Macrophages (Mφs) play a crucial role in the pathological progression of osteoarthritis (OA) by regulating inflammation and tissue repair. Decreasing pro-inflammatory M1-Mφs and increasing anti-inflammatory M2-Mφs can alleviate OA-related inflammation and promote cartilage repair. Apoptosis is a natural process associated with tissue repair. A large number of apoptotic bodies (ABs)

a type of extracellular vesicle

are produced during apoptosis

and this is associated with a reduction in inflammation. However

the functions of apoptotic bodies remain largely unknown. In this study

we investigated the role of M2-Mφs-derived apoptotic bodies (M2-ABs) in regulating the M1/M2 balance of macrophages in a mouse model of OA. Our data show that M2-ABs can be targeted for uptake by M1-Mφs

and this reprograms M1-to-M2 phenotypes within 24 h. The M2-ABs significantly ameliorated the severity of OA

alleviated the M1-mediated pro-inflammatory environment

and inhibited chondrocyte apoptosis in mice. RNA-seq revealed that M2-ABs were enriched with miR-21–5p

a microRNA that is negatively correlated with articular cartilage degeneration. Inhibiting the function of miR-21–5p in M1-Mφs significantly reduced M2-ABs-guided M1-to-M2 reprogramming following

in vitro

cell transfection. Together

these results suggest that M2-derived apoptotic bodies can prevent articular cartilage damage and improve gait abnormalities in OA mice by reversing the inflammatory response caused by M1 macrophages. The mechanism underlying these findings may be related to miR-21-5p-regulated inhibition of inflammatory factors. The application of M2-ABs may represent a novel cell therapy

and could provide a valuable strategy for the treatment of OA and/or chronic inflammation.