Visualization of bisphosphonate-induced caspase-3 activity in apoptotic osteoclasts in vitro

Inhibition of caspase-8 cascade restrains the osteoclastogenic fate of bone marrow cells

Osteoclasts are multinucleated cells of hematopoietic origin, with a pivotal role in bone development and remodeling. Failure in osteoclast differentiation and activation leads to various bone disorders; thus, attention has focused on a search of molecules involved in osteoclast regulatory pathways. Caspase-8 appears to be an interesting candidate for further exploration, due to its potential function in bone development and homeostasis. Mouse bone marrow cells were differentiated into osteoclasts by RANKL stimulation. Increased activation of caspase-8 and its downstream executioner caspases (caspase-3 and caspase-6) was found during osteoclastogenesis. Subsequent inhibition of caspase-8, caspase-3, or caspase-6, respectively, during osteoclast differentiation showed distinct changes in the formation of TRAP-positive multinucleated cells and reduced expression of osteoclast markers including Acp5, Ctsk, Dcstamp, and Mmp9. Analysis of bone matrix resorption confirmed significantly reduced osteoclast function after caspase inhibition. The results clearly showed the role of caspases in the proper development of osteoclasts and contributed new knowledge about non-apoptotic function of caspases.

The novel cytotoxic polybisphosphonate osteodex decreases bone resorption by enhancing cell death of mature osteoclasts without affecting osteoclastogenesis of RANKL-stimulated mouse bone marrow macrophages

It has previously been demonstrated that the polybisphosphonate osteodex (ODX) inhibits bone resorption in organ-cultured mouse calvarial bone. In this study, we further investigate the effects by ODX on osteoclast differentiation, formation, and function in several different bone organ and cell cultures. Zoledronic acid (ZOL) was used for comparison. In retinoid-stimulated mouse calvarial organ cultures, ODX and ZOL significantly reduced the numbers of periosteal osteoclasts without affecting Tnfsf11 or Tnfrsf11b mRNA expression. ODX and ZOL also drastically reduced the numbers of osteoclasts in cell cultures isolated from the calvarial bone and in vitamin D3-stimulated mouse crude bone marrow cell cultures. These data suggest that ODX can inhibit osteoclast formation by inhibiting the differentiation of osteoclast progenitor cells or by directly targeting mature osteoclasts. We therefore assessed if osteoclast formation in purified bone marrow macrophage cultures stimulated by RANKL was inhibited by ODX and ZOL and found that the initial formation of mature osteoclasts was not affected, but that the bisphosphonates enhanced cell death of mature osteoclasts. In agreement with these findings, ODX and ZOL did not affect the mRNA expression of the osteoclastic genes Acp5 and Ctsk and the osteoclastogenic transcription factor Nfatc1. When bone marrow macrophages were incubated on bone slices, ODX and ZOL inhibited RANKL-stimulated bone resorption. In conclusion, ODX does not inhibit osteoclast formation but inhibits osteoclastic bone resorption by decreasing osteoclast numbers through enhanced cell death of mature osteoclasts.

Editorial Commentary: Postoperative Zoledronic Acid Improves Tendon Healing but Does Not Affect Outcomes in Rotator Cuff Repair Patients With Postmenopausal Osteoporosis

Understanding the preoperative risk factors for successful rotator cuff repair (RCR) and ways to optimize these factors is an evolving area of study. The Rotator Cuff Healing Index and other proxy risk factors for failed rotator cuff healing have implicated significant fatty infiltration, muscular atrophy, advanced chronological age, tear size and retraction, and ultimately, osteoporosis. Although structural (or biological) augmentation and tendon transfer have been proposed as solutions for the alarmingly high rate of failure after primary RCR, other options may preferentially focus on the enthesis and underlying osseous footprint. Currently, bisphosphonates are frequently used in the treatment of osteoporosis and prevention of fragility fractures. However, burgeoning evidence suggests that postoperative zoledronic acid may have clinical utility after rotator cuff and other tendon repairs. In the cost-conscious world of evidence-based medicine, the added economic burden of additional medications and office visits may or may not improve patient outcomes-much less confer added value. Our advice to fellow shoulder surgeons: Wait for further information, but continue to holistically consider and optimize risk factors for poor soft-tissue healing. Although the addition of postoperative bisphosphonates may improve suture anchor fixation and promote a better foundation for healing, it will not immediately transform your RCR success rates.

Lactobacillus plantarum attenuates glucocorticoid-induced osteoporosis by altering the composition of rat gut microbiota and serum metabolic profile

Introduction

Osteoporosis, one of the most common non-communicable human diseases worldwide, is one of the most prevalent disease of the adult skeleton. Glucocorticoid-induced osteoporosis(GIOP) is the foremost form of secondary osteoporosis, extensively researched due to its prevalence.Probiotics constitute a primary bioactive component within numerous foods, offering promise as a potential biological intervention for preventing and treating osteoporosis. This study aimed to evaluate the beneficial effects of the probiotic Lactobacillus plantarum on bone health and its underlying mechanisms in a rat model of glucocorticoid dexamethasone-induced osteoporosis, using the osteoporosis treatment drug alendronate as a reference.

Methods

We examined the bone microstructure (Micro-CT and HE staining) and analyzed the gut microbiome and serum metabolome in rats.

Results and discussion

The results revealed that L. plantarum treatment significantly restored parameters of bone microstructure, with elevated bone density, increased number and thickness of trabeculae, and decreased Tb.Sp. Gut microbiota sequencing results showed that probiotic treatment increased gut microbial diversity and the ratio of Firmicutes to Bacteroidota decreased. Beneficial bacteria abundance was significantly increased (Lachnospiraceae_NK4A136_group, Ruminococcus, UCG_005, Romboutsia, and Christensenellaceae_R_7_group), and harmful bacteria abundance was significantly decreased (Desulfovibrionaceae). According to the results of serum metabolomics, significant changes in serum metabolites occurred in different groups. These differential metabolites were predominantly enriched within the pathways of Pentose and Glucuronate Interconversions, as well as Propanoate Metabolism. Furthermore, treatment of L. plantarum significantly increased serum levels of Pyrazine and gamma-Glutamylcysteine, which were associated with inhibition of osteoclast formation and promoting osteoblast formation. Lactobacillus plantarum can protect rats from DEX-induced GIOP by mediating the "gut microbial-bone axis" promoting the production of beneficial bacteria and metabolites. Therefore L. plantarum is a potential candidate for the treatment of GIOP.

Prostate cancer bone metastases biology and clinical management (Review)

Prostate cancer (PCa) is one of the most prominent causes of cancer-related mortality in the male population. A highly impactful prognostic factor for patients diagnosed with PCa is the presence or absence of bone metastases. The formation of secondary tumours at the bone is the most commonly observed site for the establishment of PCa metastases and is associated with reduced survival of patients in addition to a cohort of life-debilitating symptoms, including mobility issues and chronic pain. Despite the prevalence of this disease presentation and the high medical relevance of bone metastases, the mechanisms underlying the formation of metastases to the bone and the understanding of what drives the osteotropism exhibited by prostate tumours remain to be fully elucidated. This lack of in-depth understanding manifests in limited effective treatment options for patients with advanced metastatic PCa and culminates in the low rate of survival observed for this sub-set of patients. The present review aims to summarise the most recent promising advances in the understanding of how and why prostate tumours metastasise to the bone, with the ultimate aim of highlighting novel treatment and prognostic targets, which may provide the opportunity to improve the diagnosis and treatment of patients with PCa with bone metastases.

An Evaluation of the Effectiveness of Local Delivery of Zoledronic Acid in Accelerating Bone Healing After the Extraction of Mandibular Third Molars

Background and objective Zoledronic acid (ZA) has been reported to aid with the formation of new bone, inhibit osteoclastic bone resorption, and improve osteoblast proliferation. This split-mouth randomized clinical research aimed to evaluate the effect of the local application of ZA on bone regeneration after the removal of bilateral mandibular third molars. Methods A randomized, split-mouth study involving 12 patients aged 19-35 years requiring extraction of bilaterally mandibular third molars was conducted. The extraction of mandibular third molars on both sides was conducted in one session for all patients. In each participant, a gelatin sponge (Gelfoam) soaked with ZA was randomly applied to one cavity of the extraction socket. A gelatin sponge soaked with normal saline was applied to the opposite cavity; all patients were blinded as to which socket the drug was applied to. The study was conducted over a period of two months. The changes in bone density (BD) in the socket were assessed through cone-beam CT (CBCT) images; two images were taken for each patient at two different time points: immediately after extraction (T0) and after two months (T1). Results BD values in the socket on both sides of extraction increased from T0 to T1. There were statistically significant differences when comparing the amount of change in radiographic BD from T0 to T1 between the two sides of the extraction (p<0.05); the increase in radial BD between the two different time points was more significant in the ZA group. Conclusions Within the limitation of this study, the local application of ZA radiographically improved bone healing in a statistically significant manner and could be a cost-effective and simple way to activate bone regeneration.

