Gunnar Tufveson

Production of tissue factor by pancreatic islet cells as a trigger of detrimental thrombotic reactions in clinical islet transplantation

BACKGROUND Intraportal transplantation of pancreatic islets offers improved glycaemic control and insulin independence in type 1 diabetes mellitus, but intraportal thrombosis remains a possible complication. The thrombotic reaction may explain why graft loss occurs and islets from more than one donor are needed, since contact between human islets and ABO-compatible blood in vitro triggers a thrombotic reaction that damages the islets. We investigated the possible mechanism and treatment of such thrombotic reactions. METHODS Coagulation activation and islet damage were monitored in four patients undergoing clinical islet transplantation according to a modified Edmonton protocol. Expression of tissue factor (TF) in the islet preparations was investigated by immunohistochemistry, immunoprecipitation, electron microscopy, and RT-PCR. To assess TF activity in purified islets, human islets were mixed with non-anticoagulated ABO-compatible blood in tubing loops coated with heparin. FINDINGS Coagulation activation and subsequent release of insulin were found consistently after clinical islet transplantation, even in the absence of signs of intraportal thrombosis. The endocrine, but not the exocrine, cells of the pancreas were found to synthesise and secrete active TF. The clotting reaction triggered by pancreatic islets in vitro could be abrogated by blocking the active site of TF with specific antibodies or site-inactivated factor VIIa, a candidate drug for inhibition of TF activity in vivo. INTERPRETATION Blockade of TF represents a new therapeutic approach that might increase the success of islet transplantation in patients with type 1 diabetes, in terms of both the risk of intraportal thrombosis and the need for islets from more than one donor.

Ischemic heart disease - major cause of death and graft loss after renal transplantation in Scandinavia.

Causes of graft loss and death were studied in 1347 recipients of primary renal transplants followed for 5 years after transplantation irrespective of graft function. Immunosuppression consisted of high or medium dose CsA and prednisolone or low dose CsA and prednisolone and azathioprine. In recipients of cadaver grafts, death with a functioning transplant was more common than graft rejection after the first posttransplant year, accounting for 49% and 41% of the graft losses, respectively. Of deaths with a functioning graft, 53% were due to ischemic heart disease (IHD) and 10% were due to other vascular disease. In the 55− to 64-year-old age group, the risk of death from IHD was 6.4 times higher in the transplanted nondiabetic patients, 8.6 times higher in the dialysis patients (European Dialysis and Transplant Association figures), and 20.8 times higher in the transplanted diabetic patients than in the general population (national figures). A multivariate Cox regression analysis showed that old age, diabetes mellitus, occurrence of acute rejection, pretransplant transfusions, delayed onset of graft function, and male gender were significant for death in IHD. We conclude that, in comparison to reports from other regions, Scandinavian renal transplant recipients are at high risk of dying of HID. Future advances in long-term renal graft survival will depend largely on the success of preventing myocardial infarction and death in this patient population.

The impact of acute rejection episodes on long-term graft function and outcome in 1347 primary renal transplants treated by 3 cyclosporine regimens.

To characterize factors of importance for the occurrence of acute rejection as well as study the impact of these episodes on long-term renal survival and function, a total of 819 acute rejection episodes were studied in 951 primary cadaveric donor kidney recipients (CD) and in 396 primary living donor kidney recipients (LD). The patients were treated by three immunosuppressive schedules, namely, CsA given in a high dose, a medium dose, or a low dose. Additionally, all patients received PRED and patients in the low-dose group received AZA. The incidence of acute rejection was higher and occurred earlier after transplantation in the CsA medium dose and low dose groups than in the CsA high dose group (P < 0.05 and P < 0.01, respectively). Although the incidence of first acute rejection was similar in CD and LD patients, 59.1% vs. 60.6%, it was successfully reversed by antirejection treatment in a higher percentage in LD patients. The estimated graft half-life was shorter in patients who had acute rejection episodes than those who did not, 6.6 years vs. 12.5 years in CD pa

