The extracellular matrix: an early target of preservation/reperfusion injury and acute rejection after small bowel transplantation

Regulation of the Immune System by Laminins

Laminins are trimeric proteins that are major components of the basement membranes that separate endothelia and epithelia from the underlying tissue. Sixteen laminin isoforms have been described, each with distinct tissue expression patterns and functions. While laminins have a critical structural role, recent evidence also indicates that they also impact the migration and functions of immune cells. Laminins are differentially expressed upon immunity or tolerance and orientate the immune response. This review will summarize the structure of laminins, the modulation of their expression, and their interactions with the immune system. Finally, the role of the laminins in autoimmune diseases and transplantation will be discussed.

The role of biologicals in intestinal transplantation

PURPOSE OF REVIEW

This article reviews the role of biologicals in intestinal transplantation.

RECENT FINDINGS

Several biologicals have been used in intestinal and multivisceral transplantation for various indications, such as induction therapy, prevention and treatment of antibody-mediated rejection, desensitization, anti-inflammatory treatment, as well as treatment of Epstein-Barr virus-associated posttransplant lymphoproliferative disease. Particularly, the administration of biologicals in induction therapy such as T-cell depleting antibodies and interleukin-2 receptor antagonists have significantly contributed to the great improvement of patient and allograft outcome. Novel biologicals, such as B-cell, plasma-cell, and complement-directed agents have been successfully applied to treat antibody and complement-driven alloimmune processes to stabilize long-term outcome. Several other inflammatory allotransplant conditions have been addressed with anti-TNF-α antibodies, such as infliximab.

SUMMARY

Biologicals have contributed significantly to the recent success of intestinal transplantation. Novel developments in this field are supposed to aid in addressing various urgent needs in intestinal transplantation, such as preimmunization, antibody and complement-induced graft injury, as well as pathologies originating from innate immune responses.

Mucosal changes induced by ischemia-reperfusion injury in a jejunal loop transplanted in oropharynx

Tissues exposed to ischemia and reperfusion develop an inflammatory response. We investigate the morphological and immunological changes occurring in the mucosa of a jejunal loop transplanted in the oropharynx of a man undergoing circular pharyngolaryngectomy. Jejunal biopsies were collected during the transplantation procedures (cold and warm ischemia, reperfusion), during the 7 post-operative days through an exteriorized jejunal segment for flap monitoring, and 45 days after transplantation through an upper endoscopy. Matrix metalloproteinase (MMP)-3 and MMP-12 increase was accompanied by a parallel rise in apoptotic enterocytes, and by a concomitant reduction of surface area to volume ratio and enterocyte height. Goblet cell hyperplasia is coupled with Paneth cell disappearance at the crypt base. CD8-positive intraepithelial lymphocytes initially decrease, then they increase in accordance with the peak of enterocyte apoptosis. We identified alterations in lymphocyte infiltration, mucosal architecture and epithelial cell turnover, which may give a window to mechanisms of small bowel ischemia-reperfusion in humans.

Tumor necrosis factor alpha inhibitors as immunomodulatory antirejection agents after intestinal transplantation

We reported the successful administration of infliximab for late-onset OKT3-resistant rejection in two patients, who presented persistent ulcerative inflammation of the ileal graft after intestinal transplantation (ITX). Based on this experience, the present study demonstrated our long-term experience with infliximab for different types of rejection-related and inflammatory allograft alterations. Infliximab administration (5 mg/kg body weight (BW)) was initiated at a mean of 18.2 ± 14.1 months after transplantation. The number of administrations per patient averaged 8.4 ± 6.7. Repeat dosing was timed according to clinical signs and graft histology in addition to serum-levels of tumor necrosis factor alpha (TNFα), lipopolysaccharide binding protein (LBP) and C-reactive protein (CRP). Infliximab was successful in the following patients: patients with late-onset OKT3- and steroid-refractory rejection who presented persistent ulcerative alterations of the ileal graft (n = 5), patients with ulcerative ileitis/anastomositis, who did not show typical histological rejection signs (n = 2), and one patient with early-onset OKT3-resistant rejection. Infliximab was not successful in one patient with early-onset OKT3-resistant rejection that was accompanied by treatment-refractory humoral rejection. In conclusion, infliximab can expand therapeutic options for late-onset OKT3- and steroid-refractory rejection and chronic inflammatory graft alterations in intestinal allograft recipients.