Osteogenesis Improvement of Gelatin-Based Nanocomposite Scaffold by Loading Zoledronic Acid

Bisphosphonates (BPs) such as Zoledronic acid (ZA) are a subset of synthetic small molecules, which are now marketed as the main drugs to stimulate the growth and differentiation of osteoblast cells, thereby increasing bone formation as well as preventing bone loss. Also, Halloysite Nanotubes (HNTs)-polymer composites have attracted a lot of attention due to their high surface-to-volume ratio, low density, and high hydrophilicity, and are easily dispersed in hydrophilic biopolymers. In addition, their ability to carry enough amounts of drugs and the ability to control release has been demonstrated. Based on studies, the Gelatin-based scaffold with Halloysite nanotube (HNT) has the capacity as a drug carrier and Zoledronic acid (ZA) sustains release. Previous studies show that using ZA intravenously has some severe side effects and limitations. But by attention to the advantages of its osteogenesis, the current study has been done in order to reduce the side effects of local delivery of it. The 3-dimensional scaffolds were prepared by the Freeze-drying method. Characterization methods such as FE-SEM, FTIR, XRD, and release behavior of the scaffold has been performed to evaluate the features of the scaffolds. In fact, as-prepared Gel-HNT/ZA release 49% ZA in Phosphate Buffered Saline (PBS) within 21 days. The mechanical properties have been increased after adding HNTs and ZA from 10.27 to 26.18 MPa. Also, the water absorption has been increased after adding HNTs and ZA from 1.67 to 5.02 (g/g). Seeded human Adipose stem cells (hASCs) on the prepared scaffolds showed that the ZA effectively elevated the proliferation of the hASCs and also the MTT results proved the non-toxicity of all prepared scaffolds by high cell viability (˃80%). The osteogenic differentiation has been accelerated as displayed by ALP and Ca assay. The results propose that the HNTs-loaded Gelatin scaffold could control the releasing of ZA and its localized delivery at the defect site, simultaneously promoting the mechanical and osteogenesis ability of gelatin-based scaffolds.

Bone Metastases: From Mechanisms to Treatment

OBJECTIVES

Bone metastases are of high clinical relevance because they are a frequent complication of most types of common cancers, such as breast and prostate. The metastatic process is complex, requiring the completion of several different steps to allow successful dissemination and homing. In addition, preparation of the metastatic niche changes the constant cycle of bone matrix formation and degradation, leading to the clinical phenotypes of lytic and sclerotic lesions. We review our current knowledge on this topic and briefly explain the current treatment landscape of bone metastasis.

DATA SOURCES

These include PubMed, international guidelines, and clinician experience.

CONCLUSION

Bone metastases remain a clinical challenge that negatively impacts patients prognosis and quality of life. A comprehensive understanding of the complex molecular mechanisms that results in bone metastasis is the basis for successful treatment of affected patients. The disruption of bone matrix metabolism is already recognized as the prerequisite for metastasis formation, but many open questions remain that need to be addressed in future research to establish individually tailored treatment approaches.

IMPLICATIONS FOR NURSING PRACTICE

Patient-centered therapy of bone metastases requires suitable pharmacological options, and importantly a holistic approach in care delivery across the multidisciplinary team. Nurses provide the cornerstone of the multidisciplinary team and provide the closest and the most frequent contact to the patient and their families to provide timely intervention. Nurses require a basic understanding of the complex physiology of metastasis to inform practice.

A Review Into the Effects of Pamidronic Acid and Zoledronic Acid on the Oral Mucosa in Medication-Related Osteonecrosis of the Jaw

Medication-related osteonecrosis of the jaw (MRONJ) is a growing problem without an effective treatment, presenting as necrotic bone sections exposed via lesions in the overlying soft tissue. There is currently a lack of clarity on how the factors involved in MRONJ development and progression contribute to disease prognosis and outcomes. Bisphosphonates (BPs), the most common cause of MRONJ, affect bone remodeling, angiogenesis, infection, inflammation and soft tissue toxicity, all of which contribute to MRONJ development. This article reviews the cellular mechanisms through which BPs contribute to MRONJ pathology, with a focus on the effects on cells of the oral mucosa. BPs have been shown to reduce cell viability, reduce proliferation, and increase apoptosis in oral keratinocytes and fibroblasts. BPs have also been demonstrated to reduce epithelial thickness and prevent epithelial formation in three-dimensional tissue engineered models of the oral mucosa. This combination of factors demonstrates how BPs lead to the reduced wound healing seen in MRONJ and begins to uncover the mechanisms through which these effects occur. The evidence presented here supports identification of targets which can be used to develop novel treatment strategies to promote soft tissue wound healing and restore mucosal coverage of exposed bone in MRONJ.

Zoledronic acid modulates osteoclast apoptosis through activation of the NF-κB signaling pathway in ovariectomized rats

Bone mass loss (osteoporosis) seen in postmenopausal women is an adverse factor for implant denture. Using an ovariectomized rat model, we studied the mechanism of estrogen-deficiency-caused bone loss and the therapeutic effect of Zoledronic acid. We observed that ovariectomized-caused resorption of bone tissue in the mandible was evident at four weeks and had not fully recovered by 12 weeks post-ovariectomized compared with the sham-operated controls. Further evaluation with a TUNEL assay showed ovariectomized enhanced apoptosis of osteoblasts but inhibited apoptosis of osteoclasts in the mandible. Zoledronic acid given subcutaneously as a single low dose was shown to counteract both of these ovariectomized effects. Immunohistochemical staining showed that ovariectomized induced the protein levels of RANKL and the 65-kD subunit of the NF-κB complex mainly in osteoclasts, as confirmed by staining for TRAP, a marker for osteoclasts, whereas zoledronic acid inhibited these inductions. Western blotting showed that the levels of RANKL, p65, as well as the phosphorylated form of p65, and IκB-α were all higher in the ovariectomized group than in the sham and ovariectomized + zoledronic acid groups at both the 4th- and 12th-week time points in the mandible. These data collectively suggest that ovariectomized causes bone mass loss by enhancing apoptosis of osteoblasts and inhibiting apoptosis of osteoclasts. In osteoclasts, these cellular effects may be achieved by activating RANKL-NF-κB signalling. Moreover, zoledronic acid elicits its therapeutic effects in the mandible by counteracting these cellular and molecular consequences of ovariectomized.

Effect of nitrogen-containing bisphosphonates on osteoclasts and osteoclastogenesis: an ultrastructural study

We have previously indicated that a single injection of alendronate, one of the nitrogen-containing bisphosphonates (NBPs), affects murine hematopoietic processes, such as the shift of erythropoiesis from bone marrow (BM) to spleen, disappearance of BM-resident macrophages, the increase of granulopoiesis in BM and an increase in the number of osteoclasts. NBPs induce apoptosis and the formation of giant osteoclasts in vitro and/or in patients undergoing long-term NBP treatment. Therefore, the time-kinetic effect of NBPs on osteoclasts needs to be clarified. In this study, we examined the effect of alendronate on mouse osteoclasts and osteoclastogenesis. One day after the treatment, osteoclasts lost the clear zone and ruffled borders, and the cell size decreased. After 2 days, the cytoplasm of osteoclasts became electron dense and the nuclei became pyknotic. Some of the cells had fragmented nuclei. After 4 days, osteoclasts had euchromatic nuclei attached to the bone surface. Osteoclasts had no clear zones or ruffled borders. After 7 days, osteoclasts formed giant osteoclasts via the fusion of multinuclear and mononuclear osteoclasts. These results indicate that NBPs affect osteoclasts and osteoclastogenesis via two different mechanisms.

