Abstract: Objective To determine the repression effect and mechanism of metformin on photo-damage of human skin fibroblasts induced by UVA. Methods Human skin fibroblasts were randomly divided into Control group, UVA group and UVA+MF group. The proliferation of HSF was detected by CCK-8 assay kit. SA-β-gal staining was performed to evaluate the senescence state. The level of ROS was examined by fluorescence probe DCF-DA staining using flow cytometry. Real-time PCR was used to determine mRNA expression of senescence-associated signals of MMP1 and MMP3. The protein expression of MMP1, MMP3, SOD1 and SOD2 were measured by Western blot. Results To the proliferation of HSF, 0.01mmol/L Metformin had no significant effect, but 0.1 and 1mmol/L Metformin depressed significantly（P<0.05）. Compared with the Control group, it showed that UVA irradiation increased the positive rate of SA-β-gal staining（P<0.01）, the level of ROS（P<0.05）, mRNA and protein expression of MMP1 and MMP3 significantly（P<0.01）; Also decreased the expression of SOD1 and SOD2（P<0.01）. Compared with the UVA group, it showed that metformin decreased the positive rate of SA-β-gal staining（P<0.05）, the level of ROS（P<0.05）, mRNA and protein expression of MMP1 and MMP3 significantly（P<0.05）; Also increased the expression of SOD1（P<0.01）and SOD2. Conclusion: Metfomin can repress the photo-damage of human skin fibroblasts induced by UVA via the inhibiton of ROS and metal matrix protease generation, also the improvement of cellular antioxidant capacity.

Key words: Metformin, UVA, human skin fibroblasts, photo-damage