Stress type–specific small extracellular vesicle signatures reflect divergent biological responses to acute psychosocial and physical challenges

Maladaptive stress responses are associated with a variety of psychological and physical disorders, often characterized by molecular indicators of dysregulated stress pathways. Small extracellular vesicles (sEVs), which play a key role in intercellular communication, may be critically involved in these processes. In this study, we quantified sEV concentrations (specifically CD9 ⁺ , CD63 ⁺ , and CD81 ⁺ markers) in the plasma of twenty young, healthy men before and after exposure to both acute psychosocial and physical stress, using imaging flow cytometry (IFCM).All participants showed significant increases in cortisol, catecholamines, and circulating cell-free DNA (cfDNA) following both stressors. In contrast, sEVs were significantly elevated only in response to physical stress. Physical stress induced a rapid increase in sEV release, particularly in CD9- and CD63-positive vesicles, followed by a return to baseline within 40 minutes. Psychosocial stress, however, triggered more variable sEV responses across individuals.Importantly, our classification approach using recursive partitioning revealed distinct sEV patterns associated with psychosocial and physical stress, with highest discriminatory value for CD44⁺ sEVs. These findings indicate that psychosocial and physical stress elicit distinct sEV signatures, which may reflect differential stress communication pathways and highlight their potential as biomarkers for stress-related processes and as possible targets for the effects of psychosocial exposures, including early adversity and trauma.