β-Ecdysone Augments Peak Bone Mass in Mice of Both Sexes

Authors

Weiwei Dai PhD, HongLiang Zhang MD, PhD, Zhendong A. Zhong PhD, Li Jiang MD, Haiyan Chen MS, Yu-An Evan Lay MS, Alexander Kot BS, Robert O. Ritchie PhD, Nancy E. Lane MD, Wei Yao MD

Abstract

Background One of the strongest predictors for osteoporosis is peak bone mass. Interventions to augment peak bone mass have yet to be developed. β-Ecdysone (βEcd), a natural steroid-like compound produced by arthropods to initiate metamorphosis, is believed to have androgenic effects and so may be used to augment bone mass.

Questions/purposes The purpose of this study was to use both male and female (1) gonadal-sufficient; and (2) -insufficient mice to investigate sex differences in terms of bone development and structure after βEcd administration.

Method Two-month-old male and female Swiss-Webster mice were randomized to receive either vehicle or βEcd (0.5 mg/kg) for 3 weeks. In a separate experiment to evaluate the effects of βEcd on sex hormone-deficient mice, gonadectomy was performed in male (orchiectomy [ORX]) and female mice (ovariectomy [OVX]). Sham-operated and the ORX/OVX mice were then treated for 3 weeks with βEcd. Primary endpoints for the study were trabecular bone structure and bone strength.

Results In male mice, the trabecular bone volume was 0.18 ± 0.02 in the placebo-treated (PL) and 0.23 ± 0.02 in the βEcd-treated group (p < 0.05 versus PL); and 0.09 ± 0.01 in the ORX group (p < 0.05 versus PL) and 0.12 ± 0.01 in the ORX + βEcd group. Vertebral bone strength (maximum load) was 43 ± 2 in PL and 51 ± 1 in the βEcd-treated group (p < 0.05 versus PL); and 30 ± 4 in the ORX group (p < 0.05 versus PL) and 37 ± 3 in the ORX + βEcd group. In female mice, trabecular bone volume was 0.23 ± 0.02 in PL and 0.26 ± 0.02 in the βEcd-treated group (p < 0.05 versus PL); and 0.15 ± 0.01 in the OVX group (p < 0.05 versus PL) and 0.14 ± 0.01 in the OVX + βEcd group. Maximum load of the vertebrae was 45 ± 2 in PL and 48 ± 4 in the βEcd-treated group; and 39 ± 4 in the OVX group (p < 0.05 versus PL) and 44 ± 4 in the OVX + βEcd group.

Conclusions These findings suggest the potential use of βEcd in the augmentation of bone mass in growing male and female mice. It may also partially prevent the detrimental effects of gonadectomy on trabecular bone.

Clinical Relevance Our results support the potential use of βEcd or nature products that are rich in βEcd to augment peak bone mass. βEcd may differ from the other anabolic hormone treatments that may have severe side effects such as serious cardiac complications. However, its effects on humans remain to be determined.

Link To Article

http://dx.doi.org/10.1007/s11999-015-4246-5

Osteoblast function and bone histomorphometry in a murine model of Rett syndrome

Authors

Mary E. Blue, Adele L. Boskey, Stephen B. Doty, Neal S. Fedarko, Mir Ahamed Hossain, Jay R. Shapiro

