Discretizing low-intensity whole-body vibration into bouts with short rest intervals promotes bone defect repair in osteoporotic mice

Continuous administration of low-intensity whole-body vibration (WBV) gradually diminishes bone mechanosensitivity over time, leading to a weakening of its osteogenic effect. We investigated whether discretizing WBV into bouts with short rest intervals was effective in enhancing osteoporotic bone repair. Ten-week-old female mice were ovariectomized and underwent drill-hole defect surgery (Day 0) on the right tibial diaphysis at 11 weeks of age. The mice underwent one of three regimens starting from Day 1 for 5 days/week: continuous WBV at 45 Hz and 0.3 g for 7.5 min/day (cWBV); 3-s bouts of WBV at 45 Hz, 0.3 g followed by 9-s rest intervals, repeated for 30 min/day (repeated bouts of whole-body vibration with short rest intervals [rWBV]); or a sham treatment. Both the cWBV and rWBV groups received a total of 20,250 vibration cycles per day. On either Day 7 or 14 posteuthanasia (n = 6/group/timepoint), the bone and angiogenic vasculature in the defect were computed tomography imaged using synchrotron light. By Day 14, the bone repair was most advanced in the rWBV group, showing a higher bone volume fraction and a more uniform mineral distribution compared with the sham group. The cWBV group exhibited an intermediate level of bone repair between the sham and rWBV groups. The rWBV group had a decrease in large-sized angiogenic vessels, while the cWBV group showed an increase in such vessels. In conclusion, osteoporotic bone repair was enhanced by WBV bouts with short rest intervals, which may potentially be attributed to the improved mechanosensitivity of osteogenic cells and alterations in angiogenic vasculature.

Combined effect of teriparatide and an anti-RANKL monoclonal antibody on bone defect regeneration in mice with glucocorticoid-induced osteoporosis

OBJECTIVE

The purpose of this study was to examine the effect of single or combination therapy of teriparatide (TPTD) and a monoclonal antibody against the murine receptor activator of nuclear factor κB ligand (anti-RANKL Ab) on cancellous and cortical bone regeneration in a mouse model of glucocorticoid-induced osteoporosis (GIOP).

METHODS

C57BL/6 J mice (24 weeks of age) were divided into five groups: (1) the SHAM group: sham operation + saline; (2) the prednisolone (PSL) group: PSL + saline; (3) the TPTD group: PSL + TPTD; (4) the Ab group: PSL + anti-RANKL Ab; and (5) the COMB group: PSL + TPTD + anti-RANKL Ab (n = 8 per group). With the exception of the SHAM group, 7.5 mg of PSL was inserted subcutaneously into mice, to generate a mouse model of GIOP. Four weeks after insertion, bone defects with a diameter of 0.9 mm were created to assess bone regeneration on both femoral metaphysis (cancellous bone) and diaphysis (cortical bone). After surgery, therapeutic intervention was continued for 4 weeks. Saline (200 μl) or TPTD (40 μg/kg) was injected subcutaneously five times per week, whereas the anti-RANKL Ab (5 mg/kg) was injected subcutaneously once on the day after surgery. Subsequently, the following analyses were performed: microstructural assessment of bone regeneration and bone mineral density (BMD) measurement via micro-computed tomography, and histological, histomorphometrical, and biomechanical analyses with nanoindentation.

RESULTS

The COMB group showed the highest lumbar spine BMD increase (vs. the PSL, TPTD, and Ab groups). The volume of regenerated cancellous bone at the bone defect site was higher in the COMB group compared with the PSL, TPTD, and Ab group. The volume of the regenerated cortical bone was significantly higher in the COMB group compared with the PSL group, and its hardness was significantly higher in the COMB group compared with the PSL and TPTD groups.

CONCLUSION

In a mouse model of glucocorticoid-induced osteoporosis, the combination therapy of TPTD plus the anti-RANKL Ab increased bone mineral density in the lumbar spine and regenerated cancellous bone volume compared with single administration of each agent, and also increased regenerated cortical bone strength compared with single administration of TPTD.

The combined effect of Parathyroid hormone (1-34) and whole-body Vibration exercise in the treatment of postmenopausal OSteoporosis (PaVOS study): a randomized controlled trial

Treatment effects of combining teriparatide and whole-body vibration exercise (WBV) vs teriparatide alone in twelve months were compared using bone mineral density (BMD), bone microarchitecture, and bone turnover markers. We found an increased effect in lumbar spine BMD by adding WBV to teriparatide in postmenopausal osteoporotic women.

INTRODUCTION

The parathyroid hormone (PTH) analogue teriparatide is an effective but expensive anabolic treatment for osteoporosis. Whole-body vibration exercise (WBV) has been found to stimulate muscle and bone strength in some studies. Animal data demonstrate a beneficial effect on bone when combining PTH with mechanical loading. The aim of this study was to investigate if combining WBV exercise and teriparatide treatment gives additional beneficial effects on bone compared to teriparatide alone in postmenopausal women with osteoporosis.

