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Published on: December 13, 2024
Morphologic organization of pulmonary granulomas in mice infected with Paracoccidioides brasiliensis
Fernanda C Da Silva1, Terezinha I E Svidzinski, Eliana V Patussi
1Post-graduate Program in Clinical Analyses, Laboratory of Medical Mycology, Universidade Estadual de Maringá, Maringá, Paraná, Brazil. nandacristie@gmail.com
Abstract:
A morphologic study of the lungs was carried out in Swiss mice infected with yeast isolated from Paracoccidioides brasiliensis (Pb18). The lung was processed 1, 2, 4, and 8 weeks after inoculation for histologic staining with hematoxylin and eosin (H&E), methenamine silver nitrate (Gomori-Grocott), and picrosirius to qualitative and quantitative analyses of the granulomas and the presence of fungal lesions. The numbers of CFUs/g counted in the lungs were 189.8 +/- 20.64, 353.6 +/- 46.21, 547.2 +/- 108.1, and 295.2 +/- 89.17 in the first, second, fourth, and eighth weeks, respectively. One week after infection, inflammatory cells and reticular and collagens fibers, the latest typical of fibrosis, were detected. After 2 and 4 weeks, a progressive intensification of the infection and fibrosis was observed, but in week 8 a more organized granuloma was evident, with macrophages, epithelioid cells, and yeasts in the central portion, and intense peripheral basophilia. Pycnotic structures typical of apoptotic bodies were observed in weeks 1 and 8. The different histologic staining used acted as a fundamental tool for the study of the morphologic organization of granuloma formation.
Insights
This study reveals how Paracoccidioides brasiliensis (Pb18) infection impacts mouse lungs, detailing the formation and organization of granulomas and fibrotic changes over eight weeks. Histologic staining identified key cellular and structural alterations during infection progression.
Area of Science:
- Mycology
- Immunology
- Pathology
Background:
- Paracoccidioides brasiliensis (Pb18) is a fungal pathogen causing paracoccidioidomycosis.
- Understanding the host-pathogen interaction and lung morphologic changes is crucial for disease management.
Purpose of the Study:
- To investigate the morphologic changes in Swiss mouse lungs following infection with Paracoccidioides brasiliensis (Pb18).
- To analyze granuloma formation, fibrosis, and fungal lesion development over an 8-week period.
Main Methods:
- Swiss mice were inoculated with Paracoccidioides brasiliensis (Pb18).
- Lung tissues were collected at 1, 2, 4, and 8 weeks post-infection.
- Histologic staining (H&E, Gomori-Grocott, picrosirius) was used for qualitative and quantitative analysis of granulomas and fungal presence.
- Colony-forming units per gram (CFUs/g) were counted.
Main Results:
- Fungal burden (CFUs/g) peaked at week 4, with significant increases observed from week 1 to week 4.
- Inflammatory cells, reticular fibers, and collagen indicative of fibrosis were detected by week 1.
- Progressive infection and fibrosis intensified by weeks 2 and 4.
- An organized granuloma with macrophages, epithelioid cells, and yeast in the center, alongside peripheral basophilia, was evident by week 8.
- Apoptotic bodies were observed at weeks 1 and 8.
Conclusions:
- Histologic staining techniques are essential for studying the morphologic organization of granuloma formation during Paracoccidioides brasiliensis infection.
- The study elucidates the dynamic process of granuloma development and fibrotic response in the lung over time.
- Findings contribute to understanding the host response to fungal infections and potential therapeutic targets.
