Cytotoxicity of refractory ceramic fibres to Chinese hamster ovary cells in culture

Our plain-English summary of Cytotoxicity of refractory ceramic fibres to Chinese hamster ovary cells in culture, by G.A. Hart, M.M. Newman, W.B. Bunn, et al (Toxicology in Vitro, 1992).

The study

• Authors: G.A. Hart, M.M. Newman, W.B. Bunn, T.W. Hesterberg
• Journal: Toxicology in Vitro
• Published: 1992;6(4):317-26
• Cited by: 24 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The toxicity/oncogenicity of refractory ceramic fibres have been tested in chronic inhalation studies in rodents. Because these studies are time consuming and expensive, there is a need to develop and validate short-term models to screen fibres for their toxicological potential. In the present study, the toxic effects of four different compositions of refractory ceramic fibres were determined using Chinese hamster ovary cells grown in culture. These refractory ceramic fibres were the same size-selected fibres that had been used in animal inhalation studies, thus facilitating a direct comparison of findings in the two systems. Chinese hamster ovary cells were treated with refractory ceramic fibres 24 hr after seeding into 60-mm culture dishes in Ham's F12 medium with 10% serum. Inhibition of cell proliferation and colony formation were determined after 3-5 days of fibre exposure. Crocidolite and chrysotile asbestos were used as positive controls. Concentration-dependent inhibition of both cell proliferation and colony formation was observed after treatment with refractory ceramic fibres. The LC(50) for the different refractory ceramic fibres ranged from 10 to 30 mug/cm(2). The LC(50)s for crocidolite and chrysotile were 5 mug/cm(2) and 1 mug/cm(2), respectively. To assess the genotoxic potential of these fibres, fibre-exposed Chinese hamster ovary cell cultures were stained with acridine orange and scored for the incidence of micronuclei and other nuclear abnormalities. The incidence of nuclear abnormalities for refractory ceramic fibres at 20 mug/cm(2) ranged from 20 to 40%. Toxic endpoints of the in vitro studies were compared with those of the chronic animal inhalation studies. The latter included induction of lung fibrosis and pleural and airway tumours. A correlation was observed between the in vitro and in vivo toxicological potencies of the respective four refractory ceramic fibres: the fibres that were most toxic in vitro were also the most toxic in the chronic animal inhalation studies. A direct relationship was also observed, both in vitro and in vivo, between average fibre length and the severity of the toxic effect.

