Extracellular vesicles and their translational therapeutic potential

Background and purpose: Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) have emerged as a promising cell-free therapy for osteoarthritis (OA). However, their transition into clinical therapeutics is constrained by unstandardized pharmacokinetics and heterogeneous preclinical reporting. Experimental approach: A meta-analysis of preclinical in vivo OA models evaluating MSC-EV therapy was conducted. Study quality was rigorously assessed using MISEV 2023 (Minimal Information for Studies of Extracellular Vesicles, 2023) criteria and the SYRCLE (Systematic Review Centre for Laboratory animal Experimentation) risk-of-bias tool. Quantitative synthesis was performed for the Osteoarthritis Research Society International (OARSI) histological score, reporting pooled mean differences (MDs) and 95 % confidence intervals (95% CIs), along with heterogeneity (I² statistic) and microRNA (miRNA) cargo analysis. Key results: MSC-EV administration conferred robust structural protection against cartilage degradation. Quantitative synthesis of human-derived MSC-EVs (26 studies) significantly reduced OARSI scores (MD -3.27, 95% CI -4.66 to -1.88; p < 0.0001). Similarly, quantitative synthesis of animal-derived MSC-EVs (8 studies) demonstrated an even more profound effect (MD -5.58, 95% CI -7.13 to -4.03; p < 0.0001). Non-parametric Trim-and-Fill analysis estimated zero missing studies in both datasets, confirming that these effect sizes are highly robust to publication bias. Despite these robust efficacy signals, significant heterogeneity (I² > 84 %) persisted. Meta-regression revealed that arbitrary dosage metrics, whether reported by particle count or protein concentration, failed to reliably predict treatment efficacy, highlighting severe gaps in dose-exposure standardization. Conclusion: MSC-EVs demonstrate highly potent, cross-species efficacy in attenuating OA progression. However, clinical translation is critically bottlenecked by a lack of ADMET (absorption, distribution, metabolism, excretion and toxicity) compliance. Future research must prioritize standardized particle-based dosing, in vivo pharmacokinetic tracking, and rigorous cargo-function validation to enable regulatory approval.