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In biology, the extracellular matrix (ECM) is a collection of extracellular molecules secreted by cells that provides structural and biochemical support to the surrounding cells. Because multicellularity evolved independently in different multicellular lineages, the composition of ECM varies between multicellular structures; however, cell adhesion, cell-to-cell communication and differentiation are common functions of the ECM. The animal extracellular matrix includes the interstitial matrix and the basement membrane. Interstitial matrix is present between various animal cells (i.e., in the intercellular spaces). Gels of polysaccharides and fibrous proteins fill the interstitial space and act as a compression buffer against the stress placed on the ECM. Basement membranes are sheet-like depositions of ECM on which various epithelial cells rest. The plant ECM includes cell wall components, like cellulose, in addition to more complex signaling molecules. Some single-celled organisms adopt multicelluar biofilms in which the cells are embedded in an ECM composed primarily of extracellular polymeric substances (EPS). == Role and importance == Due to its diverse nature and composition, the ECM can serve many functions, such as providing support, segregating tissues from one another, and regulating intercellular communication. The extracellular matrix regulates a cell's dynamic behavior. In addition, it sequesters a wide range of cellular growth factors and acts as a local store for them.〔 Changes in physiological conditions can trigger protease activities that cause local release of such stores. This allows the rapid and local growth factor-mediated activation of cellular functions without ''de novo'' synthesis. Formation of the extracellular matrix is essential for processes like growth, wound healing, and fibrosis. An understanding of ECM structure and composition also helps in comprehending the complex dynamics of tumor invasion and metastasis in cancer biology as metastasis often involves the destruction of extracellular matrix by enzymes such as serine proteases, threonine proteases, and matrix metalloproteinases.〔 The stiffness and elasticity of the ECM has important implications in cell migration, gene expression, and differentiation. Cells actively sense ECM rigidity and migrate preferentially towards stiffer surfaces in a phenomenon called durotaxis. They also detect elasticity and adjust their gene expression accordingly which has increasingly become a subject of research because of its impact on differentiation and cancer progression. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「extracellular matrix」の詳細全文を読む スポンサード リンク
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