Assessment of in vitro differentiation of bovine pancreatic tissue in insulin-expressing cells

Context: Expansion and culture of beta cell progenitors in vitro may represent an alternative to the use of differentiated beta cells from donor pancreata. Objective: The aim of our study was to investigate to what extent exocrine or endocrine pancreatic cells can be differentiated in insulin-producing cells in vitro. Setting: Bovine exocrine tissue (n=4) and islets (n=4) were cultured in DMEM with serum. Interventions: After 7 days, the cells were trypsinized and cultured in the same medium for cell proliferation, or in DMEM/F-12 containing growth factors to induce cell differentiation. Main outcome measure: Proliferating capacity after 4 weeks in culture. In addition, insulin expression was evaluated by RT-PCR and by immunohistochemical staining. Results: After 4 weeks of culture, cells from exocrine tissue showed a 69.5±10.0 fold increase, while cells from islets showed a 31.2±11.4 fold increase (P=0.059). In differentiating medium, monolayers from exocrine and islet tissue were organized into islet-like structures containing cells which stained positively for insulin. Morphometrical analysis and RT-PCR confirmed the presence of insulin in the cells at the protein and the mRNA level. Conclusions: In our experimental conditions, cells from pancreatic tissue proliferated and differentiated in insulin-containing cells. However, the level of insulin as well as mRNA expression is only a small fraction of that shown by fresh islets. Only selective identification of cell precursors may allow efficient generation of insulin-producing cells in vitro.