EFFECTS OF ASBESTOS AND MAN-MADE VITREOUS FIBERS ON CELL-DIVISION IN CULTURED HUMAN MESOTHELIAL CELLS IN COMPARISON TO RODENT CELLS

We report the effects of chrysotile and crocidolite asbestos, and glas s and rock wool fibers (man-made vitreous fibers, MMVF) on the inducti on of binucleate cells in vitro. The response of human mesothelial cel ls (target cells in fiber carcinogenesis) and rodent cells was compare d. Human primary mesothelial cells, MeT-5A cells (an immortalized huma n mesothelial cell line), and rat liver epithelial (RLE) cells were ex posed to asbestos and MMVF samples of similar size range. Milled glass wool, milled rock wool, and titanium dioxide were used as non-fibrous particle controls. All four fiber types caused statistically signific ant increases in the amount of binucleate cells in human primary mesot helial cells and MeT-5A cells (in the dose range 0.5-5.0 mu g/cm(2)). Chrysotile and crocidolite asbestos were more effective (1.3-3.0-fold increases) than thin glass wool and thin rock wool fibers (1.3-2.2-fol d increases). However, when the fiber doses were expressed as the numb er of fibers per culture area, the asbestos and MMVF appeared equally effective in human mesothelial cells. In RLE cells, chrysotile was the most potent inducer of binucleation (2.9-5.0-fold increases), but the response of the RLE cells to crocidolite, thin glass wool, and thin r ock wool fibers was similar to the response of the human mesothelial c ells. No statistically significant increases in the number of bi- or m ultinucleate cells were observed in human primary mesothelial cells or RLE cells exposed to the non-fibrous dusts. In MeT-5A cells exposed t o 5 mu g/cm(2) of milled glass wool and milled rock wool, as well as i n cultures exposed to 2 and 5 mu g/cm(2) of TiO2, significant increase s were, however, observed. Our results show that rodent cells respond differently to mineral fibers than human cells. The results also add e vidence to the suggested importance of disturbed cell division in fibe r carcinogenesis. (C) 1995 Wiley-Liss, Inc.