Liao, G. Y.; Pettan-Brewer, C.; Ladiges, W. C.

Aging is characterized by coordinated molecular and physiological changes across multiple biological systems, yet the ability to quantify these processes non-invasively within individuals remains limited. Here, we establish a framework for quantifying hallmark-level features of aging in mice using serum protein array profiles obtained from a single blood draw. Serum protein expression was profiled in groups of CB6F1J and C57BL/6J male mice at 8 and 32 months of age and mapped to established hallmarks of aging. Hallmark-level analyses revealed coordinated, pathway-specific changes in inflammatory, vascular, intercellular signaling, metabolic, and regenerative processes, with distinct patterns observed between strains. CB6F1J mice exhibited directional shifts across multiple pathways, while C57BL/6J mice showed broader but more heterogeneous changes. Cross-strain comparisons demonstrated shared pathway-level trends alongside variable protein-level concordance. This approach enables non-terminal assessment of aging within individuals and resolves heterogeneity in aging trajectories using minimally invasive sampling. These findings support the use of circulating protein signatures to quantify biological aging and provide a framework for translating non-invasive proteome-based assessment of aging to human studies.