Alendronate reduces adhesion of human osteoclast-like cells to bone and bone protein-coated surfaces

Assessing bone formation on hydrophilic and hydrophobic implant surfaces in a murine model treated with bisphosphonates

OBJECTIVE

To evaluate the osseointegration of implants with hydrophobic (HFB) and hydrophilic (HFL) surfaces in a murine model of high-dose bisphosphonates (BPs).

MATERIALS AND METHODS

Sixty-four rats were randomly allocated into four groups: control group with HFB implants (CG-HFB), control group with HFL implants (CG-HFL), BP group with HFB implants (BP-HFB), and BP group with HFL implants (BP-HFL). Animals were euthanized after 15 and 45 days (n=8). The dependent variables assessed were the removal torque (biomechanical analysis), the bone volume around the implants (%BV/TV) (microtomographic analysis), the bone-implant contact (%BIC), the bone between the threads (%BBT) (histomorphometric analysis), and the expression of bone metabolism markers (immunohistochemistry analysis).

RESULTS

The CG-HFL and BP-HFL groups presented higher removal torque than the CG-HFB and BP-HFB implants. The %BIC of the CG-HFL surfaces was slightly higher than that of the CG-HFB implants. The BP-HFB and BP-HFL groups presented a higher %BIC than that of the CG-HFB and CG-HFL groups (p<0.001). BP therapy also increased the %BBT at both implant surfaces. Higher levels of ALP were observed in the matrix region of bone tissue on the HFL surfaces than on the HFB surfaces.

CONCLUSION

Both surfaces enable osseointegration in rats under BP therapy.

CLINICAL RELEVANCE

The study demonstrates that hydrophobic (HFB) and hydrophilic (HFL) implant surfaces can promote osseointegration in rats undergoing bisphosphonate therapy. The HFL surfaces exhibited improved biomechanical performance, higher bone-implant contact, and increased bone volume, suggesting their potential clinical relevance for implant success in individuals on bisphosphonate treatment.

Similarities and Differences between Osteoclast-Mediated Functional Activation of NK, CD3+ T, and γδ T Cells from Humans, Humanized-BLT Mice, and WT Mice

This study is focused on assessing the activation in NK, CD3+ T, and γδ T cells when they interact with osteoclasts (OCs) and monocytes in the presence or absence of zoledronate (ZOL), both in humans and WT mice. OCs resulted in increased IFN-γ secretion in NK, CD3+ T, and γδ T cells, however, the significantly highest increase was seen when cells were co-cultured with ZOL-treated OCs. Our previous studies have demonstrated increased IFN-γ secretion in the peripheral blood-derived immune cells of bisphosphonate-related osteonecrosis of the jaw (BRONJ) mice model. This could be due to increased OCs-induced activation of immune cells with ZOL treatment. We also observed increased IFN-γ secretion in humanized-BLT (hu-BLT) mice NK cells when were co-cultured with OCs or monocytes, and higher IFN-γ secretion levels were seen in the presence of OCs or ZOL-treated OCs. In addition, similar effects on IFN-γ secretion levels of NK, CD3+ T, and γδ T cells were seen whether cells were co-cultured with allogeneic OCs or autologous OCs.

Osteophilic and Dual-Regulated Alendronate-Gene Lipoplexes for Reversing Bone Loss

The pathogenesis of postmenopausal osteoporosis (PMOP) is mainly determined by the adhesion of osteoclasts to the bone matrix and the involvement of various molecules in bone resorption. The dual regulation strategy of the physical barriers of bone matrix and intracellular gene regulation generated by advanced biomaterials is a decent alternative for the treatment of PMOP. Herein, for the first time, it is identified that hsa-miR-378i/mmu-miR-378a-3p are closely associated with PMOP. Then, an osteophilic and dual-regulated alendronate-gene lipoplex (antagomir@Aln-Lipo), composed of medicative alendronate-functionalized liposomal vehicle and encapsulated specific microRNAs is engineered, for bone-targeting delivery of genes to achieve combined mitigation of bone loss. Alendronate targets hydroxyapatite in the bone matrix and occupies the adhesion site of osteoclasts, thus providing the "physical barriers". Antagomir is coupled precisely to specific endogenous microRNAs, thus providing the "genetic signals". These functionalized lipoplexes exhibited long-term stability and good transfection efficiency. It is proven that antagomir@Aln-Lipo could synergistically regulate osteoclastogenesis and bone resorption in vitro and in vivo. Furthermore, intravenous injection of antagomir@Aln-Lipo efficiently reverses bone loss through a dual mechanism driven by alendronate and antagomir-378a-3p. In conclusion, the osteophilic and dual-regulated antagomir@Aln-Lipo offers a brand-new bifunctional strategy for the precise treatment of PMOP.

Bioactivity, Molecular Mechanism, and Targeted Delivery of Flavonoids for Bone Loss

Skeletal disabilities are a prominent burden on the present population with an increasing life span. Advances in osteopathy have provided various medical support for bone-related diseases, including pharmacological and prosthesis interventions. However, therapeutics and post-surgery complications are often reported due to side effects associated with modern-day therapies. Thus, therapies utilizing natural means with fewer toxic or other side effects are the key to acceptable interventions. Flavonoids constitute a class of bioactive compounds found in dietary supplements, and their pharmacological attributes have been well appreciated. Recently, flavonoids' role is gaining renowned interest for its effect on bone remodeling. A wide range of flavonoids has been found to play a pivotal role in the major bone signaling pathways, such as wingless-related integration site (Wnt)/β-catenin, bone morphogenetic protein (BMP)/transforming growth factor (TGF)-β, mitogen-activated protein kinase (MAPK), etc. However, the reduced bioavailability and the absorption of flavonoids are the major limitations inhibiting their use against bone-related complications. Recent utilization of nanotechnological approaches and other delivery methods (biomaterial scaffolds, micelles) to target and control release can enhance the absorption and bioavailability of flavonoids. Thus, we have tried to recapitulate the understanding of the role of flavonoids in regulating signaling mechanisms affecting bone remodeling and various delivery methods utilized to enhance their therapeutical potential in treating bone loss.

Augmentation of IFN-γ by bone marrow derived immune cells in the presence of severe suppression of IFN-γ in gingivae induced by zoledronic acid and denosumab in Hu-BLT mice model of ONJ

Introduction

The potential mechanisms governing drug induced osteonecrosis of the jaw (ONJ) is not well understood, and is one of the objectives of this study. Thus, we tested the release of IFN-γ within different immune compartments including bone marrow and gingivae upon treatment with zoledronic acid (ZOL) and denosumab which are known to induce ONJ in susceptible individuals.

Methods

We used humanized-BLT mouse model for the in-vivo studies reported in this paper. To determine the effects of zoledronic acid and denosumab on IFN-γ secretion and NK cell-mediated cytotoxicity; peripheral blood, bone marrow, spleen and gingiva were obtained after the injection of ZOL and denosumab in mice.

Results

Percentages of B cells are much higher in wild-type mice whereas the proportions of immune subsets in humans and reconstituted hu-BLT peripheral-blood are similar. Therefore, hu-BLT mice are preferable model to study human disease, in particular, immune-pathologies induced by ZOL and denosumab. Both agents resulted in a severe suppression of IFN-γ in the gingiva, whereas they heightened the release of IFN-γ and NK cell-mediated cytotoxicity by the BM-derived immune cells. ZOL increased the IFN-γ secretion by the spleen and peripheral blood immune cells, whereas denosumab decreased the release IFN-γ by these cells significantly.

Discussion

ZOL and denosumab may likely suppress IFN-γ secretion in gingiva through different mechanisms. In addition, to the suppression of IFN-γ secretion, denosumab mediated effect could in part be due to the decrease in the bone resorptive function of osteoclasts due to the induction of antibody dependent cellular cytotoxicity and lysis of osteoclasts, whereas ZOL is able to mediate cell death of osteoclasts directly. Suppression of IFN-gamma in gingiva is largely responsible for the inhibition of immune cell function, leading to dysregulated osteoblastic and osteoclastic activities. Restoration of IFN-gamma in the local microenvironment may result in establishment of homeostatic balance in the gingiva and prevention of osteonecrosis of jaw.

