Protective effects of equol on the cartilage and subchondral bone in ovariectomized rats with osteoarthritis

OBJECTIVE(S): This study aimed to determine the therapeutic effect of equol (EQ) on osteoporotic osteoarthritis (OP OA). MATERIALS AND METHODS: Thirty-six 12-week-old female Sprague-Dawley rats were randomly divided into sham group, OP OA group, and EQ group (n=12). OP OA was induced by anterior cruciate ligament transection (ACLT) combined with ovariectomy (OVX). EQ was orally administrated (10 μg/g/day) after the operation for 12 weeks. The efficacy was evaluated by gross pathology and histopathologic evaluation. The underlying mechanism was investigated by immunohistochemical analysis, micro-computed tomography (micro-CT) scanning, and tartrate-resistant acid phosphatase (TRAP) staining. RESULTS: EQ effectively retarded cartilage degeneration, decreased the levels of matrix metalloproteinases-13 (MMP-13), a disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS-5), nuclear factor-kappa B P65 (NF-κB P65) and caspase-3, and increased the levels of collagen type II (Col-II), Col-I, aggrecan (AGG), and inhibitor of NF-κB α (IκBα) in the cartilage. In addition, EQ increased bone mineral density, improved the microstructural parameters of the subchondral bone (SB), and decreased the number of osteoclasts. CONCLUSION: EQ exerted a chondroprotective effect on OP OA in rats, associated with inhibition of the NF-κB signaling pathway and chondrocyte apoptosis. Furthermore, EQ showed an osteoprotective effect on SB via inhibiting osteoclastic activities.