To estimate the expression level of bleomycin-specific key genes in the lungs of mice with asthma and asthma-associated fibrosis, pan-fibrotic regulator Col1a1 as well as Col4a1, Col4a2, Thbs2, and Tyrobp—novel pulmonary fibrosis marker candidates poorly investigated as lung fibrosis-related genes and associated only with hepatic or renal fibrosis—were chosen for qRT-PCR analysis. This evidence concerns the gene COL4A1 and pulmonary fibrosis.