The bilayered bioengineered skin substitute (BBSS) is comprised of an epidermal layer formed from human keratinocytes and a dermal layer composed of human fibroblasts in a bovine type I collagen matrix. The fibroblasts in the dermal layer are mitotically and metabolically active, and secrete collagen and other matrix components.
BBSS does not contain any antigen-presenting cells such as Langerhans cells, dermal dendritic cells, endothelial cells or leukocytes.
BBSS is manufactured from human neonatal foreskins. The fibroblasts and keratinocytes are isolated and then serially cultured under separate tissue culture conditions to establish cell banks. Fibroblasts are seeded on a semipermeable membrane along with bovine type I collagen. They expand and then contract the collagen filaments to form a dermal matrix within approximately 6 days. The epidermal layer is formed by seeding the keratinocytes onto the surface of this contracted dermal matrix and allowing them to proliferate. After 4 days, the skin culture is incubated at the air-liquid interface for 7-10 days to promote keratinocyte differentiation and the formation of a stratum corneum. The bovine type I collagen is extracted from cattle herds bred and raised in the US.