Strontium ranelate: dose-dependent effects in established postmenopausal vertebral osteoporosis--a 2-year randomized placebo controlled trial

SrTiO3 Nanotube-Based "Pneumatic Nanocannon" for On-Demand Delivery of Antibacterial and Sustained Osseointegration Enhancement

Infection and aseptic loosening caused by bacteria and poor osseointegration remain serious challenges for orthopedic implants. The advanced surface modification of implants is an effective strategy for addressing these challenges. This study presents a "pneumatic nanocannon" coating for titanium orthopedic implants to achieve on-demand release of antibacterial and sustained release of osteogenic agents. SrTiO3 nanotubes (SrNT) were constructed on the surface of Ti implants as "cannon barrel," the "cannonball" (antibiotic) and "propellant" (NH4HCO3) were codeposited into SrNT with assistance of mussel-inspired copolymerization of dopamine and subsequently sealed by a layer of polydopamine. The encapsulated NH4HCO3 within the nanotubes could be thermally decomposed into gases under near-infrared irradiation, propelling the on-demand delivery of antibiotics. This coating demonstrated significant efficacy in eliminating typical pathogenic bacteria both in planktonic and biofilm forms. Additionally, this coating exhibited a continuous release of strontium ions, which significantly enhanced the osteogenic differentiation of preosteoblasts. In an implant-associated infection rat model, this coating demonstrated substantial antibacterial efficiency (>99%) and significant promotion of osseointegration, along with alleviated postoperative inflammation. This pneumatic nanocannon coating presents a promising approach to achieving on-demand infection inhibition and sustained osseointegration enhancement for titanium orthopedic implants.

End-Stage Tibiotalar Osteoarthritis and Chronic Strontium Toxicity

Metal toxicity due to environmental sources or orthopedic implants has been a primary focus in recent literature. Specifically, in orthopedics, total joint arthroplasty regarding metal-on-metal articulation with cobalt-chromium articulation has adverse local and systemic effects. In particular, strontium toxicity is less known metal toxicity that can cause many systemic effects such as severe osteoporosis. This is the first reported case of strontium toxicity and end-stage tibiotalar osteoarthritis. We present a case of a 68-year-old female with bilateral ankle pain and deformity that were refractory to conservative measures, including physical therapy and anti-inflammatory medications. She was diagnosed with bilateral osteoarthritis and osteoporosis secondary to strontium toxicity by exclusion after extensive workup with a multi-disciplinary approach. The patient pursued conservative measures with ankle-foot orthosis, physical therapy, and anti-inflammatory medications. After the failure of conservative measures with over two years of follow-up, we recommended operative intervention to improve function and pain with staged bilateral tibiotalocalcaneal fusions utilizing an intramedullary device. Since she is moving out of state, she chose to pursue operative intervention at a different institution in order to establish long-term follow-up. The patient was placed on teriparatide for her osteoporosis secondary to strontium toxicity. Clinicians should be aware of strontium toxicity and its systemic effects and take a multi-disciplinary approach to treatment for optimal management.

Evaluation of La(XT), a novel lanthanide compound, in an OVX rat model of osteoporosis

Purpose

The purpose of this study was to evaluate the efficacy and toxicity of a novel lanthanum compound, La(XT), in an ovariectomized (OVX) rat model of osteoporosis.

Methods

Twenty-four ovariectomized female Sprague Dawley rats were divided into 3 groups receiving a research diet with/without treatment compounds (alendronate: 3 mg/kg; La(XT) 100 mg/kg) for three months. At the time of sacrifice, the kidney, liver, brain, lung and spleen were collected for histological examination. The trabecular bone structure of the tibiae was evaluated using micro-CT and a three-point metaphyseal mechanical test was used to evaluate bone failure load and stiffness.

Results

No significant differences were noted in plasma levels of calcium, phosphorus, creatinine, alanine aminotransferase (ALT), and aspartate aminotransferase (AST) between the La(XT) treatment compared to the non-treated OVX group. Alendronate-treated animals (positive control) showed higher BV/TV, Tb.N and lower Tb.Th and Tb.Sp when compared to the non-treated OVX group. Mechanical analysis indicated that stiffness was higher in the alendronate (32.88%, p = 0.04) when compared to the non-treated OVX group. Failure load did not differ among the groups.

Conclusions

No kidney or liver toxicities of La(XT) treatments were found during the three-month study. The absence of liver and kidney toxicity with drug treatment for 3 months, as well as the increased trabecular bone stiffness are encouraging for the pursuit of further studies with La(XT) for a longer duration of time.

Effect of Strontium Ranelate on Condylar Growth during Mandibular Advancement in Rats

Objective

Strontium ranelate (SR), unlike other anti-osteoporotic agents, might not only prevent bone resorption but also might induce bone formation. The aim of this experimental study was to evaluate the effects of systemic SR on condylar growth during mandibular advancement (MA) in growing rats.

Methods

Fifty-six, 8-week-old Wistar male rats weighting 160-190 g were randomly divided into four groups; one control (n=14) and three experimental (n=14). Group 1: Control group, Group 2: SR (900mg/kg daily dose), Group 3: MA, Group 4: SR +MA. The amount and direction of mandibular growth were assessed by linear measurements on the computed tomography (CT) images taken on days 1, 15, and 30. For immunohistochemical evaluation, half of the subjects in the groups were sacrificed on the 15th day (early phase) and the rest of them on the 30th day (late phase). New cartilage and bone formation areas on the condyle were analyzed by using Sox9 and Osteopontin antibodies.

Results

Early and late CT images measurements showed no significant difference between the groups (p<0.05). However, there were significant differences between the control and experimental groups in the immunohistochemical assessment. Severe immunolocalization of SOX9 and Osteopontin was observed in Group 4, while the immunolocalization scores were moderate in Group 2 and Group 3. In addition, early histological findings were similar to late results in all groups.

Conclusion

In mandibular advancement therapy, Strontium ranelate could be therapeutically effective in avoiding relapse and reducing the duration of retention.

A review of the latest insights into the mechanism of action of strontium in bone

Interest in strontium (Sr) has persisted over the last three decades due to its unique mechanism of action: it simultaneously promotes osteoblast function and inhibits osteoclast function. While this mechanism of action is strongly supported by in vitro studies and small animal trials, recent large-scale clinical trials have demonstrated that orally administered strontium ranelate (SrRan) may have no anabolic effect on bone formation in humans. Yet, there is a strong correlation between Sr accumulation in bone and reduced fracture risk in post-menopausal women, suggesting Sr acts via a purely physiochemical mechanism to enhance bone strength. Conversely, the local administration of Sr with the use of modified biomaterials has been shown to enhance bone growth, osseointegration and bone healing at the bone-implant interface, to a greater degree than Sr-free materials. This review summarizes current knowledge of the main cellular and physiochemical mechanisms that underly Sr's effect in bone, which center around Sr's similarity to calcium (Ca). We will also summarize the main controversies in Sr research which cast doubt on the 'dual-acting mechanism'. Lastly, we will explore the effects of Sr-modified bone-implant materials both in vitro and in vivo, examining whether Sr may act via an alternate mechanism when administered locally.

Effects of strontium ranelate on bone mass and bone turnover in women with thalassemia major-related osteoporosis

Subjects affected by thalassemia major (TM) often have reduced bone mass and increased fracture risk. Strontium ranelate (SrR) is an effective treatment for postmenopausal and male osteoporosis. To date, no data exist on the use of SrR in the treatment of TM-related osteoporosis. Our aim was to evaluate the effects of SrR on bone mineral density (BMD), bone turnover markers and inhibitors of Wnt signaling (sclerostin and DKK-1). Twenty-four TM osteoporotic women were randomized to receive daily SrR 2 g or placebo in addition to calcium carbonate (1,000 mg) and vitamin D (800 IU). BMD at the lumbar spine and femoral neck, bone turnover markers (C-terminal telopeptide of procollagen type I [CTX], bone-specific alkaline phosphatase [BSAP]) and insulin-like growth factor-1 (IGF-1), sclerostin and DKK-1 were assessed at baseline and after 24 months. Back pain was measured by visual analog scale (VAS) every 6 months. After 24 months, TM women treated with SrR had increased their spine BMD values in comparison to baseline (p < 0.05). Moreover, they also exhibited a reduction of CTX and sclerostin levels (but not DKK-1) and exhibited an increase of BSAP and IGF-1 (p < 0.05); however, no significant changes were observed in the placebo group. In the SrR group, a reduction of back pain was observed after 18 months in comparison to baseline (p < 0.05) and after 24 months in comparison to placebo (p < 0.05). Our study reports for the first time the effects of SrR in the treatment of TM-related osteoporosis. SrR treatment improved BMD and normalized bone turnover markers, as well as lowering sclerostin serum levels.

