ABSTRACT
The matrix metalloproteinases (MMP) are a family of highly conserved zinc-dependent endopeptidases which collectively are capable of degrading components of the extracellular matrix (ECM). The pre-domain is found at the amino terminus of all MMPs and is rapidly removed prior to secretion. The constitutive level of MMP expression is normally low, the enzymes being induced under various physiological circumstances when ECM remodeling is required. MMPs have been implicated in a number of pathological conditions including rheumatoid arthritis and artherosclerosis, but it is their role in tumor invasion and metastasis which has been most extensively studied. Development of the human fetus depends primarily on the embryo rapidly gaining access to the maternal circulation, and the embryo achieves this by using specialized cells referred to as trophoblasts. The complexity of expression patterns in normal tissues is demonstrated by examples of cell type-and tissue-specific regulation, inducible and constitutive expression and discrepancies between in vitro and in vivo studies.