In plain English

This laboratory study tested whether a short-term cell-culture test would rank refractory ceramic fibres (RCFs) the same way as earlier long-term rodent inhalation studies of the same fibres. The authors exposed Chinese hamster ovary (CHO) cells to four size-selected RCFs: kaolin, zirconia, high purity, and an "after service" fibre made by heating the kaolin fibre to 1300 degrees C. UICC crocidolite and chrysotile asbestos were the comparison fibres. The authors measured cell growth, colony formation and abnormal cell nuclei. Growth and colony formation fell as fibre concentration rose. The concentration that halved cell or colony numbers ranged from 10 to 30 micrograms per square centimetre for the RCFs. The article's abstract gives 5 for crocidolite and 1 for chrysotile. The shortest fibre, the after-service fibre, was least toxic, and the kaolin and high-purity fibres were most toxic. This ranking generally matched the earlier animal results, except for mesothelioma, where the zirconia fibre ranked highest. The authors called the correlation encouraging but said more research is needed. They noted that only one cell type and three measures were used.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: In vitro (cell culture) experiment comparing four refractory ceramic fibres and two asbestos types, with results compared against previously reported chronic rodent inhalation studies of the same fibres
• Who was studied: Chinese hamster ovary cells (CHO-K1 cell line from the American Type Tissue Collection) grown in 60-mm culture dishes. Each exposure group was set up in triplicate. The cells' tissue of origin is not known to be a target of fibre-induced disease.
• Exposure: Four size-selected refractory ceramic fibres from the TIMA Fibre Repository: RCF1 (kaolin, average length 21.5 µm), RCF2 (zirconia, 16.7 µm), RCF3 (high purity, 24.3 µm) and RCF4 (after service; RCF1 heated to 1300 degrees C, about 27% cristobalite, average length 9.2 µm). UICC crocidolite and UICC chrysotile asbestos were the positive controls, and mitomycin C was the positive control in the nuclear-abnormality test. Concentrations were up to about 40 µg/cm2.
• Main results:
  • Across all three tests, the four RCFs ranked the same way: RCF4 least toxic, RCF2 intermediate, RCF1 and RCF3 most toxic.
  • The LC50 (concentration giving half as many cells or colonies as unexposed controls) for the RCFs ranged from 10 to 30 µg/cm2. Table 4 gives, for growth inhibition and colony formation respectively: RCF1 13 and 10, RCF2 17 and 18, RCF3 13 and 12, RCF4 30 and 22.
  • Per the article's abstract, the LC50s for crocidolite and chrysotile were 5 µg/cm2 and 1 µg/cm2 respectively. Crocidolite was more toxic than the RCFs in all three tests. Chrysotile was more toxic than crocidolite in the two tests in which it was included.
  • Nuclear abnormalities (micronuclei and/or polynuclei): chrysotile at 5 µg/cm2 produced them in 49% of cells, crocidolite at 5 µg/cm2 in 28%, and the RCFs at 20 µg/cm2 in 22 to 33% (results section).
  • Mitomycin C (2 µM) produced a 29% incidence of micronuclei and a 10% incidence of polynuclei. All fibre types produced roughly half as many micronuclei as polynuclei.
  • The in vitro ranking generally matched the earlier rodent inhalation results for the same RCFs. Percentages of animals with lung tumours were: negative control 1.6, RCF1 13.0, RCF2 6.9, RCF3 14.6, RCF4 3.2. Percentages with mesotheliomas were 0.0, 1.5, 2.3, 1.5 and 0.8 respectively. The exception was mesothelioma, where RCF2 ranked highest.
• The authors' conclusion: The authors concluded that the correlation between the in vitro and in vivo results was encouraging. They said fibre length probably accounts for the differences between the RCFs, and that more research is needed to determine which in vitro tests best correlate with animal inhalation studies and human epidemiology.
• Limitations the authors state:
  • Only three measures of toxic response and only one cell type were used.
  • The CHO cells' tissue of origin is not known to be a target tissue of fibre-induced disease.
  • The idea that disrupted cell division is the main toxic effect would need cell viability testing to confirm.
  • Lung deposition, lung clearance and long-term biopersistence cannot be measured in vitro.

Topics

Medical terms in this study, explained in our Lexicon: Crocidolite, Chrysotile, Micronuclei, Fibrosis.

Related studies

• Effects of asbestos fibers on cell division, cell survival, and formation of thioguanine-resistant mutants in Chinese hamster ovary cells — K. Kenne, S. Ljungquist, et al. (1986)
• Genotoxicity and cytotoxicity of multi-wall carbon nanotubes in cultured Chinese hamster lung cells in comparison with chrysotile A fibers — M. Asakura, T. Sasaki, et al. (2010)
• Cytotoxicity and multinucleate giant cell formation in Chinese hamster lung fibroblast caused by crocidolite and chrysotile — Y.C. Hong, S.S. Choi (1997)
• Effects of fibrous and non-fibrous dusts on Chinese hamster V79 cells: Cytotoxicity or cytostasis? — S.O. Lock, J. Rockley, et al. (1987)
• Mechanisms of cytotoxicity of asbestos fibres in rat tracheal epithelial cells in culture — T.W. Hesterberg, D.G. Ririe, et al. (1987)
• Induction of chromosome changes in Chinese hamster cells by exposure to asbestos fibres — A. Sincock, M. Seabright (1975)

Browse more research in Toxicology in Vitro, or return to medical research.