Estrogen therapy associated with mechanical vibration improves bone microarchitecture and density in osteopenic female mice

Abstract

We investigated the effects of estrogen therapy (ET) associated with low‐intensity and high‐frequency mechanical vibration (MV) on bone tissue in osteopenic female mice. Fifty 3‐month‐old female Swiss mice were ovariectomized (OVX) or sham‐operated, and distributed after 4 months into the following groups, with 10 animals per group: Sham; Control, OVX + vehicle solution; MV, OVX + MV; ET, OVX + 17β‐estradiol; and MV + ET, OVX + MV and 17β‐estradiol. Both vehicle solution and 17β‐estradiol (10 μg kg−1 day−1) were injected subcutaneously 7 days per week, and vibration (0.6 g, 60 Hz) was delivered 30 min per day, 5 days per week. Bone mineral density (BMD) and body composition were evaluated by densitometry at baseline and after 60 days of treatment when the animals were euthanized, and their femurs underwent histomorphometric and histochemical analyses. The Control group showed increased weight and fat percentage, while the ET and MV + ET groups showed increased lean mass but decreased fat percentage. At the end of the treatment period, the BMD decreased in Control, remained constant in Sham and MV, and increased in ET and MV + ET. The MV + ET group showed the greatest bone volume compared with Sham (129%), Control (350%), MV (304%) and ET (14%). No differences occurred in cortical thickness. The Control group showed the highest content of mature collagen fibers, while the MV + ET group showed the highest content of immature collagen fibers. In conclusion, ET plus MV was effective in improving bone quality in osteopenic female mice, and this improvement is associated with specific changes in trabecular but not cortical bone.

Individualized cyclic mechanical loading improves callus properties during the remodelling phase of fracture healing in mice as assessed from time-lapsed in vivo imaging

“…Targets (e.g. Sclerostin, Estrogen signalling) found via these comprehensive studies were then assessed in detail in further studies using either models with local [36][37][38] or global load application 39 . As the main underlying mechanisms of bone adaptation to loading were identified using local models of loading (ulna, tibia ..), this indicates that comprehensive spatio-temporal mechano-molecular analyses in fracture healing will require tightly regulated models with local application of mechanical loading being more controllable and less prone to variation induced by confounding factors compared to models with global loading application.…”