Bisphosphonates pathway

Mechanisms of Ellagic Acid (EA)-Mediated Osteogenic Differentiation of Human Dental Pulp-Derived Stem Cells

Ellagic acid (EA) is a potent antioxidant that reduces oxidative stress and promotes differentiation. By lowering the harmful levels of reactive oxygen species (ROS), EA fosters an environment conducive to the osteoblastic differentiation (OB) of stem cells. In addition, it promotes autophagy and mitophagy, which are vital for promoting differentiation. Effective autophagic activity recycles damaged organelles and proteins, meeting the energy required during differentiation and shielding from apoptosis. However, molecular mechanisms underlying the osteogenic differentiation of mesenchymal stem cells remain inadequately explored. Therefore, the current study aims to define the regulatory role of EA during the OB of dental pulp-derived stem cells (DPSC) and to study how autophagy and mitophagy are being modulated during this differentiation process. Herein, we showed that the expression level of osteoblast-specific markers, autophagy, and mitophagy-associated markers was significantly elevated during EA-mediated OB differentiation of DPSC. Moreover, we found that the EA induced the osteoblastic-specific markers through canonical BMP2 pathway molecules, reduced ROS in both basal and activated states, and induced autophagy and mitophagy molecules along with enhanced mitochondrial functions. Cell cycle analysis revealed that the G1 phase was arrested via phosphorylation of γ-H2AX, ATM, and CHK2 proteins. Furthermore, in silico analysis revealed that EA strongly binds with osteonectin, a crucial noncollagen protein involved in bone remodeling, and confirmed by Western blot analysis. These results support that EA could be a promising natural compound for bone repair and regeneration applications.

Combinatorial effects of hydroxyapatite and Tualang honey on medication-related osteonecrosis of the jaw (MRONJ): An in vitro study

BACKGROUND

Medication-related osteonecrosis of the jaw (MRONJ) is a severe complication associated with prolonged bisphosphonate therapy. Increasing evidence shows that mucosal damage plays an important role in the pathogenesis of MRONJ. This study investigates the combinatorial effects of hydroxyapatite with Tualang honey on cell viability and wound healing in MRONJ.

MATERIALS AND METHODS

The incorporation of Tualang honey into hydroxyapatite was assessed using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and field emission scanning electron-energy dispersive X-ray analysis microscopy (FESEM-EDX). The effect of hydroxyapatite combined with Tualang honey on cell viability was determined by WST-1 assay and wound healing was assessed by scratch assay.

RESULTS

The incorporation of Tualang honey into hydroxyapatite altered the functional groups, structure, size, morphology, and components of the crystal as evidenced by FTIR, XRD and FESEM-EDX analysis. High concentrations of pamidronic acid inhibit oral fibroblast viability and wound healing. Low and high concentrations of hydroxyapatite demonstrate non-toxicity towards fibroblast cells. Furthermore, hydroxyapatite reversed the action of pamidronic acid on the cells; it increased fibroblast viability but did not close the wound. Tualang honey promotes fibroblast viability and wound closure. However, the addition of Tualang honey is unable to overcome the inhibitory effects of pamidronic acid on fibroblasts. The addition of Tualang honey and hydroxyapatite improved the cell viability and accelerated wound closure of fibroblast exposed to pamidronic acid.

CONCLUSION

These findings demonstrated that the combination treatment protects oral fibroblasts by preventing bisphosphonate toxicity.

Asperuloside alleviates osteoporosis by promoting autophagy and regulating Nrf2 activation

BACKGROUND

Osteoporosis is a metabolic bone disease that has a common occurrence in postmenopausal women. Asperuloside (ASP) has been reported to exert anti-inflammatory and anti-oxidative effects in numerous diseases, such as rheumatoid arthritis and acute lung injury. However, whether ASP plays a role in osteoporosis has not been addressed.

METHODS

In vivo, ovariectomy (OVX) was used to induce mouse osteoporosis. Then, the mice were treated with 20 and 40 mg/kg ASP. In vitro, MC3T3-E1 cells were treated with 0, 1, 10, 20, 40 and 80 µM ASP. We chose 20 and 40 µM for further experiments due to no significant effects on cell viability.

RESULTS

The data indicated that ASP reduced osteoporosis in OVX mice and promoted osteogenic differentiation and mineralization in MC3T3-E1 cells. In addition, we explored that ASP protected against osteoporosis via inducing autophagy and activating Nrf2.

CONCLUSION

ASP alleviates OVX-induced osteoporosis by promoting autophagy and regulating Nrf2 activation.

Synthesis of Metastable Calcium Carbonate Using Long-Chain Bisphosphonate Molecules

Cementation in construction materials primarily relies on the aqueous precipitation of minerals such as carbonates and silicates. The kinetics of nucleation and growth play a critical role in the development of strength and durability, yet our understanding of the kinetic controls governing phase formation and porosity reduction in cements remains limited. In this study, we synthesized bisphosphonate molecules with varying alkyl chain lengths and functional groups to investigate their impact on calcium carbonate precipitation. Through conductivity measurements, infrared spectroscopy, and thermogravimetric analysis, we uncovered the selective formation of polymorphs and the specific incorporation of these molecules within the carbonate matrix. Further, in situ atomic force microscopy revealed that these molecules influenced the morphology of the precipitates, indicating a possible effect on the ionic organization through sorption mechanisms. Interestingly, amorphous calcium carbonate (ACC), when formed in the presence of bisphosphonates, showed metastability for at least seven months without inhibiting further calcium carbonate precipitation. Our research sheds light on the diverse mechanisms by which organic additives can modify mineral nucleation and growth, offering valuable insights for the control and enhancement of carbonate-based cementation processes.

Farnesyl Diphosphate Synthase Gene Associated with Loss of Bone Mass Density and Alendronate Treatment Failure in Patients with Primary Osteoporosis

Aminobisphosphonates (NBPs) are the first-choice medication for osteoporosis (OP); NBP treatment aims at increasing bone mineral density (BMD) by inhibiting the activity of farnesyl diphosphate synthase (FDPS) enzyme in osteoclasts. Despite its efficacy, inadequate response to the drug and side effects have been reported. The A allele of the rs2297480 (A > C) SNP, found in the regulatory region of the FDPS gene, is associated with reduced gene transcription. This study evaluates the FDPS variant rs2297480 (A > C) association with OP patients' response to alendronate sodium treatment. A total of 304 OP patients and 112 controls were enrolled; patients treated with alendronate sodium for two years were classified, according to BMD variations at specific regions (lumbar spine (L1-L4), femoral neck (FN) and total hip (TH), as responders (OP-R) (n = 20) and non-responders (OP-NR) (n = 40). We observed an association of CC genotype with treatment failure (p = 0.045), followed by a BMD decrease in the regions L1-L4 (CC = -2.21% ± 2.56; p = 0.026) and TH (CC = -2.06% ± 1.84; p = 0.015) after two years of alendronate sodium treatment. Relative expression of the FDPS gene was also evaluated in OP-R and OP-NR patients. Higher expression of the FDPS gene was also observed in OP-NR group (FC = 1.84 ± 0.77; p = 0.006) when compared to OP-R. In conclusion, the influence observed of FDPS expression and the rs2897480 variant on alendronate treatment highlights the importance of a genetic approach to improve the efficacy of treatment for primary osteoporosis.

Synergistic effect of zoledronate and compressive force suppresses proliferation and differentiation of human gingival fibroblasts

We investigated the effects of zoledronate (ZA) and compressive force, separately and in combination, on the proliferation and differentiation of human gingival fibroblasts (HGFs) to verify the mechanism underlying medication-related osteonecrosis of the jaw (MRONJ). The addition of 100 µM ZA markedly inhibited cell proliferation. Expression of type I collagen, fibroblast growth factor 2, and connective tissue growth factor genes, was decreased by ZA and compressive force. Similar results were observed for collagen expression by using Sirius red staining. These results, together with clinical findings that MRONJ is more common in cases with excessive mechanical stress on the oral mucosa, suggest that bisphosphonates such as ZA and mechanical stress may act in conjunction as risk factors for the development of MRONJ by affecting homeostasis of the oral mucosal tissues, including HGFs.

