Inhibition of miR-203 Ameliorates Osteoarthritis Cartilage Degradation in the Postmenopausal Rat Model: Involvement of Estrogen Receptor α.

miR-203 is known to target estrogen receptor α (ERα) in various cancer cell lines, such as MCF-7. However, whether miR-203 regulates ERα and contributes to the onset and progression of osteoarthritis (OA) is poorly understood. A combined protocol of the bilateral ovariectomy and the intra-articular monosodium iodoacetate injection was applied to establish a postmenopausal OA model in rats. Real-time quantitative polymerase chain reaction was used to detect miR-203 and mRNAs and Western blotting was exploited to quantify the expression levels on the protein level. Enzyme-linked immunosorbent assays were deployed to detect the expression of matrix metalloproteinase-1 (MMP-1), MMP-3, prostaglandin E (PGE), and collagen type II degradation (CTX-II) in serum samples. Dual-luciferase reporter assay was utilized to confirm the direct binding of miR-203 on ERα in postmenopausal OA rats. Expression of miR-203 was elevated; while ERα mRNA and protein were downregulated in postmenopausal OA rats, compared with sham rats. Dual-luciferase reporter assay confirmed miR-203 bound and negatively regulated ERα, resulting in promoted cellular inflammation and cartilage destruction in postmenopausal OA rats. Suppression of miR-203 using a specific inhibitor ameliorated cartilage degradation in postmenopausal OA rats. miR-203 is pivotal in the onset and progression of OA in the postmenopausal rat model, and holds promise for a therapeutic target of OA treatment.