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Aims/hypothesis: As current islet-transplantation protocols suffer from significant graft loss and dysfunction, strategies to sustain the long-term benefits of this therapy are required. Rapid and adequate oxygen and nutrient delivery by blood vessels improves islet engraftment and function. The present report evaluated a potentially beneficial effect of adult human blood outgrowth endothelial cells (BOEC) on islet graft vascularisation and function. Methods: Human BOEC, 5 × 10, were co-transplanted with a rat marginal-islet graft under the kidney capsule of hyperglycaemic NOD severe combined immunodeficiency (SCID) mice, and the effect on metabolic outcome was evaluated. Results: Although vessel density remained unaffected, co-transplantation of islets with BOEC resulted in a significant and specific improvement of glycaemia and increased plasma C-peptide. Moreover, in contrast to control mice, BOEC recipients displayed reduced beta cell death and increases in body weight, beta cell proliferation and graft-vessel and beta cell volume. In vivo cell tracing demonstrated that BOEC remain at the site of transplantation and do not expand. The potential clinical applicability was underscored by the observed metabolic benefit of co-transplanting islets with BOEC derived from a type 1 diabetes patient. Conclusions/interpretation: The present data support the use of autologous BOEC in translational studies that aim to improve current islet-transplantation protocols for the treatment of brittle type 1 diabetes. [ABSTRACT FROM AUTHOR]

Aims/hypothesis: IL-6 was recently shown to control alpha cell expansion. As beta cells expand following partial pancreatic-duct ligation (PDL) in adult mice, we investigated whether PDL also causes alpha cells to expand and whether IL-6 signalling is involved. As alpha cells can reprogramme to beta cells in a number of beta cell (re)generation models, we examined whether this phenomenon also exists in PDL pancreas., Methods: Total alpha cell volume, alpha cell size and total glucagon content were evaluated in equivalent portions of PDL- and sham-operated mouse pancreases. Proliferation of glucagon(+) cells was assessed by expression of the proliferation marker Ki67. Inter-conversions between alpha and beta cells were monitored in transgenic mice with conditional cell-type-specific labelling. The role of IL-6 in regulating alpha cell proliferation was evaluated by in situ delivery of an IL-6-inactivating antibody., Results: In response to PDL surgery, alpha cell volume in the ligated tissue was increased threefold, glucagon content fivefold and alpha cell size by 10%. Activation of alpha cell proliferation in PDL pancreas required IL-6 signalling. A minor fraction of alpha cells derived from beta cells, whereas no evidence for alpha to beta cell conversion was obtained., Conclusions/interpretation: In PDL-injured adult mouse pancreas, new alpha cells are generated mainly by IL-6-dependent self-duplication and seldom by reprogramming of beta cells.

Aims/hypothesis: Vascular endothelial growth factor (VEGF) has been recognised by loss-of-function experiments as a pleiotropic factor with importance in embryonic pancreas development and postnatal beta cell function. Chronic, nonconditional overexpression of VEGF-A has a deleterious effect on beta cell development and function. We report, for the first time, a conditional gain-of-function study to evaluate the effect of transient VEGF-A overexpression by adult pancreatic beta cells on islet vasculature and beta cell proliferation and survival, under both normal physiological and injury conditions., Methods: In a transgenicmouse strain, overexpressing VEGF-A in a doxycycline-inducible and beta cell-specific manner, we evaluated the ability of VEGF-A to affect islet vessel density, beta cell proliferation and protection of the adult beta cell mass from toxin-induced injury., Results: Short-term VEGF-A overexpression resulted in islet hypervascularisation, increased beta cell proliferation and protection from toxin-mediated beta cell death, and thereby prevented the development of hyperglycaemia. Extended overexpression of VEGF-A led to impaired glucose tolerance, elevated fasting glycaemia and a decreased beta cell mass., Conclusions/interpretation: Overexpression of VEGF-A in beta cells time-dependently affects glycometabolic control and beta cell protection and proliferation. These data nourish further studies to examine the role of controlled VEGF delivery in (pre)clinical applications aimed at protecting and/or restoring the injured beta cell mass.