The pathogenesis of melasma is complex, and its main predisposing factors include ultraviolet irradiation, endocrine disorders and emotional changes. Long-term ultraviolet exposure can induce melanocyte proliferation. Melanin synthesis relies on a series of oxidative reactions mediated by tyrosinase, which disrupts the balance between oxidation and antioxidation in the body, manifested as increased lipid peroxide (LPO) and decreased superoxide dismutase (SOD). Therefore, the experimental animal model of melasma can be evaluated by detecting skin melanin pathological morphology, as well as the levels of malondialdehyde (MDA, a derivative of LPO) and SOD. In this study, systemic intervention with progesterone combined with local ultraviolet irradiation was performed in mice to establish an experimental melasma model.

C57BL/6 mice (female, 8 weeks old)
Modeling method: Intramuscular injection of progesterone injection was performed for 28 consecutive days. From the 29th day onward, the back hair was shaved and exposed to ultraviolet irradiation. The melasma model was successfully established after 5 days.
Evaluation index: HE staining