Clinical intestinal transplantation: new perspectives and immunologic considerations

The influence of surgery, immunosuppressive drugs, and rejection, on graft function after small bowel transplantation: a large-animal study

In this study we assessed functional changes (motility and absorption) of intestinal allografts in a large-animal model of orthotopic small bowel transplantation in swine. Studies were performed on non-rejecting animals in the early and late stages after transplantation and after induction of different grades of acute rejection. Immunosuppression consisted of oral FK506 and mycophenolate mofetil. In each study group we regulated drug administration, in terms of dosage and timing, in order to induce different grades of acute rejection or to prevent it. Migrating myoelectrical complexes were recorded in fasting animals so that motility could be assessed. Mucosal biopsy of the allograft and D-xylose absorption tests were performed on the same day as the motility study. In the early stages following intestinal transplantation, we observed in non-rejecting animals a slightly increased graft motility and a marked carbohydrate malabsorption. Recovery of the carbohydrate absorption capacity occurs within 2 months, but the persistence of diarrhea leads to partial malabsorption and to a lack of normal weight gain. Motility reduction correlates with the grade of acute rejection and becomes significant at a later stage, when rejection is severe. Allograft carbohydrate absorption, on the contrary, is markedly reduced in all rejecting pigs, irrespective of the grade of rejection. In summary, the early functional impairment of non-rejecting animals has multifactorial causes due to surgery and immunosuppression (drug toxicity), and its occurrence suggests the need for specific guidelines for clinical early postoperative enteral feeding. The functional studies adopted here are helpful in defining the grade of functional impairment with or without acute rejection; however, they are not useful for early detection of ongoing acute rejection of the small bowel graft.

Chronic rejection of small bowel grafts: pediatric and adult study of risk factors and morphologic progression

One hundred and seventy-two patients underwent small bowel transplantation at Children's Hospital of Pittsburgh and University of Pittsburgh Medical Center between May 1990 and August 2001. Thirty-four patients had complete or partial resection of their primary graft and in 15, histologic features of chronic rejection were present in the resected small bowel. This is a descriptive and correlative study of the demographic, perioperative, and histologic features associated with progression to intestinal graft failure. Variable features associated with an increased risk of chronic rejection included acute rejection within the 1st month, increased number and higher grade of acute rejection episodes, isolated small bowel grafts rather than small bowel-liver grafts, older recipient age, non-Caucasian race, and Caucasian to non-Caucasian transplant. The mucosal biopsies showed predictive changes many months before the grafts were excised. The mucosal biopsy diagnosis of chronic vascular rejection can be difficult because the affected vessels, the distal branches of the mesenteric arteries, and the larger arteries of the subserosa and submucosa are not routinely sampled. The possibility of underlying arteriopathy, however, can be inferred in some instances from the presence of secondary mucosal changes in the small bowel biopsies though the "early" changes lack specificity. It is the progression of biopsy findings over time that is predictive of outcome. It is important to recognize the persistence of "late" mucosal changes of chronic rejection so that patients are not subjected to increased immune suppression when it is unlikely to be of significant benefit.

A schema for histologic grading of small intestine allograft acute rejection

BACKGROUND

Histologic evaluation of small bowel allograft biopsies is important for the diagnosis of acute rejection. However, a standard histologic schema to grade the severity of intestinal acute rejection is not currently available. The primary goal of this study was to develop a histologic grading system for the diagnosis of small bowel allograft acute rejection.

METHODS

We evaluated 3268 small bowel allograft biopsies obtained from adult patients who underwent small bowel transplantation at the University of Pittsburgh Medical Center between 1990 and 1999. A histologic grading system was proposed and validated by retrospective correlation with clinical outcomes.

RESULTS

Among the 3268 biopsies, 180 acute rejection episodes were diagnosed (88 indeterminate, 74 mild, 14 moderate, and 4 severe). All four histologically diagnosed, severe acute rejection episodes resulted in graft failure before resolution, despite aggressive immunosuppressive therapy. Four of the 14 moderate acute rejection episodes were associated with unfavorable clinical outcomes. In contrast, the 74 mild and 88 indeterminate acute rejection episodes were not associated with unfavorable clinical outcomes. Statistical analysis for trend revealed that grades indicating more severe acute rejection episodes were associated with a greater probability of unfavorable outcomes (P<0.01). In addition, there was good overall agreement among different pathologists regarding the diagnosis of acute rejection using the proposed schema, suggesting that this system is practical.

CONCLUSIONS

This study provides a reliable predictive schema for assessment of the severity of human small bowel acute rejection.

Small bowel transplant: an evidence-based analysis

OBJECTIVE

The Medical Advisory Secretariat undertook a review of the evidence on the effectiveness and cost-effectiveness of small bowel transplant in the treatment of intestinal failure.

SMALL BOWEL TRANSPLANTATION

Intestinal failure is the loss of absorptive capacity of the small intestine that results in an inability to meet the nutrient and fluid requirements of the body via the enteral route. Patients with intestinal failure usually receive nutrients intravenously, a procedure known as parenteral nutrition. However, long-term parenteral nutrition is associated with complications including liver failure and loss of venous access due to recurrent infections. Small bowel transplant is the transplantation of a cadaveric intestinal allograft for the purpose of restoring intestinal function in patients with irreversible intestinal failure. The transplant may involve the small intestine alone (isolated small bowel ISB), the small intestine and the liver (SB-L) when there is irreversible liver failure, or multiple organs including the small bowel (multivisceral MV or cluster). Although living related donor transplant is being investigated at a limited number of centres, cadaveric donors have been used in most small bowel transplants. The actual transplant procedure takes approximately 12-18 hours. After intestinal transplant, the patient is generally placed on prophylactic antibiotic medication and immunosuppressive regimen that, in the majority of cases, would include tacrolimus, corticosteroids and an induction agent. Close monitoring for infection and rejection are essential for early treatment.

MEDICAL ADVISORY SECRETARIAT REVIEW

The Medical Advisory Secretariat undertook a review of 35 reports from 9 case series and 1 international registry. Sample size of the individual studies ranged from 9 to 155. As of May 2001, 651 patients had received small bowel transplant procedures worldwide. According to information from the Canadian Organ Replacement Register, a total of 27 small bowel transplants were performed in Canada from 1988 to 2002.

