Multi‐Omics Analysis Reveals Photodynamic Therapy Ameliorating Skin Photoaging by Improving Cellular Senescence Through Mitohormesis‐Mediated Reduction of Citrate Content

ABSTRACT Clinical evidence supports the anti‐photoaging efficacy of 5‐aminolevulinic acid photodynamic therapy (ALA‐PDT), yet its mechanism remains elusive. Paradoxically, ALA‐PDT generates reactive oxygen species (ROS), a key mediator of ultraviolet radiation (UVR)‐induced photoaging, raising questions about its rejuvenating effects. Here, we employed a multi‐omics approach to clarify this paradox. A UVR‐induced hairless mouse model of photoaging was treated with ALA‐PDT, followed by transcriptomic, proteomic, and metabolomic profiling of skin biopsies. In vitro, fibroblast senescence was induced by UV irradiation to evaluate ALA‐PDT's protective effects. Mitochondrial function and citrate (CA) levels were assessed pre‐ and post‐treatment. ALA‐PDT significantly ameliorated photoaging phenotypes in mice, with multi‐omics data revealing sustained improvements in epidermal structure, extracellular matrix integrity, and immune responses. Key mechanistic findings included ALA‐PDT‐induced mitohormesis and tricarboxylic acid cycle reprogramming, notably reduced intracellular CA. In vitro, low‐dose ALA‐PDT downregulated senescence markers and CA content in UV‐stressed fibroblasts, concomitant with upregulated mitohormesis markers. These effects were abrogated by inhibiting mitochondrial ROS, suggesting ROS‐dependent mitohormetic signaling. Collectively, our data demonstrate that low‐dose ALA‐PDT alleviates photoaging by mitigating cellular senescence via mitohormesis‐mediated CA reduction, offering a novel metabolic intervention strategy for age‐related skin disorders.