Contributions of experimental asbestosis in sheep to the understanding of asbestosis

Our plain-English summary of Contributions of experimental asbestosis in sheep to the understanding of asbestosis, by R. Bégin, A. Cantin, S. Massé, et al (Annals of the New York Academy of Sciences, 1991).

The study

• Authors: R. Bégin, A. Cantin, S. Massé, P. Sébastien
• Journal: Annals of the New York Academy of Sciences
• Published: 1991;643:228-38
• Type of article: Review
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Summary of the article

This review summarized about 15 years of research by the authors' group in Sherbrooke, Québec, using a sheep model of asbestosis developed in the late 1970s, alongside observations in Québec asbestos miners and millers. Sheep were used because their size and docile nature allow repeated lung function tests, chest radiography, gallium-67 lung scans and bronchoalveolar lavage (BAL). The authors reported that disease in sheep closely resembled human asbestosis, both pathologically and functionally. After high or repeated exposures, an early macrophage-dominated alveolitis preceded radiographic and functional changes. This alveolitis could be detected by gallium-67 scanning and by BAL. In workers without radiographic asbestosis, 50 percent had enhanced gallium uptake. Among long-term workers with an abnormal scan, asbestosis appeared to develop in 75% within 3 to 5 years. The authors described four tissue reactions to asbestos: no-retention, low-retention, high-retention and intermediate. They suggested that the intermediate reaction might explain non-progressive cases of minimal asbestosis. Exposure dose and frequency influenced the intensity and speed of disease. In asbestotic sheep given cyclophosphamide, 80 percent died within a year, with more intense fibrosis. Sheep that developed asbestosis had retained more fibers, particularly fibers longer than 5 µm, and this excess accumulation preceded the alveolitis. The authors concluded that alveolar fiber retention is a major determinant of individual susceptibility and that animal models have significantly improved understanding of the human disease.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.

In plain English

This article reviewed about 15 years of the authors' research using asbestos-exposed sheep to model human asbestosis, alongside their studies of long-term Quebec asbestos miners and millers. Low doses caused some cell build-up in the sheep but, by and large, no organized and consistent disease process. High or repeated doses caused lung inflammation (alveolitis) that could progress to fibrosis, even after exposure stopped. Gallium-67 lung scans showed increased uptake before X-ray changes in sheep, and in 50 percent of workers without X-ray signs of asbestosis. About 75% of the Quebec workers with an abnormal scan appeared to develop asbestosis within 3 to 5 years. In one experiment, 80 percent of sheep with asbestosis given the drug cyclophosphamide died within a year, while those not given it survived comparably to controls. Sheep that developed asbestosis had retained more fibers than sheep given the same dose. The authors concluded the sheep disease closely resembled the human disease and that immunosuppressor trials in asbestosis patients should be viewed very cautiously. They noted that the 75% figure may not hold in other occupations.

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: Review of the authors' own earlier experimental studies in a sheep model of asbestosis, together with their related clinical studies in asbestos workers; no new study is reported
• Who was studied: Sheep in an experimental asbestosis model developed by the authors' laboratory (Sherbrooke, Quebec) in the late 1970s, plus long-term asbestos miners and millers of Quebec's Eastern Townships. The article does not give numbers of animals or workers.
• Exposure: Asbestos dust delivered to the sheep lung at low doses, a high initial dose, or multiple doses; chrysotile is named for low-exposure experimental conditions. In humans, long-term work in Quebec asbestos mines and mills.
• Main results:
  • In sheep, low asbestos doses produced some cell accumulation but, by and large, no organized and consistent disease process
  • In sheep, high or multiple doses produced disease whose lung function changes progressed even after exposure stopped
  • Among Quebec asbestos workers without asbestosis visible on X-ray, 50 percent had increased gallium-67 uptake in the lung
  • In sheep, increased gallium-67 lung uptake came before X-ray changes
  • Among long-term Quebec mine and mill workers with an abnormal gallium-67 scan, asbestosis appeared to develop in 75% within 3 to 5 years (no denominator given)
  • In a cyclophosphamide trial in early experimental asbestosis, survival at one year was comparable to controls for normal sheep given the drug and for asbestotic sheep not given it. By contrast, 80 percent of asbestotic sheep given the drug died within the year, with more intense fibrosis and frequent bacterial pneumonia.
  • Sheep that developed asbestosis had retained significantly more fibers in the alveolar space at the time of initial alveolitis than sheep given the same dose that did not develop the disease. The effect was closely associated with retention of fibers longer than 5 (unit garbled in the scan).
  • In sheep, excess fiber accumulation came before the initial alveolitis, which the authors described as a major determinant of individual susceptibility
• The authors' conclusion: The authors concluded that asbestosis in sheep closely resembles human asbestosis on pathological and functional grounds, and that clinical trials of immunosuppressors in patients with asbestosis should be viewed very cautiously
• Limitations the authors state:
  • Whether the 75% progression rate seen in Quebec mine and mill workers applies in other occupational settings had not been documented
  • Alveolar dust clearance could not yet be studied directly in exposed workers and related to asbestosis

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis.

Medical terms in this study, explained in our Lexicon: Bronchoalveolar Lavage (BAL), Macrophage, Fibrosis.

Related studies

• Pulmonary uptake of gallium-67 in asbestos-exposed humans and sheep — R. Bégin, A. Cantin, et al. (1983)
• Biochemical components of bronchoalveolar lavage in early experimental asbestosis of the sheep: phospholipase A2 activity, prostaglandin E2 and proteins — P. Sirois, G. Drapeau, et al. (1983)
• Mass, number and size of lung fibres in the pathogenesis of asbestosis in sheep — P. Sébastien, R. Bégin, et al. (1990)
• Excessive accumulation of asbestos fibre in the bronchoalveolar space may be a marker of individual susceptibility to developing asbestosis: experimental evidence — R. Bégin, P. Sébastien (1989)
• Morphologic features and function of the airways in early asbestosis in the sheep model — R. Bégin, S. Massé, et al. (1982)
• Assessment of progression of asbestosis in the sheep model by bronchoalveolar lavage and pulmonary function tests — R. Bégin, M. Rola-Pleszczynski, et al. (1983)

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