Tanshinone prevents cancellous bone loss induced by ovariectomy in rats

To investigate the skeletal effects of total tanshinone in ovariectomized rats by analyzing cancellous bone histomorphometry of fourth lumbar vertebrae (LV4) and proximal tibial metaphyses (PTM).

Four-month-old Sprague-Dawley female rats were sham-operated and treated with vehicle or ovariectomized and treated with either vehicle, total tanshinone (200 mg x kg(-1) x d(-1), equivalent to 35 microg x kg(-1) x d(-1) of tanshinone II A and 16 microg x kg(-1) x d(-1) of cryptotanshinone), or 17alpha-ethynylestradiol (30 microg x kg(-1) x d(-1) as positive treatment group) starting one day post-surgery for 10 weeks. Double in vivo fluorochrome labeling was administered to all rats. The undecalcified longitudinal LV4 and PTM sections were cut and stained with Goldner's Trichrome (4-microm thickness) or unstained (8-microm thickness) for the bone histomorphometric analysis.

A significant decrease in trabecular bone volume (BV/TV) and trabecular number (Tb.N) and a significant increase in osteoclast surface (OCS/BS) and mineralizing surface (MS/BS) were found in both LV and PTM of vehicle-treated OVX rats compared with sham controls. Tanshinone completely prevented the decreases in BV/TV and Tb.N and the increase in OCS/BS in the LV4, and partially prevented the decreases in BV/TV and Tb.N in the PTM of OVX rats. In addition, tanshinone increased trabecular thickness (Tb.Th) whereas it did not alter MS/BS. Moreover, tanshinone had no effect on uterine weight and body weight of OVX rats. Estrogen treatment increased BV/TV and Tb.N and decreased OCS/BS, but, also markedly decreased MS/BS and increased uterine weight in OVX rats.

The current study demonstrated that the adequate supply of tanshinone prevented OVX-induced cancellous bone loss in rats through inhibition of elevated bone resorption.