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Ultrastructural analysis of pulmonary alveolar proteinosis induced by methylnaphthalene in mice
Abstract:
Pulmonary alveolar proteinosis was induced at a 100% incidence in B6C3F1 female mice by twice weekly painting the back skin with methylnaphthalene for 30 weeks to give a total dose of 7.14 g/kg b.wt. Semithin sections were used for defining areas of type II pneumocyte hyperplasia and hypertrophy and associated proteinosis. Ultrastructurally, alveolar spaces were found to be filled with numerous myelinoid structures resembling the lamellar bodies of type II pneumocytes. Mononucleated giant cells (balloon cells, BC) containing numerous myelinoid structures, lipid droplets and many electron dense amorphous ascicular crystals were closely associated with this extracellular membranous material. Stacks of elastic fibers stained with tannic acid and bundles of collagen fibers were loose and discontinuous in the interstitium of affected areas. The following pathogenesis is hypothesized: type II pneumocytes produce increased amounts of lamellar bodies due to their hyperplasia and hypertrophy and develop to form BC which liberate numerous myelinoid structures on their rupture. Epidermal absorption of methylnaphthalene is an efficient reliable method of induction of this internal disease.
Insights
Methylnaphthalene effectively induced pulmonary alveolar proteinosis in mice by affecting type II pneumocytes. This study details the cellular changes and proposes a pathogenesis involving lamellar bodies and balloon cells.
Area of Science:
- Toxicology
- Pulmonary Pathology
- Cell Biology
Background:
- Pulmonary alveolar proteinosis (PAP) is a rare lung disease characterized by the accumulation of surfactant-like material in the alveoli.
- The pathogenesis of PAP is not fully understood, with various factors implicated in its development.
- Investigating reliable methods for inducing PAP in animal models is crucial for studying its mechanisms and potential treatments.
Purpose of the Study:
- To establish an efficient and reliable method for inducing pulmonary alveolar proteinosis in a mouse model.
- To investigate the ultrastructural changes in the lungs following methylnaphthalene exposure.
- To elucidate the cellular pathogenesis of methylnaphthalene-induced pulmonary alveolar proteinosis.
Main Methods:
- B6C3F1 female mice were topically administered methylnaphthalene twice weekly for 30 weeks.
- Total dose administered was 7.14 g/kg body weight.
- Lung tissues were examined using semithin and ultrathin sections for light and electron microscopy.
Main Results:
- Methylnaphthalene induced pulmonary alveolar proteinosis with 100% incidence in exposed mice.
- Histological analysis revealed type II pneumocyte hyperplasia and hypertrophy, and protein accumulation.
- Ultrastructural examination showed alveolar spaces filled with myelinoid structures, resembling lamellar bodies, and mononucleated giant cells (balloon cells) containing these structures and crystals.
Conclusions:
- Epidermal absorption of methylnaphthalene is an effective method for inducing pulmonary alveolar proteinosis in mice.
- The study hypothesizes that methylnaphthalene exposure leads to type II pneumocyte hyperplasia and hypertrophy, increased lamellar body production, and subsequent formation and rupture of balloon cells, releasing myelinoid structures.
- These findings provide a valuable model for studying PAP pathogenesis and exploring therapeutic interventions.