Increased risk of strontium ranelate-related SJS/TEN is associated with HLA

Severe adverse drug reactions (ADR) of Stevens-Johnson syndrome and toxic epidermal necrolysis (SJS/TEN) in some patients receiving strontium ranelate have been reported, but the risk factors are unclear. We show that HLA-A*33:03 and B*58:01 are significantly associated with patients who developed SJS/TEN; and provide the first evidence that genetic risk factors are involved in strontium ranelate-associated SJS/TEN.

INTRODUCTION

In this study, HLA as a genetic risk factor was assessed among osteoporotic patients prescribed with strontium ranelate that developed severe cutaneous adverse drug reactions (SCARs) compared with those who were tolerant.

METHODS

Genomic DNA isolated from peripheral blood mononuclear cells (PBMCs) of patients was HLA typed using sequencing-based typing method to determine their HLA profiles.

RESULTS

Osteoporotic patients who are currently on strontium ranelate were enrolled in the study (n = 76). Tolerant controls were defined as patients who received strontium ranelate for a minimum of 3 months (range 3 months to 8 years) with no reports of any cutaneous reactions as these reactions usually occur within the first 12 weeks after starting treatment. Retrospective cases of SJS/TEN were also identified (n = 5). The majority of the accrued samples were of Han Chinese descent: controls (n = 72) and cases (n = 4). All cases and controls were genotyped at four HLA genes, namely HLA-A, HLA-B, HLA-C, and HLA-DRB1. In comparing the samples of Han Chinese descent (72 controls and 4 cases), we found significant associations with HLA-A*33:03 (p = 0.002) and HLA-B*58:01 (p = 0.023). There was no significant association with any HLA-C or HLA-DRB1 alleles.

CONCLUSIONS

This study reveals that the occurrence of SJS/TEN in Han Chinese patients receiving strontium ranelate is HLA associated. This has important clinical implications for understanding the underlying mechanisms for this ADR as well as evaluating the potential role of genetic pre-screening for osteoporotic patients who may be prescribed strontium ranelate.

Bone regenerating effect of surface-functionalized titanium implants with sustained-release characteristics of strontium in ovariectomized rats

Since strontium (Sr) is known for its anabolic and anticatabolic effect on bone, research has been focused on its potential impact on osseointegration. The objective of this study was to investigate the performance of nanotopographic implants with a Sr-functionalized titanium (Ti) coating (Ti–Sr–O) with respect to osseointegration in osteoporotic bone. The trial was designed to examine the effect of sustained-release characteristics of Sr in poor-quality bone. Three Ti–Sr–O groups, which differed from each other in coating thickness, Sr contents, and Sr release, were examined. These were prepared by a magnetron sputtering process and compared to uncoated grade 4 Ti. Composition, morphology, and mechanical stability of the coatings were analyzed, and Sr release data were gained from in vitro washout experiments. In vivo investigation was carried out in an osteoporotic rat model and analyzed histologically, 6 weeks and 12 weeks after implantation. Median values of bone-to-implant contact and new bone formation after 6 weeks were found to be 84.7% and 54.9% (best performing Sr group) as compared to 65.2% and 23.8% (grade 4 Ti reference), respectively. The 12-week observation period revealed 84.3% and 56.5% (best performing Sr group) and 81.3% and 39.4% (grade 4 Ti reference), respectively, for the same measurements. The increase in new bone formation was found to correlate with the amount of Sr released in vitro. The results indicate that sputtered nanostructured Ti–Sr–O coatings showed sustained release of Sr and accelerate osseointegration even in poor-quality bone, and thus, may have impact on practical applications for medical implants.

Nonsurgical Treatment Strategies after Osteoporotic Hip Fractures

Osteoporosis is a metabolic disease that is increasing in prevalence as people live longer. Because the orthopedic surgeon is frequently the first and often the only physician to manage patients with osteoporotic hip fractures, every effort should be made to prevent future fractures. A multidisciplinary approach is essential in treatment of osteoporotic fractures. Basic treatment includes calcium and vitamin D supplementation, fall prevention, hip protection, and balance and exercise programs. Currently available pharmacologic agents are divided into antiresorptive and anabolic groups. Antiresorptive agents such as bisphosphonates limit bone resorption through inhibition of osteoclastic activity. Anabolic agents such as parathyroid hormone promote bone formation.

A comparison of adverse event and fracture efficacy data for strontium ranelate in regulatory documents and the publication record

OBJECTIVE

Recently, the European Medicines Agency reported that strontium ranelate increases myocardial infarction risk in postmenopausal women, 8.5 years after it was registered for use in osteoporosis. Unreported serious adverse events in clinical trials for other pharmaceuticals have been described in recent years. We assessed reporting of adverse events and fracture efficacy of strontium.

METHODS

We compared data on adverse effects (myocardial infarction, venous thromboembolism and pulmonary embolism) and fracture efficacy of strontium in publicly available regulatory documents with data in publications retrieved from searching PubMed.

RESULTS

We identified 5 regulatory documents and 9 primary publications of 7 randomised, placebo-controlled trials of strontium that reported relevant data. We identified several areas of concern in these reports: the increased risk of myocardial infarction with strontium was not identified in a pivotal phase 3 clinical trial despite specific regulatory review of cardiovascular events; data on myocardial infarction were not included in any primary publication; increased risks of venous thromboembolism and pulmonary embolism with strontium were not reported in either of the phase 3 clinical trials; data on venous thromboembolism were reported in only 5 of 9 primary publications, data on pulmonary embolism in only 2 of 9 primary publications, and either was discussed in <50% of subsequent review articles. There were differences in participant numbers, fracture cases and venous thromboembolism cases between regulatory documents and primary publications. Based on all available data from primary publications and regulatory documents, the number of fractures prevented by strontium use is similar to the number of extra cases of venous thromboembolism, pulmonary embolism and myocardial infarction caused by strontium use.

CONCLUSIONS

The risks of strontium use are similar to the benefits. Full disclosure of the clinical trial data and regulatory documents would allow clinicians and their patients to decide whether use of the drug is worthwhile.

Periodontal regeneration using strontium-loaded mesoporous bioactive glass scaffolds in osteoporotic rats

Recent studies demonstrate that the rate of periodontal breakdown significantly increased in patients compromised from both periodontal disease and osteoporosis. One pharmacological agent used for their treatment is strontium renalate due to its simultaneous ability to increase bone formation and halt bone resorption. The aim of the present study was to achieve periodontal regeneration of strontium-incorporated mesoporous bioactive glass (Sr-MBG) scaffolds in an osteoporotic animal model carried out by bilateral ovariectomy (OVX). 15 female Wistar rats were randomly assigned to three groups: control unfilled periodontal defects, 2) MBG alone and 3) Sr-MBG scaffolds. 10 weeks after OVX, bilateral fenestration defects were created at the buccal aspect of the first mandibular molar and assessed by micro-CT and histomorphometric analysis after 28 days. Periodontal fenestration defects treated with Sr-MBG scaffolds showed greater new bone formation (46.67%) when compared to MBG scaffolds (39.33%) and control unfilled samples (17.50%). The number of TRAP-positive osteoclasts was also significantly reduced in defects receiving Sr-MBG scaffolds. The results from the present study suggest that Sr-MBG scaffolds may provide greater periondontal regeneration. Clinical studies are required to fully characterize the possible beneficial effect of Sr-releasing scaffolds for patients suffering from a combination of both periodontal disease and osteoporosis.

Trajectories of Bone Remodeling Markers and Bone Mineral Density during Treatment with Strontium Ranelate in Postmenopausal Women Previously Treated with Bisphosphonates

OBJECTIVE

To evaluate the responses of C-terminal telopeptide (CTX) and serum osteocalcin after the first 4 months of treatment with strontium ranelate (SR) and demonstrate their association with long-term bone density changes.

SUBJECTS AND METHODS

A sample of 13 postmenopausal women with osteoporosis was analyzed (mean age 65 ± 7.7 years), who were treated with SR for an average of 2.56 ± 0.86 years. All patients had undergone previous treatment with bisphosphonates for an average period of 4.88 ± 2.27 years. Serum CTX and osteocalcin levels were determined before and after four months of treatment with SR. Bone mineral density in the lumbar spine and femoral neck were obtained before and after treatment with SR.

