Pancreas-After-Islet Transplantation in Nonuremic Type 1 Diabetes: A Strategy for Restoring Durable Insulin Independence

A Multi-Modal Approach to Islet and Pancreas Transplantation With Calcineurin-Sparing Immunosuppression Maintains Long-Term Insulin Independence in Patients With Type I Diabetes

Long-term success in beta-cell replacement remains limited by the toxic effects of calcineurin inhibitors (CNI) on beta-cells and renal function. We report a multi-modal approach including islet and pancreas-after-islet (PAI) transplant utilizing calcineurin-sparing immunosuppression. Ten consecutive non-uremic patients with Type 1 diabetes underwent islet transplant with immunosuppression based on belatacept (BELA; n = 5) or efalizumab (EFA; n = 5). Following islet failure, patients were considered for repeat islet infusion and/or PAI transplant. 70% of patients (four EFA, three BELA) maintained insulin independence at 10 years post-islet transplant, including four patients receiving a single islet infusion and three patients undergoing PAI transplant. 60% remain insulin independent at mean follow-up of 13.3 ± 1.1 years, including one patient 9 years after discontinuing all immunosuppression for adverse events, suggesting operational tolerance. All patients who underwent repeat islet transplant experienced graft failure. Overall, patients demonstrated preserved renal function, with a mild decrease in GFR from 76.5 ± 23.1 mL/min to 50.2 ± 27.1 mL/min (p = 0.192). Patients undergoing PAI showed the greatest degree of renal impairment following initiation of CNI (56% ± 18.7% decrease in GFR). In our series, repeat islet transplant is ineffective at maintaining long-term insulin independence. PAI results in durable insulin independence but is associated with impaired renal function secondary to CNI dependence.

Pancreas Transplantation: Current Challenges, Considerations, and Controversies

Pancreas transplantation (PTx) reestablishes an autoregulating source of endogenous insulin responsive to normal feedback controls. In addition to achieving complete β-cell replacement that frees the patient with diabetes from the need to monitor serum glucose and administer exogenous insulin, successful PTx provides counterregulatory hormone secretion and exocrine function. A functioning PTx mitigates glycemic variability, eliminates the daily stigma and burden of diabetes, restores normal glucose homeostasis in patients with complicated diabetes, and improves quality of life and life expectancy. The tradeoff is that it entails a major surgical procedure and requisite long-term immunosuppression. Despite the high likelihood of rendering patients euglycemic independent of exogenous insulin, PTx is considered a treatment rather than a cure. In spite of steadily improving outcomes in each successive era coupled with expansion of recipient selection criteria to include patients with a type 2 diabetes phenotype, a decline in PTx activity has occurred in the new millennium related to a number of factors including: (1) lack of a primary referral source and general acceptance by the diabetes care community; (2) absence of consensus criteria; and (3) access, education, and resource issues within the transplant community. In the author's experience, patients who present as potential candidates for PTx have felt as though they needed to circumvent the conventional diabetes care model to gain access to transplant options. PTx should be featured more prominently in the management algorithms for patients with insulin requiring diabetes who are failing exogenous insulin therapy or experiencing progressive diabetic complications regardless of diabetes type. Furthermore, all patients with diabetes and chronic kidney disease should undergo consideration for simultaneous pancreas-kidney transplantation independent of geography or location.

International Survey of Clinical Monitoring Practices in Pancreas and Islet Transplantation

BACKGROUND

The long-term outcomes of both pancreas and islet allotransplantation have been compromised by difficulties in the detection of early graft dysfunction at a time when a clinical intervention can prevent further deterioration and preserve allograft function. The lack of standardized strategies for monitoring pancreas and islet allograft function prompted an international survey established by an International Pancreas and Islet Transplant Association/European Pancreas and Islet Transplant Association working group.

METHODS

A global survey was administered to 24 pancreas and 18 islet programs using Redcap. The survey addressed protocolized and for-cause immunologic and metabolic monitoring strategies following pancreas and islet allotransplantation. All invited programs completed the survey.

RESULTS

The survey identified that in both pancreas and islet allograft programs, protocolized clinical monitoring practices included assessing body weight, fasting glucose/C-peptide, hemoglobin A1c, and donor-specific antibody. Protocolized monitoring in islet transplant programs relied on the addition of mixed meal tolerance test, continuous glucose monitoring, and autoantibody titers. In the setting of either suspicion for rejection or serially increasing hemoglobin A1c/fasting glucose levels postpancreas transplant, Doppler ultrasound, computed tomography, autoantibody titers, and pancreas graft biopsy were identified as adjunctive strategies to protocolized monitoring studies. No additional assays were identified in the setting of serially increasing hemoglobin A1c levels postislet transplantation.

