Epidermal Growth Factor Receptor Signaling Regulates ß Cell Proliferation in Adult Mice.

A thorough understanding of the signaling pathways involved in the regulation of ß cell proliferation is an important initial step in restoring ß cell mass in the diabetic patient. Here, we show that epidermal growth factor receptor 1 (EGFR) was significantly up-regulated in the islets of C57BL/6 mice after 50% partial pancreatectomy (PPx), a model for workload-induced ß cell proliferation. Specific deletion of EGFR in the ß cells of adult mice impaired ß cell proliferation at baseline and after 50% PPx, suggesting that the EGFR signaling pathway plays an essential role in adult ß cell proliferation. Further analyses showed that ß cell-specific depletion of EGFR resulted in impaired expression of cyclin D1 and impaired suppression of p27 after PPx, both of which enhance ß cell proliferation. These data highlight the importance of EGFR signaling and its downstream signaling cascade in postnatal ß cell growth.

Improvements to bead-based oligonucleotide ligation SNP genotyping assays.

We describe a bead-based, multiplexed, oligonucleotide ligation assay (OLA) performed on the Luminex flow cytometer. Differences between this method and those previously reported include the use of far fewer beads and the use of a universal oligonucleotide for signal detection. These innovations serve to significantly reduce the cost of the assay, while maintaining robustness and accuracy. Comparisons are made between the Luminex OLA and both pyrosequencing and direct sequencing. Experiments to assess conversion rates, call rates, and concordance across technical replicates are also presented.

SMAD3/Stat3 Signaling Mediates ß-Cell Epithelial-Mesenchymal Transition in Chronic Pancreatitis-Related Diabetes.

Many patients with chronic pancreatitis develop diabetes (chronic pancreatitis-related diabetes [CPRD]) through an undetermined mechanism. Here we used long-term partial pancreatic duct ligation (PDL) as a model to study CPRD. We found that long-term PDL induced significant ß-cell dedifferentiation, followed by a time-dependent decrease in functional ß-cell mass-all specifically in the ligated tail portion of the pancreas (PDL-tail). High levels of transforming growth factor ß1 (TGFß1) were detected in the PDL-tail and were mainly produced by M2 macrophages at the early stage and by activated myofibroblasts at the later stage. Loss of ß-cell mass was then found to result from TGFß1-triggered epithelial-mesenchymal transition (EMT) by ß-cells, rather than resulting directly from ß-cell apoptosis. Mechanistically, TGFß1-treated ß-cells activated expression of the EMT regulator gene Snail in a SMAD3/Stat3-dependent manner. Moreover, forced expression of forkhead box protein O1 (FoxO1), an antagonist for activated Stat3, specifically in ß-cells ameliorated ß-cell EMT and ß-cell loss and prevented the onset of diabetes in mice undergoing PDL. Together, our data suggest that chronic pancreatitis may trigger TGFß1-mediated ß-cell EMT to lead to CPRD, which could substantially be prevented by sustained expression of FoxO1 in ß-cells.

PNA lectin for purifying mouse acinar cells from the inflamed pancreas.

Better methods for purifying human or mouse acinar cells without the need for genetic modification are needed. Such techniques would be advantageous for the specific study of certain mechanisms, such as acinar-to-beta-cell reprogramming and pancreatitis. Ulex Europaeus Agglutinin I (UEA-I) lectin has been used to label and isolate acinar cells from the pancreas. However, the purity of the UEA-I-positive cell fraction has not been fully evaluated. Here, we screened 20 widely used lectins for their binding specificity for major pancreatic cell types, and found that UEA-I and Peanut agglutinin (PNA) have a specific affinity for acinar cells in the mouse pancreas, with minimal affinity for other major pancreatic cell types including endocrine cells, duct cells and endothelial cells. Moreover, PNA-purified acinar cells were less contaminated with mesenchymal and inflammatory cells, compared to UEA-I purified acinar cells. Thus, UEA-I and PNA appear to be excellent lectins for pancreatic acinar cell purification. PNA may be a better choice in situations where mesenchymal cells or inflammatory cells are significantly increased in the pancreas, such as type 1 diabetes, pancreatitis and pancreatic cancer.

Transient Suppression of TGFß Receptor Signaling Facilitates Human Islet Transplantation.

Although islet transplantation is an effective treatment for severe diabetes, its broad application is greatly limited due to a shortage of donor islets. Suppression of TGFß receptor signaling in ß-cells has been shown to increase ß-cell proliferation in mice, but has not been rigorously examined in humans. Here, treatment of human islets with a TGFß receptor I inhibitor, SB-431542 (SB), significantly improved C-peptide secretion by ß-cells, and significantly increased ß-cell number by increasing ß-cell proliferation. In addition, SB increased cell-cycle activators and decreased cell-cycle suppressors in human ß-cells. Transplantation of SB-treated human islets into diabetic immune-deficient mice resulted in significant improvement in blood glucose control, significantly higher serum and graft insulin content, and significantly greater increases in ß-cell proliferation in the graft, compared with controls. Thus, our data suggest that transient suppression of TGFß receptor signaling may improve the outcome of human islet transplantation, seemingly through increasing ß-cell number and function.