Development and characterization of a canine skin equivalent

The development of a complex cellular model, which incorporates the basic cell components of the dog skin, would be a useful tool to investigate the biology and pathology of canine skin and also to replace animal testing partially. The aim of the present study was to develop and characterize a canine skin equivalent. Epidermal keratinocytes and dermal fibroblasts were freshly isolated from skin biopsies from healthy dogs. Fibroblasts were embedded into a bio-matrix from collagen type I matrix protein; this built the scaffold where the keratinocytes were seeded, at air exposed conditions. At 3, 7, 15 and 21 days of culture in special growth media, skin equivalents were analysed by histological, immunohistochemical and electron microscopical techniques. At 15 days, keratinocytes underwent differentiation to a multilayer epidermis with stratum basal, stratum spinosum, stratum granulosum and stratum corneum. Expression of epidermal cytokeratins in keratinocytes was detected by immunhistochemistry, and followed the same pattern than in the normal canine epidermis. Fibroblasts from the skin equivalent expressed vimentin as dermal fibroblasts do. A basement membrane (BM) was observed underneath the epidermis; ultrastructurally, it was similar to the normal canine BM and collagen IV and laminin 5 were detected immunohistochemically as major components of this structure. Skin equivalents developed from canine cutaneous cells presented a similar morphological structure than healthy canine skin. Moreover, the immunohistochemical analysis revealed the expression of the major markers of the epidermis (keratins), dermis (vimentin) and BM (collagen type IV, laminin 5).