Altered Bone Quality Research Articles

206 Bone quality at the time of lung transplant in cystic fibrosis patients

Background and Hypothesis As CF patients get older, morbidities such as CF-related bone disease (CFBD), superimpose on the pre-existing complications. CFBD predisposes to fractures, especially of the ribs and vertebrae. Knowing that bone mineral density (BMD) is a poor predictor of fractures in CF, we postulate that alterations in bone quality will likely contribute to their propensity to fracture. Methods In order to assess bone quality in CF patients, a 2 cm segment of rib was recovered during lung transplant (LTx). Controls consisted in similarly aged lung donors (D). Dual-energy X-ray absorptiometry (DXA), micro-CT, bone histomorphometry and microcrack detection were used to assess BMD, microarchitecture, bone remodeling and quality of bone respectively. Results Over 17 CF and 21 donor's specimens were analyzed. Patients were stratified according to bisphosphonate (BP) or steroid (GC) treatment at the time of LTx. Ex vivo rib BMD, trabecular BMD and bone volume determined by micro-CT as well as trabecular thickness were significantly reduced in CF, with patients on GC having the lowest values. Despite similar surface occupied by osteoblasts, osteoid parameters (volume, surface and thickness) were lower in CF, regardless of the use of GC or BP. Number of osteoclasts and eroded surfaces were comparable among the groups. Microcracks were 3 to 4 times higher in CF than in D. Of note, the highest microcrack density was found in patients on BP. Conclusion Our data suggest alterations in the bone quality of CF ribs as evidenced by a decrease in osteoblast function and bone formation resulting in the uncoupling of bone remodeling, and the accumulation of microdamages.

Structural and Qualitative Bone Remodeling Around Repetitive Loaded Implants in Rabbits.

Bone mechanical function is regulated by bone quality and bone mineral density (BMD) that reflect bone strength. The preferential alignment of biological apatite (BAp) c-axis/collagen fibers and osteocytes is a determinant factor of bone quality. However, the effect of mechanical loading on bone quality around dental implants is unclear. The aim of this study was to clarify the effects of mechanical loading on osseointegration, bone volume BMD, and bone quality around dental implants. Twenty anodized Ti-6Al-4V alloy implants (KYOCERA Co., Kyoto, Japan) were placed in the proximal tibial metaphysis of 10 rabbits. Twelve weeks after surgery, mechanical loading was applied along the long axis of the implant (50 N, 3 Hz, 1,800 cycles, 2 days/week) for 8 weeks. Osseointegration, bone volume, BMD, and bone quality were evaluated using light microscopy, microcomputed tomography, polarized light microscopy, and microbeam X-ray diffractometer. Mechanical loading increased osseointegration, bone volume, and BMD. Bone quality around dental implant was altered with increased osteocyte numbers and the preferential alignment direction and degree of BAp c-axis/collagen fibers. These findings suggest that mechanical loading effectively induces bone anabolic responses around dental implants. Altered bone quality may upregulate bone strength, contributing to long-term implant stability.

The impact of glucocorticoid therapy on trabecular bone score in older women.