Bisphosphonate use is associated with a decreased joint narrowing rate in the non-arthritic hip

Aims

The preventive effects of bisphosphonates on articular cartilage in non-arthritic joints are unclear. This study aimed to investigate the effects of oral bisphosphonates on the rate of joint space narrowing in the non-arthritic hip.

Methods

We retrospectively reviewed standing whole-leg radiographs from patients who underwent knee arthroplasties from 2012 to 2020 at our institute. Patients with previous hip surgery, Kellgren–Lawrence grade ≥ II hip osteoarthritis, hip dysplasia, or rheumatoid arthritis were excluded. The rate of hip joint space narrowing was measured in 398 patients (796 hips), and the effects of the use of bisphosphonates were examined using the multivariate regression model and the propensity score matching (1:2) model.

Results

A total of 45 of 398 (11.3%) eligible patients were taking an oral bisphosphonate at the time of knee surgery, with a mean age of 75.8 years (SD 6.2) in bisphosphonate users and 75.7 years (SD 6.8) in non-users. The mean joint space narrowing rate was 0.04 mm/year (SD 0.11) in bisphosphonate users and 0.12 mm/year (SD 0.25) in non-users (p < 0.001). In the multivariate model, age (standardized coefficient = 0.0867, p = 0.016) and the use of a bisphosphonate (standardized coefficient = −0.182, p < 0.001) were associated with the joint space narrowing rate. After successfully matching 43 bisphosphonate users and 86 non-users, the joint narrowing rate was smaller in bisphosphonate users (p < 0.001).

Conclusion

The use of bisphosphonates is associated with decreased joint degeneration in non-arthritic hips after knee arthroplasty. Bisphosphonates slow joint degeneration, thus maintaining the thickness of joint cartilage in the normal joint or during the early phase of osteoarthritis. Cite this article: Bone Joint Res 2022;11(11):826–834.

Practical guidance for new multiple myeloma treatment regimens: A nursing perspective

As is the case for solid tumors, treatment paradigms have shifted from non-specific chemotherapeutic agents towards novel targeted drugs in the treatment of patients with multiple myeloma (MM). Currently, multiple targeted therapies are available to treat patients augmenting the arsenal of modalities which also includes chemotherapy, immunotherapy, radiation therapy, hematopoietic stem cell transplantation (HSCST) and chimeric antigen T-cell therapy (CAR-T). These novel, targeted agents have dramatically increased optimism for patients, who may now be treated over many years with successive regimens. As fortunate as we are to have these new therapies available for our patients, this advantage is juxtaposed with the challenges involved with delivering them safely. While each class of agents has demonstrated efficacy, in terms of response rates and survival, they also exert class effects which pose risks for toxicity. In addition, newer generation agents within the classes often have slightly different toxicity profiles than did their predecessors. These factors must be addressed, and their risks mitigated by the multidisciplinary team. This review presents a summary of the evolution of drug development for MM. For each targeted agent, the efficacy data from pivotal trials and highlights of the risks that were demonstrated in trials, as well as during post-marketing surveillance, are presented. Specific risks associated with agents within the classes, that are not shared with all new class members, are described. A table presenting these potential risks, with recommended nursing actions to mitigate toxicity, is provided as a quick reference that nurses may use during the planning, and provision, of patient care.

Potential Effects of Exosomes and Their MicroRNA Carrier on Osteoporosis

Osteoporosis is a typical localized or systemic skeletal disease in the clinic, mainly characterized by the weakness of bone formation and the increase of bone resorption, resulting in the decrease of bone mineral density (BMD), and frequently occurs in postmenopausal women. With the growth of the aging population, the risk of osteoporosis or even osteoporotic fracture brings great economic pressure on society and families. Although anti-osteoporosis drugs have been developed, there are still some side effects in the treatment group. Hence, that is a compelling need for more reasonable therapeutic strategies. Exosomes are nanosized extracellular vesicles (EVs), secreted by virtually all types of cells in vivo, which play an important role in intercellular communication. Compared with conventional drugs and stem cells transplantation therapy, exosomes have apparent advantages of lower toxicity and immunogenicity. Exosomes contain many functional molecules, such as proteins, lipids, mRNAs, microRNAs (miRNAs), which can be transferred into recipient cells to regulate a series of signaling pathways and influence physiological and pathological behavior. In this review, we briefly summarize the current knowledge of exosomes and the therapeutic potential of exosomal miRNAs derived from mesenchymal stem cells (MSCs), osteoblasts, osteoclasts, and macrophages in osteoporosis. Finally, a prospect of new treatment strategies for osteoporosis using new biomaterial scaffolds combined with exosomes is also given.

Does Bisphosphonate Increase the Sclerosis of Tibial Subchondral Bone in the Progression of Knee Osteoarthritis-A Propensity Score Matching Cohort Study Based on Osteoarthritis Initiative

Bisphosphonate has great potential in KOA therapy, but whether the anti-resorption mechanism of bisphosphonate aggravates sclerosis of subchondral bone remains unclear. We found that bisphosphonate use did not increase sclerosis of subchondral bone in established KOA, perhaps resolving some concerns about bisphosphonate in patients with KOA. Introduction: Most studies have focused on the protective effect of bisphosphonate on early knee osteoarthritis (KOA) through its anti-resorption mechanism in osteoclasts. However, late KOA has a decreased rate of resorption, which is the opposite of early KOA. The risk of subchondral bone sclerosis in late KOA after using bisphosphonate has not been investigated using morphometry. Methods: Forty-five patients who had ever used bisphosphonate (or 33 patients with current use) were matched with controls through propensity matching methods, including age, body mass index (BMI), sex, health status (12-Item Short Form Survey physical health score), physical activity level (Physical Activity Scale for the Elderly score), vitamin D use, and calcium use. At the baseline and 12-month (or 18-month) follow-up, bone mineral density (BMD) of the tibia and hip was measured by dual-energy X-ray absorptiometry (DXA), and medial tibial subchondral bone morphometry: bone volume fraction (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), and trabecular separation (Tb.Sp) were calculated based on 3-T trabecular MRI. Data were obtained from the Bone Ancillary Study in the Osteoarthritis Initiative (OAI) project. Results: The yearly percentage change in hip BMD of the current bisphosphonate-use group was significantly greater than that of the non-bisphosphonate-use group (0.7% vs. -1%, P = 0.02). The other outcomes (BV/TV, Tb.N, Tb.Sp, Tb.Th, tibia medial BMD, and tibia lateral BMD) between the two groups presented no significant difference. The non-bisphosphonate-use group experienced a significant increase in Tb.Th [2%, 95% CI = (1%, 4%), P = 0.01], while the bisphosphonate-use group presented no significant change [1%, 95% CI = (-2%, 4%), P = 0.54]. Conclusions: Bisphosphonate use did not increase sclerosis of subchondral bone in established KOA. Bisphosphonate might have a stage-dependent effect on subchondral bone in KOA initiation and progression.

Engineered osteoclasts resorb necrotic alveolar bone in anti-RANKL antibody-treated mice

Medication-related osteonecrosis of the jaw (MRONJ) is a serious side effect of antiresorptive medications such as denosumab (humanized anti-RANKL antibody), yet its pathophysiology remains elusive. It has been posited that inhibition of osteoclastic bone resorption leads to the pathological sequelae of dead bone accumulation, impaired new bone formation, and poor wound healing in MRONJ, but this hypothesis has not been definitively tested. We previously engineered myeloid precursors with a conditional receptor activator of nuclear factor kappa-Β intracellular domain (iRANK cells), which differentiate into osteoclasts in response to a chemical inducer of dimerization (CID) independently of RANKL. In this study, we showed that CID-treated iRANK cells differentiated into osteoclasts and robustly resorbed mineralized surfaces even in the presence of anti-RANKL antibody in vitro. We then developed a tooth extraction-triggered MRONJ model in nude mice using anti-RANKL antibody to deplete osteoclasts. This model was used to determine whether reconstitution of engineered osteoclasts within sockets could prevent specific pathological features of MRONJ. Locally delivered iRANK cells successfully differentiated into multinucleated osteoclasts in response to CID treatment in vivo as measured by green fluorescent protein (GFP), tartrate-resistant acid phosphatase (TRAP), carbonic anhydrase II, matrix metallopeptidase 9 (MMP-9), and cathepsin K staining. Sockets treated with iRANK cells + CID had significantly more osteoclasts and less necrotic bone than those receiving iRANK cells alone. These data support the hypothesis that osteoclast deficiency leads to accumulation of necrotic bone in MRONJ.

