Effects of soy isoflavones and mechanical vibration on rat bone tissue

Abstract

Objective To investigate the effects of soy isoflavones (Iso) and mechanical vibration treatments alone or combined on bone extracellular matrix constituents of ovariectomized rats.

Methods Forty female Wistar rats at the age of 6 months were ovariectomized (Ovx) and ten were sham-operated (sham). After 3 months, the animals were divided into five groups: GI (sham); GII (Ovx); GIII, ovariectomized and orally treated with isoflavones (200 mg/kg) for 90 consecutive days; GIV, ovariectomized and submitted to vibration for 90 days (5 days/week); GV, ovariectomized and treated with isoflavones plus vibration. After treatments, the rats were euthanized, and their femurs were removed for histological routine and biochemical study. Histological sections were stained with hematoxylin–eosin, picrosirius red and alcian blue. Shaft of femurs were submitted to biochemical assay and tibias were subjected to biophysical and biomechanical tests.

Results Treatments did not have significant effects on the trabecular bone volume, but the combined treatments showed trophic effects on the cortical bone width and area. Bone density and the content of organic material of the tibias were higher in the GIV and GV groups. The GV group showed the highest presence of mature collagen fibers and content of total glycosaminoglycans, while the highest contents of chondroitin sulfate and other sulfated glycosaminoglycans were seen in the GIV group.

Conclusion The mechanical vibration treatment is more efficient than soy isoflavones in improving bone quality by increasing the bone density, the content of sulfated glycosaminoglycans and the presence of mature collagen fibers. In addition, the combined interventions have partial trophic and synergistic effects that are bone site-specific in ovariectomized rats.

Key words::

• ISOFLAVONES
• MECHANICAL VIBRATION
• BONE
• COLLAGEN
• GLYCOSAMINOGLYCANS
• RATS

ACKNOWLEDGEMENTS

The authors wish to thank Gisela Sasso for technical assistance and Dr Marise Lazaretti-Castro and Dr Monica Longo de Oliveira (Federal University of São Paulo), for providing the vibration platform.

Conflict of interest The authors report no conflict of interest. The authors alone are responsible for the content and writing of this paper.

Source of funding This research was supported by CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) – Brazil.