Pancreatic thread protein is mitogenic to pancreatic-derived cells in culture.

Abstract

Pancreatic thread proteins (PTPs) are acinar cell products and members of the regenerating gene (reg) family. reg expression increases during islet regeneration, is depressed during aging-related islet dysfunction, and may be important in beta-cell growth and maintenance. The aim of this study was to examine the genetic expression of reg in pancreatic-derived cells in vitro and the mitogenic effect of PTP/reg protein on these cells. reg gene expression was measured by Northern analysis in three rat pancreatic cell lines: ARIP (ductal), AR42J (acinar), and RIN (beta-cell). PTP/reg protein was isolated from bovine and human pancreas. Cells were cultured with PTP/reg for 72 hours, and thymidine incorporation was measured. reg messenger RNA was detected in AR42J but not in ARIP or RIN. PTP/reg protein was mitogenic to RIN and ARIP in a dose-related fashion but not to AR42J. It was not mitogenic to cultured mature rat islets. reg messenger RNA is expressed in acinar but not in beta-cell or ductal pancreatic cell lines. PTP/reg protein was mitogenic to both beta-cell and ductal cell lines but not to mature, nondividing islets. This supports the hypothesis that PTP/reg protein is an acinar cell-derived mediator of beta-cell growth and may be involved in modulating the duct-to-islet axis.