extracellular matrix

(= ecm; ECM)

Any material produced by cells and secreted into the surrounding medium, but usually applied to the non-cellular portion of animal tissues. The ecm of connective tissue is particularly extensive and the properties of the ecm determine the properties of the tissue. In broad terms there are three major components: fibrous elements (particularly collagen, elastin, or reticulin), link proteins (eg. fibronectin, laminin), and space-filling molecules (usually glycosaminoglycans). The matrix may be mineralised to resist compression (as in bone) or dominated by tension-resisting fibres (as in tendon). The basal lamina of epithelial cells is another commonly encountered ecm. Although ecm is produced by cells, it has recently become clear that the ecm can influence the behaviour of cells quite markedly, an important factor to consider when growing cells in vitro : removing cells from their normal environment can have far-reaching effects.