Abstract / Summary
Human skin aging comprises compartment and exposure-dependent changes in extracellular matrix, epidermal differentiation, barrier function, redox and proteostasis, inflammation, and senescence. This study used targeted, non-exhaustive PubMed searches and citation checking through 25 August 2026 to conduct a structured secondary analysis of published adult human in vivo, human ex vivo, and primary adult skin-cell proteomic evidence. Forty selected core reports represented 36 distinct evidence units; one antibody-based targeted panel study was retained as adjacent evidence. Findings were synthesized descriptively by biological domain while preserving specimen, exposure, analytical platform, comparator, and molecular level. Qualitative convergence was strongest for extracellular matrix remodeling, epidermal and barrier biology, oxidative stress and proteostasis, inflammaging, and senescence-associated programs. Protein-level agreement was constrained by small cohorts, heterogeneous sampling, variable protein-inference rules and statistical reporting, scarce external validation, and frequent commercial involvement. Most bottom-up studies resolved protein groups rather than intact proteoforms; peptide-location and cleavage-susceptibility studies demonstrated that abundance, processing, modification, and structural accessibility are not interchangeable. Direct in vivo topical-intervention evidence was sparse and formulation-specific. Current evidence supports contextual pathway interpretation and candidate prioritization, but not universal skin-age biomarkers, individualized product matching, or clinical efficacy inferred from proteomic shifts alone.