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

Biofabrication of Gingival Fibroblast Cell-Laden Collagen/Strontium-Doped Calcium Silicate 3D-Printed Bi-Layered Scaffold for Osteoporotic Periodontal Regeneration

Periodontal disease is a chronic disease that can lead to lose teeth and even tooth loss if left untreated. Osteoporosis and periodontal disease share similar characteristics and associated factors. Current regenerative techniques for periodontal diseases are ineffective in restoring complete function and structural integrity of periodontium due to unwanted migration of cells. In this study, we applied the concept of guided tissue regeneration (GTR) and 3D fabricated gingival fibroblast cell-laden collagen/strontium-doped calcium silicate (SrCS) bi-layer scaffold for periodontal regeneration. The results revealed that the bioactive SrCS had a hydroxyapatite formation on its surface after 14 days of immersion and that SrCS could release Sr and Si ions even after 6 months of immersion. In addition, in vitro results showed that the bi-layer scaffold enhanced secretion of FGF-2, BMP-2, and VEGF from human gingival fibroblasts and increased secretion of osteogenic-related proteins ALP, BSP, and OC from WJMSCs. In vivo studies using animal osteoporotic models showed that the 3D-printed cell-laden collagen/SrCS bi-layer scaffold was able to enhance osteoporotic bone regeneration, as seen from the increased Tb.Th and BV/TV ratio and the histological stains. In conclusion, it can be seen that the bi-layer scaffolds enhanced osteogenesis and further showed that guided periodontal regeneration could be achieved using collagen/SrCS scaffolds, thus making it a potential candidate for future clinical applications.

Effect of Strontium Substitution on the Physicochemical Properties and Bone Regeneration Potential of 3D Printed Calcium Silicate Scaffolds

In this study, we synthesized strontium-contained calcium silicate (SrCS) powder and fabricated SrCS scaffolds with controlled precise structures using 3D printing techniques. SrCS scaffolds were shown to possess increased mechanical properties as compared to calcium silicate (CS) scaffolds. Our results showed that SrCS scaffolds had uniform interconnected macropores (~500 µm) with a compressive strength 2-times higher than that of CS scaffolds. The biological behaviors of SrCS scaffolds were assessed using the following characteristics: apatite-precipitating ability, cytocompatibility, proliferation, and osteogenic differentiation of human mesenchymal stem cells (MSCs). With CS scaffolds as controls, our results indicated that SrCS scaffolds demonstrated good apatite-forming bioactivity with sustained release of Si and Sr ions. The in vitro tests demonstrated that SrCS scaffolds possessed excellent biocompatibility which in turn stimulated adhesion, proliferation, and differentiation of MSCs. In addition, the SrCS scaffolds were able to enhance MSCs synthesis of osteoprotegerin (OPG) and suppress macrophage colony-stimulating factor (M-CSF) thus disrupting normal bone homeostasis which led to enhanced bone formation over bone resorption. Implanted SrCS scaffolds were able to promote new blood vessel growth and new bone regeneration within 4 weeks after implantation in critical-sized rabbit femur defects. Therefore, it was shown that 3D printed SrCS scaffolds with specific controllable structures can be fabricated and SrCS scaffolds had enhanced mechanical property and osteogenesis behavior which makes it a suitable potential candidate for bone regeneration.

Synthesis of trace element Si and Sr codoping hydroxyapatite with non-cytotoxicity and enhanced cell proliferation and differentiation

The main inorganic minerals in natural bones are non-stoichiometric hydroxyapatite (HA, Ca₁₀[PO₄]₆[OH]₂) doped with various trace elements, which may possess important biochemical effects. To investigate the functions of Sr and Si elements in human hard tissues, non-doped HA, trace Si doped HA, Si and Sr codoped HA with the concentration of natural bones are synthesized by hydrothermal method in this study. The samples are characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM). The biological activities are evaluated via cytotoxicity study, adhesion and proliferation of osteoblast measurement, and alkaline phosphatase (ALP) assay. All the synthesized materials are HA phase, which have hierarchical structures with oriented HA nanorods assembled into the platy particles. These materials are non-cytotoxic against L929 cells line even at 400 μg/ml powder suspension. The results clearly indicate that the proliferation of L929 cells increases with trace elements doping from trace Si-HA to Si + Sr-HA. The adhesion and proliferation of osteoblast measurement illustrates that proliferation of osteoblasts advances about 1.3 times for Si-HA and about 1.8 times for Si + Sr-HA compared with undoped HA. In general, Si-HA with trace Si element shows enhanced cell differentiation, and Si + Sr-HA dual-doped with Si and Sr elements presents increased biological activity compared with Si-HA.

