Alendronate reduces osteoclast precursors in osteoporosis

FABP4 inhibition suppresses bone resorption and protects against postmenopausal osteoporosis in ovariectomized mice

Postmenopausal osteoporosis (PMOP) is a condition in women caused by estrogen deficiency, characterized by reduced bone mass and increased fracture risk. Fatty acid-binding protein 4 (FABP4), a lipid-binding protein involved in metabolism and inflammation, has emerged as a key regulator in metabolic disorders and bone resorption; however, its direct role in PMOP remains unclear. Here, we show that serum FABP4 levels in PMOP patients negatively correlate with bone mineral density, a trend also observed in ovariectomized mice. FABP4 promotes osteoclast formation and bone resorption without affecting osteoblast differentiation. The FABP4 inhibitor BMS309403 suppresses osteoclast differentiation by modulating calcium signaling and inhibiting the Ca2+-Calcineurin-NFATc1 pathway. Oral BMS309403 increases bone mineral density in ovariectomized mice, though less effectively than alendronate. Notably, bone-targeted delivery of BMS309403 achieves comparable efficacy to alendronate. In this work, we demonstrate that FABP4 is a critical mediator in PMOP and that its inhibition offers a promising therapeutic strategy.

Preventing osteoporotic bone loss in mice by promoting balanced bone remodeling through M-CSFRGD, a dual antagonist to c-FMS and αvβ3 receptors

Osteoporosis is a common, age-related disease caused by imbalanced bone remodeling. Current treatments either shut down bone resorption or robustly stimulate bone formation. Here, we describe a novel compound that inhibits osteoclast activity without causing apparent disruptions to bone formation by targeting both c-FMS (i.e., osteoclast differentiation) and αvβ3 integrin (i.e., osteoclastic bone resorption) receptors. We show that human serum albumin (HSA)-conjugated M-CSFRGD protein (M-CSFRGD-HSA) effectively inhibits the activity of both receptors, with a three-fold higher serum half-life compared to the unconjugated M-CSFRGD. We then treated ovariectomized mice with different doses of M-CSFRGD-HSA, alendronate, or a monospecific control protein. The bispecific M-CSFRGD-HSA was superior to a monospecific control in alleviating bone loss and reducing osteoclast distribution and function. M-CSFRGD-HSA and alendronate effectively prevented ovariectomy-induced bone loss, but M-CSFRGD-HSA had a milder inhibitory effect on osteoclast distribution and activity. Moreover, alendronate halted bone formation, while M-CSFRGD-HSA-treated mice showed an increased level of serum amino-terminal propeptide of type I collagen, a bone formation marker. Our data indicate that the mild reduction in osteoclast activity facilitated by the bispecific M-CSFRGD-HSA allows the maintenance of certain levels of bone formation and may be superior to treatments that induce osteoclast depletion.

Osteoimmunology: The Crosstalk between T Cells, B Cells, and Osteoclasts in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an ongoing inflammatory condition that affects the joints and can lead to severe damage to cartilage and bones, resulting in significant disability. This condition occurs when the immune system becomes overactive, causing osteoclasts, cells responsible for breaking down bone, to become more active than necessary, leading to bone breakdown. RA disrupts the equilibrium between osteoclasts and osteoblasts, resulting in serious complications such as localized bone erosion, weakened bones surrounding the joints, and even widespread osteoporosis. Antibodies against the receptor activator of nuclear factor-κB ligand (RANKL), a crucial stimulator of osteoclast differentiation, have shown great effectiveness both in laboratory settings and actual patient cases. Researchers are increasingly focusing on osteoclasts as significant contributors to bone erosion in RA. Given that RA involves an overactive immune system, T cells and B cells play a pivotal role by intensifying the immune response. The imbalance between Th17 cells and Treg cells, premature aging of T cells, and excessive production of antibodies by B cells not only exacerbate inflammation but also accelerate bone destruction. Understanding the connection between the immune system and osteoclasts is crucial for comprehending the impact of RA on bone health. By delving into the immune mechanisms that lead to joint damage, exploring the interactions between the immune system and osteoclasts, and investigating new biomarkers for RA, we can significantly improve early diagnosis, treatment, and prognosis of this condition.

Therapeutic effects of isoquercetin on ovariectomy-induced osteoporosis in mice

Bone marrow mesenchymal stem cells (BMSCs) are non-hematopoietic multipotent stem cells capable of differentiating into mature cells. Isoquercetin, an extract from natural sources, has shown promise as a potential treatment for osteoporosis. To investigate the therapeutic effects of isoquercetin on osteoporosis, bone marrow mesenchymal stem cells (BMSCs) were cultured in vitro, and osteogenesis or adipogenesis was induced in the presence of isoquercetin for 14 days. We evaluated cell viability, osteogenic and adipogenic differentiation, as well as mRNA expression levels of Runx2, Alpl, and OCN in osteoblasts, and mRNA expression levels of Pparγ, Fabp4, and Cebpα in adipocytes. The results showed that isoquercetin dose-dependently increased cell viability and promoted osteogenic differentiation, as evidenced by Alizarin Red and alkaline phosphatase staining and mRNA expression levels of Runx2, Alpl, and OCN in osteoblasts (P < 0.05). In contrast, isoquercetin inhibited adipogenic differentiation and decreased the mRNA expression levels of Pparγ, Fabp4, and Cebpα in adipocytes (P < 0.05). In vivo, isoquercetin treatment increased bone quantity and density in an osteoporosis model mice group, as determined by μCT scanning and immunohistochemistry (P < 0.05). These findings suggest that isoquercetin may have therapeutic potential for osteoporosis by promoting the proliferation and differentiation of BMSCs towards osteoblasts while inhibiting adipogenic differentiation.