PATIENT OUTCOMES

The experience in small bowel transplant is still limited. International data showed that during the last decade, patient survival and graft survival rates from SBT have improved, mainly because of improved immunosuppression therapy and earlier detection and treatment of infection and rejection. The Intestinal Transplant Registry reported 1-year actuarial patient survival rates of 69% for isolated small bowel transplant, 66% for small bowel-liver transplant, and 63% for multivisceral transplant, and a graft survival rate of 55% for ISB and 63% for SB-L and MV. The range of 1-year patient survival rates reported ranged from 33%-87%. Reported 1-year graft survival rates ranged from 46-71%. Regression analysis performed by the International Transplant Registry in 1997 indicated that centres that have performed at least 10 small bowel transplants had better patient and graft survival rates than centres that performed less than 10 transplants. However, analysis of the data up to May 2001 suggests that the critical mass of 10 transplants no longer holds true for transplants after 1995, and that good results can be achieved at any multiorgan transplant program with moderate patient volumes. The largest Centre reported an overall 1-year patient and graft survival rate of 72% and 64% respectively, and 5-year patient and graft survival of 48% and 40% respectively. The overall 1-year patient survival rate reported for Ontario pediatric small bowel transplants was 61% with the highest survival rate of 83% for ISB. The majority (70% or higher) of surviving small bowel transplant recipients was able to wean from parenteral nutrition and meet all caloric needs enterally. Some may need enteral or parenteral supplementation during periods of illness. Growth and weight gain in children after ISB were reported by two studies while two other studies reported a decrease in growth velocity with no catch-up growth. The quality of life after SBT was reported to be comparable to that of patients on home enteral nutrition. A study found that while the parents of pediatric SBT recipients reported significant limitations in the physical and psychological well being of the children compared with normal school children, the pediatric SBT recipients themselves reported a quality of life similar to other school children. Survival was found to be better in transplants performed since 1991. Patient survival was associated with the type of organ transplanted with better survival in isolated small bowel recipients.

ADVERSE EVENTS

Despite improvement in patient and graft survival rates, small bowel transplant is still associated with significant mortality and morbidity. Infection with subsequent sepsis is the leading cause of death (51.3%). Bacterial, fungal and viral infections have all been reported. The most common viral infections are cytomegalorvirus (18-40%) and Epstein-Barr virus. The latter often led to ß-cell post-transplant lymphoproliferative disease. Graft rejection is the second leading cause of death after SBT (10.4%) and is responsible for 57% of graft removal. Acute rejection rates ranged from 51% to 83% in the major programs. Most of the acute rejection episodes were mild and responded to steroids and OKT3. Antilymphocyte therapy was needed in up to 27% of patients. Isolated small bowel allograft and positive lymphocytotoxic cross-match were found to be risk factors for acute rejection. Post-transplant lymphoproliferative disease occurred in 21% of SBT recipients and accounted for 7% of post-transplant mortality. The frequency was higher in pediatric recipients (31%) and in adults receiving composite visceral allografts (25%). The allograft itself is often involved in post-transplant lymphoproliferative disease. The reported incidence of host versus graft disease varied widely among centers (0% - 14%). Surgical complications were reported to occur in 85% of SB-L transplants and 25% of ISB transplants. Reoperations were required in 45% - 66% of patients in a large series and the most common reason for reoperation was intra-abdominal abscess. The median cost of intestinal transplant in the US was reported to be approximately $275,000US (approximately CDN$429,000) per case. A US study concluded that based on the US cost of home parenteral nutrition, small bowel transplant could be cost-effective by the second year after the transplant.

CONCLUSION

There is evidence that small bowel transplant can prolong the life of some patients with irreversible intestinal failure who can no longer continue to be managed by parenteral nutrition therapy. Both patient survival and graft survival rates have improved with time. However, small bowel transplant is still associated with significant mortality and morbidity. The outcomes are inferior to those of total parenteral nutrition. Evidence suggests that this procedure should only be used when total parenteral nutrition is no longer feasible.

Current concepts in radiation enteritis and implications for future clinical trials

BACKGROUND

Radiation enteritis is one of the most feared complications of abdominal and pelvic radiation. Once its occurs, the process is relentless and may result in the patient's death. Available treatment is only supportive. Recent progress in molecular biology has shed some light on the pathogenesis of radiation enteritis and other diseases that are characterized by excessive fibrosis. New treatment modalities may be devised to improve the outcome of patients who are affected with this complication.

METHODS

A literature search was used to identify the common denominator between many radiation-induced fibrotic conditions and other sclerotic diseases. Factors that affect the disease process and possible therapeutic interventions were evaluated.

RESULTS

The hyperstimulation of transforming growth factor beta1 (TGF-beta1) leads to increased fibrosis and, ultimately, organ failure. Interferon gamma (IFN-gamma) inhibits the effects of TGF-beta1 in the nucleus. The fibrotic process may be reverted by IFN-gamma in various pathologic conditions.

CONCLUSIONS

Radiation enteritis and other radiation-induced, long-term complications are characterized by excessive stimulation of TGF-beta1. Preliminary studies suggest that IFN-gamma may be effective in the treatment of patients with radiation-induced cutaneous fibrosis. IFN-gamma should be considered in Phase I-II studies to assess its toxicity and efficacy in the treatment of patients with radiation enteritis.

