Trabecular reorganization in consecutive iliac crest biopsies when switching from bisphosphonate to strontium ranelate treatment

Role of Calcitonin and Strontium Ranelate in Osteoporosis

Background

Both Strontium Ranelate (SR) and Calcitonin (CT) can be used to treat osteoporosis. Calcitonin was actually one of the very initial medicines used to treat osteoporosis, especially in postmenopausal cases. However, the fracture prevention effect of Calcitonin is only proven to be in vertebrae and that too with nasal route only. When comparing Calcitonin with other conventional medications in treating osteoporosis, Calcitonin has got no additional advantages. Strontium Ranelate has got double effect, i.e., less bone resorption and more bone formation. Therefore, it can lead to an increase in bone mass significantly. Strontium Ranelate has been proven to decrease the risk of non-vertebral fractures as well as vertebral fractures.

Conclusion

Both Calcitonin and Strontium Ranelate are used only as a second-line therapy for the treatment of osteoporosis and not as first-line therapy, mainly because of their safety concern and also because they do not provide any advantages compared to other therapy for the treatment of osteoporosis.

Biosafety of a novel covered self-expandable metal stent coated with poly(2-methoxyethyl acrylate) in vivo

Covered self-expandable metal stents (CSEMS) are often used for palliative endoscopic biliary drainage; however, the unobstructed period is limited because of sludge occlusion. The present study aimed to evaluate the biosafety of a novel poly(2-methoxyethyl acrylate)-coated CSEMS (PMEA-CSEMS) for sludge resistance and examine its biosafety in vivo. Using endoscopic retrograde cholangiopancreatography, we placed the PMEA-CSEMS into six normal porcine bile ducts and conventional CSEMS into three normal porcine bile ducts. We performed serological examination and undecalcified histological analysis at 1, 3, and 6 months during follow-up. In the bile ducts with PMEA-CSEMS or conventional CSEMS, we observed no increase in liver enzyme or inflammatory marker levels in the serological investigations and mild fibrosis but no inflammatory response in the histopathological analyses. Thus, we demonstrated the biosafety of PMEA-CSEMS in vivo.

Guidelines for the assessment of bone density and microarchitecture in vivo using high-resolution peripheral quantitative computed tomography

INTRODUCTION

The application of high-resolution peripheral quantitative computed tomography (HR-pQCT) to assess bone microarchitecture has grown rapidly since its introduction in 2005. As the use of HR-pQCT for clinical research continues to grow, there is an urgent need to form a consensus on imaging and analysis methodologies so that studies can be appropriately compared. In addition, with the recent introduction of the second-generation HrpQCT, which differs from the first-generation HR-pQCT in scan region, resolution, and morphological measurement techniques, there is a need for guidelines on appropriate reporting of results and considerations as the field adopts newer systems.

METHODS

A joint working group between the International Osteoporosis Foundation, American Society of Bone and Mineral Research, and European Calcified Tissue Society convened in person and by teleconference over several years to produce the guidelines and recommendations presented in this document.

RESULTS

An overview and discussion is provided for (1) standardized protocol for imaging distal radius and tibia sites using HR-pQCT, with the importance of quality control and operator training discussed; (2) standardized terminology and recommendations on reporting results; (3) factors influencing accuracy and precision error, with considerations for longitudinal and multi-center study designs; and finally (4) comparison between scanner generations and other high-resolution CT systems.

CONCLUSION

This article addresses the need for standardization of HR-pQCT imaging techniques and terminology, provides guidance on interpretation and reporting of results, and discusses unresolved issues in the field.