Osteoporosis therapies and their mechanisms of action (Review)

Osteoporosis is a common disease that affects millions of patients worldwide and is most common in menopausal women. The main characteristics of osteoporosis are low bone density and increased risk of fractures due to deterioration of the bone architecture. Osteoporosis is a chronic disease that is difficult to treat; thus, investigations into novel effective therapeutic methods are required. A number of studies have focused on determining the most effective treatment options for this disease. There are several treatment options for osteoporosis that differ depending on the characteristics of the disease, and these include both well-established and newly developed drugs. The present review focuses on the various drugs available for osteoporosis, the associated mechanisms of action and the methods of administration.

Inhibitory Effects of Alendronate on Adhesion and Viability of Preosteoblast Cells on Titanium Discs

Objective  This study aimed to investigate the effects of alendronate (ALN; a bisphosphonate) on adhesion and viability of preosteoblasts using different cell passages on sandblasted and acid-etched (SLA) Ti surfaces.

Materials and Methods  Preosteoblast, MC3T3, cells (passage 42; P42 and passage 62; P62) were cultured with ALN (1 and 5 µM) on cell culture plate for 7 days. Cells were lifted, counted, and seeded on SLA Ti surfaces. Cells were incubated on the discs for 6 hours to examine cell adhesion by using confocal microscopy and for 24 hours to determine cell viability by using MTT assay.

Results  ALN interfered with cell adhesion on Ti surfaces by reducing the cell number in both cell passages. Nuclei of untreated cells showed oval shape, whereas some nuclei of ALN-treated cells demonstrated crescent and condensed appearance. ALN at 1 and 5 µM significantly decreased nuclear area and perimeter in P42, while ALN at 5 µM reduced nuclear area and perimeter in P62. After 24 hours, cells (P42) grown on Ti surfaces showed decreased cell viability when culturing with 5 µM ALN.

Conclusion  ALN reduced cell adhesion and viability of preosteoblasts on Ti surfaces. ALN treatment seemed to exert higher inhibitory effects on nuclear shape and size as well as cell viability in lower cell passage. This led to the reduction in cell to implant surface interaction after encountering bisphosphonate treatment.

Local delivery therapies as adjuvants to non-surgical periodontal treatment of periodontitis grade C: a systematic review

OBJECTIVES

The aim of this article was to perform a systematic review on the effectiveness of local adjuvant therapies in the treatment of aggressive periodontitis (AgP), now reported as periodontitis grade C.

MATERIALS AND METHODS

The authors selected randomized clinical trials of AgP patients who received local therapy as adjuvants to non-surgical periodontal with a duration of at least 90 days. Seven databases were searched up to January 2020. The gain in clinical attachment level (CAL) and reduction of probing depth (PD) were the outcomes of interest.

RESULTS

Of the 3583 studies found, only five articles were included in the qualitative analysis. Among the substances analyzed, only 1.2 mg of simvastatin gel (SMV) (1.2 mg/0.1 ml), 1% of alendronate gel (ALN) (10 mg/ml), and 25% metronidazole gel (MTZ) (Elyzol^@) showed a significant decrease in the probing depth when compared with their respective control groups. The gain CAL was shown using 1.2 mg SMV gel (1.2 mg/0.1 ml) and 1% ALN gel (10 mg/ml).

CONCLUSION

Although 1.2 mg SMV gel (1.2 mg/0.1 ml), 1% ALN gel (10 mg/ml), and 25% MTZ gel (Elyzol) have shown better results, local therapies adjuvant to SRP the data found were limited. Future clinical studies with appreciable methodological quality should be conducted.

CLINICAL RELEVANCE

Despite some benefits of local delivery therapy, up to now, it has not been possible to prove the efficacy of local therapy as an adjunct to standard treatment of AgP (periodontitis grade C).

Mineral and Bone Disease in Kidney Transplant Recipients

PURPOSE OF REVIEW

Despite metabolic improvements following kidney transplantation, transplant recipients still often suffer from complex mineral and bone disease after transplantation.

RECENT FINDINGS

The pathophysiology of post-transplant disease is unique, secondary to underlying pre-transplant mineral and bone disease, immunosuppression, and changing kidney function. Changes in modern immunosuppression regimens continue to alter the clinical picture. Modern management includes reducing cumulative steroid exposure and correcting the biochemical abnormalities in mineral metabolism. While bone mineral density screening appears to help predict fracture risk and anti-osteoporotic therapy appears to have a positive effect on bone mineral density, more data regarding specific treatment is necessary. Patients with mineral and bone disease after kidney transplantation require special care in order to properly manage and mitigate their mineral and bone disease. Recent changes in clinical management of transplant patients may also be changing the implications on patients' mineral and bone disease.

Preventive Effect of Phosphodiesterase Inhibitor Pentoxifylline Against Medication-Related Osteonecrosis of the Jaw: An Animal Study

PURPOSE

The aim of this experimental study was to investigate the prophylactic effect of pentoxifylline (PTX) on medication-related osteonecrosis of the jaw (MRONJ).

MATERIALS AND METHODS

Female Sprague-Dawley rats (n = 33) received zoledronic acid (ZA) for 8 weeks to create an osteonecrosis model. The left mandibular second molars were extracted and the recovery period lasted 8 weeks before sacrifice. PTX was intraperitoneally administered to prevent MRONJ. The specimens were histopathologically and histomorphometrically evaluated.

RESULTS

Histomorphometrically, between the control and ZA groups, there was no statistically significant difference in total bone volume (P = .999), but there was a statistically significant difference in bone ratio in the extraction sockets (P < .001). A comparison of the bone ratio of the ZA group with the ZA/PTX group (PTX administered after extraction) showed no statistically significant difference (P = .69), but there was a statistically significant difference with the ZA/PTX/PTX group (PTX administered before and after extraction; P = .008). Histopathologically, between the control and ZA groups, there were statistically significant differences for inflammation (P = .013), vascularization (P = .022), hemorrhage (P = .025), and regeneration (P = .008). Between the ZA and ZA/PTX groups, there were no statistically significant differences for inflammation (P = .536), vascularization (P = .642), hemorrhage (P = .765), and regeneration (P = .127). Between the ZA and ZA/PTX/PTX groups, there were statistically significant differences for inflammation (P = .017), vascularization (P = .04), hemorrhage (P = .044), and regeneration (P = .04).

CONCLUSION

In this experimental model of MRONJ, it might be concluded that although PTX, given after tooth extraction, improves new bone formation that positively affects bone healing, it is not prophylactic. However, PTX given before tooth extraction is prophylactic. Therefore, PTX might affect healing in a positive way by optimizing the inflammatory response.

[Research progress on bisphosphonate-related osteonecrosis of the jaws]

Bisphosphonates (BPs), as potent drugs inhibiting bone resorption, have been widely used for treatment of several diseases. In recent years, dentists and oral and maxillofacial surgeons reported continuously increasing cases of bisphosphonate-related osteonecrosis of the jaws (BRONJ). This disease is clinically characterized by exposed bones, formation of sequestrum, pain, and halitosis. Provided that pathogenesis of BRONJ is unclear, effective treatments for this disease are currently unavailable. Thus, prevention plays an important role in the management of BRONJ. This review summarizes research progress on pathogenesis, risk factors, clinical characteristics, treatment, and prevention of this condition.

