Age- and Sex- Driven Transcriptional and Metabolic Diversity in Myeloid-Derived Suppressor Cells After Mouse Sepsis.

Sepsis induces profound immune dysregulation, often resulting in chronic critical illness characterized by persistent immunosuppression and poor outcomes. Myeloid-derived suppressor cells (MDSCs) are central mediators of this immunosuppressive phenotype, yet the influence of age and sex on their transcriptional and metabolic states remain poorly understood. Here, we employed single-cell RNA sequencing of splenic leukocytes from young (3-4 months) and older (18-24 months) adult male and female mice subjected to a clinically relevant murine sepsis model to define age- and sex-specific MDSC phenotypes. We identified significant differences regarding age and sex in MDSC expansion, transcriptome, canonical pathway activation, RNA velocity, mitochondrial metabolism, and predicted cell-cell communication after sepsis. Using drug2cell analysis of total leukocytes we also identified cohort-specific drug target profiles. These findings underscore the importance of age and sex in shaping sepsis-induced MDSC biology and suggest that personalized immunomodulatory strategies targeting MDSCs could improve sepsis outcomes.