In vitro validation of duct differentiation in developing embryonic mouse pancreas

Background. Early embryonic pancreatic epithelia have the capacity for eith er endocrine or exocrine lineage commitment, Recent studies demonstrated th e pluripotential nature of these undifferentiated cells. Isolated pancreati c epithelia grown under the renal capsule formed primarily islets, However, when these same epithelia were grown in a basement-membrane-rich gel (Matr igel) they formed mostly ducts. Currently, there is no model for in vitro p ancreatic duct formation and therefore, the mechanism of duct morphogenesis has never been described. The purpose of this study was to provide such a model by characterizing the expression of two duct markers, carbonic anhydr ase II (CAII) and the cystic fibrosis transmembrane conductance regulator ( CFTR), in isolated undifferentiated pancreatic epithelia grown in vitro. Materials and methods. We microdissected embryonic pancreases at Embryonic Days (E)9.5-11.5 and performed RT-PCR for CAII and CFTR on E9.5 whole pancr eases, E10.5 and E11.5 epithelia, as well as E11.5 epithelia grown for 7 da ys in Matrigel, Next we performed in situ hybridization for CAII and CFTR a nd immunohistochemistry for CAII on E11.5 epithelia grown for 7 days in Mat rigel. Results. Early, undifferentiated embryonic pancreatic epithelium does not e xpress CAII and CFTR by RT-PCR, When E11.5 epithelia were grown for 7 days in Matrigel, however, gene expression for both markers is upregulated as du cts form. Furthermore, CAII was seen by IHC and both CAII and CFTR were see n by in situ hybridization in the ducts after 7 days in Matrigel, Conclusions. These data validate our in vitro system as a model for studyin g the mechanism of normal pancreatic duct differentiation and may potential ly help us to understand the faulty mechanism involved in pancreatic ductal carcinogenesis. (C) 2000 Academic Press.