Collagen, Elastin, and Glycosaminoglycans

The dermis layer of skin has three crucial components: collagen, elastin, and glycosaminoglycans (GAG’s).

They form the bulk of an important support system called the Extracellular Matrix (ECM).

This matrix consists of structural proteins (collagen and elastin), glycosaminoglycans, and proteoglycans.

Collagen

Collagen is a structural protein, the most abundant protein in the body (about 75% of skin’s dry weight and one-third of body weight). It is found in connective tissues, such as skin, tendons, ligaments, cartilage, bones, teeth, heart valves, and the cornea.

Structurally, collagen is composed of long fibers of protein. So far, more than 29 types of collagen, have been identified (and the number continues to grow, so when you read this the number may be higher). The majority of collagen (80-90%) in the body is  Type I, Type III, and Type V. Type I is the most abundant.

Collagen is tough and does not stretch easily. It provides strength to the skin and holds the skin together.

Collagen requires Vitamin C and iron to form healthy protein fibers. In the absence of Vitamin C, collagen forms abnormal fibers. This results in skin lesions, fragile skin, and blood vessels.

Because it is a large protein, collagen does not penetrate skin. Therefore, it cannot be topically added to skin to boost collagen levels. It can only be synthesized internally. Ingredients, such as Vitamin C, boost collagen synthesis by accelerating the reaction. (Vitamin C is an essential coenzyme in collagen synthesis.)

You may see ‘hydrolyzed collagen’ on an ingredient list. Collagen in its hydrolyzed form (broken into small pieces) is used to increase skin hydration. It cannot increase the amount of collagen in skin.

Collagen is produced and recycled throughout life. But with age, the rate of collagen production slows down. After about age 40, the decline accelerates due to an increase in enzymes that degrade collagen (MMP enzymes) and a decline in the inhibitory enzymes that stop these MMP enzymes (TIMP’s).

Wrinkles and sagging are partly due to damaged collagen, and a slower rate of collagen production relative to the rate of old collagen being broken down.

Elastin

Elastin is a protein, and there is very little of it (about 1-2% of the dry weight of skin). Like collagen, elastin is a fibrous protein. But it is chemically very different from collagen. While collagen is tough, elastin is highly stretchy and resilient, providing elasticity to the skin.

Elastin gives the snap or bounce-back reaction when skin is stretched, pinched, or pulled.

Aging elastin is a major contributor to sagging and wrinkling.

Glycosaminoglycans (GAG’s)

Glycosaminoglycans (GAG’s) are polysaccharides, also called amino sugars (a sugar linked with a protein). Together with water, they create a fluid that fills the space between the collagen and elastin fibers in the dermis, giving it turgidity. This gel-like fluid is called the ground substance.

There are various glycosaminoglycans in the dermis. The most common ones are: hyaluronic acid, chondroitin sulfate, keratin sulfate, dermatan sulfate, heparin sulfate, and heparin.

The key thing to know about glycosaminoglycans is that they are water-binding substances. The GAG’s in the ground substance of the dermis attract water (brought to the dermis by blood vessels). Water in the dermis also diffuses to the lower layers of the epidermis, and eventually migrates upward through the epidermal layers.

In skin care products, water-binding ingredients are called humectants. They help keep skin moist by attracting water from the atmosphere and the lower layers of the epidermis. This counteracts the loss of water that the epidermis continually experiences when water is evaporated into air. This is called Transepidermal Water Loss (TEWL) and amounts to several ounces a day. Skin also loses water through sweating (from the sweat pores). Without constant re-hydration, skin dehydrates and wrinkles more easily.

• Hyaluronic Acid is a glycosaminoglycan that exists naturally in the dermis layer of skin. It can hold 1,000 times its molecular weight in water, which is why hyaluronic acid is such a popular hydrating and saturating ingredient in skincare.

• It is used in many moisturizers, serums, and toners to increase hydration. (Note: On ingredient labels, Hyaluronic Acid is listed as Sodium Hyaluronate, not Hyaluronic Acid, due to a naming convention.) The amount of water in the dermis is directly correlated with the amount of Hyaluronic Acid in the tissue.

• Other popular humectants include: Sodium PCA (attracts 250 times its weight), glycerin, propylene glycol, butylene glycol, lactic acid, and urea.

With age, the amount of Hyaluronic Acid in the dermis declines (steeply after 40 and most significantly in our fifth decade).