Induction of angiogenesis by intraperitoneal injection of asbestos fibers

Our plain-English summary of Induction of angiogenesis by intraperitoneal injection of asbestos fibers, by R.M. Branchaud, J.L. MacDonald, A.B. Kane (FASEB Journal, 1989).

The study

• Authors: R.M. Branchaud, J.L. MacDonald, A.B. Kane
• Journal: FASEB Journal
• Published: 1989;3(6):1747-52
• Cited by: 20 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Tumors and activated macrophages release angiogenic factors that stimulate migration and proliferation of capillaries. We studied the development of angiogenesis before the appearance of mesotheliomas in C57B1/6 mice. Weekly i.p. injections of crocidolite asbestos fibers produced mesotheliomas after 30-50 wk. The initial histologic response to asbestos fibers was a nodular lesion on the peritoneal lining composed of clusters of fibers, activated macrophages, and proliferating mesenchymal cells. The earliest visible evidence of angiogenesis was seen surrounding 7% of these lesions 14 days after a single injection of 200 micrograms of crocidolite asbestos fibers. After six weekly injections, 30% of the lesions containing asbestos fibers were surrounded by a capillary network radiating toward the center of the lesion. Other mineral fibers, including chrysotile asbestos and fiberglass, also induced angiogenesis after six weekly injections. In contrast, only 8% of the lesions containing short asbestos fibers (90.6% less than or equal to 2.0 microns) and 9% of the lesions containing silica particles showed evidence of angiogenesis. We conclude that tumorigenic mineral fibers induce angiogenesis in the peritoneal lining, whereas nontumorigenic mineral particles or short asbestos fibers are less effective. Ingrowth of new blood vessels around clusters of asbestos fibers may facilitate the later emergence of mesotheliomas at these sites.

In plain English

This was an animal experiment in C57B1/6 mice. The researchers injected mineral fibers or particles into the abdominal (peritoneal) cavity. They looked for angiogenesis, the growth of new blood vessels, around the clusters of material that formed on the abdominal lining, and they measured whether cells lining those vessels were dividing. After a single injection of 200 micrograms of crocidolite asbestos, new vessels surrounded 0% of 24 lesions on day 1, 7% of 84 lesions on day 14 and 19% of 89 lesions on day 21. Short crocidolite fibers produced less angiogenesis than long ones. After six weekly injections, the share of lesions with angiogenesis was 30% of 152 with native crocidolite, 27% of 201 with chrysotile type B asbestos and 16% of 42 with code 100 fiberglass. It was 8% of 194 with short crocidolite, 9% of 64 with silica and 0% of 91 with titanium dioxide. The authors stated that their injection model produces mesotheliomas after 30-50 weeks. They concluded that angiogenesis is a prominent response to fibers known to induce mesotheliomas, and that new vessels may help tumor cells grow at these sites.

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 (mice given injections into the abdominal cavity, with lesions examined under the microscope and by autoradiography)
• Who was studied: C57B1/6 mice, Brown University, Providence, Rhode Island. The total number of mice is not given in the text. For the six-week comparison, results came from three mice per treatment.
• Exposure: Injections into the abdominal cavity. Some mice received a single injection of 200 micrograms of native crocidolite asbestos. Others received single injections of short or long crocidolite fibers in equal fiber numbers. Others received six weekly injections of 200 micrograms of native crocidolite, chrysotile type B asbestos, code 100 fiberglass, silica or titanium dioxide, or 120 micrograms of short crocidolite fibers. Saline was the control.
• Main results:
  • After a single injection of native crocidolite, the share of lesions with angiogenesis rose over 21 days: 0% of 24 lesions at day 1, 0% of 36 at day 3, 3% of 111 at day 7, 7% of 84 at day 14 and 19% of 89 at day 21.
  • Existing small arteries in the intestinal mesenteries near asbestos fiber clusters showed dividing lining cells early after injection. The authors said this most likely reflected repair of injury from inflammation.
  • Short crocidolite fibers produced less angiogenesis than long crocidolite fibers after a single injection.
  • After six weekly injections of native crocidolite asbestos, 30% of 152 lesions showed angiogenesis. In these mice, 31.9 percent of capillaries (plus or minus 14.8) had labeled, dividing lining cells.
  • After six weekly injections of chrysotile type B asbestos, 27% of 201 lesions showed angiogenesis. In these mice, 20.8 percent of capillaries (plus or minus 1.9) had labeled lining cells.
  • After six weekly injections of code 100 fiberglass, 16% of 42 lesions showed angiogenesis. In these mice, 18.6 percent of capillaries (plus or minus 6.0) had labeled lining cells.
  • After six weekly injections of short crocidolite fibers, 8% of 194 lesions showed angiogenesis. In these mice, 7.6 percent of capillaries (plus or minus 3.4) had labeled lining cells.
  • After six weekly injections of silica particles, 9% of 64 lesions showed angiogenesis. After six weekly injections of titanium dioxide particles, 0% of 91 lesions did.
  • Whether a lesion showed angiogenesis did not correlate with its location or size.
  • The authors stated that in their model, repeated weekly injections of native crocidolite produce mesotheliomas in 20-30% of mice after 30-50 weeks. The six-week angiogenesis findings therefore came before tumors develop.
• The authors' conclusion: The authors concluded that angiogenesis is a prominent response to injection of mineral fibers known to induce mesotheliomas. They suggested that a new vascular network around asbestos fiber clusters may help neoplastic (tumor) mesothelial cells grow at these sites.
• Limitations the authors state:
  • The authors stated that the identity and source of the factors driving angiogenesis after fiber injection are unknown.
  • Seeing a vascular network directly does not show whether vessel-lining cells are moving or dividing. For this reason, the authors added autoradiography.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile, Crocidolite, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Angiogenesis, Macrophage, Mesothelioma, Crocidolite, Mineral Fiber, Chrysotile.

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