Advances in the occurrence and biotherapy of osteoporosis

Osteoporosis (OP) is a bone metabolic disease, is characterized by degeneration of bone structure and decreased bone mass. It happens in more than 1/3 women and 1/5 men of over than 50 years old, which affects the health and lives of people. The main mechanism of OP is mainly that the dynamic balance between the bone formation and resorption is broken, so that bone resorption is more than bone formation. It is prone to result in bone metabolism disorder. There are many precipitating factor such as elder age, low hormone level, genetic factors and bad hobbies. At the same time, the occurrence of the OP and its complications has different degrees of impact on people's quality of life. Based on the current understanding of the OP, we summarized the etiology, current clinical drugs and potential targeting therapy for OP. Although the research have made many progress in explore what is the novel mechanism and how to improve the effect, there are still many problems in the treatment method that limit its application prospects and need to be solved. In this review, we mainly focus on the mechanism of OP and related research on the targeted treatment of OP. Hopefully, our summary will provide a reference to develop some novel strategies for the target therapy of OP.

Clodronate

Two early observations about the first generation bisphosphonate, clodronate, suggested that it would likely have clinical utility; specifically, it was a more potent anti-resorptive but a less potent inhibitor of mineralisation than its predecessor etidronate. The known mechanism of action differs from that of the later nitrogen-containing bisphosphonates, as clodronate is metabolised intracellularly to a toxic analog of adenosine triphosphate, AppCCl2p, which causes mitochondrial dysfunction, impaired cellular energy metabolism and osteoclast apoptosis. For pre-clinical studies in a variety of disease models, liposomal clodronate has become the agent of choice for macrophage depletion, for example in a recent study to enhance haematopoietic chimerism and donor-specific skin allograft tolerance in a mouse model. For clinical use, clodronate was developed in oral and injectable formulations; while poorly absorbed from the gastro-intestinal tract, its absorption at 1-3% of the administered dose is approximately three-fold higher than for nitrogen-containing bisphosphonates. Following an early setback due to an erroneous association with toxic adverse events, a number of successful clinical studies have established clodronate, predominantly in its oral formulations, as a highly successful treatment in Paget's disease, hypercalcaemia (benign and malignant), multiple myeloma, and early or metastatic breast cancer. Novel uses in other disease areas, including veterinary use, continue to be explored.

Molecular mechanisms of action of bisphosphonates and new insights into their effects outside the skeleton

Bisphosphonates (BP) are a class of calcium-binding drug used to prevent bone resorption in skeletal disorders such as osteoporosis and metastatic bone disease. They act by selectively targeting bone-resorbing osteoclasts and can be grouped into two classes depending on their intracellular mechanisms of action. Simple BPs cause osteoclast apoptosis after cytoplasmic conversion into toxic ATP analogues. In contrast, nitrogen-containing BPs potently inhibit FPP synthase, an enzyme of the mevalonate (cholesterol biosynthesis) pathway. This results in production of a toxic metabolite (ApppI) and the loss of long-chain isoprenoid lipids required for protein prenylation, a process necessary for the function of small GTPase proteins essential for the survival and activity of osteoclasts. In this review we provide a state-of-the-art overview of these mechanisms of action and a historical perspective of how they were discovered. Finally, we challenge the long-held dogma that BPs act only in the skeleton and highlight recent studies that reveal insights into hitherto unknown effects on tumour-associated and tissue-resident macrophages.

Zoledronic Acid Is Not Equally Potent on Osteoclasts Generated From Different Individuals

Zoledronic acid is a bisphosphonate commonly used to treat bone diseases such as osteoporosis and cancer‐induced bone disease. Patients exhibit a variable sensitivity to zoledronic acid; the underlying explanation for this remains unclear. The objective of this study was to obtain more knowledge in this regard. We hypothesized that osteoclasts generated from different individuals would show a variable sensitivity to zoledronic acid in vitro. Osteoclasts were generated using monocytes from 46 healthy female blood donors (40 to 66 years). Matured osteoclasts were reseeded onto bone slices precoated with different concentrations of zoledronic acid. IC50 values were determined based on total eroded bone surface after 3 days of resorption. The IC50 for inhibition of osteoclastic bone resorption varied from 0.06 to 12.57μM zoledronic acid; thus, a more than 200‐fold difference in sensitivity to zoledronic acid among osteoclasts from different individuals was observed. Multiple linear regression analyses showed that the determined IC50 correlated with smoking status, and the average number of nuclei per osteoclast in vitro. Further analyses showed that: (i) increasing protein levels of mature cathepsin K in osteoclast cultures rendered the osteoclasts less sensitive to zoledronic acid; (ii) surprisingly, neither the gene nor the protein expression of farnesyl diphosphate synthase was found to correlate with the IC50; and (iii) trench‐forming osteoclasts were found to be more sensitive to zoledronic acid than pit‐forming osteoclasts within the same cell culture. Thus, we conclude that there indeed is a high degree of variation in the potency of zoledronic acid on osteoclasts when generated from different individuals. We propose that our findings can explain some of the varying clinical efficacy of zoledronic acid therapy observed in patients, and may therefore be of clinical importance, which should be investigated in a clinical trial combining in vitro and in vivo investigations. © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Pharmacogenetics of medication-related osteonecrosis of the jaw: a systematic review and meta-analysis

Medication-related osteonecrosis of the jaw (MRONJ) is a severe complication that can develop in patients treated with anti-resorptive drugs. Although the pathogenesis of MRONJ is still unclear, genetic factors have a demonstrated important role. Thus, the aim of this study was to perform a systematic review on the pharmacogenetics of MRONJ. Studies published until March 2019 were retrieved from eight databases and were selected by two independent reviewers. Evidence on several genetic polymorphisms was summarized and a meta-analysis was conducted when possible. Fourteen studies involving 1515 participants were eligible for systematic review. For CYP2C8 rs1934951, no significant difference was observed between the MRONJ and non-MRONJ groups (odds ratio (OR) 2.04, 95% confidence interval (CI) 0.88-4.73, P=0.09). However, a subgroup analysis based on only multiple myeloma status showed a positive association (OR 3.64, 95% CI 1.29-10.30, P=0.01). PPARG rs1152003 was not differently distributed between groups (OR 0.25, 95% CI 0.01-9.92, P=0.46). Also, VEGF rs3025039 was found to be correlated with the occurrence of MRONJ (OR 0.35, 95% CI 0.15-0.82, P=0.02). CYP2C8 rs1934951 (in multiple myeloma patients) and VEGF rs3025039 are associated with the development of MRONJ in patients treated with bisphosphonates. The results are promising and call for new trials with a larger sample to further explore this growing field.

The Bone Extracellular Matrix as an Ideal Milieu for Cancer Cell Metastases

Bone is a preferential site for cancer metastases, including multiple myeloma, prostate, and breast cancers.The composition of bone, especially the extracellular matrix (ECM), make it an attractive site for cancer cell colonization and survival. The bone ECM is composed of living cells embedded within a matrix composed of both organic and inorganic components. Among the organic components, type I collagen provides the tensile strength of bone. Inorganic components, including hydroxyapatite crystals, are an integral component of bone and provide bone with its rigidity. Under normal circumstances, two of the main cell types in bone, the osteoblasts and osteoclasts, help to maintain bone homeostasis and remodeling through cellular communication and response to biophysical signals from the ECM. However, under pathological conditions, including osteoporosis and cancer, bone remodeling is dysregulated. Once in the bone matrix, disseminated tumor cells utilize normal products of bone remodeling, such as collagen type I, to fuel cancer cell proliferation and lesion outgrowth. Models to study the complex interactions between the bone matrix and metastatic cancer cells are limited. Advances in understanding the interactions between the bone ECM and bone metastatic cancer cells are necessary in order to both regulate and prevent metastatic cancer cell growth in bone.

