The Experimental Study:Topical Metformin In The Treatment Of Melasmaguinea Pig Model

Objective:To evaluate the safety and efficacy of topical metformin with different concentrations in the treatment of melasma Guinea pig model,and to provide relevant experimental evidence for clinical treatment of melasma and other pigmented dermatitis.Methods:In this study,we use ultraviolet modeling to establishmelasma Guinea pig model.The Guinea pig in the model group are randomly divided into 6 groups,namely the blank control group(Control),the 2%Hydroquinone group(2%HQ),the 7.5%metformingroup(7.5%Met),the 15%metformin group(15%Met),the 30%metformin group(30%Met)andthe 60%metformin group(60%Met),the course of treatment in each group is 6 weeks.Outcome measures included general observation,Masson-Fontana staining and immunohistochemistry to detect the number of melanocytes and the activity of melanin.Results:After 6 weeks of treatment,there was no obvious difference in the visual changes between the groups.The pigmentation of the blank control group,7.5%Met group,and 15%Met group was slightly reduced,but still significantly higher than normal skin.The pigmentation of HQ group,30%Met group,and 60%Met group was significantly reduced,but some guinea pigs had adverse reactions such as erythema and desquamation during the treatment.The Masson-Fontana staining results show thatcompared with the blank control group,the melanin granules in the HQ group and 30%Met group were significantly reduced(P<0.001),the melanin granules in the 60%Met group were reduced(P<0.05).Among them,there was no significant difference in the percentage of positive target area occupies the epidermal area of HQ group,30%Met group,and 60%Met group(P>0.05),the melanin granules in the 30%Met group were significantly lower than 7.5%Met group and 15%Met group(P<0.05).The immunohistochemical results show that compared with the blank control group,the number of melanocytes and the mean optical density(MOD)of melanin granules in the HQ group,30%Met group,and 60%Met group were significantly decreased(P<0.001).Among them,there was no significant difference in the number of melanocytes and the MOD of melanin granules of HQ group,30%Met group,and 60%Met group(P>0.05),the number of melanocytes and the MOD of melanin granules in the 30%Met group and 60%Met group were significantly lower than 7.5%Met group and 15%Met group(P<0.001).Conclusion:The optimal concentration of metformin lotion in the treatment of melasma guinea pig model is 30%,and almost as effective modality as 2%hydroquinone cream.The mechanism of topical metformin lotion treatment in melasma guinea pig model may be related to the reduction of melanin synthesis in the skin.