An integrated approach to intestinal failure: results of a new program with total parenteral nutrition, bowel rehabilitation, and transplantation

Intestinal failure can be treated with bowel rehabilitation, total parenteral nutrition, or intestinal transplantation. Little has been done to integrate these therapies for patients with intestinal insufficiency or failure and to develop an algorithm for appropriate use and timing. We established a multidisciplinary program using bowel rehabilitation, total parenteral nutrition, or intestinal transplantation as appropriate in a large population. Evaluation included clinical, pathologic, and psychosocial assessments and assignment to therapy based on the results of this evaluation. Of 59 patients evaluated for life-threatening complications of intestinal failure, 68% were considered appropriate candidates for transplantation, 10% were managed with rehabilitation, and 17% were maintained on optimized long-term parenteral nutrition. Nineteen transplants were performed, with 78% patient survival and 66% graft survival. Patient survival among isolated intestine recipients was 90%. All patients managed with rehabilitation were weaned from parenteral nutrition within 6 months. Long-term management with parenteral nutrition resulted in a significant number of deaths both among patients waiting for a transplant and those who were poor candidates for transplant. Intestinal rehabilitation, when successful, is optimal. For patients with irreversible intestinal failure, isolated intestinal transplantation holds particular promise. Parenteral nutrition is plagued by high failure rates among this population of debilitated patients compared with the general parenteral nutrition population. Integration of these therapies, with individualization of care based on a multidisciplinary approach and perhaps with earlier isolated intestinal transplantation for patients with irreversible intestinal failure, should optimize survival.

Successful tolerance induction under CD40 ligation in a rodent small bowel transplant model: first report of a study with the novel antibody AH.F5

BACKGROUND

Intestinal transplantation has been hampered by high rates of intestinal allograft rejection. One mechanism of altering rejection in other organ transplant models has been blockade of second set T-cell costimulatory signals. AH.F5, a novel hamster anti-rat monoclonal antibody to CD154, blocks CD40-dependent T-cell costimulation. We hypothesized that blockade of this pathway might abrogate rejection in a rodent orthotopic survival model of intestinal transplantation.

METHODS

Eight groups were studied with different dosing schema, including syngeneic transplants (group 1), untreated allogeneic transplants (group 2), allogeneic transplants plus multiple doses of AH.F5 alone given IV or s.c. (groups 3 and 4), allogeneic transplants plus donor splenocyte preconditioning with and without single dose AH.F5 (groups 5 and 6), and donor splenocyte preconditioning followed by multiple doses of AH.F5 with and without thymectomy (groups 7 and 8).

RESULTS

Control animals all died within 12 days of transplantation, whereas antibody-alone and splenocytes-alone resulted in modest prolongation of survival to 16 days. Only animals treated with splenocytes before transplantation and AH.F5 survived long-term (>60 days, group 8). These animals tolerated donor-specific skin grafts, rejected third-party grafts, and fed normally. However, their weight gain was subnormal and they demonstrated intestinal muscular thickening, which might represent chronic rejection. Thymectomy prevented the induction of tolerance.

CONCLUSIONS

AH.F5 prevents acute intestinal allograft rejection in combination with donor-specific splenocyte preconditioning. We achieved long-term survival and the animals appeared tolerant. Central conditioning is essential for success with this antibody when used alone. Further studies with different dosing regimens or second agents seem warranted.

Intestinal transplantation in pediatric patients

Intestine transplantation has evolved into a feasible alternative for children with permanent intestinal failure and life-threatening complications related to total parenteral nutrition. Although the first transplantations were done nearly 40 years ago, long-term survival has only been achieved in the last decade. Nearly 700 intestinal transplantations have been performed internationally since 1985, with an overall patient survival of greater than 50%. Improvements in patient selection, medical management, and assessment and treatment for rejection and infection have contributed to the increased survival. This article will discuss current results and medical management strategies for this innovative type of transplantation for children with end-stage short gut syndrome.

Donor T cell activation initiates small bowel allograft rejection through an IFN-gamma-inducible protein-10-dependent mechanism

The poor success in controlling small bowel (SB) allograft rejection is partially attributed to the unique immune environment in the donor intestine. We hypothesized that Ag-induced activation of donor-derived T cells contributes to the initiation of SB allograft rejection. To address the role of donor T cell activation in SB transplantation, SB grafts from DO11.10 TCR transgenic mice (BALB/c, H-2L(d+)) were transplanted into BALB/c (isografts), or single class I MHC-mismatched (L(d)-deficient) BALB/c H-2(dm2) (dm2, H-2L(d-)) mutant mice (allografts). Graft survival was followed after injection of control or antigenic OVA(323-339) peptide. Eighty percent of SB allografts developed severe rejection in mice treated with antigenic peptide, whereas <20% of allografts were rejected in mice treated with control peptide (p < 0.05). Isografts survived >30 days regardless of OVA(323-339) administration. Activation of donor T cells increased intragraft expression of proinflammatory cytokine (IFN-gamma) and CXC chemokine IFN-gamma-inducible protein-10 mRNA and enhanced activation and accumulation of host NK and T cells in SB allografts. Treatment of mice with neutralizing anti-IFN-gamma-inducible protein-10 mAb increased SB allograft survival in Ag-treated mice (67%; p < 0.05) and reduced accumulation of host T cells and NK cells in the lamina propria but not mesenteric lymph nodes. These results suggest that activation of donor T cells after SB allotransplantation induces production of a Th1-like profile of cytokines and CXC chemokines that enhance infiltration of host T cells and NK cells in SB allografts. Blocking this pathway may be of therapeutic value in controlling SB allograft rejection.

Protective effects of ex vivo graft radiation and tacrolimus on syngeneic transplanted rat small bowel motility

BACKGROUND

Intestinal transplantation is unduly complicated by the nontolerogenic properties of the gut-associated lymphoid tissue. Because simultaneous graft irradiation and bone marrow infusion significantly prolong the survival of the small bowel transplanted animal, our objective was to determine the functional motility effects of the immune modulating, graft irradiation procedure in the presence and absence of tacrolimus immunosuppression.

METHODS

Four groups of syngeneic orthotopic small bowel transplanted animals were studied 48 hours after operations (untreated, tacrolimus, ex vivo graft irradiation, and tacrolimus + irradiation) and compared with controls. Histologic analysis was performed for mucosal apoptosis and neutrophilic infiltration into the muscularis externa. Gastrointestinal in vivo transit and in vitro circular muscle strip contractions were quantified in response to bethanechol (0.3-300 micromol/L).

RESULTS

Graft irradiation ex vivo alone or in the presence of tacrolimus significantly increases (> 10-fold) the number of apoptotic mucosal cells after transplantation. Functional measurements showed that transplantation resulted in a significant delay in gastrointestinal transit and a decrease in muscle strip contractility. Tacrolimus and graft irradiation significantly ameliorated the transplant-induced dysfunction.

