The most significantly increased protein in IPF alveoli was Rho guanine nucleotide exchange factor 7 (ARHGEF7), which is a guanine exchange factor for Rac1 and Cdc42 (19); Cdc42 knockout in alveolar type II cells (AT2) drives periphery-to-center lung fibrosis (20). Here, CDC42 is linked to pulmonary fibrosis.