Peter A. Senior

Improvement in Outcomes of Clinical Islet Transplantation: 1999–2010

OBJECTIVE To describe trends of primary efficacy and safety outcomes of islet transplantation in type 1 diabetes recipients with severe hypoglycemia from the Collaborative Islet Transplant Registry (CITR) from 1999 to 2010. RESEARCH DESIGN AND METHODS A total of 677 islet transplant-alone or islet-after-kidney recipients with type 1 diabetes in the CITR were analyzed for five primary efficacy outcomes and overall safety to identify any differences by early (1999–2002), mid (2003–2006), or recent (2007–2010) transplant era based on annual follow-up to 5 years. RESULTS Insulin independence at 3 years after transplant improved from 27% in the early era (1999–2002, n = 214) to 37% in the mid (2003–2006, n = 255) and to 44% in the most recent era (2007–2010, n = 208; P = 0.006 for years-by-era; P = 0.01 for era alone). C-peptide ≥0.3 ng/mL, indicative of islet graft function, was retained longer in the most recent era (P < 0.001). Reduction of HbA1c and resolution of severe hypoglycemia exhibited enduring long-term effects. Fasting blood glucose stabilization also showed improvements in the most recent era. There were also modest reductions in the occurrence of adverse events. The islet reinfusion rate was lower: 48% by 1 year in 2007–2010 vs. 60–65% in 1999–2006 (P < 0.01). Recipients that ever achieved insulin-independence experienced longer duration of islet graft function (P < 0.001). CONCLUSIONS The CITR shows improvement in primary efficacy and safety outcomes of islet transplantation in recipients who received transplants in 2007–2010 compared with those in 1999–2006, with fewer islet infusions and adverse events per recipient.

Guidelines for the management of chronic kidney disease

New guidelines for the management of chronic kidney disease have been developed by the Canadian Society of Nephrology (Appendix 1 contains the full-text guidelines; available at [www.cmaj.ca/cgi/content/full/179/11/1154/DC1][1]). These guidelines describe key aspects of the management of chronic

High risk of sensitization after failed islet transplantation.

Human Leukocyte Antigen (HLA) antibodies posttransplant have been associated with an increased risk of early graft failure in kidney transplants. Whether this also applies to islet transplantation is not clear. To achieve insulin independence after islet transplants multiple donor infusions may be required. Hence, islet transplant recipients are at risk of sensitization after transplantation. Islet transplant recipients were screened for HLA antibodies posttransplant by flow‐based methods. A total of 98 patients were studied. Twenty‐nine patients (31%) developed de novo donor specific antibodies (DSA) posttransplant. Twenty‐three patients developed DSA while on immunosuppression (IS). Among recipients who have discontinued IS, 10/14 (71%) are broadly sensitized with panel reactive antibody (PRA) ≥50%. The risk of becoming broadly sensitized after transplant was 11/69 (16%) if the recipient was unsensitized prior to transplant. The majority of these antibodies have persisted over time. Appearance of HLA antibodies posttransplant is concerning, and the incidence rises abruptly in subjects weaned completely from IS. This may negatively impact the ability of these individuals to undergo further islet, pancreas or kidney transplantation and should be discussed upfront during evaluation of candidates for islet transplantation.

Phase 3 Trial of Transplantation of Human Islets in Type 1 Diabetes Complicated by Severe Hypoglycemia

OBJECTIVE Impaired awareness of hypoglycemia (IAH) and severe hypoglycemic events (SHEs) cause substantial morbidity and mortality in patients with type 1 diabetes (T1D). Current therapies are effective in preventing SHEs in 50–80% of patients with IAH and SHEs, leaving a substantial number of patients at risk. We evaluated the effectiveness and safety of a standardized human pancreatic islet product in subjects in whom IAH and SHEs persisted despite medical treatment. RESEARCH DESIGN AND METHODS This multicenter, single-arm, phase 3 study of the investigational product purified human pancreatic islets (PHPI) was conducted at eight centers in North America. Forty-eight adults with T1D for >5 years, absent stimulated C-peptide, and documented IAH and SHEs despite expert care were enrolled. Each received immunosuppression and one or more transplants of PHPI, manufactured on-site under good manufacturing practice conditions using a common batch record and standardized lot release criteria and test methods. The primary end point was the achievement of HbA1c <7.0% (53 mmol/mol) at day 365 and freedom from SHEs from day 28 to day 365 after the first transplant. RESULTS The primary end point was successfully met by 87.5% of subjects at 1 year and by 71% at 2 years. The median HbA1c level was 5.6% (38 mmol/mol) at both 1 and 2 years. Hypoglycemia awareness was restored, with highly significant improvements in Clarke and HYPO scores (P > 0.0001). No study-related deaths or disabilities occurred. Five of the enrollees (10.4%) experienced bleeds requiring transfusions (corresponding to 5 of 75 procedures), and two enrollees (4.1%) had infections attributed to immunosuppression. Glomerular filtration rate decreased significantly on immunosuppression, and donor-specific antibodies developed in two patients. CONCLUSIONS Transplanted PHPI provided glycemic control, restoration of hypoglycemia awareness, and protection from SHEs in subjects with intractable IAH and SHEs. Safety events occurred related to the infusion procedure and immunosuppression, including bleeding and decreased renal function. Islet transplantation should be considered for patients with T1D and IAH in whom other, less invasive current treatments have been ineffective in preventing SHEs.