We propose that trabecular bone score could be a useful tool for the study of glucocorticoid-associated bone effects. Trabecular bone score alone and lumbar spine bone mineral density (BMD) used in combination with trabecular bone score, but not lumbar spine BMD alone was able to discriminate between glucocorticoid-treated and glucocorticoid-naïve women. Glucocorticoids result in rapid bone loss and an increase in fracture risk that cannot be fully explained by changes in BMD. Trabecular bone score (TBS) correlates with three-dimensional bone micro-architectural parameters and can be derived from grey-level variations within dual energy X-ray absorptiometry (DXA) scans. We propose that TBS could be a useful tool for the study of glucocorticoid-associated bone effects. We assessed the ability of lumbar spine BMD (LS-BMD), TBS, and LS-BMD with TBS (LS-BMD + TBS) to discriminate between healthy women and (i) glucocorticoid-treated women, and (ii) glucocorticoid-naïve women with recent fractures. Older women (n = 484, ages 55-79 years) who had (i) taken prednisolone ≥5 mg/day for >3 months (n = 64), (ii) sustained a recent fracture of the distal forearm (n = 46), proximal humerus (n = 37), vertebra (n = 30) or proximal femur (n = 28), or (iii) were healthy population-based women (n = 279) were recruited. LS-BMD was measured by DXA and TBS values were derived. Compared to healthy, population-based women, women with recent fractures had lower LS-BMD (-0.34 to -1.38) and TBS (-0.38 to -1.04) Z-scores. Glucocorticoid-treated women had lower TBS Z-scores than glucocorticoid-naïve women (-0.80 versus 0) but their LS-BMD Z-scores did not differ (-0.13 versus 0). TBS alone (area under the receiver operating characteristic curve (AUC) = 0.721) and LS-BMD + TBS (AUC = 0.721), but not LS-BMD alone (AUC = 0.572) was able to discriminate between glucocorticoid-treated and glucocorticoid-naïve women. TBS provides additional information regarding glucocorticoid-associated alterations in bone quality. We conclude that TBS may be a useful tool for the further study of glucocorticoid-induced osteoporosis.

Gene expression changes in cancellous bone of type 2 diabetics: a biomolecular basis for diabetic bone disease

Diabetes mellitus type 2 (2DM) is associated with altered bone quality. In order to analyze associated changes on a molecular level, we investigated the gene expression of key factors of osteoblast metabolism in type 2 diabetics. Total mRNA and protein of bone samples from 2DM patients and non-diabetic patients were isolated, and subsequently, reverse transcription polymerase chain reaction (RT-PCR) or Western blot was performed. Furthermore, pro- and anti-inflammatory serum cytokine levels were determined using a cytokine array. Expression of runt-related transcription factor 2 (RUNX2) was increased by 53%. Expression of the bone sialoproteins, secreted phosphoprotein 1 (SPP1; osteopontin), and integrin-binding sialoprotein (IBSP), was elevated by more than 50%, and activating transcription factor 4 (ATF4) expression was 13% lower in the investigated diabetes group compared to the control group. Similarly, the expression of versican (VCAN) and decorin (DCN) was upregulated twofold in the diabetic group. At the same time, 2DM patients and controls show alterations in pro- and anti-inflammatory cytokine levels in the serum. This study identifies considerable changes in the expression of transcription factors and extracellular matrix (ECM) components of bone in 2DM patients. Furthermore, the analysis of key differentiation factors of osteoblasts revealed significant alterations in gene expression of these factors, which may contribute to the dysregulation of energy metabolism in 2DM.

Research perspectives: The 2013 AAOS/ORS research symposium on Bone Quality and Fracture Prevention

Bone fracture resistance is determined by the amount of bone present ("bone quantity") and by a number of other geometric and material factors grouped under the term "bone quality." In May 2013, a workshop was convened among a group of clinicians and basic science investigators to review the current state of the art in Bone Quality and Fracture Prevention and to make recommendations for future directions for research. The AAOS/ORS/OREF workshop was attended by 64 participants, including two representatives of the National Institutes of Arthritis and Musculoskeletal and Skin Diseases and 13 new investigators whose posters stimulated additional interest. A key outcome of the workshop was a set of recommendations regarding clinically relevant aspects of both bone quality and quantity that clinicians can use to inform decisions about patient care and management. The common theme of these recommendations was the need for more education of clinicians in areas of bone quality and for basic science studies to address specific topics of pathophysiology, diagnosis, prevention, and treatment of altered bone quality. In this report, the organizers with the assistance of the speakers and other attendees highlight the major findings of the meeting that justify the recommendations and needs for this field.

