Abstract: XU Qing?鄄fang, HOU Wei, LIU Chen, ZHENG Yue, GONG Zi?鄄jian, LAI Wei. Department of Dermatology and Venereology, Third Affiliated Hospital, Sun Yat?鄄sen University, Guangzhou 510630, China Corresponding author: LAI Wei, Email: drlaiwei@163.com 【Abstract】 Objective To observe the expression changes of cathepsin K （CatK） in human dermal fibroblasts at different time points after different doses of ultraviolet A （UVA） irradiation. Methods Dermal fibroblasts were isolated from circumcised foreskins of children, and subjected to primary culture and subculture. Cells at third - tenth passage were used in the following experiment. Some fibroblasts were irradiated with UVA of 10 J/cm2 and collected at 24, 48 and 72 hours separately after the irradiation, and some fibroblasts were irradiated with UVA of 10, 20 and 30 J/cm2 separately and harvested 48 hours later. The fibroblasts receiving no irradiation served as the control group. Reverse transcription PCR and Western blot were carried out to detect the mRNA and protein expressions of CatK in fibroblasts, respectively. Results Compared with the control fibroblasts, those irradiated with UVA of 10 J/cm2 showed a significant elevation in the mRNA and protein expression levels of CatK on day 1 （0.351 ± 0.038 vs. 0.177 ± 0.006, 1.76 ± 0.27 vs. 0.82 ± 0.45, respectively, both P < 0.05）, day 2 （0.510 ± 0.017 vs. 0.176 ± 0.002, 2.97 ± 0.36 vs. 1.58 ± 0.15, respectively, both P < 0.05） and day 3 （0.313 ± 0.012 vs. 0.173 ± 0.002, 2.23 ± 0.14 vs. 1.29 ± 0.32, respectively, both P < 0.05）, with the highest expressions of CatK mRNA and protein observed on day 2. Within the range of 10 － 30 J/cm2, UVA enhanced the CatK mRNA and protein expression levels in a dose?鄄dependent manner. In detail, at 48 hours after the irradiation with UVA of 10, 20 and 30 J/cm2, the CatK mRNA expression level in the irradiated fibroblasts was 2.34, 2.91 and 3.18 times, and the CatK protein expression level 1.77, 2.82 and 3.64 times, respectively, that in the control fibroblasts （all P < 0.05）. Conclusion The expression of CatK is up?鄄regulated in human dermal fibroblasts after UVA irradiation. 【Key words】 Fibroblasts; Elastic tissue; Cathepsin K; Ultraviolet rays

Key words: Cathepsin K