Bacterial promotion of bisphosphonate-induced osteonecrosis in Wistar rats

Potential role of comprehensive dental care in preventing medication related osteonecrosis of the jaw (MRONJ): a single centre study

OBJECTIVE

Medication-related osteonecrosis of the jaw bones (MRONJ) is a well-known complication of antiresorptive and antiangiogenic drugs. Since the first report, more occurrences of MRONJ have been described worldwide. Dental extraction has been described by many studies as one of the risk factors for MRONJ. Comprehensive dental care (CDC) is a preventive dental method provided to patients prior to drug commencement. This study aims to determine the association between CDC and MRONJ.

PATIENTS AND METHODS

A retrospective analysis was performed on 75 medical records of patients on antiresorptive and/or antiangiogenic drugs between February 2018 and May 2021. Demographics and clinical and radiographic data were collected. Univariate and multivariate analyses were performed to determine the factors associated with MRONJ.

RESULTS

Of the 75 patients who met the inclusion criteria, 11 (14.7%) developed MRONJ. Three out of 11 patients (27.2%) developed MRONJ spontaneously, while eight patients (72.8%) developed it after trauma from dentures or dental extractions. Following a binary logistic regression analysis, the lack of CDC was identified as a significant predictor of MRONJ. Patients who did not receive CDC had an odds ratio of 8.64 (95% confidence interval (CI): 1.27-58.62, p = 0.03). However, dental extraction did not show a statistically significant association with MRONJ in both the univariate and multivariate analyses.

CONCLUSION

CDC before treatment with antiresorptive and antiangiogenic drugs is a potentially effective preventive method for reducing MRONJ. Dental extraction was not a significant factor in relation to MRONJ.

Etiopathogenesis of medication-related osteonecrosis of the jaws: a review

This study compiles the main hypotheses involved in the etiopathogenesis of medication-related osteonecrosis of the jaw (MRONJ). A narrative review of the literature was performed. The etiopathogenesis of MRONJ is multifactorial and not fully understood. The main hypothesis considers the disturbance of bone turnover caused by anti-resorptive drugs. Bisphosphonates and denosumab inhibit osteoclast activity through different action mechanisms, accumulating bone microfracture. Other hypotheses also consider oral infection and inflammation, the antiangiogenic effect and soft tissue toxicity of bisphosphonates, and the inhibition of lymphangiogenesis. Knowledge of the current theories for MRONJ is necessary to define future studies and protocols to minimize the incidence of this severe condition.

Exosome-targeted delivery of METTL14 regulates NFATc1 m6A methylation levels to correct osteoclast-induced bone resorption

Osteoporosis has a profound influence on public health. First-line bisphosphonates often cause osteonecrosis of the jaw meanwhile inhibiting osteoclasts. Therefore, it is important to develop effective treatments. The results of this study showed that the increased level of NFATc1 m6A methylation caused by zoledronic acid (ZOL), with 4249A as the functional site, is highly correlated with the decreased bone resorption of osteoclasts. Upstream, METTL14 regulates osteoclast bone absorption through the methylation functional site of NFATc1. Downstream, YTHDF1 and YTHDF2 show antagonistic effects on the post-transcriptional regulation of NFATc1 after the m6A methylation level is elevated by METTL14. In this study, meRIP-Seq, luciferase reporter assays, meRIP and other methods were used to elucidate the NFATc1 regulatory mechanism of osteoclasts from the perspective of RNA methylation. In addition, EphA2 overexpression on exosomes is an effective biological method for targeted delivery of METTL14 into osteoclasts. Importantly, this study shows that METTL14 released by exosomes can increase the m6A methylation level of NFATc1 to inhibit osteoclasts, help postmenopausal osteoporosis patients preserve bone mass, and avoid triggering osteonecrosis of the jaw, thus becoming a new bioactive molecule for the treatment of osteoporosis.

Zoledronate Promotes Peri-Implant Osteogenesis in Diabetic Osteoporosis by the AMPK Pathway

Together with diabetic osteoporosis (DOP), diabetes patients experience poor peri-implant osteogenesis following implantation for dentition defects. Zoledronate (ZOL) is widely used to treat osteoporosis clinically. To evaluate the mechanism of ZOL for the treatment of DOP, experiments with DOP rats and high glucose-grown MC3T3-E1 cells were used. The DOP rats treated with ZOL and/or ZOL implants underwent a 4-week implant-healing interval, and then microcomputed tomography, biomechanical testing, and immunohistochemical staining were performed to elucidate the mechanism. In addition, MC3T3-E1 cells were maintained in an osteogenic medium with or without ZOL to confirm the mechanism. The cell migration, cellular actin content, and osteogenic differentiation were evaluated by a cell activity assay, a cell migration assay, as well as alkaline phosphatase, alizarin red S, and immunofluorescence staining. The mRNA and protein expression of adenosine monophosphate-activated protein kinase (AMPK), phosphorylated AMPK (p-AMPK), osteoprotegerin (OPG), receptor activator of nuclear factor kappa B ligand (RANKL), bone morphogenetic protein 2 (BMP2), and collagen type I (Col-I) were detected using real-time quantitative PCRs and western blot assays, respectively. In the DOP rats, ZOL markedly improved osteogenesis, enhanced bone strength and increased the expression of AMPK, p-AMPK, and Col-I in peri-implant bones. The in vitro findings showed that ZOL reversed the high glucose-induced inhibition of osteogenesis via the AMPK signaling pathway. In conclusion, the ability of ZOL to promote osteogenesis in DOP by targeting AMPK signaling suggests that therapy with ZOL, particularly simultaneous local and systemic administration, may be a unique approach for future implant repair in diabetes patients.