CONCLUSIONS

Given the endowed propensity of mucosal regeneration, the immunologic and functional benefits of ex vivo graft irradiation appear to outweigh the detrimental effects to the mucosa.

Complete freedom from rejection after intestinal transplantation using a new tolerogenic protocol combined with low immunosuppression

BACKGROUND

Intestinal transplantation (Itx) remains the most difficult form of transplantation. This is due to the high immunogenicity of the bowel that currently obligates Itx patients to heavy immunosuppression, which causes infection, posttransplant lymphoproliferative disease (PTLD), and drug toxicity. Wider application of Itx depends on the development of tolerogenic strategies to promote engraftment while reducing the need for immunosuppression. We applied a strategy to clinical Itx that combines intraportal donor-specific blood transfusion with a deliberately low immunosuppression protocol (no high-dose steroids; lower tacrolimus level).

METHODS

A 55-year-old patient received a combined liver/Itx. Donor-specific whole blood was taken from the donor during procurement and transfused in the recipient portal vein after graft reperfusion. For induction immunosuppression, no intravenous bolus of steroids was given; only two doses of anti-interleukin 2 receptor antibody were administered. The patient received posttransplantation maintenance immunosuppression with lower tacrolimus levels than average (15 ng/ml first month; 5-10 ng/ml thereafter), low-dose azathioprine (1 mg/kg first to third months; 0.5 mg/kg thereafter), and low-dose steroids (Medrol 8 mg twice daily first and second months; 4 mg twice thereafter). The patient was monitored for rejection, graft-versus-host disease, infection, and PTLD. Protocol biopsy specimens were taken from the distal ileum (2 per week).

RESULTS

Clinical, endoscopic, and histologic signs of rejection did not develop. Chimerism was identified at day 28. Graft-versus-host disease was absent clinically. Chimerism was self-limiting and disappeared without modifying baseline immunosuppression and without observing a change in graft function. The patient remained free of systemic opportunistic infections, PTLD, and drug toxicity. Total parenteral nutrition was stopped at 7 weeks after transplantation. The patient remains free of total parenteral nutrition and free of rejection at 14 months after transplantation.

CONCLUSIONS

We describe an Itx patient who remained rejection free despite receiving significantly lower immunosuppression than average. We hypothesize that intraoperative immunomodulation via intraportal donor-specific blood transfusion in the absence of nonspecific overimmunosuppression promoted Itx acceptance.

Neurologic complications of transplantation

BACKGROUND

Organ transplantation is one of the most dynamic fields in medicine and has evolved into a life-saving option for thousands of patients with previously fatal conditions. The posttransplantation clinical course is frequently associated with neurologic complications that are usually related to pretransplant morbidity, the surgical procedure of transplantation, immunosuppression, and opportunistic infection.

REVIEW SUMMARY

Neurologic complications of organ transplantation may be divided into complications common to all types of allografts and complications that are specific for a particular type of organ transplantation. The most common complications include seizures, opportunistic central nervous system (CNS) infection, metabolic encephalopathy, stroke, intracranial hemorrhage, and drug-related adverse events. Opportunistic CNS infection may have a subtle presentation and should not be overlooked, as the consequences of delayed treatment may be grave. Neurotoxicity of immunosuppressive agents is also a frequent cause of neurologic complications and may occur in the setting of normal serum drug levels. The clinical course of transplant patients is frequently complex, requiring close cooperation between the transplant team and specialty consultants. Prolonged survival of transplant patients will shift the focus of neurologic complications from acute, perioperative to chronic complications of immunosuppression.

CONCLUSIONS

Neurologic complications of organ transplantation are commonly related to opportunistic infection or neurotoxicity of immunosuppressive agents, requiring careful titration of immunosuppression. Timely diagnosis of CNS infection or other causes of neurologic dysfunction may significantly improve recovery and outcome in these patients.

Update on management and treatment of short gut

Management of patients with short-bowel syndrome represents a formidable challenge. Aggressive treatment including nutritional care and anticipation of potential complications and rapid treatment of complications enhance outcome. New therapies offer the promise of significantly improving morbidity and mortality. Intestinal transplant is appropriate for infants who would otherwise die from liver disease, recurrent sepsis, or lack of venous access.

Late graft loss and long-term outcome after isolated intestinal transplantation in children

BACKGROUND/PURPOSE

The aim of this study was to determine causes of late graft loss and long-term outcome after isolated intestinal transplantation in children at a single center.

METHODS

All children who underwent primary isolated intestinal transplantation at our center with a minimum follow-up of 1 year were the subject of this retrospective study.

RESULTS

Twenty-eight children underwent primary isolated intestinal transplantation. Median graft survival was 705 days (range, 0 to 2,630 days) and median patient survival was 1,006 days (range, 0 to 2,630 days). There were 6 deaths and 15 graft losses (including the 6 nonsurvivors). Seven of the losses occurred 6 or more months after transplant. Of these, 2 losses occurred because of death of the recipients of sepsis; both recipients had functioning grafts. The 5 remaining late graft losses occurred because of acute rejection in 2 patients, chronic rejection in 2 (1 with concomitant acute rejection) and a diffuse stricturing process without the histologic hallmarks of chronic rejection in the fifth. All late survivors with intact grafts are off total parenteral nutrition (TPN).

CONCLUSIONS

Late graft loss remains a concern in a small percentage of patients after isolated intestinal transplantation. Nutritional autonomy from TPN is possible in the majority of these children after transplantation.

