Updates on bisphosphonates and potential pathobiology of bisphosphonate-induced jaw osteonecrosis

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.

Effect of alendronate on alveolar bone resorption and angiogenesis in rats with experimental periapical lesions

AIM

To investigate the effects of systemically administered alendronate, one of the most potent bisphosphonates (BPs), on alveolar bone resorption and angiogenesis in rats subjected to experimental periapical lesions over two time periods.

METHODOLOGY

Forty adult Sprague-Dawley (SD) rats were divided equally into control and experimental groups, and the pulp chambers of mandibular first molars of all rats were exposed to the oral environment to induce periapical lesions. The experimental group received daily subcutaneous injections of alendronate at a dose of 0.25 mg kg(-1), whereas the control group received only the saline vehicle. These injections were initiated 1 week before the periapical lesion induction and then continued daily throughout the entire experimental period. After 2 or 4 weeks following pulp exposure, the rats were killed, and the mandibles were examined histologically for periapical bone loss area, number of microvascular vessels (NMV) and tartrate-resistant acid phosphatase (TRAP) activity.

RESULTS

Overall, periapical bone loss area and the number of TRAP-positive cells (osteoclasts) were significantly decreased at 2 and 4 weeks, respectively, after daily subcutaneous injection of alendronate compared with the control group (P < 0.05). There was no significant decrease change in NMV (P > 0.05).

CONCLUSIONS

Administration of alendronate to rats might inhibit alveolar bone resorption associated with periapical disease, which might not lead to impairment of angiogenesis. However, because of the differences between rats and humans, one has to consider the possible consequences of this treatment in the clinic.

[Relationship between osteonecrosis of the jaw and bisphosphonate treatment]

Bisphosphonate treatment and its aetiopathogenic association with aseptic osteonecrosis of the jaw is one of the more prominent public health issues today. The aim of this review is to see into the mechanisms of bisphosphonate effects on bones described in literature (anti-osteoclastic activity, cytotoxicity, antiangiogenesis, genetic factors, and imbalance between osteoclasts and osteoblasts). Bisphosphonate treatment is the dominant cause of jaw necrosis. Epidemiological data show an exclusive incidence of osteonecrosis of the jaw in patients who took one or a combination of nitrogen-containing bisphosphonates. Risk factors vary by the bisphosphonate potency (particularly risky are the highly potent pamidronate and zoledronate, which are given intravenously), dosage, duration of treatment, and the illness. Jaw necrosis is most common in oncology patients, and only 5 % in patients with osteoporosis. From a dental-medical point of view, a good oral health is important because osteonecrosis often appears after a periodontal or oral surgical procedure.

Effect of low-level laser irradiation on bisphosphonate-induced osteonecrosis of the jaws: preliminary results of a prospective study

OBJECTIVE

The aim of this study was to detail the clinical efficacy of low-level laser therapy (LLLT) for the management of bisphosphonate-induced osteonecrosis of the jaws (ONJ-BP).

BACKGROUND

ONJ-BP is the correct term, recently emerged, to describe a significant complication in a subset of patients receiving drugs such as zoledronic acid, pamidronate, and alendronate. No definitive standard of care has been set for ONJ-BP and no definitively agreed guidelines have been provided. There is currently no consensus on the correct approach to the issue.

MATERIALS AND METHODS

The investigators studied a prospective cohort of 20 patients affected by ONJ-BP, who received biostimulation with a pulsed diode laser (GaAs). Patients were exposed to a 904-nm infrared laser (50 kHz, 28.4 J/cm(2) energy density, 40% duty cycle, spot size 0.8 cm). Outcome variables were the size of lesions, edema, visual analogue score of pain, presence of pus, fistulas, and halitosis. Preoperative results were compared with the postoperative outcome and statistically evaluated.

RESULTS

Four weeks after LLLT, a statistically significant difference was observed for reported pain (p = 0.0001), clinical size (p = 0.0034), edema (p = 0.0005), and presence of pus and fistulas (p = 0.0078 and p = 0.03, respectively).

CONCLUSION

This study suggests that LLLT would appear to be a promising modality of treatment for patients with ONJ-BP, providing that clinical efficacy is safe and well tolerated, especially by those patients who require conservative treatment. Of course, this needs to be addressed further in larger and randomly controlled studies in different clinical settings.

Human bone marrow stromal cells display variable anatomic site-dependent response and recovery from irradiation

OBJECTIVES

Orofacial bone is commonly affected by osteoradionecrosis (ORN) during head and neck cancer radiotherapy possibly due to interactions of several factors including radiation damage to resident bone marrow stromal cells (BMSCs). Irradiation causes DNA damage, triggers p53-dependent signalling resulting in either cell-cycle arrest or apoptosis. In same individuals, disproportionately higher rapid growth of orofacial BMSCs relative to those of axial/appendicular bones suggests their response to radiation is skeletally site-specific. We hypothesised that survival and osteogenic recovery capacity of irradiated human BMSCs is site-dependent based on anatomic skeletal site of origin.

