Matrix metalloproteinase 3(MMP-3), also known as stroma-decomposin-1, is encoded by the MMP3 gene in humans. MMP3 expression is regulated primarily at the transcriptional level, where gene promoters respond to a variety of stimuli, including growth factors, cytokines, cancer promoters, and proto-oncogene products. The MMP-3 enzyme degrades types II, III, IV, IX and X collagen, proteoglycans, fibronectin, laminin and elastin. In addition, MMP-3 can also activate other MMPs such as MMP-1, MMP-7 and MMP-9, so MMP-3 plays a key role in connective tissue remodeling. This enzyme is involved in wound repair, atherosclerosis progression and tumor initiation. MMP-3 wild-type and gene-knockout mouse studies have shown that MMP-3 increases blood-brain barrier permeability after traumatic injury. Nuclear MMP-3 functions as a transcription factor and protease.