The Role of EVs in the Aging Hematopoietic System.

Extracellular vesicles (EVs) are membrane-enclosed nanoparticles that mediate intercellular communication by transferring proteins, nucleic acids, and lipids. Within the hematopoietic system, EVs orchestrate critical signaling between bone marrow (BM) niche cells and hematopoietic stem and progenitor cells (HSPCs) to regulate quiescence, proliferation, and lineage commitment. During aging, senescence and telomere attrition drive a profound remodeling of EV biogenesis and cargo. Aged EVs, particularly those released from senescent mesenchymal stromal cells (MSCs) and osteoblasts, exhibit altered microRNA profiles and reduced protective antioxidants. These changes perpetuate niche dysfunction, induce senescence in recipient cells, and promote myeloid-biased hematopoiesis. Importantly, this communication is a selective process governed by vesicle-intrinsic surface signatures, such as tetraspanins and integrins, which interact with specific receptors on distinct hematopoietic subsets to regulate signaling fidelity. Conversely, EVs from young or pluripotent stem cells deliver rejuvenating signals that can restore aged HSPC function and attenuate inflammaging. Elucidating these mechanisms of selective targeting and stress-responsive cargo remodeling provides vital insights for developing EV-based diagnostic tools and rejuvenation strategies to prevent age-related immune imbalances and hematologic malignancies.