Multifunctional electrospun nanofibrous scaffold enriched with alendronate and hydroxyapatite for balancing osteogenic and osteoclast activity to promote bone regeneration

Electrospun composite nanofiber scaffolds are well known for their bone and tissue regeneration applications. This research is focused on the development of PVP and PVA nanofiber composite scaffolds enriched with hydroxyapatite (HA) nanoparticles and alendronate (ALN) using the electrospinning technique. The developed nanofiber scaffolds were investigated for their physicochemical as well as bone regeneration potential. The results obtained from particle size, zeta potential, SEM and EDX analysis of HA nanoparticles confirmed their successful fabrication. Further, SEM analysis verified nanofiber's diameters within 200-250 nm, while EDX analysis confirmed the successful incorporation of HA and ALN into the scaffolds. XRD and TGA analysis revealed the amorphous and thermally stable nature of the nanofiber composite scaffolds. Contact angle, FTIR analysis, Swelling and biodegradability studies revealed the hydrophilicity, chemical compatibility, suitable water uptake capacity and increased in-vitro degradation making it appropriate for tissue regeneration. The addition of HA into nanofiber scaffolds enhanced the physiochemical properties. Additionally, hemolysis cell viability, cell adhesion and proliferation by SEM as well as confocal microscopy and live/dead assay results demonstrated the non-toxic and biocompatibility behavior of nanofiber scaffolds. Alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase (TRAP) assays demonstrated osteoblast promotion and osteoclast inhibition, respectively. These findings suggest that developed HA and ALN-loaded PVP/PVA-ALN-HA nanofiber composite scaffolds hold significant promise for bone regeneration applications.

The Capacity of Magnesium to Induce Osteoclast Differentiation Is Greatly Enhanced by the Presence of Zoledronate

Bisphosphonates (BPs) are successfully used to cure a number of diseases characterized by a metabolic reduction in bone density, such as Osteoporosis, or a neoplastic destruction of bone tissue, such as multiple myeloma and bone metastases. These drugs exert their therapeutic effect by causing a systemic osteoclast depletion that, in turn, is responsible for reduced bone resorption. Unfortunately, in addition to their beneficial activity, BPs can also determine a frightening side effect known as osteonecrosis of the jaw (ONJ). It is generally believed that the inability of osteoclasts to dispose of inflamed/necrotic bone represents the main physiopathological aspect of ONJ. In principle, a therapeutic strategy able to elicit a local re-activation of osteoclast production could counteract ONJ and promote the healing of its lesions. Using an experimental model of Vitamin D3-dependent osteoclastogenesis, we have previously demonstrated that Magnesium is a powerful inducer of osteoclast differentiation. Here we show that, surprisingly, this effect is greatly enhanced by the presence of Zoledronate, chosen for our study because it is the most effective and dangerous of the BPs. This finding allows us to hypothesize that Magnesium might play an important role in the topical therapy of ONJ.

A Five-Year Retrospective Audit on Bone Protection Prescribing in Patients With Fragility Fractures in Primary Care

Background Fragility fractures typically occur in the elderly population due to low-energy trauma in the context of underlying osteoporotic bone disease. These fractures are becoming increasingly more common as the population of the United Kingdom ages, representing a significant public health issue. In the community, a joint care approach is adopted between general practitioners and fracture liaison services for the management of patients with fragility fractures. Despite this, preventive care for these patients remains substandard. This project aimed to conduct an audit of patients with a coded diagnosis of a fragility fracture in our primary care practice to ascertain fracture type and the prescription of bone protective agents. When necessary, the appropriate therapy was commenced per best practice guidelines. Methodology A search of patients with the diagnosis of Fragility fracture on our electronic patient database, SystmOne, was conducted for the period of April 2019 to April 2023 inclusive. A retrospective audit of electronic patient records was done to identify patient demographic data, fracture types and dates, osteoporosis prescriptions, vitamin D/calcium supplementation, and bone densitometry scan results (dual-energy X-ray absorptiometry). Results A total of 47 patients were identified with a coded diagnosis of a Fragility fracture, of whom 36 were females and 11 were males. The average age of the patients was 76.89 years with a range of 50 to 97. In total, 49 fractures were identified. More than two-thirds of the fractures identified were either distal forearm or neck of femur fractures (18 and 15, respectively). Of the 47 patients identified, 33 were on bone protection agents. Further, 26 received both bisphosphonates and calcium/vitamin D supplementation. Seven patients were on bisphosphonate monotherapy, and the remaining two patients were on vitamin D/calcium supplementation alone. Of the 47 patients, 12 had neither form of therapy prescribed. Conclusions Despite the joint effort between fracture liaison services and general practitioners, the secondary prevention of fragility fractures within the community remains inadequate. Fragility fractures are associated with significant morbidity, mortality, and re-fracture rates and incur significant costs to the National Health Service. Local practitioners must routinely evaluate their data to identify opportunities to improve patient care. Effective and timely treatment could be key to the prevention of new or second fractures.

Beneficial Effects of Zoledronic Acid on Tendons of the Osteogenesis Imperfecta Mouse (Oim)

Osteogenesis imperfecta (OI) is a genetic disorder of connective tissue characterized by spontaneous fractures, bone deformities, impaired growth and posture, as well as extra-skeletal manifestations. Recent studies have underlined an impairment of the osteotendinous complex in mice models of OI. The first objective of the present work was to further investigate the properties of tendons in the osteogenesis imperfecta mouse (oim), a model characterized by a mutation in the COL1A2 gene. The second objective was to identify the possible beneficial effects of zoledronic acid on tendons. Oim received a single intravenous injection of zoledronic acid (ZA group) at 5 weeks and were euthanized at 14 weeks. Their tendons were compared with those of untreated oim (oim group) and control mice (WT group) by histology, mechanical tests, western blotting and Raman spectroscopy. The ulnar epiphysis had a significantly lower relative bone surface (BV/TV) in oim than WT mice. The tendon of the triceps brachii was also significantly less birefringent and displayed numerous chondrocytes aligned along the fibers. ZA mice showed an increase in BV/TV of the ulnar epiphysis and in tendon birefringence. The tendon of the flexor digitorum longus was significantly less viscous in oim than WT mice; in ZA-treated mice, there was an improvement of viscoelastic properties, especially in the toe region of stress-strain curve, which corresponds to collagen crimp. The tendons of both oim and ZA groups did not show any significant change in the expression of decorin or tenomodulin. Finally, Raman spectroscopy highlighted differences in material properties between ZA and WT tendons. There was also a significant increase in the rate of hydroxyproline in the tendons of ZA mice compared with oim ones. This study highlighted changes in matrix organization and an alteration of mechanical properties in oim tendons; zoledronic acid treatment had beneficial effects on these parameters. In the future, it will be interesting to better understand the underlying mechanisms which are possibly linked to a greater solicitation of the musculoskeletal system.

Ocular Side Effects of Bisphosphonates: A Review of Literature

In rare cases, bisphosphonates are well established to cause ocular inflammation, presenting as uveitis, episcleritis, scleritis, orbital inflammation, and/or conjunctivitis. Some reports of bisphosphonate-associated neuro-ophthalmic complications also exist. We identified 101 reports in the literature relating to bisphosphonate-associated ocular complications. In a great majority of cases, symptoms resolve after discontinuation of the drug and anti-inflammatory treatment. Many cases recur if rechallenged with the same bisphosphonate. First-generation nonamino bisphosphonates, including clodronate and etidronate, are not associated with ocular inflammation. Only 2nd- and 3rd-generation amino bisphosphonates, including pamidronate, alendronate, risedronate, ibandronate, and zoledronate are associated with these complications. The mechanism of bisphosphonate-induced ocular inflammation may be related to activation of γ/δ T cells or M1 macrophages. Intravenous forms, such as pamidronate and zoledronate, tend to have higher rates and faster onset of ocular inflammation, generally presenting within days of infusion. In oral bisphosphonates, such as alendronate and risedronate, these complications present with more sporadic timing. Rates of complications are also higher when bisphosphonates are used for malignancy, as doses tend to be higher compared with doses for osteoporosis.