Pediatric intestinal transplantation: the resected allograft

We reviewed the clinical and pathologic finding of 22 resected allografts from 19 of the 83 children who underwent a variety of small intestinal transplant procedures in the years 1990-2000 at the Children's Hospital of Pittsburgh. Resections were compared with prior mucosal biopsies because resections allow for evaluation of the entire bowel thickness, including the feeding vessels, and obviate the problems of limited sampling. Partial resections that were done soon after the transplant, or soon after additional surgery, were for surgical problems such as leaks, adhesions, and volvulus. None had biopsy features suggestive of rejection or infection. Partial resections done late (6 months or more) after transplantation were more likely to be related to allograft immune biology; two had a sclerosing peritonitis that was confined to the allograft, and one had an obstructing carcinoma arising in the allograft mucosa. One patient had a localized stricture, demonstrated to be due to graft vascular disease at partial resection, and this patient went on to have the allograft removed a year later for chronic rejection. Early complete allograft enterectomies were for refractory acute cellular rejection, 1-2 months following transplant. One was removed for pancreatitis and liver failure from operative complications. Late allograft enterectomies were generally for chronic rejection, some with residual acute rejection, but there were also a number of patients who had multiple superimposed conditions such as cytomegalovirus, Epstein-Barr virus, and post-transplant lymphoproliferative disorder in various combinations. One had idiopathic scarring and developed an adynamic bowel that remains unexplained. Examination of the resected specimens allows for dissection of the multiple contributions to graft failure, especially the vascular disease that can rarely be seen on mucosal biopsy. An unexpected finding was the impressive hypertrophy of neural elements, nerves, and ganglion cells in many of the patients, the significance of which requires further investigation.

Recent advances and future prospects in intestinal and multi-visceral transplantation

From an experimental procedure, intestinal transplantation (ITx) has evolved over the last 10 yr into a treatment option for patients suffering from short bowel syndrome and who develop life-threatening complications from total parenteral nutrition (TPN) (e.g. liver dysfunction, line sepsis, shortage of venous access, etc.). One-year survival rates are approximately 70% and thus similar to lung Tx. However, the intestine remains the most challenging abdominal organ to transplant. This is because of the severe immune response (mostly rejection) that is produced, and therefore the need for profound immunosuppression with its attendant complications (sepsis, lymphoma, direct drug toxicity). Unlike other organs, graft loss as a result of acute rejection can occur late after transplantation (more than 1 yr post-transplant). With regard to the actual immunosuppressive regimens, considerable experience in patient management is required to optimize outcome of those complex transplants, which are permanently at risk of rejection and infection. ITx remains an unfinished product, and the application of ITx to patients doing well on TPN warrants further research in the understanding of the rejection process, in the development of less toxic and more efficient immunosuppressive protocols, and in the development of immunomodulatory strategies, to better control rejection and thereby reduce the need for immunosuppression.

Treatment of short-bowel syndrome

The present article reviews the current literature on the role of diet and other trophic factors in the treatment of short-bowel syndrome. Results using glutamine, growth hormone and glucagon-like peptide 2 are reviewed. Although experimental animal data would suggest that various growth factors are of benefit in the treatment of short-bowel syndrome, only a few clinical studies have made the same claim.

Effects of endothelin receptor antagonist TAK-044 on small bowel autograft from a controlled non-heart-beating donor model

BACKGROUND

This study investigated the possibility of pharmacologic protection using an endothelin (ET) receptor antagonist, TAK-044 (TAK), for small bowel autograft in a canine controlled non-heart-beating donor (NHBD) model.

METHODS

Sixteen adult mongrel dogs were allocated into 2 groups. TAK (3 mg/kg) (n = 8) was administered intravenously 30 minutes before ischemia and 30 minutes before graft reperfusion. Vehicle was administered in the control (n = 8). The superior mesenteric artery and vein were clamped for 90 minutes to induce warm ischemia as a controlled NHBD model. The entire small bowel then was harvested and stored in 4 degrees C University of Wisconsin solution for 4 hours. The autograft was transplanted orthotopically. Mucosal tissue blood flow, intramucosal pH (pHi), and serum ET-1 levels were measured. Specimens were evaluated histopathologically and ET-1 immunohistochemically.

RESULTS

TAK provided significantly higher tissue blood flow and pHi at 3 and 6 hours after graft reperfusion and significantly higher serum ET-1 levels at 1 hour after graft reperfusion as compared with the control group. TAK had histopathologic tissue damage graded as superficial, did not reach to grade 5 on Park's grading as in controls, and provided less intense immunoreactivity for ET-1 immunohistochemical staining.

CONCLUSIONS

TAK may have clinical application in small bowel transplantation from controlled NHBD or conditions related to ischemia-reperfusion (I/R) injury.

Modified temporary end-to-side portocaval shunt in liver and small bowel transplantation

Piggyback orthotopic liver transplantation (LTx) has permitted the elimination of extra-corporeal venovenous bypass. In some instances, an internal temporary portocaval shunt has to be constructed in order to prevent hemodynamic instability. We describe a technique in which a donor iliac vein graft is used to bridge the distance between the portal vein and vena cava in cases where a direct shunt cannot be constructed. This technique can be applied to liver Tx as well as to liver and small bowel Tx.

Donor and recipient pretransplant conditioning with nonlethal radiation and antilymphocyte serum improves the graft survival in a rat small bowel transplant model

BACKGROUND

Lymphoid tissue within the intestinal graft require immunomodulatory strategies to prevent graft versus host disease (GVHD) after transplant. Herein, we evaluate the potential advantage of donor-specific bone marrow infusions in donor and or recipient preconditioned with total body irradiation and or antilymphocyte serum (ALS) on the incidence of GVHD and rejection after small bowel transplantation.

METHODS

Heterotopic SBTx was performed from DA to Lewis rats and distributed in nine groups: control group G0 (n=4) and G1 (n=6) without irradiation; recipients in G2 (n=4) were given 400 rd although in groups 3 (n=5), G4 (n=6), G6 (n=5), G7 (n=5), and G8 (n=6) with 250 rd. Donors in G5 (n=4) and G6 were given 250 rd of total body irradiation 2 hours before intestinal retrieval. Donors and recipients in G7 and donors in G8 additionally received ALS (day -5). G1, 2, 3, 5, 6, 7, and 8 were infused with UDBM and G4 with the same amount of TCDBM. Animals received tacrolimus for 15 days and accessed for rejection, GVHD and for chimerism analysis.

RESULTS

High mortality due to GVHD was observed in G2, 3, and 4, and correlated with high levels of donor T cells in recipients blood. G0 and G1 showed early acute rejection with progression toward chronic rejection, in contrast to the preconditioned groups. High and low doses of total body irradiation resulted in allogeneic and in a mixed chimerism, respectively. Decrease in donor chimeric cells after 11 weeks in preconditioned groups was correlated with severe allograft rejection.

