Ibandronate uptake in the jaw is similar to long bones and vertebrae in the rat

Medication-related osteonecrosis of the jaw (MRONJ) and eNOS Polymorphisms in multiple myeloma patients: a single center experience

Background

Multiple myeloma (MM) constitutes approximately 10% of hematological malignancies. Bisphosphonates have established themselves in solid organ metastasis and multiple myeloma lytic bone lesions by inhibiting osteoclast activation. Medication-related osteonecrosis of the jaw (MRONJ) emerges as an important complication. Investigating host-based factors, and developing personal risk factors gain importance in the development mechanism of MRONJ. We aimed to reveal the different genotype polymorphisms, and clinical effects of eNOS in patients with a diagnosis of MRONJ in MM patients.

Methods

Medical records and blood samples were collected from 60 MRONJ patients with MM and 60 healthy controls. Inclusion criteria was having an exposed maxillofacial bone for more than eight weeks, a history of bisphosphonates, and no history of radiation therapy for the jaws. eNOS G894T and intron 4 VNTR were calculated by polymerase chain reaction and/or restriction fragment length polymorphism.

Results

eNOS G894T and VNTR genotypes and alleles were compared statistically with the healthy control group. There was no significant difference between the two groups. In comparison between G894T and clinical parameters, aphthous stomatitis was more common in TT genotype, while DMFT > 3 was more common in TG-GG genotype (p = 0.035, 0.023).

Conclusions

eNOS induces osteogenesis in bone metabolism, with its regulatory effects on bone remodeling and also NO induced angiogenesis takes place indirectly with its protective effect on endothelial functions. We see that these polymorphisms affecting the entire process of bone remodeling and angiogenesis, especially mucosal damage, which is the triggering factor of MRONJ pathology, have been revealed in the MM patient group. Considering the MRONJ initiating factors, it is necessary to emphasize the importance of our study results. It should be seen as an important step for new studies towards MRONJ and its treatment.

Pathogenesis of medication-related osteonecrosis of the jaw: a comparative study of in vivo and in vitro trials

Objective This study was performed to determine whether the results of prevailing in vivo and in vitro studies offer a reliable model for investigation of medication-related osteonecrosis of the jaw (MRONJ). Methods Embase, Medline, and the Cochrane Library were searched for articles published from September 2003 to June 2017 involving experimental approaches to the pathogenesis of MRONJ. In vivo and in vitro trials were analyzed with respect to the scientific question, study design, methodology, and results. Results Of 139 studies, 87, 46, and 6 conducted in vivo, in vitro, and both in vivo and in vitro experiments, respectively. Rats, mice, dogs, minipigs, sheep, and rabbits were the preferred animal models used. Osteoblasts, osteoclasts, fibroblasts, keratinocytes, macrophages, and human umbilical vein endothelial cells were the preferred cell types. Zoledronate, alendronate, ibandronate, and risedronate were the most frequent bisphosphonates used. MRONJ was most reliably induced in minipigs because of the close relationship with human bone physiology. In vitro studies showed that reduced viability, growth, and migration of cells in the bone and soft tissues were causative for MRONJ. Other than exposed jawbone after tooth extraction, no reliable cofactors were found. Conclusion The minipig is the most suitable animal model for MRONJ.

Changes in dimension of neurovascular canals in the mandible and maxilla: A radiographic finding in patients diagnosed with MRONJ

Background

The aim of this retrospective study was to compare the morphological features of neurovascular canals and foramina of patients with medication-related osteonecrosis of the jaws (MRONJ) and healthy individuals by using cone beam computed tomography (CBCT).

Material and Methods

The CBCT images of 58 patients under bisphosphonate therapy diagnosed with MRONJ and age gender- matched controls were retrospectively evaluated. The diameter of mandibular and nasopalatine canal and mandibular, mental and lingual foramina were measured on several sections of CBCT. The value of mental index (MI) and panoramic mandibular index (PMI) were also assessed.