Effects of Drugs and Chemotherapeutic Agents on Dental Implant Osseointegration: A Narrative Review

BACKGROUND

Dental implants have been one of the most popular treatments for rehabilitating individuals with single missing teeth or fully edentulous jaws since their introduction. As more implant patients are well-aged and take several medications due to various systemic conditions, clinicians should take into consideration the possible drug implications on bone remodeling and osseointegration.

OBJECTIVE

The present study aims to examine and review some desirable and unwelcomed implications of medicine on osseointegration.

METHODS

A broad search for proper relevant studies was conducted in four databases, including Web of Science, Pubmed, Scopus, and Google Scholar.

RESULTS

Some commonly prescribed medicines, such as nonsteroidal anti-inflammatory drugs (NSAIDs), glucocorticoids, proton pump inhibitors (PPIs), selective serotonin reuptake inhibitors (SSRIs), anticoagulants, metformin, and chemotherapeutic agents, may jeopardize osseointegration. On the contrary, some therapeutic agents, such as anabolic, anti-catabolic, or dual anabolic agents may enhance osseointegration and increase the treatment's success rate.

CONCLUSION

Systemic medications that enhance osseointegration include mineralization promoters and bone resorption inhibitors. On the other hand, medications often given to the elderly with systemic problems might interfere with osseointegration, leading to implant failure. However, to validate the research, more human studies with a higher level of evidence are required.

Zoledronic Acid Implant Coating Results in Local Medullary Bone Growth

Osteoarthritis (OA) can necessitate surgical interventions to restore the function of the joint in severe cases. Joint replacement surgery is one of the procedures implemented to replace the damaged joint with prosthetic implants in severe cases of OA. However, after successful implantation, a fraction of OA patients still require revision surgery due to aseptic prosthetic loosening. Insufficient osseointegration is one of the factors that contribute to such loosening of the bone implant, which is commonly made from titanium-based materials. Zoledronic acid (ZA), a potent bisphosphonate agent, has been previously shown to enhance osseointegration of titanium implants. Herein, we fabricated ZA/Ca composites using a reverse microemulsion method and coated them with 1,2-dioleoyl-sn-glycero-3-phosphate monosodium salt (DOPA) to form ZA/Ca/DOPA composites. Titanium alloy screws were subsequently dip-coated with a suspension of the ZA/Ca/DOPA composites and poly(lactic-co-glycolic) acid (PLGA) in chloroform to yield Za/PLGA-coated screws. The coated screws exhibited a biphasic in vitro release profile with an initial burst release within 48 h, followed by a sustained release over 1 month. To assess their performance in vivo, the Za/PLGA screws were then implanted into the tibiae of Sprague-Dawley rats. After 8 weeks, microCT imaging showed new bone growth along the medullary cavity around the implant site, supporting the local release of ZA to enhance bone growth around the implant. Histological staining further confirmed the presence of new mineralized medullary bone growth resembling the cortical bone. Such local medullary growth represents an opportunity for future studies with alternative coating methods to fine-tune the local release of ZA from the coating and enhance complete osseointegration of the implant.

Bone targeted new zoledronate derivative: design, synthesis, 99mTc-coupling, in-silico study and preclinical evaluation for promising osteosarcoma therapy

Background: Zoledronate suppresses human sarcomas by blocking the formation of geranylgeranyl diphosphate (GGPP) via inhibiting GGPP synthase.Objectives: Designing of new derivative of dronic acid (1-hydroxy-2-(4-nitro-1H-imidazol-1-yl)ethan-1,1-diyl)bis phosphonic acid), structurally related to zoledronate to be used for osteosarcoma therapy.Methods: 1-hydroxy-2-(4-nitro-1H-imidazol-1-yl)ethan-1,1-diyl)bis(phosphonic acid) was synthesized in one pot reaction with a yield of 65 ± 4%. The synthesized nitro-zoledronate compound was successfully radiolabeled with 99mTc with a radiochemical purity of 92.05%. Docking accuracy and scoring reliability for the new nitro-zoledronate with human GGPPS using MOE software has been presented.Results and Conclusion: The nitro-zoledronate successfully coupled with technetium-99m at high yield to investigate its in-vivo biodistribution which indicated highly selective uptake in the skeletal system and rapid clearance from soft tissues. The in-vitro cytotoxicity of the nitro-zoledronate was evaluated and potently inhibited the osteosarcoma cell line (MG-63) after 72 hours with an IC50 value of 10 μM. To summarize, our data point to a promising candidate to improve osteosarcoma therapy.

Use of zoledronic acid in antiosteoporosis treatment is associated with a decreased blood lipid level in postmenopausal women with osteoporosis: A cohort study in China

OBJECTIVE

: This cohort study aimed to evaluate the protective effects of zoledronic acid (ZA) in lipidemia in postmenopausal women with osteoporosis.

METHODS

A total of 668 postmenopausal women with osteoporosis were regularly followed up for 12 months between January 2018 and August 2021 in the department of endocrinology and the health examination center of the hospital. They were included in this cohort study. They were divided into group I and group II depending on lipid metabolism disorder; Group II received atorvastatin 20 mg/d orally. Groups I and II, divided into experimental group (ZA exposure) and control group (ZA nonexposure), depending on treatment with or without ZA. All the data were collected from the hospital's medical record system and passed ethical review.

RESULTS

In group I, which was the ZA exposure group(n = 164), the level of low-density lipoprotein cholesterol (LDL-C) was significantly lower than that before ZA treatment(P = 0.017); in the ZA nonexposure group(n = 158), the levels of LDL-C, total cholesterol (TC) and triglycerides (TG) significantly increased after 12 months of follow-up, (P = 0.005, P < 0.001 and P = 0.001). At the baseline, no significant difference was found in blood lipid indicators between the ZA exposure and nonexposure groups (P > 0.05), but the levels of LDL-C and TC in the exposed group significantly decreased after 12 months of follow-up, (P = 0.008 and P = 0.027). Also, the ZA exposure group had 47 new cases of lipid metabolism disorder, while the nonexposure group had 43 new cases of lipid metabolism disorder after 12 months of follow-up. In group II, which was the ZA exposure group(n=155), the levels of LDL-C and TC were significantly lower than those before ZA treatment(P < 0.001 and P < 0.001). At the baseline, the ZA exposure and nonexposure groups(n = 191), had no significant difference in blood lipid indicators (P > 0.05), but the levels of LDL-C and TC significantly decreased in the exposed group after 12 months of follow-up, (P < 0.001 and P = 0.003).

CONCLUSION

This cohort study found that ZA might exert a protective effect on lipid metabolism in postmenopausal women with osteoporosis. In postmenopausal women with lipid disorders suffering from osteoporosis, the treatment with ZA combined with atorvastatin or ZA alone significantly reduced the level of blood lipid (especially LDL-C and TC) compared with atorvastatin alone.

Phosphorylated and Phosphonated Low-Complexity Protein Segments for Biomimetic Mineralization and Repair of Tooth Enamel

Biomimetic mineralization based on self-assembly has made great progress, providing bottom-up strategies for the construction of new organic-inorganic hybrid materials applied in the treatment of hard tissue defects. Herein, inspired by the cooperative effects of key components in biomineralization microenvironments, a new type of biocompatible peptide scaffold based on flexibly self-assembling low-complexity protein segments (LCPSs) containing phosphate or phosphonate groups is developed. These LCPSs can retard the transformation of amorphous calcium phosphate into hydroxyapatite (HAP), leading to merged mineralization structures. Moreover, the application of phosphonated LCPS over phosphorylated LCPS can prevent hydrolysis by phosphatases that are enriched in extracellular mineralization microenvironments. After being coated on the etched tooth enamel, these LCPSs facilitate the growth of HAP to generate new enamel layers comparable to the natural layers and mitigate the adhesion of Streptococcus mutans. In addition, they can effectively stimulate the differentiation pathways of osteoblasts. These results shed light on the potential biomedical applications of two LCPSs in hard tissue repair.

