Different mechanisms in the attachment of cells to native and denatured collagen

The attachment of cells to collagen has been reported previously to require the presence of serum and the particular serum protein involved in this process, variously known as CIG, CAP or fibronectin, has been isolated. This conclusion that cell attachment to collagen requires serum (or more precisely, fibronectin) is based on experiments measuring the kinetics of cell attachment to films of collagen. We have measured the kinetics of attachment of HeLa and attachment to films of collagen-containing substrata under a variety of experimental conditions and present evidence that the serum-dependent mechanism of cell attachment described by others is actually only the case for films of denatured collagen, while cell attachment to native collagen fibres occurs by a different, serum-independent, mechanism. The possible relevance of these findings to cell-matrix interactions in vivo is discussed.