Abstract:

Liu Chen*, Lai Wei, Xu Qingfang, Hou Wei, Zheng Yue, Wu Lin, Wang Yujian. *Department of Dermatology and Venereology, Third Affiliated Hospital, Sun Yat-sen University, Guangzhou 510630, China Corresponding author: Lai Wei, Email: drlaiwei@163.com 【Abstract】 Objective To investigate the effects of repetitive ultraviolet A （UVA） radiation on the endocytosis and intracellular degradation of extracellular elastin by human dermal fibroblasts （HDFs）, and to explore the mechanism responsible for elastin accumulation in photoaging skin. Methods Cultured HDFs were divided into two groups: repetitive UVA radiation group treated with UVA radiation （9.9 J/cm2） once a day for seven consecutive days to establish a chronic photodamage model, and blank control group receiving no treatment. For the verification of the model, flow cytometry was performed to detect cell cycle, and senescence-associated β-galactosidase staining to determine the degree of cell senescence. Fluorescent tracer technique and conjugated polymer-based fluorescence quenching technique were conducted to observe the endocytosis and intracellular degradation of extracellular elastin in culture media by HDFs in these groups. Results Compared with the blank control group, the repetitive UVA radiation group showed increased proportions of G1-phase cells and senescent cells, which confirmed the successful establishment of chronic photodamage model in the repetitive UVA radiation group. After coculture with elastin for 24, 48 and 72 hours, the endocytosis rate of elastin was 10.0% ± 1.4%, 27.8% ± 4.2% and 39.9% ± 4.1% respectively in the blank control group, 9.9% ± 1.6%, 28.3% ± 5.1% and 42.0% ± 5.7% respectively in the repetitive UVA radiation group, with no significant difference between the two groups at the three time points （all P > 0.05）. The percentage of cells showing intracellular degradation of extracellular elastin was significantly lower in the repetitive UVA radiation group than in the blank control group （4.2% ± 1.1% vs. 7.7% ± 0.9% at 24 hours, 16.5% ± 2.4% vs. 22.8% ± 1.8% at 48 hours, 26.7% ± 2.6% vs. 33.9% ± 3.1% at 72 hours, all P < 0.05）. Conclusions UVA radiation at 9.9 J/cm2 for 7 consecutive days can decrease the intracellular degradation of extracellular elastin by HDFs, but has no obvious effect on endocytosis of elastin.