Zoledronic acid inhibits osteoclast differentiation and function through the regulation of NF-κB and JNK signalling pathways

It is well known that extensive osteoclast formation plays a key role in osteoporosis in post‑menopausal women and the elderly. The suppression of extensive osteoclastogenesis and bone resorption may be an effective preventive strategy for osteoporosis. Zoledronic acid (ZOL) has been indicated to play an essential role in regulating bone mineral density and has already been used in large clinical trials. However, the effects of ZOL on osteoclastogenesis remain to be fully elucidated. Therefore, the present study aimed to determine the effects of ZOL on osteoclastogenesis, and to explore the corresponding signalling pathways. By using a cell viability assay, as well as in vitro osteoclastogenesis, immunofluorescence and resorption pit assays, we demonstrated that ZOL (0.1‑5 µM) suppressed receptor activator of nuclear factor‑κB ligand (RANKL)‑induced osteoclast differentiation and bone resorptive activity. Furthermore, western blot analysis and reverse transcription‑quantitative PCR indicated that ZOL inhibited the RANKL‑induced activation of NF‑κB and the phosphorylation of JNK in RAW264.7 cells, and subsequently decreased the expression of osteoclastogenesis‑associated genes, including calcitonin receptor, tartrate‑resistant acid phosphatase and dendritic cell‑specific transmembrane protein. ZOL inhibited osteoclast formation and resorption in vitro by specifically suppressing NF‑κB and JNK signalling. On the whole, the findings of this study indicate that ZOL may serve as a potential agent for the treatment of osteoclast‑associated diseases, including osteoporosis.

Bisphosphonates and Cancer: A Relationship Beyond the Antiresorptive Effects

Bisphosphonates (BPs) are stable analogues of the Inorganic Pyrophosphate (PPi), an endogenous regulator of bone mineralization, which can resist the hydrolysis in the gastrointestinal tract. Their conformation allows targeting the bone as a result of their three-dimensional structure, which makes them primary agents against osteoclast-mediated bone loss. They are used in many bone pathological conditions, like bone metastasis, because of its ability to modulate bone metabolism into a less favorable place to cancer cell growth, through the inhibition of osteoclastogenesis and bone resorption. This review is focused on the mechanisms of action through which BPs affect the cellular activity and survival, mainly on their antitumoral effects. In conclusion, BPs are considered the primary therapy for skeletal disorders due to its high affinity for bone, but now they are also considered as potential antitumor agents due to its ability to induce tumor cell apoptosis, inhibition of cell adhesion, invasion and proliferation, modulation of the immune system to target and eliminate cancer cells as well as affect the angiogenic mechanisms. Like any other drug, they also have some adverse effects, but the most common, the acute phase reaction, can be minimized with the intake of calcium and vitamin D.

Evaluation of mandibular cortical bone ratio on computed tomography images in patients taking bisphosphonates

Background

Bisphosphonate (BP) has the ability to thicken the cortical bone. In addition, it has been reported that the cortical bone thickened by BP has relation to the medication-related osteonecrosis of the jaw (MRONJ). Therefore, the objective of this article is to analyze the ratio as well as thickness of cortical bone in the mandible using computed tomography (CT) and to evaluate it as the predictive factor of MRONJ.

Methods

The thickness of the cortical bone was measured on a paraxial view of the CT showing the mental foramen in 95 patients: 33 patients with MRONJ (3 males, 30 females), 30 patients taking BP without MRONJ (2 males, 28 females), and 32 controls (9 males, 28 females). Also, the ratios of the cortical bone to the total bone were obtained using the measured values. Based on these results, we compared the difference of mandibular cortical bone ratio between the three groups.

Results

The average cortical bone thickness was measured as 3.81 mm in patients with MRONJ, 3.39 mm in patients taking BP without MRONJ, and 3.23 mm in controls. There was only a significant difference between patients with MRONJ and controls (P < 0.05). On the other hand, the average mandibular cortical bone ratio was measured as 37.9% in patients with MRONJ, 27.9% in patients taking BP without MRONJ, and 23.3% in controls. There was a significant difference between all groups (P < 0.05).

Conclusion

The mandibular cortical bone ratio is large in order of patients with MRONJ, patients taking BP without MRONJ, and controls. This result suggests that the mandibular cortical bone ratio would be very useful to predict the development of MRONJ.

Bone Marrow Microenvironment as a Regulator and Therapeutic Target for Prostate Cancer Bone Metastasis

Bone is the most common site of prostate cancer metastasis. Once prostate cancer cells metastasize to bone, the mortality rate of prostate cancer patients increases significantly. Furthermore, bone metastases produce multiple skeletal complications, including bone pain that impairs the patients' quality of life. Effective therapies for bone metastatic disease are underdeveloped with most current therapies being primarily palliative with modest survival benefit. Although the exact mechanisms through which prostate cancer metastasizes to bone are unclear, growing evidence suggests that the bone marrow microenvironment, particularly its hematopoietic activity, is a significant mediator of prostate cancer bone tropism. Moreover, the bone microenvironment may regulate metastatic prostate cancer cells between dormant and proliferative states. In this review, we discuss (1) how prostate cancer cells interact with the bone microenvironment to establish bone metastases and (2) current and future potential treatments for prostate cancer patients with bone metastases.

Local effect of zoledronic acid on new bone formation in posterolateral spinal fusion with demineralized bone matrix in a murine model

BACKGROUND

Posterolateral spinal fusion is a common orthopaedic surgery performed to treat degenerative and traumatic deformities of the spinal column. In posteriolateral spinal fusion, different osteoinductive demineralized bone matrix products have been previously investigated. We evaluated the effect of locally applied zoledronic acid in combination with commercially available demineralized bone matrix putty on new bone formation in posterolateral spinal fusion in a murine in vivo model.

METHODS

A posterolateral sacral spine fusion in murine model was used to evaluate the new bone formation. We used the sacral spine fusion model to model the clinical situation in which a bone graft or demineralized bone matrix is applied after dorsal instrumentation of the spine. In our study, group 1 received decortications only (n = 10), group 2 received decortication, and absorbable collagen sponge carrier, group 3 received decortication and absorbable collagen sponge carrier with zoledronic acid in dose 10 µg, group 4 received demineralized bone matrix putty (DBM putty) plus decortication (n = 10), and group 5 received DBM putty, decortication and locally applied zoledronic acid in dose 10 µg. Imaging was performed using MicroCT for new bone formation assessment. Also, murine spines were harvested for histopathological analysis 10 weeks after surgery.

RESULTS

The surgery performed through midline posterior approach was reproducible. In group with decortication alone there was no new bone formation. Application of demineralized bone matrix putty alone produced new bone formation which bridged the S1-S4 laminae. Local application of zoledronic acid to demineralized bone matrix putty resulted in significant increase of new bone formation as compared to demineralized bone matrix putty group alone.

CONCLUSIONS

A single local application of zoledronic acid with DBM putty during posterolateral fusion in sacral murine spine model increased significantly new bone formation in situ in our model. Therefore, our results justify further investigations to potentially use local application of zoledronic acid in future clinical studies.

Influence Of Angiogenic Mediators And Bone Remodelling In Paget´s Disease Of Bone

Paget´s disease of bone (PDB) is characterized by increased bone resorption followed by an excessive compensatory bone formation, with an abnormal bone structure with altered mechanical properties. Pagetic bone also has a higher vascularization and marrow fibrosis. Despite of pagetic bone being a highly vascularized tissue, there are no studies on the plasma levels of angiogenic mediators in the different states of the disease; moreover, the effect of PDB treatment on plasma levels of these angiogenic mediators is not very well known. The aim of this study was to analyse plasma levels of cytokines implicated in the increased bone turnover (OPG, RANKL, sclerostin) and hypervascularization (VEGF, PGF, ENG) observed in PDB and their evolution and response to zoledronic acid treatment in 70 PDB patients, 29 with an active disease measured by plasma alkaline phosphatase (ALP). Plasma ALP concentration was higher in active PDB than in inactive PDB patients, whereas there were no differences in OPG, RANKL, sclerostin, VEGF, PGF and ENG plasma levels between active and inactive PDB patients. ALP decreased at 3 and 12 months after zoledronic acid treatment. RANKL levels were reduced and sclerostin levels were increased after 12 months of treatment. PGF levels were lower 12 months after zoledronic acid treatment, whereas there were no differences in plasma VEGF and ENG after zoledronic acid treatment. Summarizing, zoledronic acid treatment is associated to decreases in plasma levels of ALP, RANKL, sclerostin and P1GF in active PDB patients. This treatment may reduce bone turnover and might reduce the pathological vascularisation typical of pagetic bone.