Results

The mean value of diametric measurements for all neurovascular canals and foramina in MRONJ patients were narrower than controls. Left mandibular foramen was the most affected area (p<0.001). There were significantly difference in all measurements of mental foramen, lingual foramen and mandibular incisive canal between two groups (p<0.05). PMI of MRONJ subjects were also significantly differences in both sides (p<0.05).

Conclusions

In MRONJ patient, neurovascular canals and foramina are affected due to the alterations in bone remodeling. Therefore, the diametric measurement of neurovascular canals and assessment of MI and PMI on CBCT, is a potentially useful method for detection of early changes associated with bisphosphonate therapy and for predict areas where new necrosis may occur.

Key words:Bisphosphonate, MRONJ, CBCT, neurovascular canals, PMI.

In Vitro Investigation of the Antimicrobial Effect of Three Bisphosphonates Against Different Bacterial Strains

PURPOSE

Since the first descriptions of medication-related osteonecrosis of the jaw (MRONJ) in 2003, the pathogenesis has remained unanswered. Recent histomorphometric studies have found several microorganisms, including Actinomyces, Bacillus, Fusobacterium, Staphylococcus, Streptococcus, Selenomonas, Treponema, and Candida albicans in necrotic bone. Polymerase chain reaction studies have recently confirmed the occurrence of 48 genera. Only a few studies have examined the antimicrobial effect of bisphosphonates (BPs). The influence of bacterial growth on the etiology remains unclear. The aim of the present study was the in vitro investigation of the antimicrobial effect of 3 BPs against different bacterial strains.

MATERIALS AND METHODS

The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 48 strains from 40 species were determined in microdilution assays against pamidronic, ibandronic, and zoledronic acid.

RESULTS

Growth of gram-positive oral microbiota, which account for most microorganisms in MRONJ, was present for 2 of 22 species; 6 of 26 gram-negative species and 9 of 13 anaerobes were inhibited. The MIC values were compared with the BP bone concentrations from previous reports. Of the 48 strains, 9 had an MIC or MBC less than the bone concentrations.

CONCLUSIONS

The results of the present study have demonstrated that BPs have an inhibitory effect on selected bacterial species and might inhibit the growth of some relevant pathogens in osteonecrosis. However, most of the species tested were unaffected at the concentration levels assumed present in the human jawbone. The clinical relevance of these in vitro data will better be clarified with reliable data on the BP concentrations in the human jawbone. The present study has provided a first approach toward the assessment of the interaction of oral bacteria and BPs.

New insights into human farnesyl pyrophosphate synthase inhibition by second-generation bisphosphonate drugs

Pamidronate, alendronate, APHBP and neridronate are a group of drugs, known as second-generation bisphosphonates (2G-BPs), commonly used in the treatment of bone-resorption disorders, and recently their use has been related to some collateral side effects. The therapeutic activity of 2G-BPs is related to the inhibition of the human Farnesyl Pyrophosphate Synthase (hFPPS). Available inhibitory activity values show that 2G-BPs act time-dependently, showing big differences in their initial inhibitory activities but similar final IC₅₀ values. However, there is a lack of information explaining this similar final inhibitory potency. Although different residues have been identified in the stabilization of the R₂ side chain of 2G-BPs into the active site, similar free binding energies were obtained that highlighted a similar stability of the ternary complexes, which in turns justified the similar IC₅₀ values reported. Free binding energy calculations also demonstrated that the union of 2G-BPs to the active site were 38 to 54 kcal mol^-1 energetically more favourable than the union of the natural substrate, which is the basis of the inhibition potency of the hFPPS activity.

Bone-site-specific responses to zoledronic acid

OBJECTIVES

Bisphosphonates are widely used to treat bone diseases such as osteoporosis. However, they may cause osteonecrosis of the jaw. Here, we investigated whether in vivo exposure to bisphosphonates has a different effect on long bone and jaw osteoclasts, and on the turnover of these different bones.

MATERIALS AND METHODS

Zoledronic acid (0.5 mg kg^-1 weekly) was administered intraperitoneally to 3-month-old female mice for up to 6 months. The effects on the number of osteoclasts, bone mineralization and bone formation were measured in the long bones and in the jaw.