The effect of bisphosphonate treatment on osteoclast precursor cells in postmenopausal osteoporosis: The TRIO study

Bisphosphonates are used to treat bone disease characterised by increased bone resorption by inhibiting the activity of mature osteoclasts, resulting in decreased bone turnover. Bisphosphonates may also reduce the population of osteoclast precursor cells. Our aims were to investigate the effect of bisphosphonates on i) osteoclast precursor cells and ii) circulating cytokine and cytokine receptor in postmenopausal women with osteoporosis compared with healthy premenopausal women. Participants were 62 postmenopausal women (mean age 66) from a 48-week parallel group trial of bisphosphonates. They received ibandronate 150mg/month (n=22), alendronate 70mg/week (n=19) or risedronate 35mg/week (n=21). Fasting blood was collected at baseline, weeks 1 and 48. At baseline, blood was also collected from 25 healthy premenopausal women (mean age 37) to constitute a control group. Peripheral blood mononuclear cells were extracted and stained for CD14, M-CSFR, CD11b and TNFRII receptors. Flow cytometry was used to identify cells expressing CD14⁺ and M-CSFR⁺ or CD11b⁺ or TNFRII⁺. RANKL and OPG were measured to evaluate potential mediation of the bisphosphonate effect. After 48weeks of treatment, there was a decrease in the percentage of cells expressing M-CSFR and CD11b receptors by 53% and 49% respectively (p<0.01). Cells expressing M-CSFR and CD11b were decreased with ibandronate and risedronate after 48weeks to the lower part of the premenopausal reference interval. These effects were not significantly different between each of the treatment groups. There was no significant effect on RANKL and OPG throughout the study period. Bisphosphonates inhibit bone resorption in the short-term by direct action on mature osteoclasts. There is also a later effect mediated in part by a reduction in the population of circulating osteoclast precursors.

Comparative clinicoradiographical evaluation of effect of aminobisphosphonate (sodium alendronate) on peri-implant bone status: Controlled clinical trial

Aim:

The present study aims to compare the peri-implant bone status around immediately loaded dental implants treated with aminobisphosphonate solution and untreated control implants in terms of clinical and radiographical parameters.

Materials and Methods:

A total of 24 patients were randomly divided equally into two groups. This study was conducted in accordance to the Helsinki's declaration of 1975, revised in 2000, and with the approval of the institutional ethical committee. In the control group after preparation, osteotomy sites were irrigated with normal saline solution, whereas in the test group osteotomy sites were irrigated with modified bisphosphonate solution and then TRX-OP, Hi-Tec dental implants were inserted. Clinical parameters, such as modified plaque and gingival index, probing depth, mobility, and radiographic parameters were recorded at baseline (0), 3, 6, and 9 months. Data analysis was performed using the Statistical Package for the Social Sciences version 17 for windows, and the statistical techniques employed were repeated measures analysis of variance, independent sample t-test, and paired sample t-test.

Results:

Reduction in mean radiographic bone levels (height) was observed on the mesial and distal aspect of the control group in comparison to its baseline at all intervals. In the test group, there was reduction in mean radiographic bone levels on mesial and distal aspect of the implant site in comparison to its baseline till 6-month follow up, however, at 9 month, there was gain in bone level on both mesial and distal aspect of implant. This represents the effectiveness of sodium alendronate in enhancing the bone formation. On comparison, between both groups on mesial and distal aspect of implants, statistically significant differences were observed at 3 and 9 months on mesial and distal aspect, respectively, without any clinical evidence of mobility in the test group.

Conclusion:

Implant site treated with aminobisphosphonate solution represents greater efficacy in enhancing bone formation when used as an irrigant; thus, it is considered beneficial in implant dentistry.

Recurrent Monostotic Fibrous Dysplasia in the Mandible

Fibrous dysplasia (FD) is a condition in which normal bone marrow is replaced by an abnormal proliferation of new fibrous connective tissue. Female patient, white, 20 years old, attended the dental clinic reporting a slow increase in volume in the right mandible region over the last 5 years. She was examined by imaging: the panoramic X-ray revealed a lesion with the appearance of ground glass while the cone-beam computed tomography showed an extensive lesion in the region of the right hemimandible. The histopathological examination was compatible with fibrous dysplasia. Bone gammagraphy was indicated, plus an endocrinological study to eliminate polyostotic forms, which produced a negative result. Monostotic fibrous dysplasia in the right hemimandible was diagnosed. Conservative surgery was carried out and after 1 year recurrence of the tumour was observed. We may conclude that conservative surgery might not be the best choice for treatment for monostotic fibrous dysplasia in the mandible and that other options must be considered, such as radical surgery or the use of bisphosphonates. In our study, we may also conclude that it is very important to explain to the patient the possibility of recurrence of the lesion and the need for monitoring with periodic imaging studies.

Management of osteoporosis in rheumatoid arthritis patients

INTRODUCTION

In rheumatoid arthritis (RA) patients, the risk of both vertebral and non-vertebral fractures is roughly doubled, which is for an important part caused by inflammation-mediated amplification of bone loss and by immobilization. New treatments have become available in the last two decades to treat both RA and osteoporosis.

AREAS COVERED

Epidemiology and assessment of osteoporosis and fracture risk (including the influence of RA disease activity and bone-influencing medications such as glucocorticoids), the importance of vertebral fracture assessment in addition to bone density measurement in patients with RA, the use of disease-modifying antirheumatic drugs and their effects on generalized bone loss, and current and possible future anti-osteoporotic pharmacotherapeutic options are discussed with special focus on RA.

EXPERT OPINION

Assessment of osteoporosis in RA patients should include evaluation of the effects of disease activity and bone-influencing medications such as (the dose of) glucocorticoids, above standard risk factors for fractures or osteoporosis as defined by the FRAX instrument. Disease-modifying antirheumatic drugs are now well able to control disease activity using treat to target strategies. This lowering of disease activity by antirheumatic medications such as anti-TNF-α results in hampering of generalized bone loss; however, no fracture data are currently available. When treating osteoporosis in RA patients, additional focus should be on calcium supplementation, particularly in glucocorticoid users, and also on sufficient vitamin D use. Several anti-osteoporotic medications are now on the market; oral bisphosphonates are most commonly used, but in recent years, more agents have entered the market such as the parenteral antiresorptives denosumab (twice yearly) and zoledronic acid (once yearly), and the anabolic agent parathyroid hormone analogues. New agents, such as odanacatib and monoclonal antibodies against sclerostin, are now being tested and will most likely enlarge the possibilities of osteoporosis treatment in RA patients.

Bisphosphonate associated osteonecrosis of the jaw: an update on pathophysiology, risk factors, and treatment

Osteonecrosis of the jaw in patients treated with bisphosphonates is a relatively rare but well known complication at maxillofacial units around the world. It has been speculated that the medication, especially long-term i.v. bisphosphonate treatment, could cause sterile necrosis of the jaws. The aim of this narrative review of the literature was to elaborate on the pathological mechanisms behind the condition and also to gather an update on incidence, risk factors, and treatment of bisphosphonate associated osteonecrosis of the jaw. In total, ninety-one articles were reviewed. All were published in internationally recognized journals with referee systems. We can conclude that necrotic lesions in the jaw seem to be following upon exposure of bone, for example, after tooth extractions, while other interventions like implant placement do not increase the risk of osteonecrosis. Since exposure to the bacterial environment in the oral cavity seems essential for the development of necrotic lesions, we believe that the condition is in fact chronic osteomyelitis and should be treated accordingly.

Targeting TGFβ signaling in subchondral bone and articular cartilage homeostasis

Osteoarthritis (OA) is the most common degenerative joint disease and no disease-modifying therapy for OA is currently available. Targeting articular cartilage alone may not be sufficient to halt this disease progression. Articular cartilage and subchondral bone act as a functional unit. Increasing evidence indicates that transforming growth factor β (TGFβ) plays a crucial role in maintaining homeostasis of both articular cartilage and subchondral bone. Activation of extracellular matrix (ECM) latent TGFβ at the appropriate time and location is a prerequisite for its function. Aberrant activation of TGFβ in the subchondral bone in response to an abnormal mechanical loading environment induces formation of osteroid islets at the onset of OA. As a result, alteration of subchondral bone structure changes the stress distribution on the articular cartilage and leads to its degeneration. Thus, inhibition of TGFβ activity in the subchondral bone may provide a new avenue of treatment for OA. In this review we will discuss the role of TGFβ in the homeostasis of articular cartilage and subchondral bone as a novel target for OA therapy.

