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Pathogenesis of experimentally induced asbestos mesothelioma in rats
L A Vasilieva1, L N Pylev, Y A Rovensky
1Laboratory of Natural Carcinogens, Cancer Research Center, Russian Academy of Medical Sciences, Moscow.
Abstract:
Fragments of parietal and visceral pleura were studied by total films preparation, light microscopy and SEM at different times after intrapleural injection of asbestos in Wistar rats. Pleural rat mesothelium in histological slices consists normally of one layer of oblong cells. By SEM the cells are flat and coated with microvilli of different lengths. In total films the parietal mesothelium was composed of large polygonal cells covering intercostal spaces and small cells covering spaces over the ribs. Inflammatory reaction and permanent pathological regenerative processes were observed in the mesothelium during 24 months after inoculation of asbestos fibres. Different lesions which we regarded as preneoplastic or premesotheliomatous were observed against the background of or without these processes. They were diffuse irregular hyperplasia and proliferation of epithelium-like or fibroblast-like cells and focal nodous proliferates composed of such cells with various morphological structures. The number of thymidine-labelled cells was significantly more inside the proliferates than in the surrounding tissue. They were confirmed by SEM and histological slices of the same fields. Chronic pathological regeneration of pleural mesothelium could be the background against which preneoplastic lesions and mesotheliomas develop easily.
Insights
Asbestos exposure in rats causes chronic inflammation and cell changes in the pleura, leading to preneoplastic lesions. These findings suggest pathological regeneration may precede mesothelioma development.
Area of Science:
- Pathology
- Toxicology
- Cell Biology
Background:
- The pleura, a serous membrane lining the thoracic cavity, is susceptible to asbestos-induced damage.
- Asbestos exposure is a known risk factor for mesothelioma, a rare cancer of the pleura.
Purpose of the Study:
- To investigate the long-term effects of asbestos fibers on rat pleural mesothelium.
- To identify potential preneoplastic changes in the pleura following asbestos exposure.
Main Methods:
- Intrapleural injection of asbestos fibers into Wistar rats.
- Analysis of pleural tissue using total film preparation, light microscopy, and scanning electron microscopy (SEM).
- Assessment of cell proliferation using thymidine labeling.
Main Results:
- Asbestos induced inflammatory and pathological regenerative processes in the pleural mesothelium over 24 months.
- Observed preneoplastic lesions included diffuse hyperplasia and focal nodular proliferates of epithelium-like or fibroblast-like cells.
- Increased thymidine-labeled cells were found within these proliferates, indicating active cell division.
Conclusions:
- Chronic pathological regeneration of pleural mesothelium serves as a background for preneoplastic lesion development.
- These findings highlight the potential for asbestos-induced mesothelial changes to progress towards mesothelioma.