METHODS

The PaVOS study is a randomized controlled trial where postmenopausal osteoporotic women starting teriparatide 20 μg/day were randomized to WBV + teriparatide or teriparatide alone. WBV consisted of three sessions a week (12 min, including 1:1 ratio of exercise:rest). Bone mineral density (BMD) and bone microarchitecture, bone turnover markers, and sclerostin measurements were obtained. Data were analyzed using a linear mixed regression model with adjustment for baseline values or robust cluster regression in an intention-to-treat (ITT) analysis.

RESULTS

Thirty-five women were randomized (17 in teriparatide + WBV group and 18 in teriparatide group). At 12 months, both groups increased significantly in BMD at the lumbar spine. The teriparatide + WBV group increased by (mean ± SD) 8.90% ± 5.47 and the teriparatide group by 6.65% ± 5.51. The adjusted treatment effect of adding WBV to teriparatide was statistically significant at 2.95% [95% CI = 0.14-5.77; P = 0.040]. Markers of bone turnover increased significantly in both groups at three and six months with no significant difference between groups. No other treatment effects were observed in hip BMD, bone microarchitecture parameters, or sclerostin levels in either group.

CONCLUSION

Twelve months of WBV and teriparatide had a significant clinically relevant treatment effect in lumbar spine BMD compared to teriparatide alone in postmenopausal osteoporotic women. ClinicalTrials.gov :(NCT02563353).

Exploring conditions that make cortical bone geometry optimal for physiological loading

While physiological loading on lower long bones changes during bone development, the bone cross section either remains circular or slowly changes from nearly circular to other shapes such as oval and roughly triangular. Bone is said to be an optimal structure, where strength is maximized using the optimal distribution of bone mass (also called Wolff's law). One of the most appropriate mathematical validations of this law would be a structural optimization-based formulation where total strain energy is minimized against a mass and a space constraint. Assuming that the change in cross section during bone development and homeostasis after adulthood is direct result of the change in physiological loading, this work investigates what optimization problem formulation (collectively, design variables, objective function, constraints, loading conditions, etc.) results in mathematically optimal solutions that resemble bones under actual physiological loading. For this purpose, an advanced structural optimization-based computational model for cortical bone development and defect repair is presented. In the optimization problem, overall bone stiffness is maximized first against a mass constraint, and then also against a polar first moment of area constraint that simultaneously constrains both mass and space. The investigation is completed in two stages. The first stage is developmental stage when physiological loading on lower long bones (tibia) is a random combination of axial, bending and torsion. The topology optimization applied to this case with the area moment constraint results into circular and elliptical cross sections similar to that found in growing mouse or human. The second investigation stage is bone homeostasis reached in adulthood when the physiological loading has a fixed pattern. A drill hole defect is applied to the adult mouse bone, which would disrupt the homeostasis. The optimization applied after the defect interestingly brings the damaged section back to the original intact geometry. The results, however, show that cortical bone geometry is optimal for the physiological loading only when there is also a constraint on polar moment of area. Further numerical experiments show that application of torsion along with the gait-analysis-based physiological loading improves the results, which seems to indicate that the cortical bone geometry is optimal for some amount of torsion in addition to the gait-based physiological loading. This work has a potential to be extended to bone growth/development models and fracture healing models, where topology optimization and polar moment of area constraint have not been introduced earlier.

Preclinical therapies to prevent or treat fracture non-union: A systematic review

Background

Non-union affects up to 10% of fractures and is associated with substantial morbidity. There is currently no single effective therapy for the treatment or prevention of non-union. Potential treatments are currently selected for clinical trials based on results from limited animal studies, with no attempt to compare results between therapies to determine which have the greatest potential to treat non-union.

Aim

The aim of this systematic review was to define the range of therapies under investigation at the preclinical stage for the prevention or treatment of fracture non-union. Additionally, through meta-analysis, it aimed to identify the most promising therapies for progression to clinical investigation.

Methods

MEDLINE and Embase were searched from 1^St January 2004 to 10^th April 2017 for controlled trials evaluating an intervention to prevent or treat fracture non-union. Data regarding the model used, study intervention and outcome measures were extracted, and risk of bias assessed.

Results

Of 5,171 records identified, 197 papers describing 204 therapies were included. Of these, the majority were only evaluated once (179/204, 88%), with chitosan tested most commonly (6/204, 3%). Substantial variation existed in model design, length of survival and duration of treatment, with results poorly reported. These factors, as well as a lack of consistently used objective outcome measures, precluded meta-analysis.

Conclusion

This review highlights the variability and poor methodological reporting of current non-union research. The authors call for a consensus on the standardisation of animal models investigating non-union, and suggest journals apply stringent criteria when considering animal work for publication.

The combined effect of Parathyroid hormone (1-34) and whole-body Vibration exercise in the treatment of OSteoporosis (PaVOS)- study protocol for a randomized controlled trial

BACKGROUND

PaVOS is a randomized controlled trial (RCT) which aims to address the use of whole-body vibration exercise (WBV) in combination with parathyroid hormone 1-34 fragment teriparatide (PTH 1-34) treatment in patients with osteoporosis. PTH 1-34 is an effective but expensive anabolic treatment for osteoporosis. WBV has been found to stimulate muscle and bone growth. Animal studies have shown a beneficial effect on bone when combining PTH 1-34 with mechanical loading. A combined treatment with PTH 1-34 and WBV may potentially have beneficial effects on bone and muscles, and reduce fracture risk.

