Matrix metalloproteinases

Matrix metalloproteinases (MMP) are underappreciated players in the skin physiology. MMP are a special subclass of the so-called proteolytic enzymes or proteases, the enzymes whose function is to break down other proteins into recyclable fragments. Matrix metalloproteinases tend to predominantly digest the proteins found in extracellular matrix, the structural framework inside which our cells our housed.

MMP are ubiquitous throughout the body and have many roles: they break down damaged or worn out structural proteins, facilitate the second phase of wound healing, clear pathways for movement of immune cells to infected areas, and so forth. In the skin, the primary role of MMP enzymes is to recycle skin matrix, particularly the structural proteins collagen and elastin.

MMP enzymes vary in their preferred targets, i.e. each tends to primarily digest particular types of proteins. Therefore, the MMP enzymes that target key structural skin matrix proteins (collagen type I and III, elastin, and, to a smaller degree, collagen types V, VI and XII -- see our article on collagen for more details) are particularly important for skin health and rejuvenation. While at least thirty different MMP enzymes have been discovered, much fewer have significant impact on skin matrix: MMP-1, MMP-2, MMP-8, MMP-9, MMP-12, MMP-13 and possibly a few others (see table below).

Why knowing about MMP enzymes is useful? Consider this: the smoothness, firmness and youthfulness of your skin depend to a large degree on the condition of its matrix, which, in turn, depends on the balance of matrix synthsis and breakdown/recycling. MMP enzymes are responsible for the latter side of this balance. If breakdown/recycling stops, damaged matrix will accumulate, leading to skin imperfections. However, the opposite problem, excessive destruction of matrix due to elevated levels of MMP, is far more common. MMP levels tend to increase in the course of normal aging. Additionally, inflammation, irritation and environmental factors may also elevate MMP levels. Research indicates that inhibiting or suppressing elevated MMP enzymes down to normal levels (i.e. levels seen in young adults) should be a part of optimal skin rejuvenation strategy, especially in older individuals. To learn what can be done in paratice to that end, see our article on MMP inhibitors.