RESULTS

Long-term treatment with zoledronic acid reduced the number of jaw bone marrow cells, without affecting the number of long bone marrow cells. Zoledronic acid treatment did not affect the number of osteoclasts in vivo. Yet, the bisphosphonate increased bone volume and mineral density of both long bone and jaw. Interestingly, 6 months of treatment suppressed bone formation in the long bones without affecting the jaw. Unexpectedly, we showed that bisphosphonates can cause molar root resorption, mediated by active osteoclasts.

CONCLUSIONS

Our findings provide more insight into bone-site-specific effects of bisphosphonates and into the aetiology of osteonecrosis of the jaw. We demonstrated that bisphosphonates can stimulate osteoclast activity at the molar roots.

Is GERD a Factor in Osteonecrosis of the Jaw? Evidence of Pathology Linked to G6PD Deficiency and Sulfomucins

Osteonecrosis of the jaw (ONJ), a rare side effect of bisphosphonate therapy, is a debilitating disorder with a poorly understood etiology. FDA's Adverse Event Reporting System (FAERS) provides the opportunity to investigate this disease. Our goals were to analyze FAERS data to discover possible relationships between ONJ and specific conditions and drugs and then to consult the scientific literature to deduce biological explanations. Our methodology revealed a very strong association between gastroesophageal reflux and bisphosphonate-induced ONJ, suggesting acidosis as a key factor. Overgrowth of acidophilic species, particularly Streptococcus mutans, in the oral microbiome in the context of insufficient acid buffering due to impaired salivary glands maintains the low pH that sustains damage to the mucosa. Significant associations between ONJ and adrenal insufficiency, vitamin C deficiency, and Sjögren's syndrome were found. Glucose 6 phosphate dehydrogenase (G6PD) deficiency can explain much of the pathology. An inability to maintain vitamin C and other antioxidants in the reduced form leads to vascular oxidative damage and impaired adrenal function. Thus, pathogen-induced acidosis, hypoxia, and insufficient antioxidant defenses together induce ONJ. G6PD deficiency and adrenal insufficiency are underlying factors. Impaired supply of adrenal-derived sulfated sterols such as DHEA sulfate may drive the disease process.

Human farnesyl pyrophosphate synthase inhibition by nitrogen bisphosphonates: a 3D-QSAR study

We report the results of a comparative molecular field analysis and comparative molecular similarity index analysis of the human farnesyl pyrophosphate synthase (FPPS) inhibition by nitrogen bisphosphonates (NBPs) taking into account their time-dependent inhibition efficacies. The 3D-QSAR models obtained provide steric, electrostatic and hydrophobic contour maps consistent with the interactions into the active site of human FPPS observed in available crystallographic structures. Furthermore, the 3D-QSAR models obtained provide accurately IC50 values of the NBPs of the training set. The predictive ability of these 3D-QSAR models was found to rely on the choice of biologically active conformations of the target molecules and on a careful examination of the protonation status of the NBPs in the training set. The best models obtained can be useful to predict biological values of a high number of NBPs that have been used for the treatment of different diseases as potential inhibitors of the activity of the FPPS enzyme.

Short-term effect of zoledronic acid upon fracture resistance of the mandibular condyle and femoral head in an animal model

Objective: The aim of this study was to compare the effects in terms of resistance to fracture of the mandibular condyle and femoral head following different doses of zoledronic acid in an animal model. Study design: A total of 80 adult male Sprague-Dawley rats were included in a prospective randomized study. The animals were randomly divided into four groups of 20 rats each. Group 1 (control) received sterile saline solution, while groups 2, 3 and 4 received a accumulated dose of 0.2 mg, 0.4 mg and 0.6 mg of zoledronic acid, respectively. The animals were sacrificed 28 days after the last dose, and the right hemimandible and the right femur were removed. The fracture strength was measured (in Newtons) with a universal test machine using a 1 kN load connected to a metal rod with one end angled at 30 degrees. The cross-head speed was 1 mm/min. Later, the specimens were observed under a scanning electron microscope with backscattered electron imaging (SEM-BSE). At last, chemical analysis and elemental mapping of the mineral bone composition were generated using a microanalytical system based on energy-dispersive and X-ray spectrometry (EDX). Results: A total of 160 fracture tests were performed. The fracture resistance increased in mandible and femur with a higher accumulated dose of zoledronic acid. Statistically significant differences were recorded versus the controls with all the studies groups. The chemical analysis in mandible showed a significantly increased of calcium and phosphorous to compare the control with all of the study groups; however, in femur no statistically significant differences between the four study groups were observed. Conclusions: The administration of bisphosphonates increases the fracture resistance in mandible and femur.

