Clinical Islet Transplantation — Registry Report, Accomplishments in the past and Future Research Needs

This review provides the results of a recent analysis of the Islet Transplant Registry on clinical adult islet transplants performed worldwide through June 30, 1992. Between December 12, 1893 and June 30, 1992, 167 adult islet transplants were performed at 25 institutions worldwide, including 104 at 9 institutions in North America, 62 at 15 institutions in Europe, and 1 elsewhere. The total number of diabetic patients reported to be insulin independent after adult islet allotransplantation through June 30,1992, was 19. In an analysis by era, the percentage of patients that showed positive basal C-peptide levels (i.e. ≥ 1 ng/mL at ≥ 1 mo) posttransplant, and that became insulin independent (>1 wk) in the 1985-1989 era (n = 35 cases) were 20% and 6%, and in the 1990-1992 era (n = 69 cases) were 64% and 20%, respectively, and thus have improved significantly (p < 0.001 and p < 0.05). For the 1990-1992 period, the percentage of patients who showed positive basal C-peptide levels post-transplant, and who became insulin independent in the single donor pancreas group (n = 31 cases) were 52% and 13%, and in the multiple donor pancreata group (n = 36 cases) were 75% and 28%, respectively. Islet graft function rates were nearly identical for grafts prepared from pancreata stored ≤6 h (n = 27) and >6 ≤ 12 h (n = 29), so that 67% and 72% showed positive basal C-peptide levels, and 30% and 21% of the recipients became insulin independent, respectively. No single patient showed islet graft function sufficient to allow withdrawal from insulin, if the pancreata have been stored for more than 12 h. In regard to recipient category for the six groups, namely IAK (islet after kidney), SIK (simultaneous islet kidney transplantation), SIL (simultaneous islet liver transplantation), SIL(C) (simultaneous islet liver transplantation after cluster operation), SIKL (simultaneous islet kidney liver transplantation), and SIH-L (simultaneous islet heart-lung transplantation), the number of patients who showed positive basal C-peptide levels post-transplant was 11 (58%), 17 (57%), 5 (83%), 8 (80%), 1 (50%), and 0 (0%), and the number of insulin independent patients was 4 (21%), 4 (13%), 0 (0%), 6 (60%), 0 (0%), and 0 (0%), respectively. Comparing the two largest recipient categories, namely IAK and SIK, no difference in the outcome of these transplants was apparent. The only sites of transplantation in the period between 1990-1992 were the liver, epiploic flap, and spleen, with the total number of recipients being 60 (90%), 4 (6%), and 3 (4%), respectively. For these three groups, the number of patients who showed positive basal C-peptide levels was 38 (63%), 2 (50%), and 1 (33%), and the number of insulin independent patients was 13 (22%), 0 (0%) and 0 (0%), respectively. In the overwhelming majority of cases, recipient selection was not based on prospective HLA donor/recipient matching. In different categories of HLA mismatching (i.e., AB-, DR-, BDR-, and ABDR-mismatch) no obvious tendency or difference in outcome could be demonstrated. In the 1990-1992 period, 16 patients (24%) received OKT3, 26 patients (39%) received ALS, ALG, or ATG, and 25 patients (37%) received neither monoclonal nor polyclonal T-cell antibodies for induction immunosuppression. For the three groups mentioned, the number of patients who showed positive basal C-peptide levels was 12 (86%), 16 (62%), and 15 (60%), and the number of insulin independent patients was 2 (14%), 6 (23%), and 6 (24%), respectively. A synopsis of all pretransplant C-peptide-negative Type I diabetic patients who succeeded in insulin independence revealed certain common characteristics, such as transplantations of ≥8000 islet equivalents per kilogram body weight, a purity of transplanted islets ≥ 50% (in all but one case), the liver as implantation site, and OKT3 or ALG/ ALS/ATG for induction immunosuppression (“state of the art” cases). Because it has been unequivocally proven that islet transplantation can be performed successfully in association with other organ transplants, more attention should be drawn to the nonuremic, nonkidney Type I diabetic patients, who have not been reported in a single case since 1990. This is the real target group, that could benefit most from islet replacement. However, islet transplantation in this recipient category will only have an undisputable indication, if low-risk, but effective methods other than life-long immunosuppression to protect the islet graft from rejection can be developed.