Genome-wide Association Study Identified Chromosome 8 Locus Associated with Medication-Related Osteonecrosis of the Jaw

Medication-related osteonecrosis of the jaw (MRONJ) is a rare but serious drug-related adverse event. To identify pharmacogenomic markers of MRONJ associated with bisphosphonate therapy, we conducted a genomewide association study (GWAS) meta-analysis followed by functional analysis of 5,008 individuals of European ancestry treated with bisphosphonates, which includes the largest number of MRONJ cases to date (444 cases and 4,564 controls). Discovery GWAS was performed in randomly selected 70% of the patients with cancer and replication GWAS was performed in the remaining 30% of the patients with cancer treated with intravenous bisphosphonates followed by meta-analysis of all 3,639 patients with cancer. GWAS was also performed in 1,369 patients with osteoporosis treated with oral bisphosphonates. The lead single-nucleotide polymorphism (SNP), rs2736308 on chromosome 8, was associated with an increased risk of MRONJ with an odds ratio (OR) of 2.71 and 95% confidence interval (CI) of 1.90-3.86 (P = 3.57*10-8 ) in the meta-analysis of patients with cancer. This SNP was validated in the MRONJ GWAS in patients with osteoporosis (OR: 2.82, 95% CI: 1.55-4.09, P = 6.84*10-4 ). The meta-analysis combining patients with cancer and patients with osteoporosis yielded the same lead SNP rs2736308 on chromosome 8 as the top SNP (OR: 2.74, 95% CI: 2.09-3.39, P = 9.65*10-11 ). This locus is associated with regulation of the BLK, CTSB, and FDFT1 genes, which had been associated with bone mineral density. FDFT1 encodes a membrane-associated enzyme, which is implicated in the bisphosphonate pathway. This study provides insights into the potential mechanism of MRONJ.

Use of bisphosphonates in a retrospective case series of children and adolescents with complex regional pain syndrome

BACKGROUND

There is increasing evidence for the use of bisphosphonates to treat Complex Regional Pain Syndrome in adults. However, there are scarce data for their use in children with Complex Regional Pain Syndrome.

AIM

This retrospective case series aimed to analyze the effects of intravenous bisphosphonate use in children and adolescents with Complex Regional Pain Syndrome enrolled in a multidimensional pain treatment program.

METHODS

We analyzed the data of 16 patients (15 females and 1 male, mean age 14 ± 3 years) who received infusions of zoledronic acid (0.015 ± 0.0044mg/kg), pamidronate (0.72 ± 0.17mg/kg), or both depending on their initial response between October 2014 and December 2019. The primary endpoint of the study was the patient's global impression of change. Secondary outcomes included pain intensity, physical function, role function (school attendance), need for pain medications, and adverse effects.

RESULTS

Nine of 16 patients reported meaningful improvements (global impressions of change of 84% or higher) at a median follow-up time of 16 (8-21) months after their last infusion of bisphosphonates. There were also meaningful reductions in pain intensity and the need for pain medications. There was an increase in the proportion of patients with minimal or without physical disability, and almost all patients normalized their school activities. Thirteen patients (81%) reported adverse effects, mostly flu-like symptoms, for a few days after the infusion.

CONCLUSION

The use of bisphosphonate infusions may represent an effective treatment option for children with Complex Regional Pain Syndrome, not responding to multidisciplinary pain treatment programs.

Fenugreek steroidal saponins hinder osteoclastogenic bone resorption by targeting CSF-1R which diminishes the RANKL/OPG ratio

Osteoporosis is skeletal fragility caused by the excessive bone resorption due to osteoclastogenesis. But current drugs are less bioavailable and possess higher toxicity. Our study was conducted to identify safe oral bioavailable drugs from Fenugreek steroidal saponins and to delineate underlying mechanism of them to lower the osteoclastogenic bone resorption. We observed higher molecular docked binding affinities in finally selected eight hit compounds within the range of -11.0 to -10.1 kcal/mol which was greater than currently used drugs. Molecular Dynamics simulation with Root Mean Square Deviation (RMSD), Root Mean Square Fluctuation (RMSF), Solvent Accessible Surface Area (SASA) and Gyration trajectory projection reinforced the stability of the protein-ligand complexes. Pharmacokinetics analysis confirmed bioavailability of seven compounds out of eight, and drug likeliness and bioavailability profile evaluation indicated that they all are eligible to be developed as a potent oral inhibitor of CSF-1R. By literature mining knowledge-driven analysis, RNAseq data and Molecular Dynamics Simulation, we proposed that, the hit derivatives block the CSF-1/CSF-1R induced phosphorylation signaling pathway in both osteoclast and osteoblast resulting in hindrance of RANK expression and formation of Reactive oxygen species (ROS) in osteoclast and osteoblast respectively, thus declines the RANKL/OPG ratio, lowering the osteoclast survival, proliferation and differentiation.

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

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

Molecular Targeted Therapy for the Bone Loss Secondary to Pyogenic Spondylodiscitis Using Medications for Osteoporosis: A Literature Review

Pyogenic spondylodiscitis can cause severe osteolytic and destructive lesions in the spine. Elderly or immunocompromised individuals are particularly susceptible to infectious diseases; specifically, infections in the spine can impair the ability of the spine to support the trunk, causing patients to be bedridden, which can also severely affect the physical condition of patients. Although treatments for osteoporosis have been well studied, treatments for bone loss secondary to infection remain to be elucidated because they have pathological manifestations that are similar to but distinct from those of osteoporosis. Recently, we encountered a patient with severely osteolytic pyogenic spondylodiscitis who was treated with romosozumab and exhibited enhanced bone formation. Romosozumab stimulated canonical Wnt/β-catenin signaling, causing robust bone formation and the inhibition of bone resorption, which exceeded the bone loss secondary to infection. Bone loss due to infections involves the suppression of osteoblastogenesis by osteoblast apoptosis, which is induced by the nuclear factor-κB and mitogen-activated protein kinase pathways, and osteoclastogenesis with the receptor activator of the nuclear factor-κB ligand-receptor combination and subsequent activation of the nuclear factor of activated T cells cytoplasmic 1 and c-Fos. In this study, we review and discuss the molecular mechanisms of bone loss secondary to infection and analyze the efficacy of the medications for osteoporosis, focusing on romosozumab, teriparatide, denosumab, and bisphosphonates, in treating this pathological condition.

Treatment of Stage 2 Medication-Induced Osteonecrosis of the Jaw: A Case Series

Medication-induced jaw osteonecrosis (MRONJ) is a rare and serious disease with a negative impact on patients’ quality of life, whose exact cause remains unclear and which may have a multifactorial origin. Although there are different therapeutic protocols, there is still no consensus. This case series evaluated three patients diagnosed with staged 2 MRONJ treated at the University of Murcia dental clinic according to the protocols described by the Spanish Society of Oral and Maxillofacial Surgery and the American Association of Oral and Maxillofacial Surgeons. Within 12 months of the application of therapeutic protocols, the lesions were completely healed in all cases. Radiography showed slow but progressive healing with normal bone structure. Conservative treatment with antibiotics, chlorhexidine rinses and minimally invasive surgical intervention with necrotic bone resection is effective in treating stage 2 of MRONJ. In cases of refractory osteonecrosis, the application of platelet and leukocyte-rich fibrin (PRF-L) in the surgical approach improves the outcome in soft tissue healing and bone regeneration but further research is needed to confirm its effectiveness.

Primary Sjogren syndrome increases the risk of bisphosphonate-related osteonecrosis of the jaw

The risk of bisphosphonate-related osteonecrosis of the jaw (BRONJ) in primary Sjogren syndrome (pSS) has rarely been explored. To explore the association between BRONJ and pSS, we conducted a population-based propensity-score-matched cohort study using Taiwan’s National Health Insurance Research Database, including pSS patients receiving antiosteoporotic therapy and patients without pSS receiving antiosteoporotic therapy. A 1:4 matched-pair cohort based on propensity score was created. The stratified Cox proportional hazards model compared the risk of BRONJ in the pSS and non-pSS groups. In the study, 23,280 pSS patients and 28,712,152 controls were enrolled. After matching, 348 patients with pSS receiving antiosteoporotic drugs and 50,145 without pSS receiving antiosteoporotic drugs were included for analysis. The risk of developing BRONJ was 1.96 times higher in pSS patients compared with non-pSS patients after adjustment for age, sex, and comorbidities. No dose–response effect was observed in the bisphosphonate-treated pSS cohorts, documented as the cumulative defined daily doses of either < 224 or ≥ 224 (hazard ratio [HR]: 2.407, 95% confidence interval [CI] 1.412–7.790; HR: 2.143, 95% CI 1.046–4.393, respectively) increased risk of developing osteonecrosis of the jaw. In conclusion, the risk of BRONJ is significantly higher in patients with pSS compared with the general population.

