Transfection of Human Mesothelial Cells Mediated by Different Asbestos Fiber Types

Abstract

Several different asbestos fiber types mediate transfection of human mesothelial cells by exogenous DNA. We have employed the human MeT-5A mesothelial cell line, which allows the use of DNA replication as an assay for entry of DNA when plasmids bearing the SV4O origin of replication are used for transfection. We find that Canadian chrysotile, Calidria chrysotile, amosite, and crocidolite are each capable of introducing plasmid pSVod DNA into MeT-5A cells followed by subsequent replication of a fraction of the plasmid DNA. A significant fraction of the input plasmid DNA associated with the cells in the presence of asbestos is fragmented, and this fragmentation is particularly evident with crocidolite. Each of the fiber types is highly cytotoxic for the MeT-5A cells, and these cells actively accumulate the added fibers from the surrounding environment as visualized by phase-contrast microscopy. MeT-5A cells were transfected at higher efficiency with calcium phosphate than were several other primate cell lines. Calcium phosphate, however, did not induce fragmentation of the input plasmid DNA. Compared with several different mineral agents, including glass fibers, kaolin, and talc, Calidria chrysotile fibers were most effective at mediating transfection of the MeT-5A cells. Results provide a mechanism by which transfection can contribute to mutagenicity of asbestos fibers and indicate that this mechanism can operate in human mesothelial cells.