A combination of methotrexate and zoledronic acid prevents bone erosions and systemic bone mass loss in collagen induced arthritis

Introduction Osteoclasts play a key role in the pathogenesis of bone erosion and systemic bone mass loss during rheumatoid arthritis (RA). In this study, we aimed to determine the effect of methotrexate (MTX) and zoledronic acid (ZA), used alone or in combination, on osteoclast-mediated bone erosions and systemic bone mass loss in a rat model of collagen induced arthritis (CIA). We hypothesized that MTX and ZA could have an additive effect to prevent both bone erosion and systemic bone loss. Methods Arthritis was induced in 64 female Sprague-Dawley rats. After the clinical onset of CIA, rats were assigned to treatment with MTX (1 mg/kg/week), ZA (100 μg/kg twice weekly), both treatments at the same regimens, or vehicle. Arthritis score and paw thickness were recorded twice weekly. The rats were sacrificed on D28 and hind paws were removed for radiographic, histological and immunohistochemical analysis. The effects of treatments on osteoclastogenesis were determined by Tartrate resistant acid phosphatase (TRAP) staining. Micro-CT of the tibia was carried out for histomorphometric analysis. Bone mass density was evaluated by densitometry. Results MTX significantly decreased the severity of CIA, whereas ZA slightly exacerbated it. When these two drugs were used in combination, MTX prevented the pro-inflammatory effect of ZA. The combination of ZA with MTX was more effective than MTX alone for reducing structural joint damage with a dramatic decrease of osteoclasts' number in the eroded joints. However, MTX alone also significantly reduced the number of osteoclasts and the number of CD68+ mononuclear cells. ZA alone, or ZA with MTX, significantly increased the systemic bone mass density measured by densitometry and bone volume on histomorphometric analysis. Conclusions A combination of MTX and ZA prevented both bone erosion and systemic bone loss in a rat model of arthritis. Both treatments independently decreased the number of osteoclasts in the eroded joint. However, while MTX probably acts mainly through a decrease of inflammation, ZA has a direct effect on osteoclasts, allowing a dramatic down-regulation of these cells in inflamed joints. These two different mechanisms of action provide support for the use of a combination of these two drugs to improve the prevention of structural joint damage in RA

Physical activity and brain health in patients with atrial fibrillation

Background and purpose: Vascular brain lesions, such as ischemic infarcts, are common among patients with atrial fibrillation (AF) and are associated with impaired cognitive function. The role of physical activity (PA) in the prevalence of brain lesions and cognition in AF has not been investigated. Methods: Patients from the multicenter Swiss‐AF cohort study were included in this cross‐sectional analysis. We assessed regular exercise (RE; at least once weekly) and minutes of weekly PA using a validated questionnaire. We studied associations with ischemic infarcts, white matter hyperintensities, cerebral microbleeds, and brain volume on brain magnetic resonance imaging and with global cognition measured with a cognitive construct (CoCo) score.ResultsAmong 1490 participants (mean age = 72 ± 9 years), 730 (49%) engaged in RE. In adjusted regression analyses, RE was associated with a lower prevalence of ischemic infarcts (odds ratio [OR] = 0.78, 95% confidence interval [CI] = 0.63–0.98, p = 0.03) and of moderate to severe white matter hyperintensities (OR = 0.78, 95% CI = 0.62–0.99, p = 0.04), higher brain volume (β‐coefficient = 10.73, 95% CI = 2.37–19.09, p = 0.01), and higher CoCo score (β‐coefficient = 0.08, 95% CI = 0.03–0.12, p < 0.001). Increasing weekly PA was associated with higher brain volume (β‐coefficient = 1.40, 95% CI = 0.65–2.15, p < 0.001). Conclusions: In AF patients, RE was associated with a lower prevalence of ischemic infarcts and of moderate to severe white matter disease, with larger brain volume, and with better cognitive performance. Prospective studies are needed to investigate whether these associations are causal. Until then, our findings suggest that patients with AF should be encouraged to remain physically active

Precision tests of the Standard Model with leptonic and semileptonic kaon decays

We present a global analysis of leptonic and semileptonic kaon decays data, including all recent results by BNL-E865, KLOE, KTeV, ISTRA+, and NA48. Experimental results are critically reviewed and combined, taking into account theoretical (both analytical and numerical) constraints on the semileptonic kaon form factors. This analysis leads to a very accurate determination of Vus and allows us to perform several stringent tests of the Standard Model.We present a global analysis of leptonic and semileptonic kaon decays data, including all recent results by BNL-E865, KLOE, KTeV, ISTRA+, and NA48. Experimental results are critically reviewed and combined, taking into account theoretical (both analytical and numerical) constraints on the semileptonic kaon form factors. This analysis leads to a very accurate determination of Vus and allows us to perform several stringent tests of the Standard Model

The relative merits of anabolics versus anti-resorptive compounds: where our targets should be, and whether we are addressing them.

