Morphogenetic effects of soluble laminin-5 on cultured epithelial cells and tissue explants

The rat cell line 804G assembles an extracellular matrix which induces not only the rapid adhesion and spreading of epithelial cells but also the assembly of a cell-matrix attachment device called the hemidesmosome. The major component of this matrix is laminin-5. We have purified rat laminin-5 from medium conditioned by 804G cells. Epithelial cells which are co-incubated with medium supplemented with soluble laminin-5 adhere and spread rapidly. Furthermore, human carcinoma cells undergo a dramatic morphologic change in the presence of laminin-5 and form orderly arrays resembling epithelial sheets. Soluble rat laminin-5 is selectively incorporated into an insoluble matrix of epithelial cells in vitro, since rat-specific laminin-5 antibodies stain cell-substrate contacts. Addition of medium containing soluble laminin-5 to explanted, human corneal rims induces assembly of hemidesmosomes, important cell-matrix attachment devices. Furthermore, rat-specific laminin-5 antibodies stain areas of contact between corneal epithelium and basement membrane, indicating that rat laminin-5 from the medium is incorporated into basement membrane. We discuss the use of laminin-5 as a medium supplement for the culture of both epithelial cells and epithelial tissue explants.