Mechanism of cellular rejection in transplantation

The explosion of new discoveries in the field of immunology has provided new insights into mechanisms that promote an immune response directed against a transplanted organ. Central to the allograft response are T lymphocytes. This review summarizes the current literature on allorecognition, costimulation, memory T cells, T cell migration, and their role in both acute and chronic graft destruction. An in depth understanding of the cellular mechanisms that result in both acute and chronic allograft rejection will provide new strategies and targeted therapeutics capable of inducing long-lasting, allograft-specific tolerance.

Protective effect of NAC preconditioning against ischemia-reperfusion injury in piglet small bowel transplantation: effects on plasma TNF, IL-8, hyaluronic acid, and NO

BACKGROUND

Ischemia-reperfusion (I/R) injury is one of the main factors affecting the function and structure of small bowel transplantation (SBT), by generation of proinflammatory mediators such as reactive oxygen species, reactive nitrogen species, cytokines, and endotoxin. Experimental data have demonstrated that N-acetylcysteine (NAC) attenuates intestinal I/R injury. The objective of this study was to determine the effect of NAC preconditioning on the SBT-I/R induced inflammatory cascade, with particular focus on TNF, IL-8, hyaluronic acid, and NO.

METHODS

Fifteen domestic pigs were used as donors. Fifteen recipient animals were randomly assigned into two groups. Group 1: SBTx (n=7) served as controls and Group 2: SBTx (n=8) served as the experimental group (NAC administration).

RESULTS

NAC administration at a continuous 4 h intravenous bolus dose of 200 mg/kg of body weight, starting before initiation of bowel transplantation, resulted in statistically significant (P<0.05) higher plasma levels of NO, and lower plasma levels of hyaluronic acid, TNF-α, IL-8, and LDH compared with those of the control group, at the 360 min time point.

CONCLUSIONS

NAC confers a protective role in small bowel transplantation associated, partly, with NO generation and hyaluronic acid, TNF-α and IL-8 amelioration.

Ischemia/reperfusion injury in kidney transplantation: mechanisms and prevention

Ischemia has been an inevitable event accompanying kidney transplantation. Ischemic changes start with brain death, which is associated with severe hemodynamic disturbances: increasing intracranial pressure results in bradycardia and decreased cardiac output; the Cushing reflex causes tachycardia and increased blood pressure; and after a short period of stabilization, systemic vascular resistance declines with hypotension leading to cardiac arrest. Free radical-mediated injury releases proinflammatory cytokines and activates innate immunity. It has been suggested that all of these changes-the early innate response and the ischemic tissue damage-play roles in the development of adaptive responses, which in turn may lead to an acute font of kidney rejection. Hypothermic kidney storage of various durations before transplantation add to ischemic tissue damage. The final stage of ischemic injury occurs during reperfusion. Reperfusion injury, the effector phase of ischemic injury, develops hours or days after the initial insult. Repair and regeneration processes occur together with cellular apoptosis, autophagy, and necrosis; the fate of the organ depends on whether cell death or regeneration prevails. The whole process has been described as the ischemia-reperfusion (I-R) injury. It has a profound influence on not only the early but also the late function of a transplanted kidney. Prevention of I-R injury should be started before organ recovery by donor pretreatment. The organ shortage has become one of the most important factors limiting extension of deceased donor kidney transplantation worldwide. It has caused increasing use of suboptimal deceased donors (high risk, extended criteria [ECD], marginal donors) and uncontrolled non-heart-beating (NHBD) donors. Kidneys from such donors are exposed to much greater ischemic damage before recovery and show reduced chances for proper early as well as long-term function. Storage of kidneys, especially those recovered from ECD (or NHBD) donors, should use machine perfusion.

Biologics in the treatment of transplant rejection and ischemia/reperfusion injury: new applications for TNFalpha inhibitors?

