The current status of intestinal transplantation:

Indications of Intestinal Transplantation

"The intestinal transplantation is reserved for patients with life-threatening complications of permanent intestinal failure or underlying gastrointestinal disease. The choice of the allograft for a particular patient depends on several factors and the presence of concurrent organ failure, and availability of the donor organs, and specialized care. Combined liver and intestinal transplant allows for patients who have parenteral nutrition-associated liver disease a possibility of improved quality of life and nutrition as well as survival. Intestinal transplantation has made giant strides over the past few decades to the present era where current graft survivals are comparable with other solid organ transplants."

Advances in small bowel transplantation

Small bowel transplantation is a life-saving surgery for patients with intestinal failure. The biggest problem in intestinal transplantation is graft rejection. Graft rejection is the main reason for morbidity and mortality. Rejection has a negative effect on the survival of the graft. While 50%-75% of small bowel transplantation patients experience acute rejection, chronic rejection occurs in approximately 15% of patients. Immune monitoring is crucial after small bowel transplantation. Unlike other types of transplantation, there are no non-invasive or reliable markers to predict rejection in small bowel transplantation. The diagnosis of AR is confirmed by clinical symptoms, endoscopic appearance, and pathological specimens taken by endoscopy. Thus, histopathological examinations obtained by protocol biopsies remain as the gold standard for intestinal graft monitoring; however, biopsies have some complications, especially in small grafts. In addition to the high complication rate, biopsies are non-diagnostic; thus, multiple biopsies should be performed to exclude rejection. Therefore, auxiliary assays, such as measurements of citrulline and calprotectin in the blood, cytofluorographic examination of peripheral blood immune cells, cytokine profiling, and distinct gene-set-change measurements, are increasingly being used in small bowel transplantation. Developments in the understanding of genes seem to be promising that limited gene sets, taken from blood or from intestinal biopsies, will enhance pathological diagnosis. Bone marrow mesenchymal stem cell transplantation with SBT and tissue engineering are also promising procedures.

Choice of Allograft in Patients Requiring Intestinal Transplantation: A Critical Review

Intestinal transplantation (ITx) is indicated in patients with irreversible intestinal failure (IF) and life-threatening complications related to total parenteral nutrition (TPN). ITx can be classified into three main types. Isolated intestinal transplantation (IITx), that is, transplantation of the jejunoileum, is indicated in patients with preserved liver function. Combined liver-intestine transplantation (L-ITx), that is, transplantation of the liver and the jejunoileum, is indicated in patients with liver failure related to TPN. Thus, patients with cirrhosis or advanced fibrosis should receive a combined allograft, while patients with lower grades of liver fibrosis can usually safely undergo ITx. Reflecting their degree of sickness, the waitlist mortality rate and the early posttransplant outcomes of patients receiving L-ITx are worse than IITx. However, L-ITx is associated with better long-term graft and patient survival. Multivisceral transplantation (MVTx), that is, transplantation of the organs dependent on the celiac axis and superior mesenteric artery, can be classified into full MVTx if it includes the liver and modified MVTx if it does not. The most common indications for MVTx are extensive portomesenteric thrombosis and diffuse gastrointestinal pathology such as motility disorders and polyposis syndrome. Every patient with IF should undergo a multidisciplinary evaluation by an experienced ITx team.

Proposal of intestinal tissue engineering combined with Bianchi's procedure

AIM

The aim of this study is to examine the feasibility of the small intestinal submucosa (SIS) when the longitudinal staples during Bianchi's procedure are replaced with SIS graft.

METHODS

The mesentery of the bowel was separated based on the bifurcated vessels in five beagles. A 2×7-cm longitudinal half of the bowel was excised and the defect was repaired using SIS with similar blood supply in Bianchi's operation. Six months later, intestinal motility in the SIS-grafted area was recorded. Tissue preparations were obtained from the reorganized area. An organ bath technique with electrical field stimulation was applied. Both the native small intestine and grafted area were morphologically investigated using immunohistochemistry.

MAIN RESULTS

All dogs survived and thrived with no anastomotic leakage. Isoperistaltic migrating contractility during fasting was observed through the grafted segment including the reorganized area. The SIS-reorganized tissue contracted in response to an acetylcholine agonist and electrical field stimulation. The mucosa was covered with normal epithelium. Reorganization of neural and smooth muscle cells was observed.

CONCLUSIONS

SIS has the potential for use as a scaffold that promotes the formation of a physical and physiological neointestine. Our present proposal approaches a novel surgical treatment in patients with short bowel syndrome.

A CD52 antibody impairs mouse-transplanted intestinal tight junctions

BACKGROUND

Induction immunosuppression strategies using a CD52 monoclonal antibody (mAb) have been introduced for small bowel transplantation, resulting in improved outcomes. However, little information is known about the effects of the antibody on the microstructure of the intestinal barrier, which functions to prevent bacterial translocation. In this study, we used a murine orthotopic small bowel transplantation model to investigate the impact of a CD52 mAb on tight junctions (TJs), which are considered a central part of the intestinal barrier, of the transplanted intestine.

