[The extracellular matrix: from supporting tissue to regulation of cytokines]

Extracellular matrix is a polymorphic structure composed of at least thirty molecules (collagens, glycoproteins, elastin, and proteoglycans) associated in a complex network. This insoluble structured framework ensures tissue cohesiveness, and allows cells to adhere, migrate and interact. Together with cytokines extracellular matrix is also involved in the control of various aspects of cell activities. Cytokines mediate cell to cell communication. Their broad effect result from their pleiotropic and overlapping activities. Once secreted, these molecules diffuse between cells--i.e. across extracellular matrix--to reach their target cells. An increasing number of cytokines are now known to bind to the extracellular matrix. These interactions change the availability of cytokines on effector cells, activate some growth factors, localize and/or increase the duration of the expected effect. Matrix-cytokines interactions are a new field of investigation which has changed our view on extracellular matrix. First considered as a supporting tissue, extracellular matrix appears now to be critically involved in the regulation of cytokine activities.