Long-Term Follow-up After Ovariectomy Reveals Correlations Between Bone Marrow Adiposity and Trabecular Bone Quality in the Proximal Metaphysis of Tibiae in Rats

This study aimed to evaluate the correlation between BMAT and bone quality, describe the long-term effects of ovariectomy on bone, and investigate BMAT's spatial distribution. Fifteen-months-old female Sprague‒Dawley rats were studied, comparing ovariectomized (OVX, n = 22) and sham-operated (SHAM, n = 11) groups at 6 months. Tibias were analyzed for bone microarchitecture, BMAT (microcomputed tomography), mineral parameters (quantitative backscattered electron imaging), and bone composition (Raman microspectroscopy). The OVX tibias showed severe trabecular bone loss (lower bone volume/total volume, p < 0.001) with increased BMAT (higher adipose volume per marrow volume, p < 0.001), decreased mineral content (lower calcium concentration, p < 0.001), and altered organic components (lower mineral/matrix ratio in new bone, p = 0.03 trabecular surface, p < 0.001 trabecular core). When the data are pooled over both groups (SHAM and OVX), the adipose volume/marrow volume ratio was negatively correlated with bone volume/total volume (r = - 0.79, p < 0.001) and mineral/matrix ratio (r = - 0.37, p = 0.04 trabecular surface; r = - 0.65, p < 0.001 trabecular core) and positively correlated with crystallinity (r = 0.55, p = 0.001 trabecular surface; r = 0.49, p = 0.006 trabecular core). The mineral/matrix ratio of trabecular surface new bone was strongly negatively correlated with the adipose compartment nearest to the bone surface. These findings suggest mechanisms underlying BMAT's role in bone resorption.