Reduction of Osteoclastic Differentiation of Raw 264.7 Cells by EMF Exposure through TRPV4 and p-CREB Pathway

In this study, we investigated the effect of EMF exposure on the regulation of RANKL-induced osteoclast differentiation in Raw 264.7 cells. In the EMF-exposed group, the cell volume did not increase despite RANKL treatment, and the expression levels of Caspase-3 remained much lower than those in the RANKL-treated group. TRAP and F-actin staining revealed smaller actin rings in cells exposed to EMF during RANKL-induced differentiation, indicating that EMF inhibited osteoclast differentiation. EMF-irradiated cells exhibited reduced mRNA levels of osteoclastic differentiation markers cathepsin K (CTSK), tartrate-resistant acid phosphatase (TRAP), and matrix metalloproteinase 9 (MMP-9). Furthermore, as measured by RT-qPCR and Western blot, EMF induced no changes in the levels of p-ERK and p-38; however, it reduced the levels of TRPV4 and p-CREB. Overall, our findings indicate that EMF irradiation inhibits osteoclast differentiation through the TRPV4 and p-CREB pathway.

Clinical Data for Parametrization of In Silico Bone Models Incorporating Cell-Cytokine Dynamics: A Systematic Review of Literature

In silico simulations aim to provide fast, inexpensive, and ethical alternatives to years of costly experimentation on animals and humans for studying bone remodeling, its deregulation during osteoporosis and the effect of therapeutics. Within the varied spectrum of in silico modeling techniques, bone cell population dynamics and agent-based multiphysics simulations have recently emerged as useful tools to simulate the effect of specific signaling pathways. In these models, parameters for cell and cytokine behavior are set based on experimental values found in literature; however, their use is currently limited by the lack of clinical in vivo data on cell numbers and their behavior as well as cytokine concentrations, diffusion, decay and reaction rates. Further, the settings used for these parameters vary across research groups, prohibiting effective cross-comparisons. This review summarizes and evaluates the clinical trial literature that can serve as input or validation for in silico models of bone remodeling incorporating cells and cytokine dynamics in post-menopausal women in treatment, and control scenarios. The GRADE system was used to determine the level of confidence in the reported data, and areas lacking in reported measures such as binding site occupancy, reaction rates and cell proliferation, differentiation and apoptosis rates were highlighted as targets for further research. We propose a consensus for the range of values that can be used for the cell and cytokine settings related to the RANKL-RANK-OPG, TGF-β and sclerostin pathways and a Levels of Evidence-based method to estimate parameters missing from clinical trial literature.

Effect of Denosumab on the Change of Osteoclast Precursors Compared to Zoledronate Treatment in Postmenopausal Women with Osteoporosis

Background

A rapid increase in bone turnover and bone loss has been observed in response to the discontinuation of denosumab. It led to an acute increase in the fracture risk, similar to that observed in the untreated patients. We aimed to investigate the effect of denosumab on osteoclast (OC) precursor cells compared to that of zoledronate.

Methods

The study compared the effects of denosumab (60 mg/24-week) and zoledronate (5 mg/48-week) over 48 weeks in postmenopausal women with osteoporosis. From patients’ peripheral mononuclear cells, CD14⁺/CD11b⁺/vitronectin receptor (VNR)- and CD14⁺/CD11b⁺/VNR⁺ cells were isolated using fluorescent-activated cell sorting, representing early and late OC precursors, respectively. The primary endpoint was the changes in OC precursors after 48 weeks of treatment.

Results

Among the 23 patients, 11 were assigned to the denosumab group and 12 to the zoledronate group (mean age, 69 years). After 48 weeks, the changes in OC precursors were similar between and within the groups. Serum C-terminal telopeptide of type I collagen levels were inversely correlated with OC precursor levels after denosumab treatment (r=−0.72, P<0.001). Lumbar spine, femur neck, and total hip bone mineral density (BMD) increased in both groups. Lumbar spine BMD increased more significantly in the denosumab group than in the zoledronate group.

Conclusions

Denosumab and zoledronate treatments induced similar changes in OC precursors. During denosumab treatment, old age and suppressed bone turnover were associated with increased OC precursor cell populations. Further validation studies with prospective designs are required.

99Tc-Methylene Diphosphonate Treatment is Safe and Efficacious for Osteoporosis in Postmenopausal Differentiated Thyroid Cancer Patients Undergoing TSH Suppression: A Three-Center Non-Randomized Clinical Study

Objective

To investigate the effects of ⁹⁹Tc-methylene diphosphonate (⁹⁹Tc-MDP) on osteoporosis (OS) in postmenopausal patients with differentiated thyroid cancer (DTC) under thyroid stimulating hormone (TSH) suppression.

Patients and Methods

Patients (n = 142) were divided into two groups: (1) ⁹⁹Tc-MDP (n = 70) and (2) alendronate (n = 72) treatments (NCT 02304757). Bone mineral density (BMD) in the lumbar spine and hip was evaluated by DXA, along with bone turnover markers, safety, and quality of life (QOL) using SF-36 at three time points: before treatment and at 6 and/or 12 months after treatment.

Results

The percentage change of BMD in total lumbar spine or hip showed no significant difference throughout the study (P > 0.025). ⁹⁹Tc-MDP and alendronate treatment alone significantly increased BMD in the lumbar spine, but alendronate treatment also significantly increased BMD in total hip at 6 and 12 months, as compared with the baseline. There were no significant differences in the results of the SF-36 scores between the two treatment groups at any time during the whole study period. ⁹⁹Tc-MDP significantly increased bone formation markers of osteocalcin at 6 and 12 months (P all < 0.05), PINP at 12 months (P = 0.001), and bone resorption markers of β-CTX at 6 and 12 months (p < 0.05) as compared with the alendronate treated group. No adverse event was observed in the ⁹⁹Tc-MDP treatment group compared with alendronate (P = 0.014).

