Abstract
Human mesenchymal stem cells (hMSCs) and their secreted extracellular vesicles (EVs) are promising therapeutics to treat degenerative or inflammatory diseases such as ischemic stroke and Alzheimer's disease (AD). hMSC-EVs have the coveted ability to contain therapeutically relevant biomaterials; however, EV biogenesis is sensitive to the culture microenvironment in vitro. Recently, the demand for hMSC-EVs has increased dramatically, highlighting the need for scalable bioreactors for large-scale biomanufacturing. In this study, adipose-derived hMSCs were seeded in 2D plates, an ultralow-attachment (ULA) plates as static aggregates, a novel vertical wheel bioreactor (VWBR) as aggregates, and a spinner flask bioreactor (SFB). EV secretion was quantified and compared using ExtraPEG-based ultracentrifugation and nanoparticle tracking analysis. Compared to the 2D group, significantly higher total EV production and cell productivity in the bioreactors were observed, as well as the upregulation of EV biogenesis genes. Furthermore, there was increased EV production in the VWBR compared to the SFB and the static ULA control. Functional assessments demonstrated that EVs, when delivered via culture medium or hydrogel-based systems, significantly attenuated oxidative stress elevation, suppressed proinflammatory cytokine secretion (e.g., TNF-α) and gene expression, and inhibited nuclear factor kappa-light-chain-enhancer of activated B-cell (NF-κB) activation and neurodegenerative markers across in vitro assays. These findings suggest EV-mediated mitigation of oxidative and inflammatory pathways, potentially through modulation of the NF-κB signaling cascade. This study shows the influence of bioreactor types and their microenvironments on EV secretion in hMSCs and their applications in hMSC-EV production and bioengineering.