METHODS

Early passage BMSCs from maxilla, mandible and iliac crest of four normal volunteers were exposed to 2.5 to 10 Gy gamma radiation to evaluate clonogenic survival, effects on cell cycle, DNA damage, p53-related response and in vivo osteogenic regenerative capacity.

RESULTS

Orofacial bone marrow stromal cells (OF-MSCs) survived higher radiation doses and recovered quicker than iliac crest (IC-MSCs) based on clonogenic survival, proliferation and accumulation in G0G1 phase. Post-irradiation p53 level was relatively unchanged but expression of p21, a downstream effector was moderately increased in OF-MSCs. Re-establishment of in vivo bone regeneration was delayed more in irradiated IC-MSCs relative to OF-MSCs.

CONCLUSIONS

Effect of irradiation on human BMSCs was skeletal site-specific with OF-MSCs displaying higher radio-resistance and quicker recovery than IC-MSCs.

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.

Longitudinal Cohort Study of Risk Factors in Cancer Patients of Bisphosphonate-Related Osteonecrosis of the Jaw

Purpose

The reported incidence of osteonecrosis of the jaw (ONJ) ranges from 0.94% to 18.6%. This cohort study aimed to calculate the incidence of and identify the risk factors for ONJ in patients with cancer treated with intravenous zoledronate, ibandronate, and pamidronate.

Patients and Methods

Data analyzed included age, sex, smoking status, underlying disease, medical and dental history, bisphosphonates (BP) type, and doses administered. Relative risks, crude and adjusted odds ratios (aORs), and cumulative hazard ratios for ONJ development were calculated.

Results

We included 1,621 patients who received 29,006 intravenous doses of BP, given monthly. Crude ONJ incidence was 8.5%, 3.1%, and 4.9% in patients with multiple myeloma, breast cancer, and prostate cancer, respectively. Patients with breast cancer demonstrated a reduced risk for ONJ development, which turned out to be nonsignificant after adjustment for other variables. Multivariate analysis demonstrated that use of dentures (aOR = 2.02; 95% CI, 1.03 to 3.96), history of dental extraction (aOR = 32.97; 95% CI, 18.02 to 60.31), having ever received zoledronate (aOR = 28.09; 95% CI, 5.74 to 137.43), and each zoledronate dose (aOR = 2.02; 95% CI, 1.15 to 3.56) were associated with increased risk for ONJ development. Smoking, periodontitis, and root canal treatment did not increase risk for ONJ in patients receiving BP.

Conclusion

The conclusions of this study validated dental extractions and use of dentures as risk factors for ONJ development. Ibandronate and pamidronate at the dosages and frequency used in this study seem to exhibit a safer drug profile concerning ONJ complication; however, randomized controlled trials are needed to validate these results. Before initiation of a bisphosphonate, patients should have a comprehensive dental examination. Patients with a challenging dental situation should have dental care attended to before initiation of these drugs.

Osteotomy and primary wound closure in bisphosphonate-associated osteonecrosis of the jaw: a prospective clinical study with 12 months follow-up

GOALS OF WORK

This is a prospective clinical study aimed at assessing the success rate of osteotomy and primary wound closure in patients with bisphosphonate-associated osteonecrosis of the jaw (BONJ).

MATERIALS AND METHODS

Fifty patients who had received bisphosphonates intravenously and subsequently suffered from BONJ were included in the study. All patients underwent osteotomy of the affected jaw bone region and primary wound closure under general anaesthesia. They were followed up bimonthly for a period of 12 months.

RESULTS

Macroscopically altered bone could be completely removed in all cases. In two patients with plasmocytoma, major bleeding occurred postoperatively that required monitoring in an intensive care unit. In two cases, recurrence of BONJ was diagnosed during the first 2 months. In three patients, recurrence appeared between the fourth and the sixth month. In these cases, an additional osteotomy had to be performed. Six patients died during the follow-up period. In the remaining 39 patients, no signs of recurrence could be detected during the follow-up of 12 months. The success rate of the surviving patients was 89% after 1 year.

CONCLUSION

Due to the high success rate of osteotomy and primary wound closure, it should be checked for every patient suffering from BONJ if osteotomy is a viable treatment option.

Tracking gene expression during zebrafish osteoblast differentiation

The transcription factors RUNX2 and OSX have been shown to act sequentially to direct mammalian osteoblast differentiation. RUNX2 is required during the early stages of commitment and acts in part to activate Osx transcription. OSX and RUNX2 then act to direct transcription of bone matrix proteins. Here, we investigate the expression of these genes and others during zebrafish osteoblastogenesis. Using whole-mount in situ hybridization, we find that, during the formation of a given bone, the zebrafish homologues of mouse Runx2 (runx2a and runx2b) are typically expressed before the onset of osx. osx expression is usually followed by up-regulation of the bone matrix proteins, col1a2 and osteonectin. These results suggest that the mammalian pathway is conserved during development of the head and shoulder skeleton of zebrafish. We also analyze the expression of three atypical bone markers (tcf7, cvl2, and col10a1) in an effort to place them within this canonical hierarchy.

