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To understand causes of developmental abnormalities of the pancreas, it is essential to understand its normal embryonic development. Current understanding of the development of pancreatic exocrine tissue is that it develops solely from embryonic epithelium, while the role of the surrounding mesenchyme is to signal to this epithelium and form connective tissue. Recent work in our laboratory has shown that pancreatic bud mesenchyme can contribute cells to islets during embryonic development. However, no published studies have investigated in detail whether mesenchyme contributes cells to the exocrine structures of the pancreas. The aim of this study was to investigate whether cells from foregut mesenchyme can contribute to pancreatic acini during embryonic development. Chick-quail chimera recombinant organs were constructed using pancreatic epithelium and mesenchyme from either the pancreas (n=12) or stomach (n=25). These were cultured for 7 days in 3-D collagen gels. The resulting specimens were analysed using morphological criteria and fluorescent immunocytochemistry against pancreatic amylase, insulin, and the quail-specific nucleolar antigen QCPN. Two independent observers determined the origins of acini as either solely epithelial, solely mesenchymal, or of mixed origin. Results are expressed as percentages of total acini identified in each group. Statistical analysis was performed using chi(2) tests (P

Current interest in the potential use of pancreatic stem-cells in the treatment of insulin dependent diabetes mellitus has led to increased research into normal pancreatic development. Pancreatic organogenesis involves branching morphogenesis of undifferentiated epithelium within surrounding mesenchyme. Current understanding is that the pancreatic islets develop exclusively from the epithelium of the embryonic buds. However, a cellular contribution to islets by mesenchyme has not been conclusively excluded. We present evidence that the mesenchyme of both the dorsal pancreatic bud and stomach rudiment make a substantial contribution of cells to islets during development in a three-dimensional avian model. These data suggest that mesenchyme can be a source not only of signals but also of cells for the definitive epithelia, making pancreatic organogenesis more akin to that of the kidney than to other endodermal organs. This raises the possibility for the use of mesenchymal cells as stem- or progenitor- cells for islet transplantation.

SummaryGenome-wide association studies have revealed numerous risk loci associated with diverse diseases. However, identification of disease-causing variants within association loci remains a major challenge. Divergence in gene expression due to cis-regulatory variants in noncoding regions is central to disease susceptibility. We show that integrative computational analysis of phylogenetic conservation with a complexity assessment of co-occurring transcription factor binding sites (TFBS) can identify cis-regulatory variants and elucidate their mechanistic role in disease. Analysis of established type 2 diabetes risk loci revealed a striking clustering of distinct homeobox TFBS. We identified the PRRX1 homeobox factor as a repressor of PPARG2 expression in adipose cells and demonstrate its adverse effect on lipid metabolism and systemic insulin sensitivity, dependent on the rs4684847 risk allele that triggers PRRX1 binding. Thus, cross-species conservation analysis at the level of co-occurring TFBS provides a valuable contribution to the translation of genetic association signals to disease-related molecular mechanisms.

Both pancreatic cysts and pancreatic tumors rarely occur in childhood. However, when encountered they can present a diagnostic and therapeutic challenge to the pediatric surgeon. The aim of this review is to discuss the different types of pancreatic cysts and tumours that may be encountered in the pediatric population, to note the modes available for their diagnosis, and to outline treatment options.

Background Unilateral neck exploration for sporadic parathyroid adenomas remains a contentious policy. The morbidity is lower than for bilateral surgery, but the long-term outcome may be inferior. Methods The results of a policy of unilateral neck exploration for primary hyperparathyroidism based on preoperative localization are reviewed. Results Over a 10-year period, 89 patients were operated on, 57 undergoing unilateral neck exploration. Unilateral neck exploration significantly reduced operative time ( P P = 0.021). Over a mean biochemical follow-up of 38 months, recurrent hypercalcaemia occurred in 6% of patients, including 3.5% of those undergoing unilateral neck exploration, an additional 10% of patients were normocalcaemic with an inappropriately elevated parathormone level. Conclusions A policy of unilateral neck exploration can achieve comparable long-term results to more extensive bilateral surgery.

AIMS/HYPOTHESIS: Rapamycin, part of the immunosuppressive regimen of the Edmonton protocol, has been shown to inhibit vascular endothelial growth factor (VEGF) production and VEGF-mediated survival signalling in tumour cell lines. This study investigates the survival-promoting activities of VEGF in human islets and the effects of rapamycin on islet viability. MATERIALS AND METHODS: Levels of VEGF and its receptors in isolated human islets and whole pancreas was determined by western blotting and immunostaining. Islet viability following VEGF or immunosuppressive drug treatment was determined using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Islet VEGF release was measured by ELISA. Mouse islets infected with an adenovirus expressing the gene for VEGF were transplanted syngeneically into streptozotocin-induced diabetic mice, with blood glucose levels measured three times per week. RESULTS: Isolated human islets produced multiple isoforms of VEGF and VEGF receptors 1, 2 and 3 and the coreceptor neuropilin 1. Exogenous VEGF (10 ng/ml) prevented human islet death induced by serum starvation, which suggests that VEGF can act as a survival factor for human islets. Transplantation of mouse islets infected with a VEGF-expressing adenovirus in a syngeneic model, improved glycaemic control at day 1 post-transplantation (p < 0.05). Rapamycin at 10 and 100 ng/ml significantly reduced islet VEGF release (by 37 +/- 4% and 43 +/- 6%, respectively; p < 0.05) and at 100 ng/ml reduced islet viability (by 36 +/- 9%) and insulin release (by 47 +/- 7%, all vs vehicle-treated controls; p < 0.05). Tacrolimus had no effect on islet VEGF release or viability. CONCLUSIONS/INTERPRETATION: Our data suggest that rapamycin may have deleterious effects on islet survival post-transplantation, both through a direct effect on islet viability and indirectly through blockade of VEGF-mediated revascularisation.