Medication-related osteonecrosis of the jaw using periodontitis-induced rat before tooth extraction

OBJECTIVE

This study aimed to investigate the occurrence of medication-related osteonecrosis of the jaw (MRONJ) after tooth extraction due to periodontitis in ovariectomized rats.

METHODS

Twenty-four osteoporosis-induced rats were administered with zoledronic acid (ZA; ZA group) or saline (CONT group). In both groups, tooth extraction was performed after inducing periodontitis, and all animals were sacrificed 8-week after tooth extraction.

RESULTS

Micro-CT of the tibia showed that the bone volume fraction, bone surface density, trabecular number, and bone mineral density were significantly higher in the ZA group than in the CONT group. Histologically, the proliferative zone on the growth plate was thicker in the ZA group than in the CONT group. Micro-CT of the extraction sites revealed that the bone volume fraction was significantly higher in the ZA group than in the CONT group. Radiologically, the ZA group showed partial healing and delayed healing. Histological analysis revealed normal bone healing status with completely healed epithelium in the extraction sites of the CONT group, whereas abnormal empty osteocytes in the necrotic bone and inflammatory infiltration were observed in the ZA group.

CONCLUSION

The incidence of MRONJ increased in the rats administered with ZA.

The feasibility of discriminating BRONJ lesion bone with Raman spectroscopy

Background

With the frequent use of Bisphosphonates (BPs), the morbidity of BP-related osteonecrosis of the jaw (BRONJ) is also increasing. However, the prevention and treatment of BRONJ is faced with enormous challenges. This study aimed to illuminate the influence of BP administration in the rat mandible and explore the feasibility of discriminating BRONJ lesion bone with Raman spectroscopy.

Materials and methods

First, we explored the time- and mode-dependent effects of BP administration on the rat mandible with Raman spectroscopy. Second, the BRONJ rat model was constructed, and the lesion and healthy bone components were analyzed using Raman spectroscopy.

Results

When only BPs were administered, no rats showed BRONJ symptoms, and no difference could be found in the Raman spectra. However, when combined with local surgery, six (6/8) rats showed BRONJ symptoms. The Raman spectra also showed a significant difference between the lesion and healthy bone.

Conclusion

In the progression of BRONJ, BPs and local stimulation play an essential role. Both BPs administration and local stimulation need to be controlled to prevent BRONJ. Moreover, BRONJ lesion bone in rats could be discriminated with Raman spectroscopy. This novel method would become a complement in the treatment of BRONJ in the future.

Medication-Related Osteonecrosis: Why the Jawbone?

Medication-related osteonecrosis of the jaw (MRONJ) has emerged as a complication of anti-resorptive medications. Despite its low incidence rate, this problem has gained attention in recent years due to its devastating consequences and lack of preventive strategy. The fact that MRONJ incidence has been exclusive to the jawbones, despite the systemic effect of anti-resorptive medications, could be a starting point to unravel the multifactorial pathogenesis of this condition. This review aims to negotiate the question of why the jawbone is more susceptible to MRONJ than other skeletal sites. Approaching the problem from this perspective could provide new directions for the prevention of MRONJ and expand our understanding of the unique oral microenvironment.

Establishment and assessment of rodent models of medication-related osteonecrosis of the jaw (MRONJ)

Medication-related osteonecrosis of the jaw (MRONJ) is primarily associated with administering antiresorptive or antiangiogenic drugs. Despite significant research on MRONJ, its pathogenesis and effective treatments are still not fully understood. Animal models can be used to simulate the pathophysiological features of MRONJ, serving as standardized in vivo experimental platforms to explore the pathogenesis and therapies of MRONJ. Rodent models exhibit excellent effectiveness and high reproducibility in mimicking human MRONJ, but classical methods cannot achieve a complete replica of the pathogenesis of MRONJ. Modified rodent models have been reported with improvements for better mimicking of MRONJ onset in clinic. This review summarizes representative classical and modified rodent models of MRONJ created through various combinations of systemic drug induction and local stimulation and discusses their effectiveness and efficiency. Currently, there is a lack of a unified assessment system for MRONJ models, which hinders a standard definition of MRONJ-like lesions in rodents. Therefore, this review comprehensively summarizes assessment systems based on published peer-review articles, including new approaches in gross observation, histological assessments, radiographic assessments, and serological assessments. This review can serve as a reference for model establishment and evaluation in future preclinical studies on MRONJ.

