Odanacatib reduces bone turnover and increases bone mass in the lumbar spine of skeletally mature ovariectomized rhesus monkeys

Authors

P.J. Masarachia1, B.L. Pennypacker1, M. Pickarski1, K.R. Scott1, G.A. Wesolowski1, S.Y. Smith3, R. Samadfam3, J.E. Goetzmann4, B.B. Scott2, D.B. Kimmel1, L.T. Duong

Abstract

Odanacatib (ODN) is a selective and reversible inhibitor of cathepsin K (CatK) currently being developed as a once-weekly treatment for osteoporosis. In this study, we evaluated the effects of ODN on bone turnover, bone mineral density (BMD), and bone strength in the lumbar spine of estrogen deficient, skeletally mature, rhesus monkeys. Ovariectomized (OVX)-monkeys were treated in prevention mode for 21-months with either vehicle, ODN 6mg/kg or ODN 30mg/kg (p.o., q.d.) and compared to intact animals. ODN treatment persistently suppressed the bone resorption markers, urinary NTx (75-90%), serum CTx (40-55%), the serum formation markers, BSAP (30-35%) and P1NP (60-70%) versus vehicle-treated OVX-monkeys. Treatment with ODN also led to dose-dependent increases in serum 1-CTP, and maintained estrogen deficiency-elevated Trap-5b levels, supporting the distinct mechanism of CatK inhibition in effectively suppressing bone resorption without reducing osteoclast numbers. ODN at both doses fully prevented bone loss in lumbar vertebrae (LV1-4) BMD in OVX-animals maintaining a level comparable to intact animals. ODN dose-dependently increased LV1-4 BMD by 7% in the 6mg/kg (p < 0.05 vs. OVX-vehicle) and 15% in the 30mg/kg group (p < 0.05 vs. OVX-vehicle) from baseline. Treatment also trended to increase bone strength, associated with a positive and highly significant correlation (R = 0.838) between peak load and bone mineral content of the lumbar spine. While ODN reduced bone turnover parameters in trabecular bone, the number of osteoclasts was either maintained or increased in the ODN-treated groups compared to the vehicle controls. Taken together, our findings demonstrated that the long-term treatment with ODN effectively suppressed bone turnover without reducing osteoclast number and maintained normal biomechanical properties of the spine of OVX-non human primates.

Link to Article

http://dx.doi.oirg/10.1002/jbmr.1475

Femoral metaphysis bending test of rat: introduction and validation of a novel biomechanical testing protocol for osteoporosis

Authors

BaiLing Chen, YiQiang Li, XiaoXi Yang and DengHui Xie

Abstract

The diaphysis bending test is generally accepted to assess the biomechanical properties of bone in osteoporotic animals. However, bone strength loss was more pronounced at the metaphysis than diaphysis. Therefore, the biomechanical test should be focused on the metaphysis. This study aimed to validate a novel biomechanical test for femoral metaphysis in ovariectomized rats. Twenty 5-month-old female Sprague-Dawley rats were randomly divided into the ovariectomized (OVX) and sham-operated (Sham) groups. Examination of femur bone mineral density (BMD) and histomorphometry of the distal femur were performed. Femur biomechanical parameters (maximal load, yield load, and stiffness) were determined by the diaphysis bending test and a novel designed metaphysis bending test. Pearson's correlations were used to analyze the relationships between the biomechanical parameters and BMD or bone histomorphometry indexes (%Tb.Ar, Tb.N, Tb.Th), respectively. The femur BMD, bone histomorphometry indexes, and biomechanical parameters of OVX were inferior to those of the Sham group (P < 0.05). In the diaphysis bending test, the mean difference of the maximum load and yield load between the OVX and Sham groups were 13.83 ± 5.27 and 15.69 ± 4.15 N, which were significantly lower than in the metaphysis bending test (43.34 ± 4.27, 48.90 ± 4.35 N; all P < 0.05). Positive correlations between biomechanical parameters and femur BMD or bone histomorphometry indexes were observed in both the diaphysis bending and metaphysis bending test. The biomechanical parameters in the metaphysis bending test showed stronger correlations with BMD and bone histomorphometry indexes. The femoral metaphysis bending test was validated to assess osteoporosis in our study, and it was more sensitive than the diaphysis bending test in evaluating the change of biomechanical properties of the femur in osteoporotic rats.