Abstract

Rett syndrome (RTT) is an X-linked neurodevelopmental disorder due to mutations affecting the neural transcription factor MeCP2. Approximately 50% of affected females have decreased bone mass. We studied osteoblast function using a murine model of RTT. Female heterozygote (HET) and male Mecp2-null mice were compared to wild type (WT) mice. Micro-CT of tibia from 5 week-old Mecp2-null mice showed significant alterations in trabecular bone including reductions in bone volume fraction (−29%), number (−19%), thickness (−9%) and connectivity density (−32%), and increases in trabecular separation (+28%) compared to WT. We also found significant reductions in cortical bone thickness (−18%) and in polar moment of inertia (−45%). In contrast, cortical and trabecular bones from 8 week-old WT and HET female mice were not significantly different. However, mineral apposition rate, mineralizing surface and bone formation rate/bone surface were each decreased in HET and Mecp2-null mice compared to WT mice. Histomorphometric analysis of femurs showed decreased numbers of osteoblasts but similar numbers of osteoclasts compared to WT, altered osteoblast morphology and decreased tissue synthesis of alkaline phosphatase in Mecp2-null and HET mice. Osteoblasts cultured from Mecp2-null mice, which unlike WT osteoblasts did not express MeCP2, had increased growth rates, but reductions in mRNA expression of type I collagen, Runx2 and Osterix compared to WT osteoblasts. These results indicate that MeCP2 deficiency leads to altered bone growth. Osteoblast dysfunction was more marked in Mecp2-null null male than in HET female mice, suggesting that expression of MeCP2 plays a critical role in bone development.

Link To Article

http://dx.doi.org/10.1016/j.bone.2015.01.024

Pharmacological inhibition of ​Dock5 prevents osteolysis by affecting osteoclast podosome organization while preserving bone formation

Authors

Virginie Vives, Gaëlle Cres, Christian Richard, Muriel Busson, Yann Ferrandez, Anne-Gaelle Planson, Mahel Zeghouf, Jacqueline Cherfils, Luc Malaval & Anne Blangy

Abstract

Osteoporosis is caused by excessive activity of bone-degrading osteoclasts over bone-forming osteoblast. Standard antiosteolytic treatments inhibit bone resorption by inducing osteoclast loss, with the adverse effect of hindering also bone formation. Formation of the osteoclast sealing zone requires ock5, a guanine nucleotide exchange factor for the small GTPase Rac, and 21, a chemical inhibitor of ock5, decreases bone resorption by cultured osteoclasts. Here we show that 21 directly inhibits the exchange activity of ock5 and disrupts osteoclast podosome organization. Remarkably, 21 administration protects mice against bone degradation in models recapitulating major osteolytic diseases: menopause, rheumatoid arthritis and bone metastasis. Furthermore, 21 administration does not affect bone formation and is not toxic. Our results validate the pharmacological inhibition of ock5 as a novel therapeutic route for fighting osteolytic diseases while preserving bone formation.

Link To Article

http://dx.doi.org/10.1038/ncomms7218

A novel therapeutic approach with Caviunin-based isoflavonoid that en routes bone marrow cells to bone formation via BMP2/Wnt-β-catenin signaling

Authors

P Kushwaha, V Khedgikar, J Gautam, P Dixit, R Chillara, A Verma, R Thakur, D P Mishra, D Singh, R Maurya, N Chattopadhyay, P R Mishra and R Trivedi

Abstract

Recently, we reported that extract of Dalbergia sissoo made from leaves and pods have antiresorptive and bone-forming effects. The positive skeletal effect attributed because of active molecules present in the extract of Dalbergia sissoo. Caviunin 7-O-[β-d-apiofuranosyl-(1-6)-β-d-glucopyranoside] (CAFG), a novel isoflavonoid show higher percentage present in the extract. Here, we show the osteogenic potential of CAFG as an alternative for anabolic therapy for the treatment of osteoporosis by stimulating bone morphogenetic protein 2 (BMP2) and Wnt/β-catenin mechanism. CAFG supplementation improved trabecular micro-architecture of the long bones, increased biomechanical strength parameters of the vertebra and femur and decreased bone turnover markers better than genistein. Oral administration of CAFG to osteopenic ovariectomized mice increased osteoprogenitor cells in the bone marrow and increased the expression of osteogenic genes in femur and show new bone formation without uterine hyperplasia. CAFG increased mRNA expression of osteoprotegerin in bone and inhibited osteoclast activation by inhibiting the expression of skeletal osteoclastogenic genes. CAFG is also an effective accelerant for chondrogenesis and has stimulatory effect on the repair of cortical bone after drill-hole injury at the tissue, cell and gene level in mouse femur. At cellular levels, CAFG stimulated osteoblast proliferation, survival and differentiation. Signal transduction inhibitors in osteoblast demonstrated involvement of p-38 mitogen-activated protein kinase pathway stimulated by BMP2 to initiate Wnt/β-catenin signaling to reduce phosphorylation of GSK3-β and subsequent nuclear accumulation of β-catenin. Osteogenic effects were abrogated by Dkk1, Wnt-receptor blocker and FH535, inhibitor of TCF-complex by reduction in β-catenin levels. CAFG modulated MSC responsiveness to BMP2, which promoted osteoblast differentiation via Wnt/β-catenin mechanism. CAFG at 1 mg/kg/day dose in ovariectomy mice (human dose ~0.081 mg/kg) led to enhanced bone formation, reduced bone resorption and bone turnover better than well-known phytoestrogen genistein. Owing to CAFG’s inherent properties for bone, it could be positioned as a potential drug, food supplement, for postmenopausal osteoporosis and fracture repair.