Increased mechanical loading through controlled swimming exercise induces bone formation and mineralization in adult zebrafish

Exercise promotes gain in bone mass through adaptive responses of the vertebrate skeleton. This mechanism counteracts age- and disease-related skeletal degradation, but remains to be fully understood. In life sciences, zebrafish emerged as a vertebrate model that can provide new insights into the complex mechanisms governing bone quality. To test the hypothesis that musculoskeletal exercise induces bone adaptation in adult zebrafish and to characterize bone reorganization, animals were subjected to increased physical exercise for four weeks in a swim tunnel experiment. Cellular, structural and compositional changes of loaded vertebrae were quantified using integrated high-resolution analyses. Exercise triggered rapid bone adaptation with substantial increases in bone-forming osteoblasts, bone volume and mineralization. Clearly, modeling processes in zebrafish bone resemble processes in human bone. This study highlights how exercise experiments in adult zebrafish foster in-depth insight into aging-related bone diseases and can thus catalyze the search for appropriate prevention and new treatment options.

Trends in trabecular architecture and bone mineral density distribution in 152 individuals aged 30-90 years

The strength of trabecular bone depends on its microarchitecture and its tissue level properties. However, the interrelation between these two determinants of bone quality and their relation to age remain to be clarified. Iliac crest bone cores (n=152) from individuals aged 30-90 years were analyzed by quantitative backscattered electron imaging. Univariate and multivariate analyses were conducted to determine whether epidemiological parameters (age, sex or BMI), structural histomorphometrical variables (BV/TV, Tb.Th, Tb.N and Tb.Sp) and osteoid-related indices (OV/BV, OS/BS or O.Th) predict the degree of bone mineralization. While sex and BMI were not associated with bone mineralization, age was positively correlated with the most frequently occurring calcium concentrations (Ca peak), the percentage of highly mineralized bone areas (Ca high) and, in the case of adjusted covariates, also the mean calcium content (Ca mean). Bone volume fraction and trabecular thickness were both negatively correlated with Ca mean. However, trabecular thickness was additionally associated with Ca peak, Ca high as well as the amount of low mineralized bone (Ca low) and was the only structural parameter predicting bone mineralization independent of age. Furthermore, our analyses demonstrated that osteoid variables - within a normal range (<2% OV/BV) - were significantly associated with all mineralization parameters and represent the only predictor for the mineralization heterogeneity (Ca width). Taken together, we showed that elevated trabecular bone mineralization correlates with aging and bone loss. However, these associations are attributable to trabecular thinning that comes along with high bone mineralization due to the loss of low mineralized bone surfaces. Therefore, we demonstrated that the degree of areally resolved bone mineral is primarily associated with the amount of physiological osteoid present and the thickness of mineralized bone in trabeculae.

A holistic hip fracture approach: individualized diagnosis and treatment after surgery

Secondary fracture prevention is of paramount importance in the clinical management of patients with hip fractures. However, in contrast to the excellent surgical care provided to these patients in the Western hemisphere and despite good medical options, causative treatment of the underlying osteopathy causing skeletal fragility remains an unmet medical need that urgently needs to be improved. This calls for a concerted action between orthopedic/trauma surgeons and osteologists, as outstanding hospitals not only treat fragility fractures, but also prevent fractures from recurring. Aiming for a holistic hip fracture approach, in this work we highlight aspects of (a) improved risk assessment and differential diagnosis, (b) optimized basic medical care, and

Bisphosphonate-osteoclasts: changes in osteoclast morphology and function induced by antiresorptive nitrogen-containing bisphosphonate treatment in osteoporosis patients