A comparative study of strontium-substituted hydroxyapatite coating on implant's osseointegration for osteopenic rats

Surface modification techniques have been applied to generate titanium implant surfaces that promote osseointegration for the implants in cementless arthroplasty. However, its effect is not sufficient for osteoporotic bone. Strontium (Sr) promotes osteoblast proliferation and inhibits osteoclast proliferation and positively affects bone regeneration. The aim of this study was to confirm the effects of strontium-substituted hydroxyapatite (Sr-HA) coating via electrochemical deposition on implant's osseointegration in the osteoporotic condition. Female Sprague Dawley rats were used for this study. Twelve weeks after bilateral ovariectomy, all animals were randomly divided into four groups: group HA; group 5 % Sr-HA; group 10 % Sr-HA; and group 20 % Sr-HA. Afterward, all rats from groups HA, 5 % Sr-HA, 10 % Sr-HA, and 20 % Sr-HA received implants with hydroxyapatite coating containing 0, 5, 10, and 20 % Sr. Implants were inserted bilaterally in all animals until death at 12 weeks. The bilateral femurs of rats were harvested for evaluation. All treatment groups increased new bone formation around the surface of titanium rods and push-out force; group 20 % Sr-HA showed the strongest effects on new bone formation and biomechanical strength. Additionally, these are significant differences in bone formation and push-out force was observed between groups 5 % Sr-HA and 10 % Sr-HA. This finding suggests that Sr-HA coating can improve implant osseointegration, and the 20 % Sr coating exhibited the best properties for implant osseointegration among the tested coatings in osteoporosis rats.

A comparative study of Sr-incorporated mesoporous bioactive glass scaffolds for regeneration of osteopenic bone defects

Recently, the use of the pharmacological agent strontium ranelate has come to prominence for the treatment of osteoporosis. While much investigation is focused on preventing disease progression, here we fabricate strontium-containing scaffolds and show that they enhance bone defect healing in the femurs of rats induced by ovariectomy.

INTRODUCTION

Recently, the use of the pharmacological agent strontium ranelate has come to prominence for the treatment of osteoporosis due to its ability to prevent bone loss in osteoporotic patients. Although much emphasis has been placed on using pharmacological agents for the prevention of disease, much less attention has been placed on the construction of biomaterials following osteoporotic-related fracture. The aim of the present study was to incorporate bioactive strontium (Sr) trace element into mesoporous bioactive glass (MBG) scaffolds and to investigate their in vivo efficacy for bone defect healing in the femurs of rats induced by ovariectomy.

METHODS

In total, 30 animals were divided into five groups as follows: (1) empty defect (control), (2) empty defects with estrogen replacement therapy, (3) defects filled with MBG scaffolds alone, (4) defects filled with MBG + estrogen replacement therapy, and (5) defects filled with strontium-incorporated mesopore-bioglass (Sr-MBG) scaffolds.

RESULTS

The two groups demonstrating the highest levels of new bone formation were the defects treated with MBG + estrogen replacement therapy and the defects receiving Sr-MBG scaffolds as assessed by μ-CT and histological analysis. Furthermore, Sr scaffolds had a reduced number of tartrate-resistant acid phosphatase-positive cells when compared to other modalities.

CONCLUSION

The results from the present study demonstrate that the local release of Sr from bone scaffolds may improve fracture repair. Future large animal models are necessary to investigate the future relationship of Sr incorporation into biomaterials.

Strontium-substituted, luminescent and mesoporous hydroxyapatite microspheres for sustained drug release

The multifunctional strontium (Sr)-substituted hydroxyapatite microsphere was prepared via hydrothermal method, in which the luminescent and controlled drug release functions can be realized. The structure and morphology of the as-prepared microspheres were studied by using XRD, FTIR, SEM, TEM, HR-TEM, BET method. The optical properties was investigated by using photoluminescence (PL) and XPS measurement. Then, the as-prepared multifunctional microspheres were performed as a drug delivery carrier using vancomycin as a model drug. The experimental results show that the composition, morphology, luminescent properties and drug storage/release behaviour were obviously influenced by the amount of Sr. The microspheres with Sr(2+)/(Ca(2+) + Sr(2+)) = 0.3 of Sr substitution showed the maximum specific surface area, best pore structure and strongest PL intensity. All the samples presented remarkable sustained drug release kinetics. In addition, the PL intensity of SrHA in the drug delivery system increased with the cumulative release time (amount) of vancomycin, which would make the drug release might be possibly tracked by the change of the luminescent intensity. Our study indicated a potential prospect that the fabricated multifunctional SrHA mesoporous microspheres might be applied in the field of bone regeneration and drug delivery.

