Vitamin C attenuates primate bone marrow aging at the molecular and progenitor level.

Bone marrow aging compromises hematopoiesis and immunity, yet whether these processes are modifiable in primates remains unexplored. Here, we map the single-cell transcriptomic landscape of primate bone marrow aging and demonstrate that long-term oral vitamin C (VC) supplementation attenuates selected molecular and progenitor-level decline. Aging drives severe common lymphoid progenitor (CLP) depletion, myeloid-biased hematopoietic stem and progenitor cell (HSPC) output, and anatomical site-specific molecular adaptations. VC administration partially offsets these phenotypes, expanding the CLP pool and rebalancing lineage commitment trajectories. This aligns with a ∼4-year reduction in transcriptomic age estimates, cross-validated by an epigenetic clock. Cell-cell communication analyses revealed that VC remodels intercellular signaling, nominating a VC-responsive, progranulin (GRN)-linked candidate pathway. In parallel, human in vitro assays demonstrate that recombinant progranulin mirrors selected VC-associated molecular actions. Collectively, these findings delineate the molecular architecture of primate bone marrow aging and nominate modifiable pathways for further investigation.