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

Abstract 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). Both stressors induced significant increases in cortisol, catecholamines, and cell-free DNA (cfDNA) in all participants. sEVs, however, were elevated only after physical stress, showing a rapid rise particularly in CD9- and CD63-positive vesicles, followed by a return to baseline within 40 min. In contrast, psychosocial stress elicited highly heterogeneous, non-directional sEV responses. Recursive partitioning further revealed clearly distinct sEV patterns for psychosocial and physical stress, with the highest discriminatory power observed for CD44⁺ sEVs. These findings support the existence of stressor-specific sEV signatures that could serve as future biomarkers of individual stress experience and act as effectors of distinct signal transduction pathways in both psychosocial and physical stress.