BACKGROUND: Estrogen levels regulate changes in osteoarthritis (OA) by inhibiting degradation of the extracellular matrix. Recent in vitro studies have also shown the role of microRNA-140-5p (miR-140-5p). This study aimed to investigate the role of estrogen deficiency, selective modulation of expression of the estrogen receptor (ER), and expression of miR-140-5p in cartilage and subchondral bone remodeling in an ovariectomized rat model of postmenopausal OA.

MATERIAL AND METHODS: Female Sprague-Dawley rats included two model groups, ovariectomized (OVX) rats and rats with destabilization of the medial meniscus (DMM) rats. Two months after surgery, estrogen levels were measured by the enzyme-linked immunosorbent assay (ELISA). Three-dimensional (3D) micro-computed tomography (micro-CT) was used to image the knee joints. Rats were treated with subcutaneous injection of estrogen (E2) or the selective estrogen receptor modulator (SERM), raloxifene (RAL), for one month. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect miR-140-5p in serum, and histology of the knee joint cartilage and bone was performed.

RESULTS: In the ovariectomized rat model of OA, estrogen therapy reduced the degree of cartilaginous degeneration, while treatment with raloxifene showed no significant effect. Expression levels of miR-140-5p in the OA model group were significantly lower than the control group. Micro-CT showed that in the model group, anterior cruciate ligament dislocation and subchondral bone density were significantly reduced.

CONCLUSIONS: In an ovariectomized rat model of postmenopausal OA, estrogen deficiency resulted in resorption of subchondral bone and degeneration of articular cartilage.

Keywords: Estrogens, Osteoarthritis, Raloxifene, Anterior Cruciate Ligament, Bone Density, Bone Remodeling, Cartilage, Cartilage, Articular, Extracellular Matrix, Knee Joint, Ovariectomy, Postmenopause, Receptors, Estrogen