Skin aquaporins: function in hydration, wound healing, and skin epidermis homeostasis.

Several aquaporins (AQPs) are expressed in mammalian skin. Some are directly involved in water transport, such as AQP5, which is involved in sweat secretion. In contrast, the physiological role of skin aquaglyceroporins, which permeate both water and glycerol, appears more and more complex. AQP3 is the most abundant skin aquaglyceroporin. Both water and glycerol transport by AQP3 appear to play an important role in hydration of mammalian skin epidermis. In addition, recent data suggest that glycerol transport by AQP3 is involved in the metabolism of lipids in skin as well as in the regulation of proliferation and differentiation of keratinocytes. Finally, AQP3 is also believed to be important in wound healing, as a water channel by facilitating cell migration, and as a glycerol transporter by enhancing keratinocyte proliferation and differentiation.