CONCLUSION

Donor preconditioning with 250 rd and or ALS combined with recipient preconditioning and donor-specific bone marrow infusions prevented GVHD and resulted in a transient mixed chimerism with inhibition of allograft rejection after small bowel transplantation.

Clinical intestinal transplantation: a decade of experience at a single center

OBJECTIVE

To assess the long-term efficacy of intestinal transplantation under tacrolimus-based immunosuppression and the therapeutic benefit of newly developed adjunct immunosuppressants and management strategies.

SUMMARY BACKGROUND DATA

With the advent of tacrolimus in 1990, transplantation of the intestine began to emerge as therapy for intestinal failure. However, a high risk of rejection, with the consequent need for acute and chronic high-dose immunosuppression, has inhibited its widespread application.

METHODS

During an 11-year period, divided into two segments by a 1-year moratorium in 1994, 155 patients received 165 intestinal allografts under immunosuppression based on tacrolimus and prednisone: 65 intestine alone, 75 liver and intestine, and 25 multivisceral. For the transplantations since the moratorium (n = 99), an adjunct immunosuppressant (cyclophosphamide or daclizumab) was used for 74 transplantations, adjunct donor bone marrow was given in 39, and the intestine of 11 allografts was irradiated with a single dose of 750 cGy.

RESULTS

The actuarial survival rate for the total population was 75% at 1 year, 54% at 5 years, and 42% at 10 years. Recipients of liver plus intestine had the best long-term prognosis and the lowest risk of graft loss from rejection (P =.001). Since 1994, survival rates have improved. Techniques for early detection of Epstein-Barr and cytomegaloviral infections, bone marrow augmentation, the adjunct use of the interleukin-2 antagonist daclizumab, and most recently allograft irradiation may have contributed to the better results.

CONCLUSION

The survival rates after intestinal transplantation have cumulatively improved during the past decade. With the management strategies currently under evaluation, intestinal transplant procedures have the potential to become the standard of care for patients with end-stage intestinal failure.

Inhibition of nitric oxide synthase induces intestinal mucosal damage and increases mortality in rats treated by FK506

INTRODUCTION

Despite the beneficial immunosuppressive effects of FK506 during small intestine transplantation, FK506 appears to have direct toxic effects on the intestine. The mechanisms of FK506-induced intestinal damage is unclear, and whether nitric oxide (NO) is involved in the mechanism has not been well defined. This study was designed to evaluate the effects of NG-Nitro-L-arginine methyl ester (L-NAME), an inhibitor of NO synthase, on small intestinal damage in rats treated with FK506.

MATERIALS AND METHODS

Wistar rats weighing 240-260 g, aged 11 weeks, were administered FK506 (5 mg/kg/day i.m) and/or L-NAME (5 mg/dl in drinking water) for 10 days. Body weight gain, diarrhoea and mortality were observed during experiment. At the end of experiment, the intestinal specimens were excised for histological evaluation. In addition, the effects of L-aginine treatment (1 g/dl in drinking water) were evaluated in this study.

RESULTS

L-NAME administration time-dependently induced diarrhoea and high mortality in the rats treated with FK506. At the end of 10 days treatment, 7 of 12 rats (58.3%) suffered from diarrhoea and 5 of 12 rats (41.7%) died in the FK506 + L-NAME group (vs. FK506 group, p = 0.05). A significant loss of body weight was also found in the rats treated with FK506 + L-NAME (-52.2 +/- 28.8 g, in FK506 + L-NAME group vs. -14.3 +/- 8.7 g in FK506 group, p = 0.001). In parallel with the severe diarrhoea and high mortality, the loss of villi, hemorrhage and necrosis (grade 5 of pathological damage) was seen in the small intestinal mucosa of rats treated with FK506 + L-NAME. L-arginine treatment in part prevented diarrhoea, mortality and pathological damage of small intestinal mucosa induced by L-NAME.

CONCLUSIONS

Inhibition of NOS induces intestinal mucosal damage and increases mortality in rats treated with FK506. L-arginine treatment can in part prevent the injury induced L-NAME. The present study suggests that NO, as an important protective factor, may be involved in the FK506-induced intestinal damage.

Small bowel tissue engineering using small intestinal submucosa as a scaffold

BACKGROUND

Small intestinal submucosa (SIS) is an extracellular matrix used in tissue engineering studies to create de novo abdominal wall, urinary bladder, tendons, blood vessels, and dura mater. The purpose of this study is to evaluate the feasibility of using SIS as a scaffold for small bowel regeneration in an in situ xenograft model.

MATERIALS AND METHODS

Twenty-three dogs had a partial defect created on the small bowel wall which was repaired with a SIS patch. Four dogs underwent small bowel resection with placement of an interposed tube of SIS. The animals were followed 2 weeks to 1 year.

RESULTS

Three of the 23 dogs with SIS placed as a patch died shortly after surgery due to leakage from the site. The other 20 dogs survived up to time of elective necropsy with no evidence of intestinal dysfunction. At necropsy, the bowel circumference in the patched area had no stenosis. Histological evaluation showed the presence of a mucosal epithelial layer, varying amount of smooth muscle, sheets of collagen, and a serosal covering. Architecturally, the layers were not well organized in the submucosal region. An abundance of inflammatory cells was present in the early postoperative period but receded with time. All 4 dogs with a tubular segment of SIS interposed had significant problems. One had partial obstruction at 1 month, and 3 died in the early postoperative period due to leakage.

CONCLUSIONS

This preliminary study suggests that SIS patches can be used for small bowel regeneration. Tubular segmental replacement is not feasible at this time.

