Long-term follow-up of the bone marrow adipose tissue distribution in ovariectomized rats reveals a clustering of adipocytes at the tibiae trabecular bone surface
Résumé
Introduction: During osteoporosis, higher bone marrow adipose tissue (BMAT) is associated with lower bone density (Schwartz AV, 2015). However relationship between BMAT and bone loss is unclear. This study aims to analyze the 3D-relationship between BMAT and tibiae trabecular bone during ovariectomy in a long-term follow-up on mature rats.
Methods: Female Sprague-Dawley rats of six-month-old (n=45) were OVX or SHAM operated and tibiae were studied at 6 (baseline), 10 (M4) and 15 (M9) months. An advanced microCT imaging (Coutel X, 2018) allowed accurate alignment of both the BMAT distribution and bone micro-architecture as well as calculation of the distance of the BMAT from the bone surface.
Results: Bone microarchitectural parameters were altered in both M4- and M9-OVX groups compared to the corresponding SHAM groups: BV/TV (-63%, -65%, p<0.0001), Tb.N (-65%, -68%, p<0.0001), Tb.Th (+7%, +13%, p=0.01), Tb.Sp (+188%, +238%, p<0.0001).
BMAT parameters were increased in both M4- and M9-OVX groups compared to the corresponding SHAM groups: MaV/TV (+34%, +34%, p<0.0001) and AdV/Ma.V (+103%, +483%, p<0.0001).
At baseline, BMAT content (Ad per µm3) was higher at 80-100µm distance to trabecular bone in comparison to 0-20µm (+79%, p=0,0004). A higher BMAT content was located close to trabecular bone surface (0-20µm) in both M4 and M9 OVX groups compared to baseline (+92%, +87%, p=0,0002/0,0004) and compared to the corresponding SHAM groups (+53%, +75%, p=0,0008/0,0002).
Conclusion: The present study demonstrate that trabecular bone loss occurring during ovariectomy is associated with BMAT clustering at bone surface in short and long-term processes. Based on the present results, additional studies in the paracrine role of BMAT mediators appears of great interest for better physiopathology understanding of bone loss and should lead to new treatments.
Keywords: Bone marrow adipose tissue – Bone microstructure – Osteoporosis – Rat model - microCT