Currently available results from fracture trials provide evidence that the most potent anti-resorptive agents reduce vertebral and non-vertebral fractures maximally by 61% and 51%, respectively. Results from the Phase III trial with denosumab, the human monoclonal antibody, are eagerly awaited. Denosumab leads to sustained 80-90% reduction of bone resorption markers, which is below the level commonly achieved with bisphosphonates, and it will be interesting to see whether this leads to an improvement in its anti-fracture efficacy over bisphosphonates. If the majority of the anti-fracture efficacy of anti-resorptive agents results from the reduction of the remodelling space (removal of stress raisers) and the conservation of structural integrity of cancellous bone, a further decrease in bone resorption might not be desirable, especially as suppression of the residual remodelling capacity could lead to an increased risk for accumulation of microdamage. In contrast to anti-resorptive agents, the bone anabolic parathyroid hormone activates modelling drifts, which act to increase trabecular thickness and add bone predominantly on the endocortical, and to a lesser degree the periosteal, surface. Despite its anabolic nature, reduction of vertebral and non-vertebral fractures is only marginally better than those achieved with anti-resorptive agents. Ageing compromises locomotor capacity and is associated with an increased risk of falls. Perhaps it is time to shift our attendance to the age-related deterioration of muscle or neuromuscular function as a target and add this 'adjuvant therapy' to the potent anti-remodelling and bone anabolic agents available for the treatment of osteoporosis if we truly want to reduce fracture incidence beyond what is possible today

Conditional transgene expression mediated by the mouse beta-actin locus.

Transgenic mice are an effective model to study gene function in vivo; however, position effects can complicate tissue-specific transgene analysis. To facilitate precise targeting of a transgenic construct into the mouse genome, we combined the Cre/lox and Flp/FRT recombination systems to allow for rapid transgene replacement and conditional transgene expression from the endogenous beta-actin locus. Flp/FRT recombination was used to rapidly exchange FRT-flanked transgene cassettes by recombinase-mediated cassette exchange in embryonic stem cells, while transgene expression can be activated in mice after Cre-mediated excision of a floxed STOP cassette. To validate our system, we analyzed the expression profile of an EGFP reporter gene after integration into the beta-actin locus and Cre-mediated excision of the floxed STOP cassette. Breeding of EGFP reporter mice with various Cre mouse lines resulted in the expected expression profiles, demonstrating the feasibility of the model to facilitate predictable and strong transgene expression in a spatially and temporally controlled manner

European Society of Biomechanics S.M. Perren Award 2008: using temporal trends of 3D bone micro-architecture to predict bone quality.

In longitudinal studies, three-dimensional (3D) bone images are acquired at sequential time points essentially resulting in four-dimensional (4D) data for an individual. Based on the 4D data, we propose to calculate temporal trends and project these trends to estimate future bone architecture. Multiple consecutive deformation fields, calculated with Demons deformable image registration algorithm, were extrapolated on a voxel-by-voxel basis. Test data were from in vivo micro-computed tomography (microCT) scans of the proximal tibia of Wistar rats that were either ovariectomized (OVX; N=5) or sham operated (SHAM; N=6). Measurements performed at baseline, 4 and 8 weeks were the basis to predict the 12 week data. Predicted and actual 12 week data were compared using qualitative (3D rendering) and quantitative (geometry, morphology and micro-finite element, microFE) methods. The results indicated a voxel-based linear extrapolation scheme yielded mean geometric errors that were smaller than the voxel size of 15 microm. Key morphological parameters that were estimated included bone volume ratio (BV/TV; mean error 0.4%, maximum error 9%), trabecular thickness (Tb.Th; -1.1%, 11%), connectivity density (Conn.D; 9.0%, 18.5%) and the apparent Young's modulus (E(1); 6.0%, 32%). These data demonstrated a promising and novel approach for quantitatively capturing in vivo bone dynamics at the local trabecular level. The method does not require an a priori understanding of the diseases state, and can provide information about the trends of the bone remodeling process that may be used for better monitoring and treatment of diseases such as osteoporosis

