeneic islet transplantation was developed in the 1990s as a minimally invasive alternative to pancreas transplantation. Pancreatic islets are isolated enzymatically from the donor pancreas, in most cases infused into the portal vein and thus engrafted into the liver. Currently, technical and medical problems as well as high costs prevent the application of islet transplantation as a therapeutic option for a larger number of patients with diabetes mellitus.

Current status of transplantation of the small intestine

The evolution of small bowel transplantation has been significant over the past 20 years to the point at which it can now be considered a viable and often successful option in the treatment of many forms of short bowel syndrome. A refinement of surgical techniques, improved immunosuppression, enhanced understanding of gut immunology, and better treatment and prevention of complications have contributed to a marked improvement in graft and patient survival. Whereas this transplant population is still beset with many potential complications after isolated bowel or multivisceral transplantation and long-term graft survival (like with other solid organ transplants) remains a challenge, the future holds promise for a continuation of the current positive trend of improvement in several areas.

Features of chronic allograft rejection on rat small intestine transplantation

The aim of this study was to develop a model of chronic rejection of the entire small intestine transplantation and to analyze the features of chronic rejection. Allogenic small bowel transplantation was performed in a rat combination of Lewis to F344. Intestines were procured at the 60th and the 90th day after operation. We compared the semiquantitative score of histological parameters. The immunological components involved in the chronic rejection process were evaluated by immunohistochemical staining and the cytokine levels in grafts. The significant characteristics of the allograft on histology were changes of villous architecture, interstitial fibrosis, leukocyte infiltration, and obliterative arteriopathy. Allografts on the 60th day post-transplantation had more score in inflammatory events, while the grafts on the 90th day after operation had more values in ischemia/fibrotic events. The number of infiltrating CD4, CD8 and macrophage cells in allografts progressively decreased over time. The level of intragraft cytokines such as IL-6, TNF-alpha and IL-10 in the 90th day after transplantation also decreased compared with that in the 60th day. These data suggested that in the early stage (POD 60), there were more active and intense inflammatory events; later (POD 90) allografts manifested less inflammation and more arterial obliteration and fibrosis.

Sclerosing peritonitis after intestinal transplantation in children

Long-term graft dysfunction and/or graft loss after intestinal transplantation (ITx) is a significant concern. Sclerosing peritonitis (SP) is a manifestation of chronic allograft failure and its presence may also include classic arterial obliterative arteriopathy (OA) as in chronic rejection. We describe the clinical presentation and management of SP occurring after ITx in children. Case records of 121 children undergoing ITx from 1990 to 2003 were reviewed. Three children (2.4%) presented with SP of the intestine allograft at a mean time of 6.6 yr following ITx as follows: age at Tx (yr) 8.2, and 3.7, with indication for ITx being gastroschisis in two and midgut volvulus in one patient. Type of ITx was isolated intestine in one and liver/intestine in two patients. Gross findings of SP included fibrosis/strictures; microscopically SP showed fibrosis/serositis, and fibrous adhesions; one patient had evidence of chronic allograft vasculopathy. All patients presented with clinical signs and symptoms of bowel obstruction and gastrointestinal contrast studies confirmed distal ileal obstruction (DIO). Operative findings confirmed SP and DIO in all patients; all patients were initially treated with distal segmental intestine allograft resection and lysis of the fibrous peel. All three patients recovered, although two required repeat laparotomy, there is only one long-term survival. SP after ITx may be a different manifestation of long-term intestine allograft degeneration. Surgical resection appears to offer palliation.