50 SKIN HYDRATION
groups. Orthodox aquaporins (AQP0, AQP1, AQP2, AQP4, AQP5, AQP6 and AQP8) were initially believed to transport only water; however, it is now known that some of them can also permeate small molecules under certain conditions. AQP3, AQP7, AQP9 and AQP10, known as
aquaglyceroporins, facilitate the transport of glycerol and other small solutes in addition to water. Finally, AQP11 and AQP12, often referred to as unorthodox aquaporins, display unique structural and functional features that are not yet fully understood.6
Aquaporin-3: the master of hydration 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.7 Several studies, have suggested an important
role for Aquaporin-3 (AQP3) in keratinocyte proliferation. Mechanistically, AQP3 facilitates the uptake of glycerol into keratinocytes, which can be used as a metabolic substrate contributing to ATP production and cellular growth. However, although AQP3 may promote
proliferative responses under certain conditions, its presence is also essential for normal skin physiology, including epidermal homeostasis, wound healing, and skin hydration, highlighting the context-dependent role of AQP3 in epidermal biology.6 In addition, AQP3 expression is closely
associated with the expression of other epidermal proteins involved in maintaining skin hydration, such as CD44, claudin-1, and filaggrin.8 AQP3 levels are significantly influenced by ageing and chronic sun exposure, conditions that
Figure 1: Schematic representation of aquaporin channel embedded in the lipid bilayer
may disrupt osmotic balance in the epidermis and contribute to the skin dryness frequently observed in older individuals and in photo-exposed areas.8 This effect is particularly relevant when considering the structural organization of human skin. In a thicker epidermis such as that of humans,
deletion or loss of AQP3 may disrupt water movement within the viable layers of the epidermis where this protein is normally expressed. This alteration in water transport may lead
to the accumulation of fluid between epidermal cells, resulting in intercellular edema, histologically known as spongiosis. This phenotype is likely to represent a more severe alteration than the dry skin phenotype previously described in AQP3 deletion models.9 To evaluate whether the intercellular edema
observed in patients with eczema could be associated with a defect in the localization of AQP3 in the plasma membrane, the
immunolocalization of this protein was analysed in skin biopsies obtained from three patients suffering from eczema. In the first patient, the epidermis showed
severe spongiosis and no AQP3 expression was detected. In the second patient, both apparently healthy
and damaged epidermal regions were observed within the same tissue section. In areas with normal epidermal structure, AQP3 expression remained intact, whereas in regions displaying intercellular edema the water channel was absent. In the third patient, no alterations in epidermal
structure were detected and, consistently, no changes in the expression or localization of AQP3 were observed.9 Taken together, these results indicate that
AQP3 expression remains normal in structurally intact epidermal regions but disappears in areas where spongiosis is present. Therefore, these findings suggest a possible association between the absence of AQP3 in the plasma membrane and the development of intercellular edema in some cases of eczema in human skin.9 For these reasons, considerable interest has
emerged in identifying active ingredients capable of increasing AQP3 expression in order to enhance hydration in human skin keratinocytes.
Cistanthe grandiflora and the phenomenon of the flowering desert The Atacama Desert, located in northern Chile, extends across the regions of Arica and Parinacota, Tarapacá, Antofagasta, Atacama, and Coquimbo. It is characterised by a hyper-arid climate and is considered the driest non-polar desert in the world, with areas where no significant precipitation has been recorded for decades and even centuries.1,2 Its exceptionally stable atmosphere and low
Figure 2: Schematic representation of aquaporin-mediated water regulation in plants adapted to arid environments11
PERSONAL CARE MAGAZINE May 2026
cloud cover favour intense solar radiation, making it one of the regions with the highest levels of solar irradiance on the planet. The extreme aridity, together with high soil salinity and the limited availability of organic matter, generates vast areas characterized by very low biodiversity.1,3 In this extremely arid environment, where
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