Prostate cancer metastases alter bone mineral and matrix composition independent of effects on bone architecture in mice — A quantitative study using microCT and Raman spectroscopy

Prostate cancer is the most common primary tumor and the second leading cause of cancer-related deaths in men in the United States. Prostate cancer bone metastases are characterized by abnormal bone remodeling processes and result in a variety of skeletal morbidities. Prevention of skeletal complications is a crucial element in prostate cancer management. This study investigated prostate cancer-induced alterations in the molecular composition and morphological structure of metastasis-bearing bones in a mouse model of prostate cancer using Raman spectroscopy and micro-computed tomography (microCT). LNCaP C4-2B prostate cancer cells were injected into the right tibiae of 5-week old male SCID mice. Upon sacrifice at 8weeks post tumor inoculation, two out of the ten tumor-bearing tibiae showed only osteoblastic lesions in the radiographs, 4 osteolytic lesions only and 4 mixed with osteoblastic and osteolytic lesions. Carbonate substitution was significantly increased while there was a marked reduction in the level of collagen mineralization, mineral crystallinity, and carbonate:matrix ratio in the cortex of the intact tumor-bearing tibiae compared to contralateral controls. MicroCT analysis revealed a significant reduction in bone volume/total volume, trabecular number and trabecular thickness, as well as significant increase in bone surface/volume ratio in tibiae with osteolytic lesions, suggesting active bone remodeling and bone loss. None of the changes in bone compositional properties were correlated with lesion area from radiographs or the changes in bone architecture from microCT. This study indicates that LNCaP C4-2B prostate cancer metastases alter bone tissue composition independent of changes in architecture, and altered bone quality may be an important contributor to fracture risk in these patients. Raman spectroscopy may provide a new avenue of investigation into interactions between tumor and bone microenvironment.

Alterations in Bone Quality After Socket Preservation with Grafting Materials: A Systematic Review

While the ability of various grafting materials to preserve extraction socket morphology has been adequately reviewed, the quality of the grafted bone in the socket is not as well understood. This systematic review aimed to compare the proportion of vital bone and connective tissue between grafted and naturally healed sockets. An electronic search of five databases (from 1965 to November 2011) and a hand search of peer-reviewed journals for relevant articles were performed. Human clinical trials that compared histologic components of soft and hard tissues in augmented sockets and naturally healed sites, with at least five samples per group, were included. Eight studies (five randomized controlled trials and three controlled clinical trials) were included. The mean percentages of vital bone and connective tissue in natural healing sockets were 38.5% ± 13.4% and 58.3% ± 10.6%, respectively. Limited evidence (one to two articles for each material) implied that vital bone fraction was not different with demineralized allografts and autografts and increased by 6.2% to 23.5% with alloplasts in comparison to nongrafted sites. Four studies investigating the effect of xenografts were available, with equivocal results. The difference in the mean percentage of vital bone ranged from -22.2% (decrease) to 9.8% (increase). Connective tissue content decreased with the use of the aforementioned bone substitutes. Considerable residual hydroxyapatite and xenograft particles (15% to 36%) remained at a mean of 5.6 months after socket augmentation procedures. Based on a limited number of prospective comparative studies, the use of grafting materials for socket augmentation might change the proportion of vital bone in comparison to sockets allowed to heal without grafting. Whether these changes in bone quality will influence implant success and peri-implant tissue stability remains unknown.

