Histological analysis
The left lung tissues of mice fixed in 4% formalin were dehydrated and embedded in paraffin, and the sample blocks were cut into 5 μm for staining. All tissue sections were visualized using a 3D HISTECH digital scanner (Hungary). Hematoxylin and Eosin (HE) staining was performed to assess the degree of lung inflammation using the Szapiel’s method (Szapiel SV, 1979), which included 0 (no inflammation), 1 (mild inflammation), 2 (moderate inflammation), and 3 (severe inflammation ). Masson’s trichrome staining was carried out and the extent of fibrosis was evaluated following the methodology described by King et al (King, 1952). Briefly, the fibrotic damage scores were calculated and, specifically, the different silicotic nodules were first assessed for fibrosis according to King’s method at levels ranging from 0 to 5. Each silicotic nodule then received a corresponding fraction of fibrotic injury calculated as the score of fibrotic level (0­­­­­­­–5) multiplied by its percentage of the total area of the tissue section (Z. Cao et al., 2020).