Tumor necrosis factor (TNF)-alpha inhibitors have proven efficacy in various autoimmune diseases such as Crohn disease, rheumatoid arthritis, psoriasis, and ankylosing spondylitis. Indeed, some TNFalpha inhibitors have already been approved for the management of the inflammatory manifestations associated with Crohn disease and rheumatoid arthritis. These agents are increasingly used for treatment of corticosteroid-resistant graft-versus-host disease after bone marrow transplantation, and case reports have documented their efficacy in treating corticosteroid- and muromonab-resistant rejection after intestinal transplantation. Thus, the potential role of TNFalpha inhibitors in transplantation of other vascularized solid organs is worthy of investigation. Experimental evidence indicates that TNFalpha plays a key role in mediating ischemia/reperfusion (IR) injury after liver, kidney, intestine, heart, lung, and pancreas transplantation. TNFalpha was also identified as a marker cytokine during organ rejection. Single-center studies evaluating the role of TNFalpha inhibitors in kidney transplantation have been initiated but the results are not yet available. TNFalpha is known to be a contributing factor in kidney allograft rejection, and may have value in predicting the onset of steroid-resistant acute rejection after liver transplantation. Experimental and preliminary clinical data have shown that circulating levels of TNFalpha are increased during cardiac graft rejection, and indicate that TNFalpha plays a role in the pathogenesis of acute cardiac allograft rejection. Anti-TNFalpha therapy was shown to prolong cardiac allograft survival when used alone or in combination with other drugs. TNFalpha genotype has been strongly associated with mortality in humans due to acute cell-mediated heart transplant rejection. In addition, there is evidence for a genetic predisposition toward acute rejection after kidney and simultaneous kidney-pancreas transplantation. TNFalpha inhibition has been used successfully as part of an induction therapy for pancreatic islet cell transplantation. Apart from IR injury and acute rejection after lung transplantation, TNFalpha was also found to be involved in the pathoimmunology of obliterative bronchiolitis. In conclusion, a substantial body of experimental evidence and preliminary clinical data suggest that TNFalpha inhibitors may play an important role in solid-organ transplantation, both in the amelioration of IR injury and in the treatment and prevention of acute rejection. Pharmacodynamic monitoring and pharmacogenetic screening may help to identify patients most likely to benefit from TNFalpha blockade. Randomized controlled trials in patients undergoing solid-organ transplantation are needed to further elucidate the clinical value of TNFalpha inhibition.

Regulation of fibroblasts by activated and non-activated immune cells

BACKGROUND

Rejection of transplanted tissue is characterized by cell infiltration and interstitial edema. Graft fibroblasts and fibroblast products are partly involved in the regulation of both these phenomena. Knowledge about the mechanisms behind fibroblast activation may lead to new strategies to prevent rejection. This study investigated whether cells of the immune system have the capacity to regulate fibroblast activation.

METHODS

Fibroblasts isolated from rejecting heart transplants or from normal heart tissue were cultured in the presence of supernatants of stimulated or non-stimulated immune cells. The immune cells were challenged either in vitro (incubation with phytohemagglutinin) or in vivo (organ transplantation). Fibroblast proliferation and hyaluronan production were measured.

RESULTS

Normal, sub-confluent heart fibroblasts showed an increased proliferation rate in the presence of supernatants of activated immunocompetent cells, irrespective of if these cells had been stimulated in vitro or in vivo. As expected, proliferation rate and hyaluronan production were upregulated in fibroblasts isolated from rejecting tissue. However, supernatants of biopsy specimens obtained from non-rejecting organs (syngeneic transplants or normal hearts) had an inhibitory effect on the growth rate of confluent fibroblasts isolated from rejecting tissue.

CONCLUSIONS

We conclude that graft-infiltrating cells and immune cells activated in vitro have the capacity to stimulate fibroblasts, most probably as a result of the production and secretion of fibroblast-stimulating factors.

Assessment of serum matrix metalloproteinases MMP-2 and MMP-9 after human liver transplantation: increased serum MMP-9 level in acute rejection

BACKGROUND

Alterations in synthesis and breakdown of extracellular matrix components play a role in acute rejection after orthotopic liver transplantation (OLT). Matrix metalloproteinases (MMPs) are capable of degrading basement membranes and are involved in the process of tissue remodelling in inflammation and liver fibrosis.

METHODS

We examined MMP-2 and MMP-9 in serum of 33 patients before and during 1 year after OLT, in 60 controls as well as in some specimens of cirrhotic liver and control liver tissue.

RESULTS

Serum MMP-2 levels before OLT were significantly higher compared with controls and decreased approximately 50% after OLT. Also, the MMP-2 content of cirrhotic liver specimens was significantly higher compared with normal liver. MMP-9 in serum and liver tissue of patients were similar to controls, but serum levels showed a peak at 1 week after OLT. At this time-point, total and active/inhibitor-complexed MMP-9 was significantly higher in patients with rejection (n=13) compared with those without rejection (n=20). The relative amount of MMP-9 in the active/inhibitor-complexed form did not differ between each group over time. Immunohistochemical staining at 1 week after OLT showed increased numbers of MMP-9-positive inflammatory cells in the portal triads of patients with rejection.

CONCLUSIONS

Patients with acute allograft rejection have elevated serum levels of MMP-9 1 week after OLT, which was most likely derived from inflammatory cells. An increased MMP-2 serum level and liver tissue content was found in patients with cirrhosis, which decreased after OLT. These observations indicate active involvement of MMP-2 and -9 in end-stage liver disease and OLT.

