Histology and ultrastructure of serially transplanted rat mesotheliomas

Our plain-English summary of Histology and ultrastructure of serially transplanted rat mesotheliomas, by J.C. Wagner, N.F. Johnson, D.G. Brown, et al (British Journal of Cancer, 1982).

The study

• Authors: J.C. Wagner, N.F. Johnson, D.G. Brown, M.M. Wagner
• Journal: British Journal of Cancer
• Published: 1982;46(2):294-9
• Cited by: 15 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Summary of the article

This short communication described how the microscopic appearance of rat pleural mesotheliomas changed over repeated transplantation. Syngeneic PVG/C Norwegian hooded rats (26 males and 17 females, aged 6-7 weeks) were given an intrapleural injection of 20 mg of UICC crocidolite. Seven pleural mesothelioma tumour lines were established and maintained by subcutaneous serial passage, six of them for more than 20 generations. Tissue from primary tumours and from random tumour generations was examined by light microscopy, including staining for hyaluronic acid. Eight tumour generations were also examined by electron microscopy. All primary tumours were of mixed cell type. Three were mainly epithelial, three were predominantly spindle-celled, and one was an equal mixture that became predominantly spindle-celled. Some tumour lines alternated between mainly one cell type and the other in successive generations. A high mitotic rate was noted for all tumours by the third generation. The average time to reach the required size fell from 65 days in the first two generations to 35 days in later generations. Electron microscopy showed cells ranging from poorly differentiated epithelial-like cells to well-differentiated mesodermal cells. The secretory tumour contained intracellular lumens lined with microvilli. The authors concluded that the dimorphic pattern characteristic of mesotheliomas was maintained after subcutaneous transplantation. They also described a primitive cell with few distinguishing features and discussed its possible origins.

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In plain English

This short communication described the microscopic appearance of rat pleural mesotheliomas that were passed from rat to rat by transplantation. Twenty-six male and 17 female PVG/C Norwegian hooded rats, aged 6-7 weeks, received an injection into the chest cavity (intrapleural injection) of 20 mg of UICC crocidolite. Seven pleural mesothelioma tumour lines were established. They were kept going by repeated transplantation under the skin of genetically matched rats. The authors examined random tumour generations by light microscopy, and 8 also by electron microscopy. All the primary tumours were of mixed cell type. Some lines stayed mainly epithelial and some mainly spindle-celled. Three alternated between the two cell types in later generations. A high rate of cell division was noted in all tumours by the third generation and was always associated with immature areas. The average time to grow to the required size was 65 days for the first two generations and 35 days for the following 20-25 generations, with much variation; Me7 took 45 days. The authors concluded that the two-cell-type pattern typical of mesothelioma was kept after transplantation. They also described a primitive cell with few distinguishing features.

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: asbestos-induced rat pleural mesotheliomas serially transplanted under the skin and examined by light and electron microscopy (short communication)
• Who was studied: Syngeneic PVG/C Norwegian hooded rats (26 males and 17 females, aged 6-7 weeks) from Glaxo Laboratories; 7 pleural mesothelioma tumour lines established and serially transplanted
• Exposure: A single intrapleural injection of 20 mg of UICC crocidolite in saline
• Main results:
  • All the primary tumours were of mixed cell type.
  • Three primary tumours (Me1, Me2 and Me6) were mainly epithelial. Me2 and Me6 secreted hyaluronic acid. Me1 and Me6 remained epithelial, with undifferentiated cells, for most generations.
  • Three tumours (Me4, Me7 and Me9) were predominantly spindle-celled. In Me7 this cell type remained predominant, with many well-differentiated cells.
  • Primary tumour Me5 was an equal mixture of epithelial and spindle cells. It became predominantly spindle-celled through the generations, with mostly immature cells.
  • Me2, Me4 and Me9 alternated between mainly one cell type or the other in following generations.
  • A high mitotic rate was noted for all tumours by the third tumour generation. It was always associated with areas showing immaturity.
  • The average time to grow to the required size was 65 days for the first and second generations and 35 days for the following 20-25 generations, with much variation. For Me7 it was 45 days.
  • Electron microscopy showed cells ranging from poorly differentiated epithelial-like cells to well-differentiated mesodermal-looking cells.
  • In the secretory tumour, electron microscopy showed cells with intracellular lumens containing microvilli.
• The authors' conclusion: The authors concluded that the dimorphic (two-cell-type) picture characteristic of mesotheliomas was maintained after subcutaneous transplantation. It appeared both with the two cell types present at once and with one cell type reappearing as dominant after several generations. They also described a primitive cell with few distinguishing features among unorganized sheets of epithelial cells with a high mitotic rate.
• Limitations the authors state:
  • The dominant cell type recorded for each generation was based on one section only. Small areas of clefts and papillae seen in several tumours were not shown in the figure, which shows the dominant cell only.

Topics

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

Medical terms in this study, explained in our Lexicon: Histology, Mesothelioma, Pleural Mesothelioma, UICC, Crocidolite, Hyaluronic Acid, Well-Differentiated.

Related studies

• Acute and chronic effects of intraperitoneal injection of two types of asbestos in rats with a study of the histopathogenesis and ultrastructure of resulting mesotheliomas — M.L. Shin, H.I. Firminger (1973)
• Failure to demonstrate tumour-associated transplantation antigens on asbestos-induced mesotheliomas in rats — D.G. Brown, J.C. Wagner, et al. (1980)
• Further observations on the ultrastructure and chemistry of the formation of asbestos bodies — J.M. Davis (1970)
• Ultrastructure of the lung in the rat following exposure to crocidolite asbestos and quartz — K. Miller, I. Webster, et al. (1978)
• The histopathology and ultrastructure of pleural mesotheliomas produced in the rat by injections of crocidolite asbestos — J.M. Davis (1979)
• Ultrastructure of mesothelial regeneration after intraperitoneal injection of asbestos fibres on rat omentum — S. Gonzalez, J. Friemann, et al. (1991)

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