Is Aquaporin-3 a Determinant Factor of Intrinsic and Extrinsic Aging? An Immunohistochemical and Morphometric Study

Aquaporin-3 (AQP3) is an aquaglyceroporin that plays a role in skin hydration, cell proliferation, and migration. The aim of this work was to investigate the expression of AQP3 in sun-exposed and sun-protected human skin from different age groups to understand the relationship between AQP3 and skin aging. Using standard immunohistochemical techniques, sun-exposed and sun-protected skin biopsies were taken from 60 normal individuals. AQP3 was expressed in the basal and the suprabasal layers, sparing the stratum corneum, in all specimens. Dermal expression was detected in fibroblasts, endothelial cells, and adnexa. Sun-protected skin showed a significantly higher epidermal H-score and percentage of expression (P=0.002 and <0.001, respectively) compared with sun-exposed skin. The AQP3 expression intensity showed a gradual decrease from the 20 to 35-year-old group to the 35 to 50-year-old group, with the least immunoreactivity in the above 50-year-old group. A significant difference was detected in the H-score in favor of the 20 to 35-year-old group in sun-exposed and sun-protected skin (P<0.001 for both). A significant negative correlation was noted between the AQP3 expression percentage and the age in sun-exposed (r=-0.64, P<0.001) and sun-protected skin (r=-0.53, P<0.001). In conclusion, the skin dryness observed in intrinsic and extrinsic aged skin may be explained, at least in part, by AQP3 downregulation. This may open new avenues sufficient to control skin texture and beauty. Its interaction in skin protein organization and gene polymorphism can also be tackled in future research. In addition, clinical trials using AQP3 topical applications should be carried out to evaluate its effectiveness in the reversal of age-related skin changes.