Background/Purpose Potential for curative stem-cell treatments of juvenile-onset diabetes has focussed research into pancreatic islet development. Islets were previously thought to originate solely from embryonic pancreatic epithelium, but we have demonstrated that islets can originate from mesenchyme, that is, islet mesenchyme-to-epithelial transition. The aim of this study was to establish the competence of foregut mesenchyme during mesenchymal islet development. Methods Embryonic chick pancreatic epithelium of gestational stage Hamburger-Hamilton (HH) 22 ( J Morphol . 1951;88:49-92) was combined with quail stomach mesenchyme of increasing gestation (stage HH22 [n = 6], HH26 [n = 6], HH28 [n = 4], or HH31 [n = 6]). Recombinants were cultured and analysed by immunocytochemistry for coexpression of insulin and quail-specific antigen to determine the embryonic origin of islets. Results Recombinants constructed using stage HH22 mesenchyme yielded 34 islets, of which 35% were mesenchymal. However, when recombinants were constructed using stage HH26 mesenchyme, 24% of 25 islets were mesenchymal. When using mesenchyme, 13% of 15 islets were mesenchymal. All islets (n = 35) in recombinants constructed using stage HH31 mesenchyme were epithelial derived. Islet mesenchyme-to-epithelial transition diminished significantly with increasing mesenchymal gestational stage ( P = .002). Conclusions These data show foregut mesenchyme is competent to form islets between stages HH22 and HH28. Developmental competence of foregut mesenchyme in islet mesenchyme-to-epithelial transition diminishes as gestation increases. This may have important implications for identifying stem cells to treat juvenile-onset diabetes.

Stem or progenitor cells are a promising potential alternative source of pancreatic islets for transplantation in the treatment of juvenile-onset diabetes. However, to derive islets from such cells, it is important to elucidate the mechanisms of normal pancreatic development. Previous work in our laboratory has shown that, contrary to previous thinking, pancreatic mesenchyme when combined with pancreatic epithelium can contribute cells to islets. However, the signals and role of individual tissues involved in this mesenchyme-to-epithelial transition (MET) have yet to be elucidated. The aim of this study was to investigate whether MET can occur in the absence of pancreatic epithelium. Chick and quail eggs were incubated for 4 days and the dorsal pancreatic buds and stomach rudiments were microdissected. Mesenchyme and epithelium of the organ rudiments were separated after collagenase treatment. Separated pancreatic mesenchyme were cultured alone and in combination with stomach (nonpancreatic). After 7 days of culture, the specimens were analysed using immunohistochemistry for quail-specific nucleolar antigen (QCPN), insulin, and islet precursor cell marker (ISL-1). Pancreatic mesenchyme when cultured in the absence of epithelium did not differentiate into islets, but differentiated into fibroblast-like cells. When pancreatic mesenchyme were cultured in combination with stomach epithelium, there was no evidence of mesenchymally derived islets. We have demonstrated that pancreatic mesenchyme require pancreatic epithelium to differentiate into islet cells. These findings further increase our understanding of normal pancreatic islet development and may help to elucidate the molecular mechanisms of MET in islet development.

Persistent hyperinsulinemic hypoglycemia of infancy is caused by inappropriate and excessive secretion of insulin. Although the disease is rare in outbred communities (approximately 1 case per 50,000 persons), the incidence is approximately 1 per 2500 in inbred Arabic communities in which there is a familial (autosomal recessive) form of the disease. The disease most commonly presents with severe hypoglycemia a few hours after birth, although some cases present after several weeks or months. Some patients have a response to treatment with diazoxide or somatostatin, but others require partial pancreatectomy to control the hyperinsulinism.1–3 It has recently been suggested2, . . .

Persistent hyperinsulinemic hypoglycemia of infancy (PHHI) is a disorder of childhood associated with inappropriate hypersecretion of insulin by the pancreas. The pathogenesis of the condition has hitherto remained controversial. We show here that insulin-secreting cells from a homogeneous group of five infants with PHHI lack ATP-sensitive K+ channel (KATP) activity. As a consequence, PHHI beta-cells are spontaneously electrically active with high basal cytosolic Ca2+ concentrations due to Ca2+ influx. Our findings define the pathogenesis of this disease as a novel K+ channel disorder.