Conclusion

⁹⁹Tc-MDP was as efficacious as alendronate in the improvement of lumbar BMD for DTC patients with OS under TSH stimulation. ⁹⁹Tc-MDP was shown to be safe and improved patients’ QOL.

Regulation of bone mass in inflammatory diseases

Inflammation is among the major determinants of bone loss in chronic disease and aging. Bone metabolism is radically affected by inflammation with consequent bone loss and increased fracture risk. Various cytokines and mediators are involved in the pathogenesis of bone loss in inflammatory conditions. The present review has the aim of discussing the main pathways involved in the pathogenesis of bone loss in inflammatory diseases, focusing in particular on the Wnt system and its regulators. Literature review of studies published between inception to 2021 on osteoporosis and inflammation was conducted. I will discuss the epidemiology of osteoporosis and fractures in common inflammatory diseases. The molecular basis of bone loss related to inflammation will be discussed as well. Finally, the effects of various anti-inflammatory medications on bone metabolism will be reviewed.

The Use of Oral Amino-Bisphosphonates and Coronavirus Disease 2019 (COVID-19) Outcomes

The determinants of the susceptibility to severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection and severe coronavirus disease 2019 (COVID-19) manifestations are yet not fully understood. Amino-bisphosphonates (N-BPs) have anti-inflammatory properties and have been shown to reduce the incidence of lower respiratory infections, cardiovascular events, and cancer. We conducted a population-based retrospective observational cohort study with the primary objective of determining if oral N-BPs treatment can play a role in the susceptibility to development of severe COVID-19. Administrative International Classification of Diseases, Ninth Revision, Clinical ModificationI (ICD-9-CM) and anatomical-therapeutic chemical (ATC) code data, representative of Italian population (9% sample of the overall population), were analyzed. Oral N-BPs (mainly alendronate and risedronate) were included in the analysis, zoledronic acid was excluded because of the low number of patients at risk. Incidence of COVID-19 hospitalization was 12.32 (95% confidence interval [CI], 9.61-15.04) and 11.55 (95% CI, 8.91-14.20), of intensive care unit (ICU) utilization because of COVID-19 was 1.25 (95% CI, 0.38-2.11) and 1.42 (95% CI, 0.49-2.36), and of all-cause death was 4.06 (95% CI, 2.50-5.61) and 3.96 (95% CI, 2.41-5.51) for oral N-BPs users and nonusers, respectively. Sensitivity analyses that excluded patients with prevalent vertebral or hip fragility fractures and without concomitant glucocorticoid treatment yielded similar results. In conclusion, we found that the incidence of COVID-19 hospitalization, intensive care unit (ICU) utilization, and COVID-19 potentially related mortality were similar in N-BPs-treated and nontreated subjects. Similar results were found in N-BPs versus other anti-osteoporotic drugs. We provide real-life data on the safety of oral N-BPs in terms of severe COVID-19 risk on a population-based cohort. Our results do not support the hypothesis that oral N-BPs can prevent COVID-19 infection and/or severe COVID-19; however, they do not seem to increase the risk. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Impact of Cigarette Smoking on the Risk of Osteoporosis in Inflammatory Bowel Diseases

Cigarette smoking constitutes one of the most important modifiable factors of osteoporosis, as well as contributes to an early death, tumors, and numerous chronic diseases. The group with an increased risk of a lower bone mineral density are patients suffering from inflammatory bowel diseases. In fact, tobacco smoke, which contains more than 7000 chemical compounds, affects bone mineral density (BMD) both directly and indirectly, as it has an impact on the RANK-RANKL-OPG pathway, intestinal microbiota composition, and calcium-phosphate balance. Constant cigarette use interferes with the production of protective mucus and inhibits the repair processes in the intestinal mucus. Nicotine as well as the other compounds of the cigarette smoke are important risk factors of the inflammatory bowel disease and osteoporosis. Additionally, cigarette smoking may decrease BMD in the IBD patients. Interestingly, it affects patients with Crohn's disease and ulcerative colitis in different ways-on the one hand it protects against ulcerative colitis, whereas on the other it increases the risk of Crohn's disease development. Nevertheless, all patients should be encouraged to cease smoking in order to decrease the risk of developing other disorders.

Randomized, controlled trial to assess the safety and efficacy of odanacatib in the treatment of men with osteoporosis

Odanacatib (ODN) was investigated as an osteoporosis treatment in 292 men. Compared with placebo, odanacatib improved bone mineral density and led to sustained bone resorption decreases while producing relatively little bone formation reduction that leveled off with time. However, increased risk of stroke in another study stopped further odanacatib development.

INTRODUCTION

ODN, a selective oral cathepsin K inhibitor, was in development for osteoporosis treatment. This phase 3, double-blind, randomized, placebo-controlled, 24-month study investigated ODN safety and efficacy in men with osteoporosis.

METHODS

Men with idiopathic osteoporosis or osteoporosis due to hypogonadism and a lumbar spine or hip (total hip [TH], femoral neck [FN], or trochanter) bone mineral density (BMD) T-score of ≤ - 2.5 to ≥ - 4.0 without prior vertebral fracture or ≤ - 1.5 to ≥ - 4.0 with one prior vertebral fracture were randomized (1:1) to once-weekly ODN 50 mg or placebo. All received 5600 IU vitamin D₃ weekly and calcium supplementation as needed (≥ 1200 mg daily). The primary efficacy outcome was changed from baseline in lumbar spine BMD versus placebo.

RESULTS

Overall, 292 men, mean age 68.8 years, were randomly assigned to ODN or placebo. Versus placebo, ODN increased BMD from baseline at the lumbar spine, TH, FN, and trochanter by 5.6%, 2.0%, 1.7%, and 2.1%, respectively (all p < 0.01), and decreased uNTx/Cr (68%, p < 0.001), sCTx (77%, p < 0.001), sP1NP (16%, p = 0.001), and sBSAP (8%, p = 0.019). The between-group bone formation marker decrease peaked at 3 months, then returned toward baseline. The safety profile, including cardiovascular events, was similar between groups.

