[Show abstract][Hide abstract] ABSTRACT: Islet transplantation is a successful β-cell replacement therapy for selected patients with type 1 diabetes mellitus. Although high rates of early insulin independence are achieved routinely, long-term function wanes over time. Intraportal transplantation is associated with procedural risks, requires multiple donors, and does not afford routine biopsy. Stem cell technologies may require potential for retrievability, and graft removal by hepatectomy is impractical. There is a clear clinical need for an alternative, optimized transplantation site. The subcutaneous space is a potential substitute, but transplantation of islets into this site has routinely failed to reverse diabetes. However, an implanted device, which becomes prevascularized before transplantation, may alter this equation.
Syngeneic mouse islets were transplanted subcutaneously within Sernova Corp's Cell Pouch (CP). All recipients were preimplanted with CPs 4 weeks before diabetes induction and transplantation. After transplantation, recipients were monitored for glycemic control and glucose tolerance.
Mouse islets transplanted into the CP routinely restored glycemic control with modest delay and responded well to glucose challenge, comparable to renal subcapsular islet grafts, despite a marginal islet dose, and normoglycemia was maintained until graft explantation. In contrast, islets transplanted subcutaneously alone failed to engraft. Islets within CPs stained positively for insulin, glucagon, and microvessels.
The CP is biocompatible, forms an environment suitable for islet engraftment, and offers a potential alternative to the intraportal site for islet and future stem cell therapies.This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives 3.0 License, where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially.
[Show abstract][Hide abstract] ABSTRACT: In islet transplantation, deceased cardiac death (DCD) donation has been identified as a potential extended source. There are currently no studies comparing outcomes between these categories, and our goal was to compare islet isolation success rates and transplantation outcomes between DCD and neurological determination of death (NDD) donors.
Islet isolations from 15 DCD and 418 NDD were performed in our centre between September 2008 and September 2014. Donor variables, islet yields, metabolic function of isolated isled and insulin requirements at 1-month post transplant were compared.
Compared to NDD, pancreata from DCD were more often procured locally and donors required less vasopressive support (p<0.001 and p=0.023, respectively), but the other variables were similar between groups. Pre- and post-purification islet yields were similar between NDD and DCD (576 vs. 608 x10(3) islet equivalent, p=0.628 and 386 vs. 379, p=0.881, respectively). The metabolic function was similar between NDD and DCD, as well as the mean decrease in insulin-requirement at 1-month post-transplantation (NDD: 64.82%; DCD: 60.17% reduction, p=0.517).
These results support the broader use of DCD pancreata for islet isolation. A much larger DCD islet experience will be required to truly determine non-inferiority of both short and long-term outcomes. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
Transplant International 08/2015; DOI:10.1111/tri.12650 · 2.60 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: There are potential advantages to the low-temperature (-196°C) banking of isolated islets, including the maintenance of viable islets for future research. We therefore assessed the in vitro and in vivo function of islets cryopreserved for nearly 20 years.
Human islets were cryopreserved from 1991 to 2001 and thawed between 2012 and 2014. These were characterised by immunostaining, patch-clamp electrophysiology, insulin secretion, transcriptome analysis and transplantation into a streptozotocin (STZ)-induced mouse model of diabetes.
The cryopreservation time was 17.6 ± 0.4 years (n = 43). The thawed islets stained positive with dithizone, contained insulin-positive and glucagon-positive cells, and displayed levels of apoptosis and transcriptome profiles similar to those of freshly isolated islets, although their insulin content was lower. The cryopreserved beta cells possessed ion channels and exocytotic responses identical to those of freshly isolated beta cells. Cells from a subset of five donors demonstrated similar perifusion insulin secretion profiles pre- and post-cryopreservation. The transplantation of cryopreserved islets into the diabetic mice improved their glucose tolerance but did not completely normalise their blood glucose levels. Circulating human insulin and insulin-positive grafts were detectable at 10 weeks post-transplantation.
We have demonstrated the potential for long-term banking of human islets for research, which could enable the use of tissue from a large number of donors with future technologies to gain new insight into diabetes.