Pharmacogenetics of osteoporosis-related bone fractures: moving towards the harmonization and validation of polymorphism diagnostic tools

Osteoporosis is one of the most common skeletal chronic conditions in developed countries, hip fracture being one of its major healthcare outcomes. There is considerable variation in the implementation of current pharmacological treatment and prevention, despite consistent recommendations and guidelines. Many studies have reported conflicting findings of genetic associations with bone density and turnover that might predict fracture risk. Moreover, it is not clear whether genetic differences exist in relation to the morbidity and efficiency of the pharmacotherapy treatments. Clinical response, including beneficial and adverse events associated with osteoporosis treatments, is highly variable among individuals. In this context, the present article intends to summarize putative candidate genes and genome-wide association studies that have been related with BMD and fracture risk, and to draw the attention to the need for pharmacogenetic methodology that could be applicable in clinical translational research after an adequate validation process. This article mainly compiles analysis of important polymorphisms in osteoporosis documented previously, and it describes the simple molecular biology tools for routine genotype acquisition. Validation of methods for the easy, fast and accessible identification of SNPs is necessary for evolving pharmacogenetic diagnostic tools in order to contribute to the discovery of clinically relevant genetic variation with an impact on osteoporosis and its personalized treatment.

The incorporation of strontium and zinc into a calcium-silicon ceramic for bone tissue engineering

In this study we developed novel scaffolds through the controlled substitution and incorporation of strontium and zinc into a calcium-silicon system to form Sr-Hardystonite (Sr-Ca(2)ZnSi(2)O(7), Sr-HT). The physical and biological properties of Sr-HT were compared to Hardystonite (Ca(2)ZnSi(2)O(7)) [HT]. We showed that Sr-HT scaffolds are porous with interconnected porous network (interconnectivity: 99%) and large pore size (300-500 microm) and an overall porosity of 78%, combined with a relatively high compressive strength (2.16+/-0.52 MPa). These properties are essential for enhancing bone ingrowth in load-bearing applications. Sr-HT ceramic scaffolds induced the attachment and differentiation of human bone derived cells (HOB), compared to that for the HT scaffolds. Sr-HT scaffolds enhanced expression of alkaline phosphatase, Runx-2, osteopontin, osteocalcin and bone sialoprotein. The in vivo osteoconductivity of the scaffolds was assessed at 3 and 6 weeks following implantation in tibial bone defects in rats. Histological staining revealed rapid new growth of bone into the pores of the 3D scaffolds with the Sr-HT and HT, relative to the beta-tricalcium phosphate (beta-TCP). In vivo, HT and Sr-HT produced distinct differences in the patterns of degradation of the materials, and their association with TRAP positive osteoclast-like cells with HT appearing more resistant compared to both Sr-HT and beta-TCP.

The morphology and lattice structure of bone crystal after strontium treatment in goats

Strontium (Sr) compounds have become increasingly popular in osteoporosis treatment. As a bone seeking element, 98% of Sr deposits in bone and teeth after oral ingestion. However, the quality of new bone after Sr deposition is yet to be extensively investigated. In this study, eight osteopenic goats were divided into two groups: Ca + 40Sr (five goats) and controls (three goats). Controls were fed with low calcium feeds. Ca phosphate was supplied at 100 mg/(kg day), and Sr phosphate at 40 mg/(kg day) in the Ca + 40Sr group. The newly formed bone at the outer cortical area of the femur with Sr deposition was identified from tetracycline labels, and the morphology and lattice structure of the crystals in these regions were investigated. Results showed that Sr concentrations of bone tissue significantly increased 144.37% for Sr administration without significant change in Ca concentration, and the ingested Sr mainly deposited in new bone. The crystal isolated from new bone exhibited the typical character of biological apatite as determined by Fourier transform infrared spectroscopy and selected-area electron diffraction. Transmission electron microscopy examination showed that a crystal with width of 8-10 nm grew along with the (002) lattice and aligned with the same direction in both groups. The elemental analysis of crystals showed that the ingested Sr deposited mainly in the bone matrix or was absorbed on the bone crystal surface, while only a limited amount of Sr replaced Ca in apatite crystals. Our findings showed that Sr administration at current dosages for prevention and treatment of osteoporosis might not change the bone crystal morphology and structure.