The stimulating effects of polyphenol and protein fractions from jelly fig (Ficus awkeotsang Makino) achenes against proliferation of leukemia cells

This study aimed to investigate the direct and immune-stimulated antiproliferative activities of jelly fig achenes fractions including pectinesterase inhibitors, crude polyphenols extract, and purified polyphenols extract (PP). Beside the measurement of cell viability of U937, the quantity of cytokines in conditioned medium and morphologic changes in leukemia were observed. After surveying all fractions in jelly fig, the obtained fractions of polyphenol exhibited the highest stimulating effects and directly cytotoxic effects against leukemia with the lowest effect found in protein fractions. The leukemia treated by our PP fraction showed dose-dependent response between the concentration and G2/M cell numbers of the U937 cells. The PP fraction had more pronounced effect on immune-stimulated than direct antiproliferative activities. The finding was also supported by morphological analysis by showing the formation of apoptotic bodies and differentiation from immature U937 cells into mature monocytes/macrophages on cells cultured with PP-conditioned medium. In conclusion, polyphenol fraction of pectinesterase inhibitors from jelly fig showed the immune-stimulated antiproliferative activities against U937 cell.

Do topical applications of bisphosphonates improve bone formation in oral implantology? A systematic review

Background

The aim of this systematic literature review was to evaluate the feasibility of topical bisphosphonate application for preserving/enhancing alveolar bone in oral implantology.

Material and Methods

An electronic search was conducted in the PubMed/Medline, EMBASE, Scopus, Web of knowledge, and Google-Scholar databases for articles dated from January 2000 to December 2016. Two reviewers assessed the quality of the studies independently.

Results

A total of 154 abstracts were identified, of which 18 potentially relevant articles were selected; a final total of nine papers were included for analysis. Comparison of the findings of the selected studies was made difficult by the heterogeneity of the articles, all of them animal research papers that showed heterogeneity in the methodologies used and a high or moderate risk of bias.

Conclusions

The topical application of bisphosphonate solution would appear to favor new bone formation in alveolar defects, and boosts the regenerative capacities of biomaterials resulting in increased bone density.

Key words:Alveolar bone, bone regeneration, topical application, biomaterial, bisphosphonates.

Zoledronic acid renders human M1 and M2 macrophages susceptible to Vδ2+ γδ T cell cytotoxicity in a perforin-dependent manner

Vδ2⁺ T cells are a subpopulation of γδ T cells in humans that are cytotoxic towards cells which accumulate isopentenyl pyrophosphate. The nitrogen-containing bisphosphonate, zoledronic acid (ZA), can induce tumour cell lines to accumulate isopentenyl pyrophosphate, thus rendering them more susceptible to Vδ2⁺ T cell cytotoxicity. However, little is known about whether ZA renders other, non-malignant cell types susceptible. In this study we focussed on macrophages (Mϕs), as these cells have been shown to take up ZA. We differentiated peripheral blood monocytes from healthy donors into Mϕs and then treated them with IFN-γ or IL-4 to generate M1 and M2 Mϕs, respectively. We characterised these Mϕs based on their phenotype and cytokine production and then tested whether ZA rendered them susceptible to Vδ2⁺ T cell cytotoxicity. Consistent with the literature, IFN-γ-treated Mϕs expressed higher levels of the M1 markers CD64 and IL-12p70, whereas IL-4-treated Mϕs expressed higher levels of the M2 markers CD206 and chemokine (C–C motif) ligand 18. When treated with ZA, both M1 and M2 Mϕs became susceptible to Vδ2⁺ T cell cytotoxicity. Vδ2⁺ T cells expressed perforin and degranulated in response to ZA-treated Mϕs as shown by mobilisation of CD107a and CD107b to the cell surface. Furthermore, cytotoxicity towards ZA-treated Mϕs was sensitive—at least in part—to the perforin inhibitor concanamycin A. These findings suggest that ZA can render M1 and M2 Mϕs susceptible to Vδ2⁺ T cell cytotoxicity in a perforin-dependent manner, which has important implications regarding the use of ZA in cancer immunotherapy.

Cytoprotective effects of melatonin on zoledronic acid-treated human osteoblasts

OBJECTIVE

To evaluate the cytoprotective effects of melatonin (MLT) on zoledronic acid (ZA)-treated human osteoblasts.

METHODS

Human osteoblasts were exposed to ZA (1, 5, 10, 50, 100 and 300 μM) and MLT (1, 10, 50, 100 y 200 μM) for 24, 48 and 72 h of incubation, to evaluate their effects on cell viability.

RESULTS

As ZA concentration increased, greater reductions in cell viability of human osteoblasts were induced whether at 24, 48 or 72 h incubation. At 24 h incubation with MLT, greatest cell viability was obtained when low dose of MLT was applied (without significant differences); 48 and 72 h incubation presented the greatest cell viability with the highest MLT concentrations (100 and 200 μM). MLT at concentrations of 100 and 200 μM would appear to have a certain cytoprotective effect on ZA-treated human osteoblasts with low concentrations of ZA (1 y 5 μM), whether at 24, 48 or 72 h; however, at ZA concentrations ≥10 μM the possible cytoprotective effects of MLT were low at 24 h incubation.

CONCLUSIONS

MLT has a cytoprotective effect on ZA-treated human osteoblasts and could represent a promising preventative alternative for patients at risk of bisphosphonate-related osteonecrosis of the jaw.

Reactive oxygen species are required for zoledronic acid-induced apoptosis in osteoclast precursors and mature osteoclast-like cells

Inhibiting osteoclasts and osteoclast precursors to reduce bone resorption is an important strategy to treat osteoclast-related diseases, such as osteoporosis, inflammatory bone loss, and malignant bone metastasis. However, the mechanism by which apoptosis is induced in the osteoclasts and their precursors are not completely understood. Here, we used nitrogen-containing bisphosphonate zoledronic acid (ZA) to induce cell apoptosis in human and murine osteoclast precursors and mature osteoclast-like cells. Caspase-3-mediated cell apoptosis occurred following the ZA (100 μM) treatment. Reactive oxygen species (ROS) were also generated in a time-dependent manner. Following knock-down of the p47^phox expression, which is required for ROS activation, or co-treatment with the ROS inhibitor, N-acetyl-L-cysteine, ZA-induced apoptosis was significantly suppressed in both osteoclast precursors and mature osteoclast-like cells. The ROS-activated mitogen-activated protein kinases pathways did not trigger cell apoptosis. However, a ROS-regulated Mcl-1 decrease simultaneously with glycogen synthase kinase (GSK)-3β promoted cell apoptosis. These findings show that ZA induces apoptosis in osteoclast precursors and mature osteoclast-like cells by triggering ROS- and GSK-3β-mediated Mcl-1 down-regulation.

Toll-like receptor 9 expression is associated with breast cancer sensitivity to the growth inhibitory effects of bisphosphonates in vitro and in vivo

Bisphosphonates are standard treatments for bone metastases. When given in the adjuvant setting, they reduce breast cancer mortality and recurrence in bone but only among post-menopausal patients. Optimal drug use would require biomarker-based patient selection. Such biomarkers are not yet in clinical use. Based on the similarities in inflammatory responses to bisphosphonates and Toll-like receptor (TLR) agonists, we hypothesized that TLR9 expression may affect bisphosphonate responses in cells. We compared bisphosphonate effects in breast cancer cell lines with low or high TLR9 expression. We discovered that cells with decreased TLR9 expression are significantly more sensitive to the growth-inhibitory effects of bisphosphonates in vitro and in vivo. Furthermore, cancer growth-promoting effects seen with some bisphosphonates in some control shRNA cells were not detected in TLR9 shRNA cells. These differences were not associated with inhibition of Rap1A prenylation or p38 phosphorylation, which are known markers for bisphosphonate activity. However, TLR9 shRNA cells exhibited increased sensitivity to ApppI, a metabolite that accumulates in cells after bisphosphonate treatment. We conclude that decreased TLR9-expression sensitizes breast cancer cells to the growth inhibitory effects of bisphosphonates. Our results suggest that TLR9 should be studied as a potential biomarker for adjuvant bisphosphonate sensitivity among breast cancer patients.

Does pamidronate enhance the osteogenesis in mesenchymal stem cells derived from fibrous hamartoma in congenital pseudarthrosis of the tibia?