RESULTS

We observed an average increase of 53.7% in the CTX levels, and 30.7% in the osteocalcin levels. The increase in bone markers was associated with a mean 4.8% increase in lumbar spine bone mineral density (BMD) from 0.820 to 0.860 g/cm² (T-score from −2.67 to −1.92; P = 0.001), after 2.5 years of treatment with SR.

CONCLUSION

These data suggest an anabolic effect of SR on postmenopausal women who were previously treated with long-term bisphosphonates.

Osteoporosis - a current view of pharmacological prevention and treatment

Postmenopausal osteoporosis is the most common bone disease, associated with low bone mineral density (BMD) and pathological fractures which lead to significant morbidity. It is defined clinically by a BMD of 2.5 standard deviations or more below the young female adult mean (T-score =−2.5). Osteoporosis was a huge global problem both socially and economically – in the UK alone, in 2011 £6 million per day was spent on treatment and social care of the 230,000 osteoporotic fracture patients – and therefore viable preventative and therapeutic approaches are key to managing this problem within the aging population of today. One of the main issues surrounding the potential of osteoporosis management is diagnosing patients at risk before they develop a fracture. We discuss the current and future possibilities for identifying susceptible patients, from fracture risk assessment to shape modeling and in relation to the high heritability of osteoporosis now that a plethora of genes have been associated with low BMD and osteoporotic fracture. This review highlights the current therapeutics in clinical use (including bisphosphonates, anti-RANKL [receptor activator of NF-κB ligand], intermittent low dose parathyroid hormone, and strontium ranelate) and some of those in development (anti-sclerostin antibodies and cathepsin K inhibitors). By highlighting the intimate relationship between the activities of bone forming (osteoblasts) and bone-resorbing (osteoclasts) cells, we include an overview and comparison of the molecular mechanisms exploited in each therapy.

Vitamin d deficiency among postmenopausal women with osteoporosis

BACKGROUND

Hypovitaminosis D is widely prevalent in India and is a formidable issue especially in postmenopausal women. The study intends to estimate the prevalence of vitamin D deficiency among postmenopausal women with osteoporosis.

METHODS

The study was performed at a referral teaching institute in north India between 2007 and 2009. One hundred and ninety postmenopausal osteoporotic women were enrolled and the clinical information was collected along with the assessment of biochemical parameters.

RESULTS & CONCLUSION

Serum vitamin D was found to be de- ficient in two third of patients. A significant correlation was observed between body mass index and bone mineral density at lumbar spine. Prevention and early detection of hypovitaminosis D is the key to reduce the incidence of osteoporosis among postmenopausal women.

Efficacy and safety of strontium ranelate in the treatment of knee osteoarthritis: results of a double-blind, randomised placebo-controlled trial

Background

Strontium ranelate is currently used for osteoporosis. The international, double-blind, randomised, placebo-controlled Strontium ranelate Efficacy in Knee OsteoarthrItis triAl evaluated its effect on radiological progression of knee osteoarthritis.

Methods

Patients with knee osteoarthritis (Kellgren and Lawrence grade 2 or 3, and joint space width (JSW) 2.5–5 mm) were randomly allocated to strontium ranelate 1 g/day (n=558), 2 g/day (n=566) or placebo (n=559). The primary endpoint was radiographical change in JSW (medial tibiofemoral compartment) over 3 years versus placebo. Secondary endpoints included radiological progression, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, and knee pain. The trial is registered (ISRCTN41323372).

Results

The intention-to-treat population included 1371 patients. Treatment with strontium ranelate was associated with smaller degradations in JSW than placebo (1 g/day: −0.23 (SD 0.56) mm; 2 g/day: −0.27 (SD 0.63) mm; placebo: −0.37 (SD 0.59) mm); treatment-placebo differences were 0.14 (SE 0.04), 95% CI 0.05 to 0.23, p<0.001 for 1 g/day and 0.10 (SE 0.04), 95% CI 0.02 to 0.19, p=0.018 for 2 g/day. Fewer radiological progressors were observed with strontium ranelate (p<0.001 and p=0.012 for 1 and 2 g/day). There were greater reductions in total WOMAC score (p=0.045), pain subscore (p=0.028), physical function subscore (p=0.099) and knee pain (p=0.065) with strontium ranelate 2 g/day. Strontium ranelate was well tolerated.

Conclusions

Treatment with strontium ranelate 1 and 2 g/day is associated with a significant effect on structure in patients with knee osteoarthritis, and a beneficial effect on symptoms for strontium ranelate 2 g/day.

Progress and challenges in biomaterials used for bone tissue engineering: bioactive glasses and elastomeric composites

Driven by the increasing economic burden associated with bone injury and disease, biomaterial development for bone repair represents the most active research area in the field of tissue engineering. This article provides an update on recent advances in the development of bioactive biomaterials for bone regeneration. Special attention is paid to the recent developments of sintered Na-containing bioactive glasses, borate-based bioactive glasses, those doped with trace elements (such as Cu, Zn, and Sr), and novel elastomeric composites. Although bioactive glasses are not new to bone tissue engineering, their tunable mechanical properties, biodegradation rates, and ability to support bone and vascular tissue regeneration, as well as osteoblast differentiation from stem and progenitor cells, are superior to other bioceramics. Recent progresses on the development of borate bioactive glasses and trace element-doped bioactive glasses expand the repertoire of bioactive glasses. Although boride and other trace elements have beneficial effects on bone remodeling and/or associated angiogenesis, the risk of toxicity at high levels must be highly regarded in the design of new composition of bioactive biomaterials so that the release of these elements must be satisfactorily lower than their biologically safe levels. Elastomeric composites are superior to the more commonly used thermoplastic-matrix composites, owing to the well-defined elastic properties of elastomers which are ideal for the replacement of collagen, a key elastic protein within the bone tissue. Artificial bone matrix made from elastomeric composites can, therefore, offer both sound mechanical integrity and flexibility in the dynamic environment of injured bone.

Strontium Ranelate: Long-Term Efficacy against Vertebral, Nonvertebral and Hip Fractures in Patients with Postmenopausal Osteoporosis

Osteoporosis treatments need to combine an unequivocally demonstrated reduction of fractures, at various skeletal sites, long-term safety, and a user-friendly profile, optimizing therapeutic adherence. Strontium ranelate is the first compound to simultaneously decrease bone resorption and stimulate bone formation. Its antifracture efficacy, at various skeletal sites, has been established up to 8 years, through studies of the highest methodological standards. Increases in bone mineral density, observed after 1 year of treatment, are predictive of the long-term fracture efficacy, hence suggesting, for the first time in osteoporosis, that bone densitometry can be used as a monitoring tool for both efficacy and compliance. Owing to a positive benefit/risk ratio, strontium ranelate may now be considered as a first-line treatment in the management of osteoporosis.

Bone mechanotransduction may require augmentation in order to strengthen the senescent skeleton

Physical exercise is thought to hold promise as a non-invasive countermeasure against skeletal fragility arising from post-menopausal and age-related osteoporosis. Importantly, mechanical loading and exercise are capable of increasing bone size via periosteal expansion, which by far, is the most effective means of strengthening the structure of a given bone. The focus of this review was to therefore explore whether exercise has the potential to increase periosteal modeling and bone size in the senescent skeleton. A survey of exercise trials in humans suggests that exercise interventions that enhance periosteal modeling in the young skeleton fail to do the same in the elderly skeleton. Underlying this ineffectiveness, in vitro studies indicate that aging lowers basal levels of cell function and degrades bone mechanotransduction at a variety of levels from altered second messenger signaling to gene expression driving proliferation and/or differentiation. Given these age-related alterations, the ultimate efficacy of an exercise intervention may depend upon concurrent supplementation that directly address deficits in signaling and/or cell function. In this context, in vivo animal models of mechanical loading that simulate the muted periosteal adaptation in the elderly hold potential to examine the efficacy of countermeasures. Preliminary in vivo experiments suggest that pharmacologically counteracting age-related deficits in cellular function can restore exercise induced periosteal modeling in the senescent skeleton to levels observed in young animals. If the safety and efficacy of this strategy were to be confirmed for human use, it would enable the utilization of exercise as a viable countermeasure against skeletal fragility at senescence.

Osteoanabolics

Osteoporosis is characterized by reduced bone mass, impaired bone quality, and a propensity to fracture. An "osteoanabolic" should be referred to any therapy that helps increase bone mass. Bone mass represents 80% of bone mechanical strength. A low bone mass therefore provides the strongest association of future risk of fracture. This review aims to discuss all available and future therapies that attempt to increase bone mass be it organic or inorganic.

