A study into how the skin retains its moisture levels

Skin is a major physical barrier against water loss from within the body to the outside dry environment. A number of water‐controlling structures are present in the skin, including the stratum corneum (the outer layer of the epidermis, which is the top layer of the skin) and the tight junctions (TJs). These are gasket‐like seals composed of proteins that block the gaps between cells, therefore controlling water loss from outside of cells. The skin cells themselves contain water, which they can also lose. When this happens they can shrink. This is dangerous for the cells because if they shrink too much, they can die. One method to counteract cell shrinkage is the accumulation by cells of ‘organic osmolytes’. These molecules are transported in and out of cells via special transporters in response to changes in the water content of the cells. We hypothesized that osmolytes may also control TJs in skin as part of a fully integrated water conservation system. This study from the UK examined how human skin cells behave in the presence of organic osmolytes. We used these samples to look at what happens to the TJs and also proteins that transport osmolytes. We also used keratinocytes (epidermal skin cells) to assess the level of ‘tightness’ of the seal made by TJs. We have provided exciting new evidence showing that the presence of organic osmolytes within keratinocytes induces the cells to make more osmolyte transporters to enhance their transport, and also specific TJ proteins. The TJ seal is also made stronger by organic osmolytes. We speculate that organic osmolytes may contribute to the barrier function of the skin through a direct effect on TJ structures. Linked Article :  El‐Chami et al. Br J Dermatol 2021; 184 :482–494.