Biology, pathology, and therapeutic targeting of RAS

RAS was identified as a human oncogene in the early 1980s and subsequently found to be mutated in nearly 30% of all human cancers. More importantly, RAS plays a central role in driving tumor development and maintenance. Despite decades of effort, there remain no FDA approved drugs that directly inhibit RAS. The prevalence of RAS mutations in cancer and the lack of effective anti-RAS therapies stem from RAS' core role in growth factor signaling, unique structural features, and biochemistry. However, recent advances have brought promising new drugs to clinical trials and shone a ray of hope in the field. Here, we will exposit the details of RAS biology that illustrate its key role in cell signaling and shed light on the difficulties in therapeutically targeting RAS. Furthermore, past and current efforts to develop RAS inhibitors will be discussed in depth.

Mitigating osteonecrosis of the jaw (ONJ) through preventive dental care and understanding of risk factors

It is well established that alterations in phosphate metabolism have a profound effect on hard and soft tissues of the oral cavity. The present-day clinical form of osteonecrosis of the jaw (ONJ) was preceded by phosphorus necrosis of the jaw, ca. 1860. The subsequent removal of yellow phosphorus from matches in the early 20th century saw a parallel decline in "phossy jaw" until the early 2000s, when similar reports of unusual jaw bone necrosis began to appear in the literature describing jaw necrosis in patients undergoing chemotherapy and concomitant steroid and bisphosphonate treatment. Today, the potential side effect of ONJ associated with medications that block osteoclast activity (antiresorptive) is well known, though the mechanism remains unclear and the management and outcomes are often unsatisfactory. Much of the existing literature has focused on the continuing concerns of appropriate use of bisphosphonates and other antiresorptive medications, the incomplete or underdeveloped research on ONJ, and the use of drugs with anabolic potential for treatment of osteoporosis. While recognizing that ONJ is a rare occurrence and ONJ-associated medications play an important role in fracture risk reduction in osteoporotic patients, evidence to date suggests that health care providers can lower the risk further by dental evaluations and care prior to initiating antiresorptive therapies and by monitoring dental health during and after treatment. This review describes the current clinical management guidelines for ONJ, the critical role of dental-medical management in mitigating risks, and the current understanding of the effects of predominantly osteoclast-modulating drugs on bone homeostasis.

Protective effects of alendronate in Triton X-100-induced hyperlipidemia in rats

BACKGROUND/AIMS

The aim of the present study was to evaluate the protective effects of alendronate (used in osteoporosis disease) in Triton X-100 (a polyethylene glycol-based non-ionic surfactant)-induced hyperlipidemia in rats.

MATERIALS AND METHODS

The animals were randomized into seven groups receiving different treatments for 21 days, and alendronate was administered (1.5 and 3 mg/kg body weight, per orally (p.o.) by oral gavage). On day 21, the rats were anesthetized and decapitated, blood samples were extracted, and the livers were dissected for various biochemical tests and histopathological examinations.

RESULTS

The biochemical parameters, total cholesterol (TC), triglycerides (TGs), low-density lipoprotein-cholesterol (LDL-C), very low-density lipoprotein-cholesterol (VLDL-C), thiobarbituric acid reactive substances (TBARS), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and atherogenic index, were increased, and reduction in high-density lipoprotein-cholesterol (HDL-C) levels was observed following Triton X-100 treatment to rats. Alendronate (1.5 and 3 mg/kg) produced a dose-dependent reduction in serum TC, VLDL-C, TGs, ratio of TC/HDL-C, ALT, AST, and TBARS. It significantly increased the HDL-C and superoxide dismutase levels but did not cause a significant decrease in serum LDL-C and/or an increase in catalase levels. Histopathological examinations of alendronate showed beneficial effects with lower capsular thickening, slight enlargement of the hepatocytes at the margin, and lower inflammatory cell infiltration.

CONCLUSION

Alendronate showed dose-dependent antihyperlipidemic and hepatoprotective effects. It may serve a dual purpose as anti-osteoporotic and hypolipidemic by reducing blood cholesterol and TG synthesis and offering hepatic protection.

Clinical evidence of the effect of bisphosphonates on pregnancy and the infant

Bisphosphonates (BPs) are potent inhibitors of osteoclast mediated bone resorption. These drugs are widely used in the management of osteoporosis and other diseases, characterized by high bone turnover. The effect of BPs on gestation and lactation, when they are used as therapeutic agents in premenopausal women, is yet unknown. We conducted a detailed literature review and identified the cases of BPs use in young women, as well as, the effects of this therapy on the gestation and the embryo. The published data, regarding the use of BPs in premenopausal women and their effects on the pregnancy outcome, are limited. However, we could identify the outcomes of 40 pregnant women, who had received BPs prior to or during pregnancy, that have been documented in the literature. All women had valid indications to receive BPs for serious bone metabolism conditions. We could not identify any prospective trials, which focus on pregnancy outcomes following after the in-utero exposure to BPs. In total, no serious adverse effects were reported. Problems related to the offspring, such as hypocalcemia and a tendency for low body weight (LBW), were self-resolving. In addition, no serious adverse outcomes were reported for women having completed pregnancy. Nevertheless, follow-up was limited for both outcomes suggesting the necessity of national and international registries.

From Osteoclast Differentiation to Osteonecrosis of the Jaw: Molecular and Clinical Insights

Bone physiology relies on the delicate balance between resorption and formation of its tissue. Bone resorption depends on a process called osteoclastogenesis in which bone-resorbing cells, i.e., osteoclasts, are produced by the differentiation of more undifferentiated progenitors and precursors. This process is governed by two main factors, monocyte-colony stimulating factor (M-CSF) and receptor activator of NFκB ligand (RANKL). While the former exerts a proliferating effect on progenitors/precursors, the latter triggers a differentiation effect on more mature cells of the same lineage. Bone homeostasis requires a perfect space–time coordination of the involved signals. When osteoclastogenesis is poorly balanced with the differentiation of the bone forming counterparts, i.e., osteoblasts, physiological bone remodelling can turn into a pathological state, causing the systematic disruption of bone tissue which results in osteopenia or osteolysis. Examples of these conditions are represented by osteoporosis, Paget’s disease, bone metastasis, and multiple myeloma. Therefore, drugs targeting osteoclastogenesis, such as bisphosphonates and an anti-RANKL monoclonal antibody, have been developed and are currently used in the treatment of such diseases. Despite their demonstrated therapeutic efficacy, these agents are unfortunately not devoid of side effects. In this regard, a condition called osteonecrosis of the jaw (ONJ) has been recently correlated with anti-resorptive therapy. In this review we will address the involvement of osteoclasts and osteoclast-related factors in the pathogenesis of ONJ. It is to be hoped that a better understanding of the biological mechanisms underlying bone remodelling will help in the design a medical therapeutic approach for ONJ as an alternative to surgical procedures.

May zoledronic acid have negative effects on cognition and muscle performance?

BACKGROUND

We aimed to investigate the effects of zoledronic acid treatment on daily living activities, cognitive functions, depression, muscle strength, and performance.

METHODS

The study was conducted retrospectively. Bone mineral densitometry (BMD) values, Katz activities of daily living (ADL), Lawton-Brody instrumental activities of daily living (IADL), mini mental state examination (MMSE), geriatric depression scale (GDS), mini nutritional assessment (MNA), grip strength, and gait speed scores before and 6 months after zoledronic acid administration were compared.

RESULTS

A total of 115 patients were included in the study. There was a significant increase in lumbar total (p < .001), femoral neck (p = .002), and femur total (p = .001) BMD values after zoledronic acid treatment. Significant decrease was found in MMSE (p = .016) and gait speed scores (p = .008) after zoledronic acid treatment, but no significant difference was found in terms of Katz ADL, Lawton-Brody IADL, MNA, GDS, and grip strength (p > .05).