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.

Monitoring strontium ranelate therapy in patients with osteoporosis

PURPOSE

The purpose of this study was to review the monitoring of strontium ranelate osteoporosis therapy.

METHODS

The method used in this study was comprehensive literature review with clinical perspectives.

RESULTS

Changes in bone turnover markers (BTM) or bone mineral density (BMD) have been documented in osteoporosis clinical trials. However, neither BMD nor BTM changes fully explain the observed fracture risk reduction in treated patients. If changes in BMD or BTM on therapy would be easily discernable in individual patients, and were strongly associated with fracture risk reduction, monitoring individuals would be more useful. BMD changes in patients on strontium ranelate are of a greater magnitude and hence can be easily determined in an individual patient. In addition, there exists a better correlation between fracture risk reduction and increases in BMD.

CONCLUSIONS

The strong correlation between measured BMD increases and fracture risk reduction in patients on strontium ranelate therapy will be of clinical benefit to physicians wishing to evaluate both treatment persistence and fracture risk reduction.

Strontium ranelate: the first agent of a new therapeutic class in osteoporosis

Strontium ranelate is a new agent developed for the management of post-menopausal osteoporosis. It has a unique mode of action, based on an uncoupling between bone formation (increased) and bone resorption (decreased). To review its effectiveness we searched the MEDLINE database from 1985 to 2008, as well as databases such as the Cochrane controlled register, for citations or relevant articles. After this extensive search of the literature, a critical appraisal of the data was obtained through a consensus meeting (AN, MH, SS, OB, and J-YR). We found that strontium ranelate reduces vertebral, nonvertebral, major nonvertebral, and hip fractures over 1, 3, 4, and 5 years. Its spectrum of activity covers women with osteopenia, osteoporosis, and severe osteoporosis. Elderly subjects also show a reduction in vertebral and nonvertebral fractures. Bone mineral density may be used as a monitoring tool for strontium ranelate, since early changes are predictive of long-term fracture reduction. Biochemical markers of bone turnover reflect the uncoupling between resorption and formation. The safety profile of strontium ranelate compares favorably with the other currently marketed antiosteoporosis medications. Preliminary results suggest that strontium ranelate is able to reduce the progression of spine osteoarthritis. In conclusion, strontium ranelate has the potential to be a candidate for first-line treatment of osteopenia and osteoporosis. However, further research is needed before suggesting its widespread use in osteoarthritis.

[Metabolic bone diseases]

Osteomalacia is caused by impaired vitamin D receptor (VDR) signaling, calcium deficiency, and altered bone mineralization. This can be due to insufficient sunlight exposure, malabsorption, reduced D hormone activation in chronic kidney disease, and rare alterations of VDR signaling and phosphate metabolism. Leading symptoms are bone pain, muscular cramps, and increased incidence of falls in the elderly. The adequate respective countermeasures are to optimize the daily intake of calcium and vitamin D3 and to replace active D hormone and phosphate if deficient. Osteoporosis is characterized by bone fragility fractures upon minor physical impact. Indications for diagnosis and treatment can be established by estimating the absolute fracture risk, taking into account bone mineral density, age, gender, and individual risk factors. Exercise, intervention programs to avoid falls, and specific drugs are capable of substantially reducing fracture risk even in the elderly. Secondary osteoporosis primarily requires both bone-altering medications and effective treatment of underlying diseases.

Alendronate has an anabolic effect on bone through the differentiation of mesenchymal stem cells

We committed MSCs to differentiate into either osteoblasts or adipocytes and examined the effect of ALN on both adipogenesis and osteoblastogenesis. ALN inhibited adipogenesis while promoting osteoblast differentiation and activity. Our results reveal a new anabolic effect of ALN in differentiating bone marrow cells.

INTRODUCTION

Alendronate (ALN) prevents bone loss in postmenopausal patients through the regulation of osteoclastic activity. However, it has also proven to be effective in older adults where the pathophysiological mechanism is the predominance of adipogenesis over osteoblastogenesis. The aim of this study is to determine the in vitro effect of ALN on both osteoblastogenesis and adipogenesis.

