Moreover, the validation of genes regulating pulmonary fibrosis of non-allergic etiology (bleomycin-induced lung fibrosis) on asthmatic and asthma-driven fibrotic lungs allows us to identify new promising universal genes (Col4a1 and Col4a2) involved in the development of pulmonary fibrosis regardless of its etiology. Here, COL4A1 is linked to pulmonary fibrosis.