EPIDERM™ FULL THICKNESS (EPIDERMFT™), A DERMAL/EPIDERMAL SKIN EQUIVALENT WITH A FULLY DEVELOPED BASEMENT MEMBRANE.

Paracrine signaling between dermal fibroblasts and epidermal keratinocytes is believed to modulate skin responses during contact irritant or allergic reactions. Dermal fibroblasats also play an important role in photo-aging and photo-damage, wound healing and cancer progression. To enable in vitro study of these and other dermal phenomena in which fibroblast-epidermal keratinocyte interactions are important, a full thickness skin model (EpiDermFT) composed of a fibroblast-containing dermis/keratinocyte-containing epidermis has been developed. In normal healthy skin in vivo, attachment of epidermis to dermis occurs via integrin receptors on basal keratinocytes, which bind to the basement membrane at the dermal/epidermal junction. Integrin binding at the dermal/epidermal junction is also involved in numerous signal transduction pathways related to inflammation, tissue remodeling, apoptosis, growth and tumorigenesis. However, basement membrane development is seldom achieved in vitro. Thus, the ultrastructure of the EpiDermFT dermal/epidermal junction was also examined by transmission electron microscopy. The presence of specific basement membrane structural proteins was also examined by immunohistochemistry. Histologic examination of the EpiDermFT tissue shows a collagen dermis populated by numerous viable fibroblasts and an epidermis consisting of stratified keratinocytes including basal, spinous, granular and stratum corneum components. Examination of ultrastructure at the dermal/epidermal junction by transmission electron microscopy revealed a well-developed basement membrane. Hemidesmosomes were observed at the basal membranes of keratinocytes, with associated tonofilaments extending into the cytoplasm. Well-defined, continuous lamina densa, lamina lucida and fine anchoring filaments were present beneath the basal keratinocytes. Anchoring fibrils with characteristic striated structure connected the lamina densa to the underlying collagen matrix. Immunohistochemical analysis of basement membrane proteins was also performed. Protein markers of hemidesmosomes (a-6 integrin), lamina lucida (laminin 5), lamina densa (collagen IV) and anchoring fibrils (collagen VII) were specifically localized to the dermal/epidermal junction. EpiDermFT overcomes shortcomings of previous models in terms of providing a wall-to-wall tissue as well as appropriate in vivo-like basement membrane development. These attributes will enable more realistic in vitro toxicological studies of dermal/epidermal phenomena.

Allergic reactions, Anchoring fibrils, Anchoring filaments, Basement membrane, Cancer, Collagen, Collagen dermis, Collagen matrix, Contact irritant reaction, Dermal fibroblasts (FB), Dermal phenomena, Dermal/epidermal junction, Dermal/epidermal phenomena, ELISA, EpiDerm-FT, EpiDermFT, Epidermal keratinocytes (KC), Epidermis, FB-KC interactions, FB-containing dermis, Fine anchoring filaments, Full thickness, Hemidesmosomes, In vitro toxicological studies, In vivo-like basement membrane, KC-containing epidermis, Lamina densa, Lamina lucida, MMP, MMP-1, Paracrine signaling, Photo-aging, Photo-damage, Pro-MMP-1, Stratified KC, Stratum corneum, Sunburn cells, TEM, Tonofilaments, Transmission electron microscopy, UVA, UVB, Ultrastructure, Ultraviolet irradiation (UVR), Wound healing