Diabetes Is Reversed in a Murine Model by Marginal Mass Syngeneic Islet Transplantation Using a Subcutaneous Cell Pouch Device.

BACKGROUND: Islet transplantation is a successful ß-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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Establishment of a stringent large animal model of insulin-dependent diabetes for islet autotransplantation: combination of pancreatectomy and streptozotocin.

OBJECTIVE: A stringent porcine islet autograft diabetes model was developed to enable the assessment of autoislet safety and efficacy in either portal vein or an extrahepatic site. METHODS: A 95% pancreatectomy was performed preserving the pancreaticoduodenal arcade; however, glycemic control was still maintained at 3.3 ± 0.3 days (mean ± SEM), shown by euglycemic fasting blood glucose levels of 4.9 ± 0.8 mmol/L (mean ± SEM, n = 3). To reduce surgical complications and eliminate remaining islets, pigs were dosed intravenously after a modified 90% pancreatectomy, with 150-mg/kg streptozotocin, producing a diabetic state (18.9 ± 1.8 mmol/L [mean ± SEM], n = 8; P < 0.001) within 2.0 ± 0.9 days (mean ± SEM). RESULTS: Animals presented with sustained hyperglycemia, failing a glucose challenge test 12 weeks after diabetic induction, and showed no stimulated C-peptide secretion compared to nondiabetic controls (baseline: 0.479 ± 0.080 ng/mL [mean ± SEM] vs after procedure: 0.219 ± 0.055 ng/mL [mean ± SEM], P = 0.02). Diabetic animals were maintained on daily insulin. Despite an initial decline in body weight acutely after pancreatectomy and streptozotocin administration, the mean body weight increased after induction over the approximately 88-day study, indicating that the animals were in good health. CONCLUSION: This stringent porcine model of diabetic induction should be used to assess autograft transplantation safety and efficacy.

Lotus japonicus symRK-14 uncouples the cortical and epidermal symbiotic program.

SYMRK is a leucine-rich-repeat (LRR)-receptor kinase that mediates intracellular symbioses of legumes with rhizobia and arbuscular mycorrhizal fungi. It participates in signalling events that lead to epidermal calcium spiking, an early cellular response that is typically considered as central for intracellular accommodation and nodule organogenesis. Here, we describe the Lotus japonicus symRK-14 mutation that alters a conserved GDPC amino-acid sequence in the SYMRK extracellular domain. Normal infection of the epidermis by fungal or bacterial symbionts was aborted in symRK-14. Likewise, epidermal responses of symRK-14 to bacterial signalling, including calcium spiking, NIN gene expression and infection thread formation, were significantly reduced. In contrast, no major negative effects on the formation of nodule primordia and cortical infection were detected. Cumulatively, our data show that the symRK-14 mutation uncouples the epidermal and cortical symbiotic program, while indicating that the SYMRK extracellular domain participates in transduction of non-equivalent signalling events. The GDPC sequence was found to be highly conserved in LRR-receptor kinases in legumes and non-legumes, including the evolutionarily distant bryophytes. Conservation of the GDPC sequence in nearly one-fourth of LRR-receptor-like kinases in the genome of Arabidopsis thaliana suggests, however, that this sequence might also play an important non-symbiotic function in this plant.