Partial chemical reprogramming for induced cellular rejuvenation

Aging is caused in part by epigenetic dysregulation, making cellular reprogramming a promising strategy to restore youthful function. Full induction of pluripotency resets cellular age but erases somatic identity, limiting therapeutic use. Partial reprogramming offers a compromise by transiently engaging reprogramming pathways to reverse hallmarks of aging while maintaining cellular identity. Chemical reprogramming has emerged as an alternative approach, using small molecules to remodel signaling and chromatin states in a more controllable and homogeneous manner than transcription factor induction. Here we compare genetic and chemical reprogramming modalities for cellular rejuvenation and show that chemical cocktails can reproduce and, in some respects, surpass genetic partial reprogramming, reducing senescence and improving mitochondrial performance while avoiding induction of pluripotency. Chemical reprogramming led to a homogeneous early change in identity and pluripotency markers, while factor induction produced mixed subpopulations and prolonged treatment increased stress. Screening by systematic removal of cocktail components identified MLL-menin inhibition and chromatin regulators such as p300/CBP as necessary for senescence suppression. By contrast, RAR signaling was indispensable. Its removal not only elevated senescence but also diminished identity markers. These results establish chemical partial reprogramming as a promising alternative strategy for epigenetic rejuvenation. They highlight the balance between senescence reduction and lineage stability and set the stage for protocols that may translate into safer, tunable therapeutic approaches.