Prevention of Bleeding After Islet Transplantation: Lessons Learned from a Multivariate Analysis of 132 Cases at a Single Institution

Islet transplantation is being offered increasingly for selected patients with unstable type 1 diabetes. Percutaneous transhepatic portal access avoids a need for surgery, but is associated with potential risk of bleeding. Between 1999 and 2005, we performed 132 percutaneous transhepatic islet transplants in 67 patients. We encountered bleeding in 18/132 cases (13.6%). In univariate analysis, the risk of bleeding in the absence of effective track ablation was associated with an increasing number of procedures (2nd and 3rd procedures with an odds ratio (OR) of 9.5 and 20.9, respectively), platelets count <150 000 (OR 4.4), elevated portal pressure (OR 1.1 per mm Hg rise), heparin dose ≥45 U/kg (OR 9.8) and pre‐transplant aspirin (81 mg per day) (OR 2.6, p = 0.05). A multivariate analysis further confirmed the cumulative transplant procedure number (p < 0.001) and heparin dose ≥45 U/kg (p = 0.02) as independent risk factors for bleeding. Effective mechanical sealing of the intrahepatic portal catheter tract with thrombostatic coils and tissue fibrin glue completely prevented bleeding in all subsequent procedures (n = 26, p = 0.02). We conclude that bleeding after percutaneous islet implantation is an avoidable complication provided the intraparenchymal liver tract is sealed effectively.

The Impact of Frequent and Unrecognized Hypoglycemia on Mortality in the ACCORD Study

OBJECTIVE The aim of this study was to examine the relationship between frequent and unrecognized hypoglycemia and mortality in the Action to Control Cardiovascular Risk in Diabetes (ACCORD) study cohort. RESEARCH DESIGN AND METHODS A total of 10,096 ACCORD study participants with follow-up for both hypoglycemia and mortality were included. Hazard ratios (95% CIs) relating the risk of death to the updated annualized number of hypoglycemic episodes and the updated annualized number of intervals with unrecognized hypoglycemia were obtained using Cox proportional hazards regression models, allowing for these hypoglycemia variables as time-dependent covariates and controlling for the baseline covariates. RESULTS Participants in the intensive group reported a mean of 1.06 hypoglycemic episodes (self-monitored blood glucose <70 mg/dL or <3.9 mmol/L) in the 7 days preceding their regular 4-month visit, whereas participants in the standard group reported an average of 0.29 episodes. Unrecognized hypoglycemia was reported, on average, at 5.8% of the intensive group 4-month visits and 2.6% of the standard group visits. Hazard ratios for mortality in models including frequency of hypoglycemic episodes were 0.93 (95% CI 0.9–0.97; P < 0.001) for participants in the intensive group and 0.98 (0.91–1.06; P = 0.615) for participants in the standard group. The hazard ratios for mortality in models, including unrecognized hypoglycemia, were not statistically significant for either group. CONCLUSIONS Recognized and unrecognized hypoglycemia was more common in the intensive group than in the standard group. In the intensive group of the ACCORD study, a small but statistically significant inverse relationship of uncertain clinical importance was identified between the number of hypoglycemic episodes and the risk of death among participants.

