BMSC-derived Exosomes Attenuate Rat Osteoarthritis By Regulating Macrophage Polarization Through PINK1/Parkin Signaling Pathway

Objective Increasing evidence indicates that osteoarthritis(OA)is an inflammatory disease.Macrophages regulate inflammation and play a key role in OA.Research has shown that exosomes derived from bone marrow mesenchymal stem cells(BMSC-Exos)may modulate the transformation of M1 macrophages into M2 macrophages.However,the mechanisms remain unclear.Methods Exosomes were extracted from BMSC-conditioned medium and identified.We co-cultured RAW264.7 cells with Dil-labeled BMSC-Exos to evaluate the uptake of BMSC-Exos.The effects of BMSC-Exos on M1/M2 macrophage polarization,the production of reactive oxygen species(ROS),and mitochondrial damage in RAW264.7 cells were determined after induction of lipopolysaccharide(LPS)with or without BMSC-Exos by flow cytometry,immunofluorescent cell staining,and western blot analysis.The expression levels of AKT,PINK1,and Parkin were determined by western blot.We prepared an OA rat model by resecting the anterior cruciate ligament and medial meniscus.Hematoxylin-eosin(H&E)and safranin-O-fast green staining,immunohistochemistry,and immunofluorescence analyses were performed to assess changes in the cartilage and synovium.The levels of IL-6,IL-1β,TNF-α,and IL-10 in the serum or supernatant of cultured cells were examined by ELISA.Results BMSC-Exos could reduce M1 and promote M2 macrophage polarization.BMSC-Exos also inhibited mitochondrial membrane damage and ROS production.AKT phosphorylation was downregulated but significantly recovered after treatment with BMSC-Exos(P<0.01).PINK1/Parkin signaling was crucial in mitochondrial damage and subsequent M1 macrophage polarization.The protein expression of PINK1 and Parkin was significantly inhibited by BMSCExos(P<0.01).The animal model data revealed that BMSC-Exos alleviated cartilage damage,inhibited M1 macrophage polarization,and promoted M2 macrophage polarization in the synovium.BMSC-Exos also changed the systematic inflammatory state.Conclusion These data suggest that BMSC-Exos ameliorate OA development by regulating synovial macrophage polarization,and one of the underlying mechanisms may be through inhibiting PINK1/Parkin signaling.Therefore,BMSC-Exos are a potential useful therapeutic approach for OA.