MATERIALS AND METHODS

C57BL/6 mice were used as recipients. The grafts were harvested from BALB/c mice in allogeneic groups and C57BL/6 mice in syngeneic groups. The anti-mouse CD52 mAb was applied as a surrogate antibody. Transmission electron microscopy was used to evaluate the TJ ultrastructure. The expression of the TJ proteins occludin and ZO-1 was analyzed by Western blot. The distribution of TJ proteins was observed by immunofluorescence, and the permeability of the transplanted intestine was assessed in vivo using FITC-dextran.

RESULTS

After CD52 mAb application, a compromised TJ ultrastructure was observed. In addition, TJ protein expression (occludin and ZO-1) decreased and the intestinal permeability increased.

CONCLUSIONS

The anti-mouse CD52 mAb impaired the transplanted intestinal TJ and barrier.

Small bowel transplantation

BACKGROUND

Small bowel transplantation evolution, because of its complexity, was slower than other solid organs. Several advances have enabled its clinical application.

AIM

To review intestinal transplantation evolution and its current status.

METHOD

Search in MEDLINE and ScIELO literature. The terms used as descriptors were: intestinal failure, intestinal transplantation, small bowel transplantation, multivisceral transplantation. Were analyzed data on historical evolution, centers experience, indications, types of grafts, selection and organ procurement, postoperative management, complications and results.

CONCLUSION

Despite a slower evolution, intestinal transplantation is currently the standard therapy for patients with intestinal failure and life-threatening parenteral nutrition complications. It involves some modalities: small bowel transplantation, liver-intestinal transplantation, multivisceral transplantation and modified multivisceral transplantation. Currently, survival rate is similar to other solid organs. Most of the patients become free of parenteral nutrition.

Neurologic complications of pancreas and small bowel transplantation

In the past decade, substantial improvements in patient and graft survival for pancreas and small bowel transplants have been achieved. Despite this progress, many patients still develop neurologic complications in the course of their illness. Small bowel transplants produce more neurologic complications because of the complex metabolic environment in which the procedure is performed and because of the intense immune suppression necessitated by the greater immunogenicity of the intestinal mucosa. Pancreas transplants stabilize and/or improve the signs and symptoms of diabetic neuropathy over time. Because transplantation of the pancreas is often coupled with a kidney transplant and small intestine with liver, neurologic complications in these patients sometimes reflect problems involving the organ partner or both organs. The spectrum of neurologic complications for pancreas and small bowel transplant recipients is similar to other organ transplants but their frequency varies depending on the type of transplant performed.

Function and expression of cystic fibrosis transmembrane conductance regulator after small intestinal transplantation in mice

The secretion function of intestinal graft is one of the most important factors for successful intestinal transplantation. Cystic fibrosis transmembrane conductance regulator (CFTR) mediates HCO₃^- and Cl^- secretions in intestinal epithelial cells. In this study, we made investigation on the expression and function of CFTR in an experimental model of murine small intestinal transplantation. Heterotopic intestinal transplantations were performed in syngeneic mice. The mRNA and protein expressions of CFTR were analyzed by real time PCR and western blot. Murine intestinal mucosal HCO₃^- and Cl^- secretions were examined in vitro in Ussing chambers by the pH stat and short circuit current (I_sc) techniques. The results showed that forskolin, an activator of CFTR, stimulated jejunal mucosal epithelial HCO₃^- and Cl^- secretions in mice, but forskolin-stimulated HCO₃^- and Cl^- secretions in donor and recipient jejunal mucosae of mice after heterotopic jejunal transplantation were markedly decreased, compared with controls (P<0.001). The mRNA and protein expression levels of CFTR in donor and recipient jejunal mucosae of mice were also markedly lower than those in controls (P<0.001), and the mRNA and protein expression levels of tumor necrosis factor α (TNFα) were markedly increased in donor jejunal mucosae of mice (P<0.001), compared with controls. Further experiments showed that TNFα down-regulated the expression of CFTR mRNA in murine jejunal mucosa. In conclusion, after intestinal transplantation, the function of CFTR was impaired, and its mRNA and protein expressions were down-regulated, which may be induced by TNFα.

High molecular weight polyethylene glycol (PEG 15-20) maintains mucosal microbial barrier function during intestinal graft preservation

BACKGROUND

During organ transplantation, it is inevitable that tissues undergo cold ischemia during harvest and transport before implantation. Polyethylene-based polymers have been proposed and tested as preservation agents, with promising results. We have previously reported that a high molecular weight polyethylene glycol (PEG) (15-20,000 MW; PEG 15-20) protects the intestinal epithelium against a variety of cellular stresses, including radiation injury and microbial invasion, by mechanisms that appear to involve lipid rafts. The aim of this study was to determine the preservation effect of PEG 15-20 on the integrity of intestine grafts harvested for subsequent transplantation.

