Ultrastructural changes in lung fibroblast cultures exposed to chrysotile asbestos

Our plain-English summary of Ultrastructural changes in lung fibroblast cultures exposed to chrysotile asbestos, by R.J. Richards, P.M. Hext, G. Blundell, et al (British Journal of Experimental Pathology, 1974).

The study

• Authors: R.J. Richards, P.M. Hext, G. Blundell, W.J. Henderson, B.E. Volcani
• Journal: British Journal of Experimental Pathology
• Published: 1974;55(3):275-81
• Cited by: 22 articles, as counted by NIH iCite
• Read it: PubMed · Free full text

Abstract

Early changes in the ultrastructure of lung fibroblasts exposed to chrysotile asbestos in vitro are described. The dust exposed cells rapidly undergo a “maturation process” reflected by highly dilated endoplasmic cisternae, irregularity in nuclear outline and composition and the appearance of membrane microvilli which are all characteristics of normal cells in the stationary phase. It is suggested the surviving cells undergoing this “maturation process” may account in part for the higher synthetic activity, leading to increased collagen levels, in chrysotile exposed cultures.

In plain English

This was a laboratory experiment on cells, not a study of people. The authors grew rabbit lung fibroblasts, cells that make collagen. They added a single 50-microgram dose of chrysotile A asbestos (a UICC sample) to some cultures and compared them with untreated cultures under the electron microscope. Findings were described rather than counted. Within hours of exposure (apparently 4½ hours; the scan garbles this number), many fibres were inside the cells. They were often wrapped in membrane but never in the nucleus. By 24 hours, nuclei were often grossly distorted, and cell surfaces carried many microvilli, which were rarely seen in untreated cells at that time. After 8 days, most exposed cells held little dust and looked normal, though many still contained large amounts. Collagen fibres were rarely seen in exposed cultures up to day 9, unlike untreated ones, but appeared after 13 days of exposure. The authors concluded that the cells underwent a rapid "maturation process." They speculated that surviving cells might partly explain higher collagen levels found in their earlier biochemical work. They noted that cells take up particles more readily in laboratory culture than in the body.

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 examined by electron microscopy, comparing asbestos-exposed and unexposed cultures; findings are descriptive, not counted
• Who was studied: Cultured rabbit lung fibroblasts (connective-tissue cells), grown on glass coverslips in a laboratory in Cardiff, Wales
• Exposure: A single dose of 50 micrograms of chrysotile A (UICC sample), added to test cultures 24 hours after subculturing; control cultures received medium only
• Main results:
  • Within the first hours of exposure (printed as '41 hours', apparently 4½ hours), exposed fibroblasts had taken up many fibres, and serial sectioning showed many fibres were inside the cells
  • Chrysotile fibres of a wide size range, up to 15 micrometres, entered the exposed cells and were found throughout the cytoplasm, often in vacuoles, but never in the nucleus
  • Fibres inside exposed cells were often enclosed by a membrane rather than in direct contact with the cytoplasm
  • After 24 hours of exposure, nuclei of exposed cells were often grossly distorted, with large abnormal nucleoli
  • At the earliest time point, exposed cells showed highly dilated endoplasmic cisternae, like normal cells in the stationary phase; this was not apparent after 24 hours
  • After 24 hours, exposed cells had many surface microvilli, which were rarely seen in unexposed cells over the same period
  • After 8 days of exposure, a high proportion of exposed cells contained little dust and looked normal, but many still contained large amounts of fibres
  • Cells heavily loaded with dust had highly irregular nuclei, and some were binucleate (had two nuclei)
  • Up to day 9 in culture, collagen fibres were rarely seen in exposed cultures, in contrast to unexposed cultures
  • After 13 days of exposure, the exposed cells had begun to produce collagen
  • Microanalysis (EMMA) showed that the particles inside the cells had the magnesium-to-silicon ratio expected of chrysotile
• The authors' conclusion: The authors concluded that after exposure to chrysotile the fibroblasts rapidly undergo a 'maturation process', taking on the structure of stationary-phase cells. They speculated that surviving cells may be synthetically active and may account in part for the increased collagen levels reported in their earlier biochemical study (Richards and Morris, 1973), not measured here
• Limitations the authors state:
  • Cells show greater phagocytic (particle-engulfing) potential in laboratory culture than in the living body
  • No comparison was made with alveolar macrophages
  • The disappearance of dilated cisternae by 24 hours could reflect either a return to normal or the death of the affected cells
  • It is unknown whether the later collagen increase comes from surviving dust-laden cells or from a relatively dust-free replacement population

Topics

Medical terms in this study, explained in our Lexicon: Fibroblast, Chrysotile, Collagen.

Related studies

• Biochemical effects of asbestiform minerals on lung fibroblast cultures — P.M. Hext, R.J. Richards (1976)
• The effects of long-term exposure of lung fibroblast strains to chrysotile asbestos — P.M. Hext, J. Hunt, et al. (1977)
• Reaction of mineral dusts with primary lung fibroblast cultures — R.J. Richards, J. Hunt (1983)
• Cytokine regulation of lung fibroblast proliferation. Pulmonary and systemic changes in asbestos-induced pulmonary fibrosis — I. Lemaire, H. Beaudoin, et al. (1986)
• Chrysotile asbestos upregulates gene expression and production of alpha-receptors for platelet-derived growth factor (PDGF-AA) on rat lung fibroblasts — J.C. Bonner, A.L. Goodell, et al. (1993)
• Chrysotile asbestos induces PDGF-A chain-dependent proliferation in human and rat lung fibroblasts in vitro — J.A. Lasky, J.C. Bonner, et al. (1996)

Browse more research in British Journal of Experimental Pathology, or return to medical research.