Matrix MetalloProteinases (MMPs) are endopeptidases – a subfamily of proteolytic enzymes or proteases – that are capable of degrading proteins into recyclable fragments. MMPs in the skin regulate the balance of synthesis and breakdown of extracellular matrix proteins such as collagen, elastin, and others. As we all realize that –  it is the condition and health of our skin matrix that is responsible for the skin’s youthful appearance including firmness, strength, suppleness and elasticity. The signs of skin aging reflect the condition of the skin matrix – the weaker and less regular the matrix, the more wrinkles, roughness and sag one tends to have. The functions of MMPs include: break down damaged or worn out structural proteins; facilitate the second phase of wound healing; clear pathways for migrations of immune cells to infected areas in an inflammatory response. In the skin, MMPs’s primary role is to recycle skin matrix, especially the structural proteins collagen and elastin. Different versionsof MMPs (the discovered MMP have 28 variations) targets different substrates such as collagen I, II, III, V, VI and XII, elastin, and etc. The following table shows the MMPs which targets key skin matrix protein collagen and elastin.

MMP-1   Collagens I, II, III, VII and X

MMP-2  Gelatins, Collagens I, IV, VII and XI, Fibronectin, Laminin, Elastin

MMP-3  Aggrecan, Gelatin, Fibronectin, Laminin, Collagens III, IV, IX and X

MMP-8  Collagens I, II, III, Link protein, Aggrecan

MMP-9  Gelatins, Collagens IV, V and XIV Aggrecan, Elastin

MMP-12  Elastin

MMP-13 Collagens I, II, III

MMP-14  Collagens I, II and III, Laminin

MMP-18  Collagens I

The damaged matrix needs to be degraded and recycled in response to skin tissue injury or in an inflammatory reaction triggered by environmental stresses (sun damage, smoking, pathogen invasion, glycation and etc). Otherwise, damaged skin structural proteins (collagen and elastin) would accumulate, leading to skin imperfections. It is found that aging, (chronic) inflammation and other external or environmental factors can increase the MMPs level in the skin, this will shift the balance of skin matrix toward excess collagen and elastin destruction. When new collagen and elastin synthesis can not makeup for the damage, wrinkles/fine lines, sags and dull skin will be formed.

Research indicates that inhibiting or suppressing elevated MMP enzymes down to normal levels should be a part of optimal skin rejuvenation strategy, especially as one ages. The easiest and least expensive strategies of preventing skin matrix deterioration is to avoid environmental factors that stimulate the production of MMPs via proper life style habits (proper diets, no smoking, and etc) although avoiding environmental stressors is not always possible. Scientists have been looking for and developing MMP inhibitors as the topical ingredients to be added to the arsenals of anti-wrinkle ingredients. Many of the well-known skin rejuvenation treatments are aimed at replenishing skin matrix by stimulating the synthesis of collagen or elastin while the opposite – inhibition of collage and elastin degradation via inhibition of MMPs activities gets less attention. Since research indicates that MMP levels rise excessively with age, it makes sense to try to return MMP to its normal level.

Doxycycline hyclate (Periostat) is a MMP inhibitor available as a drug which inhibits MMP-1 (i.e. type I collagenase) and possibly also MMP-2, MMP-8 and MMP-9. The approved indication of doxycycline hyclate is periodontal disease, however.  Some plant extracts have been shown to inhibit MMP enzymes. There are also evidence that tea extract may inhibit MMP.  Hydrolyzed soy protein (a.k.a. soy peptide complex or soy hydrolysate) appears to inhibit some MMP enzymes. These ingredients are no new ingredients. They have other anti-aging skin care properties.

Dr. Patricia Wexler M.D skin care line has a series of products (for example, Patricia Wexler 3 in 1 Intensive Day Cream SPF 30) are developed based on the idea of MMP inhibition – the so called MMPi technology. According to Dr. Wexler’s website, studies have been done to show that MMPi technology really works. She measured a reduction in MMP production but there’s no data on how the skin itself was affected. In other words, did she prove her products have a beneficial effect on skin or did she only prove her products react a certain way in laboratory tests? MMPi technology is discussed in further detail in another post.