ACTA1 and interstitial lung disease: Genetic knockdown of PAD2 in RA-ILD fibroblasts resulted in decreased α-SMA protein expression (Fig. 2D), gel contractility which led to an increase in gel area (Fig. 2E), and COL1A1 and FN expression (Fig. 2F) compared to scrambled shRNA (Scr)-transfected cells.