Parts of skin tissue of the subjects were collected, fixed by 4% paraformaldehyde, dehydrated by gradient ethanol and normal butanol and sliced into 5 μm sections. Afterward, the sections were supplemented with 100 μL 5% bovine serum albumin, 100 μL primary antibody THBS1 (1:200; ab93653; Abcam Inc., Cambridge, MA) and biotin‐labeled goat anti‐rabbit secondary antibody working solution (1:100; HY90046; Hengyuan Biological Technology Co Ltd, Shanghai, China), and streptomycin anti biotin peroxidase solution (Zhongshan Biotechnology Co, Beijing, China).