Reconstruction of basement membrane in skin equivalent; role of laminin-1

To reconstruct the basement membrane in a skin equivalent, the epidermoderm al interface was coated with porcine type IV collagen and mouse laminin-1 a t various ratios before keratinocyte seeding. Laminin-1, a component of the basement membrane, induced massive infiltration of keratinocytes into the dermal equivalent, while type IV collagen induced discrete demarcation betw een dermal and epidermal compartments without any infiltrating cells. Immun ohistochemical staining indicated that the laminin-induced infiltrating cel ls expressed endogenous type IV collagens at the cell periphery, which were not incorporated into the basement membrane structure. The infiltrating ce lls did not express fibronectin receptor alpha (5)beta (1) integrin but sho wed MMP-9 secretion and cell surface associated MMP-2. However, when lamini n-1 was preincubated with type IV collagen, laminin-1-induced keratinocyte infiltration as well as MMP-9 induction were almost completely suppressed t o basal levels. Therefore, replenishment of the type IV collagen lattice se emed to cause laminin-stimulated cells to anchor to the lattice, in a simil ar manner to the basal cells on the basement membrane of normal skin. Our s tudy suggests that the molar ratio of basement membrane components may dete rmine the behavior of basal cells within the wound healing microenvironment , which is probably regulated either by extracellular matrix deposition or degradation.