Diclofenac sodium-loaded mesenchymal stem cells-derived exosomes for rheumatoid arthritis therapy in mice

  Background  Controlling inflammation is considered as a main clinic intervention in rheumatoid arthritis (RA). However, some patients show low responsiveness to conventional treatments, so it is urgent to explore some new therapies to meet the treatment needs.

  Objective  To explore the therapeutic effect of diclofenac sodium (DS)-loaded mesenchymal stem cells (MSCs) derived exosomes (EXs) in RA.

  Methods  MSCs were obtained from bone marrow of mice and cultured in vitro. EXs were obtained from supernatant by ultracentrifugation. Then, the nanodrug DS@EXs were constructed by loading DS into EXs by ultrasound. Morphological structure of EXs and DS@EXs were observed by transmission electron microscopy (TEM), the particle sizes and zeta potentials of EXs and DS@EXs were detected by nanoparticle tracking analysis. The markers (CD9 and CD63) of EXs and DS@EXs were verified by western blotting. The ability of targeted delivery of DS@EXs in inflamed joints in vivo were analyzed by frozen section of joint and immunofluorescence. The anti-inflammatory effect of DS@EXs was evaluated by arthritis score and the levels of inflammatory cytokines (interleukin-6, IL-6; interleukin-1β, IL-1β; tumor necrosis factor, TNF). The protective effect on joint was analyzed by micro-computed tomography (micro-CT).

  Results  TEM revealed cup-like morphologies for EXs and DS@EXs. Diameter and zeta potential of DS@EXs was 100 nm and -12 mV, which were similar to EXs. In addition, the markers (CD9 and CD63) were both expressed on EXs and DS@EXs. Compared to ordinary drug delivery carrier (such as liposomes), confocal laser scanning microscope imaging showed more DS@EXs (labeled with DIO) accumulated in the inflamed joints (P<0.05). The arthritis score of the DS@EXs group was significantly lower than that of the PBS group (P<0.05). Compared to the PBS group, the levels of IL-6, IL-1, and TNF in serum of mice from the DS@EXs group decreased by 52.8%, 63.8% and 52.5%, respectively (P<0.05). Compared to the PBS group, DS@EXs ameliorated bone erosion on the surface of joint, and the value of bone mineral density increased from 921 mg/cm³ to 1195 mg/cm³ (P<0.05).

  Conclusion  DS@EXs can attenuate inflammatory response and alleviate bone erosion.