Quercetin-loaded exosomes derived from human umbilical cord mesenchymal stem cells alleviate microglia-mediated neuroinflammation via an anti-inflammatory mechanism

Neuroinflammation is central to the progression of neurodegenerative diseases (NDs), with microglia contributing through the release of pro-inflammatory and oxidative mediators. Although quercetin (Que) possesses potent anti-inflammatory and antioxidant properties, its clinical application is limited by poor solubility and bioavailability. Umbilical cord mesenchymal stem cells (UC-MSCs)-derived exosomes (Exo) offer a promising delivery system to enhance Que efficacy. This study investigated the anti-inflammatory effects of Que-loaded Exo (Que-Exo) using an in vitro neuroinflammation model. Exo were isolated from UC-MSC-conditioned media via ultracentrifugation and loaded with Que through sonication. Characterization of Exo and Que-Exo was performed using dynamic light scattering, zeta potential analysis, transmission electron microscopy, and western blotting. In vitro release and cellular uptake studies assessed Que-Exo release profiles and their internalization by HMC3 microglial cells. Neuroinflammation was induced in HMC3 cells using lipopolysaccharide (LPS). The effects of Que-Exo on pro-inflammatory cytokine and enzyme expression, nitric oxide (NO) production, and inflammatory signaling pathways were evaluated using flow cytometry, the Griess assay, and western blotting. In vitro release from Que-Exo demonstrated improved stability and controlled delivery, while fluorescence imaging confirmed efficient uptake of Que-Exo by HMC3 cells. Mechanistically, Que-Exo inhibited NF-κB nuclear translocation, a key regulator of pro-inflammatory mediator transcription. Que-Exo pretreatment significantly reduced TNF-α, IL-6, iNOS, and COX-2 expression and suppressed NO synthesis in LPS-stimulated cells. Overall, Que-Exo exhibited superior anti-inflammatory activity compared to Exo and free Que, highlighting the synergistic effect of exosomal delivery in enhancing Que bioavailability and therapeutic efficacy against neuroinflammation.