Key words:Zoledronic acid, bisphosphonates, animal experimentation, fracture test.

Zoledronate effects on systemic and jaw osteopenias in ovariectomized periostin-deficient mice

Osteoporosis and periodontal disease (PD) are frequently associated in the elderly, both concurring to the loss of jaw alveolar bone and finally of teeth. Bisphosphonates improve alveolar bone loss but have also been associated with osteonecrosis of the jaw (ONJ), particularly using oncological doses of zoledronate. The effects and therapeutic margin of zoledronate on jaw bone therefore remain uncertain. We reappraised the efficacy and safety of Zoledronate (Zol) in ovariectomized (OVX) periostin (Postn)-deficient mice, a unique genetic model of systemic and jaw osteopenia. Compared to vehicle, Zol 1M (100 µg/kg/month) and Zol 1W (100 µg/kg/week) for 3 months both significantly improved femur BMD, trabecular bone volume on tissue volume (BV/TV) and cortical bone volume in both OVX Postn^+/+ and Postn^−/− (all p<0.01). Zol 1M and Zol 1W also improved jaw alveolar and basal BV/TV, although the highest dose (Zol 1W) was less efficient, particularly in Postn^−/−. Zol decreased osteoclast number and bone formation indices, i.e. MAR, MPm/BPm and BFR, independently in Postn^−/− and Postn^+/+, both in the long bones and in deep jaw alveolar bone, without differences between Zol doses. Zol 1M and Zol 1W did not reactivate inflammation nor increase fibrous tissue in the bone marrow of the jaw, whereas the distance between the root and the enamel of the incisor (DRI) remained high in Postn^−/− vs Postn^+/+ confirming latent inflammation and lack of crestal alveolar bone. Zol 1W and Zol 1M decreased osteocyte numbers in Postn^−/− and Postn^+/+ mandible, and Zol 1W increased the number of empty lacunae in Postn^−/−, however no areas of necrotic bone were observed. These results demonstrate that zoledronate improves jaw osteopenia and suggest that in Postn^−/− mice, zoledronate is not sufficient to induce bone necrosis.

Osteonecrosis of the jaw onset times are based on the route of bisphosphonate therapy

PURPOSE

Osteonecrosis of the jaw (ONJ) has been reported to be associated with patients receiving bisphosphonate (BP) therapy. There are many reports that suggest that the time of exposure to BPs is a significant risk factor for ONJ and that the greatest risk occurs after dentoalveolar surgery. The aim of this study was to retrospectively investigate the duration of BP therapy and related events before the onset of ONJ based on an intravenous (IV) or oral route of administration.

MATERIALS AND METHODS

We conducted a retrospective cohort study of patients referred to our institution to identify the onset of ONJ based on the exposure to BP therapy and associated triggers (ie, dentoalveolar surgery or spontaneous occurrence) based on the route of BP administration. Demographic data (ie, age, gender, and race), medical diagnosis related to BP therapy, and information as to whether the BP therapy was continued at the time of ONJ diagnosis were also collected.

RESULTS

We reviewed the records for 114 patients with a history of ONJ. We divided patient cohorts by route of BP administration, with 76 patients having a history of IV BP therapy and 38 patients having a history of oral BP therapy. The overall onset of ONJ was earlier in the IV BP group (median, 3 years) compared with the oral BP group (median, 5 years). There was no statistical difference in the duration to occurrence of ONJ associated with dental extraction compared with spontaneous occurrence for both the IV and oral BP groups.

