Histology
We obtained the dorsal skin tissue of the mice after taking pictures at day 7. The obtained tissues were fixed overnight in 4 % formaldehyde at 4℃, dehydrated in ethanol, embedded in paraffin, and cut into 6 μm-thick sections for H&E staining. Skin paraffin sections were baked at 60℃ for one hour before staining. The sliced sections were imaged with a bright-field microscope (Eclipse Ti-S; Nikon) with a charge-coupled device camera (DS-Ri2; Nikon).