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Regulatory proteins have been identified in embryonic development of the endocrine pancreas. It is unknown whether these factors can also play a role in the formation of pancreatic endocrine cells from postnatal nonendocrine cells. The present study demonstrates that adult human pancreatic duct cells can be converted into insulin-expressing cells after ectopic, adenovirus-mediated expression of the class B basic helix-loop-helix factor neurogenin 3 (ngn3), which is a critical factor in embryogenesis of the mouse endocrine pancreas. Infection with adenovirus ngn3 (Adngn3) induced gene and/or protein expression of NeuroD/β2, Pax4, Nkx2.2, Pax6, and Nkx6.1, all known to be essential for β-cell differentiation in mouse embryos. Expression of ngn3 in adult human duct cells induced Notch ligands Dll1 and Dll4 and neuroendocrine- and β-cell–specific markers: it increased the percentage of synaptophysin- and insulin-positive cells 15-fold in ngn3-infected versus control cells. Infection with NeuroD/β2 (a downstream target of ngn3) induced similar effects. These data indicate that the Delta-Notch pathway, which controls embryonic development of the mouse endocrine pancreas, can also operate in adult human duct cells driving them to a neuroendocrine phenotype with the formation of insulin-expressing cells.

Acute kidney injury is followed by regeneration of damaged renal tubular epithelial cells. The purpose of this study was to test the hypothesis that renal stem cells exist in the adult kidney and participate in the repair process. A unique population of cells that behave in a manner that is consistent with a renal stem cell were isolated from rat kidneys and were termed multipotent renal progenitor cells (MRPC). Features of these cells include spindle-shaped morphology; self-renewal for >200 population doublings without evidence for senescence; normal karyotype and DNA analysis; and expression of vimentin, CD90 (thy1.1), Pax-2, and Oct4 but not cytokeratin, MHC class I or II, or other markers of more differentiated cells. MRPC exhibit plasticity that is demonstrated by the ability of the cells to be induced to express endothelial, hepatocyte, and neural markers by reverse transcriptase-PCR and immunohistochemistry. The cells can differentiate into renal tubules when injected under the capsule of an uninjured kidney or intra-arterially after renal ischemia-reperfusion injury. Oct4 expression was seen in some tubular cells in the adult kidney, suggesting these cells may be candidate renal stem cells. It is proposed that MRPC participate in the regenerative response of the kidney to acute injury.

Regeneration, or neogenesis, of beta cells in adult pancreas is an important research issue because it could find applications in the restoration of the normal beta-cell mass in diabetic patients. In vitro neogenesis might be a means of generating additional beta cells intended for transplantation, as the number of beta cells that can be isolated from organ donors is very limited. Neogenesis can be induced in vivo in several ways [1] but the identity of the beta-cell precursors is not clear. Several lines of evidence suggest that, in addition to duct cells, exocrine acinar cells could be able to transdifferentiate into beta cells [2]. In several experimental models and pathological conditions, islet neogenesis is accompanied by the transformation of the normal exocrine tissue into ductal complexes, a process called acinoductal metaplasia. This is seen in the model of pancreatic duct ligation [3], transforming growth factor-alpha transgenic mice [4,5] and interferon-gamma transgenic mice [6]. Islet neogenesis has also been observed in associ- Diabetologia (2000) Abstract Aims/hypothesis. In adult pancreatic regeneration models exocrine acini are found to transdifferentiate to duct-like complexes. This has also been associated with the formation of new endocrine islet cells. We aimed to establish an in vitro model in which this transdifferentiation process is characterised and can be modulated. Methods. Purified rat pancreatic acini were cultured in suspension. Differentiation was analysed by immunocytochemistry, electron microscopy, western blotting and RT-PCR.Results. During culture acinar cells directly transdifferentiated without dividing, the cells lost their acinar phenotype and started to express cytokeratins 20 and 7 and fetal liver kinase-1 (Flk-1) receptors for vascular endothelial growth factor. Expression of the acinar pancreatic exocrine transcription factor (PTF-1) remained and the pancreatic duodenal homeoboxcontaining transcription factor (PDX-1) was induced. When transdifferentiation was completed, the cells started to express protein gene product 9.5, a panneuroendocrine marker. By combining these features, the transdifferentiated cells show similar characteristics to precursor cells during active beta-cell neogenesis. We were able to modulate the differentiation state by addition of nicotinamide or sodium butyrate, agents which are known to stimulate endocrine differentiation in other models. Conclusion/interpretation. Here, we present an in vitro system in which the cellular differentiation of putative pancreatic endocrine precursor cells and their PDX-1 expression can be modulated, thereby providing a possible model for the study of beta-cell transdifferentiation. [Diabetologia (2000) Corresponding author: L. Bouwens, VUB-Department of Experimental Pathology, Laarbeeklaan 103, B-1090 Brussels, Belgium Abbreviations: BrdU, Bromodeoxyuridine; CK7, cytokeratin 7; CK20, cytokeratin 20; Flk-1, fetal liver kinase-1; PDX-1, pancreatic duodenal homeodomain containing transcription factor; PGP9.5, ...