Link To Article

http://dx.doi.org/10.1038/cddis.2014.350

Absence of Dap12 and the αvβ3 integrin causes severe osteopetrosis

Authors

Wei Zou and Steven L. Teitelbaum

Abstract

In vitro, ligand occupancy of αvβ3 integrin induces phosphorylation of Dap12, which is essential for osteoclast function. Like mice deleted of only αvβ3, Dap12−/− mice exhibited a slight increase in bone mass, but Dap12−/− mice, lacking another ITAM protein, FcRγ, were severely osteopetrotic. The mechanism by which FcRγ compensates for Dap12 deficiency is unknown. We find that co-deletion of FcRγ did not exacerbate the skeletal phenotype of β3−/− mice. In contrast, β3/Dap12 double-deficient (DAP/β3−/−) mice (but not β1/Dap12 double-deficient mice) were profoundly osteopetrotic, reflecting severe osteoclast dysfunction relative to those lacking αvβ3 or Dap12 alone. Activation of OSCAR, the FcRγ co-receptor, rescued Dap12−/− but not DAP/β3−/−osteoclasts. Thus, the absence of αvβ3 precluded compensation for Dap12 deficiency by FcRγ. In keeping with this, Syk phosphorylation did not occur in OSCAR-activated DAP/β3−/− osteoclasts. Thus, FcRγ requires the osteoclast αvβ3 integrin to normalize the Dap12-deficient skeleton.

μCT-based, in vivo dynamic bone histomorphometry allows 3D evaluation of the early responses of bone resorption and formation to PTH and alendronate combination therapy

Authors

Chantal M.J. de Bakker, Allison R. Altman, Wei-Ju Tseng, Mary Beth Tribble, Connie Li, Abhishek Chandra, Ling Qin, X. Sherry Liu

Abstract

Current osteoporosis treatments improve bone mass by increasing net bone formation: anti-resorptive drugs such as bisphosphonates block osteoclast activity, while anabolic agents such as parathyroid hormone (PTH) increase bone remodeling, with a greater effect on formation. Although these drugs are widely used, their role in modulating formation and resorption is not fully understood, due in part to technical limitations in the ability to longitudinally assess bone remodeling. Importantly, it is not known whether or not PTH-induced bone formation is independent of resorption, resulting in controversy over the effectiveness of combination therapies that use both PTH and an anti-resorptive. In this study, we developed a μCT-based, in vivo dynamic bone histomorphometry technique for rat tibiae, and applied this method to longitudinally track changes in bone resorption and formation as a result of treatment with alendronate (ALN), PTH, or combination therapy of both PTH and ALN (PTH + ALN). Correlations between our μCT-based measures of bone formation and measures of bone formation based on calcein-labeled histology (r = 0.72–0.83) confirm the accuracy of this method. Bone remodeling parameters measured through μCT-based in vivo dynamic bone histomorphometry indicate an increased rate of bone formation in rats treated with PTH and PTH + ALN, together with a decrease in bone resorption measures in rats treated with ALN and PTH + ALN. These results were further supported by traditional histology-based measurements, suggesting that PTH was able to induce bone formation while bone resorption was suppressed.

Link To Article

http://dx.doi.org/10.1016/j.bone.2014.12.061