Osteoclasts are unique cells capable of bone resorption and therefore have become a major target in osteoporosis treatment strategies. Bisphosphonates suppress bone turnover via interference with the internal enzymatic cell system of osteoclasts leading to cytoskeletal disruption. This mechanism found its clinical relevance in reducing bone resorption, stabilizing bone mass and reducing fracture risk in osteoporosis patients. However, knowledge about specific in vivo changes in osteoclast cell morphology and function is still insufficient. We examined osteoclasts in 23 paired bone biopsies from osteoporosis patients (18 males, 5 females; age: 52.6±11.5yrs) under nitrogen-containing bisphosphonate administration with a mean treatment duration of three years. Formalin-fixed, undecalcified sections were assessed by qualitative and quantitative bone histomorphometry, where the osteoclast morphology, nuclei, distribution, location as well as resorption parameters were investigated to obtain information about cell function and viability. After three years of treatment, resorption parameters decreased significantly while the number of osteoclasts remained unchanged. Out of 23 patients, nine developed previously termed "giant-osteoclasts" with increased size, numerous nuclei (>10 nuclei/Oc) and oftentimes detachment from the bone surface. These cells frequently had pycnotic nuclei and other morphological signs suggestive of osteoclast apoptosis. Characteristic large-sized osteoclasts were uniquely found in patients treated with nitrogen-containing bisphosphonates, thus being clearly distinguishable from giant-osteoclasts in other bone disorders such as Paget disease, secondary hyperparathyroidism or osteopetrosis. The resorption indices of large-sized osteoclasts, specifically the eroded perimeter and erosion depth, revealed significantly reduced values but not an entirely inhibited resorption capability. Bisphosphonate-osteoclasts' viability and affinity to bone seem significantly disturbed while the apoptotic process may be prolonged for a yet unknown period of time in favor of maintaining a low bone turnover.

A physiologically based pharmacokinetic model for strontium exposure in rat

PURPOSE

To develop a physiologically based pharmacokinetic (PBPK) model to describe the disposition of Strontium--a bone seeking agent approved in 2004 (as its Ranelate salt) for treatment of osteoporosis in post-menopausal women.

METHODS

The model was developed using plasma and bone exposure data obtained from ovariectomised (OVX) female rats--a preclinical model for post-menopausal osteoporosis. The final PBPK model incorporated elements from literature models for bone seeking agents allowing for description of the heterogeneity of bone tissue and also for a physiological description of bone remodelling processes. The model was implemented in MATLAB in open and closed loop configurations, and fittings of the model to exposure data to estimate certain model parameters were carried out using nonlinear regression, treating data with a naïve-pooled approach.

RESULTS

The PBPK model successfully described plasma and bone exposure of Strontium in OVX rats with parameter estimates and model behaviour in keeping with known aspects of the distribution and incorporation of Strontium into bone.

CONCLUSIONS

The model describes Strontium exposure in a physiologically rationalized manner and has the potential for future uses in modelling the PK-PD of Strontium, and/or other bone seeking agents, and for scaling to model human Strontium bone exposure.

Analysis of retrieved hip resurfacing arthroplasties reveals the interrelationship between interface hyperosteoidosis and demineralization of viable bone trabeculae

Retrieved hip resurfacing arthroplasties (HRA) revised for causes other than osteonecrosis enable further insights into bone-cement interactions within the interface with only minimal biomechanical stresses. Our primary objective was to investigate the mineralization changes at the trabecular bone interface in retrieved hips using bright field and polarized light microscopy and by quantitative backscattered electron imaging. Because superficial seams of non-mineralized bone tissue varied substantially, we defined hyperosteoidosis as an osteoid seam of more than 20 µm thickness. We hypothesized that interface hyperosteoidosis might be caused by the demineralization of previously mineralized bone tissue. One hundred and thirty-one retrieved HRAs with viable bone remnant tissue were analyzed. Bone mineral density distribution obtained from backscattered signal intensities of the trabecular bone at the bone-cement interface was assessed in cases with and without interface hyperosteoidosis. In cases with interface hyperosteoidosis, the degree of trabecular mineralization was also analyzed in deeper areas of the femoral remnants. Thirty-four cases showed hyperosteoidosis at the bone-cement interface, mostly in female patients. Bone trabeculae with hyperosteoidosis displayed a mineral density distribution pattern suggestive of the demineralization of a previously mineralized bone matrix. Our results demonstrate the localized disorder of the mineralization pattern of bone trabeculae at the bone-cement interface in a group of retrieved HRAs. In previously well-fixed femoral components, potential adverse effects on the load-bearing bone due to a decreased degree of mineralization at the bone-cement interface may affect the durability of the implant's function.