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

Effects of bovine lactoferrin in surgically created bone defects on bone regeneration around implants

Authors

Ulaş Görmez, Mehmet Kürkcü, Mehmet E. Benlidayi, Kezban Ulubayram, Yaşar Sertdemir, Kenan Dağlioğlu

Abstract

The aim of this experimental study was to evaluate the effect of bovine lactoferrin (bLF)-loaded gelatin microspheres (GM) used in combination with anorganic bovine bone on bone regeneration in surgically created bone defects around tooth implants. Twenty-four uniform bone defects were created in the frontal bone via an extraoral approach in 12 domestic pigs. Twenty-four implants were placed at the center of the defects. In eight animals one of these defects was filled with 0.3 mL anorganic bovine bone while the other was left empty. In four animals, all defects were filled with 3 mg/defect bLF-loaded GM and anorganic bovine bone. All the defects were covered with collagen membranes. All animals were sacrificed after 10 weeks of healing, and the implants with the surrounding bone defects were removed en bloc. Undecalcified sections were prepared for histomorphometric analysis. The mean total area of hard tissue was 26.9 ± 6.0% in the empty defect group, 31.8 ± 8.4% in the graft group, and 47.6 ± 5.0% in the lactoferrin group (P < 0.001). The mean area of newly formed bone was 26.9 ± 6.0% in the empty defect group, 22.4 ± 8.2% in the graft group, and 46.1 ± 5.1% in the lactoferrin group (P < 0.001). The mean residual graft area was 9.4 ± 3.2% in the graft group and 1.5 ± 0.6% in the lactoferrin group (P < 0.001). The mean proportion of bone-implant contact in the defect region was 21.9 ± 8.4% in the empty defect group, 26.9 ± 10.1% in the graft group and 29.9 ± 10.3% in the lactoferrin group (P = 0.143). These data indicate that a combination of 3 mg bLF-loaded GM and bovine-derived HA promotes bone regeneration in defects around implants.

Link To Article

http://dx.doi.org/10.2334/josnusd.57.7

Odanacatib restores trabecular bone of skeletally mature female rabbits with osteopenia but induces brittleness of cortical bone...

Title

Odanacatib restores trabecular bone of skeletally mature female rabbits with osteopenia but induces brittleness of cortical bone: a comparative study of the investigational drug with PTH, Estrogen and Alendronate

Authors

Mohd. Parvez Khan M.Sc., Atul Kumar Singh M.Tech., Abhishek Kumar Singh M.Sc., Pragya Shrivastava M.Sc., Mahesh Chandra Tiwari M.Sc., Geet Kumar Nagar B.Sc., Himangshu Kousik Bora M.V.Sc., Venkitanarayanan Parameswaran PhD, Sabyasachi Sanyal PhD, Jayesh R. Bellare PhD, and Naibedya Chattopadhyay PhD

Abstract

Cathepsin K (CK), a lysosomal cysteine protease is highly expressed in mature osteoclasts and degrades type 1 collagen. Odanacatib (ODN) is a selective and reversible CK inhibitor that inhibits bone loss in preclinical and clinical studies. Although an anti-resorptive, ODN, does not suppress bone formation which led us to hypothesize that ODN may display restorative effect on the osteopenic bones. In a curative study, skeletally mature New Zealand rabbits were OVX and following induction of bone loss were given a steady-state exposure of ODN (9μM/day) for 14 weeks. Sham operated and OVX rabbits treated with alendronate (ALD), 17β-estradiol (E2) or PTH served as various controls. Efficacy was evaluated by assessing BMD, bone microarchitecture (using microcomputed tomography), fluorescent labeling of bone and biomechanical strength. Skeletal Ca/P ratio was measured by scanning electron microscopy (SEM) with X-ray microanalysis, crystallinity by X-ray diffraction, and bone mineral density distribution (tissue mineralization) by backscattered SEM. Between the sham and ODN-treated osteopenic groups, lumbar and femur metaphyseal BMD, Ca/P ratio, trabecular microstructure and geometric indices, vertebral compressive strength, trabecular lining cells, cortical parameters (femoral BMD, area and thickness, and periosteal deposition) and serum P1NP were largely comparable. Skeletal improvements in ALD or E2-treated groups fell significantly short of the sham/ODN/PTH group. However, the ODN group displayed reduced ductility and enhanced brittleness of central femur, which might have been contributed by higher crytallinity and tissue mineralization. Rabbit bone marrow stromal cells expressed CK and when treated with ODN displayed increased formation of mineralized nodules and decreased apoptosis in serum-deficient medium compared with control. In vivo, ODN did not suppress remodeling but inhibited osteoclast activity more than ALD. Taken together, we show that ODN reverses BMD, skeletal architecture and compressive strength in osteopenic rabbits however, increases crystallinity and tissue mineralization thus leading to increased cortical bone brittleness.