CONCLUSION

Though a promising osteoporosis therapy for men, ODN development was discontinued due to increased risk of stroke in the LOFT phase 3 trial.

TRIAL REGISTRATION

Clinicaltrials.gov NCT01120600 (registered May 11, 2010).

Bisphosphonates Reduce Smoking-Induced Osteoporotic-Like Alterations by Regulating RANKL/OPG in an Osteoblast and Osteoclast Co-Culture Model

Co-culture models have become mandatory for obtaining better insights into bone homeostasis, which relies on the balance between osteoblasts and osteoclasts. Cigarette smoking (CS) has been proven to increase the risk of osteoporosis; however, there is currently no proven treatment for osteoporosis in smokers excluding cessation. Bisphosphonates (BPs) are classical anti-osteoclastic drugs that are commonly used in examining the suitability of bone co-culture systems in vitro as well as to verify the response to osteoporotic stimuli. In the present study, we tested the effects of BPs on cigarette smoke extract (CSE)-affected cells in the co-culture of osteoblasts and osteoclasts. Our results showed that BPs were able to reduce CSE-induced osteoporotic alterations in the co-culture of osteoblasts and osteoclasts such as decreased matrix remodeling, enhanced osteoclast activation, and an up-regulated receptor activator of nuclear factor (NF)-kB-ligand (RANKL)/osteoprotegerin (OPG) ratio. In summary, BPs may be an effective alternative therapy for reversing osteoporotic alterations in smokers, and the potential mechanism is through modulation of the RANKL/OPG ratio.

Nitrogen-Containing Bisphosphonates Are Associated With Reduced Risk of Pneumonia in Patients With Hip Fracture

The objective of this work was to study the risk of pneumonia and pneumonia mortality among patients receiving nitrogen-containing bisphosphonates (N-BPs), non-N-BP anti-osteoporosis medications, and no anti-osteoporosis medications after hip fracture. We studied a historical cohort using a population-wide database. Patients with first hip fracture during 2005-2015 were identified and matched by time-dependent propensity score. The cohort was followed until December 31, 2016, to capture any pneumonia and pneumonia mortality. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox-proportional hazards regression. Absolute risk difference (ARD) and number needed to treat (NNT) were calculated. We identified 54,047 patients with hip fracture. Of these, 4041 patients who received N-BPs and 11,802 without anti-osteoporosis medication were propensity score-matched. N-BPs were associated with a significantly lower risk of pneumonia compared with no treatment (6.9 versus 9.0 per 100 person-years; HR 0.76; 95% CI, 0.70 to 0.83), resulting in an ARD of 0.02 and NNT of 46. A similar association was observed with pneumonia mortality (HR 0.65; 95% CI, 0.56 to 0.75). When N-BPs were compared with non-N-BP anti-osteoporosis medications, the association remained significant. N-BPs were associated with lower risks of pneumonia and pneumonia mortality. Randomized controlled trials are now required to determine whether N-BPs, non-vaccine-based medications, can reduce pneumonia incidence in high risk groups. © 2020 American Society for Bone and Mineral Research.

Sodium alendronate loaded poly(l-lactide- co-glycolide) microparticles immobilized on ceramic scaffolds for local treatment of bone defects

Bone tissue regeneration in critical-size defects is possible after implantation of a 3D scaffold and can be additionally enhanced once the scaffold is enriched with drugs or other factors supporting bone remodelling and healing. Sodium alendronate (Aln), a widely used anti-osteoporosis drug, exhibits strong inhibitory effect on bone resorption performed by osteoclasts. Thus, we propose a new approach for the treatment of bone defects in craniofacial region combining biocompatible titanium dioxide scaffolds and poly(l-lactide-co-glycolide) microparticles (MPs) loaded with Aln. The MPs were effectively attached to the surface of the scaffolds’ pore walls by human recombinant collagen. Drug release from the scaffolds was characterized by initial burst (24 ± 6% of the drug released within first 24 h) followed by a sustained release phase (on average 5 µg of Aln released per day from Day 3 to Day 18). In vitro tests evidenced that Aln at concentrations of 5 and 2.5 µg/ml was not cytotoxic for MG-63 osteoblast-like cells (viability between 81 ± 6% and 98 ± 3% of control), but it prevented RANKL-induced formation of osteoclast-like cells from macrophages derived from peripheral blood mononuclear cells, as shown by reduced fusion capability and decreased tartrate-resistant acid phosphatase 5b activity (56 ± 5% reduction in comparison to control after 8 days of culture). Results show that it is feasible to design the scaffolds providing required doses of Aln inhibiting osteoclastogenesis, reducing osteoclast activity, but not affecting osteoblast functions, which may be beneficial in the treatment of critical-size bone tissue defects.

Efficacy of vitamin D plus calcium with/without alendronate on bone metabolism in immunologic thrombocytopenic purpura patients with steroid treatment: Nine-month results of a randomized, double-blinded, controlled trial

Bone loss is a prominent complication in immunologic thrombocytopenic purpura (ITP) patients with steroid treatment. Anti-osteoporotic medications are applied as a therapeutic strategy to prevent bone deterioration in ITP patients. However, the skeletal protective effect of alendronate (ALN) in ITP patients has been rarely reported. The present study was performed to determine whether ALN reduces bone loss in ITP patients. A total of 40 ITP patients with steroid treatment were randomized into a placebo group [n=20; caltrate D (CalD)] and an ALN (10 mg/day) + CalD group (n=20). The patients received CalD or CalD + ALN treatment for 9 months. The primary outcomes were bone mineral density (BMD) in the lumbar vertebrae (L1-L4), femoral neck and total hip, as well as bone metabolism markers. The results indicated that the BMD of the lumbar vertebrae (L1-L4), femoral neck and total hip was significantly increased after ALN + CalD treatment for at 6 and 9 months compared with the baseline. Compared with CalD treatment alone, CalD combined with ALN significantly elevated the BMD at the three skeletal sites at 9 months. Compared with the baseline levels or CalD treatment alone, ALN together with CalD treatment markedly reduced urinary Ca excretion and the serum levels of the bone resorption markers tartrate resistant acid phosphatase 5b and C-terminal telopeptides of type 1 collagen, at 9 months. In conclusion, treatment with ALN together with CalD significantly elevated the BMD at three skeletal sites, and inhibited urinary Ca excretion and the activity of bone resorption markers in patients with ITP.