Combined effects of zoledronate and mechanical stimulation on bone adaptation in an axially loaded mouse tibia

Local bisphosphonate delivery may be a solution to prevent periprosthetic bone loss and improve orthopedic implants fixation. In load-bearing implants, periprosthetic bone is exposed to high mechanical demands, which in normal conditions induce an adaptation of bone. In this specific mechanical situation, the modulation of the bone response by bisphosphonate remains uncertain. We assessed the combined effects of zoledronate and mechanical loading on bone adaptation using an in-vivo axial compression model of the mouse tibia and injections of zoledronate. Bone structure was assessed with in-vivo µCT before and after the period of stimulation and the biomechanical properties of the tibias were assessed with 3 point-bending tests after sacrifice. Axial loading induced a localized increase of cortical thickness and bone area. Zoledronate increased cortical thickness, bone perimeter, and bone area. At the most loaded site of the tibia, the combined effect of zoledronate and mechanical stimulation was significantly smaller than the effect of zoledronate plus the effect of mechanical loading. This suggested that an interaction between zoledronate and mechanical loading might exist at high levels of strains

Long-term protective effects of zoledronic acid on cancellous and cortical bone in the ovariectomized rat.

Current bisphosphonate therapies effectively prevent bone loss in postmenopausal women. We studied the effect of a single intravenous dose of ZOL in ovariectomized rats. Protection from bone loss was dose dependent, lasting for up to 32 weeks, supporting the rationale for an annual intravenous dosing regimen of ZOL for treatment of postmenopausal osteoporosis. INTRODUCTION: Once-yearly dosing with zoledronic acid (ZOL) 5 mg can increase BMD and reduce fracture rate in postmenopausal women with low BMD. The primary objective of this study was to determine the duration of bone protective effects of a single dose of ZOL in ovariectomized rats, an animal model of postmenopausal osteopenia. Secondary objectives were to determine the effects on bone turnover and mechanical properties. MATERIALS AND METHODS: Female Wistar rats (10 per group) received single intravenous doses of ZOL 0.8, 4, 20, 100, or 500 microg/kg, alendronate 200 microg/kg, or isotonic saline 4 days before bilateral ovariectomy. Sham-operated controls were pretreated with saline. Mass and density of cancellous and cortical bone (pQCT) were measured at 4-wk intervals for 32 wk. Bone architecture (microCT), bone formation dynamics (fluorochrome label-based histomorphometry), and biomechanical strength in compression testing were also assessed at 32 wk. RESULTS: Ovariectomy-associated BMD loss was significantly attenuated for 32 wk by ZOL >or=4 microg/kg for total BMD, ZOL >or=20 microg/kg for cortical BMD, and ZOL >or=4 microg/kg for cancellous BMD (p < 0.01 versus ovariectomized controls). Alendronate 200 microg/kg was of equivalent potency to ZOL 20 microg/kg. Ovariectomy-associated decreases in trabecular architectural parameters were dose-dependently attenuated by ZOL. Alendronate 200 microg/kg was equivalent to ZOL 20 microg/kg. The bone resorption marker TRACP5b indicated transient suppression of elevated osteoclast activity by ZOL relative to OVX-rats even at the lowest dose of 0.8 microg/kg, whereas at 100-500 microg/kg, the effect was significant relative to the OVX control for the entire duration of the study of 32 wk. Bone formation parameters were not significantly affected by ZOL 20 microg/kg but were significantly reduced by ZOL 100-500 microg/kg. Alendronate 200 microg/kg was equivalent to ZOL 100 microg/kg. ZOL produced dose-related improvements in bone strength parameters after ovariectomy. Alendronate 200 microg/kg was of similar potency to ZOL 20 microg/kg. CONCLUSIONS: The duration and magnitude of the bone-protecting effect of a single intravenous dose of ZOL in ovariectomized rats is dose dependent and lasts for up to 32 wk. Compared with alendronate, ZOL shows 10-fold higher potency in preventing bone loss. These data support the use of an annual intravenous ZOL dosing regimen for the treatment of osteoporosis