Transplacental transfer of asbestos in pregnant mice

Our plain-English summary of Transplacental transfer of asbestos in pregnant mice, by A.K. Haque, D.M. Vrazel (Bulletin of Environmental Contamination and Toxicology, 1998).

The study

• Authors: A.K. Haque, D.M. Vrazel
• Journal: Bulletin of Environmental Contamination and Toxicology
• Published: 1998;60(4):620-5
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Summary of the article

Earlier human studies had found asbestos fibers in the tissues and placentas of stillborn infants. The authors therefore investigated whether asbestos fibers cross the placenta in pregnant mice. The work was done at the University of Texas Medical Branch, Galveston. Pregnant ICR mice received crocidolite asbestos suspension (approximately 345,000 fibers/ml) by tail vein injection. On gestational day 12, two mice received 0.2 ml and one received 0.45 ml. On gestational day 16, one more mouse received 0.2 ml. One control mouse received 0.2 ml of normal saline on gestational day 15. Mice were sacrificed 1, 48 or 72 hours after treatment, and fetuses and placentas were removed by Caesarean section. In total, 36 fetuses and their placentas from 5 mice were examined. Fibers were counted by light microscopy after tissue digestion. Tissues were also examined by light microscopy for pathologic changes, and by electron microscopy with energy dispersive x-ray analysis. Average fetal counts ranged from 254 fibers/g (48 hours) to 4,288 fibers/g (1 hour). Average placental counts ranged from 5,222 to 23,529 fibers/g. Control tissues contained 0 fibers/g. Focal coagulative necrosis with mild neutrophil infiltration was seen in 29% of placentas from treated mice. Electron microscopy of necrotic placental areas showed very small (100-700 nm) fibers in the cytoplasm of placental sinusoidal cells, and a few within cell nuclei. The authors concluded that asbestos fibers transferred to the fetus and placenta within an hour of intravenous injection and remained present for up to 72 hours. They noted that the observations were based on a small number of animals.

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In plain English

This was an animal experiment testing whether asbestos fibers injected into pregnant mice reach their fetuses and placentas. Four pregnant ICR mice each received one tail-vein injection of crocidolite asbestos suspension (about 345,000 fibers per ml, given as 0.2 ml or 0.45 ml) on gestational day 12 or 16. One control mouse received saline. The mice were killed 1, 48 or 72 hours after injection, and 36 fetuses and their placentas from the 5 mice were examined. Average fetal counts in the treated mice ranged from 254 fibers/g (48-hour mouse) to 4,288 fibers/g (1-hour mouse). Average placental counts ranged from 5,222 fibers/g (72-hour mouse, 0.2 ml dose) to a figure printed as '23, 529' fibers/g (48-hour mouse). Fetal and placental tissue from the control mouse had 0 fibers/g. In 29% of placentas from treated mice there were small areas of coagulative necrosis (tissue death) with mild inflammation. Electron microscopy found very small fibers in those areas, a few inside cell nuclei. The authors concluded that transfer across the placenta occurred and that fibers remained for up to 72 hours. They noted the observations rest on a small number of animals.

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: Animal experiment: single intravenous injection of asbestos into pregnant mice, followed by light and electron microscopic examination of fetal and placental tissues
• Who was studied: 5 pregnant ICR mice from Harlan Laboratories (4 injected with asbestos, 1 saline control), received on the tenth day of pregnancy; 36 fetuses and their placentas were examined
• Exposure: Crocidolite asbestos suspension of approximately 345,000 fibers/ml, injected into the tail vein. Two mice received 0.2 ml and one received 0.45 ml on gestational day 12. One mouse received 0.2 ml on gestational day 16. The control mouse received 0.2 ml saline on gestational day 15. Mice were sacrificed 1, 48 or 72 hours after treatment.
• Main results:
  • Mouse sacrificed 1 hour after injection: average fetal digest count 4,288 fibers/g (range 116 to 30,342 fibers/g); average placental count 10,857 fibers/g (range 1,335 to 48,337 fibers/g)
  • Mouse sacrificed at 48 hours: average fetal count 254 fibers/g (range 0 to 706 fibers/g); average placental count printed as '23, 529' fibers/g (range 6,026 to 104,481 fibers/g)
  • Mouse sacrificed at 72 hours after a 0.2 ml dose: average fetal count 1,010 fibers/g (range 378 to 2,225 fibers/g); average placental count 5,222 fibers/g (range 1,171 to 11,800 fibers/g)
  • Mouse sacrificed at 72 hours after a 0.45 ml dose: average fetal count 855 fibers/g (range 139 to 1,440 fibers/g); average placental count 11,683 fibers/g (range 2,781 to 17,483 fibers/g)
  • Fetal and placental digests from the saline control mouse had 0 fibers/g
  • Focal areas of coagulative necrosis with mild neutrophil infiltration were seen in 29% of placentas from treated mice. No other pathologic changes were seen in fetuses or placentas.
  • No fibers were visible by light microscopy in the necrotic placental areas. Electron microscopy of those areas showed very small (100 nm to 700 nm) asbestos fibers, some in the cytoplasm of placental sinusoidal cells and a few within the cell nucleus.
• The authors' conclusion: The authors concluded that the study confirms transplacental transfer of asbestos in mice after a single intravenous injection, and that the fibers remain in both fetus and placenta for up to 72 hours after injection
• Limitations the authors state:
  • The observations are based on a small number of animals and need further exploration
  • There was no previous data on the dose or the best treatment days in pregnant mice, so the injection days were chosen by the authors

Topics

Medical terms in this study, explained in our Lexicon: Crocidolite, Tissue Digestion, Necrosis.

Related studies

• Chrysotile asbestos fibers detected in the newborn pups following gavage feeding of pregnant mice — A.K. Haque, I. Ali, et al. (2001)
• Asbestos in organs and placenta of five stillborn infants suggests transplacental transfer — A.K. Haque, M.G. Mancuso, et al. (1992)
• Placental transfer of asbestos — H.M. Cunningham, R.D. Pontefract (1974)
• Teratogenicity of asbestos in mice — T. Fujitani, M. Hojo, et al. (2014)
• Regression of AK7 malignant mesothelioma established in immunocompetent mice following intratumoral gene transfer of interferon gamma — L. Cordier Kellerman, L. Valeyrie, et al. (2003)
• Giant benign fibrous tumor of the pleura in a pregnant woman: report of a case — A. Cakan, U. Cagirici, et al. (2003)

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