[Show abstract][Hide abstract] ABSTRACT: Transplantation of donor-derived islets into the liver is a successful cellular replacement therapy for individuals with diabetes. However, the hepatic vasculature is not an optimal transplant site for several reasons, including graft attrition and the inability to retrieve or image the islets. Here we describe islet transplantation into a prevascularized, subcutaneous site created by temporary placement of a medically approved vascular access catheter. In mice with streptozotocin (STZ)-induced diabetes, transplantation of ∼500 syngeneic islets into the resulting 'device-less' space reversed diabetes in 91% of mice and maintained normoglycemia for >100 days. The approach was also effective in mice with pre-existing diabetes, in another mouse strain that mounts a more vigorous inflammatory response, and across an allogeneic barrier. These results demonstrate that transient priming of a subcutaneous site supports diabetes-reversing islet transplantation in mouse models without the need for a permanent cell-encapsulation device.
[Show abstract][Hide abstract] ABSTRACT: We report a unique first case of benign heterotopic pancreas arising within the proximal hepatic bile duct, containing a focus of intraductal papillary mucinous neoplasm (IPMN). The condition was diagnosed on pathological explant after left hepatic lobectomy with total extrahepatic bile duct excision.
[Show abstract][Hide abstract] ABSTRACT: Objective The spectrum of the surgeon-scientist ranges from a clinician who participates in the occasional research collaboration to the predominantly academic scientist with no involvement in clinical work. Training surgeon-scientists can involve resource-intense and lengthy training programs, including Masters and PhD degrees. Despite high enrollment rates in such programs, limited data exist regarding their outcome. The aim of the study was to investigate the scientific productivity of general surgeons who completed Masters or PhD graduate training compared with those who completed clinical residency training only.
[Show abstract][Hide abstract] ABSTRACT: Sulfonylureas are widely prescribed for the treatment of type 2 diabetes mellitus (T2DM). Through their actions on ATP-sensitive potassium (K ATP) channels, sulfonylureas boost insulin release from the pancreatic beta cell mass to restore glucose homeostasis. A limitation of these compounds is the elevated risk of developing hypoglycemia and cardio-vascular disease, both potentially fatal complications. Here, we describe the design and development of a photoswitchable sulfonylurea, JB253, which reversibly and repeatedly blocks K ATP channel activity following exposure to violet-blue light. Using in situ imaging and hormone assays, we further show that JB253 bestows light sensitivity upon rodent and human pancreatic beta cell function. Thus, JB253 enables the optical control of insulin release and may offer a valuable research tool for the interrogation of K ATP channel function in health and T2DM.
[Show abstract][Hide abstract] ABSTRACT: Islet transplantation is an effective means of treating severe type 1 diabetes in patients with life-threatening hypoglycemia. Improvements in glycemic control with correction of HbA1C enhance quality of life irrespective of insulin independence. By antagonizing the Natural Killer Group 2, member D (NKG2D) receptor expression on NK and CD8+ T cells, in combination with blocking CTLA-4 binding sites, we demonstrate a significant delay of graft rejection in islet allotransplant. Anti-NKG2D combined with CTLA-4 Ig (n = 15) results in prolonged allograft survival, with 84.6 ± 10% of the recipients displaying insulin independence compared to controls (n = 10, p < 0.001). The effect of combination therapy on graft survival is superior to treatments alone (CTLA-4 Ig vs. combination p = 0.024, anti-NKG2D vs. combination p < 0.001) indicating an interaction between these pathways. In addition, combination treatment also improves glucose tolerance when compared to controls (n = 10, p = 0.018). Histologically, NKG2D+ cells were significantly decreased within the allograft after 7 days of combination treatment (n = 6, p = 0.029). T cell proliferation was significantly reduced with anti-NKG2D therapy and CD8+ T cell daughter fractions were also significantly decreased with mAb and combination treatment when measured by in vitro mixed lymphocyte reaction (n = 5, p = 0.015, p = 0.005 and p = 0.048). These results demonstrate that inhibition of NKG2D receptors and costimulatory pathways enhance islet allograft survival.
American Journal of Transplantation 08/2014; 14(10). DOI:10.1111/ajt.12838 · 5.68 Impact Factor