The effects of long-term exposure of lung fibroblast strains to chrysotile asbestos

Our plain-English summary of The effects of long-term exposure of lung fibroblast strains to chrysotile asbestos, by P.M. Hext, J. Hunt, K.S. Dodgson, et al (British Journal of Experimental Pathology, 1977).

The study

• Authors: P.M. Hext, J. Hunt, K.S. Dodgson, R.J. Richards
• Journal: British Journal of Experimental Pathology
• Published: 1977;58(2):160-7
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Free full text

Abstract

Evidence is presented that persistent long-term exposure of a strain of lung fibroblast-like cells to chrysotile asbestos over 37 passages in vitro leads to enhancement in cell mat collagen deposition and is accompanied by other metabolic alterations in the cultures.

In plain English

This laboratory study used lung fibroblast-like cells grown from rabbit lung. The cells were divided into two strains. One strain was given a small dose of UICC Rhodesian chrysotile asbestos in most of its passages (repeated subcultures). The other was left untreated as a control. The asbestos dose was lowered after Passage 14 to keep toxic effects to a minimum. Across 37 passages, the authors measured fibrous collagen (as hydroxyproline), DNA, RNA and protein in test cultures grown for 24 days without further asbestos. The chrysotile-treated strain had more fibrous collagen per culture than the normal strain at each subculture except Passages 4, 13 and 15. The authors said this difference was not simply explained by more cells. A substrain kept without further asbestos from the 38th to the 45th passage had collagen levels practically identical to the treated strain, but these data were not given. The authors concluded that persistent exposure to small quantities of chrysotile considerably enhanced the cells' capacity to make and/or deposit fibrous collagen. They said its relevance to asbestos-induced fibrosis in living lungs can only be surmised.

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 (in vitro) cell culture experiment comparing an asbestos-treated cell strain with an untreated control strain over many subcultures
• Who was studied: A primary culture of rabbit lung fibroblast-like cells, divided at the first subculture into a chrysotile-treated strain (D70/C) and an untreated normal strain (D70/N); Department of Biochemistry, University College, Cardiff
• Exposure: Small doses of UICC Rhodesian chrysotile asbestos added in the majority of passages. No dust was added at Passages 4, 6, 8, 14, 16, 18 and 20 to 22, and the dose was lowered after Passage 14. Test cultures taken for analysis received no further asbestos during their 24 days of growth.
• Main results:
  • The chrysotile-treated strain had higher levels of fibrous collagen per culture than the normal strain at each subculture except Passages 4, 13 and 15
  • The authors reported that the extra collagen in the asbestos-treated cultures was not simply explained by more cells; DNA levels were often lower in the treated strain than in the normal strain, with notable exceptions at Passages 25 to 27
  • In the normal strain, cell mat hydroxyproline was 6 micrograms per culture at Passage 10 and 80 micrograms at Passage 29, over 13 times lower at Passage 10
  • In the chrysotile-treated strain, hydroxyproline was 8 micrograms per culture at Passage 12 and 148 micrograms per culture at Passage 25, over 18 times lower at Passage 12
  • Protein and RNA levels were considerably higher in the chrysotile-treated strain than in the normal strain between Passages 20 and 27; after Passage 27 they were similar, while collagen stayed high in the treated cultures
  • A substrain derived from the treated strain at the 38th passage and kept to the 45th passage without further asbestos had cell mat hydroxyproline levels practically identical to the treated strain, and considerably higher than equivalent normal cultures after 14 days (data not given)
  • The normal strain could no longer be maintained after the 44th passage. The chrysotile-treated strain showed no deterioration in growth ability or plating efficiency and was abandoned after the 45th passage because no control strains were left for comparison.
  • In the chrysotile-treated strain, binucleate cells were common in early passages, and cells with large nuclei increased between Passage 6 and Passage 25, particularly at Passage 16; in the normal strain such cells were extremely rare early but more common after Passage 27
• The authors' conclusion: The authors concluded that persistent exposure of lung fibroblast-like cells to small quantities of chrysotile asbestos considerably enhanced their capacity to synthesise and/or deposit fibrous collagen. They said this effect may not be reduced for many cell generations after exposure stops.
• Limitations the authors state:
  • The authors stated that the relevance of these laboratory findings to asbestos-induced fibrosis in the living lung can only be surmised
  • The authors stated that how chrysotile produces the effect on collagen is not known
  • The authors noted that collagen levels in normal cells grown under identical conditions varied widely between passages

Topics

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

Related studies

• Biochemical effects of asbestiform minerals on lung fibroblast cultures — P.M. Hext, R.J. Richards (1976)
• Ultrastructural changes in lung fibroblast cultures exposed to chrysotile asbestos — R.J. Richards, P.M. Hext, et al. (1974)
• Reaction of mineral dusts with primary lung fibroblast cultures — R.J. Richards, J. Hunt (1983)
• A preliminary study of biochemical changes in the rat small intestine following long-term ingestion of chrysotile asbestos — R. Jacobs, K.S. Dodgson, et al. (1977)
• The long term fibrogenic effects of chrysotile and crocidolite asbestos dust injected into the pleural cavity of experimental animals — J.M. Davis (1970)
• Primary lung fibroblasts from the 129 mouse strain exhibit reduced growth factor responsiveness in vitro — D.M. Brass, S.Y. Tsai, et al. (2001)

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