FN1 and pulmonary fibrosis: Furthermore, in pulmonary fibrosis, upregulation of PDGF-B promotes COL1A1, COL3A1, and FN1 expression by activating the PI3K/AKT pathway, closely linked to pulmonary fibrosis pathogenesis (Peng et al., 2024; Aono et al., 2014; Noskovičová et al., 2015).