Intervention timing of strontium treatment on estrogen depletion-induced osteoporosis in rats: bone microstructure and mechanics.

To evaluate the effect of intervention timing of Sr treatment on trabecular bone microstructure and mechanics. Ninety female rats were randomly divided into three batches with three groups in each batch. Each group was divided according to the initiation timing of vehicle or strontium compound (SrC), which was at week 0 (early), 4 (mid-term) and 8 (late) after the ovariectomy, respectively. The treatment lasted for 12 weeks. The trabecular bone biomechanical properties, trabecular bone tissue mechanical properties, trabecular bone microstructure, and bone remodeling were analyzed with mechanical testing, nanoindentation, microCT, and histomorphometry, respectively. The osteoblast and osteoclast phenotypic genes were analyzed with real-time polymerase chain reaction (PCR). Early and mid-term Sr treatment significantly increased biomechanical properties of trabecular bone, which was associated with increased microarchitecture parameters, increased bone formation parameters and up-regulation of osteoblast-related gene expression. Late Sr treatment failed to exert a beneficial effect on any of those parameters. The beneficial effect of Sr was dependent on the intervention timing in ovariectomized rats.

Peng S ，Liu XS ，Huang S ，Pan H ，Zhen W ，Zhou G ，Luk KD ，Guo XE ，Lu WW ... -  《-》

The beneficial effect of icaritin on osteoporotic bone is dependent on the treatment initiation timing in adult ovariectomized rats.

Epimedium-derived flavonoids (EFs) have a potential to treat established osteoporosis in postmenopausal women. However, one of the main disadvantages of the compound is the high volume and dosage during long-term administration period. Meanwhile, the beneficial effect of EFs on osteoporotic bone depends greatly on the intervention timing. Whether icaritin (ICT), an active molecular compound from EFs, can exert beneficial effect on osteoporotic bone and whether the beneficial effect is also dependent on the intervention timing remain unknown. The objective of this study was to evaluate the effect of the early and late ICT treatment on bone turnover markers, trabecular architecture, bone remodeling, biomechanics, colony formation of bone marrow stromal cells and osteoblast, adipocyte and osteoclast-related gene expression in adult ovariectomized rats. Eighty 9-month-old female rats (n=8/group) were sham-operated (Sham) or ovariectomized (OVX). The OVX rats were subjected to ICT treatment initiation at 1 month (early treatment) and 3 months (late treatment) post-operation, respectively. The vehicle-treated Sham and OVX rats starting at month 1 and month 3 post-operation served as the corresponding controls (Sham and OVX controls) for early and late ICT treatment, respectively. Those Sham and OVX rats sacrificed immediately before early and late ICT treatment served as the pretreatment baseline controls. Both ICT and vehicle treatments lasted for 2 months. The bone turnover markers, trabecular architecture, bone remodeling and bone biomechanical properties were analyzed with biochemistry, microCT, histomorphometry and mechanical testing, respectively. The population of bone marrow stromal cells (BMSCs) and osteoblasts were evaluated with colony formation assays, respectively. The expression levels of osteoblast, adipocyte and osteoclast-related genes in bone marrow were assessed by real-time polymerase chain reaction (PCR), respectively. At the tissue level, early ICT treatment remarkably restored the trabecular bone mass, trabecular architecture and bone biomechanical properties towards pretreatment Sham levels, and significantly increased bone formation from pretreatment OVX level and markedly inhibited bone resorption towards pretreatment Sham level, whereas late ICT treatment failed to have any effect. At the cellular and molecular level, early ICT treatment significantly increased the number of osteoblastic colonies and the level of osteoblast-related gene expression compared to pretreatment OVX levels and remarkably decreased adipocyte and osteoclast-related gene expression towards pretreatment Sham levels. Late ICT treatment failed to have beneficial effect on any of these parameters. ICT can exert anabolic and anti-resorptive effect on osteoporotic bone. The beneficial effect of ICT treatment is dependent on the intervention timing in established osteoporosis induced by estrogen depletion.

Peng S ，Zhang G ，Zhang BT ，Guo B ，He Y ，Bakker AJ ，Pan X ，Zhen W ，Hung L ，Qin L ，Leung WN ... -  《-》

The cross-talk between osteoclasts and osteoblasts in response to strontium treatment: involvement of osteoprotegerin.

The mechanism for the uncoupling effects of Sr on bone remains to be evaluated. Osteoblasts play important roles in osteoclastogenesis through regulating receptor activated nuclear factor kappa B (RANK) ligand (RANKL) and osteoprotegerin (OPG) expression. We hypothesize that OPG plays an important role in the cross-talk between osteoclasts and osteoblasts in response to Sr treatment. MC3T3E1 cells were treated with Sr chloride (0-3 mM) and conditioned media were collected at 24h after the treatment. The effect of conditioned media on osteoclastogenesis was evaluated by tartrate-resistant acid phosphatase (TRAP) staining and bone resorption pits analysis. OPG and RANKL mRNA expressions in osteoblastic cells and protein secretion in the conditioned media were analyzed with real-time PCR and ELISA assay, respectively. The role of OPG in Sr-mediated inhibition of osteoclastogenesis was further evaluated with anti-OPG antibody in pre-osteoclastic cells. The role of OPG in Sr-mediated uncoupling effects on osteoporotic bone was evaluated by an animal study. Ovariectomized rats were oral administrated with vehicle or Sr chloride for two months supplemented with anti-IgG antibody (control) or anti-OPG antibody. The effects of OPG neutralization after Sr treatment on bone metabolism were analyzed by microCT, bone histomorphometry and biochemical analysis. The conditioned media derived from Sr-treated osteoblastic cells exerted a dose-dependent inhibitory effect on osteoclastic differentiation and resorptive activity in pre-osteoclastic cells. OPG mRNA expression and protein secretion in osteoblastic cells were significantly increased after Sr treatment. Neutralization with anti-OPG antibody abolished the inhibitory effect of conditioned media on RANKL-induced osteoclastogenesis. The uncoupling effects of Sr treatment on trabecular bone were evidenced by greater bone volume and trabecular number, greater osteoid surface and bone formation rate, while less osteoclast surface. These effects were attenuated by the OPG neutralization by anti-OPG antibody injection. The evidences from the in vitro and in vivo studies suggested that OPG played an important role in the uncoupling effect of Sr on bone metabolism, possibly by acting as a cross-talk molecule between osteoclasts and osteoblasts in response to Sr treatment.

Peng S ，Liu XS ，Huang S ，Li Z ，Pan H ，Zhen W ，Luk KD ，Guo XE ，Lu WW ... -  《-》

A standardized phytopreparation from an Indian medicinal plant (Dalbergia sissoo) has antiresorptive and bone-forming effects on a postmenopausal osteoporosis model of rat.

Khedgikar V ，Gautam J ，Kushwaha P ，Kumar A ，Nagar GK ，Dixit P ，Chillara R ，Voruganti S ，Singh SP ，Uddin W ，Jain GK ，Singh D ，Maurya R ，Chattopadhyay N ，Trivedi R ... -  《-》

Thyroid-stimulating hormone restores bone volume, microarchitecture, and strength in aged ovariectomized rats.

Sampath TK ，Simic P ，Sendak R ，Draca N ，Bowe AE ，O'Brien S ，Schiavi SC ，McPherson JM ，Vukicevic S ... -  《JOURNAL OF BONE AND MINERAL RESEARCH》