The Annexin V/PI double staining indicates that lung fibroblast apoptosis is promoted by THY1 up-regulation and WNT signaling pathway inactivation. *, p < 0.05 vs. the normal group; #, p < 0.05 vs. the NC and AIP groups; PI, propidium iodide; THY1, thymocyte differentiation antigen-1; AIP, acute interstitial pneumonia; NC, negative control.