Extracellular Vesicles in Osteosarcoma: Mechanisms, Diagnostics and Therapeutic Applications.

Osteosarcoma is a primary bone malignancy of adolescents and young adults with marked heterogeneity and a high metastatic propensity. Five-year survival exceeds 70% in localized disease but falls to about 20% with pulmonary metastasis or chemoresistance, and overall outcomes have plateaued for decades. Extracellular vesicles (EVs) have emerged as critical mediators of osteosarcoma progression and metastasis. EVs remodel the tumor microenvironment (TME) by promoting immune evasion, extracellular matrix reprogramming, and angiogenesis, while also facilitating invasion, epithelial-mesenchymal transition (EMT)-like plasticity, and formation of lung pre-metastatic niches through organotropic integrins and glycoproteins. Their cargo, including proteins, lipids, and nucleic acids, drives intercellular communication that sustains proliferation, migration, and therapy resistance under metabolic or hypoxic stress. Clinically, the stability of EVs in body fluids and their tumor-specific molecular signatures highlight their promise as liquid-biopsy biomarkers for early diagnosis, prognosis, and treatment monitoring. Therapeutically, EVs are being engineered as delivery vehicles for drugs or RNA therapeutics, and interventions targeting their biogenesis, cargo sorting, or uptake are under exploration. Future research should integrate single-EV multi-omics, longitudinal cohort validation, and causal perturbation models to delineate functional mechanisms. Rational strategies that modulate EV dynamics and incorporate standardized analytic pipelines may transform EVs into actionable biomarkers and therapeutic targets, offering new avenues to overcome resistance and improve clinical outcomes in osteosarcoma.