MATERIALS AND METHODS

We harvested intestinal grafts from mice using a complete surgical technique for intestinal transplantation and assessed them for the effect of PEG on graft tissue integrity. We preserved half of the grafts in histidine-tryptophan-ketoglutarate solution (HTK) alone and half in HTK-PEG 15-20 solution at 4°C for 24 h. We examined gross morphology, wet to dry ratios, histology, terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine, 5'-triphosphate nick end labeling assay for apoptosis, goblet cell numbers, and bacterial localization studies to evaluate the effect of PEG on tissue integrity.

RESULTS

Results demonstrated that PEG 15-20 had a superior preservation effect over HTK alone in all parameters tested. The effect of PEG was notable on attenuation of epithelial apoptosis, preservation of mucus-producing cells, and bacterial adherence to the epithelium.

CONCLUSIONS

Taken together, these studies suggest that use of PEG 15-20 as a potential adjuvant during intestinal transplant may offer significant promise to prolong graft survival during organ harvest.

Effects of ischemic preconditioning associated to different preservation solutions in protecting the intestinal graft

PURPOSE

To evaluate the effects of ischemic preconditioning (IPC) associate with different preservation solutions, in the protecting of gut.

METHODS

Four groups of 14 rats underwent laparotomy and collecting 20 cm of ileum, for preservation, at 4ºC, in Belzer (Belz), Ringer (RL), Celsior (Cs) and Custodiol (Cust) solutions, for 24 hours. Prior to collection, half of the animals in each group were subjected to IPC. During preservation, in the periods of zero, 12, 18 and 24 hours, were conducted evaluating the degree of mucosal injury and dosage of malondialdehyde acid (MDA).

RESULTS

In all periods the RL group, with and without IPC, presented MDA values higher than the Belz and Cs. The degree of mucosal injury in the non-ipc RLgroup with 12h preservation was higher than the others; with 18 and 24h, the RL and Cust had higher degrees of damage than Cs and Belz. With IPC, in all periods, the group Cs and Belz had lower degrees of injury.

CONCLUSION

The Celsior and Belzer solutions had better protective effects on the gut and these effects were enhanced by IPC.

The impact of MELD/PELD revisions on the mortality of liver-intestine transplantation candidates

Patients listed for liver-intestine transplantation suffer higher waiting list mortality than those listed for liver-only, thus leading to policy revisions seeking to close the gap. We sought to determine the impact of key model for end-stage liver disease (MELD)/pediatric end-stage liver disease (PELD) policy modifications on the waiting list mortality of adult and pediatric liver-intestine candidates as compared to liver-only candidates. Analysis of UNOS data separated into adult and pediatric categories and based on time periods of policy implementation revealed higher mortality in liver-intestine candidates over all time periods studied (p < 0.001 pediatric and adult). After implementation of a revision to augment their MELD scores based on a sliding scale, adult liver-intestine candidates with calculated MELD > 15 no longer suffered higher mortality although this change did not completely eliminate the mortality disparity for candidates with MELD < 15 (p < 0.01). The waiting list mortality of pediatric liver-intestine candidates dropped significantly after a revision that gave them 23 additional MELD/PELD points (p < 0.01) although the mortality disparity with pediatric liver-only candidates was not eliminated. Following this revision, mortality in pediatric liver-only and liver-intestine Status 1 candidates was similar, however more liver-intestine candidates were listed as Status 1B. This data demonstrates that a mortality disparity remains for liver-intestine candidates compared with candidates listed for liver-only.

Small bowel preservation for intestinal transplantation: a review

Intestinal transplantation has become the therapy of choice for patients with intestinal failure and life-threatening complications from total parenteral nutrition. Results, however, remain inferior as compared with other transplant types with the quality of the organ graft as the most important factor of outcome after transplantation. The intestine is extremely sensitive to ischemia. Unfortunately, a relatively long ischemic preservation period is inevitable. The current standard in organ preservation [cold storage (CS) with University of Wisconsin solution] was developed for kidney/liver preservation and is suboptimal for the intestinal graft despite good results for other organs. This review aimed at appraising the results from the use of previously applied and recently developed preservation solutions and techniques to identify key areas for improvement. As the studies available do not reveal the most effective method for intestinal preservation, an optimal strategy will result from a synergistic effect of different vital elements identified from a review of published material from the literature. A key factor is the composition of the solution using a low-viscosity solution to facilitate washout of blood, including amino acids to improve viability, impermeants and colloids to prevent edema, and buffer for pH-homeostasis. Optimizing conditions include a vascular flush before CS and luminal preservation. The most effective composition of the luminal solution and a practical, clinically applicable optimal technique are yet to reach finality. Short-duration oxygenated arterial and/or luminal perfusion have to be considered. Thus, a tailor-made approach to luminal preservation solution and technique need further investigation in transplant models and the human setting to develop the ultimate technique meeting the physiologic demands of the intestinal graft during preservation.