Figure 7.

The process of re-epithelialization. A representative data set was obtained from the dorsal skin of the forearms. (a) Wound margin immediately after operation (Stage 1). (b) Wound epidermis which appeared 6 h after operation. Blue in (a,b): DAPI staining of nuclei. (c,d) Neighboring sections showing the wound epidermis at Stage 2 (12 h after operation). Masson’s trichrome stain. As shown in (d), the region composed of the stratum corneum and a part of the transitional layer was sometimes detached from the extending wound epidermis during sectioning. (e–h) Dendritic melanophores (magenta arrow) in the extending wound epidermis. (e,f) 6 h after operation. (f) is a magnification of a part of (e). (g,h) Stage 2 (12 h after operation). (h) is a magnification of a part of (g). (i) The extending epidermal tongue (EET) 6 h after operation. A view from above. The EET was brown because its constituent cells contained melanin pigments. Following a delay after the wound epidermis started to extend, differentiation of the stratum corneum began from the circumference of the wound. (j,k) Wound epidermis closing around the center of the wound bed 24 h after operation. (k) is a magnification of a part of (j). This is a sagittal section of the forearm. The wave of differentiation of the stratum corneum caught up with the closure of the wound epidermis; however, in this particular case, the stratum corneum and the EET were not integrated into one continuous epithelium. The central hole surrounded by the wound epidermis was filled with white blood cells containing neutrophils and monocytes (arrowheads in the inset). BL: basal layer; GG: granular gland; PCL: pigment cell layer; SC: stratum corneum; TL: transitional layer. Black and white arrows: location of the wound margin. Arrowheads: margin of the stratum corneum and a part of the transitional layer that were left behind the wound epidermis. Asterisks: leading end of the wound epidermis. Scale bars, 50 μm (a–h,k); 100 μm (i,j).