Hairless guinea pig skin: anatomical basis for studies of cutaneous biology.

In order to characterize the microscopic anatomy of hairless guinea pig (HL-GP) skin, we utilized light microscopy with a computer-assisted image analysis system, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM revealed that the hair shafts of HL-GPs were thin, short, extremely irregular in diameter and often twisted and curled. The HL-GP epidermis was of similar thickness to that of human skin with distinct strata, serrated/non-serrated basal keratinocytes and shallow dermal papillae. The density of Langerhans cells in epidermal sheets, visualized by adenosine-s-triphosphatase staining, was similar to that of normal-haired guinea pigs (HD-GPs), although the dendrites of HL-GPs were thicker and shorter than those of HD-GPs. The dermal vasculature of HL-GPs was well-developed and similar to that of humans, demonstrating a network of vertically oriented capillary loops. HL-GPs had significantly more dendritic or spindle-shaped dermal interstitial cells than humans and HD-GPs. Collectively, these data suggest that HL-GP skin is more similar to human skin than to the skin of HD-GPs and other rodents and, therefore, the HL-GP may be a useful animal for studying cutaneous biology, experimental pathology, pharmacology and toxicology.