Pericytes on the dermal microvasculature of the rat skin.

Surface morphology of pericytes of the subepidermal capillary network of rat skin was studied by scanning electron microscopy. Pericytes showed considerable variation in shape, one end of the spectrum representing a fusiform cell body and lateral projections, the other end a club-like, undulated appearance. Most cells of whatever form were disposed parallel to the capillary course and aligned on the dermal side of the vessels. The pericytic processes encompassed up to half of the endothelial circumference, and were not tapered but spatulated at the ends; the cells adhered to the vessel wall only in certain areas. These findings, together with our previous observation that the subepidermal capillaries exhibit fenestrations mainly at the epidermal side of the endothelial lining, suggest a possible functional role of the pericyte in control of material exchange through the vessel wall. The lateral processes of the fusiform pericytes may, by contraction, cause thinning of the capillary endothelium and the formation of fenestrae, while the club-like pericytes may straighten and push the capillary towards the epidermis, if pericytes are indeed contractile cells, as recent studies indicate.