CHEMISTRY OF OSTEOPOROSIS: ALTERATIONS OF BONE QUALITY IN OVARIECTOMIZED MONKEYS REVEALED BY SYNCHROTRON INFRARED MICROSPECTROSCOPY.

Reduced bone density is a well-known feature of osteoporosis, where the trabecular bone compartment is most affected. Yet, little is known about how the disease affects the chemical composition of bone and its impact on fracture risks. Using ovariectomized cynomolgus monkeys as a model for osteoporosis, we examined the chemical changes in both trabecular and cortical bone as a function of time after ovariectomy. In addition, the effects of nandrolone decanoate treatment were examined. Fluorochrome labels were used to identify regions of bone remodeled 1 year (calcein) and 2 years (alizarin complexone) after ovariectomy, and synchrotron infrared microspectroscopy was used to determine protein and mineral content, and composition in these particular regions of bone. Our results demonstrate that ovariectomy does not affect the average mineralization levels of cortical or trabecular bone. However, the rate of new bone mineralization after ovariectomy increases in cortical bone, whereas it remains unchanged in trabecular bone. Ovariectomy reduces the average carbonate accumulation in cortical bone. Although it does not affect the average trabecular bone accumulation, the rate at which carbonate accumulates in new trabecular bone is reduced after ovariectomy. The average collagen cross-linking of mature bone is not affected by ovariectomy, but it significantly increases in new trabecular bone and decreases in new cortical bone. Treatment of the ovariectomized monkeys with nandrolone decanoate, a drug that decreases bone resorption, reverses most of the chemical changes in the cortical bone to the level of the ovary-intact controls, but has little effect on the trabecular bone. [ABSTRACT FROM AUTHOR]