전이성 골암으로 인한 골질 변화와 이로 인한 골절 위험성 분석

While much has been learned about the mechanisms of metastatic spread of cancer to bone, there has been little headway in establishing guidelines for monitoring the alteration in bone quality and estimating fracture risk. The aims of this study are, therefore, 1) to evaluate bone quality induced by metastatic bone tumor by analyzing the characteristics on bone microarchitecture and degree of bone mineralization and 2) analyze fracture risk increased secondary to the bone quality changes by metastatic bone tumor through calculating mechanical rigidities based on in-vivo micro CT images. For this study, eighteen female SD rats (12 weeks old, approximate 250 g) were randomly allocated in Sham and Tumor groups. W256 (Walker carcinosarcoma 256 malignant breast cancer cell) was inoculated in the right femur (intraosseous injection) in Tumor group, while 0.9% NaCl (saline solution) was injected in Sham group. The right hind limbs of all rats were scanned by in-vivo micro-CT to acquire structural parameters and degree of bone mineralization at 0 week, 4 weeks, 8 weeks, and 12 weeks after surgery. At the same time, urine was collected by metabolic cages for a biochemical marker test in order to evaluate bone resorption. Then, bone metastasis had been directly identified by positron emission tomography. Finally, axial, bending and torsional rigidities had been calculated based on in-vivo micro CT images for predict fracture risk. The results of this study showed that metastatic bone tumor might induce significant decrease in bone quality and increase of fracture risk. This study may be helpful to monitoring a degree of bone metastasis and predicting fracture risk due to metastatic bone tumor. In addition, this noninvasive diagnostic methodology may be utilized for evaluating other bone metabolic diseases such as osteoporosis.

Alterations of bone geometry, density, microarchitecture, and biomechanical properties in systemic lupus erythematosus on long-term glucocorticoid: a case–control study using HR-pQCT

Compared to controls, HR-pQCT at distal radius of SLE patients on chronic glucocorticoid (SLE/GC) revealed reduced bone area, vBMD, deteriorated microarchitecture, and unevenly distributed stresses limited to cortical bone. Despite similar trabecular quality, whole bone strength decreased in patients. These alterations may partly explain high fracture rates in SLE/GC. To assess bone geometric, densitometric, microarchitectural, and biomechanical properties in patients with systemic lupus erythematosus (SLE) on long-term glucocorticoid (GC) (SLE/GC) as compared with healthy controls. A total of 180 female SLE patients and 180 healthy controls were in this cross-sectional study to assess areal bone mineral density (aBMD) by dual-energy X-ray absorptiometry. High-resolution peripheral quantitative computed tomography (HR-pQCT) and microfinite element analysis (μFEA) was performed at distal radius. In addition to significantly lower aBMD at femoral neck, total hip and lumbar spine, cortical area, average volumetric BMD (vBMD) and cortical vBMD also significantly reduced by 5.3, 5.7, to 1.9% in SLE patients, respectively. Deteriorations of cortical microarchitecture were pronounced in patients, with 6.3% reduction in cortical thickness and 13.6% higher in cortical porosity. Local stresses were more unevenly distributed through cortical bone in patients. SLE/GC patients had decreased whole bone stiffness, estimated failure load, and apparent modulus. Parameters related to trabecular bone density and microarchitecture were comparable between patients and controls. In SLE/GC patients, despite a reduction in bone area, vBMD and deteriorated microarchitecture and unevenly distributed stresses limited to the cortical compartment, whole bone strength decreased. HR-pQCT and μFEA were promising in elucidating the potential underlying pathophysiology of bone loss and propensity to fracture in SLE/GC and provide us additional information about alterations of bone quality which might better predict fracture risk beyond aBMD in SLE/GC.

Atypical dental implant failure with long-term bisphosphonate treatment—akin to atypical fractures?

Concern that long-term bisphosphonate therapy may significantly undermine bone quality in osteoporotic patients has been heightened by rare instances of low-impact atypical femoral fractures that are often bilateral. Reduced fracture toughness is believed to result from reduced bone remodeling, leading to increased homogeneity in bone microarchitecture, narrowed bone mineral density distribution, and increased bone tissue microdamage burden. We postulate that these long-term alterations in bone quality may undermine the ongoing remodeling surrounding osteointegrated endosseous dental implants as well. To illustrate our hypothesis, we report the catastrophic failure of multiple, successfully osteointegrated dental implants in an osteopenic patient following long-term bisphosphonate treatment. This clinical presentation may reflect underlying adverse changes in bone quality, in a manner analogous to atypical fractures in a small percentage of patients on bisphosphonates. This report highlights the need for multidisciplinary care of patients who have dental implants and begin or are receiving long-term bisphosphonate therapy.