Identifying the patient at risk for post-transplant lymphoproliferative disorder

Post-transplant lymphoproliferative disorders (PTLD) are a recognized complication of the immunosuppression required to prevent allograft rejection, occurring in 1-20% of recipients of solid organ transplants. Several factors greatly increase the risk of developing PTLD early post-transplant in any individual recipient. Epstein-Barr virus (EBV) infection is critical in the pathogenesis of the majority of these cases. Pre-transplant EBV seronegativity increases the incidence of PTLD 10- to 75-fold over that of EBV-seropositive recipients. Other risk factors include very young recipient age, cytomegalovirus infection or mismatching (donor positive-recipient negative), aggressive immunosuppression with conventional biologic agents, and the type of organ transplanted. In contrast, the risk of developing PTLD late in the post-transplant course does not appear to be influenced by the type of immunosuppressive agents employed, but rather by the duration of any immunosuppression. The role of EBV in late PTLD is also less certain, as a greater proportion of lesions are not associated with evidence of EBV infection. As the understanding of these risk factors has expanded, opportunities exist to target those populations at highest risk for the development of PTLD for aggressive monitoring and pre-emptive or prophylactic therapy. It is hoped that implementation of such strategies will render early PTLD a preventable complication of transplantation.

Intestinal transplantation for children with short bowel syndrome

Intestinal transplantation has emerged as a feasible alternative in the treatment of children with short gut syndrome. The challenges in the management of these patients include maintaining a tight balance between the degree of immunosuppression necessary to prevent graft-versus-host disease and rejection. At the same time, this amount of immunosuppression is associated with a high risk for lymphoproliferative disorders and intestinal-derived sepsis. Current 3-year patient and graft survival rates are 55% and 50%, respectively. The indications, morbidity, and timing for referral are discussed.

Microchimerism, GVHD, and tolerance in solid organ transplantation

The phenomenon of microchimerism and its relationship to long-term graft tolerance is an area of active study. The ability to establish a tolerant state has been enhanced with current immunosuppressive drugs and emerging therapies such as donor HPC infusions. An undesirable outcome of host-donor WBC interaction is GVHD. GVHD is a rare complication reported most frequently in liver transplantation. Two cases of GVHD reported in recipients of organs from donors homozygous for a shared HLA haplotype would support a policy of avoiding the use of these donors. TA-GVHD is very rare in solid organ transplant recipients, with only four published cases; only two had convincing supportive evidence and one of these had an underlying hematologic abnormality. These few cases do not support a policy of routine irradiation of cellular blood components for all solid organ transplant recipients. The use of donor HPC infusions to enhance chimerism and graft tolerance has increased the number of GVHD cases observed (usually mild) and decreased the severity and number of rejection episodes. The long-term effects of donor HPC infusions on graft survival is under investigation.

Segmental living related small bowel transplantation in adults

The advent of small bowel transplantation has provided selected patients with chronic intestinal irreversible failure with a physiologic alternative to total parenteral nutrition. Recently a standardized technique for living related small bowel transplantation (LR-SBTx) has been developed. Three patients with short bowel syndrome underwent LR-SBTx at our institution. All donors were ABO compatible with a good human leukocyte antigen match. A segment of 180 to 200 cm of ileum was harvested and transplanted with its vascular pedicle constituted by the ileocolic artery and vein. The grafts were transplanted with a short cold and warm ischemia time. The immunosuppression regimen consisted of oral FK-506, prednisone, and intravenous induction with atgam. Serial biopsies of the intestinal grafts were performed to evaluate rejection or viral infections. The postoperative course was uneventful for all donors. All of the recipients are currently alive and well. Two of three patients are off total parenteral nutrition and tolerating an oral diet with no limitations on daily activity. In the third patient, the graft was removed 6 weeks after transplantation. At the time of enterectomy, no technical or immunologic complications were documented. Absorption tests for D-xylose and fecal fat studies were performed showing functional adaptation of the segmental graft. All biopsies were negative for acute rejection. A well-matched segmental ileal graft from a living donor can provide complete rehabilitation for patients with short bowel syndrome. Our initial experience suggests that the risk of acute rejection and infection is greatly reduced compared to cadaveric bowel transplantation. Further clinical application of this procedure is warranted.

Intestinal transplantation for the treatment of desmoid tumors associated with familial adenomatous polyposis

BACKGROUND

Desmoid tumors associated with familial adenomatous polyposis (FAP) are locally invasive. Often occurring in the mesentery of the intestine, they sometimes recur after resection. Complications can include intestinal failure and dependence on parenteral nutrition. We describe 9 patients who underwent intestinal transplantation for the treatment of desmoid tumors associated with FAP.

METHODS

Records of patients undergoing intestinal transplantation for desmoid tumors at 2 transplant centers were reviewed for patient age, sex, type of graft, procedure date, tumor site, desmoid complications, medications, extracolonic manifestations, status at follow-up, and length of survival.

RESULTS

Nine patients with FAP and intestinal failure caused by desmoid tumors were treated with isolated intestinal (n = 6), multivisceral (n = 2), or combined liver-intestinal transplantation (n = 1). Desmoid tumors recurred in the abdominal walls of 2 patients. Two patients died: one as a result of sepsis, the other because of a rupture of a mycotic aneurysm of the aortic anastomosis. One graft lost to severe rejection was replaced with a second intestinal graft. Eleven to 53 months after transplantation, 7 patients were alive, well, independent of parenteral treatment, and leading apparently normal lifestyles.

CONCLUSIONS

Transplantation of the intestine alone or as part of a multivisceral transplantation may help rescue otherwise untreatable patients with complicated desmoid tumors.

Progressive functional adaptation of segmental bowel graft from living related donor

We report a patient with short gut syndrome successfully treated with living related bowel transplantation. A 27-year-old Caucasian man was referred after traumatic loss of almost the entire bowel from the third portion of duodenum to the sigmoid colon. His HLA-identical sister volunteered as a donor. A 200-cm segment of ileum was successfully transplanted under tacrolimus-based immunosuppression. The posttransplant course was uneventful, without rejection or infectious complication. Total parenteral nutrition was discontinued 1 week posttransplant. At 6 months the patient had returned to his preinjury weight. Water and D-xylose absorption as well as fecal fat studies were markedly abnormal 1 month posttransplant but normalized by 6 months. The donor recovery was uneventful. A well-matched segmental ileal graft from living donor can provide complete rehabilitation for patients with short gut syndrome. We documented a progressive functional adaptation of the ileal graft, resulting in normal absorption by 5 months posttransplantation.