Islet Surface Heparinization Prevents the Instant Blood-Mediated Inflammatory Reaction in Islet Transplantation

OBJECTIVE—In clinical islet transplantation, the instant blood-mediated inflammatory reaction (IBMIR) is a major factor contributing to the poor initial engraftment of the islets. This reaction is triggered by tissue factor and monocyte chemoattractant protein (MCP)-1, expressed by the transplanted pancreatic islets when the islets come in contact with blood in the portal vein. All currently identified systemic inhibitors of the IBMIR are associated with a significantly increased risk of bleeding or other side effects. To avoid systemic treatment, the aim of the present study was to render the islet graft blood biocompatible by applying a continuous heparin coating to the islet surface. RESEARCH DESIGN AND METHODS—A biotin/avidin technique was used to conjugate preformed heparin complexes to the surface of pancreatic islets. This endothelial-like coating was achieved by conjugating barely 40 IU heparin per full-size clinical islet transplant. RESULTS—Both in an in vitro loop model and in an allogeneic porcine model of clinical islet transplantation, this heparin coating provided protection against the IBMIR. Culturing heparinized islets for 24 h did not affect insulin release after glucose challenge, and heparin-coated islets cured diabetic mice in a manner similar to untreated islets. CONCLUSIONS—This novel pretreatment procedure prevents intraportal thrombosis and efficiently inhibits the IBMIR without increasing the bleeding risk and, unlike other pretreatment procedures (e.g., gene therapy), without inducing acute or chronic toxicity in the islets.

Implementation of a Protocol for ABO-incompatible kidney transplantation--a three-center experience with 60 consecutive transplantations

Background. A new protocol for ABO-incompatible kidney transplantation has recently been introduced. We report here on the joint experience of the implementation in Stockholm and Uppsala, Sweden and Freiburg, Germany. Methods. The new protocol utilizes antigen-specific immunoadsorption to remove existing ABO-antibodies, rituximab, and intravenous immunoglobulin to prevent the rebound of antibodies, and conventional tacrolimus, mycophenolate-mofetil, and prednisolone immunosuppression. Sixty consecutive ABO-incompatible kidney transplantations were included in the study. The outcome is compared with the results of 274 ABO-compatible live donor transplantations performed during the same period. Results. Two of the ABO-incompatible grafts have been lost (non-compliance and death with functioning graft). All the remaining 58 grafts had good renal function at a follow-up of up to 61 months. We did not observe any late rebound of antibodies and there were no humoral rejections. Graft survival was 97% for the ABO-incompatible compared with 95% for the ABO-compatible. Patient survival was 98% in both groups. There was a significant variation in preoperative A/B-antibody titer between the centers, with a median 1:8 in Uppsala, median 1:32 in Stockholm and median 1:128 in Freiburg. More preoperative antibody adsorptions were therefore needed in Freiburg than in Stockholm and Uppsala. Conclusions. The new protocol was easily implemented and there were no graft losses that could be related to ABO-incompatibility. A significant inter-institutional variation in the measurement of anti-AB-antibodies was found, having a substantial impact on the number of immunoadsorptions and consequently on the total cost for the procedure. A standardized fluorescence-activated cell sorting technique for antibody quantification is much needed.

Optimising islet engraftment is critical for successful clinical islet transplantation

Clinical islet transplantation is currently being explored as a treatment for persons with type 1 diabetes and hypoglycaemia unawareness. Although ‘proof-of-principle’ has been established in recent clinical studies, the procedure suffers from low efficacy. At the time of transplantation, the isolated islets are allowed to embolise the liver after injection in the portal vein, a procedure that is unique in the area of transplantation. A novel view on the engraftment of intraportally transplanted islets is presented that could explain the low efficacy of the procedure.