CONCLUSIONS

The median onset of ONJ for patients undergoing IV BP therapy occurs earlier than the median onset for patients undergoing oral BP therapy, and there was no difference in onset occurring spontaneously and after dental extraction. The significance of these findings suggests that patients who receive IV BP therapy should be closely evaluated after the initiation of BP therapy. The lack of evidence suggesting greater onset after dental extraction may provide clinical support for dentoalveolar surgery that is indicated for patients with a history of BP therapy. Research focusing on the clinical circumstances and physiologic events during early antiresorptive therapy may provide insight as to the critical risk factors.

An aromatase polymorphism (g.132810C>T) predicts risk of bisphosphonate-related osteonecrosis of the jaw

Background: Bisphosphonate (BP)-related osteonecrosis of the jaw (ONJ) is an unpredictable, debilitating adverse effect. Recently, genetic polymorphisms have arisen as promising tools to identify patients with a higher risk of drug-related adverse events. Aim: We aimed to examine the association between the aromatase polymorphism g.132810C>T, and the estrogen receptor polymorphisms g.156705T>C and g.156751A>G, and the risk of BP-related ONJ. Methods: Eighty-three subjects were included in the study. A clinical and radiological examination was conducted on oncologic subjects treated with zoledronic acid. Subjects with histologically confirmed ONJ were included in the test group (n = 30) whereas subjects with good oral health were included in control group (n = 53). Aromatase and estrogen receptor polymorphisms from blood samples were analyzed. Results: The aromatase g.132810C>T polymorphism displayed an over-representation of the TT genotype in the test group (36.67 vs 16.98%; p < 0.05). There was no significant difference in either estrogen receptor polymorphism genotype frequency between the test and control groups. Conclusion: Our data suggest a role for the g.132810C>T polymorphism in predicting ONJ risk. These results can pave the way to the personalization of BP therapy, based on individual genotype.

Bisphosphonate osteonecrosis of the jaw: a historical and contemporary review

The use of bisphosphonate drugs has been popularised in the late 20th century for the management of many conditions associated with abnormalities of bone turnover, particularly metastatic and haematogenous malignancy and osteopenia. The increase in indications for the use of bisphosphonates was supported by what was thought to be a very good safety profile. However in 2003 cases of osteonecrosis related to the use of bisphosphonates were first described. The pathogenesis, and with this the explanation of why it only appears to affect the maxillofacial skeleton, and the best way of managing this problem remains unknown. In this review we examine the process of identification of this pathology and the development of guidelines from medical societies and professional bodies on the management of patients before commencing bisphosphonate therapy, requiring dental treatment whilst on therapy, or with a diagnosis of bisphosphonate associated osteonecrosis of the jaws.

Are nitrogen-containing intravenous bisphosphonates implicated in osteonecrosis of appendicular bones and bones other than the jaws? A survey and literature review

PURPOSE

The purpose of this study was to determine the incidence of osteonecrosis of appendicular bones due to nitrogen-containing intravenous bisphosphonates and the incidence of adverse effects in bones other than the jaws.

MATERIALS AND METHODS

A detailed search of the professional medical and dental literature was conducted. In addition, a questionnaire was mailed to all known orthopedic surgery training programs in the United States. Programs were queried as to clinical findings and other various scenarios.

RESULTS

There was a great paucity of literature that addressed the issue. Of the 154 questionnaires mailed, 29 (19%) were returned. Identification was optional; therefore, it was impossible to determine the geographic origin of the returned questionnaires. No orthopedic surgery training program indicated positive findings of osteonecrosis in the long bones due to nitrogen-containing intravenous bisphosphonates. There were rare reports in the literature of osteonecrosis in other areas of the bony skeleton.

CONCLUSION

On the basis of literature searches and national orthopedic questionnaires, there is only a rare incidence of osteonecrosis of the appendicular bones and bones other than the jaws due to nitrogen-containing intravenous bisphosphonates. There were no reports of adverse long bone effects, based on the questionnaires. There were rare reports in the literature.

