Suitable Ovariectomy Age for Screening the Functional Agents by Femoral Bone Strength in Osteoporosis Model Rats

Abstract Osteoporosis is a major contributor to the high frequency of bone fracture in elderly women. The ovariectomized (OVX) rat is one of the excellent pre-clinical animal model of osteoporosis. Following ovariectomy, rapid loss of cancellous bone mass and strength occurs. Maximum breaking force of the femoral diaphysis is a major parameter to determine the severity of the osteoporosis directly. Although, the suitable age at ovariectomy remains obscure to evaluate the maximum breaking force of the femoral diaphysis. Accordingly, the suitable rat age at ovariectomy to evaluate the maximum breaking force of the femoral diaphysis for screening of therapeutic or functional agents was determined. Female Sprague-Dawley rats (6, 13 or 30 week-old) were used. Rats of each age were divided into two groups; underwent bilateral OVX and underwent bilateral laparotomy (sham). All rats were fed an AIN93G-based normal diet for further 10 weeks. Reduction of maximum bone strength in femur and increase of body weight gain were observed only in 6 week-old OVX rats after 10-week acclimatization, whereas the difference was obscure in 13 and 30 week-old OVX rats. Therefore, ovariectomy at 6 week-old was the suitable age for osteoporosis model to screen the effects of functional agents in rats