METHODS/DESIGN

PaVOS is a multicenter, assessor-blinded, superiority, two-armed randomized controlled trial (RCT). Postmenopausal women (n = 40, aged 50 years and older) starting taking PTH 1-34 from outpatient clinics will be randomized and assigned to a PTH 1-34 + WBV-exercise group (intervention group), or a PTH 1-34-alone group (control group). The intervention group will undergo WBV three sessions a week (12 min each, including 1:1 ratio of exercise: rest, 30 Hz, 1 mm amplitude) for a 12-month intervention period. Both the intervention and the control group will receive PTH 1-34 treatment (20 μg s.c. daily) for 24 months. After 12 months the WBV group will be re-randomized to stop or continue WBV for an additional 12 months. The primary endpoint, bone mineral density (BMD), will be measured by dual-energy x-ray absorptiometry of the total hip and the lumbar spine. Secondary endpoints, bone microarchitecture and estimated bone strength, will be assessed using high-resolution peripheral quantitative computed tomography (HR-pQCT) of the radius and tibia. Serum bone turnover markers (carboxy-terminal collagen crosslinks (CTX), amino-terminal propeptide of type-I collagen (P1NP), and sclerostin) and functional biomarkers (Timed Up and Go (TUG), Short Physical Performance Battery (SPPB), grip strength, and leg extension power) will be measured to assess the effect on bone turnover, muscle strength, balance, and functionality. Quality of life (EQ-5D), physical activity (IPAQ) and fear of falling (FES-I) will be assessed by questionnaires. Data on adherence and falls incidence will be collected.

DISCUSSION

The PaVOS study will investigate the effects of WBV in combination with PTH 1-34 on bone parameters in postmenopausal women.

TRIAL REGISTRATION

ClinicalTrials.gov, ID: NCT02563353 . Registered on 30 September 2015.

Effects of single or combination therapy of teriparatide and anti-RANKL monoclonal antibody on bone defect regeneration in mice

OBJECTIVE

The purpose of this study is to investigate the effects of a single or combination therapy of teriparatide (TPTD) and anti-RANKL Ab (anti-murine receptor activator of nuclear factor κB ligand monoclonal antibody) on the regeneration of both cancellous and cortical bone.

METHODS

Nine-week-old mice underwent bone defect surgery on the left femoral metaphysis (cancellous-bone healing model) and right femoral mid-diaphysis (cortical-bone healing model). After surgery, the mice were assigned to 1 of 4 groups to receive 1) saline (5 times a week; CNT group), 2) TPTD (40μg/kg 5 times a week; TPTD group), 3) anti-RANKL Ab (5mg/kg once; Ab group), or 4) a combination of TPTD and anti-RANKL Ab (COMB group). The following analyses were performed: Time-course microstructural analysis of healing in both cancellous and cortical bone in the bone defect, the volumetric bone mineral density of the tibia with micro-computed tomography, histological, histomorphometrical, and biomechanical analysis of regenerated bone.

RESULTS

Regeneration of cancellous bone volume in the COMB group was the highest among the 4 groups, and this combined administration prompted medullary callus formation in the early phase of bone regeneration. On the other hand, regeneration of cortical bone volume in the COMB group was significantly higher than in the Ab group and was almost same as in the TPTD group. Histological analysis showed remaining woven bones, cartilage matrix, and immature lamellar bone in the COMB and Ab groups. However, biomechanical analysis showed that hardness and Young's modulus of regenerated cortical bone in the COMB group was not lower than in both the CNT and TPTD groups. Volumetric bone mineral density in the tibia was significantly increased in the COMB group compared with the other 3 groups.

CONCLUSION

In the early phase of bone regeneration, the combination of TPTD and anti-RANKL Ab accelerates regeneration of cancellous bone in bone defects and increases cancellous bone mass in the tibia more effectively than either agent does individually, but these additive effects are not observed in the regeneration of cortical bone.

Spatiotemporal Changes of Calcitonin Gene-Related Peptide Innervation in Spinal Fusion

Few studies have investigated the role calcitonin gene-related peptide (CGRP) plays in the process of spinal fusion. The aim of the present study is to observe the temporal and spatial changes of CGRP induced by experimental fusion surgery in rats and elucidate the role of CGRP in spinal fusion. Male Sprague-Dawley rats were used in the study and the specimens were collected on the 7th, 14th, 21st, and 28th day, respectively. Then, histological and immunohistochemical analysis were applied to evaluate the fusion mass and spatiotemporal changes of CGRP chronologically. The results demonstrated that density of CGRP reached peak on the 21st day after surgery and most of the CGRP expression located surrounding the interface of allograft and fibrous tissue where the cells differentiate into osteoblasts, indicating that CGRP might be involved in the process of bone formation and absorption.