Anatomic site variability in rat skeletal uptake and desorption of fluorescently labeled bisphosphonate

OBJECTIVES

Bisphosphonates commonly used to treat osteoporosis, Paget's disease, multiple myeloma, hypercalcemia of malignancy and osteolytic lesions of cancer metastasis have been associated with bisphosphonate-associated jaw osteonecrosis (BJON). The underlying pathogenesis of BJON is unclear, but disproportionate bisphosphonate concentration in the jaw has been proposed as one potential etiological factor. This study tested the hypothesis that skeletal biodistribution of intravenous bisphosphonate is anatomic site-dependent in a rat model system.

MATERIALS AND METHODS

Fluorescently labeled pamidronate was injected intravenously in athymic rats of equal weights followed by in vivo whole body fluorimetry, ex vivo optical imaging of oral, axial, and appendicular bones and ethylenediaminetetraacetic acid bone decalcification to assess hydroxyapatite-bound bisphosphonate.

RESULTS

Bisphosphonate uptake and bisphosphonate released per unit calcium were similar in oral and appendicular bones but lower than those in axial bones. Hydroxyapatite-bound bisphosphonate liberated by sequential acid decalcification was the highest in oral, relative to axial and appendicular bones (P < 0.05).

CONCLUSIONS

This study demonstrates regional differences in uptake and release of bisphosphonate from oral, axial, and appendicular bones of immune deficient rats.

Bisphosphonate related osteonecrosis of the jaw--manifestation in a microvascular iliac bone flap

Bisphosphonate related osteonecrosis of the jaw (BRONJ) is a side effect that may emerge due to a long-term bisphosphonate therapy. Although the timely diagnosis and initiation of treatment are associated with good outcome results, extended cases require whole parts of the jaw to be resected. A possible treatment option is the bony reconstruction of the jaw using microvascular bone flaps. We report, for the first time, the development of a bisphosphonate related osteonecrosis in a microvascular iliac bone graft, a reconstruction that was performed following a partial mandibulectomy due to BRONJ stage III. The observation of BRONJ manifestation in an osseous microvascular transplant is a novel finding that sheds new light on current pathogenesis theories that surround this entity. Furthermore, it is hypothesized that BRONJ is able to progress to adjacent bone. In addition, bone reconstruction in patients suffering from BRONJ may be seen more critically.

Bone scans, bisphosphonates, and a lack of acute changes within the mandible

PURPOSE

The etiology of osteonecrosis of the jaw is poorly understood, but preferential mandibular uptake of intravenous bisphosphonates (IVBPs) has been implicated. We examined this association within a prospective study assessing the effect of IVBPs on radionuclide bone scanning.

PATIENTS AND METHODS

Women with at least 3 osseous breast metastases on bone scanning and previous IVBP use within 8 weeks were eligible for the present study. After the first clinically indicated bone scan, the patients received zoledronic acid within 72 hours and underwent a second bone scan within another 72 hours. The regions of interest on the bone scan were read in triplicate, and the mean count per pixel was calculated for the mandible (C(M)), left femur (C(FL)), right femur (C(FR)), and thigh (C(B)). The mandibular bone turnover (MBT) was quantified as the ratio of (C(M) - C(B))/(C(F) - C(B)), where C(F) = (C(FL) + C(FR)/2). The MBT was compared before and after IVBP use.

RESULTS

A total of 10 patients were enrolled (median age 51 years, range 40 to 71); none had known osteonecrosis of the jaw. Of the 10 patients, 8 had paired bone scans available for analysis. The previous zoledronic acid exposure was 48.6 mg (range 24 to 148) for a median of 13 months (range 6 to 35). The baseline mean MBT ratio was 2.33 (range 0.88 to 4.22). After IVBP administration, the mean MBT ratio was statistically unchanged at 2.23 (range 1.05 to 3.09). The MBT had declined in 4 patients and increased in 4. Only 1 patient had had an MBT of less than 1.0 before IVBP use, and no patient had an MBT ratio of less than 1.0 after IVBP use.