Neurofibromatosis type 1 (NF1) is a commonly occurring genetic disorder in children. Mutation in the NF1 gene has its implication in poor osteoblastic capabilities. We hypothesised that pamidronate will enhance the osteoblastic potential of the mesenchymal stem cells (MSCs) derived from lipofibromatosis tissue of children with congenital pseudarthrosis tibia (CPT) associated with NF1. In this study, bone marrow MSCs (BM MSCs) and CPT MSCs were obtained from three patients undergoing salvage surgeries/bone grafting (healthy controls) and those undergoing excision of the hamartoma and corrective surgeries respectively. The effects of pamidronate (0, 10 nM, 100 nM and 1 μM) on cell proliferation, toxicity and differentiation potential were assessed and the outcome was measured by staining and gene expression. Our outcome showed that CPT MSCs had more proliferation rate as compared to BM MSCs. All 3 doses of pamidronate did not cause any toxicity to the cells in both the groups. The CPT MSCs showed less differentiation with pamidronate compared to the healthy control MSCs. This was quantitated by staining and gene expression analysis. Therefore, supplementation with pamidronate alone will not aid in bone formation in patients diagnosed with CPT. An additional stimulus is required to enhance bone formation.

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First study demonstrating the differentiation potential of MSCs derived from the hamartoma using pamidronate

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The CPT MSCs have lower osteogenic potential as compared to BM MSCs.

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The osteoblastic response does not improve with the addition of pamidronate (1 μM) in CPT MSCs.

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Pamidronate enhances osteogenic differentiation in normal BM MSCs.

Association Between Geranylgeranyl Pyrophosphate Synthase Gene Polymorphisms and Bone Phenotypes and Response to Alendronate Treatment in Chinese Osteoporotic Women

Objective To investigate the relationship between geranylgeranyl pyrophosphate synthase (GGPPS) gene polymorphisms and bone response to alendronate in Chinese osteoporotic women.Methods A total of 639 postmenopausal women with osteoporosis or osteopenia were included and randomly received treatment of low dose (70 mg per two weeks) or standard dose (70 mg weekly) of alendronate for one year. The six tag single nucleotide polymorphisms of GGPPS gene were identified. Bone mineral density (BMD), serum cross-linked C-telopeptide of type I collagen (β-CTX), and total alkaline phosphatase (ALP) were measured before and after treatment. GGPPS gene polymorphisms and the changes of BMD and bone turnover markers after treatment were analyzed.Results rs10925503 polymorphism of GGPPS gene was correlated to serum β-CTX levels at baseline, and patients with TT genotype had significantly higher serum β-CTX level than those with TC or CC genotype (all P<0.05). No correlation was found between polymorphisms of GGPPS gene and serum total ALP levels, as well as BMD at baseline. After 12 months of treatment, lumbar spine and hip BMD increased and serum bone turnover markers decreased significantly (P<0.01), and without obvious differences between the low dose and standard dose groups (all P>0.05). However, GGPPS gene polymorphisms were uncorrelated to percentage changes of BMD, serum total ALP, and β-CTX levels (all P>0.05).Conclusion GGPPS gene polymorphisms are correlated to osteoclasts activity, but all tag single nucleotide polymorphisms of GGPPS gene have no influence on the skeletal response to alendronate treatment.

Revival of nitrogen-containing bisphosphonate-induced inhibition of osteoclastogenesis and osteoclast function by water-soluble microfibrous borate glass

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a serious skeletal complication associated with the long-term oral or intravenous use of nitrogen-containing bisphosphonates (N-BPs). Here, we investigated the effects of an ionic cocktail prepared from water-soluble microfibrous borate glass on neutralizing the inhibitory effects of two heterocyclic N-BPs, risedronate or zoledronic acid, on osteoclastogenesis, apoptosis of differentiated osteoclasts and osteoclast function. Cell growth and proliferation assays were first performed on RAW 264.7 cells to optimize the concentrations of the ionic cocktail and N-BPs to be used for static cell culture. The pre-osteoclasts were then stimulated with RANKL to differentiate into osteoclasts. The effects of the ionic cocktail and N-BPs on osteoclast differentiation, apoptosis and function were subsequently examined using 3 series of experiments conducted at the gene, protein, morphological and functional levels. After concentration optimization, the ionic cocktail was found to partially reverse N-BP-induced inhibition of osteoclastogenesis, stimulation of osteoclasts apoptosis and reduction of osteoclast resorptive activity. Ultrastructural examination of osteoclasts that had been exposed to either N-BP identified classical features of late apoptosis and secondary necrosis, while osteoclasts exposed simultaneously to the concentration-optimized ionic cocktail and N-BPs exhibited only signs of early apoptosis that were possibly reversible. Taken together, the results of the 4 series of experiments indicate that the ionic cocktail produced from dissolution of borate glass dressings has the potential to rescue the adverse effects of heterocyclic N-BPs on osteoclast differentiation and function. These results warrant further confirmation using dynamic cell culture and small animal BRONJ models.

STATEMENT OF SIGNIFICANCE

Long-term oral and intravenous use of nitrogen-containing bisphosphonates (N-BPs) may result in bisphosphonate-related osteonecrosis of the jaw (BRONJ) due to the suppression of normal bone turnover. There is no effective treatment for such a complication to date. This work reported the use of an ionic cocktail derived from water-soluble microfibrous borate glass to revert heterocyclic N-BP-induced inhibition of osteoclastogenesis, stimulation of osteoclasts apoptosis and reduction of osteoclasts resorption in static cell culture condition. This ionic cocktail may have the potential to be further developed into a new adjunctive treatment for BRONJ.

Role of a nitrogenous bisphosphonate (local delivery) incorporated vitreous coating (with/without polymer) on surgical grade SS316L implant material to improve fixation at the damaged tissue site

This study demonstrates the material and biological properties of a unique osteogenic drug eluting (local) coating on load bearing SS316L implant material with a tunable release profile.

Live imaging of osteoclast inhibition by bisphosphonates in a medaka osteoporosis model

Osteoclasts are bone-resorbing cells derived from the monocyte/macrophage lineage. Excess osteoclast activity leads to reduced bone mineral density, a hallmark of diseases such as osteoporosis. Processes that regulate osteoclast activity are therefore targeted in current osteoporosis therapies. To identify and characterize drugs for treatment of bone diseases, suitable in vivo models are needed to complement cell-culture assays. We have previously reported transgenic medaka lines expressing the osteoclast-inducing factor receptor activator of nuclear factor κB ligand (Rankl) under control of a heat shock-inducible promoter. Forced Rankl expression resulted in ectopic osteoclast formation, as visualized by live imaging in fluorescent reporter lines. This led to increased bone resorption and a dramatic reduction of mineralized matrix similar to the situation in humans with osteoporosis. In an attempt to establish the medaka as an in vivo model for osteoporosis drug screening, we treated Rankl-expressing larvae with etidronate and alendronate, two bisphosphonates commonly used in human osteoporosis therapy. Using live imaging, we observed an efficient, dose-dependent inhibition of osteoclast activity, which resulted in the maintenance of bone integrity despite an excess of osteoclast formation. Strikingly, we also found that bone recovery was efficiently promoted after inhibition of osteoclast activity and that osteoblast distribution was altered, suggesting effects on osteoblast-osteoclast coupling. Our data show that transgenic medaka lines are suitable in vivo models for the characterization of antiresorptive or bone-anabolic compounds by live imaging and for screening of novel osteoporosis drugs.

Bone Tumor Environment as a Potential Therapeutic Target in Ewing Sarcoma

Ewing sarcoma is the second most common pediatric bone tumor, with three cases per million worldwide. In clinical terms, Ewing sarcoma is an aggressive, rapidly fatal malignancy that mainly develops not only in osseous sites (85%) but also in extra-skeletal soft tissue. It spreads naturally to the lungs, bones, and bone marrow with poor prognosis in the two latter cases. Bone lesions from primary or secondary (metastases) tumors are characterized by extensive bone remodeling, more often due to osteolysis. Osteoclast activation and subsequent bone resorption are responsible for the clinical features of bone tumors, including pain, vertebral collapse, and spinal cord compression. Based on the “vicious cycle” concept of tumor cells and bone resorbing cells, drugs, which target osteoclasts, may be promising agents as adjuvant setting for treating bone tumors, including Ewing sarcoma. There is also increasing evidence that cellular and molecular protagonists present in the bone microenvironment play a part in establishing a favorable “niche” for tumor initiation and progression. The purpose of this review is to discuss the potential therapeutic value of drugs targeting the bone tumor microenvironment in Ewing sarcoma. The first part of the review will focus on targeting the bone resorbing function of osteoclasts by means of bisphosphonates or drugs blocking the pro-resorbing cytokine receptor activator of NF-kappa B ligand. Second, the role of this peculiar hypoxic microenvironment will be discussed in the context of resistance to chemotherapy, escape from the immune system, or neo-angiogenesis. Therapeutic interventions based on these specificities could be then proposed in the context of Ewing sarcoma.

