Transforming growth factor-beta (TGF-beta) superfamily signaling has been implicated in many developmental processes, including pancreatic development. Previous studies are conflicting with regard to an exact role for TGF-beta signaling in various aspects of pancreatic organogenesis. Here we have investigated the role of TGF-beta isoform signaling in embryonic pancreas differentiation and lineage selection. The TGF-beta isoform receptors (RI, RII and ALK1) were localized mainly to both the pancreatic epithelium and mesenchyme at early stages of development, but then with increasing age localized to the pancreatic islets and ducts. To determine the specific role of TGF-beta isoforms, we functionally inactivated TGF-beta signaling at different points in the signaling cascade. Disruption of TGF-beta signaling at the receptor level using mice overexpressing the dominant-negative TGF-beta type II receptor showed an increase in endocrine precursors and proliferating endocrine cells, with an abnormal accumulation of endocrine cells around the developing ducts of mid-late stage embryonic pancreas. This pattern suggested that TGF-beta isoform signaling may suppress the origination of secondary transition endocrine cells from the ducts. Secondly, TGF-beta isoform ligand inhibition with neutralizing antibody in pancreatic organ culture also led to an increase in the number of endocrine-positive cells. Thirdly, hybrid mix-and-match in vitro recombinations of transgenic pancreatic mesenchyme and wild-type epithelium also led to increased endocrine cell differentiation, but with different patterns depending on the directionality of the epithelial-mesenchymal signaling. Together these results suggest that TGF-beta signaling is important for restraining the growth and differentiation of pancreatic epithelial cells, particularly away from the endocrine lineage. Inhibition of TGF-beta signaling in the embryonic period may thus allow pancreatic epithelial cells to progress towards the endocrine lineage unchecked, particularly as part of the secondary transition of pancreatic endocrine cell development. TGF-beta RII in the ducts and islets may normally serve to downregulate the production of beta cells from embryonic ducts.

A key goal of cellular engineering is to manipulate progenitor cells to become ␤-cells, allowing cell replacement therapy to cure diabetes mellitus. As a paradigm for cell engineering, we have studied the molecular mechanisms by which AR42J cells become ␤-cells. Bone morphogenetic proteins (BMPs), implicated in a myriad of developmental pathways, have not been well studied in insulin-positive differentiation. We found that the canonical intracellular mediators of BMP signaling, Smad-1 and Smad-8, were significantly elevated in AR42J cells undergoing insulin-positive differentiation in response to exendin-4 treatment, suggesting a role for BMP signaling in ␤-cell formation. Similarly, endogenous BMP-2 ligand and ALK-1 receptor (activin receptor-like kinase-1; known to activate Smads 1 and 8) mRNAs were specifically up-regulated in exendin-4-treated AR42J cells. Surprisingly, Smad-1 and Smad-8 levels were suppressed by the addition of BMP-soluble receptor inhibition of BMP ligand binding to its receptor. Here, insulin-positive differentiation was also ablated. BMP-2 ligand antisense also strongly inhibited Smad-1 and Smad-8 expression, again with the abolition of insulin-positive differentiation. These results demonstrate a previously unrecognized key role for BMP signaling in mediating insulin-positive differentiation through the intracellular Smad signaling pathway. In short, BMP signaling may represent a novel downstream target of exendin-4 (glucagon-like peptide 1) signaling and potentially serve as an upstream regulator of transforming growth factor-␤ isoform signaling to differentiate the acinarlike AR42J cells into insulin-secreting cells.Type 1 diabetes is an insulin deficiency state due to pancreatic destruction of ␤-cells caused by autoimmunity. Several approaches to treat diabetes are being pursued, such as islet cell transplantation, pancreas transplantation, and genetic manipulation. However, a key alternative strategy is cellular engineering to manipulate progenitor cells to become ␤-cells, allowing cellular therapy to cure diabetes. As a paradigm for cell engineering, we have used exendin-4 treatment of AR42J cells, a fairly plastic acinar cell carcinoma-derived cell line, as a model for studying the role of bone morphogenetic protein (BMP) 2 signaling in the induction of insulin-positive differentiation. Exendin-4, a peptide from Helodermatidae venom, is a novel insulinotropic agent and a long acting analogue of glucagon-like peptide-1 (GLP-1). It interacts with endocrine pancreatic islet GLP-1 receptors, inducing a stimulatory effect on insulin secretion. Over the past few decades significant progress has been made in our understanding of the biological function of BMPs, which have been found to regulate a myriad of developmental and differentiation process in the embryo, including epithelial-mesenchymal interactions, cell fate specification, dorsoventral patterning, and apoptosis as well as the secretion of extracellular matrix components (1-5).BMPs are one of the multifunctional cytokines from...

Our results suggest that laparoscopic injection of Db into the IHS is simple, safe, reliable, virtually scarless, and may be a reasonable alternative to standard open surgical inguinal hernia repair.

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Our data suggest that patients with PDA-CCAM may be observed safely until they become symptomatic or changes in size are observed radiologically.

Epithelial-mesenchymal interactions are crucial for the proper development of many organs, including the pancreas. Within the pancreas, the ducts are thought to harbor stem/progenitor cells, and possibly to give rise to pancreatic ductal carcinoma. Little is known about the mechanism of formation of pancreatic ducts in the embryo. Pancreatic mesenchyme contains numerous soluble factors which help to sustain the growth and differentiation of exocrine and endocrine structures. Here, we report that one such morphoregulatory mesenchymal protein, epimorphin, plays an important role during pancreatic ductal proliferation and differentiation. We found that epimorphin is expressed in pancreatic mesenchyme during early stages of development, and at mesenchymal-epithelial interfaces surrounding the ducts at later stages. Strong upregulation of epimorphin expression was seen during in vitro pancreatic duct differentiation. Similarly, in vitro pancreatic duct formation was inhibited by a neutralizing antibody against epimorphin, whereas addition of recombinant epimorphin partially rescued duct formation. Together, our study demonstrates the role of epimorphin in pancreatic ductal morphogenesis.

We conclude that TGF-beta isoforms have a specific synergistic role with GLP-1 pathway signaling in early pancreatic development, toward endocrine differentiation and away from acinar differentiation.