Histomorphometric interpretation of bone biopsies for the evaluation of osteoporosis treatment

Bone histomorphometry is a valuable tool in the evaluation of bone safety and the mechanism of action of drugs used in the treatment of osteoporosis. Recent studies in patients treated with anti-resorptive agents have highlighted technical issues, in particular, related to the calculation of dynamic indices of bone turnover using fluorochrome labelling. This review addresses the need for standardised approaches for overcoming these problems in order to enable valid comparison of the effects of different interventions on bone remodelling.

The use of combination therapy in the treatment of postmenopausal osteoporosis

In recent years, there has been growing interest in the potential use of combination therapy in the management of osteoporosis in postmenopausal women. Possible regimens include sequential or combined use of anti-resorptive drugs or combinations of anabolic and anti-resorptive agents, given concurrently or in sequence. Combined therapy with anti-resorptive drugs usually produces greater increases in bone mineral density (BMD) than monotherapy but there is no evidence that this results in greater anti-fracture efficacy. The use of bisphosphonates before strontium ranelate or PTH peptides blunts the BMD response. Combined PTH and anti-resorptive therapy results in more rapid gains in spine BMD and a greater increase in hip BMD than PTH monotherapy in the first year of treatment but greater gains in both spine and hip BMD are seen with PTH monotherapy than combined therapy after 2 years of treatment. Anti-resorptive therapy after PTH therapy maintains or increases the gains in BMD. Further research is required to establish the cost-effectiveness and safety of combined and sequential regimens.

Effects of kalsis, a dietary supplement, on bone metabolism in the ovariectomized rats

We studied the ability of Kalsis, a food supplement that contains selenium, citric acid, and vitamin E, to prevent the effects of ovariectomy on bone loss. Six-month-old, Wistar female rats were studied. Groups (n = 12): SHAM: sham-operated rats; OVX: ovariectomized rats, treated with vehicle; OVX + Kalsis: ovariectomized rats treated with Kalsis (25 mg/kg/day) for 3 months. Bone mineral density (BMD) was determined by DXA in lumbar spine and femur. Computerized microtomography (μCT) in femur and serum osteocalcin (BGP), aminoterminal propeptide of procollagen I (PINP), β-isomer of carboxyterminal telopeptide of collagen I (CTX), and 5b isoenzyme of tartrate-resistant acid phosphatase (TRAP) were performed. Treatment with Kalsis prevented BMD loss in OVX group. μCT showed a decrease in BV/TV, and trabecular number, and an increase in trabecular separation in OVX rats. Kalsis administration attenuated partially bone loss observed by μCT due to ovariectomy. BGP, PINP, and the resorption index (CTX/TRAP) were increased in OVX group. Treatment with Kalsis maintained this increase. The mechanism of action of this supplement is not through a decrease in bone remodelling rate. The antioxidant action of this food supplement, due to the synergism of all its components, as a cause of its beneficial effect is suggested.

A meta-analysis of the effect of strontium ranelate on the risk of vertebral and non-vertebral fracture in postmenopausal osteoporosis and the interaction with FRAX(®)

The aim of the present study was to determine the efficacy of strontium ranelate as a function of baseline fracture risk. Treatment with strontium ranelate was associated with a significant 31% decrease in all clinical osteoporotic fractures (vertebral fractures included). Hazard ratios for the effect of strontium ranelate on the fracture outcome did not change significantly with increasing fracture probability.

INTRODUCTION

Two previous studies have suggested that the efficacy of intervention may be greater in the segment of the population at highest fracture risk as assessed by the FRAX(®) algorithms. The aim of the present study was to determine whether the anti-fracture efficacy of strontium ranelate was dependent of the level of fracture risk.

METHODS

The primary data of the two phase III studies (SOTI and TROPOS) of the effects of strontium ranelate in postmenopausal osteoporosis were combined. Country-specific probabilities were computed using the FRAX(®) tool (version 2.0). The primary outcome variable comprised all clinical osteoporotic fractures (including clinical vertebral fractures). Interactions between fracture probability and efficacy were explored by Poisson regression.

RESULTS

The 10-year probability of major osteoporotic fractures (with BMD) ranged from 2.5% to 90.8%. FRAX(®)-based hip fracture probabilities ranged from 0.1% to 90.3%. The incidence of clinical osteoporotic fractures (vertebral fractures excluded) and morphometric vertebral fractures increased with increasing baseline fracture probabilities. Treatment with strontium ranelate was associated with a 31% (95% CI = 20-39%) decrease in osteoporotic clinical fractures and a 40% decrease in vertebral fractures assessed by semiquantitative morphometry (95% CI = 31-48%) Hazard ratios for the effect of strontium ranelate on the fracture outcomes did not change significantly with increasing fracture probability.

CONCLUSION

Strontium ranelate significantly decreased the risk of osteoporotic clinical fractures, non vertebral fractures and morphometric vertebral fractures in women. Overall, the efficacy of strontium ranelate was not dependent of the level of fracture risk assessed by FRAX.

Management of age-related osteoporosis and prevention of associated fractures

Osteoporosis and related fractures are a significant concern for the global community. As the population continues to age, morbidity and mortality from fractures due to low bone mineral density (BMD) will likely continue to increase. Efforts should be made to screen those at risk for osteoporosis, identify and address various risk factors for falls and associated fractures, ensure adequate calcium and vitamin D intake, and institute pharmacological therapy to increase BMD when indicated. Agents which increase BMD and have been shown to decrease fractures, particularly at the hip, should be considered preferentially over those for which only BMD data are available. Drugs which have been shown to decrease the risk of age-related osteoporotic fractures include oral bisphosphonates (alendronate, ibandronate, and risedronate), intranasal calcitonin, estrogen receptor stimulators (eg, estrogen, selective estrogen receptor modulators [raloxifene]), parathyroid hormone (teriparatide), sodium fluoride, and strontium ranelate. Data are beginning to emerge supporting various combination therapies (eg, bisphosphonate plus an estrogen receptor stimulator), though more data are needed to identify combinations which are most effective and confer added fracture protection. In addition, further research is needed to identify ideal regimens in special populations such as nursing home patients and men.

The evidence for efficacy of osteoporosis treatment in men with primary osteoporosis: a systematic review and meta-analysis of antiresorptive and anabolic treatment in men

Purpose. Fragility fractures in men constitute a major worldwide public health problem with a life-time risk of 13%. It cannot be directly inferred that antiosteoporotic drugs effective in women have the same effect in men. Our aim was to appraise the existing evidence for efficacy of osteoporosis treatment in men. Methods. This study was a systematic review of the published literature on the clinical efficacy of medical osteoporosis therapy in the reduction of fracture risk in men (age > 50 years). Studies included were randomised, placebo-controlled trials of men. Results. Five BMD studies of antiresorptive treatment were included. All studies showed an increase in BMD, but there was only a nonsignificant trend in the reduction of clinical fractures. Three BMD studies of anabolic treatment with teriparatide were also included. These showed a significant mean increase in spine BMD and for vertebral fractures a non-significant trend towards a reduction was seen. Conclusion. The evidence of medical osteoporosis treatment in men is scant and inconclusive due to the lack of prospective RCT studies with fracture prevention as primary end point. So far, all evidence is based on BMD increases in small RCT studies showing BMD increases comparable to those reported in postmenopausal women.

An Akt-dependent increase in canonical Wnt signaling and a decrease in sclerostin protein levels are involved in strontium ranelate-induced osteogenic effects in human osteoblasts

Sclerostin is an important regulator of bone homeostasis and canonical Wnt signaling is a key regulator of osteogenesis. Strontium ranelate is a treatment for osteoporosis that has been shown to reduce fracture risk, in part, by increasing bone formation. Here we show that exposure of human osteoblasts in primary culture to strontium increased mineralization and decreased the expression of sclerostin, an osteocyte-specific secreted protein that acts as a negative regulator of bone formation by inhibiting canonical Wnt signaling. Strontium also activated, in an apparently separate process, an Akt-dependent signaling cascade via the calcium-sensing receptor that promoted the nuclear translocation of β-catenin. We propose that two discrete pathways linked to canonical Wnt signaling contribute to strontium-induced osteogenic effects in osteoblasts.

Changes in total body bone mineral density following a common bone health plan with two versions of a unique bone health supplement: a comparative effectiveness research study

BACKGROUND

The US Surgeon General's Report on Bone Health suggests America's bone-health is in jeopardy and issued a "call to action" to develop bone-health plans that: (1) improve nutrition, (2) increase health literacy and, (3) increase physical activity. This study is a response to this call to action.

