Inhibition of cytokinesis by asbestos and synthetic fibres

Our plain-English summary of Inhibition of cytokinesis by asbestos and synthetic fibres, by C.G. Jensen, M. Watson (Cell Biology International, 1999).

The study

• Authors: C.G. Jensen, M. Watson
• Journal: Cell Biology International
• Published: 1999;23(12):829-40
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Using high-resolution timelapse microscopy, we have followed individual phagocytized fibres through the later stages of division in MeT-5A human mesothelial cells and LLC-MK(2)monkey epithelial cells. The fibres used were crocidolite and chrysotile asbestos, fibrous glass (MMVF), and refractory ceramic fibres (RCF). Long fibres (15-80 microm) trapped within the cleavage furrow can partially or completely block cytokinesis. Cells proceed in one of three ways: (1) eventual completion of cytokinesis; (2) incomplete cytokinesis, resulting in two cells joined by a fibre-containing intercellular channel; or (3) failure of cytokinesis, resulting in a binucleate or trinucleate cell. Two factors associated with fibre-induced bi/trinucleation are: (1) an initial association between the fibre and the forming daughter nuclei, which is sometimes lost over time, and (2) disintegration of the midbody. The studies suggest that delay of cytokinesis by interzonal fibres can result in bi/trinucleation through the loss of midbody/intercellular bridge proteins that are required for completion of cytokinesis.

Copyright 1999 Academic Press.

In plain English

This laboratory study filmed living cells in culture as they divided after taking up fibres. The cells were a human lung mesothelial cell line (MeT-5A) and a monkey kidney cell line (LLC-MK2). The fibres were crocidolite and chrysotile asbestos, fibrous glass (MMVF) and refractory ceramic fibres (RCF). Of 65 dividing cells filmed, 38 contained fibres and 27 were controls. The authors examined in detail 16 cells with a fibre caught where the cell splits in two. In all 16, the final splitting step was delayed compared with controls. Five eventually separated, three stayed joined by a channel holding the fibre, and eight became a single cell with two or three nuclei. These fibres were 15 to 80 micrometres long. In a separate count of MeT-5A cultures exposed for 48 hours, 5.2% of control cells had two or more nuclei, based on 1000 cells. This compared with 8.0% to 13.7% in fibre-exposed cultures. The authors concluded that the ability to produce cells with two nuclei appeared related to fibre length rather than fibre type.

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: laboratory cell culture study: time-lapse video microscopy of living dividing cells, with fluorescence and electron microscopy
• Who was studied: Two cultured cell lines: LLC-MK2 rhesus monkey kidney epithelial cells and MeT-5A transformed human lung mesothelial cells (University of Auckland, New Zealand). The study filmed 65 dividing cells: 38 containing one of the four fibre types and 27 controls. Of these, 16 fibre-containing cells were analysed in detail.
• Exposure: Four fibre types were added at 0.3 to 1.0 mg/ml: International Union Against Cancer crocidolite asbestos, National Institute of Environmental Health Sciences intermediate-length chrysotile asbestos, MMVF 10a fibrous glass, and RCF 1a refractory ceramic fibres. The share of fibres 15 to 80 micrometres long was 13.0% for crocidolite, 2.0% for chrysotile, 53% for MMVF and 64% for RCF.
• Main results:
  • In all 16 cells with fibres in the dividing zone (9 RCF, 4 MMVF, 2 crocidolite, 1 chrysotile), cytokinesis was delayed. Control cells separated within 25 to 30 min (LLC-MK2) or 40 to 45 min (MeT-5A) after anaphase onset.
  • Five of the 16 cells (four with RCF, one with MMVF) eventually separated completely.
  • Three of the 16 cells (two with crocidolite, one with RCF) stayed joined by a persistent channel containing the fibres.
  • Eight of the 16 cells (four with RCF, three MMVF, one chrysotile) became a single cell with two or three nuclei. Three of these eight had three nuclei.
  • The fibres in the dividing zone of the 16 analysed cells were 15 to 80 micrometres long. The authors calculated that a fibre must be at least 15 micrometres long to reach both forming nuclei in these cells.
  • When the midbody (a structure in the bridge between dividing cells) disappeared, the cells did not separate and the nuclei ended up in one cell. When the midbody persisted, the cells stayed joined by the fibre.
  • In a separate count of MeT-5A cultures after 48 hours, 5.2% of control cells had two or more nuclei (based on 1000 cells). In fibre-exposed cultures the share was 12.5% with crocidolite, 10.1% with chrysotile, 13.7% with MMVF and 8.0% with RCF. No statistical tests are reported. The authors stated that LLC-MK2 data were similar.
• The authors' conclusion: The authors concluded that both asbestos and synthetic fibres can block cytokinesis, in some cases producing cells with two nuclei. They also concluded that this ability appears related to fibre length rather than fibre type, and that this should be considered when comparing the toxicity of natural and synthetic fibres.

Topics

Medical terms in this study, explained in our Lexicon: Mesothelial Cells, Crocidolite, Chrysotile.

Related studies

• Long crocidolite asbestos fibers cause polyploidy by sterically blocking cytokinesis — C.G. Jensen, L.C. Jensen, et al. (1996)
• A comparison of the cytogenetic response to asbestos and glass fibre in Chinese hamster and human cell lines. Demonstration of growth inhibition in primary human fibroblasts — A.M. Sincock, J.D. Delhanty, et al. (1982)
• Bromo-deoxyuridine (BRDU) uptake in the lungs of rats inhaling amosite asbestos or vitreous fibres at equal airborne fibre concentrations — K. Donaldson, D.M. Brown, et al. (1995)
• Biological effects of naturally occurring and man-made fibres: in vitro cytotoxicity and mutagenesis in mammalian cells — R. Okayasu, L. Wu, et al. (1999)
• Angiogenic effect induced by mineral fibres — D. Carbonari, A. Campopiano, et al. (2011)
• Differential in vitro cellular response induced by exposure to synthetic vitreous fibers (SVFs) and asbestos crocidolite fibers — G. Cardinali, D. Kovacs, et al. (2006)

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