End-stage Posttraumatic Osteoarthritis Treated With THA in Osteogenesis Imperfecta

Osteogenesis imperfecta is an incurable genetic disorder manifested with altered bone quality that predisposes patients to a multitude of fractures throughout their lives, including acetabular fractures. The management of acetabular fractures in patients with osteogenesis imperfecta remains a challenging clinical problem, with a paucity of literature supporting treatments and their outcomes. Limited reports in the literature validate the use of total hip arthroplasty (THA) in patients with osteogenesis imperfecta, and they describe the adult population only.This article describes a case of delayed diagnosis of a transverse acetabular fracture and femoral head impaction fracture that led to posttraumatic end-stage hip osteoarthritis in a 16-year-old boy with osteogenesis imperfecta (Sillence Type I) that was sustained after minimal trauma. Clinical examination 3 months postinjury revealed a significant pelvic obliquity, severe pain with hip range of motion, and limited hip range of motion. Imaging studies revealed a complete loss of articular cartilage and significant joint effusion.The patient underwent THA. No postoperative complications occurred. Two-year follow-up showed an excellent clinical result. The patient's hip was pain free, and he was able to walk with no limp.The authors are unaware of any reported cases of children with osteogenesis imperfecta undergoing THA. Based on the reported literature and the authors' experience, THA can be a reliable surgical option for patients with osteogenesis imperfecta.

Significant deterioration in nanomechanical quality occurs through incomplete extrafibrillar mineralization in rachitic bone: Evidence from in-situ synchrotron X-ray scattering and backscattered electron imaging

Bone diseases such as rickets and osteoporosis cause significant reduction in bone quantity and quality, which leads to mechanical abnormalities. However, the precise ultrastructural mechanism by which altered bone quality affects mechanical properties is not clearly understood. Here we demonstrate the functional link between altered bone quality (reduced mineralization) and abnormal fibrillar-level mechanics using a novel, real-time synchrotron X-ray nanomechanical imaging method to study a mouse model with rickets due to reduced extrafibrillar mineralization. A previously unreported N-ethyl-N-nitrosourea (ENU) mouse model for hypophosphatemic rickets (Hpr), as a result of missense Trp314Arg mutation of the phosphate regulating gene with homologies to endopeptidase on the X chromosome (Phex) and with features consistent with X-linked hypophosphatemic rickets (XLHR) in man, was investigated using in situ synchrotron small angle X-ray scattering to measure real-time changes in axial periodicity of the nanoscale mineralized fibrils in bone during tensile loading. These determine nanomechanical parameters including fibril elastic modulus and maximum fibril strain. Mineral content was estimated using backscattered electron imaging. A significant reduction of effective fibril modulus and enhancement of maximum fibril strain was found in Hpr mice. Effective fibril modulus and maximum fibril strain in the elastic region increased consistently with age in Hpr and wild-type mice. However, the mean mineral content was ∼21% lower in Hpr mice and was more heterogeneous in its distribution. Our results are consistent with a nanostructural mechanism in which incompletely mineralized fibrils show greater extensibility and lower stiffness, leading to macroscopic outcomes such as greater bone flexibility. Our study demonstrates the value of in situ X-ray nanomechanical imaging in linking the alterations in bone nanostructure to nanoscale mechanical deterioration in a metabolic bone disease.