METHODS

After signing an informed consent, 158 adults agreed to follow an open-label bone-health plan for six months after taking a DXA test of bone density, a 43-chemistry blood test panel and a quality of life inventory (AlgaeCal 1). Two weeks after the last subject completed, a second group of 58 was enrolled and followed the identical plan, but with a different bone-health supplement (AlgaeCal 2).

RESULTS

There were no significant differences between the two groups in baseline bone mineral density (BMD) or in variables related to BMD (age, sex, weight, percent body fat, fat mass, or fat-free mass). In both groups, no significant differences in BMD or related variables were found between volunteers and non-volunteers or between those who completed per protocol and those who were lost to attrition.Both groups experienced a significant positive mean annualized percent change (MAPC) in BMD compared to expectation [AlgaeCal 1: 1.15%, p = 0.001; AlgaeCal 2: 2.79%, p = 0.001]. Both groups experienced a positive MAPC compared to baseline, but only AlgaeCal 2 experienced a significant change [AlgaeCal 1: 0.48%, p = 0.14; AlgaeCal 2: 2.18%, p < 0.001]. The MAPC in AlgaeCal 2 was significantly greater than that in AlgaeCal 1 (p = 0.005). The MAPC contrast between compliant and partially compliant subjects was significant for both plans (p = 0.001 and p = 0.003 respectively). No clinically significant changes in a 43-panel blood chemistry test were found nor were there any changes in self-reported quality of life in either group.

CONCLUSIONS

Following The Plan for six months with either version of the bone health supplement was associated with significant increases in BMD as compared to expected and, in AlgaeCal 2, the increase from baseline was significantly greater than the increase from baseline in AlgaeCal 1. Increased compliance was associated with greater increases in BMD in both groups. No adverse effects were reported in either group.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01114685.

A comparative effectiveness study of bone density changes in women over 40 following three bone health plans containing variations of the same novel plant-sourced calcium

BACKGROUND

The US Surgeon General's Report on Bone Health suggests America's bone-health is in jeopardy and issued a "call to action" to develop bone-health plans incorporating components of (1) improved nutrition, (2) increased health literacy, and (3) increased physical activity.

OBJECTIVE

To conduct a Comparative Effectiveness Research (CER) study comparing changes in bone mineral density in healthy women over-40 with above-average compliance when following one of three bone health Plans incorporating the SG's three components.

METHODS

Using an open-label sequential design, 414 females over 40 years of age were tested, 176 of whom agreed to participate and follow one of three different bone-health programs. One Plan contained a bone-health supplement with 1,000 IUs of vitamin D(3 )and 750 mg of a plant-sourced form of calcium for one year. The other two Plans contained the same plant form of calcium, but with differing amounts of vitamin D(3) and other added bone health ingredients along with components designed to increase physical activity and health literacy. Each group completed the same baseline and ending DXA bone density scans, 43-chemistry blood test panels, and 84-item Quality of Life Inventory (QOL). Changes for all subjects were annualized as percent change in BMD from baseline. Using self-reports of adherence, subjects were rank-ordered and dichotomized as "compliant" or "partially compliant" based on the median rating. Comparisons were also made between the treatment groups and two theoretical age-adjusted expected groups: a non-intervention group and a group derived from a review of previously published studies on non-plant sources of calcium.

RESULTS

There were no significant differences in baseline BMD between those who volunteered versus those who did not and between those who completed per protocol (PP) and those who were lost to attrition. Among subjects completing per protocol, there were no significant differences between the three groups on baseline measurements of BMD, weight, age, body fat and fat-free mass suggesting that the treatment groups were statistically similar at baseline. In all three treatment groups subjects with above average compliance had significantly greater increases in BMD as compared to the two expected-change reference groups. The group following the most nutritionally comprehensive Plan outperformed the other two groups. For all three groups, there were no statistically significant differences between baseline and ending blood chemistry tests or the QOL self-reports.

CONCLUSIONS

The increases in BMD found in all three treatment groups in this CER stand in marked contrast to previous studies reporting that interventions with calcium and vitamin D(3) reduce age-related losses of BMD, but do not increase BMD. Increased compliance resulted in increased BMD levels. No adverse effects were found in the blood chemistry tests, self-reported quality of life and daily tracking reports. The Plans tested suggest a significant improvement over the traditional calcium and vitamin D(3) standard of care.

Strontium ranelate: a review of its use in the treatment of postmenopausal osteoporosis

This is a review of the pharmacology of strontium ranelate (Protelos, Protos, Protaxos, Bivalos, Osseor), and its efficacy and tolerability in the treatment of patients with postmenopausal osteoporosis. Strontium ranelate is a divalent strontium salt of ranelic acid that is capable of increasing bone formation and reducing bone resorption, thereby uncoupling and rebalancing bone turnover in favour of bone formation. The drug is effective in reducing the risk of fractures, including both vertebral and nonvertebral fractures, in patients with postmenopausal osteoporosis, according to data from two large, double-blind, placebo-controlled, multicentre trials of 5 years' duration, and reduced the risk of hip fracture in high-risk patients in a post hoc analysis of one trial. Moreover, data from patients who continued to receive the drug during the 3-year extension phases of these trials indicate that strontium ranelate continues to provide protection against new vertebral fractures and nonvertebral fractures for up to 8 years of therapy. It also improves bone mineral density at numerous sites and both increases markers of bone formation and decreases markers of bone resorption. Strontium ranelate is administered orally as a suspension and is generally well tolerated. The nature of adverse events was generally similar regardless of treatment duration in clinical trials, with the most commonly reported being nausea and diarrhoea over 5 years of treatment, and memory loss and diarrhoea during longer-term treatment. Although an increased risk of venous thromboembolism was associated with strontium ranelate relative to placebo over 5 years of treatment in a pooled analysis of clinical trials, postmarketing data have not confirmed this finding. Overall, the clinical data available suggest that strontium ranelate is an effective and generally well tolerated option for the first-line treatment of postmenopausal osteoporosis.

Receptor activator of nuclear factor-κB ligand and osteoprotegerin: maintaining the balance to prevent bone loss

Bone remodeling requires a precise balance between resorption and formation. It is a complex process that involves numerous factors: hormones, growth factors, vitamins, and cytokines, and notably osteoprotegerin (OPG) and receptor activator for nuclear factor-κB (RANK) ligand. The signaling pathway OPG/RANK/RANKL is key to regulation for maintaining the balance between the activity of osteoblasts and osteoclasts in order to prevent bone loss and ensure a normal bone turnover. In this review, the RANK/RANKL/OPG pathway is described. The multiple interactions of various factors (hormones, cytokines, growth factors, and vitamins) with the OPG/RANK/RANKL pathway are also commented on. Finally, the effects of denosumab, a human monoclonal antibody that binds to RANKL and thereby inhibits the activation of osteoclasts, and of strontium ranelate are also described. Indeed, these two new drugs afford appreciable assistance in daily care practice, helping to prevent bone loss in patients with osteoporosis.

Current and emerging therapies for the treatment of osteoporosis

Osteoporosis represents a weakening of bone tissue due to an imbalance in the dynamic processes of bone formation and bone resorption that are continually ongoing within bone tissue. Most currently available osteoporosis therapies are antiresorptive agents. Over the past decade, bisphosphonates, notably alendronate and risedronate, have become the dominant agents with newer bisphosphonates such as ibandronate and zoledronic acid following a trend of less frequent dosing regimens. Synthetic estrogen receptor modulators (SERMs) continue to be developed as drugs that maintain the bone-protective effects of estrogen while avoiding its associated adverse side effects. Currently available agents of this class include raloxifene, the only SERM available in the United States (US), and lasofoxifene and bazedoxifene, available in Europe. Calcitonin, usually administered as a nasal spray, completes the list of currently approved antiresorptive agents, while parathyroid hormone analogs represent the only anabolic agents currently approved in both the US and Europe. Strontium ranelate is an additional agent available in Europe but not the US that has both anabolic and antiresorptive activity. New agents expected to further expand therapeutic options include denosumab, a monoclonal antibody inhibitor of the resorptive enzyme cathepsin K, which is in the final stages of Food and Drug Administration approval. Other agents in preclinical development include those targeting specific molecules of the Wnt/β-catenin pathway involved in stimulating bone formation by osteoblast cells. This review discusses the use of currently available agents as well as highlighting emerging agents expected to bring significant changes to the approach to osteoporosis therapy in the near future.

