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Hyaluronic acid: Skin matrix health is not just about proteins
Hyaluronic acid and aging
Hyaluronic acid-based fillers
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Hyaluronic acid: Skin matrix health is not just about proteins

From www.SmartSkinCare.com

The skin matrix is what would remain if you took the dermis (the fibrous middle layer of the skin) and removed all cells from it. The skin matrix is responsible for structural integrity, mechanical resilience, stability and many other properties of the skin. The degradation of the skin matrix plays an important role in the development of wrinkles and other signs of skin aging. The best known components of the skin matrix are structural proteins (notably collagen and elastin), which are vital to skin health and youthfulness. However, just like steal beams and rebar are necessary but insufficient for building a skyscraper, structural proteins are necessary but insufficient for a healthy skin matrix. In addition to the framework of structural proteins, the skin matrix also needs appropriate fillers, which provide mechanical cushioning, hold moisture, enhance barrier function, and so forth. The principal skin matrix fillers are glycans, a class of glucose-based polymers that includes glycosoaminoglycans and proteoglycans. As far as skin rejuvenation is concerned, the most important glycan may be hyaluronic acid (a.k.a. hyaluronan, hyaluronate or HA).

Chemistry of hyaluronic acid

Hyaluronic acid is a polymer whose unit consits of D-Glucuronic acid and N-Acetyl Glucosamine. Hyaluronic acid chains can be up to 25,000 units long or even longer; their molecular weight ranging from about 5,000 to 20,000,000 Da.

Hyaluronic acid is synthesized by the enzymes called hyaluronan synthases. Humans have at least three types of hyaluronic acid synthases: HAS1, HAS2, and HAS3. HAS1 and HAS2 synthases produce high molecular weight HA whereas HAS3 produces low molecular weight HA. Hyaluronic acid is degraded by the enzymes called hyaluronidases, of which there also appear to be several types.

Hyaluronic acid and skin physiology

Hyaluronic acid has many functions throughout the body, especially in the connective tissue. In the skin, some of its known roles are the following:

    * Holding moisture

    * Increasing viscosity and reducing permeability of extracellular fluid

    * Contributing to mechanical resilience and suppleness of the skin

    * Regulation of tissues repair

    * Regulation of movement and proliferation of cells

    * Regulation of immune and inflammatory responses

It is important to note that physiological effects of hyaluronic acid depend to a large degree on the size (molecular weight) of its chains. In particular, relatively small HA molecules (weighing less than about 20,000 Da) appear to trigger the early phases of wound healing, including activation of various types of immune cells and inflammatory responses. This is understandable. Considering that tissue injury would typically result in increased degradation of extracellular matrix (and HA in particular), it makes sense that the degradation fragments (i.e. small size HA fragments) would act as indicators of injury and trigger wound healing. On the other hand, large HA molecules appear to suppress local immune response and inflammation. By the similar logic, the predominance of large HA molecules sends a signal that the skin is intact and defense and/or repair are not required.