50 Years Ago in CORR: Osteomalacia, Osteoporosis, and Calcium Deficiency B.E.C. Nordin, MD, MRCP, PhD 1960;17:235-258

The concept of bone quality has been long known, although perhaps not in the current context. Some of the earliest references to “bone quality” appear to be in the context of animal husbandry. Burdett-Coutts, referring to the purchase of horses, commented at the end of the 19th Century, “And so he sets himself to think how he can supply the dealers who have been round during the past week, wanting something on short legs, with bone quality, and substance…” [4]. The notion that it might apply to disease appears in the mid 20th Century: Bell remarked, “Rickets is the only condition in which alterations of bone quality have been demonstrated in this laboratory…” [2]. The increase in rates of fracture in elderly persons was well established in the late 1800s [7]. However, researchers questioned whether or not this related to bone quality per se. Knowelden and his colleagues, commented in 1964, “There is indeed no mystery about the immediate cause of any fracture – it is, of course, that the stress produced by the forces applied to the bone has exceeded the breaking stress. There is no proof from either animal or human experiments that bone quality, that is breaking stress, decreases in old age. The bone is, of course, decreased in amount - the compact shaft walls and trabeculae becoming thinner and therefore weaker.” Thus, they presumed the quality of bone—if quality is defined as breaking strength—as a material (contrasted to bone as a structure) was similar regardless of age. However, bone quality may be defined in many ways. Elsewhere in this issue, we devote a symposium to bone quality. One of the striking points is the more or less subtle differences in definitions of “bone quality.” Boskey et al. [3] comment, “The term ‘bone quality’ is frequently used by clinicians, basic scientists, and engineers. However, do they mean the same thing?…there are many aspects of bone quality that vary in importance and scope with the person providing the definition” while Paschalis et al. [6] suggest, “Bone quality encompasses the structural and material properties of bone.” Nordin [5] explored another aspect of bone quality: calcium content, particularly its relationship to bone strength. He, as others, found a wide range of dietary “calcium requirements” for individuals to maintain a balance of intake and excretion (Fig. 10). Not only did subjects have a wide range of absorption, they also had a wide range of excretion, only partly related to dietary intake (Fig. 12). Dietary calcium content was earlier related to maximum strength of the bone in rats [1]. In reviewing other evidence, Nordin concluded, “Experimental work, the significance of which has not been sufficiently appreciated, shows that calcium deficiency causes osteoporosis in animals, whereas protein deficiency does not…It cannot be claimed that all forms of osteoporosis can be explained on the lines presented here, but it is believe that so-called postmenopausal and ‘senile’ osteoporosis could be accounted for in this way…” These continue to be commonly held views and undoubtedly account for the dizzying array of calcium supplements marketed throughout the world. Fig. 10 Calcium requirement of 32 normal subjects calculated from the calcium balances at more than one level of intake. (Reprinted with permission and © Lippincott Williams & Wilkins, from Nordin BEC. Osteomalacia, Osteoporosis, and Calcium Deficiency. ... Fig. 12 Mean urinary calcium and lower and upper limits in normal subjects at different levels of intake. Note small change in mean excretion with changing intake. (Reprinted with permission and © Lippincott Williams & Wilkins, from Nordin BEC. ...

Bone Quality: From Bench to Bedside: Editorial Comment: The Clinical Challenge of Altered Bone Quality

Bone Quality: From Bench to Bedside: Editorial Comment: The Clinical Challenge of Altered Bone Quality

Short-term and long-term orthopaedic issues in patients with fragility fractures.

Patients with impaired bone quality who suffer a fragility fracture face substantial challenges in both their short- and long-term care. In addition to poor bone quality, many of these patients have multiple medical comorbidities that alter their surgical risk and affect their ultimate functional recovery. Some medical issues can contribute to the altered bone quality and must be addressed to prevent future fractures. This review summarizes the modifications in perioperative management and fracture fixation in patients with common fragility fractures who have impaired bone quality. It also summarizes the postoperative diagnosis and treatment of secondary causes of impaired bone quality in these patients. We performed a PubMed search, and literature published after 2000 was prioritized, with the exception of benchmark clinical trial studies published before 2000. Patients with altered bone quality require rapid perioperative management of multiple medical comorbidities. Implant selection in patients with poor quality bone should permit early weightbearing, and constructs should maximize surface area contact with the remaining bone. Long-term diagnosis and treatment of other disease states contributing to poor bone quality (vitamin D deficiency/insufficiency, hypothyroidism, hyperthyroidism, hyperparathyroidism, Cushing's disease, and hypogonadism) must occur to minimize the chances of future fractures. Recognition of patients with impaired bone quality and proper treatment of their special needs in both the short and long term are essential for their best opportunity for maximal functional recovery and prevention of future fractures.