Current, new and future treatments of osteoporosis

Osteoporosis as a common chronic disease is challenging human health. Although different therapeutic options are routinely used for prevention/treatment of osteoporosis, their side effects and benefits are under question. Increasing our knowledge about signaling pathways in bone and osteocytes as well as osteoblasts and osteoclasts will help us in designing new therapeutic modalities for osteoporosis. In the present study, all new therapeutic measures of osteoporosis have been reviewed. For this purpose, search engines like Pubmed, Web of Science, Scopus, Google Scholar were searched and all relevant articles were found. The study was limited to the year 1998-2010. Bisphosphonates are the cornerstone of osteoporosis treatment, but there are not enough relevant studies that investigated their equivalencies in comparison with each other or the other medications. Therefore, medication selection is empirical and subjective. Furthermore, no eminent study has compared certain combinations. There are new hopes for treatment of osteoporosis, which are more specific with less harm. Our results show that new and emerging therapies are more potent and target specified which more individualize osteoporosis treatment; however, more investigations on their safety and efficacy in comparison with current medications are highly recommended.

In osteoporotic women treated with strontium ranelate, strontium is located in bone formed during treatment with a maintained degree of mineralization

In postmenopausal osteoporotic women and up to 3 years of treatment with strontium ranelate, strontium was present only in recently deposited bone tissue resulting from formation activity during the period of treatment. Strontium was shown to be dose-dependently deposited into this newly formed bone with preservation of the mineralization.

INTRODUCTION

Interactions between strontium (Sr) and bone mineral and its effects on mineralization were investigated in women treated with strontium ranelate.

METHODS

Bone biopsies from osteoporotic women were obtained over 5-year strontium ranelate treatment from phases II and III studies. Bone samples obtained over 3-year treatment were investigated by X-ray microanalysis for bone Sr uptake and focal distribution, and by quantitative microradiography for degree of mineralization. On some samples, Sr distribution (X-ray cartography) was analyzed on whole sample surfaces and the percentage of bone surface containing Sr was calculated. Bone Sr content was chemically measured on whole samples.

RESULTS

In treated women, Sr was exclusively present in bone formed during treatment; Sr deposition depended on the dose with higher focal content in new bone structural units than in old ones constantly devoid of Sr, even after 3-year treatment. A plateau in global bone Sr content was reached after 3 years of treatment. Cartography illustrated the extent of surfaces containing Sr, and formation activity during strontium ranelate treatment was higher in cancellous than in cortical bone. Mineralization was maintained during treatment.

CONCLUSION

The quality of bone mineral was preserved after treatment with strontium ranelate, supporting the safety of this agent at the bone tissue level.

The cost-effectiveness of strontium ranelate in the UK for the management of osteoporosis

The cost-effectiveness of strontium ranelate was compared to no treatment in UK women using the FRAX algorithm for fracture risk assessment. At a willingness-to-pay of pound 30,000 per quality-adjusted life-year (QALY), strontium ranelate was generally cost-effective in women with prior fracture at the threshold of osteoporosis from an age of 65 years.

INTRODUCTION

The objectives of the study were to estimate the cost-effectiveness of strontium ranelate in the UK for the treatment of osteoporosis and to establish intervention thresholds for treatment using the FRAX tool.

METHODS

The cost-effectiveness of strontium ranelate was compared to no treatment in postmenopausal women with clinical risk factors for fracture using a lifetime simulation model based on Markov cohort methodology that incorporated the features of FRAX.

RESULTS

At a threshold of pound 30,000 per QALY, strontium ranelate was generally cost-effective in women from an age of 65 years with prior fracture at the threshold of osteoporosis (i.e., a T-score of -2.5 SD) and in women with a prior fracture (and no information on bone mineral density) from the age of 65 years. At a threshold of pound 20,000, strontium ranelate became cost-effective at a 10-year fracture probability of 25.7% and at 16.9% with a threshold of pound 30,000 for a QALY.

CONCLUSIONS

Strontium ranelate is a cost-effective agent for the treatment of established osteoporosis in women over the age of 65 years. Cost-effective scenarios were also found for the prevention and treatment of fractures associated with osteoporosis, in younger women with additional clinical risk factors.

Effects of long-term strontium ranelate treatment on vertebral fracture risk in postmenopausal women with osteoporosis

SUMMARY

Vertebral fractures are a major adverse consequence of osteoporosis. In a large placebo-controlled trial in postmenopausal women with osteoporosis, strontium ranelate reduced vertebral fracture risk by 33% over 4 years, confirming the role of strontium ranelate as an effective long-term treatment in osteoporosis.

INTRODUCTION

Osteoporotic vertebral fractures are associated with increased mortality, morbidity, and loss of quality-of-life (QoL). Strontium ranelate (2 g/day) was shown to prevent bone loss, increase bone strength, and reduce vertebral and peripheral fractures. The preplanned aim of this study was to evaluate long-term efficacy and safety of strontium ranelate.

METHODS

A total of 1,649 postmenopausal osteoporotic women were randomized to strontium ranelate or placebo for 4 years, followed by a 1-year treatment-switch period for half of the patients. Primary efficacy criterion was incidence of patients with new vertebral fractures over 4 years. Lumbar bone mineral density (BMD) and QoL were also evaluated.

RESULTS

Over 4 years, risk of vertebral fracture was reduced by 33% with strontium ranelate (risk reduction = 0.67, p < 0.001). Among patients with two or more prevalent vertebral fractures, risk reduction was 36% (p < 0.001). QoL, assessed by the QUALIOST(R), was significantly better (p = 0.025), and patients without back pain were greater (p = 0.005) with strontium ranelate than placebo over 4 years. Lumbar BMD increased over 5 years in patients who continued with strontium ranelate, while it decreased in patients who switched to placebo. Emergent adverse events were similar between groups.

CONCLUSION

In this 4- and 5-year study, strontium ranelate is an effective and safe treatment for long-term treatment of osteoporosis in postmenopausal women.

Strontium ranelate: new data on fracture prevention and mechanisms of action

Osteoporosis treatments need to combine an unequivocally demonstrated reduction of fractures, at various skeletal sites, long-term safety, and a user-friendly profile that optimizes therapeutic adherence. Strontium ranelate is the first compound to simultaneously decrease bone resorption and stimulate bone formation. Its anti-fracture efficacy at various skeletal sites has been established for as long as 5 years through studies of the highest methodological standards. Increases in bone mineral density observed after 1 year of treatment are predictive of the long-term fracture efficacy, suggesting for the first time in osteoporosis that bone densitometry can be used as a monitoring tool. Due to a positive risk/benefit ratio, strontium ranelate is now considered as a first-line treatment in the management of osteoporosis.

Osteoblasts play key roles in the mechanisms of action of strontium ranelate

BACKGROUND AND PURPOSE

Strontium ranelate reduces fracture risk in postmenopausal women with osteoporosis. Evidence from non-clinical studies and analyses of bone markers in phase III trials indicate that this is due to an increase in osteoblast formation and a decrease of osteoclastic resorption. The aim of this work was to investigate, in human cells, the mechanisms by which strontium ranelate is able to influence the activities of osteoblasts and osteoclasts.

EXPERIMENTAL APPROACH

Human primary osteoblasts were used to examine effects of strontium ranelate on replication (thymidine incorporation), differentiation (Runx2 and alkaline phosphatase) and cell survival (cell counts and caspase activity). Osteoprotegerin (OPG) was measured by quantitative reverse transcription PCR (qRT-PCR) and elisa and receptor activator of NFkappaB ligand (RANKL) by qRT-PCR and Western blot. As strontium ranelate has been proposed as an agonist of the calcium-sensing receptor (CaSR), the involvement of CaSR in the effects of strontium ranelate on OPG and RANKL expression, and cell replication was examined using siRNA.

KEY RESULTS

Strontium ranelate increased mRNA and protein levels of OPG and suppressed those of RANKL. Strontium ranelate also stimulated osteoblast replication and differentiation and increased cell survival under stress. Knocking down CaSR suppressed strontium ranelate-induced stimulation of OPG mRNA, reduction of RANKL mRNA, and increase in replication, indicating the involvement of CaSR in these responses.

CONCLUSIONS AND IMPLICATIONS

Our results demonstrate that osteoblasts play a key role in the mechanism of action of the anti-fracture agent, strontium ranelate by mediating both its anabolic and anti-resorptive actions, at least in part, via activation of CaSR.

