Impaired migration and delayed differentiation of pancreatic islet cells in mice lacking EGF-receptors

Pancreatic acini and islets are believed to differentiate from common ductal precursors through a process requiring various growth factors. Epidermal growth factor receptor (EGF-R) is expressed throughout the developing pancreas. We have analyzed here the pancreatic phenotype of EGF-R deficient (−/−) mice, which generally die from epithelial immaturity within the first postnatal week. The pancreata appeared macroscopically normal. The most striking feature of the EGF-R (−/−) islets was that instead of forming circular clusters, the islet cells were mainly located in streak-like structures directly associated with pancreatic ducts. Based on BrdU-labelling, proliferation of the neonatal EGF-R (−/−) beta-cells was significantly reduced (2.6+/−0.4 versus 5.8+/−0.9%, P<0.01) and the difference persisted even at 7–11 days of age. Analysis of embryonic pancreata revealed impaired branching morphogenesis and delayed islet cell differentiation in the EGF-R (−/−) mice. Islet development was analyzed further in organ cultures of E12.5 pancreata. The proportion of insulin-positive cells was significantly lower in the EGF-R (−/−) explants (27+/−6 versus 48+/−8%, P<0.01), indicating delayed differentiation of the beta cells. Branching of the epithelium into ducts was also impaired. Matrix metalloproteinase (MMP-2 and MMP-9) activity was reduced 20% in EGF-R (−/−) late-gestation pancreata, as measured by gelatinase assays. Furthermore, the levels of secreted plasminogen activator inhibitor-1 (PAI-1) were markedly higher, while no apparent differences were seen in the levels of active uPA and tPa between EGF-R (−/−) and wild-type pancreata. Our findings suggest that the perturbation of EGF-R-mediated signalling can lead to a generalized proliferation defect of the pancreatic epithelia associated with a delay in beta cell development and disturbed migration of the developing islet cells as they differentiate from their precursors. Upregulated PAI-1 production and decreased gelatinolytic activity correlated to this migration defect. An intact EGF-R pathway appears to be a prerequisite for normal pancreatic development.

Global profiling of coxsackievirus- and cytokine-induced gene expression in human pancreatic islets

AIMS/HYPOTHESIS

It is thought that enterovirus infections initiate or facilitate the pathogenetic processes leading to type 1 diabetes. Exposure of cultured human islets to cytolytic enterovirus strains kills beta cells after a protracted period, suggesting a role for secondary virus-induced factors such as cytokines.

METHODS

To clarify the molecular mechanisms involved in virus-induced beta cell destruction, we analysed the global pattern of gene expression in human islets. After 48 h, RNA was extracted from three independent human islet preparations infected with coxsackievirus B5 or exposed to interleukin 1beta (50 U/ml) plus interferon gamma (1,000 U/ml), and gene expression profiles were analysed using Affymetrix HG-U133A gene chips, which enable simultaneous analysis of 22,000 probe sets.

RESULTS

As many as 13,077 genes were detected in control human islets, and 945 and 1293 single genes were found to be modified by exposure to viral infection and the indicated cytokines, respectively. Four hundred and eighty-four genes were similarly modified by the cytokines and viral infection.

CONCLUSIONS/INTERPRETATION

The large number of modified genes observed emphasises the complex responses of human islet cells to agents potentially involved in insulitis. Notably, both cytokines and viral infection significantly (p<0.02) increased the expression of several chemokines, the cytokine IL-15 and the intercellular adhesion molecule ICAM-1, which might contribute to the homing and activation of mononuclear cells in the islets during infection and/or an early autoimmune response. The present results provide novel insights into the molecular mechanisms involved in viral- and cytokine-induced human beta cell dysfunction and death.

Mechanisms of coxsackievirus-induced damage to human pancreatic beta-cells

Enteroviruses may be involved in the pathogenesis of insulin-dependent diabetes mellitus, either through direct beta-cell infection or as triggers of autoimmunity. In the present study we investigated the patterns of infection in adult human islet cell preparations (consisting of 56+/-14% beta-cells) by several coxsackieviruses. The cells were infected with prototype strains of coxsackievirus B (CBV) 3, 4, and 5 as well as coxsackievirus A9 (CAV-9). The previously characterized diabetogenic strain of coxsackievirus B4 (CBV-4-E2) was used as a reference. All viruses replicated well in beta-cells, but only CBVs caused cell death. One week after infection, the insulin response of the beta-cells to glucose or glucose plus theophylline was most severely impaired by CBV-3 and CBV-5 infections. CBV-4 also caused significant functional impairment, whereas CAV-9-infected cells responded like uninfected controls. After 2 days of infection, about 40% of CBV-5-infected cells had undergone morphological changes characteristic of pyknosis, i.e. highly distorted nuclei with condensed but intact chromatin. Both mitochondria and plasma membrane were intact in these cells. DNA fragmentation was found in 5.9+/-1.1% of CBV-5-infected beta-cell nuclei (2.1+/-0.3% in controls; P<0.01). CAV-9 infection did not induce DNA fragmentation. One week after infection the majority of infected cells showed characteristics of secondary necrosis. Medium nitrite and inducible nitric oxide synthase messenger ribonucleic acid levels were not significantly up-regulated by CBV infection. These results suggest that several enteroviruses may infect human beta-cells. The infection may result in functional impairment or death of the beta-cell or may have no apparent immediate adverse effects, as shown here for CAV-9. Coxsackie B viruses cause functional impairment and beta-cell death characterized by nuclear pyknosis. Apoptosis appears to play a minor role during a productive CBV infection in beta-cells.

