Hedgehog signals inhibit postnatal beta cell neogenesis from adult rat exocrine pancreas in vitro

Abstract

Aims/hypothesis Transdifferentiation of pancreatic exocrine cells into insulin-producing beta cells may represent an important alternative to islets required for diabetes cell therapy. Rat pancreatic acinar cells are known to transdifferentiate into functional beta cells, with recapitulation of several pancreas developmental features. Considering the inhibitory functions of hedgehog signalling in early and mid-stage pancreatic development, we questioned whether it also operates in transdifferentiating acinar cells and whether its modulation would influence postnatal beta cell neogenesis in vitro. Methods Rat exocrine cells were precultured in suspension for 4 days and then incubated with EGF and leukaemia inhibitory factor (LIF) for 72 h. The hedgehog signalling pathway was modulated during this, and its effects analysed by RT-PCR, immunocytochemistry and western blot. Results Our data indicate induction of Dhh and Ihh, but not Shh, expression during acinar cell culture, resulting in activation of hedgehog targets (Ptc1, Gli1). Exposure of the metaplastic cells to EGF and LIF induced beta cell differentiation without affecting endogenous hedgehog activity. Whereas blocking endogenous hedgehog only slightly increased beta cell neogenesis, exposure to embryoid body-conditioned medium activated hedgehog signalling as well as other pathways such as Notch, resulting in severe blockade of beta cell neogenesis. Interestingly, this effect was partially rescued by treatment with the hedgehog inhibitor, 3-keto-N-(aminoethylaminocaproyl-dihydrocinnamoyl)-cyclopamine (KAADcyclopamine), alone. Conclusions/interpretation We report here Dhh/Ihh-dependent activation of hedgehog targets during pancreatic exocrine cell metaplasia in vitro and a persistent inhibitory function of hedgehog signalling in a model of postnatal beta cell differentiation.

Immuno-Isolation of Pancreatic Islet Allografts Using Pegylated Nanotherapy Leads to Long-Term Normoglycemia in Full MHC Mismatch Recipient Mice

“…For example, we anticipate nanotherapeutic delivery of factors including LIF plus EGF, known to synergise in β cell transdifferentiation from pancreatic exocrine cells [24], [25]. Exocrine pancreas as a source for β cell neogenesis might also be promoted by targeted delivery of inhibitors of the hedgehog signaling pathway based on the recent findings [27].…”

Human β-cell regeneration

“…Lineage tracing with Ptf1a, expressed only in acinar cells in adulthood, found that some exocrine cells expressed β-cell markers after pancreatic duct ligation; exocrine-to-endocrine conversion was promoted by prior elimination of endogenous β-cells with streptozotocin [61 ▪ ]. Overexpression of Pdx1, Ngn3, and MafA in a transformed exocrine cell line suppressed exocrine markers and increased endocrine markers [62]; on the contrary, Hedgehog signaling inhibited exocrine to β-cell transformation [63]. Remarkably, deletion of FoxO1 in Ngn3+ cells resulted in glucose-responsive insulin-secreting cells in the gut, which expanded in number when pancreatic β-cells were eliminated using streptozotocin [64].…”

Congenital Hyperinsulinism and Cochlear Hypoplasia in a Rare Case of Pallister-Hall Syndrome

“…GLI3 is implicated in the cochlear abnormality and the digital abnormalities described in PHS. We have not been able to establish the exact genetic link between GLI3 mutation and CHI, but SHH pathways that are modified by GLI3 have been implicated in the early development of the pancreas as well as subsequent insulin activity in pancreatic β cells [19,20]. Further studies are needed to establish the exact genetic link between GLI3 mutation and CHI.…”