Comprehensive Multi-omics and Mendelian Randomization Reveal the Key Role of Monocytes in Aging and Osteoarthritis

There is a close connection between aging and osteoarthritis (OA), but the specific mechanisms are still unclear. This study aims to explore the potential connections and molecular mechanisms between OA and aging through multi-omics and genetics methods. Integrating single-cell RNA sequencing (scRNA-seq), bulk RNA-seq data, Mendelian randomization (MR), colocalization analysis, and cell function analysis, this study explores the correlation between OA and aging. Furthermore, it investigates the potential causal relationship between key marker genes and OA. Integrating and analyzing scRNA-seq data from OA, aging, and control groups revealed a significant increase in the proportion of the classical monocyte core subgroup. Differential expression analysis yielded 77 marker genes, and further MR analysis identified four key marker genes (DUSP6, CSTA, CD300E, and GPX1) as causally related to OA, which was confirmed in an independent validation cohort. Reverse MR and Steiger filtering indicated no evidence of reverse causality. DUSP6- and CSTA-classical monocytes may interact with other cell subgroups through the MIF-(CD74 + CD44) signaling pathway. This study revealed the heterogeneity of monocyte subgroups in OA and aging patients, identifying key marker genes with a causal relationship to OA through an integrated multi-omics approach, providing potential molecular targets for the diagnosis and treatment of OA from an aging perspective.