Characterization of beta cells developed in vitro from rat embryonic pancreatic epithelium

The present study evaluates the development and functional properties of be ta cells differentiated in vitro. The authors have previously demonstrated that when E12.5 rat pancreatic rudiments are cultured in vitro in the absen ce of mesenchyme, the majority of the epithelial cells differentiate into e ndocrine beta cells. Thus, depletion of the mesenchyme provokes the expansi on of endocrine tissue at the expense of exocrine tissue, The potential use of this procedure for the production of beta cells led the authors to char acterize the beta cells differentiated in this model and to compare their p roperties with those of the endocrine cells of the embryonic and adult panc reas. This study shows that the beta cells that differentiate in vitro in t he absence of mesenchyme express the homeodomain protein Nkx6.1, a transcri ption factor that is characteristic of adult mature beta cells. Further, el ectron microscopy analysis shows that these beta cells are highly granulate d, and the ultrastructural analysis of the granules shows that they are cha racteristic of mature beta cells, The maturity of these granules was confir med by a double-immunofluorescence study that demonstrated that Rab3A and S NAP-25, two proteins associated with the secretory pathway of insulin, are strongly expressed, Finally, the maturity of the differentiated beta cells in this model was confirmed when the cells responded to stimulation with 16 mM glucose by a 5-fold increase in insulin release. The authors conclude t hat the beta cells differentiated in vitro from rat embryonic pancreatic ru diments devoid of mesenchyme are mature beta cells. Dev Dyn 1999;214:116-12 6. (C) 1999 Wiley-Liss, Inc.