Abstracts
1998 Digestive Disease Week

#1017

REGULATION OF PANCREATIC DUCT CELL GROWTH BY TRANSFORMING GROWTH FACTOR BETA (TGF_) IN VITRO. C. Alvarez, B.L. Bass. University of Maryland and Surgical Service, Baltimore VAMC, Baltimore, MD 21201.

Expression of TGF_ is increased in the periductal regions of the pancreas during the course of clinical and experimental acute and chronic pancreatitis. We have previously shown that TGF_ protects the pancreatic duct epithelium (PDE) from damage produced by bile salts in vitro. Here we examined whether TGF_ affects proliferation vs. migration.

METHODS: Segments of the bovine main pancreatic duct were dissected out of freshly obtained pancreata (n=5), placed in culture on collagen rafts and stabilized in defined culture media for 48h at 37°C in 5% CO2. TGF_ was then added (0, 0.01, 0.1 and 1nM) for a second 48h incubation period. The explants were then processed for light microscopy (H&E) and immunohistochemistry using antibody against a marker of proliferation, the nuclear antigen PCNA. The amount of PDE cell extension from the cut edge of the explant and the extent of epithelial damage as a percentage of the total explant length were measured with a micrometer. The epithelial cell density (cells/high power field) was also determined. Statistical comparisons were made using Student's t-test.

RESULTS: TGF_ caused a dose-response increase in epithelial density and extension from the cut edge (p<0.05). PCNA staining was strong and evident throughout the explant epithelium in the absence of TGF_ and at the lowest dose. With higher concentrations, PCNA expression was completely suppressed in the native epithelium but persisted at the explant margins, as duct cells proliferated to cover denuded connective tissue in the cut edge.

CONCLUSIONS: PDE cell density increased in the absence of proliferation, suggesting either artifact or connective tissue influence. Epithelial extension at the explant margin (which is analogous to a denuded epithelial "wound") was stimulated by TGF_ and represents proliferation. The increased TGF_ expression observed in pancreatitis may be intended promote PDE recovery from damage.

Copyright 1996 - 1998, SSAT, Inc. Revised 29 June 1998.