CONCLUSIONS

This international survey identifies common immunologic and metabolic monitoring strategies utilized for protocol and for cause following pancreas and islet transplantation. In the absence of any formal studies to assess the efficacy of immunologic and metabolic testing to detect early allograft dysfunction, it can serve as a guidance document for developing monitoring algorithms following beta-cell replacement.

Evaluation of Autophagy Process in Differentiation of Human Induced Pluripotent Stem Cells toward Insulin Producing Cells

Background

Autophagy is an intracellular self-degradative homeostasis process which eliminates undesirable and harmful macromolecules and organelles. Autophagy is also involved in self-renewal and differentiation of induced pluripotent stem cell (iPSCs).

Objective

In this study, we investigated the expression profile of autophagy marker genes in human iPSCs during their differentiation induction toward insulin producing β-like cells.

Methods

Human iPSC line, R1-hiPSC1, was used for differentiation induction toward β-like cells. The mRNA expression of Nanog, OCT4 (pluripotency markers), SOX17, FOXA2 (endodermic markers), PTF1A, NKX6.1 (exocrine/endocrine determinants), and PDX1 were measured during differentiation stages. Autophagy was monitored by genes expression study of four autophagy markers, MAP1LC3B, BECN1, SQSTM1/P62 and ATG5, along with protein expression profile of LC3b-II during differentiation stages.

Results

The mRNA expression measurement of pluripotency, endoderm and exocrine/endocrine marker genes confirmed that hiPSCs skipped pluripotency, differentiated into endoderm, passed through the pancreatic lineage commitment stage and successfully generated insulin producing β-like cells. Expression profile of autophagy genes during differentiation stages indicated the decreased expression levels at the early stages (EB and MEI) and then increased at the definitive endoderm stages (DEI 1, DEI 2 and DE) followed by a subtractive pattern toward the end of differentiation. The results of protein expression of LC3b-II were consistent with gene expression data.

Conclusion

This study demonstrated the high contribution of key autophagy genes/proteins during the differentiation of hiPSC toward β-like cells. The enhanced autophagy levels were a prominent feature of early stages of differentiation and DE rather than the later stages.

Long-term Persistence of Allosensitization After Islet Allograft Failure

BACKGROUND

Allosensitization has been reported after discontinuation of immunosuppression following graft failure in islet transplantation (ITx) recipients, though duration of its persistence is unknown.

METHODS

We evaluated 35 patients with type 1 diabetes who received ITx, including 17 who developed graft failure (ITx alone, n = 13; ITx plus bone marrow-derived hematopoietic stem cells, n = 4) and 18 with persistent graft function. Panel-reactive antibody (PRA) was measured yearly for the duration of graft function within 1 y after graft failure at enrollment and yearly thereafter.

RESULTS

In ITx alone graft failure patients, 61% (8/13) were PRA-positive at 6 y postgraft failure, and 46% (6/13) developed donor-specific anti-HLA antibodies (DSA to 2 ± 1 donors) during follow-up. The degree of sensitization was variable (cPRA ranging between 22% and 100% after graft failure). Allosensitization persisted for 7-15 y. Three subjects (3/13) were not allosensitized. In ITx plus bone marrow-derived hematopoietic stem cell recipients, cPRA-positivity (88%-98%) and DSA positivity persisted for 15 y in 75% (3/4) of subjects.

CONCLUSIONS

Allosensitization was minimal while subjects remained on immunosuppression, but after discontinuation of immunosuppressive therapy, the majority of subjects (77%) became allosensitized with persistence of PRA positivity for up to 15 y. Persistence of allosensitization in this patient population is of clinical importance as it may result in longer transplant waiting list times for identification of a suitable donor in the case of requiring a subsequent transplant.

Examination of the Igls Criteria for Defining Functional Outcomes of β-cell Replacement Therapy: IPITA Symposium Report

CONTEXT

The Igls criteria were developed to provide a consensus definition for outcomes of β-cell replacement therapy in the treatment of diabetes during a January 2017 workshop sponsored by the International Pancreas & Islet Transplant Association (IPITA) and the European Pancreas & Islet Transplant Association. In July 2019, a symposium at the 17th IPITA World Congress was held to examine the Igls criteria after 2 years in clinical practice, including validation against continuous glucose monitoring (CGM)-derived glucose targets, and to propose future refinements that would allow for comparison of outcomes with artificial pancreas system approaches.