Successful infliximab treatment of steroid and OKT3 refractory acute cellular rejection in two patients after intestinal transplantation

Acute rejection resistant to established immunosuppressive rescue protocols remains the most prominent risk factor after intestinal transplantation. In two patients presenting with steroid-resistant severe acute cellular rejection 9 months and 2 years after intestinal transplantation, complete resolution was not achieved despite 5 and 10 days of OKT3 treatment, respectively, and high-dose triple baseline immunosuppression with tacrolimus, rapamycin, and steroids. There was a dissociated course of rejection with persistent moderate to severe rejection in the terminal portion of the graft despite complete recovery from rejection in the proximal parts. Both patients were treated with four subsequent infusions of infliximab (3 mg/kg body weight), a chimeric anti-tumor necrosis factor-alpha antibody. There was an immediate response regarding macroscopic appearance, graft histology, and clinical symptoms. Both patients recovered. In conclusion, infliximab has proven to be an effective rescue therapy in a selected group of patients with steroid and OKT3 refractory severe acute rejection after intestinal transplantation.

IL-10 increases tissue injury after selective intestinal ischemia/reperfusion

OBJECTIVE This study focused on the effect of immunoregulatory cytokines on tissue injury after intestinal ischemia/reperfusion (IR). Furthermore, the role of nitric oxide, heme oxygenase-1 (HO-1) and the transcription factor NF-kappaB/Rel in the disease process was evaluated.SUMMARY BACKGROUND DATA Oxidative stress and inflammatory gene products contribute to ischemia/reperfusion injury (IRI). However, expression of stress proteins such as the inducible nitric oxide synthase (NOS-2) and HO-1 might also provide protection against IRI. METHODS IR was achieved in Lewis rats by selective clamping of the superior mesenteric artery. IL-2 or IL-10 was administered intravenously before reperfusion. Animals were killed 1 hour, 4 hours, and 24 hours after reperfusion. Tissue destruction was assessed by hyaluronic acid (HA) and aminoaspartate-transaminase (AST) serum levels, whereas reduction of glutathione (GSH) tissue levels was used as a marker for oxidative stress. Furthermore, the activation of NF-kappaB/Rel and the expression of NOS-2 and HO-1 were analyzed.RESULTS IR resulted in tissue destruction and significantly reduced GSH tissue levels in the intestines and liver. In addition, NF-kappaB/Rel activation and increased NOS-2 and HO-1 mRNA expression were detected in both organs after IR. IL-2 administration resulted in clinical improvement of the animals and was associated with increased NF-kappaB/Rel activation and enhanced NOS-2 and HO-1 mRNA expression. In contrast, IL-10 resulted in increased tissue destruction in both organs and sustained reduction of GSH levels in the intestines. Furthermore, IL-10 administration failed to enhance NF-kappaB/Rel activity, NOS-2 mRNA, or HO-1 mRNA expression after IR. CONCLUSION IL-10 resulted in increased tissue damage after intestinal IR. This detrimental effect of IL-10 might have been the result of reduced NOS-2 and HO-1 mRNA expression. In contrast, the beneficial effect of IL-2 might have relied on increased HO-1 expression and NOS-2 activity. These controversial effects of IL-2 and IL-10 might have been mediated through transcriptional regulation of NOS-2 and HO-1 gene expression.

Local antilaminin antibody treatment alters the rejection pattern of murine cardiac allografts: correlation between cellular infiltration and extracellular matrix

BACKGROUND

Emerging data place extracellular matrix (ECM) proteins as important elements in lymphocyte positioning and effector function in alloreactive responses. Using a non-vascularized model of allogeneic heart transplantation in Swiss mice, we have observed a correlation between the cellular infiltration and ECM deposition towards the interior of the graft during the kinetics of rejection.

METHODS

To confirm the importance of ECM during the rejection process in this model, we treated the transplanted animals with local injections of antilaminin monoclonal antibody and analyzed, by histology and immunohistochemistry, the grafts on day 15, which corresponds to the peak of cellular infiltration and ECM deposition.

RESULTS

The treatment with mAb antilaminin decreased the cellular infiltrate and ECM deposition within the grafts, as compared to controls. Moreover, we found a diminished IFN-gamma, TNF-alpha and IL-2 deposition in the transplant area, and a reduced co-localization of these cytokines with laminin. By contrast, the antilaminin treatment increased tenascin deposition, a molecule with immunosuppressive properties, and also caused an increase in apoptosis of the cellular infiltrate.

