Abstract: BACKGROUND: Studies have confirmed that up-regulation of microRNA-140 expression can partially inhibit osteoarthritis-like changes in knee cartilage tissues and cells and delay the progression of osteoarthritis, suggesting that microRNA-140 is involved in the pathogenesis of osteoarthritis.
OBJECTIVE: To further analyze the mechanism of microRNA-140 involvement in osteoarthritis by loading exosomes overexpressing microRNA-140 with sodium alginate/collagen hydrogel.
METHODS: Lentivirus was used to infect rat bone marrow mesenchymal stem cells to overexpress microRNA-140, then exosomes were isolated and exosomes overexpressing microRNA-140 were obtained. Sodium alginate/collagen hydrogels loaded with exosomes were prepared. Thirty-two SD rats were randomly divided into four groups, with 8 rats in each group. Normal control group did not receive any treatment. The osteoarthritis model was established by injecting sodium iodoacetate into the knee cavity in the osteoarthritis group, the non-transfected exosome group and the transfected exosome group. Two weeks later, PBS was injected into the knee cavity in the osteoarthritis group. Sodium alginate/collagen hydrogel carrying non-overexpressing microRNA-140 and overexpressing microRNA-140 exosomes were injected into the knee cavity of the non-transfected exosome group and transfected exosome group. At 6 weeks after modeling, the threshold of mechanical foot withdrawal response, the concentration of inflammatory factors in synovial fluid, the expression of chondrogen-related genes, the histological changes of knee cartilage and the expression of pyroptosis related proteins were detected in rats.
RESULTS AND CONCLUSION: (1) Compared with normal control group, the threshold value of mechanical stimulation foot contraction response, type II collagen, SOX9 mRNA expression levels, and Type II collagen immunofluorescence intensity were decreased in the osteoarthritis group (P < 0.05), and proinflammatory cytokine levels were increased in synovial fluid (P < 0.05). The mRNA expressions of matrix metalloproteinase 13 and a disintegrin and metalloproteinase with thrombospondin motifs-5 (ADAMTS-5) were increased (P < 0.05), and the protein expression levels of NLRP3, ASC, GSDMD p30, caspase-1 p20, interleukin-1β, and interleukin-18 were increased (P < 0.05). Immunofluorescence intensity of GSDMD and cleaved caspase-1 was increased (P < 0.05), and cartilage tissue was severely damaged. (2) Compared with osteoarthritis group, the threshold value of mechanical stimulation foot contraction response, type II collagen, SOX9 mRNA expression levels, and type II collagen immunofluorescence intensity in the non-transfected and transfected exosome groups were increased (P < 0.05); proinflammatory cytokine levels were decreased in synovial fluid (P < 0.05). The mRNA expression of matrix metalloproteinase 13 was decreased (P < 0.05), and the protein expression levels of NLRP3, ASC, GSDMD p30, caspase-1 p20, interleukin-1β, and interleukin-18 were decreased (P < 0.05). The immunofluorescence intensity of GSDMD and cleaved caspase-1 decreased (P < 0.05), and the cartilage tissue damage was reduced (P < 0.05), and the effect was stronger in the transfected exosome group. (3) These results conclude that microRNA-140 can reduce the pain response of rats with osteoarthritis by inhibiting inflammation, maintaining cartilage homeostasis, and inhibiting cartilaginous pyroptosis, thereby reducing cartilage damage and playing a therapeutic role in osteoarthritis. 

Key words: osteoarthritis, cartilage injury, exosomes;, microRNA-140, sodium alginate/collagen hydrogel, pyroptosis