Alendronate-Modified Polymeric Micelles for the Treatment of Breast Cancer Bone Metastasis

Although the prognosis of patients with breast cancer continues to improve, breast cancer metastasis to bones remains high in incidence and challenging to manage. Here, we report the development of bone-homing alendronate (ALN)-anchored biodegradable polymeric micelles for the targeted treatment of metastatic cancer to bone. These micelles exhibited bone protective capacity including the recruitment, differentiation, and resorption activity of the osteoclasts. Encapsulation of docetaxel (DTX), the first-line chemotherapeutic for treatment of metastatic breast cancer, in ALN-modified micelles results in a sustained release, enhanced cytotoxicity, and improved pharmacokinetics. In the syngeneic animal model of late-stage disseminated breast cancer bone metastasis, the treatment with targeted DTX-loaded micelles attenuated the tumorigenesis and significantly improved animal lifespan compared to the conventional surfactant-based formulation (free DTX). These findings indicate potential applications of the osteotropic nanomedicines for bone metastasis treatment.

Link between estrogen deficiency osteoporosis and susceptibility to bone metastases: A way towards precision medicine in cancer patients

Different fields of cancer management consider bone health to be of increasing clinical importance for patients: 1) presence of bone metastases in many solid tumors, 2) use of bone-targeted treatments in the reduction of bone metastasis, 3) effects of cancer treatment on reproductive hormones, critical for normal bone remodeling maintenance. Additionally, bone microenvironment is further complicated by the decline of ovarian sex steroid production and by the related increase in inflammatory factors linked to menopause, which result in accelerated bone loss and increased risk of osteoporosis (OP). Similarly, cancers and metastasis to bone showed a close relationship with sex hormones (particularly estrogen). Thus, these findings raise a question: Could pre-existing estrogen deficiency OP promote and/or influence cancer cell homing and tumor growth in bone? Although some preclinical and clinical evidence exists, it is mandatory to understand this aspect that would be relevant in the clinical theatre, where physicians need to understand the treatments available to reduce the risk of skeletal disease in cancer patients. This descriptive systematic review summarizes preclinical and clinical studies dealing with bimodal interactions between pre-existing estrogen deficiency OP and bone metastasis development and provides evidence supporting differences in tumor growth and colonization between healthy and OP status. Few studies evaluated the impact of estrogen deficiency OP on the susceptibility to bone metastases. Therefore, implementing biological knowledge, could help researchers and clinicians to have a better comprehension of the importance of pre- and post-menopausal bone microenvironment and its clinical implications for precision medicine in cancer patients.

Effects of discontinuing oral bisphosphonate treatments for postmenopausal osteoporosis on bone turnover markers and bone density

The antiresorptive potency varies between different bisphosphonates. We investigated the effect of stopping oral bisphosphonate treatment for postmenopausal osteoporosis (ibandronate, alendronate, risedronate) on BTMs and BMD. After stopping treatment, all three groups showed an increase in BTMs and a decrease in hip BMD; however, none returned to pre-treatment baseline values.

INTRODUCTION

Bisphosphonates (BPs) continue to suppress bone turnover markers (BTMs) after treatment has stopped, leading to the suggestion that a pause in treatment could be considered for low-risk patients. Indirect comparisons suggest that after cessation of treatment, the effects on bone may differ between drugs. We investigated the effects of stopping oral BP treatments for postmenopausal osteoporosis on BTMs and bone mineral density (BMD).

METHODS

We studied postmenopausal osteoporotic women who had previously taken part in a 2-year randomised study of three oral BPs (ibandronate, alendronate, or risedronate). At the end of the study, women with hip BMD T-score > - 2.5 and considered clinically appropriate to discontinue treatment were invited to participate in a further 2-year observational study. Biochemical response was assessed using BTMs, and BMD was measured by dual-energy X-ray absorptiometry.

RESULTS

All BTMs increased after treatment withdrawal but remained below the pre-treatment baseline with less suppression of BTMs for the risedronate group compared to alendronate and ibandronate up to 48 weeks. There was no difference between the BP groups 96 weeks after stopping treatment. The change in BMD during the 96 weeks after stopping treatment was - 1.6% (95% CI - 1.9 to - 1.2, P < 0.001) for the total hip and - 0.6% (95% CI - 1.1 to - 0.2, P = 0.17) at the lumbar spine with no difference between the three BP groups (P = 0.85 and P = 0.48, respectively).

CONCLUSION

For all treatment groups, there was an increase in BTMs and a decrease in hip BMD after stopping BPs for 2 years; however, none returned to pre-treatment baseline values.

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.