Differentiation and maturation of porcine fetal islet cells in vitro and after transplantation

BACKGROUND

Porcine fetal pancreas is a potential source of beta cells for transplantation. The immaturity of the cells is a problem. We have defined the optimal conditions for in vitro propagation of this tissue before transplantation.

METHODS

Porcine fetal pancreas tissue was obtained for tissue culture at various stages of development. Serum-containing and serum-free media and a variety of potential differentiation factors were tested. In vitro, the numbers of endocrine islet cells and their proliferation were quantified and functional maturity of the beta cells was assessed by perifusion. Growth and maturation of the cells was assessed 3 months after transplantation into nude mice.

RESULTS

Highest beta cell mass was obtained from end-gestational, as compared with early fetal or neonatal, pancreas. Nicotinamide and sodium butyrate effectively increased the insulin content and the number of endocrine cells in culture. In combination, these factors led up to a 90-fold increase in the insulin content of islet-like cell clusters (ICC) as compared with untreated controls. However, a high level of cell death through apoptosis was observed in these maximally stimulated endocrine cells, and they did not survive as grafts when transplanted into nude mice. Instead, a serum-free culture medium containing 10 mM nicotinamide and 0.1 mM isobutylmethylxanthine was found to support both differentiation and proliferation of endocrine cells as loose ICCs. Insulin release from these ICCs was sensitive to glucose. When transplanted under the kidney capsule of normoglycemic nude mice, a high level of beta cell differentiation and function was evident only in the ICCs cultured in the serum-free medium, and in freshly isolated ICCs. When transplanted to hyperglycemic nude recipients, the cells cultured in serum-free medium for 3 weeks reversed hyperglycemia more consistently and rapidly than freshly isolated ICCs.

CONCLUSIONS

Optimal maturation of porcine fetal pancreatic cells is obtained in serum-free medium supplemented with nicotinamide. Butyrate is a potent stimulus for beta cell differentiation but leads to increased apoptotic cell death.

Mechanical and oral antibiotic bowel preparation versus no bowel preparation in right and left colectomy: subgroup analysis of MOBILE trial

BACKGROUND

In retrospective series, mechanical and oral antibiotic bowel preparation (MOABP) has been reported to reduce surgical-site infections (SSIs) after colectomy compared with no bowel preparation (NBP).

METHOD

This was a subgroup analysis of a multicentre randomized trial that included patients scheduled for elective colectomy. The MOABP group underwent mechanical bowel preparation, and took 2 g neomycin and 2 g metronidazole orally during the day before surgery. The NBP group did not undergo bowel preparation. Patients were categorized according to the side of resection (right versus left colectomy), and these subgroups compared for postoperative outcomes.

RESULTS

Among 217 patients undergoing right colectomy (106 in MOABP and 111 in NBP group), SSI was detected in seven (7 per cent) and 10 (9 per cent) patients (odds ratio (OR) 0.71, 95 per cent c.i. 0.26 to 1.95; P = 0.510), anastomotic dehiscence in two (2 per cent) and two (2 per cent) patients (OR 1.05, 0.15 to 7.58; P = 1.000), and the mean(s.d.) Comprehensive Complication Index (CCI) score was 9.4(12.9) and 10.5(18.0) (mean difference -1.09; 95 per cent c.i. -5.29 to 3.11; P = 0.608) in the MOABP and NBP groups respectively. Among 164 patients undergoing left colectomy (84 in MOABP and 80 in NBP group), SSI was detected in five (6 per cent) and eight (10 per cent) patients (OR 0.57, 0.18 to 1.82; P = 0.338), anastomotic dehiscence in four (5 per cent) and five (6 per cent) patients (OR 0.75, 0.19 to 2.90; P = 0.742), and the CCI score was 10.2(13.1) and 6.5(11.0) (mean difference 3.68, -0.06 to 7.42; P = 0.053) in the MOABP and NBP groups respectively.

CONCLUSIONS

MOABP did not decrease the rate of SSI or complications in patients undergoing either right or left colectomy compared with NBP.