Efficacy of Intense Pulsed Light AOPT-LTL Technique in the Treatment of Melasma: An In Vivo and Clinical Study.

PURPOSE: To evaluate the efficacy and underlying mechanism of advanced optimal pulse technology intense pulsed light (AOPT) in low-energy triple-pulse long-width mode (AOPT-LTL) for melasma treatment. METHODS: An in vivo guinea pig model of melasma was established through progesterone injection and ultraviolet B radiation. Three sessions of AOPT-LTL treatment were performed weekly. The mRNA levels of key melanogenic enzymes, inflammatory factors, pro-angiogenic cytokines, and collagenolytic proteases were detected by qRT-PCR. Protein levels of stem cell factor (SCF) and mast cell growth factor receptor (c-KIT) were detected by immunofluorescence staining and Western blotting. Twenty melasma patients were treated with three sessions of AOPT-LTL treatment monthly, evaluated by the Modified Melasma Area and Severity Index (mMASI) and Erythema Index (EI). RESULTS: In guinea pigs with melasma, AOPT-LTL treatment effectively mitigated pigmentation and suppressed the expression of key genes involved in melanin production. There was a reduction in mast cell infiltration, decreased expression of inflammatory factors and pro-angiogenic factors, inhibition of angiogenesis, and alleviation of skin photoaging. Furthermore, AOPT-LTL also diminished the expression level of the SCF/c-KIT ligand/receptor pathway, which is closely associated with mast cell proliferation and activation. Consistently, three sessions of AOPT-LTL treatment effectively reduced skin melanin content, erythema severity, as well as the mMASI and EI scores in melasma patients. CONCLUSIONS: AOPT-LTL treatment significantly enhances the improvement of melasma by diminishing melanogenesis, inflammation, angiogenesis, mast cell infiltration, and collagen degeneration, potentially through the inhibition of the SCF/c-KIT ligand/receptor pathway.