Transdifferentiation molecular pathways of neonatal pig pancreatic duct cells into endocrine cell phenotypes.

Restrictions in availability of cadaveric human donor pancreata have intensified the search for alternate sources of pancreatic endocrine tissue. We have undertaken to assess whether nonendocrine pancreatic tissue, with special regard to ducts, including epithelial cells, and retrieved from neonatal pig pancreata that are used for islet isolation, may under special in vitro culture conditions generate endocrine cell phenotypes. Special care was taken to identify the time-related appearance of molecular and biochemical markers associated with beta-cell specificity, in terms of glucose-sensing apparatus and insulin secretion. For this purpose, established ductal origin monolayer cell cultures were incubated with a battery of mono- or polyvalent growth factors. Morphological, immunocytochemical, molecular, and functional assays indicated that under special culture conditions ductal origin cells acquired an endocrine identity, based upon expression of key gene transcripts that govern the stimulus-coupled insulin secretory activity. Among factors eliciting transdifferentiation of ductal epithelial into endocrine cells, Sertoli cell (SC)-conditioned medium seemed to be the most powerful inducer of this process. In fact, the resulting cultures not only expressed beta-cell-oriented metabolic markers but also were associated with insulin and C-peptide output at equimolar ratios. This finding indicates that SC coincubation, more than other conditions, caused originally ductal cell cultures to gradually differentiate and mature into beta-cell-like elements. In vivo studies with this early cell differentiation product will test whether our approach may be suitable for correction of hyperglycemia in diabetic animal models.