EVIDENCE ACQUISITION

Utilization of the criteria in various clinical and research settings was illustrated by population as well as individual outcome data of 4 islet and/or pancreas transplant centers. Validation against CGM metrics was conducted in 55 islet transplant recipients followed-up to 10 years from a fifth center.

EVIDENCE SYNTHESIS

The Igls criteria provided meaningful clinical assessment on an individual patient and treatment group level, allowing for comparison both within and between different β-cell replacement modalities. Important limitations include the need to account for changes in insulin requirements and C-peptide levels relative to baseline. In islet transplant recipients, CGM glucose time in range improved with each category of increasing β-cell graft function.

CONCLUSIONS

Future Igls 2.0 criteria should consider absolute rather than relative levels of insulin use and C-peptide as qualifiers with treatment success based on glucose assessment using CGM metrics on par with assessment of glycated hemoglobin and severe hypoglycemia events.

Eosinophil-to-monocyte ratio is an excellent predictor of acute cellular rejection in pancreas transplant alone recipients

Serum pancreatic enzymes (serum amylase and lipase) are sensitive markers for monitoring acute rejection in pancreatic transplant recipients. However, those enzymes are not specific, as their levels are elevated in other conditions. We evaluated the eosinophil-to-monocyte ratio (EMR) in peripheral blood as a biomarker of acute rejection in the clinical setting in recipients of pancreatic transplant alone. We performed 32 cases of pancreatic transplantation alone since 2015. Nine patients were diagnosed with rejection. Serum amylase and lipase levels and eosinophil and monocytes counts were analyzed and compared retrospectively between the non-rejection and rejection groups. The serum eosinophil count, eosinophil fraction of the complete blood count, and serum amylase and lipase levels were significant predictors of rejection according to the receiver operation characteristic (ROC) curve. However, the EMR was the best indicator of rejection based on the ROC curve (area under the curve 0.918, sensitivity 100%, specificity 76.2% at the cutoff value 0.80, P < .001). The combination of EMR and the lipase level had 100% sensitivity and 90.5% specificity. The EMR is a simple and excellent predictor of acute rejection in recipients of pancreatic transplant alone.

Pancreas transplantation following total pancreatectomy for chronic pancreatitis

BACKGROUND

Total pancreatectomy for chronic pancreatitis leads to brittle diabetes and challenging glycemic control with half of all patients experiencing severe hypoglycemia, many requiring medical intervention or hospitalization. Pancreas transplantation has the potential to manage both the endocrine and the exocrine insufficiency in this patient population.

METHODS

Between June 1, 2005, and July 1, 2016, 8 patients with brittle diabetes following total pancreatectomy underwent pancreas transplantation. All grafts had systemic venous and enteric exocrine drainage. Data included demographics, graft and patient survival, pre- and post-transplant supplementation with pancreatic enzymes, and narcotic usage.

RESULTS

Patient survival rate at 1 and 3 years was 88%. Pancreas graft survival rate of those alive at 1 year was 100% and 86%, respectively. About 75% of these patients remained insulin-free until their time of death, loss of follow-up, or present day. Of the patients with maintained graft function at 3 years, none required further hospitalization for glycemic control. About 75% of these patients have also maintained exocrine function without pancreatic enzyme supplementation.

CONCLUSIONS

Pancreas transplant can treat both exocrine and endocrine insufficiency and give long-term insulin-free survival and should be considered as a viable treatment option for patients who have undergone total pancreatectomy for chronic pancreatitis.

Steroid-free three-drug maintenance regimen for pancreas transplant alone: Comparison of induction with rabbit antithymocyte globulin +/- rituximab

Graft survival following pancreas transplant alone (PTA) is inferior to other pancreas transplants. Steroid elimination is appealing, but a two-drug maintenance strategy may be inadequate. Additionally, recipients tend to have diabetic nephropathy and do not tolerate nephrotoxic medications. A three-drug maintenance strategy permits immunosuppression through different mechanisms as well as an opportunity to use lower doses of the individual medications. Induction consisted of five doses of rabbit antithymocyte globulin (1 mg/kg/dose). As of October 2007, a single dose of rituximab (150 mg/m² ) was added. Maintenance consisted of tacrolimus, sirolimus and mycophenolate mofetil. From 2004 to 2017, 166 PTA were performed. Graft loss at 7 and 90 days were 4% and 5%, and 1-year patient and graft survival were 97% and 91%. Comparing induction without and with rituximab, there was no significant difference in 7- or 90-day graft loss, 1-year patient or graft survival, or in the rate of rejection or infection. Rabbit antithymocyte globulin induction and steroid withdrawal followed by a three-drug immunosuppression regimen is an excellent strategy for PTA recipients.