Denosumab in postmenopausal osteoporosis: what the clinician needs to know

Denosumab is a subcutaneously (SC) administered investigational fully human monoclonal antibody to receptor activator of nuclear factor-kB ligand (RANKL), a cytokine member of the tumor necrosis factor family that is the principal mediator of osteoclastic bone resorption. RANKL stimulates the formation, activity, and survival of osteoclasts, and is implicated in the pathogenesis of postmenopausal osteoporosis and other skeletal disorders associated with increased bone remodeling. Denosumab binds RANKL, preventing it from binding to RANK, thereby reducing the formation, activity, and survival of osteoclasts and slowing the rate of bone resorption. Postmenopausal women with low bone mineral density (BMD) treated with denosumab have a reduction of bone turnover markers and an increase in BMD that is rapid, sustained, and reversible. In postmenopausal women with osteoporosis, denosumab reduces the risk of vertebral, hip, and nonvertebral fractures. In postmenopausal women with low BMD randomized to receive denosumab or alendronate, denosumab is associated with a significantly greater increase in BMD and further reduction in bone turnover markers compared with alendronate. In postmenopausal women with low BMD who were previously treated with alendronate, those who switched to denosumab have a significantly greater BMD increase and further reduction in bone turnover markers compared with those continuing alendronate. Denosumab is well tolerated with a favorable safety profile. It is a promising emerging drug for the prevention and treatment of osteoporosis, offering a long dosing interval of every 6 months and convenient SC dosing, with the potential of improving long-term adherence to therapy compared with current oral treatments.

Clinical challenges in the management of osteoporosis

While knowledge regarding the diagnosis and treatment of osteoporosis has expanded dramatically over the last few years, gaps in knowledge still exist with guidance lacking on the appropriate management of several common clinical scenarios. This article uses fictional clinical scenarios to help answer three challenging questions commonly encountered in clinical practice. The first clinical challenge is when to initiate drug therapy in a patient with low bone density. It is estimated that 34 million America have low bone density and are at a higher risk for low trauma fractures. Limitations of using bone mineral density alone for drug therapy decisions, absolute risk assessment and evidence for the cost-effectiveness of therapy in this population are presented. The second clinical challenge is the prevention and treatment of vitamin D deficiency. Appropriate definitions for vitamin D insufficiency and deficiency, the populations at risk for low vitamin, potential consequences of low vitamin D, and how to manage a patient with low vitamin D are reviewed. The third clinical challenge is how to manage a patient receiving drug therapy for osteoporosis who has been deemed a potential treatment failure. How to define treatment failure, common causes of treatment failure, and the approach to the management of a patient who is not responding to appropriate osteoporosis therapy are discussed.

The effect of the microscopic and nanoscale structure on bone fragility

Bone mineral density is the gold-standard for assessing bone quantity and diagnosing osteoporosis. Although bone mineral density measurements assess the quantity of bone, the quality of the tissue is an important predictor of fragility. Understanding the macro- and nanoscale properties of bone is critical to understanding bone fragility in osteoporosis. Osteoporosis is a disease that affects more than 75 million people worldwide. The gold standard for osteoporosis prognosis, bone mineral density, primarily measures the quantity of bone in the skeleton, overlooking more subtle aspects of bone's properties. Bone quality, a measure of bone's architecture, geometry and material properties, is evaluated via mechanical, structural and chemical testing. Although decreased BMD indicates tissue fragility at the clinical level, changes in the substructure of bone can help indicate how bone quality is altered in osteoporosis. Additionally, mechanical properties which can quantify fragility, or bone's inability to resist fracture, can be changed due to alterations in bone architecture and composition. Recent studies have focused on examination of bone on the nanoscale, suggesting the importance of understanding the interactions of the mineral crystals and collagen fibrils and how they can alter bone quality. It is therefore important to understand alterations in bone that occur at the macro-, micro- and nanoscopic levels to determine what parameters contribute to decreased bone quality in diseased tissue.

Considerations for development of surrogate endpoints for antifracture efficacy of new treatments in osteoporosis: a perspective

Because of the broad availability of efficacious osteoporosis therapies, conduct of placebo-controlled trials in subjects at high risk for fracture is becoming increasing difficult. Alternative trial designs include placebo-controlled trials in patients at low risk for fracture or active comparator studies, both of which would require enormous sample sizes and associated financial resources. Another more attractive alternative is to develop and validate surrogate endpoints for fracture. In this perspective, we review the concept of surrogate endpoints as it has been developed in other fields of medicine and discuss how it could be applied in clinical trials of osteoporosis. We outline a stepwise approach and possible study designs to qualify a biomarker as a surrogate endpoint in osteoporosis and review the existing data for several potential surrogate endpoints to assess their success in meeting the proposed criteria. Finally, we suggest a research agenda needed to advance the development of biomarkers as surrogate endpoints for fracture in osteoporosis trials. To ensure optimal development and best use of biomarkers to accelerate drug development, continuous dialog among the health professionals, industry, and regulators is of paramount importance.

Comparative effects of antiresorptive agents on bone mineral density and bone turnover in postmenopausal women

Postmenopausal osteoporosis is a common clinical entity; its complications represent a significant burden to society. In recent years the choice of therapies available for the treatment of postmenopausal osteoporosis has increased dramatically. There are a number of antiresorptive agents currently available including hormone replacement therapy (HRT), selective estrogen receptor modulators (SERMs), bisphosphonates, and dual action bone agents. It is difficult to truly compare these therapies given the lack of direct head-to head studies. The efficacy of antiresorptive therapies can be assessed in a number of ways including measurement of bone mineral density (BMD), assessment of bone turnover markers, and fracture reduction. Other important factors include ease of administration and consequent patient compliance. This article reviews the currently available antiresorptive agents and their effects on the above outcome measures.

Cancer treatment-related bone loss: a review and synthesis of the literature

Cancer therapy can result in significant bone loss and increased risk of fragility fracture. Chemotherapy, aromatase inhibitors, and gonadotropin-releasing hormone analogues contribute to increases in the rate of bone remodelling and reduce bone mineral density. Patients with prostate cancer on androgen deprivation therapy experience an increase in the risk of fracture. New research has demonstrated the key role played by bisphosphonates in preventing declines in bone density and increases in bone remodelling. Novel antiresorptive agents targeting receptor activator of nuclear factor κB ligand have great potential in skeletal protection and prevention of bone loss related to cancer therapy. Early assessment of skeletal health, followed by initiation of calcium, vitamin D, and an exercise program are valuable in the prevention and treatment of osteoporosis. In addition, individuals at increased risk for fracture should be offered antiresorptive therapy. Early data have demonstrated that bisphosphonates are able to prevent the bone loss and increased bone remodelling associated with cancer therapy, including aromatase inhibition and androgen deprivation therapy. The present paper reviews the new research and advances in the management of bone loss associated with both cancer therapy and estrogen deficiency in the postmenopausal female.

Effects of parathyroid hormone alone or in combination with antiresorptive therapy on bone mineral density and fracture risk--a meta-analysis

AIM

The effects of parathyroid hormone (PTH) alone or in combination with antiresorptive therapy on changes in bone mineral density (BMD) and fracture risk were studied.

MATERIALS AND METHODS

Randomised placebo controlled trials were retrieved from the PubMed, Web of Science or Embase databases.

RESULTS

PTH alone or in combination with antiresorptive drugs reduced vertebral [relative risk (RR)=0.36, 95% confidence interval (CI): 0.28-0.47, 2p<0.01] and non-vertebral (RR=0.62, 95% CI: 0.48-0.82, 2p<0.01) fracture risk and increased spine BMD by 6.6% (95% CI: 5.2-8.1%, 2p<0.01) and hip BMD non-significantly by 1.0% (95% CI: -0.1 to 2.1%, 2p=0.08) during 11-36 months of follow-up (13 trials). The gain in spine and hip BMD tended to increase with the length of the PTH treatment. No significant effect of study duration on fracture risk could be demonstrated. The major adverse events were hypercalcaemia, nausea and discomfort at the injection sites. Only limited data are currently available on fracture risk reduction with PTH plus antiresorptive therapies.

CONCLUSION

Although the number of studies on non-vertebral fractures is limited, our pooled analysis revealed that PTH alone or in combination with antiresorptive drugs would appear to be able to reduce the risk of vertebral and non-vertebral fractures and to increase spine and perhaps hip BMD. However, these analyses were based on cross-sectional data--i.e. based on indirect comparisons--and further studies with a direct comparison of study duration are necessary. No studies comparing PTH, PTH plus antiresorptive drugs and antiresorptive drug versus placebo in a factorial design are available; consequently, we were unable to draw any conclusions on the superiority of PTH plus antiresorptive drug versus antiresorptive drug or PTH alone with respect to BMD or fractures.

