The influence of sexual and phytohormones on remodelling of the osteoporotic bone of male rat after trepanation and whole-body-vibration.

The aim of the study was designed to evaluate the effect of dihydrotestosteron (DHT), 17-ß-estrogen (E2), genistein (GEN) and equol (EQ) on remodelling of injured and osteoporotic tibia of male rat, which additionally were exposed to a whole-body-vibration. After orchiectomy and whole-body-vibration for all 172 Sprague Dawley male rats, the animals were divided in 5 groups. The first group was only fed with soja free food (control group), whereas the other groups were fed with a supplement of hormones (DHT, E2, GEN or EQ). Together with the change of food the tibia of each rat was perforated by a drill with a diameter of 1.5 mm. After a time period of 2, 3 and 8 weeks (three series) rats of each group were analyzed. Additionally, half of the animals of the third series were exposed to a second whole-body-vibration for four weeks. To investigate the mineral-apposition-rate (MAR) in the cortical and trabecular bone the polychrome fluorescence labelling was measured with help of two fluorescence labels, calcein and alizarin. Our results show that the trepanation of the rat tibia induced the formation of woven bone, which was replaced by lamellar bone especially by the therapy with EQ. Both, DHT und E2 stimulated the apposition of the bone in the cortical and trabecular tissue in a much stronger way than the treatment with GEN or EQ. E2 accessorily induced a high MAR on the endostal and periostal side of cortical bone whereas DHT only induced a high MAR on the periostal side. Only the treatment with the phytohormone GEN demonstrated the apposition of the bone on the periostal side of the tissue which was comparable to the effect of the E2 application. Simultaneously, rats which were fed with GEN demonstrated the highest effect concerning bone apposition in association with the second whole-body-vibration. Furthermore we found out that the dimension of the fluorescence labelling is time-dependent, so the labelling became smaller in the course of time. It is much likely that this is due to increasing bone-mineralization and compaction. In summary, it was shown that the donation of sexual hormones significantly increased the remodelling of the cortical and trabecular bone. In comparison to that, the treatment with phytohormones had a much lower effect on bone remodeling. Besides, the donation of EQ in combination with a whole-body-vibration seemed to support the replacement of woven bone by lamellar bone. 2014-04-1