Effect of alendronate on the mandible and long bones: an experimental study in vivo

BACKGROUND

Bisphosphonates are anticatabolic agents that inhibit bone resorption and are widely used to treat osteoporosis and bone metastases in adults. They are also used in young patients with diseases like osteogenesis imperfecta or juvenile osteoporosis. Bone modeling/remodeling is elevated in growing subjects, and inhibition of osteoclastic activity has been shown to interfere with growth. Thus, our objective was to evaluate the effect of alendronate (ALN) on growing animals.

METHODS

Healthy male Wistar rats, aged 1 mo, received ALN or vehicle for 8 wk. Serum levels (calcemia, phosphatemia, and total alkaline phosphatase) were determined. Morphometric (rat: femur and tibia weight and length and hemimandible growth) and histomorphometric parameters (thickness of tibial epiphyseal cartilage and each cartilage zone, interradicular bone volume in the first lower molar, trabeculae volume, percentage of bone and cartilage, and osteoclast number in mandibular condyles) were assessed.

RESULTS

ALN caused a significant decrease in femur and tibia length, tibial cartilage thickness, and longitudinal growth of hemimandibles. It increased interradicular bone volume and mandibular condyle trabeculae volume, increasing the percentage of cartilage and osteoclast number.

CONCLUSION

These findings indicate that administration of ALN to growing animals alters the endochondral ossification process, and thus alters growth.

Oestrogen receptor positive breast cancer metastasis to bone: inhibition by targeting the bone microenvironment in vivo

Clinical trials have shown that adjuvant Zoledronic acid (ZOL) reduces the development of bone metastases irrespective of ER status. However, post-menopausal patients show anti-tumour benefit with ZOL whereas pre-menopausal patients do not. Here we have developed in vivo models of spontaneous ER+ve breast cancer metastasis to bone and investigated the effects of ZOL and oestrogen on tumour cell dissemination and growth. ER+ve (MCF7, T47D) or ER-ve (MDA-MB-231) cells were administered by inter-mammary or inter-cardiac injection into female nude mice ± estradiol. Mice were administered saline or 100 μg/kg ZOL weekly. Tumour growth, dissemination of tumour cells in blood, bone and bone turnover were monitored by luciferase imaging, histology, flow cytometry, two-photon microscopy, micro-CT and TRAP/P1NP ELISA. Estradiol induced metastasis of ER+ve cells to bone in 80-100 % of animals whereas bone metastases from ER-ve cells were unaffected. Administration of ZOL had no effect on tumour growth in the fat pad but significantly inhibited dissemination of ER+ve tumour cells to bone and frequency of bone metastasis. Estradiol and ZOL increased bone volume via different mechanisms: Estradiol increased activity of bone forming osteoblasts whereas administration of ZOL to estradiol supplemented mice decreased osteoclast activity and returned osteoblast activity to levels comparable to that of saline treated mice. ER-ve cells require increased osteoclast activity to grow in bone whereas ER+ve cells do not. Zol does not affect ER+ve tumour growth in soft tissue, however, inhibition of bone turnover by ZOL reduced dissemination and growth of ER+ve breast cancer cells in bone.

Inhibitory effect of bisphosphonate on osteoclast function contributes to improved skeletal pain in ovariectomized mice

The aim of this study was to evaluate skeletal pain associated with osteoporosis and to examine the inhibitory effect of bisphosphonate (BP) on pain in an ovariectomized (OVX) mouse model. We evaluated skeletal pain in OVX mice through an examination of pain-like behavior as well as immunohistochemical findings. In addition, we assessed the effects of alendronate (ALN), a potent osteoclast inhibitor, on those parameters. The OVX mice showed a decrease in the pain threshold value, and an increase in the number of c-Fos immunoreactive neurons in laminae I-II of the dorsal horn of the spinal cord. Alendronate caused an increase in the pain threshold value and inhibited c-Fos expression. The serum level of tartrate-resistant acid phosphatase 5b, a marker of osteoclast activity, was significantly negatively correlated with the pain threshold value. Furthermore, we found that an antagonist of the transient receptor potential channel vanilloid subfamily member 1, which is an acid-sensing nociceptor, improved pain-like behavior in OVX mice. These results indicated that the inhibitory effect of BP on osteoclast function might contribute to an improvement in skeletal pain in osteoporosis patients.

Ulnar fractures with bisphosphonate therapy: a systematic review of published case reports

SUMMARY

A systematic review of eight ulnar fractures in seven patients with bisphosphonate therapy was performed to describe the characteristics and predisposing factors. The proximal ulna is likely to be fractured, especially in the dominant limb of elderly female patients using walking aids after 7 to 15 years of bisphosphonate use.

INTRODUCTION

Long-term bisphosphonate use has been suggested to result in decreased bone remodelling and increased risk of atypical fractures. While the relationship between bisphosphonate use and atypical femoral fractures has been extensively studied, there is relative rarity and unawareness of these fractures in the forearm. We conducted a systematic review of existing case reports to better describe the characteristics and predisposing factors for fractures occurring in patients with bisphosphonate therapy.

METHODS

The systematic review was conducted according to PRISMA guidelines. All studies with ulnar fractures in individuals with history of bisphosphonate use were included, with data extracted and analysed in totality.

RESULTS

Seven patients with eight fractures are included. Predisposing factors include elderly females requiring walking aids. There is a propensity for the proximal ulna to be fractured, especially in the dominant limb used for ambulation or transfer. All patients were on bisphosphonate for 7 to 15 years. All fractures were atraumatic, non-comminuted, transverse in configuration, had localised periosteal or endosteal thickening at the fracture site and generalised cortical thickening of the diaphysis.

CONCLUSION

Ulnar fractures in patients with bisphosphonate therapy demonstrate features similar to those described for atypical femoral fractures, suggesting that these fractures could also possibly be due to bisphosphonate use. However, the ulna appears to be able to tolerate longer periods of alendronate use prior to fracture development. The mechanism and characteristics of these fractures additionally suggest the presence of repetitive stress that accumulates over time due to suppressed bone remodelling in patients on bisphosphonates, eventually resulting in these fractures.

Mevalonates restore zoledronic acid-induced osteoclastogenesis inhibition

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is likely to be caused by continuous imperfection of bone healing after surgical treatments in patients with long-term administration of nitrogen-containing bisphosphonates (NBPs). NBPs inhibit osteoclastic bone resorption by impairing the mevalonic acid sterol pathway in osteoclasts. Thus, we hypothesized that exogenous mevalonic acid metabolites restore the inhibitory effects of NBPs on osteoclastogenesis and bone remodeling. To clarify the effects of mevalonic acid metabolites, especially geranylgeranyl pyrophosphate (GGPP) and geranylgeranyl transferase substrate geranylgeranyl acid (GGOH), we examined the effects of zoledronic acid with or without GGOH or GGPP on osteoclast differentiation, multinucleation, and bone mineral deposition in tooth-extracted sockets. Zoledronic acid decreased the number of tartrate-resistant acid phosphatase (TRAP)-positive multinuclear cells derived from mouse osteoclast precursors treated with receptor activator of nuclear factor-κB ligand and macrophage colony-stimulating factor. Zoledronic acid simultaneously suppressed not only the expressions of osteoclastic differentiation-related molecules such as TRAP, cathepsin K, calcitonin receptor, and vacuolar H-ATPase but also those of multinucleation-related molecules such as dendrocyte-expressed 7 transmembrane proteins and osteoclast stimulatory transmembrane protein. Treatment with GGOH or GGPP, but not farnesyl acid, restored the zoledronic acid-inhibited number of TRAP-positive multinuclear cells together with the expressions of these molecules. Although intraperitoneal administration of zoledronic acid and lipopolysaccharide into mice appeared to induce BRONJ-like lesions with empty bone lacunae and decreased mineral deposition in tooth-extracted socket, both GGOH and GGPP partially restored the inhibitory effects on zoledronic acid-related mineral deposition. These results suggest the potential of mevalonic acid metabolites as therapeutic agents for BRONJ.

