Glycosaminoglycans
Glycosaminoglycans — long chains of sugar molecules found in the extracellular matrix that attract and hold water, giving the dermis its cushioning and hydration. Hyaluronic acid is the best known example, and as a group they help maintain volume, lubrication, and the environment cells need to function.
Key points
- Glycosaminoglycans are large sugar-based molecules that bind water and fill space in the dermis.
- Hyaluronic acid is the most well-known glycosaminoglycan in skin.
- They contribute to hydration, cushioning, and the overall structure of the extracellular matrix.
- Many glycosaminoglycans attach to proteins to form larger molecules called proteoglycans.
- Their content in skin generally declines with age, affecting hydration and volume.
The family at a glance
| Glycosaminoglycan | Where it is found in skin | What it does |
|---|---|---|
| Hyaluronic acid | Throughout the dermis; smaller amounts between living epidermal cells | Binds water and fills space; the only member with no sulphate and no core protein |
| Chondroitin sulphate | Dermal ground substance, on proteoglycans such as versican | Resists compression and holds water in the gel between fibres |
| Dermatan sulphate | The dominant sulphated chain of the dermis | Carried mainly by decorin; helps set collagen fibril thickness |
| Heparan sulphate | Basement membrane at the dermal–epidermal junction, and cell surfaces | Binds and stores growth factors; helps anchor epidermis to dermis |
| Keratan sulphate | Minor in skin; concentrated in cornea and cartilage | Holds water in low-density tissue; adds little to dermal bulk |
| Decorin (a proteoglycan) | Along collagen fibrils in the dermis | Small core protein carrying one dermatan sulphate chain; limits fibril diameter |
What a glycosaminoglycan actually is
Every one is built the same way: a long, unbranched chain of a repeating pair of sugars, one of them an amino sugar. Most carry sulphate groups and all carry carboxyl groups, so the chain is strongly negatively charged along its length. That charge does the work — neighbouring chains repel one another and stay extended rather than folding up, and sodium ions are attracted in, drawing water behind them.
With one exception they do not float free. Each is assembled onto a core protein to form a proteoglycan — decorin, versican and perlecan are the ones usually named in skin — so the dermis holds bottle-brush molecules with sugar chains projecting from a protein spine. Hyaluronic acid is the outlier: no core protein, no sulphate, and a chain running to millions of daltons.
The ground substance the fibres sit in
Collagen and elastin are called the scaffolding of the dermis, but scaffolding alone would be a dry, brittle mesh. These molecules fill the space between the fibres as a viscous, heavily hydrated gel. It resists compression, so skin pressed with a fingertip yields and recovers; it lubricates the fibres so they slide past one another; and it is the medium through which nutrients and signals diffuse.
They also organise the scaffolding rather than merely filling it. Decorin binds along collagen fibrils and limits how thick they grow, part of why healthy dermal collagen forms fine, evenly spaced bundles. Heparan sulphate proteoglycans hold growth factors in reserve near the cells that respond to them. Remove those interactions and the matrix is not simply drier — it is less well built.
What shifts the balance
Total content generally falls from early adulthood, and the composition shifts as well as the quantity. Dermal hyaluronic acid becomes more tightly bound to surrounding tissue with age, so less is free to hold water. Fibroblasts synthesise less as they age, and ultraviolet exposure fragments existing chains; in chronically sun-exposed skin, glycosaminoglycan tends to sit on disorganised elastotic material rather than spread evenly.
Other influences are quieter but real. Oestrogen supports dermal glycosaminoglycan content, part of why dermal hydration and thickness commonly change around the menopause. Inflammation raises local hyaluronic acid production — some of the swelling in irritated skin is this — and a healing wound lays down a temporary hyaluronic-acid-rich matrix before remodelling it. The mix also differs between eyelid, cheek and back.
Frequently asked
How are glycosaminoglycans different from collagen?
Collagen is a fibrous protein that provides structural strength, while glycosaminoglycans are water-binding sugar molecules that fill the space between fibers and provide hydration and cushioning. Both are part of the extracellular matrix.
Are glycosaminoglycans used in skincare?
Yes, hyaluronic acid is the most common glycosaminoglycan in skincare, valued for its water-binding hydration. Others are less frequently featured but share similar moisture-holding properties.
Can a glycosaminoglycan in a cream reach the dermis?
These are large, strongly water-loving molecules, and the stratum corneum is built to keep exactly that kind of molecule out. Applied topically they generally stay at or near the surface, holding water in the outer layers — a real but superficial effect, not a top-up of the dermal supply.
Is ground substance the same thing as the extracellular matrix?
Not quite. The extracellular matrix is everything outside the cells, fibres included. Ground substance is the older term for its non-fibrous, gel-like part — glycosaminoglycans, proteoglycans and the water they hold — so it is a component of the matrix, not a synonym for it.
What does it mean for a glycosaminoglycan to be sulphated?
Sulphate groups are added inside the cell as the chain is assembled, increasing its negative charge. Every glycosaminoglycan in skin is sulphated except hyaluronic acid. The pattern is not random: it varies along the chain and influences which proteins bind there.
Do they have any role outside the dermis?
Yes. Heparan sulphate proteoglycans sit on cell surfaces and in the basement membrane throughout the skin, and hyaluronic acid is present between keratinocytes in the living epidermis. The same family appears in cartilage, vessel walls, the cornea and joint fluid.
Related topics
This is a foundational entry in the SYNC Skin Encyclopedia and is expanded over time. Educational information only — not medical advice.
