MiR-9 facilitates cartilage regeneration of osteoarthritis in rabbits through regulating Notch signaling pathway

H.-T. Yu, C.-Z. Gu, J.-Q. Chen

Department of Orthopedics, Baoding No. 1 Central Hospital, Baoding, China. rde303a@163.com

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• Orthopedics

OBJECTIVE: To explore the effect of micro ribonucleic acid (miR-9) on cartilage regeneration of osteoarthritis in rabbits through the regulation of the Notch signaling pathway.

MATERIALS AND METHODS: A total of 30 specific pathogen-free Sprague-Dawley rabbits were randomly divided into control group (healthy rabbits, n=10), model group (osteoarthritis model, n=10) and miR-9 group (osteoarthritis model + miR-9 interference, n=10). The degeneration degree of rabbit knee articular cartilage in three groups was assessed through the Mankin’s score. The morphology of cartilage tissues was observed under an optical microscope. Expressions of the Notch1, B-cell lymphoma-2 (Bcl-2), Bcl-2 associated X protein (Bax) proteins, and collagen II (CII) in chondrocytes were detected via the immunohistochemical assay.

RESULTS: In rabbits of control group, the articular cartilage had a smooth surface and complete structure, and the cells were arranged orderly with a clear tidal line. A large number of articular chondrocytes died in model group, while it was improved in miR-9 group. The Mankin’s score was 3.52±0.79 points in control group, 6.73±0.95 points in model group, and 5.37±0.61 points in miR-9 group, showing significant differences among the three groups (p<0.05). Results of immunohistochemistry showed that the protein expressions of Notch1 and Bax were higher in model group, but lower in control group and miR-9 group (p<0.05). The protein expression of Bcl-2 was lower in model group but was upregulated in control group and miR-9 group (p<0.05). The results of Reverse Transcription-Polymerase Chain Reaction (RT-PCR) revealed that the expressions of Notch1 and Bax in control group were lower than those in model group and miR-9 group (p<0.05), while the expression of Bcl-2 in model group was lower than that in control group and miR-9 group (p<0.05). According to the results of immunohistochemistry, the CII optical density (OD) value was 0.18±0.013, 0.25±0.05 and 0.22±0.009 in control group, model group, and miR-9 group, respectively. It could be seen that the CII OD value was the highest in model group, indicating that the CII expression in articular cartilage in osteoarthritis was negatively correlated with the severity of osteoarthritis.

CONCLUSIONS: MiR-9, through the down-regulation of the expressions of Notch and Bax, can activate the Bcl-2 to promote the differentiation and regeneration of chondrocytes. It can facilitate the cartilage regeneration of osteoarthritis in rabbits through the mediation of the CII expression.

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