OBJECTIVETo investigate if tumor necrosis factor-alpha (TNF-alpha) could induce phenotypic transformation or the associated cell function changes of human peritoneal mesothelial cells (HPMCs).

METHODSAll tests were performed on the human peritoneal mesothelial cell line (HMrSV5, kindly donated by Prof. Pierre RONCO). Morphological changes of HPMCs were observed by phase contrast microscopy. The expressions of cytokeratin 8, cytokeratin 18 and vimentin were detected by immunocytochemistry. mRNA expressions of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) were detected by semiquantitative reverse transcription polymerase chain reaction (RT-PCR). Production of MMP-9 and type I collagen was measured by enzyme-linked immunosorbent assays.

RESULTSTNF-alpha (1 - 10 ng/ml) induced morphological changes in about 50% - 60% of human peritoneal mesothelial cells (HPMCs). The original polygonal cobblestone monolayer was changed into elongated, spindle-shape characteristic of fibroblasts. The original strong positive expression of cytokeratin 8 and cytokeratin 18 was changed in all morphologically changed HPMCs to negative, but the expression of vimentin maintained positive. By 4-hour treatment with TNF-alpha (1 - 10 ng/ml), mRNA expression of MMP9 was significantly up-regulated, and mRNA expression of TIMP-1 and TIMP-2 were down-regulated. We also observed that the production of MMP-9 and type I collagen increased significantly after 24-hour treatment with TNF-alpha.

CONCLUSION24-hour treatment with TNF-alpha, produced a partial transformation of HPMCs into the fibroblast phenotype. TNF-alpha treatment of HPMCs up-regulated the synthesis of MMP-9 and type I collagen, which may facilitate peritoneal extracellular matrix remodeling and fibrogenesis.