Regulatory Role of Bone Marrow Mesenchymal Stem Cell-Derived Exosomes Loaded with miRNA-122 in the Progression of Osteoarthritis

Objective The aim was to design and construct engineered exosomes carrying miR-122 and miR-122 inhibitors, and to observe the effects of intra-articular injection on articular cartilage and the progression of osteoarthritis (OA) in rats, with the goal of providing new insights and options for cartilage repair, regeneration, and early treatment of OA. Methods Forty-eight SPF male rats aged 6-8 weeks were selected to establish an OA model in the rat knee joints. Rats were randomly divided into four groups: blank control group (n=12) received injection of physiological saline, normal exosome group (n=12) received injection of normal exosome suspension, miR-122 engineered exosome group (n=12) received injection of miR-122 engineered exosome suspension, and miR-122 inhibitors engineered exosome group (n=12) received injection of miR-122 inhibitors engineered exosome suspension. Bone marrow mesenchymal stem cells were cultured, identified, and passaged. Exosomes were extracted and identified using transmission electron microscopy, nanoparticle size analysis, and western blotting. Engineered exosomes loaded with miR-122 and miR-122 inhibitors were prepared using magnetic bead method, and identified by nanoparticle size analysis and real-time fluorescence quantitative PCR. The experiment was conducted according to the experimental design. General behavioral observation analysis, imaging evaluation, gross histological observation evaluation, histological detection, and immunohistochemical detection were performed on the four groups to compare and evaluate the progression of arthritis. Results (1) In terms of general behavioral observation, rats in the miR-122 engineered exosome group exhibited poorer performance compared to the blank control group in indicators such as pain, gait, joint mobility, and swelling; the miR-122 inhibitors engineered exosome group outperformed both the blank control group and normal exosome group in all indicators, with the most significant difference observed at 12 weeks. (2) Micro-CT imaging results showed that the progression of arthritis was most rapid in the miR-122 engineered exosome group, followed by the blank control group, while the normal exosome group exhibited mild arthritis, and no obvious signs of arthritis were observed in the miR-122 inhibitors engineered exosome group. Gross scoring evaluation revealed that the progression of arthritis was slowest in the miR-122 inhibitors engineered exosome group, while it was most rapid in the miR-122 engineered exosome group. (3) Histological staining results showed that at week 4, the articular surfaces of the blank control group, miR-122 engineered exosome group, and normal exosome group exhibited mild damage and thinning of cartilage; the normal exosome group and miR-122 inhibitors engineered exosome group showed relatively thicker cartilage layers. At week 8, the articular surfaces of the blank control group and miR-122 engineered exosome group were uneven, with decreased and disorganized chondrocytes, while those of the normal exosome group and miR-122 inhibitors engineered exosome group were relatively smooth, with more chondrocytes observed in the miR-122 inhibitors engineered exosome group. At week 12, a significant reduction in chondrocytes was observed in the blank control group, almost no chondrocytes were present in the miR-122 engineered exosome group, and severe cartilage damage was observed; the articular surfaces were relatively smooth in the normal exosome group, with thickening of the cartilage layer, while the miR-122 inhibitors engineered exosome group showed the best performance. (4) Immunohistochemical detection of type II collagen and proteoglycan revealed that the extracellular matrix of chondrocytes in the miR-122 inhibitors engineered exosome group and normal exosome group was better than that in the blank control group, with the miR-122 inhibitors engineered exosome group showing superiority over the normal exosome group, while the extracellular matrix of the miR-122 engineered exosome group was inferior to that of the blank control group. Conclusion MiR-122 engineered exosomes disrupt the stability of the extracellular matrix, accelerating the progression of OA, while miR-122 inhibitors engineered exosomes delay this process, maintaining the stability of the extracellular matrix and protecting articular cartilage. This may provide new insights and options for the treatment of early OA and the repair and regeneration of cartilage.