Functional osteoclastogenesis: the baseline variability in blood donor precursors is not associated with age and gender

Mononuclear osteoclast precursors circulate in the monocyte fraction of peripheral blood and form multinuclear cells with all osteoclastic phenotypic characteristics when cultured in the presence of macrophage colony stimulating factor (M-CSF) and receptor activator of nuclear factor kB ligand (RANKL). The method to obtain osteoclast precursors from peripheral blood is simple but the number of recovered osteoclasts is often largely insufficient for functional analyses. The original aim of this study was to develop a rapid and efficient method that could overcome the donor variability and enrich the osteoclast precursors from a small volume of peripheral blood as a basis for future clinical studies to correlate the differentiation potential of circulating osteoclast precursors with bone lesions in cancer patients. We improved the efficiency of osteoclastogenesis by reducing isolation and purification times and overcame the use of flow cytometry and immunomagnetic purification procedures. In our culture system the osteoclast number was increased several-fold and the precursors were able to reach a full differentiation within seven days of culture. Both age as well as gender differences in osteoclastogenesis efficiency were no longer evident by processing limited volume blood samples with this simple and rapid method.

The effect of alendronate soaking and ultraviolet treatment on bone-implant interface

OBJECTIVE

Rapid and stable fixation of dental implants is crucial for successful treatment. Herein, we examined whether the simultaneous treatment of titanium implants with ultraviolet (UV) and alendronate (ALN) synergistically improved the bone-to-implant contact.

MATERIALS AND METHODS

We assessed the in vitro effects of UV radiation-treated (UV+/ALN-), ALN-soaked (UV-/ALN+), and UV radiation/ALN-treated (UV+/ALN+) titanium implants on cell proliferation, cytotoxicity, cell adhesion, and osteoblast differentiation using MG-63 osteoblast-like cells by the assays of MTS, live/dead, scanning electron microscopy (SEM), alkaline phosphatase (ALP) activity, and alizarin red S (AR-S) staining, respectively. Furthermore, in vivo bone formation at the bone-implant interface efficiency determined using a rabbit tibia implantation. Implants were divided into 3 experimental groups (UV+/ALN-, UV-/ALN+, UV+/ALN+) and the non-treated control (UV-/ALN-) group and transplanted into the proximal tibia of rabbits. At 1, 2, 4, and 8 weeks post-operation, bone formation at the bone-implant interface was evaluated by micro-computed tomography and histological analysis.

RESULTS

MG-63 cells cultured on UV+/ALN+ implants showed significantly higher cell proliferation, ALP activity, and calcium mineralization than those cultured on other implants (P < 0.05). Furthermore, SEM observation showed the highest increase in cell attachment and growth on the UV+/ALN+ implants. In vivo, experimental groups at all time points showed greater peri-implant bone formation than the control group. At 8 weeks post-implantation, in the UV+/ALN+ group, significantly higher bone formation was observed than the UV+/ALN- or UV-/ALN+ group, respectively (P < 0.05).

CONCLUSIONS

Treatment of titanium surfaces with UV and ALN may synergistically enhance osteoblastic differentiation and mineralization in vitro and enhance bone formation at the bone-implant interface in vivo. These data suggest that UV and ALN treatment may improve the osseointegration of titanium implants.

Alendronate-loaded hydroxyapatite-TiO2 nanotubes for improved bone formation in osteoporotic rabbits

Alendronate-loaded hydroxyapatite-TiO₂ nanotubes were fabricated for locally improving new bone formation at the bone–implant interface in osteoporotic rabbits.

Bone-immune cell crosstalk: bone diseases

Bone diseases are associated with great morbidity; thus, the understanding of the mechanisms leading to their development represents a great challenge to improve bone health. Recent reports suggest that a large number of molecules produced by immune cells affect bone cell activity. However, the mechanisms are incompletely understood. This review aims to shed new lights into the mechanisms of bone diseases involving immune cells. In particular, we focused our attention on the major pathogenic mechanism underlying periodontal disease, psoriatic arthritis, postmenopausal osteoporosis, glucocorticoid-induced osteoporosis, metastatic solid tumors, and multiple myeloma.

Effects of alendronate on osteoclast formation and activity in vitro

INTRODUCTION

Root resorption is a common complication after replantation following traumatic dental avulsion. Endodontic therapy combined with local and intracanal medications aims to avoid osteoclastic activity. In such cases, the application of alendronate (ALN), a bisphosphonate widely used for the treatment of bone disorders, could be of clinical relevance. This study evaluated alendronate biocompatibility on periodontal ligament cells as well as its effects on an in vitro osteoclastogenesis model.

METHODS

Alendronate cytotoxicity (10(-3) to 10(-9) mol/L) in human periodontal ligament fibroblasts, human osteogenic sarcoma cells, and murine osteoclastic precursors (RAW 264.7) was analyzed using cell number determination, cell viability, and proliferation assays. ALN (10(-6) to 10(-12) mol/L) effects on RANKL-induced osteoclastogenesis of RAW cells were assessed by tartrate-resistant acid phosphatase (TRAP) staining and activity and real-time polymerase chain reaction.

RESULTS

ALN at higher concentrations was cytotoxic for all cell types, inhibiting significantly the proliferation of human osteogenic sarcoma cells and human periodontal ligament fibroblasts (≥10(-5) mol/L). TRAP activity and expression of the osteoclast markers TRAP and cathepsin K by RAW-derived osteoclasts decreased significantly with ALN at low concentrations, reaching the maximum effect at 10(-10) mol/L.

CONCLUSIONS

We showed that ALN at very low concentrations is an effective inhibitor of RANKL-generated osteoclasts, without causing cytotoxic effects on their precursors or periapical cells. ALN at such concentrations might be useful to prevent replacement resorption in avulsed teeth.

