Expression of mRNA for growth factors and extracellular matrix proteins after injury to cultured peritoneal cells: does the healing process contribute to peritoneal ultrastructural alteration?

Abstract

The purpose of this study was to investigate the possibility that healing processes following repeated injury by nonphysiological dialysate play a significant role in the pathogenesis of peritoneal ultrastructural alteration, mediated by the production of growth factors and extracellular matrix proteins (ECM). To test a possible mechanism for peritoneal membrane alteration, we investigated whether chemically injured peritoneal mesothelial cells and fibroblasts upregulate their production of growth factors and ECM as a consequence of the healing process. Using 1 N NaOH, circular wounds of uniform surface area were made in monolayers of subconfluent rat peritoneal mesothelial cells (RPMC) and peritoneal fibroblasts (RPFB). At 0, 24, and 72 h after wounding, changes in mRNA expression of transforming growth factor-beta 1 (TGF-Β1), b-FGF, HGF, VEGF, and FN were semiquantified by reverse transcription-polymerase chain reaction. Nonwounded monolayers of RPMC and RPFB were used as controls with mRNA expression being determined at the same times. For RPMC, TGF-Β1, HGF, b-FGF, and FN mRNA gradually increased up to 72 h postwounding to 1.5-fold, 1.6-fold, 1.3-fold, and 2.1-fold of the control levels, respectively. A significant increase was only observed for TGF-Β1, while VEGF showed the least change with time. For RPFB, HGF, b-FGF, VEGF, and FN mRNA expression were slightly suppressed compared to control levels up to 72 h postwounding. TGF-Β1, however, increased markedly above control expression levels by the end of the wound healing process. The production of profibrotic growth factors by mesothelial cells in response to injury may represent a mechanism whereby fibroblast activation, resulting in fibroblast hyperplasia and excessive extracellular matrix accumulation, culminates in alteration of the peritoneal membrane ultrastructure.