MR spectroscopy and micro-CT in evaluation of osteoporosis model in rabbits: comparison with histopathology

Abstract

MRS revealed gradually increasing bone marrow fat in rabbits rendered osteoporotic. Marrow adipogenesis occurs in synchrony with deterioration of trabecular microarchitecture. Pathology revealed an early increase in number of marrow adipocytes in osteoporosis. MRS may help assess early pathophysiological bone marrow changes in osteoporosis.

Longitudinal assessment of oxytocin efficacy on bone and bone marrow fat masses in a rabbit osteoporosis model through 3.0-T magnetic resonance spectroscopy and micro-CT

“…The rabbits in the control group were subjected to sham operation, in which the ovaries were lifted and then returned to the original position. The animals in the OP and OT groups were subjected to bilateral OVX [13,14]. The rabbits in the OT group were subcutaneously injected daily with 1 mg/kg oxytocin from 2 weeks after OVX for 8 weeks or up to the scheduled time points [10].…”

“…Spectral assignments were performed using the protocols of previous studies [13,19], and only clearly identifiable peaks were measured. The MR spectra of the bone marrow exhibited two dominant peaks, namely water at a shift of 4.65 ppm and lipid at a shift of 1.3 to 0.9 ppm.…”

“…Histopathological results were read in a blinded manner, particularly without knowledge of group allocation status, to avoid any bias in the final analysis. Three representative sections (top, middle, and bottom levels of the specimen) per femur were chosen to be imported into the Leica Q-win Plus image analysis system (Leica Microsystems, Wetzlar, Germany), according to the previously described method [13,19]. The reading area starts 1.0 mm from the lower part of the distal growth plate of the femoral head superior to the distal shaft for 17 mm.…”

“…Many studies show that marrow fat content increases with trabecular microarchitecture deterioration [13,14]. The bone density of female patients with postmenopausal osteoporosis is inversely proportional to bone marrow fat content [15,16].…”

“…Bone structure studies are limited to small animals, and specimen imaging is exclusively limited to micro-CT. Osteoporosis imaging studies in literature are mostly restricted to one kind of imaging method and lack combined analysis with other imaging techniques and support of quantitative histopathological results [1,5,6]. MRS quantitatively analyzes bone marrow fat and water metabolism in a rabbit osteoporosis model [13]. Rabbits show active Haversian remodeling, which may be very useful for test agents acting on bone remodeling, especially those with strong anabolic effects.…”