Regulation of basement formation in skin-organotypic coculture
The basement membrane (BM) development and assembly and the interactions between the single components (laminin, nidogen, type IV collagen and perlecan), was investigated in a skin-organotypic 3D-coculture model, consisting of epidermal cells growing on a type I collagen matrix with incorporated fibroblasts. Nidogen deficiency was fatal for the BM-formation; absence of nidogen-1 and -2 caused failure of assembly of laminin-10, type IV collagen and perlecan. Also the epithelial anchoring complexes did not develop in the basal cells. In addition, laminin-5 was clearly disturbed. Application of recombinant nidogen-1 or -2 fully restored the BM. Inhibition of the laminin-nidogen complex also disturbed the BM-assembly process. In both cases, the BM-proteins were detectable in the respective tissue compartments, indicating that nidogen might act as a molecular adapter facilitating binding of laminin to cells, or catalyze the initial polymerization steps of the BM-components. Perlecan deficiency did not interfere with BM-assembly, probably being compensated for by a similar molecule. These findings indicate that the BM-components nidogen-1 and -2 are crucial for BM-formation in the skin and that the nidogen-laminin complex may not only be an initial trigger for the assembly of other BM-components, but also for intracellular adhesion complexes.