CONCLUSIONS

These data hallmark the importance of laminin, in distinct aspects concerning the events leading to allograft rejection, and also reinforce this molecule as a potential target for immune intervention in organ transplantation.

Modified techniques of heterotopic total small intestinal transplantation in rats

AIM

To establish a successful model of heterotopic total small intestinal transplantation (SIT) in rats in order to reduce the complications and increase the survival rate.

METHODS

A total of 196 Wistar rats underwent heterotopic SIT with microsurgical technique. Technical modifications included shortening fasting time and supplying energy before surgery, administering optimal volume of crystalloid fluid to the donor and recipient during surgical procedures, reducing mechanical and ischemic injuries to donor intestine, revascularizing small intestinal graft with a combination of conventional aorta to aorta anastomosis and a cuffed portal vein to left renal vein anastomosis which resulted in an acceptably short warm ischemic time, and also an adequate blood supply and drainage of the graft.

RESULTS

The average time for the donor surgery was 86 min +/- 20 min, the mean operative time for the recipient was 115 min +/-20 min and warm ischemia time was shortened to 40 min +/- 5 min. There was a shorter revascularizing time of the graft, the abdominal aorta (AA) to AA anastomosis being 21 min +/- 10 min, and the cuffed portal vein (PV) to the renal vein anastomosis being 5 min +/- 5 min. The one-week survival rate of 98 rats with SIT was 88.78% (87/98), without thrombosis and stenosis of anastomosis. The longest survival time of recipient rats was more than 389 days after SIT, the rats were maintaining normal weight, with perfect intestinal function and intact intestinal histology.

CONCLUSION

These modified techniques for SIT would remarkably reduce the complications and improve survival rate in rats, which provided a potentially more consistent and practical model for experimental and clinical studies.

Experimental small bowel transplantation using a newborn intestine in rats: IV. Effect of cold preservation on graft neovascularization

BACKGROUND/PURPOSE

University of Wisconsin (UW) solution is one of the most superior organ preservation solutions for liver, kidney, and pancreas; however, it still is controversial for intestinal preservation. Here, the authors studied the efficacy of preservation with 2 kinds of solutions, UW and modified TOM (m-TOM) solutions in our experimental newborn intestinal transplantation model. UW solution was used as a standard intracellular and m-TOM solution as an extracellular preservation solution. Lactated ringer (LR) solution was used as a control.

METHODS

Newborn intestine, which were preserved in these solutions for 24 or 48 hours, were transplanted in the subcutaneous spaces of the syngeneic recipients without surgical vascular anastomosis and histologically examined 14 days after grafting. The preserved grafts were evaluated histologically by use of light and electron microscopy just after preservation. The biochemical parameters such as LDH and serotonin also were measured in the supernatants of preservation solutions.

RESULTS

Fresh newborn grafts were revascularized successfully at a rate of 80% (16 of 20). After 24 hours of preservation, 65% (13 of 20), 75% (15 of 20), and 85% (17 of 20) of the grafts were observed to be revascularized in LR, m-TOM, and UW solutions, respectively. After 48 hours of preservation, 60% (12 of 20), 80% (16 of 20), and 80% (16 of 20) of the grafts also were revascularized in the respective solutions (no statistic difference among the groups). The cold-preservation did not affect the neovascularization of newborn intestine until 48 hours. Histologic findings of the preserved intestine and biochemical analyses showed that UW and m-TOM solutions kept villous architectures of the preserved grafts, however, might be harmful to enterochromaffin cells.

CONCLUSION

Long-time preservation of newborn intestine did not interfere with neovascularization and maturation. J Pediatr Surg 36:1805-1810.

Gene therapy in transplantation

Facilitation of solid organ and cell transplantation depends on metabolic and immunologic factors that can be manipulated ex vivo and in vivo using gene transfer technology. Vectors have been developed which can optimally transfer relevant genes to various tissues and organs. Interventions aimed at promoting tissue preservation before transplantation, prevention of oxidative stress and immunological rejection have recently become attractive options using viral and nonviral gene delivery vehicles. Further understanding of the mechanisms involved in tolerance induction as well as the facilitation of xenogeneic engraftment have made possible a variety of avenues that can be exploited using gene transfer technology.

Intestinal transplantation

Increasing experience with intestinal transplantation has led to the refinement of techniques to detect and treat rejection and infectious complications. Improved outcome has led to a broadening of the indications for intestinal transplantation, particularly solitary intestinal transplantation.