Signals from the neural crest regulate beta-cell mass in the pancreas
ABSTRACT Pancreatic islet cells and neurons share common functions and similar ontogenies, but originate in different germ layers. To determine whether ectoderm-derived cells contribute instructive signals to the developing endoderm-derived pancreas, we defined the chronology of migration and differentiation of neural crest cells in the pancreas, and tested their role in the development of the islets. The homeodomain transcription factor Phox2b marks the neural precursors from the neural crest that colonize the gut to form the enteric nervous system. In the embryonic mouse pancreas, we found Phox2b expressed briefly together with Sox10 along the epithelial-mesenchymal border at E12.5 in cells derived from the neural crest. Downregulation of Phox2b shortly thereafter was dependent upon Nkx2.2 expressed in the adjacent pancreatic epithelium. In Phox2b(-/-) embryos, neurons and glia did not develop in the pancreas, and Nkx2.2 expression was markedly upregulated in the epithelium. In addition, the number and replication rate of insulin-expressing beta-cells increased in the Phox2b(-/-) mice. We conclude that, during pancreatic development, Phox2b and Nkx2.2 form a non-cell-autonomous feedback loop that links the neural crest with the pancreatic epithelium, regulates the size of the beta-cell population, and thereby impacts insulin-secretory capacity and energy homeostasis.
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- "Homeobox TFs are known to be involved in embryonic and tissue developmental processes including β-cell development (Jonsson et al., 1994; Harrison et al., 1999; Nekrep et al., 2008). However, except for the mature onset of diabetes gene PDX1 (Fajans et al., 2001) and the common T2D-associated loci HHEX1 and ALX4 (Sladek et al., 2007), the inferred -9 homeobox factors have not been implicated in T2D pathogenesis. "
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- "It is possible that co-transplantation of islet cells with neural crest stem cells (NCSCs) will promote an improved islet transplantation outcome. Indeed, recent studies have demonstrated that NCSCs have an important role in beta-cell differentiation by regulating beta-cell mass during development . It has also been observed that embryonic dorsal root ganglia affect insulin secretion in co-cultured islets , that co-cultured islets and NCSCs have mutual beneficial effects in vitro , and that co-transplantation of NCSC-derived neurospheres with islets induces proliferation and promotes function of transplanted beta-cells . "
ABSTRACT: Transplantation of pancreatic islets to Type 1 diabetes patients is hampered by inflammatory reactions at the transplantation site leading to dysfunction and death of insulin producing beta-cells. Recently we have shown that co-transplantation of neural crest stem cells (NCSCs) together with the islet cells improves transplantation outcome. The aim of the present investigation was to describe in vitro interactions between NCSCs and insulin producing beta-TC6 cells that may mediate protection against cytokine-induced beta-cell death. Beta-TC6 and NCSC cells were cultured either alone or together, and either with or without cell culture inserts. The cultures were then exposed to the pro-inflammatory cytokines IL-1β and IFN-γ for 48 hours followed by analysis of cell death rates (flow cytometry), nitrite production (Griess reagent), protein localization (immunofluorescence) and protein phosphorylation (flow cytometry). We observed that beta-TC6 cells co-cultured with NCSCs were protected against cytokine-induced cell death, but not when separated by cell culture inserts. This occurred in parallel with (i) augmented production of nitrite from beta-TC6 cells, indicating that increased cell survival allows a sustained production of nitric oxide; (ii) NCSC-derived laminin production; (iii) decreased phospho-FAK staining in beta-TC6 cell focal adhesions, and (iv) decreased beta-TC6 cell phosphorylation of ERK(T202/Y204), FAK(Y397) and FAK(Y576). Furthermore, co-culture also resulted in cadherin and beta-catenin accumulations at the NCSC/beta-TC6 cell junctions. Finally, the gap junction inhibitor carbenoxolone did not affect cytokine-induced beta-cell death during co-culture with NCSCs. In summary, direct contacts, but not soluble factors, promote improved beta-TC6 viability when co-cultured with NCSCs. We hypothesize that cadherin junctions between NCSC and beta-TC6 cells promote powerful signals that maintain beta-cell survival even though ERK and FAK signaling are suppressed. It may be that future strategies to improve islet transplantation outcome may benefit from attempts to increase beta-cell cadherin junctions to neighboring cells.PLoS ONE 04/2013; 8(4):e61828. DOI:10.1371/journal.pone.0061828 · 3.23 Impact Factor
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- "Functioning as a trophic factor in plants, 5-HT signaled in even the most primitive nervous systems to regulate the primitive energy metabolism systems , . Considering that pancreatic islet cells and neurons share common functions and similar ontogenies , it is not surprising that the serotonergic nervous system might regulate pancreatic islet function, to form an intricate energy metabolism regulatory system with the effect on hypothalamus. Our data strongly suggest that the 5-HT system is important for metabolic control, though much remains to be understood about the function of the 5-HT system in energy metabolism, including the specific roles of each of the 5-HT receptor subtypes, and the nuances of the effector pathways. "
ABSTRACT: Type 2 diabetes mellitus (T2DM) describes a group of metabolic disorders characterized by defects in insulin secretion and insulin sensitivity. Insulin secretion from pancreatic β-cells is an important factor in the etiology of T2DM, though the complex regulation and mechanisms of insulin secretion from β-cells remains to be fully elucidated. High plasma levels of serotonin (5-hydroxytryptamine; 5-HT) have been reported in T2DM patients, though the potential effect on insulin secretion is unclear. However, it is known that the 5-HT receptor 2C (5-HT(2C)R) agonist, mCPP, decreases plasma insulin concentration in mice. As such, we aimed to investigate the expression of the 5-HT(2C)R in pancreatic islets of diabetic mice and the role of 5-HT(2C)R signaling in insulin secretion from pancreatic β-cells. We found that 5-HT(2C)R expression was significantly increased in pancreatic islets of db/db mice. Furthermore, treatment with a 5-HT(2C)R antagonist (SB242084) increased insulin secretion from pancreatic islets isolated from db/db mice in a dose-dependent manner, but had no effect in islets from control mice. The effect of a 5-HT(2C)R agonist (mCPP) and antagonist (SB242084) were further studied in isolated pancreatic islets from mice and Min-6 cells. We found that mCPP significantly inhibited insulin secretion in Min-6 cells and isolated islets in a dose-dependent manner, which could be reversed by SB242084 or RNA interference against 5-HT(2C)R. We also treated Min-6 cells with palmitic acid for 24 h, and found that the expression of 5-HT(2C)R increased in a dose-dependent manner; furthermore, the inhibition of insulin secretion in Min-6 cells induced by palmitic acid could be reversed by SB242084 or RNA interference against 5-HT(2C)R. Taken together, our data suggests that increased expression of 5-HT(2C)R in pancreatic β-cells might inhibit insulin secretion. This unique observation increases our understanding of T2DM and suggests new avenues for potential treatment.PLoS ONE 01/2013; 8(1):e54250. DOI:10.1371/journal.pone.0054250 · 3.23 Impact Factor