Development of a sustained-release PLGA–MFSC nanoparticle formulation and its long-term anti-inflammatory and chondroprotective effects in osteoarthritis

This study aimed to develop a PLGA-based nanoparticle formulation for the sustained delivery of membrane-free stem cell (MFSC) derived from human adipose-derived stem cells and to evaluate its anti-inflammatory and chondroprotective efficacy in an osteoarthritis model. Although MFSC has emerged as a promising cell-free therapeutic approach for osteoarthritis treatment, its rapid clearance and limited retention following intra-articular administration may reduce its long-term therapeutic efficacy. To overcome these limitations, MFSC was encapsulated into poly(lactic-co-glycolic acid) (PLGA) nanoparticles using a double-emulsion solvent evaporation method to establish a sustained-release delivery system. The morphological characteristics and in vitro release behavior of the formulation were analyzed. The results showed that PLGA–MFSC nanoparticles exhibited a spherical morphology in the nano–submicron size range. In a preliminary in vitro release assessment conducted at room temperature, PLGA–MFSC showed prolonged and non-linear release of the MMP-9 analytical marker over 31 days without a pronounced initial burst, with a cumulative release of 67.2%. An osteoarthritis model induced by monosodium iodoacetate (MIA) in rats was used, and the efficacy of PLGA–MFSC was evaluated via intra-articular administration. Histological analysis revealed that the PLGA–MFSC group exhibited reduced cartilage surface damage and improved chondrocyte organization compared with the control group. Furthermore, immunohistochemical analysis showed reduced expression of inflammatory mediators, including iNOS, COX-2, and IL-6. Immunofluorescence staining revealed restored ZO-1 expression in RAW264.7 macrophages alongside suppression of TLR4, IL-6, and NF-κB signaling activity. In addition, serum CRP and MMP-9 levels in the PLGA–MFSC (W2) group were reduced by 28.5% and 53.2%, respectively, compared with those in the MIA control group, indicating attenuation of osteoarthritis-associated inflammatory responses. These results suggest that PLGA–MFSC has potential as a delivery system for MFSC-associated components and exerts anti-inflammatory and chondroprotective effects in an experimental osteoarthritis model. Therefore, PLGA–MFSC may represent a promising local delivery strategy for MFSC-based osteoarthritis therapy by combining the biological activity of MFSC with the delivery properties of PLGA nanoparticles.