| Aging means that organs' adaptability decreases accompanied with years of age, and human is liable to diseases or death. Aging is regulated by presumptive genes, as well as exterior and interior's abrasions and consume, which are both shown in cell and molecular level. Skin is located in body surface, skin aging comprise natural aging and photoaging. Mechanism of natural aging is not clear, the representative theory include gene regulation theory,free radical theory,metabolic disorder theory. Gene regulation is fundamental of skin natural aging.One of feature of the clinical manifestation of skin natural aging is xerosis cutis,desquamating,fragility increasing, and recovery hypofunction; the histological manifestation include skin thinning,epidermal renewal stepping down,stratum corneum's barrier and hydration function descending. The normal water content of stratum corneum retained between 10%-20%, which make skin soft; but in old man, the water content of skin is 75% compared normal content, which cause xerosis cutis. Meanwhile,water content of skin cells decrease, which cause tiny shrinkage and enzymatic active decrease. Thus, skin aging is concerned with water content,stratum corneum's barrier and hydration function.AQP is a kind of membrane integral protein which can fast transport water. AQP has 13 hypotype in mammalian, which are distributed in different tissue and cell. According to the different function of AQPs, AQPs are divided into two subfamily: aquaporins and aquaglyceroporins. The former transport only water; aquaglyceroporins transport not only water but also glycerol. AQP3 is a aquaglyceroporin which is located in skin. AQP3 participate in several patho-physiological functions including urine concentration,water balance of air tube surface,intestinal tract's water absorption. In dermal patho-physiological course, AQP3 can transport water and glycerol to epiderm, so AQP3 is significant to epidermal barrier and water retention. Researchers found AQP3-/- mouse display xerosis cutis,stratum corneum's barrier function descending,skin elasticity descending,skin barrier repairing delayed,and biosynthesis damage,wound healing delay. All of these hint that AQP3 participate skin aging.In order to identify the relationship between AQP3 and skin aging, we detect the expression of AQP3 mRNA and protein of different ages by RT-PCR and Western blot. The result display: 1 .AQP3 mRNA in teenage group: 0.654±0.104, in middle-age group: 0.685±0.143,in old- age: 0.316±0.109. 2.The expression of AQP3 protein in in teenage group: 1.936 +0.250, in middle-age group: 1.813±0.224,in old- age: 1.044 + 0.271. We found AQP3 mRNA and protein in old-age group significantly lower than the level of middle-age group (P<0.01), and teenage group(P＜0.01)In the second part, normal human epidermal keratinocytes and skin fibroblast of different ages were cultured; the expression of AQP3 was investigated in keratinocytes and fibroblast respectively. The result display: 1 .in keratinocytes, AQP3 mRNA in teenage group: 1.240±0.205, in middle-age group: 0.889±0.136,in old- age: 0.392±0.083. The expression of AQP3 protein in in teenage group: 1.303±0.231, in middle-age group: 0.980±0.164,in old- age: 0.360 + 0.142. AQP3mRNA and protein in old-age group keratinocytes decreased with the increase of age. 2. In fibroblast, AQP3 mRNA in teenage group: 0.881±0.118, in middle-age group: 0.757±0.167,in old- age: 0.285±0.143. The expression of AQP3 protein by WB in teenage group: 0.792±0.092, in middle-age group: 0.692±0.155,in old- age: 0.375 + 0.112. AQP3 mRNA and protein in old-age group fibroblast decreased significantly (P<0.01). 3. AQP3 mRNA and protein in keratinocytes of teenage group is signify-cantly higher than fibroblasts of teenage group(P＜0.01). AQP3 protein in keratinocytes of middle-age group is significantly higher than fibroblasts of middle-age group(P<0.05). AQP3 mRNA and protein of old-age group in keratinocytes and fibroblasts is not significantly different.ALL findings suggest the expression level of AQP3 in the human skin is associated with age, and decreases as the age grow. AQP3 may play a important role in aging of human skin.
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