Strontium ranelate for preventing and treating postmenopausal osteoporosis

BACKGROUND

Strontium ranelate is a new treatment for osteoporosis therefore, its benefits and harms need to be known.

OBJECTIVES

To determine the efficacy and safety of strontium ranelate for the treatment and prevention of postmenopausal osteoporosis.

SEARCH STRATEGY

We searched MEDLINE (1996 to March 2005), EMBASE (1996 to week 9 2005), the Cochrane Library (1996 to Issue 1 2005), reference lists of relevant articles and conference proceedings from the last two years. Additional data was sought from authors.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) of at least one year duration comparing strontium ranelate versus placebo reporting fracture incidence, bone mineral density (BMD), health related quality of life or safety in postmenopausal women. Treatment (versus prevention) population was defined as women with prevalent vertebral fractures and/or lumbar spine BMD T score < -2.5 SD.

DATA COLLECTION AND ANALYSIS

Two reviewers independently determined study eligibility, assessed trial quality and extracted the relevant data. Disagreements were resolved by consensus. RCTs were grouped by dose of strontium ranelate and treatment duration. Where possible, meta-analysis was conducted using the random effects model.

MAIN RESULTS

Four trials met the inclusion criteria. Three included a treatment population (0.5 to 2 g of strontium ranelate daily) and one a prevention population (0.125 g, 0.5 g and 1 g daily). A 37% reduction in vertebral fractures (RR 0.63, 95% CI 0.56, 0.71) and a 14% reduction in non-vertebral fractures (RR 0.86, 95% CI 0.75, 0.98) were demonstrated over three years with 2 g of strontium ranelate daily in a treatment population. An increase in BMD was shown at all BMD sites after two to three years in both populations. Lower doses of strontium ranelate were superior to placebo and the highest dose demonstrated the greatest reduction in vertebral fractures and increase in BMD. An increased risk of diarrhea with 2 g of strontium ranelate was found; however, adverse events did not affect the risk of discontinuing treatment nor did it increase the risk of serious side effects, gastritis or death. Additional data suggests that the risk of vascular and nervous system side-effects is slightly increased with taking 2 g of strontium ranelate daily over three to four years.

AUTHORS' CONCLUSIONS

There is silver level evidence (www.cochranemsk.org) to support the efficacy of strontium ranelate for the reduction of fractures (vertebral and to a lesser extent non-vertebral) in postmenopausal osteoporotic women and an increase in BMD in postmenopausal women with/without osteoporosis. Diarrhea may occur however, adverse events leading to study withdrawal were not significantly increased with taking 2 g of strontium ranelate daily. Potential vascular and neurological side-effects need to be further explored.

Strontium ranelate--data on vertebral and nonvertebral fracture efficacy and safety: mechanism of action

Strontium ranelate is a novel therapy for the treatment of postmenopausal osteoporosis with actions to reduce bone resorption and increase bone formation. In vitro, strontium ranelate has anabolic and antiresorptive activity, increasing collagen and non-collagen protein synthesis, enhancing pre-osteoblast differentiation, inhibiting osteoclast differentiation, and reducing osteoclast function. In animal models, the increase in bone density is closely correlated with increases in biomechanical bone strength. Histomorphometry demonstrates reduced osteoclast surfaces with increased bone formation. Clinical trials in postmenopausal women have demonstrated 3-year fracture efficacy. Reductions in vertebral fracture were seen in patients with and without prevalent vertebral fracture. Nonvertebral fractures were also significantly reduced. In a subgroup of patients at high risk for hip fracture, there was a significant reduction in hip fracture risk. Strontium ranelate is well tolerated with nausea, diarrhea, headache, and dermatitis more frequent in treated patients only for the first 3 months of therapy. Together, these data suggest that strontium ranelate is a well-tolerated and effective therapy for postmenopausal osteoporosis reducing vertebral and nonvertebral fracture by a novel dual antiresorptive and anabolic action on bone.

Strontium ranelate: a novel treatment for postmenopausal osteoporosis: a review of safety and efficacy

Strontium ranelate is a new orally administered agent for the treatment of women with postmenopausal osteoporosis that reduces the risk of vertebral and hip fractures. Evidence for the safety and efficacy of strontium ranelate comes from two large multinational trials, the SOTI (Spinal Osteoporosis Therapeutic Intervention) and TROPOS (Treatment Of Postmenopausal Osteoporosis) studies. The SOTI study evaluated vertebral fracture prevention in 1649 postmenopausal women with a mean age of 69 y. The subjects all had at least one previous vertebral fracture and a low spine bone mineral density (BMD) (equivalent to a Hologic spine T-score below -1.9). The strontium ranelate group had a 41% lower risk of a new vertebral fracture than the placebo group over the three-year study period (relative risk [RR] = 0.59; 95% confidence interval [CI]: 0.48-0.73; p < 0.001). The TROPOS study evaluated non-vertebral fracture prevention in 5091 postmenopausal women with a mean age of 77 y. The subjects were aged 74 y and over (or 70-74 y with one additional risk factor) and a low femoral neck BMD (equivalent to an NHANES III [Third National Health and Nutrition Examination Survey] T-score below -2.2). Over the three-year study period there was a 16% reduction in all non-vertebral fractures (RR = 0.84; 95% CI 0.702-0.995; p = 0.04) and a 19% reduction at the principal sites for non-vertebral fractures. The TROPOS study was not powered to investigate hip fracture risk. However, in a high risk group of women aged 74 y and over and with an NHANES III femoral neck T-score less than -2.4 there was a 36% reduction in hip fracture risk (RR = 0.64; 95% CI: 0.412-0.997; p = 0.046). The overall incidence of adverse events did not differ significantly from placebo and were generally mild and transient, the most common being nausea and diarrhea. Strontium ranelate is a useful addition to the range of anti-fracture treatments available for treating postmenopausal women with osteoporosis and is the only treatment proven to be effective at preventing both vertebral and hip fractures in women aged 80 y and over.

Medical treatment of vertebral osteoporosis

Although osteoporosis is a systemic disease, vertebral fractures due to spinal bone loss are a frequent, sometimes early and often neglected complication of the disease, generally associated with considerable disability and pain. As osteoporotic vertebral fractures are an important predictor of future fracture risk, including at the hip, medical management is targeted at reducing fracture risk. A literature search for randomized, double-blind, prospective, controlled clinical studies addressing medical treatment possibilities of vertebral fractures in postmenopausal Caucasian women was performed on the leading medical databases. For each publication, the number of patients with at least one new vertebral fracture and the number of randomized patients by treatment arm was retrieved. The relative risk (RR) and the number needed to treat (NNT, i.e. the number of patients to be treated to avoid one radiological vertebral fracture over the duration of the study), together with the respective 95% confidence intervals (95%CI) were calculated for each study. Treatment of steroid-induced osteoporosis and treatment of osteoporosis in men were reviewed separately, based on the low number of publications available. Forty-five publications matched with the search criteria, allowing for analysis of 15 different substances tested regarding their anti-fracture efficacy at the vertebral level. Bisphosphonates, mainly alendronate and risedronate, were reported to have consistently reduced the risk of a vertebral fracture over up to 50 months of treatment in four (alendronate) and two (risedronate) publications. Raloxifene reduced vertebral fracture risk in one study over 36 months, which was confirmed by 48 months' follow-up data. Parathormone (PTH) showed a drastic reduction in vertebral fracture risk in early studies, while calcitonin may also be a treatment option to reduce fracture risk. For other substances published data are conflicting (calcitriol, fluoride) or insufficient to conclude about efficacy (calcium, clodronate, etidronate, hormone replacement therapy, pamidronate, strontium, tiludronate, vitamin D). The low NNTs for the leading substances (ranges: 15-64 for alendronate, 8-26 for risedronate, 23 for calcitonin and 28-31 for raloxifene) confirm that effective and efficient drug interventions for treatment and prevention of osteoporotic vertebral fractures are available. Bisphosphonates have demonstrated similar efficacy in treatment and prevention of steroid-induced and male osteoporosis as in postmenopausal osteoporosis. The selection of the appropriate drug for treatment of vertebral osteoporosis from among a bisphosphonate (alendronate or risedronate), PTH, calcitonin or raloxifene will mainly depend on the efficacy, tolerability and safety profile, together with the patient's willingness to comply with a long-term treatment. Although reduction of vertebral fracture risk is an important criterion for decision making, drugs with proven additional fracture risk reduction at all clinically relevant sites (especially at the hip) should be the preferred options.