Targeted depletion of tumour-associated macrophages by an alendronate-glucomannan conjugate for cancer immunotherapy

Tumour-associated macrophages (TAMs) are a set of macrophages residing in the tumour microenvironment. They play essential roles in mediating tumour angiogenesis, metastasis and immune evasion. Delivery of therapeutic agents to eliminate TAMs can be a promising strategy for cancer immunotherapy but an efficient vehicle to target these cells is still in pressing need. In this study, we developed a bisphosphonate-glucomannan conjugate that could efficiently target and specifically eliminate TAMs in the tumour microenvironment. We employed the polysaccharide from Bletilla striata (BSP), a glucomannan affinitive for macrophages that express abundant mannose receptors, to conjugate alendronate (ALN), a bisphosphonate compound with in vitro macrophage-inhibiting activities. In both in vitro and in vivo tests, the prepared ALN-BSP conjugate could preferentially accumulate in macrophages and induced them into apoptosis. In the subcutaneous S180 tumour-bearing mice model, the treatment using ALN-BSP effectively eliminated TAMs, remarkably inhibited angiogenesis, recovered local immune surveillance, and eventually suppressed tumour progression, without eliciting any unwanted effect such as systematic immune response. Interestingly, ALN alone failed to exhibit any anti-TAM activity in vivo, probably because this compound was susceptible to the mildly acidic tumour microenvironment. Taken together, these results demonstrate the potential of ALN-BSP as a safe and efficient tool targeted at direct depletion of TAMs for cancer immunotherapy.

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.

Assessment of OPG/RANK/RANKL gene expression levels in peripheral blood mononuclear cells (PBMC) after treatment with strontium ranelate and ibandronate in patients with postmenopausal osteoporosis

CONTEXT

Recent research results have confirmed the high significance of the OPG/RANK/RANKL system in the development of bone diseases.

AIM

The aim of the reported study was to assess gene expression levels of the OPG/RANK/RANKL system in peripheral blood mononuclear cells (PBMCs) after strontium ranelate (SR) and ibandronate administered to patients with postmenopausal osteoporosis.

PATIENTS AND METHODS

A total of 89 postmenopausal women, aged 51 to 85 years, patients of the Outpatient Clinic of Osteoporosis of the Military Teaching Hospital in Lodz, were enrolled into the study. The patients were randomly assigned to different medical therapies: ibandronate and SR. Patients of the control group received only calcium and vitamin D₃ supplements. Patient visits were repeated after 3 and 6 months. Measurements of serum alkaline phosphatase concentrations and of RNA expression in PBMCs as well as of total serum calcium and phosphate levels and of their 24-hour urine excretion rates were carried out in material, collected at baseline and after 3 and 6 months of the therapy. Densitometry of the left hip and of the lumbar spine was done at the baseline visit and after 6 months.

RESULTS

The differences in gene expressions of RANKL and RANK were not significant during the study period and did not differ between the groups in a statistically significant manner. No OPG gene expression was observed in PBMCs of patients in any of the studied groups and at any time point. The tendency of correlation (P = .07) was observed between decreasing RANK gene expression and increasing bone mineral density in the patients treated with SR.

CONCLUSIONS

Both ibandronate and SR do not seem to cause any significant changes in gene expression levels of OPG/RANK/RANKL in PBMCs during the first 6 months of treatment.

No reduction in circulating preosteoclasts 18 months after treatment with zoledronate: analysis from a randomized placebo controlled trial

The conventional model that bisphosphonates bind to the bone surface and inhibit mature osteoclasts does not convincingly explain the prolonged duration of action of zoledronate. We hypothesized that zoledronate on the bone surface adjacent to marrow cells impairs osteoclastogenesis, contributing to sustained inhibition of resorption. In this case, numbers of circulating preosteoclasts may be reduced after zoledronate treatment. This study assessed this possibility in subjects from a clinical trial. Twenty-two osteopenic women participating in a randomized, controlled trial comparing zoledronate 5 mg with placebo were recruited, 18 months after administration of study drug. Peripheral blood mononuclear cells were analyzed for the presence of osteoclast precursors using flow cytometry for preosteoclast markers and the ability to form osteoclast-like cells in culture with RANKL and M-CSF. There was no difference in the percentage of CD14(+)/CD11b(+) cells in peripheral blood between the two groups. The numbers of TRAP(+) multinucleated cells in cultures in the absence of RANKL and M-CSF were very low in both groups, but a significantly higher number of these cells was observed in the zoledronate group compared with the placebo group (p = 0.01). The number of TRAP(+) multinucleated cells and resorption pits following culture with RANKL and M-CSF did not differ between the two groups. Serum P1NP was reduced 53 % at 18 months in the zoledronate group but unchanged in the placebo group. These results do not support the hypothesis that the inhibitory action of zoledronate contributes to its prolonged action on preosteoclasts within bone marrow.

Bisphosphonate- and statin-induced enhancement of OPG expression and inhibition of CD9, M-CSF, and RANKL expressions via inhibition of the Ras/MEK/ERK pathway and activation of p38MAPK in mouse bone marrow stromal cell line ST2

Osteoclast differentiation is influenced by receptor activator of the NF-κB ligand (RANKL), macrophage colony-stimulating factor (M-CSF), and CD9, which are expressed on bone marrow stromal cells and osteoblasts. In addition, osteoprotegerin (OPG) is known as an osteoclastogenesis inhibitory factor. In this study, we investigated whether bisphosphonates and statins increase OPG expression and inhibit the expression of CD9, M-CSF, and RANKL in the bone marrow-derived stromal cell line ST2. We found that bisphosphonates and statins enhanced OPG mRNA expression and inhibited the expression of CD9, M-CSF, and RANKL mRNA. Futhermore, bisphosphonates and statins decreased the membrane localization of Ras and phosphorylated ERK1/2, and activated the p38MAPK. This indicates that bisphosphonates and statins enhanced OPG expression, and inhibited the expression of CD9, M-CSF, and RANKL through blocking the Ras/ERK pathway and activating p38MAPK. Accordingly, we believe that its clinical applications will be investigated in the future for the development of osteoporosis therapy.