The regulation of osteoclast function and bone resorption by small GTPases

Osteoclasts are multinucleated cells that are responsible for resorption of bone, and increased activity of these cells is associated with several common bone diseases, including postmenopausal osteoporosis. Upon adhesion to bone, osteoclasts become polarized and reorganise their cytoskeleton and membrane to form unique domains including the sealing zone (SZ), which is a dense ring of F-actin-rich podosomes delimiting the ruffled border (RB), where protons and proteases are secreted to demineralise and degrade the bone matrix, respectively. These processes are dependent on the activity of small GTPases. Rho GTPases are well known to control the organization of F-actin and adhesion structures of different cell types, affecting subsequently their migration. In osteoclasts, RhoA, Rac, Cdc42, RhoU and also Arf6 regulate podosome assembly and their organization into the SZ. By contrast, the formation of the RB involves vesicular trafficking pathways that are regulated by the Rab family of GTPases, in particular lysosomal Rab7. Finally, osteoclast survival is dependent on the activity of Ras GTPases. The correct function of almost all these GTPases is absolutely dependent on post-translational prenylation, which enables them to localize to specific target membranes. Bisphosphonate drugs, which are widely used in the treatment of bone diseases such as osteoporosis, act by preventing the prenylation of small GTPases, resulting in the loss of the SZ and RB and therefore inhibition of osteoclast activity, as well as inducing osteoclast apoptosis. In this review we summarize current understanding of the role of specific prenylated small GTPases in osteoclast polarization, function and survival.

Activation of p38 MAPK-regulated Bcl-xL signaling increases survival against zoledronic acid-induced apoptosis in osteoclast precursors

The nitrogen-containing bisphosphonate zoledronic acid (ZA) induces apoptosis in osteoclasts and inhibits osteoclast-mediated bone resorption. It is widely used to treat osteoporosis. However, some patients are less responsive to ZA treatment, and the mechanisms of resistance are still unclear. Here, we identified that murine osteoclast precursors may develop resistance to ZA-induced apoptosis. These resistant cells survived the apoptotic effect of ZA following an increase in anti-apoptotic Bcl-xL. Pharmacologically inhibiting Bcl-xL facilitated ZA-induced apoptosis. Treatment with ZA activated p38 MAPK, increasing Bcl-xL expression and cell survival. Nuclear import of β-catenin regulated by p38 MAPK determined Bcl-xL mRNA expression and cell survival in response to ZA. ZA also inactivated glycogen synthase kinase (GSK)-3β, a negative upstream regulator of β-catenin, in a p38 MAPK-mediated manner. Synergistic pharmacological inhibition of p38 MAPK with ZA attenuated receptor activator of nuclear factor kappa-B ligand (RANKL)-induced osteoclast differentiation and facilitated ZA-induced apoptosis. These results demonstrate that elevated Bcl-xL expression mediated by p38 MAPK-regulated GSK-3β/β-catenin signaling is required for cell survival of ZA-induced apoptosis in both osteoclast precursors and osteoclasts. Finally, we demonstrated that inhibiting p38 MAPK-mediated pathway enhanced ZA effect on increasing the bone mineral density of ovariectomized mice. This result suggests that targeting these pathways may represent a potential therapeutic strategy.

Zoledronic acid in combination with alfacalcidol has additive effects on trabecular microarchitecture and mechanical properties in osteopenic ovariectomized rats

BACKGROUND

We conducted the present study to investigate the therapeutic effects of the antiresorptive agent zoledronic acid (ZOL), alone and in combination with alfacalcidol (ALF), in a rat model of postmenopausal osteoporosis.

METHODS

Female Wistar rats were ovariectomized (OVX) or sham-operated at 3 months of age. Twelve weeks post surgery, rats were randomized into six groups: (1) sham + vehicle, (2) OVX + vehicle, (3) OVX + ZOL (100 μg/kg, i.v. single dose), (4) OVX + ZOL (50 μg/kg, i.v. single dose), (5) OVX + ALF (0.5 μg/kg, oral gauge daily) and (6) OVX + ZOL (50 μg/kg, i.v. single dose) + ALF (0.5 μg/kg, oral gauge daily) for 12 weeks. After treatment, we evaluated the mechanical properties of the lumbar vertebra and femoral mid-shaft. Femurs were also tested for bone density, porosity and trabecular micro-architecture. Biochemical markers in serum and urine were also determined.

RESULTS

With respect to improvement in the mechanical strength of the lumbar spine and the femoral mid-shaft, the combination treatment of ZOL and ALF was more effective than each administered as a monotherapy. Moreover, combination therapy using ZOL and ALF preserved the trabecular micro-architecture and cortical bone porosity. Furthermore, the combination treatment of ZOL and ALF corrected the decrease in serum calcium and increase in serum alkaline phosphatase and the tartarate-resistant acid phosphatase level better than single-drug therapy using ZOL or ALF in OVX rats. In addition, the combination treatment of ZOL and ALF corrected the increase in urine calcium, phosphorous and creatinine levels better than single-drug therapy using ZOL or ALF in OVX rats.

CONCLUSIONS

These data suggest that the combination treatment of ZOL and ALF has a therapeutic advantage over each monotherapy for the treatment of osteoporosis.

Prostaglandin D(2) induces apoptosis of human osteoclasts through ERK1/2 and Akt signaling pathways

In a recent study we have shown that prostaglandin D2 (PGD2) induces human osteoclast (OC) apoptosis through the activation of the chemoattractant receptor homologous molecule expressed on T-helper type 2 cell (CRTH2) receptor and the intrinsic apoptotic pathway. However, the molecular mechanisms underlying this response remain elusive. The objective of this study is to investigate the intracellular signaling pathways mediating PGD2-induced OC apoptosis. OCs were generated by in vitro differentiation of human peripheral blood mononuclear cells (PBMCs), and then treated with or without the selective inhibitors of mitogen-activated protein kinase-extracellular signal-regulated kinase (ERK) kinase, (MEK)-1/2, phosphatidylinositol3-kinase (PI3K) and NF-κB/IκB kinase-2 (IKK2) prior to the treatments of PGD2 as well as its agonists and antagonists. Fluorogenic substrate assay and immunoblotting were performed to determine the caspase-3 activity and key proteins involved in Akt, ERK1/2 and NF-κB signaling pathways. Treatments with both PGD2 and a CRTH2 agonist decreased ERK1/2 (Thr202/Tyr204) and Akt (Ser473) phosphorylation, whereas both treatments increased β-arrestin-1 phosphorylation (Ser412) in the presence of naproxen, which was used to eliminate endogenous prostaglandin production. In the absence of naproxen, treatment with a CRTH2 antagonist increased both ERK1/2 and Akt phosphorylations, and reduced the phosphorylation of β-arrestin-1. Treatment of OCs with a selective MEK-1/2 inhibitor increased caspase-3 activity and OC apoptosis induced by both PGD2 and a CRTH2 agonist. Moreover, a CRTH2 antagonist diminished the selective MEK-1/2 inhibitor-induced increase in caspase-3 activity in the presence of endogenous prostaglandins. In addition, treatment of OCs with a selective PI3K inhibitor decreased ERK1/2 (Thr202/Tyr204) phosphorylation caused by PGD2, whereas increased ERK1/2 (Thr202/Tyr204) phosphorylation by a CRTH2 antagonist was attenuated with a PI3K inhibitor treatment. The DP receptor was not implicated in any of the parameters evaluated. Treatment of OCs with PGD2 as well as its receptor agonists and antagonists did not alter the phosphorylation of RelA/p65 (Ser536). Moreover, the caspase-3 activity was not altered in OCs treated with a selective IKK2/NF-κB inhibitor. In conclusion, endogenous or exogenous PGD2 induces CRTH2-dependent apoptosis in human differentiated OCs; β-arrestin-1, ERK1/2, and Akt, but not IKK2/NF-κB are probably implicated in the signaling pathways of this receptor in the model studied.