Refining the biomanufacturing of microalgae-derived extracellular vesicles as a potential nanotherapeutic for osteoarthritis

Abstract Osteoarthritis (OA) is a degenerative joint disease marked by oxidative stress, chronic inflammation, and cartilage degradation. Current treatments are limited and fail to address the underlying disease mechanisms. Extracellular vesicles (EVs) have emerged as promising nanotherapeutics; however, mammalian-derived EVs face cost and scalability challenges. Microalgae represent a sustainable alternative, yet their potential as EV biofactories for regenerative medicine remains unknown. This study aims to refine the bio-manufacturing of microalgae EVs as a next-generation nanotherapeutic for OA. Microalgae species ( Chlorella sorokiniana, Synechococcus sp. , Leptolyngbya sp. , Chlamydomonas reinhardtii CC1690 ) were screened under varying photoperiods (0h, 16h, 24h light/day) to assess the influence on viability, growth and EV production. EVs were characterized by transmission electron microscopy, nanoparticle tracking analysis, protein quantification and immunoblotting. Their antioxidant capacity, cellular recruitment, and therapeutic efficacy were evaluated in a cytokine-induced OA-like in vitro model. Our findings demonstrated that microalgae growth and EV yield were highly light-dependent, with all species maintaining high viability (>80%) across different photoperiods. Notably, Leptolyngbya sp. ( Leptolyngbya ) exhibited the fastest growth and highest EV yield under extended illumination, producing EVs with strong antioxidant activity. Leptolyngbya- derived EVs (Lepto-EVs) enhanced the proliferation and migration of human bone marrow-derived mesenchymal stromal cells and provided protection against matrix degradation within a cytokine-induced OA-like model. These findings position microalgae, particularly Leptolyngbya , as a highly scalable and sustainable producer of therapeutic EVs. Lepto-EVs offer a potent, cell-free nanotherapeutic exhibiting anti-catabolic properties alleviating cytokine-induced matrix degradation in an OA-like milieu, establishing microalgae EVs as a promising, cost-effective frontier in regenerative nanomedicine. Graphical abstract