SHORT-TERM EFFECTS OF ORGANIC SILICON ON TRABECULAR BONE IN MATURE OVARIECTOMIZED RATS

Silicon is known to ensure an essential role in the formation of cross -links between collagen and proteoglycans during bone growth. In this study, we have evaluated the short-term effects of a preventive treatm ent with silanol, a soluble organic silicon (Si), on trabecular bone i n mature ovariectomized rats. Three-month-old rats were sham-operated (sham) or were ovariectomized (OVX) and treated with 10 mug/kg/day of 17beta estradiol (E2), or with 0.1 mg Si/kg/day or 1.0 mg Si/kg/day of silanol for 1 month. Plasma alkaline phosphatase and osteocalcin leve ls were increased by 50% in OVX rats compared with sham rats and were corrected by E2 but not by silanol treatment. The trabecular bone volu me measured at the tibial metaphysis was decreased by 48%, and histomo rphometric indices of bone resorption and formation were increased in OVX rats compared with sham, and these parameters were corrected by E2 treatment. Treatment of OVX rats with silanol decreased the osteoclas t surface by 31% and the number of osteoclasts by 20%. The mineral app osition rate, the bone formation rate, and the osteoblast surface at t he tibia metaphyseal area were increased by 30% at the higher dose of silanol compared with OVX rats. In contrast, silanol treatment had no effect on the periosteal apposition rate. The reduction of the metaphy seal bone resorption and the increased bone formation induced by silan ol resulted in a slight improvement of the trabecular bone volume (+ 1 4%) compared with controls. The results indicate that a short-term pre ventive treatment with the organic silicon silanol partially prevented the trabecular bone loss in mature OVX rats by reducing bone resorpti on and increasing bone formation, possibly through stimulatory effects on the formation and/or the stability of the organic bone matrix.