DIFFERENTIATION OF PANCREATIC ACINAR-CELLS INTO DUCT-LIKE CELL IN-VITRO

BACKGROUND: Previous studies have shown that a combination of both the extracellular matrix and secretagogues plays critical roles in the ma intenance of well-differentiated pancreatic acinar cells in culture. I n the present study, we have shown that, upon proper stimulation, acin ar cells change their growth pattern and morphologic appearance to a d uct like phenotype. EXPERIMENTAL DESIGN: Both rat and guinea pig acina r cells were cultured on or embedded into the Matrigel basement membra ne, in the presence of differentiating agents such as dimethylsulfoxid e (DMSO), hexamethyl-bis-acetamide, dimethylformamide, triiodothyronin e, and butyric acid. The growth patterns, cell proliferation, ultrastr uctural appearance, intracellular contents, secretion and immunolocali zation of amylase, as well as the expression of the ductal marker carb onic anhydrase II and lectin-binding specific sites were analyzed. Mor eover, the effects of metabolic inhibitors such as cycloheximide and a ctinomycin D on the DMSO induced action were also examined. RESULTS: I solated acinar cells from both rat and guinea pig pancreas showed an i mportant modification of their growth pattern and morphologic appearan ce when culture embedded into Matrigel in the presence of 2% DMSO. The y reaggregate and form isolated and branched tubular structures lined by a single cell layer. These tubules can be maintained in culture for over a period of 21 days. The cells lining the tubules were originall y acinar cells that became elongated and progressively lost their secr etory granules. They displayed a lower number of apical microvilli and established long junctional complexes with elaborated interdigitation s. The immunocytochemical localization and biochemical determination o f intracellular and secreted amylase revealed a progressive decrease r eaching minimal values by the 12th day of culture. The cells further e xpressed the duct cell marker carbonic anhydrase II and lost the Helix pomatia lectin-binding affinity characteristic of acinar cells. Cell proliferation by modified cells as measured by thymidine incorporation and the autoradiographic labeling index, was significantly lower than in control cultured acinar cells. The DMSO differentiating action was mimicked, but to a lesser extent, by the other agents except butyric acid. Since cycloheximide and actinomycin D inhibited the DMSO-induced changes, protein synthesis and DNA transcription seem to be required. CONCLUSIONS: Our results demonstrate that normal pancreatic acinar ce lls retain a morphogenetic plasticity and, upon particular stimulation , can change their differentiation commitment pattern toward that of t he duct cell phenotype.