CONCLUSION

Our study indicated that zoledronic acid did not affect daily living activities, depression, and muscle strength. Although we have concluded that cognitive and muscle performance may be adversely affected by zoledronic acid treatment.

Pharmacogenomics of osteonecrosis of the jaw

Osteonecrosis of the jaw (ONJ) is a rare but serious drug induced adverse event, mainly associated with the use of antiresorptive medications, such as intravenous (IV) bisphosphonates (BPs) in cancer patients. In this review, we evaluated all the pharmacogenomic association studies for ONJ published up to December 2018. To date, two SNPs (CYP2C8 rs1934951 and RBMS3 rs17024608) were identified to be associated with ONJ by two genome-wide association studies (GWAS). However, all six subsequent candidate gene studies failed to replicate these results. In addition, six discovery candidate gene studies tried to identify the genetic markers in several genes associated with bone remodeling, bone mineral density, or osteoporosis. After evaluating the results of these 6 studies, none of the SNPs was significantly associated with ONJ. Recently, two whole-exome sequencing (WES) analysis (including one from our group) were performed to identify variants associated with ONJ. So far, only our study successfully replicated discovery result indicating SIRT1 SNP rs7896005 to be associated with ONJ. However, this SNP also did not reach genome-wide significance. The major limitations of these studies include lack of replication phases and limited sample sizes. Even though some studies had larger sample sizes, they recruited healthy individuals as controls, not subjects treated with BPs. We conclude that a GWAS with a larger sample size followed by replication phase will be needed to fully investigate the pharmacogenomic markers of ONJ.

Zoledronic acid blocks the interaction between breast cancer cells and regulatory T-cells

BACKGROUND

Zoledronic acid (ZA), a nitrogen-containing bisphosphonate, inhibits osteoclastogenesis. Emerging evidence suggests that ZA has anti-tumor and anti-metastatic properties for breast cancer cells. In a mouse model of ZA-related osteonecrosis of the jaw, ZA administration was found to suppress regulatory T-cells (Tregs) function. Our previous reports also demonstrated ZA acted as an immune modulator to block Tregs. Manipulation of Tregs represents a new strategy for cancer treatment. However, the relationship among ZA, Tregs, and cancer cells remains unclear. In this study, we investigated the effects of ZA on the interaction of breast cancer cells and Tregs.

METHODS

The anti-tumor effect of ZA on triple negative breast cancer cell lines were validated by XTT, wound healing and apoptosis analysis. A flow cytometry-based assay was used to analyze the immunosuppressive effect of Tregs treated with media conditioned by breast cancer cells, and a transwell assay was used to evaluate the chemotactic migration of Tregs. Differential gene expression profile on MDA-MB-231 treated with ZA (25 μM) was analyzed by. microarrays to describe the molecular basis of actions of ZA for possible direct anti-tumor effects. Enzyme-linked immunosorbent assays and quantitative real-time PCR were used to investigate the effect of ZA on the expression of cytokines/factors by breast cancer cells.

RESULTS

ZA was found to inhibit the proliferation and migration of breast cancer cells. Media conditioned by the MDA-MB-231 cells promoted the expansion, chemotactic migration, and immunosuppressive activity of Tregs, and these effects were attenuated in a dose-dependent manner by ZA treatment, and the attenuation was due to reduced expression of selected breast cancer cell factors (CCL2, CCL5, and IDO).

CONCLUSIONS

ZA can significantly affect the interaction between breast cancer cells and Tregs. Our findings indicate that ZA is a potential therapeutic agent that can be used to reduce cancer aggressiveness by abolishing the supportive role of Tregs.

Geranylgeraniol (GGOH) as a Mevalonate Pathway Activator in the Rescue of Bone Cells Treated with Zoledronic Acid: An In Vitro Study

Bisphosphonates (BPs) are the keystone to treat bone disorders. Despite the great benefits of BPs, medication-related osteonecrosis of the jaw (MRONJ) arouse as a potential side effect. Nitrogen-containing BPs (N-BPs) as zoledronate (ZA) act by the inhibition of specific enzymes of the mevalonate pathway resulting in altering protein prenylation which is required for the posttranslational maturation of the small GTP-binding proteins. Geranylgeraniol (GGOH) is an intermediate product in the mevalonate pathway having positive effects on different cell types treated with BPs by salvaging protein prenylation improving cell viability and proliferation in tissue regeneration, thus overcoming N-BP-induced apoptosis. Here, the effect of different concentrations of zoledronate (ZA) on the bone cells has been investigated by cell viability assay, live/dead staining, and western blot to understand if GGOH was able to rescue bone cells and levels of statistical significance were indicated at ^∗P < 0.05, ^∗∗P < 0.01, ^∗∗∗P < 0.001, and ^∗∗∗∗P < 0.0001. Although the high concentration of ZA had significantly decreased the cell viability in the bone cells, GGOH reversed the action of ZA on the cells while at very high concentration; it caused severe reduction in the cell viability. Rap1A, a member of the GTPases family, was expressed in the negative controls but was absent in cells treated with high concentrations of ZA. The addition of GGOH had increased the expression of Rap1A up to a certain limit. The experiments proved that ZA acts directly on the mevalonate pathway and protein prenylation and that GGOH could be applied as a future local therapy to MRONJ.

Anabolic and antiresorptive actions of locally delivered bisphosphonates for bone repair: A review

During the last decades, several research groups have used bisphosphonates for local application to counteract secondary bone resorption after bone grafting, to improve implant fixation or to control bone resorption caused by bone morphogenetic proteins (BMPs). We focused on zoledronate (a bisphosphonate) due to its greater antiresorptive potential over other bisphosphonates. Recently, it has become obvious that the carrier is of importance to modulate the concentration and elution profile of the zoledronic acid locally. Incorporating one fifth of the recommended systemic dose of zoledronate with different apatite matrices and types of bone defects has been shown to enhance bone regeneration significantly in vivo. We expect the local delivery of zoledronate to overcome the limitations and side effects associated with systemic usage; however, we need to know more about the bioavailability and the biological effects. The local use of BMP-2 and zoledronate as a combination has a proven additional effect on bone regeneration. This review focuses primarily on the local use of zoledronate alone, or in combination with bone anabolic factors, in various preclinical models mimicking different orthopaedic conditions.

Cite this article: I. Qayoom, D. B. Raina, A. Širka, Š. Tarasevičius, M. Tägil, A. Kumar, L. Lidgren. Anabolic and antiresorptive actions of locally delivered bisphosphonates for bone repair: A review. Bone Joint Res 2018;7:548–560. DOI: 10.1302/2046-3758.710.BJR-2018-0015.R2.

Zoledronic acid induces micronuclei formation, mitochondrial-mediated apoptosis and cytostasis in kidney cells

AIMS

Zoledronic acid (ZA), a FDA approved drug has used widely in the treatment of bone metastasis complications, has been linked to renal toxicity with unclear mechanism. The present study is aimed at investigating the genotoxic and cytotoxic effects of ZA in renal epithelial cells.

MAIN METHODS

The genotoxic effect of ZA in Vero and MDCK cells determined by cytokinesis block micronucleus (CBMN) assay. The cytotoxic effect assessed by analysing cell cycle profile, cell death and mitochondrial membrane potential by flow cytometry using propidium iodide, AnnexinV-FITC/PI and JC1 dye staining, respectively, BAX and Bcl-2 expression by Western blotting and caspase activity by spectrofluorimetry.

KEY FINDINGS

The cytotoxic effect of ZA based on MTT assay revealed variable sensitivities of Vero and MDCK cells, with IC₅₀ values of 7.41 and 109.58 μM, respectively. The CBMN assay has shown prominent dose-dependent (IC_10-50) induction of micronuclei formation in both cells, indicating ZA's clastogenic and aneugenic potential. Further, the ZA treatment led the cells to apoptosis, evident from dose-dependent increase in the percentage of cells in subG1 phase and display of membranous phosphatidylserine translocation. Studies also confirmed apoptosis through mitochondria, evident from the prominent increase in BAX/Bcl-2 ratio, mitochondrial membrane depolarization and caspase-3/7 activity. In addition, ZA reduces cytokinetic activity of renal cells, evident from dose-wise lowered replicative indices.