Downregulation of the inflammatory response by CORM-3 results in protective effects in a model of postmenopausal arthritis

CO-releasing molecules (CORMs) are a new class of drugs able to release small amounts of CO in biological systems. We have shown previously that one of these molecules, CORM-3, exerts anti-inflammatory effects in animal models. The aim of this study was to assess the effects of CORM-3 on bone metabolism in a model of postmenopausal rheumatoid arthritis osteoporosis. Ovariectomy was followed by collagen-induced arthritis in female DBA-1/J mice. Animals showing arthritis on day 22 after immunization were then randomized into control and treatment groups. CORM-3 was administered at 10 mg/kg, intraperitoneally, once a day. Alendronate was administered at 100 μg/kg, orally, once a day. On days 36 and 50 after immunization, animals were killed and tissues analyzed. The arthritic score was significantly reduced by CORM-3 but not by alendronate treatment. Histopathological analyses indicated that both compounds reduced cellular infiltration and cartilage degradation. Local bone erosion and reduction in TNFα levels were seen for CORM-3 on day 50 and for alendronate on day 36. Serum levels of COMP, IL-6, MMP-3, CTX-I, alkaline phosphatase, and osteocalcin were decreased by both treatments, whereas TNFα levels were reduced by CORM-3 and TRAP-5b by alendronate. Micro-computed tomographic analysis showed protective effects on trabecular bone, which were more prominent for CORM-3 on day 36 and for alendronate on day 50. Our results suggest that CORMs represent a novel anti-inflammatory strategy to counteract joint bone erosion with partial protective effects on systemic bone loss in postmenopausal rheumatoid arthritis.

Teriparatide increases the maturation of circulating osteoblast precursors

This study shows that teriparatide promotes the circulating osteoblast (OB) precursor degree of maturation in patients affected by postmenopausal osteoporosis.

INTRODUCTION

Anabolic treatment with teriparatide has proven effective for the therapy of postmenopausal osteoporosis and significantly reduces the risk of non-vertebral fragility fractures. The aim of this study was to investigate the effect of teriparatide on circulating OB precursors.

METHODS

We evaluated by flow cytometry and real-time PCR the expression of OBs typical markers in peripheral blood mononuclear cells during treatment with teriparatide plus calcium and vitamin D, raloxifene plus calcium and vitamin D or calcium and vitamin D alone at various time points. Serum bone alkaline phosphatase and osteocalcin (OC) were measured as markers of bone turnover.

RESULTS

Our results show that circulating OB precursors are more numerous and more immature in patients affected by fragility fractures than in osteoporotic patients without fractures. We also show that teriparatide treatment increases the expression of alkaline phosphatase and of OC in OB precursors; thus, it increases their degree of maturation.

CONCLUSIONS

We suggest that teriparatide acts as anabolic agents also by promoting the maturation of OB precursors.

Parathyroid hormone regulates the distribution and osteoclastogenic potential of hematopoietic progenitors in the bone marrow

Parathyroid hormone (PTH) increases both the number of osteoclast in bone and the number of early hematopoietic stem cells (HSCs) in bone marrow. We previously characterized the phenotype of multiple populations of bone marrow cells with in vitro osteoclastogenic potential in mice. Here we examined whether intermittent administration of PTH influences these osteoclast progenitor (OCP) populations. C57BL/6 mice were treated with daily injections of bPTH(1-34) (80 µg/kg/day) for 7 or 14 days. We found that PTH caused a significant increase in the percentage of TN/CD115(+) CD117(high) and TN/CD115(+) CD117(int) cells (p < .05) in bone marrow on day 7. In contrast, PTH decreased the absolute number of TN/CD115(+) CD117(low) cells by 39% on day 7 (p < .05). On day 14, there was no effect of PTH on osteoclast progenitor distribution in vivo. However, PTH treatment for 7 and 14 days did increase receptor activator of NF-κB ligand (RANKL)- and macrophage colony-stimulating factor (M-CSF)-stimulated in vitro osteoclastogenesis and bone resorption in TN/CD115(+) cells. In the periphery, 14 days of treatment increased the percentage and absolute numbers of HSCs (Lin(-) CD117(+) Sca-1(+) ) in the spleen (p < .05). These data correlated with an increase in the percent and absolute numbers of HSCs in bone marrow on day 14 (p < .05). Interestingly, the effects on hematopoietic progenitors do not depend on osteoclast resorption activity. These results suggest that in vivo PTH treatment increased in vitro osteoclastogenesis and resorption without altering the number of osteoclast precursors. This implies that in vivo PTH induces sustained changes, possibly through an epigenetic mechanism, in the in vitro responsiveness of the cells to M-CSF and RANKL.

The role of circulating bone cell precursors in fracture healing

Fracture healing is a complex process that involves several cell types; as a previous report suggested an increase in osteoblast (OB) precursors in peripheral blood during this process, this paper examines the role of circulating bone cell precursors in this process in the light of a prior suggestion that OB precursors are increased. Nine healthy men less than 60 years old with traumatic fractures were enrolled. The parameters circulating OB precursors (osteocalcin+/alkaline phosphatase+/CD15- cells) and osteoclast precursors (CD14+/CD11b+/vitronectin receptor + cells) were measured by flow cytometry; bone formation markers and TGFbeta1, by ELISA; and PTH, by RIA in serum on arrival at the emergency department (baseline) and 15 days after fracture. Bone cell precursors behaved differently during healing. TGFbeta1 was inversely correlated with OB number, but increased their degree of maturation at baseline. Bone formation markers and TGFbeta1 were increased after fracture, whereas PTH was decreased. The TGFbeta1 increase was directly correlated with age, whereas age was not correlated with the precursors. In conclusion, we confirm the role of TGFbeta1 in fracture healing; and its possible role in the control of pre-OB homeostasis. There was no variation in circulating precursor cells during healing, though the increase in TGFbeta1 may suggest increased pre-OB maturation and homing to the injured site.