Nicotinamide inhibits tissue factor expression in isolated human pancreatic islets: Implications for clinical islet transplantation

Background. Islet-produced tissue factor (TF) triggers an adverse clotting reaction, the instant blood-mediated inflammatory reaction (IBMIR), providing a likely explanation for the need of tissue from multiple donors in clinical islet transplantation. In this study, the authors investigated whether compounds previously shown to affect TF and macrophage chemoattractant protein (MCP)-1 expression in monocytes and endothelial cells have the same effect in human islet cells. Methods. Islets were cultured in the presence of l-arginine, cyclosporine A, enalapril, or nicotinamide for 48 hr, after which the TF content and MCP-1 expression were assessed. The effect of nicotinamide on IBMIR was evaluated by exposing the treated islets to fresh human ABO-compatible blood in an in vitro loop model. Results. Nicotinamide was the only compound that significantly reduced both TF and MCP-1. This reduction was dose-dependent. The level of MCP-1 was strongly correlated with TF expression (r2=0.98). In addition, the level of TF was also correlated with the ability of the islets to initiate IBMIR (r2=0.94). Conclusions. TF and MCP-1 expression in human islets can be decreased by adding nicotinamide to the culture medium. These observations indicate that the adverse effects of IBMIR in clinical islet transplantation could be reduced without endangering the recipient using antithrombotic drugs.

A Randomized, Doubleblind, Placebo-Controlled, Study of Single-Dose Rituximab as Induction in Renal Transplantation

We performed a prospective, double blind, randomized, placebo-controlled multicenter study on the efficacy and safety of rituximab as induction therapy, together with tacrolimus, mycophenolate mofetil, and steroids. The primary endpoint was defined as acute rejection, graft loss, or death during the first 6 months. Secondary endpoints were creatinine clearance, incidence of infections, and incidence of rituximab-related adverse event. Results. We enrolled140 patients (44 living donor and 96 deceased donor), and of those, 68 rituximab and 68 placebo patients fulfilled the study. In all the patients receiving rituximab, there was a complete depletion of CD19/CD20 cells, whereas there was no change in the number of CD19/CD20 cells in the placebo group. There were 10 treatment failures in the rituximab group versus 14 in the placebo group (P=0.348). There were eight rejection episodes in the rituximab group versus 12 in the placebo group (P=0.317) Creatinine clearance was 66±22 mL/min in the study group and 67±23 mL/min in the placebo group. There was no difference in the number of bacterial infections, cytomegalovirus infections, and BK virus infections or fungal infections. Conclusion. We performed a placebo-controlled study of rituximab induction in renal transplantation. There was a tendency toward fewer and milder rejections during the first 6 months in the rituximab group. Although induction with one dose of rituximab induced a complete depletion B cells, there was no increase in the incidence of infectious complications or leukopenia and it seems safe, therefore, to conduct further studies on the use of rituximab in transplantation.

Positron emission tomography in clinical islet transplantation.

The fate of islets in clinical transplantation is unclear. To elude on this positron emission tomography combined with computed tomography (PET/CT) was performed for 60 min during islet transplantation in five patients receiving six transplants.

Increased hyaluronan in acutely rejecting human kidney grafts

The glycosaminoglycan hyaluronan is not only involved in cellular differentiation and migration but may also play a role in several inflammatory diseases. We have previously demonstrated an increased local production of hyaluronan in chronically rejected kidneys and the correspondingly affected renal vessels. In this report, we demonstrate the presence of hyaluronan in acutely rejecting kidneys. A total of 77 biopsies classified as either acute rejection or nonrejecting were analyzed using a biotin-labeled hyaluronan-binding protein in conjunction with an avidin-biotin peroxidase detection system and graded using an arbitrary scale from 0 to 3. Those biopsies classified as nonrejecting did not contain any peritubular hyaluronan in the cortex, with hyaluronan being localized only in the medulla. In contrast, those biopsies exhibiting acute rejection had an increase of hyaluronan both in the cortex and in the medulla. This increase was significantly different (P=0.0001) and correlated with edema and interstitial inflammation. The detection of the local hyaluronan production may be a useful marker to measure acute rejection episodes.