Variations in morphological and biomechanical indices at the distal radius in subjects with identical BMD

Determination of osteoporotic status is based primarily on areal bone mineral density (aBMD) obtained through dual X-ray absorptiometry (DXA). However, many fractures occur in patients with T-scores above the WHO threshold of osteoporosis, in part because DXA measures are insensitive to biomechanically important alterations in bone quality. The goal of this study was to determine – within groups of subjects with identical radius aBMD values – the extant variation in densitometric, geometric, microstructural, and biomechanical parameters. High resolution peripheral quantitative computed tomography (HR-pQCT) and DXA radius data from males and females spanning large ranges in age, osteoporotic status, and anthropometrics were compiled. 262 distal radius datasets were processed for this study. HR-pQCT scans were analyzed according to the manufacturer’s standard clinical protocol to quantify densitometric, geometric, and microstructural indices. Micro-finite element analysis was performed to calculate biomechanical indices. Factor of risk of wrist fracture was calculated. Simulated aBMD calculated from HR-pQCT data was used to group scans for evaluation of variation in quantified indices. Indices reflecting the greatest variation within aBMD level were BMD in the central portion of the trabecular compartment (max CV 142), trabecular heterogeneity (max CV 90), and intra-cortical porosity (max CV 151). Of the biomechanical indices, cortical load fraction had the greatest variation (max CV 38). Substantial variations in indices reflecting density, structure, and biomechanical competence exist among subjects with identical aBMD levels. Overlap of these indices among osteoporotic status groups reflects the reported incidence of osteoporotic fracture in subjects classified as osteopenic or normal.

Essential Role of Nuclear Factor of Activated T Cells (NFAT)-mediated Wnt Signaling in Osteoblast Differentiation Induced by Strontium Ranelate

The antiosteoporotic treatment strontium ranelate (SrRan) was shown to increase bone mass and strength by dissociating bone resorption and bone formation. To identify the molecular mechanisms of action of SrRan on osteoblasts, we investigated its effects on calcineurin-NFAT (nuclear factor of activated T cells) signaling, an important calcium sensitive pathway controlling bone formation. Using murine MC3T3-E1 and primary murine osteoblasts, we demonstrate that SrRan induces NFATc1 nuclear translocation, as shown by immunocytochemical and Western blot analyses. Molecular analysis showed that SrRan increased NFATc1 transactivation in osteoblasts, an effect that was fully abrogated by the calcineurin inhibitors cyclosporin A or FK506, confirming that SrRan activates NFATc1 signaling in osteoblasts. This has functional implications because calcineurin inhibitors blunted the enhanced osteoblast replication and expression of the osteoblast phenotypic markers Runx2, alkaline phosphatase, and type I collagen induced by SrRan. We further found that SrRan increased the expression of Wnt3a and Wnt5a as well as beta-catenin transcriptional activity in osteoblasts, and these effects were abolished by calcineurin inhibitors. The Wnt inhibitors sFRP1 and DKK1 abolished SrRan-induced osteoblast gene expression. Furthermore, blunting the Wnt5a receptor Ryk or RhoA that acts downstream of Ryk abrogated cell proliferation and osteoblast gene expression induced by SrRan. These results indicate that activation of NFATc1 and downstream canonical and non-canonical Wnt signaling pathways mediate SrRan-induced osteoblastic cell replication and differentiation, which provides novel insights into the mechanisms of action of this antiosteoporotic agent in osteoblastogenesis.