The effect of alendronate on the expression of important cell factors in osteoclasts

This study investigated the effects of alendronate (ALN) on critical cell factors in osteoclasts. RAW 264.7 cells were induced by sRANKL to change to mature osteoclasts. On the sixth day of incubation, the osteoclasts were treated with ALN at various concentrations and for different incubation times. The concentration groups included 10-5 M, 10-6 M and 10-7 M ALN, respectively. The cells were incubated for 0 (control group), 2, 4, 6 and 8 h for each dose group. The mRNA and protein expression of tartrate‑resistant acid phosphatase, carbonic anhydrase II, osteoclast‑associated receptor and FAS/FASL genes in osteoclasts was analyzed. A concentration- and time‑dependent decrease in the mRNA and protein expression levels of the five genes was observed, and no significant difference between the two control groups was observed (P>0.05). Notably, significant differences between any two experimental groups were observed (P<0.05). Thus, ALN significantly decreased the expression of critical factors involved in osteoclast function.

Effects of combined treatment with eldecalcitol and alendronate on bone mass, mechanical properties, and bone histomorphometry in ovariectomized rats: a comparison with alfacalcidol and alendronate

Eldecalcitol (ELD), a 2β-hydroxypropyloxy derivative of 1α,25 (OH) 2D3, inhibits bone resorption more potently than alfacalcidol (ALF) while maintaining osteoblastic function in an ovariectomized (OVX) osteoporosis rat model. Alendronate (ALN), which is the most common bisphosphonate used for the treatment of osteoporosis, increases the bone mineral density (BMD) by suppressing bone resorption. In this study, we investigated the effects of combination treatments with ELD and ALN or with ALF and ALN on bone mass and strength in OVX rats. Seventy female rats, 32 weeks old, were assigned to seven groups: (1) a sham-operated control group; (2) an OVX-control group; (3) an ELD group; (4) an ALF group; (5) an ALN group; (6) an ELD+ALN group; and (7) an ALF+ALN group. OVX rats were orally treated with ELD (0.015 μg/kg), ALF (0.0375 μg/kg), or ALN (0.2mg/kg) daily for 12 weeks. In both the lumbar spine and the femur, ELD and ALF monotherapy significantly increased the BMD, and ELD+ALN and ALF+ALN significantly increased the BMD, compared with ALN monotherapy, as an additive effect. In particular, ELD+ALN resulted in a significantly higher BMD than ALF+ALN in the femur. On mechanical testing of the lumbar spine, ELD and ALF monotherapy significantly increased the ultimate load, and ELD+ALN and ALF+ALN significantly increased the ultimate load compared with ALN monotherapy. In the femur, ELD, ELD+ALN, and ALF+ALN treatment significantly increased the ultimate load, compared with the OVX-control group, and ELD+ALN resulted in a significantly higher ultimate load than ALN monotherapy. A histomorphometric analysis showed that ELD monotherapy and ELD+ALN combination therapy had a potent inhibitory effect on bone resorption parameters (osteoclast surface and eroded surface), while maintaining bone formation parameters (osteoblast surface and osteoid surface). By contrast, ALF and ALF+ALN significantly lowered the histological parameters of both bone resorption and formation. These results suggested that ELD or ALF used in combination with ALN has therapeutic advantages over ALN monotherapy, with ELD+ALN combination treatment producing an especially beneficial anti-osteoporotic effect by inhibiting osteoclastic bone resorption and maintaining osteoblastic function, compared with ALF+ALN combination treatment.

Osteoclast activity modulates B-cell development in the bone marrow

B-cell development is dependent on the interactions between B-cell precursors and bone marrow stromal cells, but the role of osteoclasts (OCLs) in this process remains unknown. B lymphocytopenia is a characteristic of osteopetrosis, suggesting a modulation of B lymphopoiesis by OCL activity. To address this question, we first rescued OCL function in osteopetrotic oc/oc mice by dendritic cell transfer, leading to a restoration of both bone phenotype and B-cell development. To further explore the link between OCL activity and B lymphopoiesis, we induced osteopetrosis in normal mice by injections of zoledronic acid (ZA), an inhibitor of bone resorption. B-cell number decreased specifically in the bone marrow of ZA-treated mice. ZA did not directly affect B-cell differentiation, proliferation and apoptosis, but induced a decrease in the expression of CXCL12 and IL-7 by stromal cells, associated with reduced osteoblastic engagement. Equivalent low osteoblastic engagement in oc/oc mice confirmed that it resulted from the reduced OCL activity rather than from a direct effect of ZA on osteoblasts. These dramatic alterations of the bone microenvironment were disadvantageous for B lymphopoiesis, leading to retention of B-cell progenitors outside of their bone marrow niches in the ZA-induced osteopetrotic model. Altogether, our data revealed that OCLs modulate B-cell development in the bone marrow by controlling the bone microenvironment and the fate of osteoblasts. They provide novel basis for the regulation of the retention of B cells in their niche by OCL activity.

Alendronate reduces osteoclast precursors in osteoporosis

This study evaluates the effect of alendronate on osteoclastogenesis, cytokine production, and bone resorption in postmenopausal women. We suggest that it acts on mature bone resorbing osteoclasts after 3 months of treatment, whereas, after 1 year, it diminishes their formation by reducing their precursors and serum RANKL.

INTRODUCTION

Osteoclasts are the target cells of bisphosphonates, though the most drug-sensitive steps of their formation and activity have not been determined. The present study evaluates the effect of alendronate on osteoclastogenesis, cytokine production, and bone resorption in postmenopausal women.

METHODS

The study was conducted on 35 osteoporotic women; 15 were pretreated with alendronate 70 mg/week, whereas, 20 were treated with calcium 1 g/day and vitamin D 800 IU/day. After 3 months, 30 received alendonate 70/mg, vitamin D 2800 IU/week, and calcium 1 g/day for 12 months (combined therapy), whereas, the other five patients remained on calcium 1 g/day and vitamin D 800 IU/day. The following parameters were assessed before and after therapy: changes in bone resorption markers, circulating osteoclast precursors, formation of osteoclasts in peripheral blood mononuclear cell cultures, their viability, and variations in cytokines production.

RESULTS

After 3 months of alendronate, there was no significant reduction in the number of osteoclast precursors, osteoclast formation and viability, and cytokine levels, whereas, there was a significant reduction of bone resorption markers. One year of the combined therapy, on the other hand, reduced osteoclast precursors, osteoclast formation, and serum RANKL, whereas, calcium plus vitamin D alone had no effect.

CONCLUSIONS

We suggest that alendronate mainly acts on mature bone resorbing osteoclasts in the short term, whereas, its long-term administration diminishes their formation by reducing their precursors and serum RANKL.

Effects of combination treatment with alendronate and vitamin K(2) on bone mineral density and strength in ovariectomized mice

Bisphosphonates increase bone mineral density (BMD) by suppressing remodeling space and elongating the duration of mineralization. Menatetrenone (vitamin K(2)) reduces the incidence of fractures by improving bone quality through enhanced gamma-carboxylation of bone glutamic acid residues of osteocalcin in osteoporotic patients. This study investigated the effects of combination treatment with alendronate (ALN) and vitamin K(2) on BMD and bone strength in ovariectomized (OVX) mice. Thirty-three female mice, 16 weeks of age, were assigned to four groups: (1) OVX-control group; (2) oral vitamin K(2) group; (3) subcutaneous ALN group; and (4) ALN + vitamin K(2) group. The treatment was started 4 weeks after OVX and continued for 4 weeks. BMD, geometric parameters measured by peripheral quantitative computed tomography, and mechanical strength at the femoral metaphysis and mid-diaphysis were evaluated after an 8-week treatment period. ALN alone significantly increased total BMD (20%, P < 0.05) and trabecular BMD (25%, P < 0.05), but not the mechanical parameters of the femur, compared with the OVX-control group. Combination treatment with ALN and vitamin K(2) increased not only total BMD (15%, P < 0.05) and trabecular BMD (32%, P < 0.05) but also maximum load (33%, P < 0.05) and breaking energy (25%, P < 0.05) of compression test at the distal metaphysis, and maximum load (20%, P < 0.05) and breaking force (33%, P < 0.05) of three-point bending test at the mid-diaphysis compared with the OVX-control group. These results suggest that ALN, alone or in combination with vitamin K(2), showed significant improvement in BMD, but that the combination treatment was more effective than ALN alone for improving bone strength in OVX mice.

