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Aims/hypothesis: Islet transplantation has been studied in small cohorts of recipients with type 1 diabetes complicated by severe hypoglycaemic events (SHEs). We determined factors associated with favourable outcomes in a large cohort of recipients reported to the Collaborative Islet Transplant Registry (CITR). Methods: In 398 non-uraemic islet transplant alone (ITA) recipients with type 1 diabetes and SHEs, transplanted between 1999 and 2015 and with at least 1 year follow-up, we analysed specified favourable outcomes against each of all available characteristics of pancreas donors, islet grafts, recipients and immunosuppressive regimens, as well as immunosuppression and procedure-related serious adverse events (SAEs). Results: Four factors were associated with the highest rates of favourable outcomes: recipient age ≥35 years; total infused islets ≥325,000 islet equivalents; induction immunosuppression with T cell depletion and/or TNF-α inhibition; and maintenance with both mechanistic target of rapamycin (mTOR) and calcineurin inhibitors. At 5 years after the last islet infusion, of the recipients meeting these four common favourable factors (4CFF; N=126), 95% were free of SHEs, 76% had HbA1c <53 mmol/mol (7.0%), 73% had HbA1c <53 mmol/mol (7.0%) and absence of SHEs, and 53% were insulin independent, significantly higher rates than in the remaining recipients (<4CFF; N=272). The incidence of procedural and immunosuppression-related SAEs per recipient that resulted in sequelae, disability or death was low in both the 4CFF (0.056 per person) and <4CFF (0.074 per person) groups. Conclusions/interpretation: In recipients with type 1 diabetes complicated by SHEs, islet transplantation meeting 4CFF protected 95% from SHEs at 5 years after the last islet infusion and exerted a large and significant benefit on glycaemic control, with an acceptable safety profile for this subgroup of type 1 diabetes. [ABSTRACT FROM AUTHOR]

Autologous human islet transplantation to mitigate or prevent surgically induced diabetes after total pancreatectomy for the relief of chronic pancreatitisinduced pain was pioneered in the late 1970s. Islet allotransplantation using islets from human donors to treat type 1 diabetes was first reported several years later. Over the last 40 years, methods for clinical islet transplantation have been methodically standardized to become the methods used today. Human islets are also isolated from donors with pathologies with the aim to conduct a broad range of investigational studies. Human islet isolation undertaken for research can provide the opportunity to further optimize and develop methods that may be helpful in the clinic. The variability of conditions associated with donor and pancreas makes consistent success in isolating islets a challenge, thus, we should re-evaluate the effectiveness of our methods of islet isolation. In order to do this, we must first consider that the intended outcomes for clinical islet transplantation and experimental investigations involving islet isolation are, in fact, quite different and that these differences impact the status and future considerations of islet isolation procedures.

Milestones in the history of diabetes therapy include the discovery of insulin and successful methods of beta cell replacement including whole pancreas and islet cell transplantation options. While pancreas transplantation remains the gold standard for patients who have difficulty controlling their symptoms with exogenous insulin, islet allotransplantation is now able to provide similar results with some advantages that make it an attractive potential alternative. The Edmonton Protocol, which incorporated a large dose of islets from multiple donors with steroid-free immunosuppression helped to establish the modern era of islet transplantation almost 20 years ago. While islet allotransplantation is recognized around the world as a powerful clinical therapy for type 1 diabetes it is not yet recognized by the Federal Drug Administration of the United States. Large-scale clinical trials administered by the Clinical Islet Transplantation Consortium have recently demonstrated that the well-regulated manufacture of a human islet product transplanted into patients with difficult to control type 1 diabetes and with a history of severe hyperglycemic episodes can safely and efficaciously maintain glycemic balance and eliminate the most severe complications associated with diabetes. The results of these clinical trials have established a strong basis for licensure of clinical islet allotransplantation in the US. Recognition by the Federal Drug Administration would likely lead to third party reimbursement for islet allotransplantation as a therapeutic option in the United States and would make the treatment available to many more patients. The high costs of rampant diabetes justify the expense of the treatment, which is in-line with the costs of clinical pancreas transplantation. While much enthusiasm and hope is raised toward the development and optimization of stem cell therapy, the islet transplantation community should push toward licensure, if that means broader access of this procedure to patients who may benefit from it. Even as we prepare to take the first steps in that direction, we must acknowledge the new challenges that a shift from the experimental to clinical will bring. Clinical islet allotransplantation in the United States would be a game-changing event in the treatment of type 1 diabetes and also generate enthusiasm for continued research.

Background: Effective digestive enzymes are crucial for successful islet isolation. Supplemental proteases are essential because they synergize with collagenase for effective pancreatic digestion. The activity of these enzymes is critically dependent on the presence of Ca 2+ ions at a concentration of 5-10 mM. The present study aimed to determine the Ca 2+ concentration during human islet isolation and to ascertain whether the addition of supplementary Ca 2+ is required to maintain an optimal Ca 2+ concentration during the various phases of the islet isolation process., Methods: Human islets were isolated according to standard methods and isolation parameters. Islet quality control and the number of isolations fulfilling standard transplantation criteria were evaluated. Ca 2+ was determined by using standard clinical chemistry routines. Islet isolation was performed with or without addition of supplementary Ca 2+ to reach a Ca 2+ of 5 mM., Results: Ca 2+ concentration was markedly reduced in bicarbonate-based buffers, especially if additional bicarbonate was used to adjust the pH as recommended by the Clinical Islet Transplantation Consortium. A major reduction in Ca 2+ concentration was also observed during pancreatic enzyme perfusion, digestion, and harvest. Additional Ca 2+ supplementation of media used for dissolving the enzymes and during digestion, perfusion, and harvest was necessary in order to obtain the concentration recommended for optimal enzyme activity and efficient liberation of a large number of islets from the human pancreas., Conclusions: Ca 2+ is to a large extent consumed during clinical islet isolation, and in the absence of supplementation, the concentration fell below that recommended for optimal enzyme activity. Ca 2+ supplementation of the media used during human pancreas digestion is necessary to maintain the concentration recommended for optimal enzyme activity. Addition of Ca 2+ to the enzyme blend has been implemented in the standard isolation protocols in the Nordic Network for Clinical Islet Transplantation.