Changes in Renal Function after Clinical Islet Transplantation: Four‐Year Observational Study

Tight glycemic control can reduce progression of diabetic nephropathy (DN) while the histological changes may regress after pancreas transplantation. Clinical islet transplantation (CIT) can restore euglycemia but the effects of CIT and concomitant immunosuppression on renal function are not known. Renal function (modification of diet in renal disease estimated glomerular filtration rate [GFR]) is reported in 41 type 1 diabetes subjects followed for 29.8 (6–57) months after CIT who received sirolimus and tacrolimus. HbA1c improved by 3 months (6.1 ± 0.5 vs. 8.1 ± 1.3%, p < 0.001) and was sustained. Over 4 years estimated GFR (eGFR) declined (repeated measures ANOVA: p = 0.0011). The median rate of change in eGFR was −0.39 mL/min/1.73 m2/month but was highly variable (range: +1.62 to −2.79 mL/min/1.73 m2/month). Progression of albuminuria was observed in ten individuals while regression of microalbuminuria was observed in only one (chi square = 22.51, df = 4, p = 0.0002). Despite improved glycemia, CIT and concomitant immunosuppression, was associated with a fall in eGFR and progression of albuminuria over 4 years of observation. The rate of decline in eGFR was extremely variable and difficult to predict. The risk of progressive nephrotoxicity with decline in eGFR should be discussed with prospective CIT candidates and the risk: benefit ratio carefully considered in individuals with pre‐existing renal impairment.

Risk factors for islet loss during culture prior to transplantation

Culturing islets can add great flexibility to a clinical islet transplant program. However, a reduction in the islet mass has been frequently observed during culture and its degree varies. The aim of this study was to identify the risk factors associated with a significant islet loss during culture. One‐hundred and four islet preparations cultured in an attempt to use for transplantation constituted this study. After culture for 20 h (median), islet yield significantly decreased from 363 309 ± 12 647 to 313 035 ± 10 862 islet equivalent yield (IE) (mean ± SE), accompanied by a reduction in packed tissue volume from 3.9 ± 0.1 to 3.0 ± 0.1 ml and islet index (IE/islet particle count) from 1.20 ± 0.04 to 1.05 ± 0.04. Culture did not markedly alter islet purity or percent of trapped islet. Morphology score and viability were significantly improved after culture. Of 104 islet preparations, 37 suffered a substantial islet loss (>20%) over culture. Factors significantly associated with risk of islet loss identified by univariate analysis were longer cold ischemia time, two‐layer method (TLM) preservation, lower islet purity, and higher islet index. Multivariate analysis revealed that independent predictors of islet loss were higher islet index and the use of TLM. This study provides novel information on the link between donor‐ isolation factors and islet loss during culture.

Proteinuria developing after clinical islet transplantation resolves with sirolimus withdrawal and increased tacrolimus dosing

Sirolimus is a potent immunosuppressant, which may permit the avoidance of nephrotoxic calcineurin inhibitors (CNI). However, cases of proteinuria associated with sirolimus have been reported following renal transplantation. Here, we report three cases of proteinuria (1, 2 and 7 g/day) developing during therapy with sirolimus plus low‐dose tacrolimus following clinical islet transplantation (CIT) in type I diabetic subjects. The proteinuria resolved after discontinuation of sirolimus, substituted by mycophenolate mofetil (MMF) combined with an increased dose of tacrolimus. A renal biopsy in one case indicated only the presence of diabetic glomerulopathy. Five other CIT recipients developed microalbuminuria while on sirolimus which all resolved after switching to tacrolimus and MMF. The resolution of proteinuria from the native kidneys of CIT recipients after the discontinuation sirolimus suggests that, at least in some individuals, sirolimus itself may have adverse renal effects. Sirolimus should be used cautiously with close monitoring for proteinuria or renal dysfunction.

Pretransplant HLA antibodies are associated with reduced graft survival after clinical islet transplantation.

Despite significant improvements in islet transplantation, long‐term graft function is still not optimal. It is likely that both immune and nonimmune factors are involved in the deterioration of islet function over time. Historically, the pretransplant T‐cell crossmatch and antibody screening were done by anti‐human globulin—complement‐dependent cytotoxicity (AHG‐CDC). Class II antibodies were not evaluated. In 2003, we introduced solid‐phase antibody screening using flow‐based beads and flow crossmatching. We were interested to know whether pretransplant human leukocyte antigen (HLA) antibodies or a positive flow crossmatch impacted islet function post‐transplant. A total of 152 islet transplants was performed in 81 patients. Islet function was determined by a positive C‐peptide. Results were analyzed by procedure. Class I and class II panel reactive antibody (PRA) > 15% and donor‐specific antibodies (DSA) were associated with a reduced C‐peptide survival (p < 0.0001 and p < 0.0001, respectively). A positive T‐ and or B‐cell crossmatch alone was not. Pretransplant HLA antibodies detectable by flow beads are associated with reduced graft survival. This suggests that the sirolimus and low‐dose tacrolimus‐based immunosuppression may not control the alloimmune response in this presensitized population and individuals with a PRA > 15% may require more aggressive inductive and maintenance immunosuppression, or represent a group that may not benefit from islet transplantation.