Atrial fibrillation and bisphosphonate therapy

Bisphosphonates are the most commonly used treatment for osteoporosis and have proven efficacy in the reduction of vertebral and nonvertebral fractures. Recently, concerns have been raised about a possible association between bisphosphonate therapy and atrial fibrillation (AF) following the report of a significant increase in risk of serious AF in women treated with zoledronic acid in the HORIZON study. Subsequent studies have produced conflicting results but have not excluded the possibility of such an association. Currently there is no direct evidence that bisphosphonates exert either acute or chronic effects on cardiac electrophysiology. Nevertheless, altered intracellular electrolyte homeostasis and proinflammatory, profibrotic, and antiangiogenic effects provide potential mechanisms by which atrial conduction could be affected in patients treated with bisphosphonates. In studies in which an increase in risk of AF has been identified, there is no evidence that this translates into increased mortality or increased risk of stroke, and the risk-benefit balance of bisphosphonate therapy in patients with osteoporosis and other forms of metabolic bone disease remains strongly positive.

Bone tissue engineering therapeutics: controlled drug delivery in three-dimensional scaffolds

This paper provides an extensive overview of published studies on the development and applications of three-dimensional bone tissue engineering (TE) scaffolds with potential capability for the controlled delivery of therapeutic drugs. Typical drugs considered include gentamicin and other antibiotics generally used to combat osteomyelitis, as well as anti-inflammatory drugs and bisphosphonates, but delivery of growth factors is not covered in this review. In each case reviewed, special attention has been given to the technology used for controlling the release of the loaded drugs. The possibility of designing multifunctional three-dimensional bone TE scaffolds for the emerging field of bone TE therapeutics is discussed. A detailed summary of drugs included in three-dimensional scaffolds and the several approaches developed to combine bioceramics with various polymeric biomaterials in composites for drug-delivery systems is included. The main results presented in the literature are discussed and the remaining challenges in the field are summarized with suggestions for future research directions.

Use of high-dose oral bisphosphonate therapy for symptomatic fibrous dysplasia of the skull

Fibrous dysplasia of the bone in adults is a rare anomaly of skeletal development caused by a defect in differentiation of osteoblasts. This condition is associated with bone pain, bone deformity, and an increased incidence of fracture. Involvement of the skull is associated with headache along with dysmorphic features. Until recently, the principal treatment has been resection or fracture repair, although the latter is often palliative at best. However, new insight into the molecular mechanism of fibrous dysplasia has led to the use of bisphosphonates to treat this disease.

The authors examined the effects of high-dose oral alendronate (40 mg daily) for 6 months on 3 adult patients with intractable headache due to fibrous dysplasia of the skull. Each patient had disease processes not amenable to surgery. The patients underwent clinical follow-up at 1, 3, and 6 months. Their pain levels were documented at each visit by using a visual analog scale. All 3 patients demonstrated a significant decrease in pain levels and became independent of scheduled analgesics. Tumor bulk did not progress during this interval in any patient. Overall, alendronate was tolerated well, although in 1 patient it was discontinued early due to esophagitis. High-dose oral bisphosphonate therapy is an alternative therapeutic option for the palliative treatment of patients with fibrous dysplasia of the skull.

Risedronate reduces osteoclast precursors and cytokine production in postmenopausal osteoporotic women

This paper studies the effect of oral risedronate on osteoclast precursors, osteoclast formation, and cytokine production in 25 osteoporotic women. Risedronate is effective in reducing the number of osteoclast precursors, their formation, vitality, and activity and the level of RANKL and TNF-alpha in cultures.

INTRODUCTION

Bisphosphonates inhibit bone resorption by acting against osteoclasts. Some in vitro studies suggest that they induce osteoclast apoptosis; others suggest that they exert an effect on the production of pro-osteoclastogenic cytokines. The effect of risedronate on osteoclastogenesis by peripheral blood mononuclear cells (PBMCs) in postmenopausal osteoporosis has not been previously studied. This paper examined the influence of risedronate on the formation of osteoclast precursors and cytokine production within the compass of osteoclastogenesis in osteoporosis.

MATERIALS AND METHODS

This study was conducted on 38 osteoporotic women; 25 patients were treated with risedronate 5 mg/d, whereas 13 were treated with calcium 1 g/d and vitamin D 800 UI/d. The following parameters were assessed: changes in bone turnover, circulating osteoclast precursors, formation of osteoclasts in PBMC cultures, their activity and vitality, and variations in the production of pro-osteoclastogenic cytokines before and after therapy.

RESULTS

After 3 mo of risedronate, there was a significant reduction in the number and degree of differentiation of osteoclast precursors, osteoclast formation, vitality and activity, and in the level of RANKL and TNF in cultures and of TNF and osteoprotegerin (OPG) in serum, whereas in the group treated with calcium and vitamin D, there were no significant changes.

CONCLUSIONS

Our data show that risedronate is effective in lowering the number of circulating osteoclast precursors, their formation, vitality, and activity in cultures, and in reducing the level of pro-osteoclastogenic cytokines in culture supernatants and in serum.

Alendronate induces anti-migratory effects and inhibition of neutral phosphatases in UMR106 osteosarcoma cells

Bisphosphonates are nonhydrolysable pyrophosphate analogues that prevent bone loss in several types of cancer. However, the mechanisms of anticancer action of bisphosphonates are not completely known. We have previously shown that nitrogen-containing bisphosphonates directly inhibit alkaline phosphatase of UMR106 rat osteosarcoma cells. In this study, we evaluated the effects of alendronate on the migration of UMR106 osteosarcoma using a model of multicellular cell spheroids, as well as the alendronate effect on neutral phosphatases. Alendronate significantly inhibited the migration of osteoblasts in a dose-dependent manner (10(-6)-10(-4) M). This effect was also dependent on calcium availability. The spheroid morphology and distribution of actin fibers were also affected by alendronate treatment. Alendronate dose-dependently inhibited neutral phosphatase activity in cell-free osteoblastic extracts as well as in osteoblasts in culture. Our results show that alendronate inhibits cell migration through mechanisms dependent on calcium, and that seem to involve inhibition of phosphotyrosine-neutral-phosphatases and disassembly of actin stress fibers.

Current topics in pharmacological research on bone metabolism: inhibitory effects of bisphosphonates on the differentiation and activity of osteoclasts

Despite the extensive use of bisphosphonates (BPs) in the treatment of metabolic bone diseases associated with increased osteoclastic bone resorption, the precise mechanism of their action on bone metabolism is still unclear. To clarify at which stages of osteoclast differentiation and activation that BPs influence, we examined the osteoclasts generated from mononuclear precursors and osteoclasts in the calvaria by laser scanning confocal microscopy. The studies showed that BPs inhibit lipopolysaccharide- or parathyroid hormone-induced osteoclast differentiation, fusion, attachment, actin ring formation, and activation and that both beta3 integrin and osteopontin have an important role in cytoskeletal rearrangements associated with cell attachment and resorption in osteoclasts.

Ibandronate in metastatic bone disease: a review of preclinical data

Bisphosphonates are widely used to prevent and treat skeletal complications of metastatic bone disease. There is increasing evidence that, besides inhibiting osteoclast activity and reducing bone resorption, bisphosphonates also have an anti-tumor effect. This paper reviews the preclinical data for ibandronate. Ibandronate increased the proportion of apoptotic tumor cells in vitro and in vivo, possibly following activation of caspase-like proteases. In vitro, ibandronate also prevented adhesion and spreading of tumor cells to bone, and tumor cell invasion. These inhibitory effects were additive when ibandronate was given with paclitaxel or docetaxel. In animal models of tumor-induced osteolysis, ibandronate significantly reduced the development of osteolytic lesions. Efficacy for the prevention and reduction of bone metastases was related to the timing of treatment; ibandronate treatment initiated prior to or shortly after tumor cell inoculation inhibited the growth of bone metastases and preserved skeletal integrity most effectively. As with other bisphosphonates, the influence of ibandronate on soft tissue metastases has been inconsistent. Overall, preclinical evidence supports the rationale for adjuvant treatment with ibandronate for patients at risk of metastatic bone disease. The renal safety profile of ibandronate supports its suitability for long-term adjuvant use, even with intermittent high dosing. Adjuvant clinical trials have been initiated. The ability of bisphosphonates to preserve skeletal integrity is also of benefit in other clinical settings. Recent studies in rat models demonstrate improved osseointegration of joint implants following ibandronate therapy, with potential application in patients with conditions such as degenerative arthritis or osteoporosis.