Link to Article

http://dx.doi.org/10.1007/s00776-011-0167-7

Topically administered Risedronate shows powerful anti-osteoporosis effect in ovariectomized mouse model

Authors

So Hee Nam, Jae-Hwan Jeong, Xiangguo Che, Kyung-Eun Lim, Hyemi Nam, Jong-Sang Park, Je-Yong Choi

Abstract

We investigated the therapeutic effect of topical Risedronate (RIS) on a mouse model of estrogen-deficient osteoporosis. Fourteen-week-old female mice were ovariectomized and assigned to 4 groups: SHAM-operated (SHAM), OVX mice treated with vehicle (OVX-V), OVX mice treated with 0.2% RIS (OVX-0.2% RIS), and OVX-mice treated with 0.02% RIS (OVX-0.02% RIS). Topical samples containing RIS were prepared in 10% (w/w) polyethylene glycol (PEG, MW 400) and 80 μg of sample was spread on the mice's mid-backs every 3 days for 5 weeks. Micro-CT analysis of femora demonstrated that OVX-0.2% RIS exhibited a 29% greater bone mineral density and 24% greater bone volume fraction than that of OVX-V group. Investigation of the trabecular bone in OVX-0.2% RIS revealed a 24% higher bone volume (BV/TV), 51% higher trabecular number (Tb.N), and 40% lower trabecular separation (Tb.Sp) compared to OVX-V mice. Additionally, bone phenotypes of tibiae were further confirmed by histological analysis. OVX-0.2% RIS group exhibited a 494% greater BV/TV, 464% less Tb.Sp, 81% greater active osteoclast surface (Oc.S/BS) and 26% less osteoclast number (N.Oc/BS) than that of OVX-V group. Collectively, these results indicated that topical delivery of RIS has powerful pharmaceutical effects on the prevention of osteoporosis and bone turnover.

Link to Article

http://dx.doi.org/10.1016/j.bone.2011.10.017

Corticosterone selectively targets endo-cortical surfaces by an osteoblast-dependent mechanism

Authors

Holger Henneicke, Markus Herrmann, Robert Kalak, Tara C. Brennan-Speranza, Uta Heinevetter, Nicky Bertollo, Robert E. Day, Dörte Huscher, Frank Buttgereit, Colin R. Dunstan, Markus J. Seibel, and Hong Zhou

Abstract

The pathogenesis of glucocorticoid-induced osteoporosis remains ill defined. In this study, we examined the role of the osteoblast in mediating the effects of exogenous glucocorticoids on cortical and trabecular bone, employing the Col2.3-11βHSD2 transgenic mouse model of osteoblast-targeted disruption of glucocorticoid signalling. Eight week-old male transgenic (tg) and wild-type (WT) mice (n = 20–23/group) were treated with either 1.5 mg corticosterone (CS) or placebo for 4 weeks. Serum tartrate-resistant acid phosphatase 5b (TRAP5b) and osteocalcin (OCN) were measured throughout the study. Tibiae and lumbar vertebrae were analysed by micro-CT and histomorphometry at endpoint. CS suppressed serum OCN levels in WT and tg mice, although they remained higher in tg animals at all time points (p < 0.05). Serum TRAP5b levels increased in WT mice only. The effect of CS on cortical bone differed by site: At the endosteal surface, exposure to CS significantly increased bone resorption and reduced bone formation, resulting in a larger bone marrow cavity cross-sectional area (p < 0.01). In contrast, at the pericortical surface bone resorption was significantly decreased accompanied with a significant increase in pericortical cross-sectional area (p < 0.05) while bone formation remained unaffected. Vertebral cortical thickness and area were reduced in CS treatment mice. Tg mice were partially protected from the effects of exogenous CS, both on a cellular and structural level. At the CS doses used in this study, trabecular bone remained largely unaffected. Endocortical osteoblasts appear to be particularly sensitive to the detrimental actions of exogenous glucocorticoids. The increase in tibial pericortical cross-sectional area and the according changes in pericortical circumference suggest an anabolic bone response to GC treatment at this site. The protection of tg mice from these effects indicates that both catabolic and anabolic action of glucocorticoids are, at least in part, mediated by osteoblasts.

