Epidermal maturation, vitamin C and hyaluronan metabolism

Summary Epidermis, the surface layer of human skin, is formed by cells called keratinocytes. They divide (making more cells) in the deeper parts of the skin and gradually move towards the surface. Keratinocytes eventually form a layer of dead cells on the skin's surface, and this layer is the main protective barrier against things that might damage or irritate the skin, such as chemicals and germs. A viscous substance called hyaluronan surrounds keratinocytes in the lower, living cell layers. All kinds of injuries to the epidermis, like wounding, infection, and sunburn, trigger a strong inflammatory response by keratinocytes. This response includes increased division of keratinocytes, and their movement to help the injury site recover, as well as increased hyaluronan production and turnover. In many skin diseases the keratinocyte injury‐response is excessive, or even completely unfounded, and harmful. Therefore, factors and treatments that calm down this reaction are potential medicines for some skin diseases. This study from Kuopio, Finland, studied hyaluronan metabolism (i.e. breakdown) in a special model developed in the laboratory, in which keratinocytes separate to produce a normal‐looking epidermis. This model allowed the researchers to demonstrate that vitamin C suppresses both production and degradation of hyaluronan in the epidermis. Since rapid hyaluronan metabolism is an indicator of inflammation, vitamin C – which is an antioxidant ‐ might have a use for suppressing this reaction in keratinocytes. This study calls for more work on the vitamin's mechanism of action, and possible roles in clinical practice.