Role of CD4+ and CD8+ T cells in early and late acute rejection of small bowel allograft

BACKGROUND/PURPOSE

Results of small bowel transplantation remain unsatisfactory because of severe immune rejection. The current study aims to elucidate the role of activation of CD4+ and CD8+ T cells in early and late acute rejection of small bowel allograft and, hence, provide the immunologic basis for developing new therapeutic strategies.

METHODS

We used an MHC fully mismatched (DA to Lewis) heterotopic rat small bowel transplant model and a unique FK506-based immunosuppressive regimen, which suppresses early acute rejection but does not prevent late acute rejection. Flow cytometric analysis was used to quantitate the number of activated CD4+ and CD8+ T cells in graft and host mesenteric lymph nodes.

RESULTS

The survival (mean +/- SD) of intestinal allograft was significantly prolonged, from 6.6 +/- 0.84 days for the untreated group to 40.7 +/- 14.1 days for the FK506-treated group. Activation of CD4+ cells was suppressed significantly in the FK506-treated group on postoperative day 7 compared with the untreated group (29.4% +/- 3.55% v 52.83% +/- 11.9%; P <.01). Activation of CD8+ cells was similarly suppressed (31.5 +/- 10.34% v 48.53 +/- 14.34%; P <.05). Interestingly, at late acute rejection, activated CD4+ and CD8+ T cells remained at almost the same low levels as those on postoperative day 7 in the FK506-treated group. The spleen to body weight ratio was significantly increased in the untreated group (0.53 +/- 0.07), and slightly increased in the FK treated group (0.27 +/- 0.07, on postoperative day 7; 0.24 +/- 0.07 at late acute rejection) compared with the syngeneic group (0.18 +/- 0.02).

CONCLUSION

The activation of CD4+ and CD8+ T cells was suppressed effectively by early potent immunosuppressive treatment resulting in prolonged survival of intestinal allograft. At late acute rejection, the CD4+ and CD8+ T cells remained at low-level activation status, in contrast to the surge of CD4+ and CD8+ activation during early acute rejection. This suggests that persistent T cell activation even at low level is sufficient to cause the late acute rejection eventually. A therapeutic strategy targeting these cells is needed for long-term engraftment.

Analysis of patients with longitudinal intestinal lengthening procedure referred for intestinal transplantation

BACKGROUND/PURPOSE

Longitudinal intestinal lengthening procedures (LILP) in patients with short gut syndrome (SGS) enhances small intestinal peristalsis and decreases bacterial overgrowth without reducing absorptive surface. Therefore, patients theoretically may be easily weaned off TPN. The aim of this study was to evaluate the impact of failed LILP in SGS patients referred for intestinal transplantation.

METHODS

Twenty-seven (11%) of 230 children with SGS and total parenteral nutrition (TPN) dependency evaluated for intestinal transplantation at our institution had undergone LILP. This was performed at a mean age of 1.7 years (range, 1 day to 14.7 years); the mean age at the time of evaluation was 3.3 years (range, 0.4 to 17 years). Two patients underwent LILP immediately after birth. The principle diagnoses producing SGS were gastroschisis (n = 8), intestinal atresia (n = 11), neonatal volvulus (n = 7) and necrotizing enterocolitis (n = 1). Before LILP, the mean length of intestine was 32 cm (range, 8 to 70 cm). Fifteen (56%) patients had jaundice at the time of evaluation.

RESULTS

All but one child were considered candidates for intestinal transplantation. The mean intestinal length achieved after LILP was 48 cm (range, 16 to 100). The mean follow-up from the date of LILP was 876 days (range, 109 to 4,109 days). After LILP, only 9 (33%) patients increased their caloric intake through the enteral route by > or =50%, and only 1 patient could be weaned off TPN. In the patients with liver dysfunction at the time of LILP, none recovered. Most of the patients had multiple episodes of sepsis after LILP. Fourteen (52%) of 27 patients underwent intestinal transplantation, 7 combined with a liver allograft because of TPN-induced end-stage liver disease. Six of the transplanted patients are alive and TPN free. Of the remaining 13 (48%) nontransplanted patients, 9 patients died. The main cause of death was TPN-induced liver failure. Three patients are on partial TPN, and only 1 patient was weaned off TPN. The presence of an ileocecal valve did not impact on outcome. Surprisingly, patients with > or =50% of colon at the time of LILP had poorer survival than those with less. Twelve (44%) of 27 patients had surgical complications, and in both patients with LILP performed in the neonatal period it failed immediately with acute complications. There were no differences in patient survival rate for patients with SGS without LILP (n = 203) and those with LILP (n = 27).

CONCLUSION

Based on patients with unsuccessful LILP referred for intestinal transplantation, we believe this procedure should be avoided in the neonatal period, in those patients with liver dysfunction, and when intestinal length is <50 cm.

The role of intestinal transplantation in the management of intestinal failure

Significantly reduced morbidity and mortality is needed before intestinal transplantation will be applicable in most patients with intestinal failure who are on long-term total parenteral nutrition (TPN). However, transplantation does play a role if TPN fails, with failure defined by Medicare as liver failure, frequent line sepsis, major central vein thrombosis, or recurrent dehydration. Of these complications, the relationship between liver failure and subsequent death in high-risk subgroups of long-term TPN patients has been shown clearly. Patients with less than 100 cm of postduodenal small bowel, an end-jejunostomy, no ileocecal valve or cecum, or persistently elevated liver function levels are at high risk for end-stage liver disease (ESLD). Early referral to experienced centers is suggested in these circumstances. High-risk patients may also take part in clinical trials of promising therapies to increase intestinal adaptation and prevent liver failure. Living donors should be considered for transplant candidates to minimize waiting time and optimize HLA matching. ESLD patients need a liver-intestine transplant. Because their waiting-list mortality is very high, their status on the liver waiting list should be elevated if possible. High incidence of early death from sepsis is reported after intestinal transplant, even at experienced centers. Aggressive measures should be taken if uncontrolled sepsis occurs, including discontinuing immunosuppression and removing the graft. Further research is needed in intestinal immunology and in development of strategies to decrease the need for aggressive immunosuppression in these transplant recipients. The ultimate role of intestinal transplantation will be determined by its capacity to show superiority, both in effectiveness and safety, to long-term TPN.