MATERIALS AND METHODS

Human mesenchymal stem cells (MSCs) were plated at a density of 5 x 10(5) cells/well in 100-cm2 dishes containing MSC growth media. After confluence, cells were committed to differentiate adding either adipogenic or osteogenic media with and without 1,25(OH)2D3 (10(-8) M) and supplemented with ALN at increasing concentrations (10(-9) to 10(-7) M). Untreated differentiating MSCs were used as control. Alkaline phosphatase (ALP), oil red O, and Alizarin red staining were performed at timed intervals (weeks 1 and 2). Additionally, levels of expression of both osteogenesis and adipogenesis transcription factors were measured in protein extracts. Finally, the effect of ALN on PPARgamma2 nuclear activation complex was assessed.

RESULTS

We found that ALN has a significant and dose-dependent effect on osteoblastogenesis. This effect was not modified by the presence of 1,25(OH)2D3 in the medium. Furthermore, adipogenic differentiation of MSCs was affected by addition of both ALN and 1,25(OH)2D3 to the media as confirmed by phenotype changes and lower number of lipid droplets. Finally, expression of adipogenic transcription factors and PPARgamma2 activation were reduced in adipose differentiating MSCs treated with either ALN or ALN + 1,25(OH)2D3.

CONCLUSIONS

This study shows a potential anabolic effect of ALN in vitro through the stimulation of osteogenic differentiation of MSCs. Additionally, a previously unknown inhibitory effect of ALN on bone marrow adipogenesis was also found.

Advances in the medical management of osteoporosis

Osteoporosis is a skeletal disorder characterised by compromised bone strength predisposing to increased risk of fracture, which is rapidly reaching epidemic proportions as the population ages. Many patients presenting with a fracture caused by a fall from standing height or less are not on any kind of therapy and many patients who sustain these fragility fractures are not started on therapy by their orthopaedic surgeon. In 2004, the United States Surgeon General released a report on osteoporosis recommending that physicians adopt a pyramidal approach to therapy. The base of the pyramid includes calcium, vitamin D, physical therapy and fall prevention. The second level calls for management or elimination of secondary causes of osteoporosis. The third level consists of treatment with either anti-resorptive or anabolic medications. The orthopaedic surgeon is in an ideal position to diagnose fragility fractures and suggest treatment in the hope of preventing future fractures. Anti-resorptive and anabolic therapies currently available are discussed.

Neue Techniken in der Osteoporosediagnostik

In this review article current developments and applications in quantitative osteoporosis imaging are presented. Developments in the field of DXA include geometrical parameters of the proximal femur such as the "hip axis length" and new ROIs to determine BMD. Advances in QCT are new volumetric techniques to quantify BMD at the lumbar spine and the proximal femur. In addition techniques to determine BMD in standard contrast-enhanced abdominal computed tomography studies are described. Currently with the new bone quality concept in full bloom techniques to quantify trabecular bone architecture as new surrogates of bone strength are of increasing significance. Spatial high-resolution techniques such as magnetic resonance imaging and new computed tomography techniques have shown their potential in assessing trabecular bone structure. In addition ultrasound is considered a low-cost technique to explore bone quality.

Effect of lithium carbonate on subchondral bone in sexually mature Wistar rats

Clinical and experimental studies have shown that lithium carbonate causes a number of clinical manifestations such as hyperparathyroidism, hypothyroidism, renal toxicity, and diabetes insipidus. The effect of this drug on the bone biology of experimental animals has not been studied to date. Therefore, the aim of the present experimental work was to study the effect of lithium on bone tissue in healthy sexually mature Wistar rats. Ten female Wistar rats, aged 312-412 months, 210-220 g body weight, were assigned to one of the following groups: untreated control group and experimental group receiving 45 mg/kg body weight/day of lithium carbonate in their drinking water during 3 months. Prior to euthanasia, blood samples were obtained in order to determine plasma phosphorus, calcium alkaline phosphatase, and lithium. After sacrifice, the tibiae were resected, processed, and embedded in paraffin. The following histomorphometric parameters were determined on digital photographs of the histologic sections: BV/TV (%), bone volume; Tb.Th (microm), trabecular thickness; Tb.N (mm(-2)/mm), trabecular number; Tb.Sp (microm), trabecular separation; Ob.S/BS (%), osteoblast surface; ES/BS (%), total erosive surface; Lc.S (%), lining cells surface; and GPC.Th (microm), thickness of growth plate cartilage. The results showed that administration of lithium carbonate cause bone loss in healthy sexually mature Wistar rats. Although the mechanism involved in bone toxicity remains to be clarified, the results obtained in the present study suggest that patients under long-term lithium therapy should be thoroughly evaluated, particularly those presenting other risk factors of osteopenia, such as menopause, low calcium intake, alcohol consumption, and glucocorticoid therapy.