Link to Article

http://dx.doi.org/10.1016/j.bone.2011.06.013

Trabecular bone microstructure and local gene expression in iliac crest biopsies of men with idiopathic osteoporosis

Authors

Janina M Patsch, Thomas Kohler, Andrea Berzlanovich, Christian Muschitz, Christian Bieglmayr, Paul Roschger, Heinrich Resch, Peter Pietschmann

Abstract

Male idiopathic osteoporosis (MIO) is a metabolic bone disease that is characterized by low bone mass, microstructural alterations, and increased fracture risk in otherwise healthy men. Although the detailed pathophysiology of MIO has yet to be clarified, evidence increasingly suggests an osteoblastic defect as the underlying cause. In this study we tested the hypothesis that the expression profile of certain osteoblastic or osteoblast-related genes (ie, WNT10B, RUNX2, Osterix, Osteocalcin, SOST, RANKL, and OPG) is different in iliac crest biopsies of MIO patients when compared with healthy controls. Furthermore, we investigated the relation of local gene expression characteristics with histomorphometric, microstructural, and clinical features. Following written informed consent and diligent clinical patient characterization, iliac crest biopsies were performed in nine men. While RNA extraction, reverse-transcription, and real-time polymerase chain reactions (PCRs) were performed on one biopsy, a second biopsy of each patient was submitted for histomorphometry and micro–computed tomography (µCT). Age-matched bone samples from forensic autopsies served as controls. MIO patients displayed significantly reduced WNT10B, RUNX2, RANKL, and SOST expression. Performing µCT for the first time in MIO biopsies, we found significant decreases in trabecular number and connectivity density. Trabecular separation was increased significantly, but trabecular thickness was similar in both groups. Histomorphometry revealed decreased BV/TV and osteoid volume and fewer osteoclasts in MIO. By providing evidence for reduced local WNT10B, RUNX2, and RANKL gene expression and histomorphometric low turnover, our data support the osteoblast dysfunction model discussed for MIO. Further, MIO seems to lead to a different microstructural pathology than age-related bone loss.

Link to Article

http://dx.doi.org/10.1002/jbmr.344

Differential maintenance of cortical and cancellous bone strength following discontinuation of bone-active agents

Authors

Mohammad Shahnazari, Wei Yao, Bob Wang, Brian Panganiban, Robert Ritchie, Yolanda Hagar, Nancy E Lane

Abstract

Osteoporotic patients treated with antiresorptive or anabolic agents experience an increase in bone mass and a reduction in incident fractures. However, the effects of these medications on bone quality and strength after a prolonged discontinuation of treatment are not known. We evaluated these effects in an osteoporotic rat model. Six-month-old ovariectomized (OVX) rats were treated with placebo, alendronate (ALN, 2 µg/kg), parathyroid hormone [PTH(1–34); 20 µg/kg], or raloxifene (RAL, 2 mg/kg) three times a week for 4 months and withdrawn from the treatments for 8 months. Treatment with ALN, PTH, and RAL increased the vertebral trabecular bone volume (BV/TV) by 47%, 53%, and 31%, with corresponding increases in vertebral compression load by 27%, 51%, and 31%, respectively (p < .001). The resulting bone strength was similar to that of the sham-OVX control group with ALN and RAL and higher (p < .001) with PTH treatment. After 4 months of withdrawal, bone turnover (BFR/BS) remained suppressed in the ALN group versus the OVX controls (p < .001). The vertebral strength was higher than in the OVX group only in ALN-treated group (p < .05), whereas only the PTH-treated animals showed a higher maximum load in tibial bending versus the OVX controls (p < .05). The vertebral BV/TV returned to the OVX group level in both the PTH and RAL groups 4 months after withdrawal but remained 25% higher than the OVX controls up to 8 months after withdrawal of ALN (p < .05). Interestingly, cortical bone mineral density increased only with PTH treatment (p < .05) but was not different among the experimental groups after withdrawal. At 8 months after treatment withdrawal, none of the treatment groups was different from the OVX control group for cortical or cancellous bone strength. In summary, both ALN and PTH maintained bone strength (maximum load) 4 months after discontinuation of treatment despite changes in bone mass and bone turnover; however, PTH maintained cortical bone strength, whereas ALN maintained cancellous bone strength. Additional studies on the long-term effects on bone strength after discontinuation and with combination of osteoporosis medications are needed to improve our treatment of osteoporosis.

Link to Article

http://dx.doi.org/10.1002/jbmr.249