Bilayered cell therapy (BCT) is a live product, constructed of type I bovine collagen (extracted and purified from bovine tendons), viable allogeneic human fibroblasts and keratinocytes isolated from human foreskin. BCT is morphologically, biochemically, and metabolically similar to human skin. However, the dermo–epidermal junction is flatter in BCT than in normal human skin, but the cell proliferation rate is similar to that of human skin. The basal keratinocytes of the epidermis and in the fibroblasts within the matrix are mitotically active. The device is supplied as a circular disc (7.5 cm in diameter and 0.075-cm thick) on a clear plastic tray of gelled support medium (agarose) stored at room temperature.
The dermal layer is formed in vitro by combining fibroblasts with collagen, serum, and tissue culture medium in a special mold that limits lateral contraction. The collagen assembles into a gel in which human fibroblasts are interspersed, and these fibroblasts contract the network of collagen fibers. A suspension of keratinocytes is added to the surface of the collagen fibroblast layer and, after several days of growth, it is submersed in tissue culture medium. At this time, the surface of the BCT is exposed to the air to promote epidermal differentiation. After 7 to 10 days of incubation under these conditions, a mature, cornified epidermis develops at the air–liquid interface.
EMBRYONIC DEVELOPMENT & STEM CELL COMPENDIUM
