Figure 3.

Histologic biopsies illustrating normal and burned human skin. Images (a), (c), (e) and (g) are hematoxylin and eosin (H&E) stained (scale bar 500 μm). Images (b), (d), (f) and (h) are lactate dehydrogenase (LDH) stained (scale bar 500 μm) with viable cells stained blue. Images (a) and (b) illustrate normal tissue histology, with a dotted line representing the interface between the papillary and reticular dermis. The pilosebaceous unit (PSU) (dotted rectangle), composed of a hair follicle, arrector pili muscle and associated sebaceous gland, extends from the epidermis into the dermis. Dotted circles represent eccrine gland structures, which together with the PSU form the regenerative niches needed for wound healing. Images (c) and (d) represent superficial partial-thickness burns (SPTB) with complete absence of epithelial cells and minor involvement of the papillary dermis. In contrast, images (e) and (f) depict a deep partial-thickness burn (DPTB) with severe loss of epidermal and dermal epithelium. Note that the arrows in both SPTB and DPTB point to the remaining regenerative characteristic of second-degree burns. Images (g) and (h) represent a full-thickness burn with no visible regenerative potential. Copyright permission obtained from Karim et al. [11]