Extracellular Matrix

The extracellular matrix, or ECM, is an organized network of proteins and polysaccharides located outside cells. Cells produce and assemble these molecules into structures that surround, support, and connect cells within tissues. The amount and composition of ECM vary greatly among tissues, from the abundant matrix of bone, cartilage, and tendon to the thin basement membranes that support epithelial layers .^1,2

Major ECM components include collagens, which provide tensile strength, and elastin, which allows some tissues to stretch and recoil. Proteoglycans and glycosaminoglycans form highly hydrated networks that help determine properties such as resistance to compression. Adhesive glycoproteins, including fibronectin and laminins, help organize the matrix and connect it to receptors on cell surfaces .^1,2

The extracellular matrix is not simply passive structural material. Cells attach to ECM molecules through receptors such as integrins, allowing mechanical and biochemical signals to pass between the matrix and cells. The ECM can thereby influence cell adhesion, migration, survival, differentiation, and other aspects of cellular behavior .^1,2

The ECM is continually produced, modified, and degraded in a process called extracellular matrix remodeling. This allows tissues to change during development, normal maintenance, and repair. The extracellular matrix should not be confused with extracellular fluid, which is the fluid outside cells. Although the ECM is highly hydrated and interacts with extracellular fluid, it specifically refers to the organized macromolecular network within the extracellular space .^1,2