The extracellular matrix or ECM is the structural and functional substance that surrounds cells in nearly all tissues in the body. A three-dimensional matrix, ECM supports cells in addition to playing other vital roles. While the composition of the ECM varies by tissue, it is generally composed of four major types of molecules:
In natural living tissue, collagen, which provides the main structural framework, is the most abundant protein in the ECM. Glycoproteins, such as fibronectin, help to bind cells to the collagen, which allows the cells to move through the matrix. GAGs and proteoglycans keep the matrix well hydrated by absorbing water and also bind growth factors, which are important for cell signaling. Matricellular proteins add additional functional utility to the ECM.