Osteoclast responses to lipopolysaccharide, parathyroid hormone and bisphosphonates in neonatal murine calvaria analyzed by laser scanning confocal microscopy

Because the development and activity of osteoclasts in bone remodeling is critically dependent on cell-cell and cell-matrix interactions, we used laser confocal microscopy to study the response of osteoclasts to lipopolysaccharide (LPS; 10 microg/ml), parathyroid hormone (PTH; 10(-8) M), and bisphosphonates (BPs; 1-25 microM clodronate or 0.1-2.5 microM risedronate) in cultured neonatal calvaria. Following treatment with LPS or PTH (<48 hr), osteopontin (OPN) and the alphavbeta3 integrin were found colocalized with the actin ring in the sealing zone of actively resorbing osteoclasts. In contrast, non-resorbing osteoclasts in BP-treated cultures showed morphological abnormalities, including retraction of pseudopods and vacuolization of cytoplasm. In the combined presence of LPS and BP, bone-resorbing osteoclasts were smaller and the sealing zone diffuse, reflecting reduced actin, OPN, and beta3 integrin staining. Depth analyses of calvaria showed that the area of resorbed bone was filled with proliferating osteoblastic cells that stained for alkaline phosphatase, collagen type I, and bone sialoprotein, regardless of the presence of BPs. These studies show that confocal microscopy of neonatal calvaria in culture can be used to assess the cytological relationships between osteoclasts and osteoblastic cells in response to agents that regulate bone remodeling in situ, avoiding systemic effects that can compromise in vivo studies and artifacts associated with studies of isolated osteoclasts.

Zoledronic acid-related angiogenesis modifications and survival in advanced breast cancer patients

The proven antiangiogenic activity of zoledronic acid, a third-generation bisphosphonate widely used in bone metastatic cancer patients, led us to investigate if the vascular endothelial growth factor (VEGF)-related zoledronic acid modifications are correlated with survival advantages in advanced breast cancer patients. Forty-two consecutive breast cancer patients with scintigraphic and radiographic evidence of bone metastases were treated with a single infusion of 4 mg zoledronic acid before anticancer chemotherapy. The patients were prospectively evaluated for circulating levels of VEGF and interferon-gamma (IFN-gamma) just before and at 1, 2, 7, and 21 days after zoledronic acid infusion. Afterward, clinical outcome was prospectively monitored. The basal serum VEGF median levels were significantly decreased at each time point, but the major reduction was recorded 21 days after the infusion. In particular, 25 patients of 42 (59.5%) experienced a reduction of at least 25% in the VEGF circulating levels. In contrast, no statistically significant modifications of the IFN-gamma serum levels were recorded. We stratified patients on the basis of this VEGF reduction 21 days after the infusion. No differences in patient features were recorded between those with or without the VEGF reduction. The analysis of survival showed that patients with a reduction in the VEGF circulating levels had a longer time to first skeletal-related event (p = 0.0002), time to bone progression disease (p = 0.0024), and time to performance status worsening (p = 0.0352) than those without the VEGF reduction. No statistically significant differences were recorded in terms of overall survival and time to visceral progression. This study confirms that zoledronic acid could have an in vivo antiangiogenic property and that the VEGF modifications may represent a surrogate marker able to predict time to first skeletal-related event, time to bone progression disease, and time to worsening of performance status.

Alendronate inhibits bone resorption at the bone-screw interface

In the current study, we investigated whether the systemic administration of alendronate, a third-generation bisphosphonate, suppressed the loosening of screws at the bone-screw interface. We systemically administered alendronate to rats fitted with external fixators. External fixators with two half pins were applied to the right femurs of rats, and alendronate was administrated once a week during a 5-week postoperative period. Radiographic, histologic, and immunohistochemical findings subsequently were analyzed. Treatment with alendronate reduced the width of the fibrous loosening membrane and the number of osteoclasts at the bone-screw interface. These findings indicate that systemic treatment with alendronate exerts an inhibitory effect on local bone resorption at the bone-screw interface.

Effects of vitamin K2 (menatetrenone) and alendronate on bone mineral density and bone strength in rats fed a low-magnesium diet

In this study, we examined changes in bone parameters and bone strength in rats fed low-Mg diets (experiment 1) and the effects of vitamin K2 (MK-4, experiment 3) and alendronate (ALN, experiment 2) in this model. In experiment 1, 5-week-old male Wistar rats were fed three low-Mg diets (Mg 9, 6, 3 mg/100 g diet) for 4 weeks. Although the cortical bone mineral content (CtBMC) and cortical thickness (CtTh) of the femoral diaphysis in all low-Mg-diet groups were the same as or greater than those in the intact group (Mg: 90 mg/100 g diet), the maximum load and elastic modulus were significantly reduced in the 3-mg-Mg group. In experiment 2, 4-week-old Wistar rats were fed a 6-mg-Mg diet for 8 weeks, and the effect of ALN (2, 20, and 200 microg/kg twice a week) was evaluated. The administration of ALN at 200 microg/kg increased the cortical bone mineral content (CtBMC), CtTh, and maximum load, but had no effect on the elastic modulus, as compared with the low-Mg-control group. In experiment 3, the effect of MK-4 was evaluated under the same conditions as in experiment 2. The administration of MK-4 had no effect on CtBMC, CtTh, or bone components of the femoral diaphysis. However, MK-4 inhibited the decreases in maximum load and elastic modulus due to the low-Mg diet. Since there is no other experimental model in which there is a decrease in bone mechanical properties without a decrease in bone mineral content, the low-Mg diet model is considered to be an excellent model for examining bone quality. Our results from this model suggest that MK-4 and ALN affect bone mechanical properties by different mechanisms.

Bisphosphonate Effects in Cancer and Inflammatory Diseases

Bisphosphonates are endogenous pyrophosphate analogs in which a carbon atom replaces the central atom of oxygen. They are indicated in non-neoplastic diseases including osteoporosis, corticosteroid-induced bone loss, Paget disease, and in cancer-related diseases such as neoplastic hypercalcemia, multiple myeloma and bone metastases secondary to breast and prostate cancer. There is now extensive in vitro evidence suggesting a direct antitumor effect of bisphosphonates at different levels of action. Some new in vitro and in vivo studies support the cytostatic effects of bisphosphonates on tumor cells, and the effects on the regulation of cell growth, apoptosis, angiogenesis, cell adhesion, and invasion, with particular attention to biological properties. Well designed clinical trials are necessary to investigate whether the antitumor potential of bisphosphonates may be clinically relevant. On the basis of their effects on macrophages, we may divide bisphosphonates into two distinct categories: aminobisphosphonates, which sensitize macrophages to an inflammatory stimulus inducing an acute-phase response, and non-aminobisphosphonates that can be metabolized into macrophages and that may inhibit the inflammatory response of macrophages. There is evidence of aminobisphosphonate-induced pro-inflammatory response, in particular, related to modifications of the cytokine network. Several in vivo studies have demonstrated an acute-phase reaction after the first administration of aminobisphosphonates, with a significant increase in the main pro-inflammatory cytokines. However, a peculiar aspect concerning the action of non-aminobisphosphonates seems to be an anti-inflammatory activity caused by the inhibition of the release of inflammatory mediators from activated macrophages, such as interleukin (IL)-6, tumor necrosis factor-alpha and IL-1. The inhibition of inflammatory responses is demonstrated in both in vivo and in vitro models. This activity suggests the use of non-aminobisphosphonates in several inflammatory diseases characterized by macrophage-mediated production of acute-phase cytokines, as prevention of erosions in rheumatoid arthritis, and of loosening of joint prostheses, as well as possibly in osteoarthritis, ankylosing spondylitis, myelofibrosis, and hypertrophic pulmonary osteoarthropathy.