Importance of microcracks in etiology of bisphosphonate-related osteonecrosis of the jaw: a possible pathogenetic model of symptomatic and non-symptomatic osteonecrosis of the jaw based on scanning electron microscopy findings

The aim of this study was to evaluate a possible role of microcracks in the pathogenesis of bisphosphonate-related osteonecrosis of the jaw (ONJ) and to discuss an etiological model. Bone samples from 35 patients with ONJ were analyzed. Control samples were taken from five patients with osteomyelitis (OM), ten patients with osteoradionecrosis, seven patients with osteoporosis and bisphosphonate medication without signs of ONJ, and six osteoporotic elderly patients. Samples were examined using scanning electron microscopy. In 54% of the bone samples of patients with ONJ, microcracks were seen. Inflammatory and connective tissue reactions within the microcracks were evident in 82% of the cases, indicating that these cracks were not artificial. In contrast, only 29% of samples from patients with oral bisphosphonate medication without ONJ, no sample from patients with OM, none of the osteoradionecrosis group, and only 17% from patients with osteoporosis showed microcracks. Statistically significant differences could be found between the ONJ group and the group after irradiation and the group with OM, respectively. The evidence of microcracks could be a first step in the pathogenesis of bisphosphonate-related ONJ. The accumulation of these microcracks leads to a situation that could be named "non-symptomatic ONJ". Disruptions of the mucosal integrity may then allow bacterial invasion, leading to jawbone infection with exposed bone, fistulas, and pain. This state could be called "symptomatic ONJ". Furthermore, an assumed local immunosuppression as indicated by various studies could explain the severe courses of therapy-resistant ONJ as regularly observed.

Bisphosphonates and osteonecrosis: potential treatment or serious complication?

They are commonly used to treat osteoporosis and other diseases that involve osteoclast-mediated bone resorption, including Paget's disease and multiple myeloma. Their use in treating osteonecrosis of the femoral head has been studied and theoretically holds promise. There are complications associated with these medications, however, including the development of osteonecrosis in the jaw.

Osteonecrosis of the jaw in patients with multiple myeloma treated with zoledronic acid

Intravenous bisphosphonates-the potent inhibitors of osteoclast-mediated bone resorption are among the most commonly prescribed drugs in the management of multiple myeloma (MM). Zoledronic acid (ZA) is a new generation potent intravenous bisphosphonate that has been approved for the treatment and prevention of bone lesions, and/or hypercalcemia associated with MM. Osteonecrosis of the jaw (ONJ) is an emerging serious side effect of the new generation bisphosphonates with a growing number of reports related to this pathological entity. ONJ usually appears following oral surgical and dental procedures but sometimes occur spontaneously. These cases are mostly seen and treated by dentists and oral surgeons. The aim of this study was to discuss the frequency, characteristics, risk factors, management and histopathological features of ZA induced ONJ based on the literature and illustrated with five own cases. Thirty-two patients with MM who received ZA for a median period of 26.5 +/- 18.7 months (min: 5 months, max: 76 months) were evaluated. ONJ was detected in five patients and mean drug duration time was 34 months. The frequency was 15% and the patients were usually symptomatic. There was no significant difference in terms of the duration of ZA in patients with and without ONJ. Management of these established cases were performed with medical treatment, minor debridement, sequestrectomy, and combining bone resection with autologous platelet rich plasma. Our data indicate that ZA therapy has a major role in the development of ONJ a fact that should be considered by physicians treating MM patients.

Osteonecrosis of the jaw complicating bisphosphonate treatment for bone disease in multiple myeloma: an overview with recommendations for prevention and treatment

Osteonecrosis of the Jaw (ONJ) is a recently recognised and potentially highly morbid complication of bisphosphonate therapy in the setting of metastatic malignancy, including myeloma. Members of the Medical and Scientific Advisory Group of the Myeloma Foundation of Australia formulated guidelines for the management of bisphosphonates around the issue of ONJ, based on the best available evidence in June 2008. Prior to commencement of therapy, patients should have an oral health assessment and be educated about the risks of ONJ. Dental assessment should occur 6 monthly during therapy. If tooth extraction is required, sufficient time should be allowed for complete healing to occur prior to commencement of bisphosphonate. As the risk of ONJ increases with duration of bisphosphonate therapy, we recommend annual assessment of dose with modification to 3 monthly i.v. therapy or to oral therapy with clodronate for those with all but the highest risk of skeletal-related event. Established ONJ should be managed conservatively; a bisphosphonate "drug holiday" is usually indicated and invasive surgery should generally be avoided. These recommendations will assist with clinical decision making for myeloma patients who are at risk of bisphosphonate-associated ONJ.