An Acidic pH and Activation of Phosphoinositide 3-Kinase Stimulate Differentiation of Pancreatic Progenitors Into Insulin-Producing Cells

Adult pancreatic nonendocrine cells represent a potential alternative source of insulin-producing tissue for the treatment of diabetes. Differentiation of these cells is regulated by various signaling pathways including the phosphoinositide 3-kinase (PI3K) pathway. Therefore, we evaluated the effect of PI3K on this process. Compared with untreated cells the differentiation of human nonendocrine pancreatic cells into insulin-producing elements was increased after treatment with IGF-1, EGF, and Exendin-4, growth factors known to be activators of the PI3K pathway (12.2 ± 3.2% vs 9.1 ± 3.2%). Treatment with PI3K pathway inhibitor wortmannin reduced the number of differentiated beta cells from 9.1 ± 3.2 to 0.7 ± 0.4%. Reverse transcriptase polymerase chain reaction (RT-PCR) analysis revealed that insulin-like growth factor-1 (IGF-1), epidermal growth factor (EGF), and Exendin-4 significantly increased the expression of the transcription factor neurogenin-3, whereas the expressions of pancreatic and duodenal homeobox 1 (PDX-1), neurogenic differentiation 1 (NeuroD) were increased only among samples treated with ZnCl2 and not significantly affected by treatment with the tested growth factors. Successful differentiation of IGF-1, EGF-, and Exendin-4-treated cells into functional beta cells was confirmed by C-peptide secretion in response to 5 versus 20 mmol glucose stimulation (0.24 vs 0.91 pmol C-peptide/μg DNA). These results showed that activation of the PI3K signaling pathway might be used to stimulate the differentiation of nonendocrine pancreatic cells into insulin-producing elements.