SIGNIFICANCE

The study depict ZA's potential genotoxic effect along with cytotoxic effect in renal epithelial cells, could be key factors for the development of renal complications associated with it, which prompts renal safety measures in lieu with ZA usage.

Bisphosphonate-related osteonecrosis of the jaw: a mechanobiology perspective

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a dramatic disintegration of the jaw that affects patients treated with bisphosphonates (BPs) for diseases characterized by bone loss. These diseases are often metastasizing cancers (like multiple myeloma, breast cancer and prostate cancer (Aragon-Ching et al., 2009)) as well as osteoporosis. BRONJ is incompletely understood, although it is believed to arise from a defect in bone remodeling—the intricate process by which sensory osteocytes signal to osteoclasts and osteoblasts to resorb and form bone in response to stimuli. Further, tooth extraction and infection have been overwhelmingly linked to BRONJ (Ikebe, 2013). Because bone cells are highly networked, the importance of multicellular interactions and mechanotransduction during the onset of these risk factors cannot be overstated. As such, this perspective addresses current research on the effects of BPs, mechanical load and inflammation on bone remodeling and on development of BRONJ. Our investigation has led us to conclude that improved in vitro systems capable of adequately recapitulating multicellular communication and incorporating effects of osteocyte mechanosensing on bone resorption and formation are needed to elucidate the mechanism(s) by which BRONJ ensues.

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Current research on cofactors implicated in BRONJ is reviewed.

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BPs, load and inflammation work in tandem to contribute to BRONJ.

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Effects of cofactors on remodeling in the oral cavity are poorly understood.

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Osteocytes' ability to sense and respond to cofactors is likely central to BRONJ.

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Research is limited by a lack of multicellular systems integrating mechanosensing.

Smart, programmable and responsive injectable hydrogels for controlled release of cargo osteoporosis drugs

Easy-to-prepare drug delivery systems, based on smart, silica gels have been synthesized, characterized, and studied as hosts in the controlled release of bisphosphonates. They exhibit variable release rates and final % release, depending on the nature of bisphosphonate (side-chain length, hydro-philicity/-phobicity, water-solubility), cations present, pH and temperature. These gels are robust, injectable, re-loadable and re-usable.

Systemic drugs that influence titanium implant osseointegration

Titanium implants are widely used on an increasing number of patients in orthopedic and dental medicine. Despite the good survival rates of these implants, failures that lead to important socio-economic consequences still exist. Recently, research aimed at improving implant fixation, a process called osseointegration, has focused on a new, innovative field: systemic delivery of drugs. Following implant fixation, patients receive systemic drugs that could either impair or enhance osseointegration; these drugs include anabolic and anti-catabolic bone-acting agents in addition to new treatments. Anabolic bone-acting agents include parathyroid hormone (PTH) peptides, simvastatin, prostaglandin EP4 receptor antagonist, vitamin D and strontium ranelate; anti-catabolic bone-acting agents include compounds like calcitonin, biphosphonates, RANK/RANKL/OPG system and selective estrogen receptor modulators (SERM). Examples of the new therapies include DKK1- and anti-sclerostin antibodies. All classes of treatments have proven to possess positive impacts such as an increase in bone mineral density and on osseointegration. In order to prevent complications from occurring after surgery, some post-operative systemic drugs are administered; these can show an impairment in the osseointegration process. These include nonsteroidal anti-inflammatory drugs, proton pump inhibitors and selective serotonin reuptake inhibitors. The effects of aspirin, acetaminophen, opioids, adjuvants, anticoagulants and antibiotics in implant fixations are not fully understood, but studies are being carried out to investigate potential ramifications. It is currently accepted that systemic pharmacological agents can either enhance or impair implant osseointegration; therefore, proper drug selection is essential. This review aims to discuss the varying effects of three different classes of treatments on improving this process.

Zoledronic acid suppresses transforming growth factor-β-induced fibrogenesis by human gingival fibroblasts

Bisphosphonates (BPs) are analogues of pyro-phosphate that are known to prevent bone resorption by inhibiting osteoclast activity. Nitrogen-containing BPs, such as zoledronic acid (ZA), are widely used in the treatment of osteoporosis and bone metastasis. However, despite having benefits, ZA has been reported to induce BP-related osteonecrosis of the jaw (BRONJ) in cancer patients. The molecular pathological mechanisms responsible for the development of BRONJ, including necrotic bone exposure after tooth extraction, remain to be elucidated. In this study, we examined the effects of ZA on the transforming growth factor-β (TGF-β)-induced myofibroblast (MF) differentiation of human gingival fibroblasts (hGFs) and the migratory activity of hGFs, which are important for wound closure by fibrous tissue formation. The ZA maximum concentration in serum (Cmax) was found to be approximately 1.47 µM, which clinically, is found after the intravenous administration of 4 mg ZA, and ZA at this dose is considered appropriate for the treatment of cancer bone metastasis or bone diseases, such as Erdheim-Chester disease. At Cmax, ZA significantly suppressed i) the TGF-β-induced promotion of cell viability, ii) the TGF-β-induced expression of MF markers such as α-smooth muscle actin (α-SMA) and type I collagen, iii) the TGF-β-induced migratory activity of hGFs and iv) the expression level of TGF-β type I receptor on the surfaces of hGFs, as well as the TGF-β-induced phosphorylation of Smad2/3. Thus, ZA suppresses TGF-β-induced fibrous tissue formation by hGFs, possibly through the inhibition of Smad-dependent signal transduction. Our findings partly elucidate the molecular mechanisms underlying BRONJ and may prove to be beneficial to the identification of drug targets for the treatment of this symptom at the molecular level.

Serotonergic Mechanisms Regulating the GI Tract: Experimental Evidence and Therapeutic Relevance

Serotonin (5-hydroxytryptamine; 5-HT) is best known as a neurotransmitter critical for central nervous system (CNS) development and function. 95% of the body's serotonin, however, is produced in the intestine where it has been increasingly recognized for its hormonal, autocrine, paracrine, and endocrine actions. This chapter provides the most current knowledge of the critical autocrine and paracrine roles of 5-HT in intestinal motility and inflammation as well as its function as a hormone in osteocyte homeostasis. Therapeutic applications in each of these areas are also discussed.

A polymorphism at the translation start site of the vitamin D receptor gene is associated with the response to anti-osteoporotic therapy in postmenopausal women from southern Italy

The present study investigated the effect of two single nucleotide polymorphisms (SNPs) of the vitamin D receptor (VDR) gene, rs1544410 A/G and rs2228570 C/T, in modulating bone mineral density (BMD) and the response to treatment with bisphosphonates or strontium ranelate in postmenopausal osteoporosis (PMO). Four hundred eighteen postmenopausal women from Southern Italy treated with bisphosphonates or strontium ranelate for three years were enrolled and stratified according to their genotype. Changes in BMD were expressed as the delta t-score (Δt-score). Allelic frequencies for rs1544410 A/GSNP were 11.2% AA, 50.0% GA and 38.8% GG; for rs2228570 C/TSNP were 54.8% CC, 39.5% TC and 5.7% TT. TT carriers showed a lower t-score than TC and CC (both p < 0.02) genotypes and were more responsive to the therapy when compared to both TC (p < 0.02) and CC (p < 0.05) carriers. Specifically, TT carriers receiving alendronate demonstrated a significant improvement of the Δt-score compared to TC and CC (both p < 0.0001) carriers. After adjustment for confounders, the Δt-score showed evidence of a statistically significant positive association with TT in all treatments considered. Therapy response was independent of rs1544410 A/G SNP; instead, rs2228570 C/TSNP was associated with a better response to antiresorptive treatment, thus suggesting that the therapy for PMO should be personalized.

