The Extracellular Matrix in Development and in Disease

Recent concepts suggest that there are specific interactions between cells and the components of the extracellular matrix. These are mediated via cell surface receptors for the glycoproteins, collagens, and proteoglycans of the matrix. Two types of reactions are postulated. Normal matrix components, that is, those that are indigenous to the tissue, induce functional competence in the cells. Trauma, inflammation, or related reactions induce the production of matrix components more typical of fibrotic tissues. These matrix components cause a shift in cellular activities as they engage cell receptors. Various mechanisms can prolong and augment the fibrotic response, leading to an irreversible loss of tissue structures and function. New methods are available for identifying the cells and species of matrix proteins active in disease states.