The nitrogen-containing bisphosphonate, zoledronic acid, influences RANKL expression in human osteoblast-like cells by activating TNF-alpha converting enzyme (TACE)

Bisphosphonates are used to prevent osteoclast-mediated bone loss. Zoledronic acid inhibits osteoclast maturation indirectly by increasing OPG protein secretion and decreasing transmembrane RANKL expression in human osteoblasts. The decreased transmembrane RANKL expression seems to be related to the upregulation of the RANKL sheddase, TACE.

INTRODUCTION

Bisphosphonates (BPs) exhibit high affinity for hydroxyapatite mineral in bone and are used extensively to treat malignancy-associated bone disease and postmenopausal bone loss by inhibiting osteoclast (OC)-mediated bone resorption.

MATERIALS AND METHODS

We examined the effect of the most potent nitrogen-containing BP available, zoledronic acid (ZOL), on the expression of RANKL and osteoprotegerin (OPG), critical factors in the regulation of OC formation and activation, in primary osteoblast (OB)-like cells derived from human bone, using flow cytometry, ELISA, semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR), in situ immunofluorescence staining, and Western blotting.

RESULTS

Our studies show that ZOL, while not significantly affecting RANKL or OPG gene expression, markedly increased OPG protein secretion and reduced transmembrane RANKL protein expression in OB-like cells. The reduction in transmembrane RANKL expression was preceded by a marked increase in the expression of the metalloprotease-disintegrin, TNF-alpha converting enzyme (TACE). In addition, the decreased transmembrane expression of RANKL could be partially reversed by a TACE inhibitor, TAPI-2.

CONCLUSIONS

Our studies indicate that ZOL, in addition to its direct effects on mature OCs, may inhibit the recruitment and differentiation of OCs by cleavage of transmembrane RANKL in OB-like cells by upregulating the sheddase, TACE.

The antineoplastic role of bisphosphonates: from basic research to clinical evidence

Bisphosphonates are now well established as successful agents for the prevention and treatment of postmenopausal osteoporosis, corticosteroid-induced bone loss and Paget's disease. Bisphosphonates have also recently become important in the management of cancer-induced bone disease, and they now have a widely recognized role for patients with multiple myeloma and bone metastases secondary to breast cancer and prostate cancer. Recent studies suggest that, besides the strong antiosteoclastic activity, the efficacy of such compounds in the oncological setting could also be due also to direct antitumor effect, exerted at different levels. Here, after a brief analysis of the chemical structure, we will review the antineoplastic and biological properties of bisphosphonates. We will start from well estabilished mechanisms of action and go on to discuss the latest evidence and hypotheses. In particular, we will review the antiresorptive properties in malignant osteolysis and the recent evidence of a direct antitumor effect. Furthermore, this review will analyze the influence of bisphosphonates on cancer growth factor release, their effect on cancer cell adhesion, invasion and viability, the proapoptotic potential on cancer cells, the antiangiogenic effect, and, finally, the immunomodulating properties of bisphosphonates on the gammadelta T cell population.

Antitumor effects of bisphosphonates

BACKGROUND

Bisphosphonates are widely used to treat skeletal complications of malignancy. These drugs accumulate in bone where they inhibit osteoclastic bone resorption and reduce the local release of factors that stimulate tumor growth. The mechanism of action of bisphosphonates is dependent on chemical structure: Nonnitrogen-containing compounds (e.g., etidronate, clodronate) are metabolized into cytotoxic analogues of ATP, whereas the more potent nitrogen-containing compounds (N-BPs; e.g., pamidronate, ibandronate, zoledronic acid) inhibit protein prenylation, thus affecting cell function and survival. Because protein prenylation is required by all cells, not just osteoclasts, the possibility arises that N-BPs could also affect the viability of tumor cells.

METHODS

Several groups have investigated the in vitro effects of bisphosphonates, either alone or in combination with other antineoplastic agents, on the viability and metastatic properties of many tumor cell types. Similarly, the effect of bisphosphonate treatment on osteolysis and tumor burden has been studied in a variety of animal tumor models.

RESULTS

In vitro, submicromolar concentrations of N-BPs inhibited tumor cell adhesion and reduced invasion through extracellular matrix. At higher concentrations, antiproliferative and proapoptotic effects have been reported. In animal models of bone metastases, bisphosphonate treatment markedly reduced osteolytic lesions. There is also evidence of a reduction in tumor burden in bone and occasionally in other organs. Survival may be prolonged, but bisphosphonates do not appear to inhibit the growth of primary soft tissue tumors or orthotopic xenografts.

CONCLUSIONS

The cell culture data clearly demonstrated that N-BPs exert antitumor properties and interact synergistically with other antineoplastic agents. As bisphosphonates accumulate in bone, they can also exert cytostatic effects on tumor cells in bone metastases, either directly or indirectly via osteoclast inhibition and alterations in the bone microenvironment. Further in vivo research is now required to optimize the dosing regimen of N-BPs to exploit fully their antitumor potential.

Effect of pamidronate on the stimulation of macrophage TNF-alpha release by ultra-high-molecular-weight polyethylene particles: a role for apoptosis

The demonstration that one of the mechanisms of action of bisphosphonates (BPs) is the induction of osteoclast and macrophage apoptosis, suggests a potent therapeutic role for the BPs and other apoptosis-modulating agents in the management of periprosthetic osteolysis. The purpose of this study was to improve our understanding of the basic underlying molecular events leading to the inhibitory effect of pamidronate on the macrophage response to ultra-high-molecular-weight polyethylene (UHMWPE) particles. Murine J774 macrophages were incubated for 0-72 h in the presence of UHMWPE particles and/or pamidronate. TNF-alpha release was measured by ELISA while poly(ADP-ribose)polymerase (PARP) expression was measured by Western blot. DNA was analyzed on agarose. The appearance of PARP fragment and the fragmentation of DNA were used as markers of apoptosis. We observed a dose-dependent response to UHMWPE particles with TNF-alpha release reaching 4, 10, and 19 times control with 10, 25, and 125 particles/macrophage, respectively. UHMWPE particles (25 particles/macrophage) stimulate TNF-alpha release by a factor of 10, 7, and 6 after 24, 48, and 72 h, respectively, indicating a rapid stimulating effect of UHMWPE particles on TNF-alpha release. Our results also showed that at 10 particles/macrophage, pamidronate inhibits UHMWPE-induced TNF-alpha release by 12%, 14%, and 23% respectively after 24, 48, and 72 h (p<0.05 vs. 24 and 48 h). With 25 particles/macrophage, the inhibition of TNF-alpha reached 9%, 12%, and 15% after 24, 48, and 72 h (p<0.05 vs. 24 h), respectively. There is no significant difference between the inhibition by pamidronate of TNF-alpha release induced by 125 particles/macrophages at 24, 48, and 72 h. When cells are pre-incubated for 48 h with pamidronate prior to addition of UHMWPE particles for 24 h, we observed an increased inhibition of TNF-alpha compared to the co-incubation protocol. The inhibiting effect of pamidronate reaches 56% when pre-incubated with macrophages prior to incubation with 10 particles of UHMWPE/macrophage (p<0.05 vs. co-incubation).Co-incubation of pamidronate with UHMWPE particles also led to the appearance of the proteolytic PARP fragment after 24 h incubation. We also demonstrated the stimulation of DNA fragmentation (DNA laddering) after 48-72 h with pamidronate. The proteolytic cleavage of PARP, an early event in the induction of apoptosis, precedes the inhibition of UHMWPE particle-induced TNF-alpha release by pamidronate whereas the fragmentation of DNA, a late apoptotic event, parallels this inhibition. Our results suggest the induction of macrophage apoptosis is associated with the inhibitory effect of pamidronate on TNF-alpha release. There is a need for the development of medical management of periprosthetic osteolysis. The demonstration that drugs such as pamidronate induce specific apoptosis-related pathways in macrophages contributes data for a rational approach in the treatment and/or prevention of periprosthetic osteolysis.