EXTRACELLULAR MATRIX PROTEINS

The extracellular matrix is a complex network of secreted (glyco)proteins situated in between cells of particular types of tissue. The relative amounts of the different types of matrix macromolecules and the way in which they are organized in the extracellular matrix vary between different tissues. For example, connective tissues have extensive extracellular matrices in which fibrous polymers, especially collagen, are present. In contrast, in epithelial tissues the extracellular matrix consists only of a thin mat called the basal lamina, which underlies the epithelial cell sheet. Cells located in the extracellular matrix produce matrix constituents and control the organization of these matrix components. The main components of the extracellular matrix are proteoglycans (e.g. aggrecan, perlecan and syndecan) and fibrous proteins (e.g. collagen, elastin, fibronectin and laminin). The extracellular matrix, next to being a scaffold to support cells in a particular tissue, also plays a role in the regulation of processes such as proliferation, differentiation, adhesion and locomotion of these cells.