Implications of hormonal and neuroendocrine changes associated with seizures and antiepileptic drugs: A clinical perspective

Epilepsy and antiepileptic drugs (AEDs) affect hormones and neuroendocrine systems, which may result in a change in the seizure threshold (catamenial epilepsy) or in comorbidities including sexual dysfunction, reproductive dysfunction, and abnormalities in bone health. Catamenial epilepsy occurs commonly in women with epilepsy. The most commonly reported and studied mechanism proposed to explain why some women have a catamenial seizure exacerbation relates to cyclic changes in reproductive steroid hormones. Women and men with epilepsy have a higher than expected prevalence of sexual dysfunction. The epilepsy syndrome and localization influence the presentation of sexual dysfunction. Reproductive dysfunction occurs in both men and women with epilepsy. As with sexual dysfunction both the epilepsy syndrome and specific AEDs influence the presentation of reproductive dysfunction. Persons with epilepsy have an increased risk of fracture secondary to decreased bone mineral density (BMD), altered bone quality, and a propensity to fall because of either seizures or side effects of medication. Some AEDs are associated with abnormalities in BMD and bone and mineral metabolism.

Impaired Body Weight and Tail Length Gain and Altered Bone Quality after Treatment with the Aromatase Inhibitor Exemestane in Male Rats

Background: Estrogen deficiency induced by aromatase inhibitors may be a novel treatment modality for growth enhancement in short children, but may have adverse effects on bone, brain and reproduction. Aim: To assess growth effects and potential adverse effects of aromatase inhibition in male rats. Methods: 26-day-old prepubertal rats received intramuscular injections with placebo or the aromatase inhibitor exemestane at a dose of 10, 30 or 100 mg/kg/week [E10, E30, E100(6)] for 6 weeks, completely covering the sexual maturation phase, or with 3 weeks E100 followed by 3 weeks placebo [E100(3)]. Growth parameters and histology of the testis, seminal vesicle and brain were analyzed. Bone architecture was studied with X-ray microtomography. Results: Exemestane dose-dependently decreased body weight and tail length gain, as well as liver and seminal vesicle weights, but did not affect nose-anus length gain, growth plate width or radial growth. E100(6) decreased trabecular thickness (epiphysis and metaphysis) and number (metaphysis). Normal IGF-I levels and brain, testis and seminal vesicle morphology were observed. E100(3) resulted in decreased tail length gain only. Conclusion: Exemestane treatment during sexual maturation did not augment linear growth in male rats, but caused impaired body weight and tail length gain and osteopenia.

Marginal Growth Increase, Altered Bone Quality and Polycystic Ovaries in Female Prepubertal Rats after Treatment with the Aromatase Inhibitor Exemestane

Background: Aromatase inhibition has been proposed as a potential approach for growth enhancement in children with short stature, but detailed animal studies are lacking. Aim: To assess the effect and potential adverse effects of aromatase inhibition on growth in female rats. Methods: Prepubertal Wistar rats received intramuscular injections with placebo or the aromatase inhibitor exemestane at a dose of 10, 30 or 100 mg/kg/week (E10, E30, E100) for 3 weeks. A control group was ovariectomized (OVX). Weight and length gain, tibia and femur length, growth plate width, organ weights, insulin-like growth factor I (IGF-I) levels, and histology of the ovaries, uterus and brain were analyzed. X-ray microtomography of femora was performed. Results: E100 significantly increased weight gain and growth plate width, but less prominently than OVX. Trabecular number and thickness were decreased in E100 and OVX in the metaphysis and epiphysis. E100 significantly decreased ovarian weight and multiple cysts were seen upon histological evaluation. No significant effects were found on IGF-I levels and brain morphology in E100. E10 and E30 had no effects on growth. Conclusion: A high dose of exemestane marginally increases axial and appendicular growth in female rats, at the expense of osteopenia and polycystic ovaries.