Soybean isoflavone can protect against osteoarthritis in ovariectomized rats

Osteoarthritis (OA) is a chronic and incurable disease and a leading cause of significant pain and disability that is closely associated with aging and obesity. An appropriate long-term therapy regimen is presently unknown. An estrogen deficiency after menopause increases the incidence and severity of OA in women. Soybean isoflavone have weak estrogenic effects in several organs and have been considered as a potentially safe natural selective estrogen receptor modulator. The present study aimed to determine the effects of isoflavone on cartilage degradation in ovariectomized rats. Six-month-old female Sprague-Dawley (SD) rats (n = 40) were randomly assigned to sham operation (n = 10), ovariectomy (OVX) (n = 15) or OVX + isoflavone (OVXI) (n = 15) groups. The OVXI group was fed with soybean isoflavone (51.0 mg/kg/day) for nine weeks, then knee joints were excised. Cartilage degradation was evaluated by toluidine blue staining joint specimens, and by comparing values for serum C-telopeptides of Type II collagen (CTX-II) and cartilage oligomeric matrix protein (COMP) between baseline and the end of the study. Cartilage damage scored by Toluidine blue staining was significantly lower in the OXVI, than the OVX group (P < 0.016). The CTX-II values before the surgical procedure and the end of experiment, did not significantly differ among the groups. Values for COMP in all samples were below detection limits in all samples. Soy bean isoflavone limited the degeneration of cartilage induced by OVX in rats.