Bone Abstracts

Background: In postmenopausal osteoporosis, a loss of bone volume due to increased bone turnover is accompanied by a higher volume of bone marrow adipose tissue (BMAT). If this static relationship is based on a functional relationship, BMAT is a potential target for treating osteoporosis. While it is known that estrogen can reduce BMAT, it is still unknown whether raloxifene – a selective estrogen receptor modulator – can also reduce BMAT.

Objective: To determine 1) the correlation between BMAT and bone turnover in postmenopausal osteoporotic women and 2) the effect of raloxifene on BMAT.

Methods: We retrospectively analyzed paired iliac crest biopsies from 26 postmenopausal osteoporotic women enrolled in the MORE trial, both at baseline and after 2 years of treatment with placebo or raloxifene. All subjects received oral calcium and vitamin D3. Standardized bone histomorphometry and BMAT parameters were measured in Goldner stained sections.

Results: At baseline, BMAT was correlated with bone volume (R=−0.382; P=0.03), but not with bone formation rate or osteoclast number. There was an increase in adipocyte density in the raloxifene group, while there was no change in adipocyte density in the in the placebo group (mean change from baseline: 34.1 S.D. 28.9 vs −3.5 S.D. 29.5 cells/mm²; P=0.003). The adipocyte diameter did not change after raloxifene, while after placebo there was an increase in adipocyte diameter (mean change from baseline: −0.5 S.D. 2.8 vs 3.1 S.D. 5.1 μm; P=0.03).

Conclusion: This study suggests that BMAT is not correlated with bone turnover in iliac crest biopsies of postmenopausal osteoporotic women. Furthermore our results indicate that raloxifene does not reduce the volume of BMAT, but rather increases the number of bone marrow adipocytes while preventing an increase in the size of bone marrow adipocytes.