Link To Article

http://dx.doi.org/10.1002/jbmr.2520

Effects of blockade of endogenous Gi signaling in Tie2+-expressing cells on bone formation in a mouse model of heterotopic ossification

Authors

Liping Wang, Dylan O'Carroll, Xuhui Liu, Theresa Roth, Hubert Kim, Bernard Halloran and Robert A. Nissenson

Abstract

Available evidence indicates that some Tie2-expressing (Tie2+) cells serve as multipotent progenitors that have robust BMP-dependent osteogenic activity and mediate heterotopic ossification (HO). Since signaling through the G protein Gi is required for cell motility, we hypothesized that blockade of endogenous Gi signaling in Tie2+ cell populations would prevent HO formation. Blockade of Gi signaling in Tie2+ cells was accomplished in transgenic mice with expression of pertussis toxin (PTX) under the control of the Tie2 promoter (Tie2+/PTX+). Bone formation within HOs was evaluated 2 weeks after BMP injection. Expression of PTX in Tie2+ cells significantly reduced the bone volume (BV) of HOs in male and female mice. Orthotopic bones were assessed at the distal femur and expression of PTX significantly increased trabecular bone fractional volume and bone formation rate in females only. In adult Tie2+/GFP+ mice, GFP+ cells appeared both inside and at the surfaces of bone tissue within HOs and in orthotopic bones. In summary, blockade of Gi signaling in Tie2+ cells reduced the accrual of HOs and stimulated osteogenesis in orthotopic bones. Targeting of Gi protein coupled receptors in Tie2+ cells may be a novel therapeutic strategy in states of abnormal bone formation such as osteoporosis and HO.

Link To Article

http://dx.doi.org/10.1002/jor.22876

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

A delivery system specifically approaching bone resorption surfaces to facilitate therapeutic modulation of microRNAs in osteoclasts

Authors

Jin Liu, Lei Dang, Defang Li, Chao Liang, Xiaojuan He, Heng Wua, Airong Qiane, Zhijun Yanga, Doris W.T. Au, Michael W.L. Chiang, Bao-Ting Zhani, Quanbin Han, Kevin K.M. Yuea, Hongqi Zhang, Changwei Lv, Xiaohua Pan, Jiake Xu, Zhaoxiang Bian, Peng Shang, Weihong Tan, Zicai Liang, Baosheng Guo, Aiping Lu, Ge Zhang

Abstract

Dysregulated microRNAs in osteoclasts could cause many skeletal diseases. The therapeutic manipulation of these pathogenic microRNAs necessitates novel, efficient delivery systems to facilitate microRNAs modulators targeting osteoclasts with minimal off-target effects. Bone resorption surfaces characterized by highly crystallized hydroxyapatite are dominantly occupied by osteoclasts. Considering that the eight repeating sequences of aspartate (D-Asp8) could preferably bind to highly crystallized hydroxyapatite, we developed a targeting system by conjugating D-Asp8 peptide with liposome for delivering microRNA modulators specifically to bone resorption surfaces and subsequently encapsulated antagomir-148a (a microRNA modulator suppressing the osteoclastogenic miR-148a), i.e. (D-Asp8)-liposome-antagomir-148a. Our results demonstrated that D-Asp8 could facilitate the enrichment of antagomir-148a and the subsequent down-regulation of miR-148a in osteoclasts in vivo, resulting in reduced bone resorption and attenuated deterioration of trabecular architecture in osteoporotic mice. Mechanistically, the osteoclast-targeted delivery depended on the interaction between bone resorption surfaces and D-Asp8. No detectable liver and kidney toxicity was found in mice after single/multiple dose(s) treatment of (D-Asp8)-liposome-antagomir-148a. These results indicated that (D-Asp8)-liposome as a promising osteoclast-targeting delivery system could facilitate clinical translation of microRNA modulators in treating those osteoclast-dysfunction-induced skeletal diseases.

Link To Article

http://dx.doi.org/10.1016/j.biomaterials.2015.02.007