Optimized Lipid Nanoparticle-Mediated mRNA Co-Delivery of SOX5/SOX9 Enables Synergistic Senescence Reversal for Osteoarthritis Therapy.

Background: Chondrocyte senescence significantly impairs extracellular matrix (ECM) synthesis and accelerates cartilage degradation, driving osteoarthritis (OA) progression. Although gene therapies targeting senescent chondrocytes are promising for OA, developing strategies that simultaneously rejuvenate cartilage function and precisely modulate the inflammatory microenvironment remains challenging. Methods: We developed an optimized lipid nanoparticle (LNP)-based delivery platform for the efficient co-delivery of transcription factors SOX5 and SOX9 mRNAs into chondrocytes. The physicochemical properties and biosafety of the formulations were systematically characterized. Additionally, the therapeutic efficacy of these formulations was evaluated in senescent chondrocyte cultures and an ACLT-induced osteoarthritis (OA) rat model. Results: The synergistic action of SOX5 and SOX9 markedly enhanced anabolic signaling, promoting synthesis of critical cartilage ECM components (type II collagen and aggrecan). The combination also reduced inflammation-mediated matrix degradation in vitro and in vivo. In a rat OA model, this optimized LNP-mediated co-delivery substantially improved cartilage regeneration, suppressed joint inflammation, and restored joint function compared to single-gene treatment or untreated controls. Conclusion: This work provides an advanced, synergistic mRNA therapeutic approach employing optimized LNPs to alleviate chondrocyte senescence and stimulate cartilage regeneration, representing a promising strategy for OA intervention.