In vitro dedifferentiation of fetal porcine pancreatic tissue prior to transplantation as islet-like cell clusters

The fetal porcine pancreas under experimental conditions can be transplante d in the form of explants or islet-like cell clusters (ICCs) to normalize b lood glucose levels in diabetic recipients. ICCs are released from the coll agenase-digested pancreas and require a 4- to 5-day culture period for thei r complete formation. In order to maximize insulin producing beta cell diff erentiation following transplantation, an understanding of ICC development is essential to utilize this alternative treatment for type 1 diabetes. In this study a role is proposed for exocrine cells in the generation of the m ultipotent pancreatic precursor cells during the culture period. Acinar cel ls undergo dedifferentiation during the initial stages of the culture perio d into multipotent pancreatic precusor cells, previously called protodiffer entiated cells. The progressive loss of exocrine differentiation appears to involve rapid degranulation of zymogen granules by exocytosis and loss of the prominent secretory apparatus. These processes occur in parallel with a significant reduction in the expression of lipase in the period from day 0 to day 5 and simultaneously there is an increase in the epithelioid/ductal cell marker, cytokeratin 20. Using proliferating cell nuclear antigen, cel l proliferation during the culture period does not appear to account for th e increase in epithelioid/ductal cells. Further the rates of apoptosis and necrosis which were identified using the TUNEL technique and propidium iodi de, respectively, do not appear to account for the reduction in exocrine ce ll numbers. Exocrine cell dedifferentiation appears to increase the pool of protodifferentiated cells which have the potential to develop into the ins ulin- producing beta -cell population following transplantation into the di abetic recipient Copyright (C) 2001 S. Karger AG, Basel.