CONCLUSIONS

The mandibular region appears to be a site of increased uptake of technetium-99m bound to methylene diphosphonate-technetium. Acute changes in bisphosphonate binding in the mandible were not observed in our patients receiving chronic IVBP therapy.

Long-term treatment with bisphosphonates and their safety in postmenopausal osteoporosis

Bisphosphonates are the leading drugs for the treatment of osteoporosis. In randomized controlled trials (RCTs), alendronate, risedronate, and zoledronate have shown to reduce the risk of vertebral, nonvertebral, and hip fractures, whereas RCTs with ibandronate show antifracture efficacy at vertebral sites. Bisphosphonates are generally well tolerated and safe. Nevertheless, adverse events have been noted, and it is important to consider the strength of the evidence for causal relationships. Effects on the gastrointestinal tract and kidney function are well recognized, as are transient acute-phase reactions. Atrial fibrillation was first identified as a potential adverse event in a zoledronate trial, but subsequent trials and analyses failed to substantiate an association with bisphosphonates. Case reports have suggested a relationship between oral bisphosphonates and esophageal cancer, but this has not been demonstrated in epidemiologic studies. A possible association between bisphosphonate use and osteonecrosis of the jaw (ONJ) has also been suggested. However, the risk of ONJ in patients with osteoporosis appears to be very low, with no evidence from prospective RCTs of a causal association. There are reports of occasional occurrence of subtrochanteric or diaphyseal fractures in osteoporotic patients, but an association with bisphosphonate therapy is not substantiated by epidemiologic studies or prospective RCTs.

A novel animal model to study non-spontaneous bisphosphonates osteonecrosis of jaw

The aim of this study was to evaluate a novel animal model of bisphosphonates-associated osteonecrosis, which realistically recapitulates the same pathological human condition. Five Wistar rats were given intravenous zoledronic acid 0.04 mg once a week for 5 weeks. After 2 weeks, the animals underwent the extraction of an upper molar, producing a 4 mm-diameter bone defect on the same site. After 7 weeks from the extraction, the animals were clinically examined and a bone scintigraphy was carried out. After an additional week, the rats were killed and both Computerized Tomography and histological analysis were performed. Five rats, not treated with zoledronic acid and exposed to the same surgical treatment, were used as controls. At 7 weeks after the extraction, all the rats treated with zoledronic acid showed expansion of the defect and bone exposure. These features were confirmed by bone scintigraphy. The rats of the control group demonstrated epithelialization of the bone defect and a normal uptake of the contrast medium during the scan. The Computerized Tomography scan disclosed irregularity of the cortical margin and bone destruction, which were not evident in the control group. On microscopy, the samples showed necrotic bone, loss of osteocytes and peripheral resorption without inflammatory infiltrate, while the controls showed normal bone healing. The rat treated with zoledronic acid can be considered a novel, reliable and reproducible animal model to understand better the pathophysiology of osteonecrosis of the jaw and to develop a therapeutic approach.

Skeletal accumulation of bisphosphonates: implications for osteoporosis treatment

BACKGROUND

Bisphosphonates (BPs), the gold-standard pharmacological treatment for osteoporosis, are unique in that they become physically bound to the bone matrix and therefore accumulate over time. This skeletal accumulation has important physiological implications that are not completely understood.

OBJECTIVE

To review concepts related to the biological effects of BP accumulation in the skeleton.

METHODS

Articles concerning skeletal accumulation of BP treatment were identified.

RESULTS/CONCLUSIONS

Skeletal accumulation of BP, dictated by both chemical and biological factors, is dose-dependent, differs among skeletal sites and likely differs among the various BPs. Bisphosphonate embedded within the skeletal matrix has lasting biological effects, the results of which have both positive and negative implications for bone remodeling. As alternative anti-remodeling agents gain approval for treatment of osteoporosis, the property of skeletal accumulation will likely be unique to BPs and therefore may be the property that determines the future use of this drug class.