Zoledronate inhibits receptor activator of nuclear factor kappa-B ligand-induced osteoclast differentiation via suppression of expression of nuclear factor of activated T-cell c1 and carbonic anhydrase 2

Bisphosphonates (BPs) are widely used in the prevention of skeletal-related events (SRE), including osteoporosis, skeletal metastases of malignant tumours, and multiple myeloma. Osteonecrosis of the jaw (ONJ) is frequently reported as a major adverse effect induced by BP treatment. The receptor activator of the nuclear factor kappa-B ligand (RANKL) inhibitor, denosumab, has recently been used to prevent SRE, but the frequency of ONJ induced by denosumab is similar to that by BPs. This finding suggests that the inhibition of RANKL-mediated osteoclastogenesis may have a close relationship with the occurrence of ONJ. We therefore investigated the expression status of RANKL-inducible genes in zoledronate-treated mouse osteoclast precursor cells. The molecular targets of zoledronate in the RANKL signal pathway and additional factors associated with osteoclastogenesis were analysed by genome-wide screening. Microarray analysis identified that among 31 genes on 44 entities of RANKL-inducible genes, the mRNA expression level of two genes, i.e., nuclear factor of activated T-cells c1 (NFATc1) and carbonic anhydrase 2 (CAII), was decreased in zoledronate-treated cells. Subsequent analyses verified that these two genes were significantly silenced by zoledronate treatment and that their expression was restored following inhibition of zoledronate action by geranylgeraniol. Zoledronate inhibited RANKL-induced osteoclast differentiation by suppression of NFATc1 and CAII gene expression. Our results suggest that these genes might be common targets for zoledronate and denosumab in the mechanism underlying RANKL-induced osteoclast differentiation. A clear understanding of the common molecular mechanisms of bone-remodelling agents is thus essential for prevention of ONJ.

Modulating effect of matrices with calcium phosphate coating on cytotoxicity of strontium ranelate and ibandronic acid in vitro

Strontium ranelate (29 μg/ml) and ibandronic acid (50 μM) produced a cytotoxic effect on rat bone marrow myelokaryocytes in vitro. Strontium ranelate increased the number of myelokaryocytes with signs of necrosis, ibandronic acid increased the number of apoptotic and necrotic cells in the 9-day 2D culture of bone marrow cells on the plastic surface of the wells of culture plates. Co-culturing of the bone marrow with 3D matrices with microarc calcium phosphate coating that simulated bone mineral matrix increased intracellular ROS concentration, but abolished the cytotoxic effect of these drugs.

PharmGKB: the Pharmacogenomics Knowledge Base

The Pharmacogenomics Knowledge Base, PharmGKB, is an interactive tool for researchers investigating how genetic variation affects drug response. The PharmGKB Web site, http://www.pharmgkb.org , displays genotype, molecular, and clinical knowledge integrated into pathway representations and Very Important Pharmacogene (VIP) summaries with links to additional external resources. Users can search and browse the knowledgebase by genes, variants, drugs, diseases, and pathways. Registration is free to the entire research community, but subject to agreement to use for research purposes only and not to redistribute. Registered users can access and download data to aid in the design of future pharmacogenetics and pharmacogenomics studies.

The effect of alendronate on proteome of hepatocellular carcinoma cell lines

Cancer is a life threatening disorder effecting 11 million people worldwide annually. Among various types of cancers, Hepatocellular carcinoma (HCC) has a higher rate of mortality and is the fifth leading cause of cancer related deaths around the world. Many chemotherapeutic drugs have been used for the treatment of HCC with many side effects. These drugs are inhibitors of different cell regulatory pathways. Mevalonate (MVA) pathway is an important cellular cascade vital for cell growth. A variety of inhibitors of MVA pathway have been reported for their anticancerous activity. Bisphosphonates (BPs) are members of a family involved in the treatment of skeletal complications. In recent years, their anticancer potential has been highlighted. Current study focuses on exploring the effects of alendronate (ALN), a nitrogen containing BP, on hepatocellular carcinoma cell line using genomic and proteomics approach. Our results identified ten differentially expressed proteins, of which five were up regulated and five were down regulated in ALN treated cells. Furthermore, we also performed gene expression analysis in treated and control cell lines. The study may help in understanding the molecular mechanism involved in antitumor activity of ALN, identification of possible novel drug targets, and designing new therapeutic strategies for HCC.

High-level copy number gains of established and potential drug target genes in gastric cancer as a lead for treatment development and selection

PURPOSE

The overall survival rate of patients with advanced gastric cancer is poor. Therefore, there is an urgent need for new treatment options for these patients. The identification of drug target genes located on DNA regions exhibiting high-level copy number gains (CNG) may be an effective approach, as has e.g. previously been shown for HER2. The aim of the present study was to identify putative drug targets in patients with gastric cancer by applying this strategy.

METHODS

Genome-wide array comparative genomic hybridization (array CGH) data available from 183 primary gastric cancer samples were analyzed through Ingenuity Pathway Analysis (IPA) to assess whether any established or potential anticancer drug target genes showed high-level CNG, including focal amplifications.

RESULTS

A total of 147 high-level gained regions were identified in the gastric cancer samples, harboring 167 genes that had previously been annotated as drug target genes. Thirty (18 %) of these genes showed high-level gains in at least 2 % of the tumors. The identified drug target genes included those for drugs known to be active in advanced (gastric) cancer, targets for targeted therapies in clinical development, as well as targets for drugs currently used for other indications but of potential interest for anticancer treatment. In addition, 12 potential drug target genes were identified, including genes involved in growth factor signaling and cell cycle regulation.

CONCLUSION

The majority of gastric cancers carried one or more high-level CNGs or focal amplifications encompassing putative drug target genes. A number of the associated drugs are currently not being considered for treatment of gastric cancer. Based on these results we hypothesize that DNA copy number profiling may be a useful tool to identify new drug targets and to guide individualized treatment strategies in patients with gastric cancer.

Pharmacogenetics of osteoporosis: towards novel theranostics for personalized medicine?

Osteoporosis is a complex multifactorial bone disorder with a strong genetic basis. It is the most common, severe, progressive skeletal illness that has been increasing, particularly in developed countries. Osteoporosis will no doubt constitute a serious clinical burden in healthcare management in the coming decades. The genetics of osteoporosis should be analyzed from both the disease susceptibility and the pharmacogenetic treatment perspectives. The former has been widely studied and discussed, while the latter still requires much more information and research. This article provides a synthesis of the literature on the genetics of osteoporosis and an update on progress made in pharmacogenetics of osteoporosis in recent years, specifically regarding the new molecular targets for antiresorptive drugs. In-depth translation of osteoporosis pharmacogenetics approaches to clinical practice demands a new vision grounded on the concept of "theranostics," that is, the integration of diagnostics for both disease susceptibility testing, as well as for prediction of health intervention outcomes. In essence, theranostics signals a broadening in the scope of inquiry in diagnostics medicine. The upcoming wave of theranostics medicine also suggests more distributed forms of science and knowledge production, both by experts and end-users of scientific products. Both the diagnosis and personalized treatment of osteoporosis could conceivably benefit from the emerging postgenomics field of theranostics.

Genomewide pharmacogenetics of bisphosphonate-induced osteonecrosis of the jaw: the role of RBMS3

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a serious adverse drug reaction. We conducted a genomewide association study to search for genetic variants with a large effect size that increase the risk for BRONJ.

METHODS

We ascertained BRONJ cases according to the diagnostic criteria of the American Association of Oral and Maxillofacial Surgeons. We genotyped cases and a set of treatment-matched controls using Illumina Human Omni Express 12v1 chip (733,202 markers). To maximize the power of the study, we expanded the initial control set by including population and treatment-tolerant controls from publicly available sources. Imputation at the whole-genome level was performed to increase the number of single nucleotide polymorphisms (SNPs) investigated. Tests of association were carried out by logistic regression, adjusting for population structure. We also examined a list of candidate genes comprising genes potentially involved in the pathogenesis of BRONJ and genes related to drug absorption, distribution, metabolism, and excretion.

RESULTS

Based on principal component analysis, we initially analyzed 30 white cases and 17 treatment-tolerant controls. We subsequently expanded the control set to include 60 genetically matched controls per case. Association testing identified a significant marker in the RBMS3 gene, rs17024608 (p-value < 7 × 10(-8)); individuals positive for the SNP were 5.8× more likely to develop BRONJ (odds ratio, 5.8; 95% confidence interval, 3.1-11.1). Candidate gene analysis further identified SNPs in IGFBP7 and ABCC4 as potentially implicated in BRONJ risk.

CONCLUSION

Our findings suggest that genetic susceptibility plays a role in the pathophysiology of BRONJ, with RBMS3 having a significant effect in the risk.