Porphyromonas gingivalis Induces Bisphosphonate-Related Osteonecrosis of the Femur in Mice

One of the most prominent characteristics of bisphosphonate-related osteonecrosis of the jaw(BRONJ) is its site-specificity. Osteonecrosis tends to occur specifically in maxillofacial bones, in spite of a systemic administration of the medicine. Previous studies suggested rich blood supply and fast bone turnover might be reasons for BRONJ. Yet, a sound scientific basis explaining its occurrence is still lacking. The present study aimed to explore the role of Porphyromonas gingivalis (P. gingivalis), an important oral pathogen, on the site-specificity of bisphosphonate-induced osteonecrosis and to elucidate its underlying mechanism. Mice were intraperitoneally injected with zoledronic acid (ZA) or saline for 3 weeks. In the third week, the right mandibular first molars were extracted and circular bone defects with a diameter of 1 mm were created in right femurs. After the operation, drug administration was continued, and P. gingivalis suspension was applied to the oral cavities and femur defects. The mice were killed after four or eight weeks postoperatively. The right mandibles and femurs were harvested for micro-CT and histological analyses. A poor healing of bone defects of both jaws and femurs was noted in mice injected with both ZA and P. gingivalis. Micro-CT analysis showed a decreased bone volume, and histological staining showed an increased number of empty osteocyte lacunae, a decreased collagen regeneration, an increased inflammatory infiltration and a decreased number of osteoclasts. In addition, the left femurs were collected for isolation of osteoclast precursors (OCPs). The osteoclastogenesis potential of OCPs was analyzed in vitro. OCPs extracted from mice of ZA-treated groups were shown to have a lower osteoclast differentiation potential and the expression level of related genes and proteins was declined. In conclusion, we established a mouse model of bisphosphonate-related osteonecrosis of both the jaw and femur. P. gingivalis could inhibit the healing of femur defects under the administration of ZA. These findings suggest that P. gingivalis in the oral cavity might be one of the steering compounds for BRONJ to occur.

Nrf2 in the Field of Dentistry with Special Attention to NLRP3

The aim of this review article was to summarize the functional implications of the nuclear factor E2-related factor or nuclear factor (erythroid-derived 2)-like 2 (Nrf2), with special attention to the NACHT (nucleotide-binding oligomerization), LRR (leucine-rich repeat), and PYD (pyrin domain) domains-containing protein 3 (NLRP3) inflammasome in the field of dentistry. NLRP3 plays a crucial role in the progression of inflammatory and adaptive immune responses throughout the body. It is already known that this inflammasome is a key regulator of several systemic diseases. The initiation and activation of NLRP3 starts with the oral microbiome and its association with the pathogenesis and progression of several oral diseases, including periodontitis, periapical periodontitis, and oral squamous cell carcinoma (OSCC). The possible role of the inflammasome in oral disease conditions may involve the aberrant regulation of various response mechanisms, not only in the mouth but in the whole body. Understanding the cellular and molecular biology of the NLRP3 inflammasome and its relationship to Nrf2 is necessary for the rationale when suggesting it as a potential therapeutic target for treatment and prevention of oral inflammatory and immunological disorders. In this review, we highlighted the current knowledge about NLRP3, its likely role in the pathogenesis of various inflammatory oral processes, and its crosstalk with Nrf2, which might offer future possibilities for disease prevention and targeted therapy in the field of dentistry and oral health.

Preclinical models of medication-related osteonecrosis of the jaw (MRONJ)

Medication-related osteonecrosis of the jaw (MRONJ) is a potentially severe adverse event affecting patients with cancer and patients with osteoporosis who have been treated with powerful antiresorptives (pARs) or angiogenesis inhibitors (AgIs). pARs, including nitrogen-containing bisphosphonates (N-BPs; e.g., zoledronic acid, alendronate) and anti-RANKL antibodies (e.g., denosumab), are used to manage bone metastases in patients with cancer or to prevent fragility fractures in patients with osteoporosis. Though significant advances have been made in understanding MRONJ, its pathophysiology is still not fully elucidated. Multiple species have been used in preclinical MRONJ research, including the rat, mouse, rice rat, rabbit, dog, sheep, and pig. Animal research has contributed immensely to advancing the MRONJ field, particularly, but not limited to, in developing models and investigating risk factors that were first observed in humans. MRONJ models have been developed using clinically relevant doses of systemic risk factors, like N-BPs, anti-RANKL antibodies, or AgIs. Specific local oral risk factors first noted in humans, including tooth extraction and inflammatory dental disease (e.g., periodontitis, periapical infection, etc.), were then added. Research in rodents, particularly the rat, and, to some extent, the mouse, across multiple laboratories, has contributed to establishing multiple relevant and complementary preclinical models. Models in larger species produced accurate clinical and histopathologic outcomes suggesting a potential role for confirming specific crucial findings from rodent research. We view the current state of animal models for MRONJ as good. The rodent models are now reliable enough to produce large numbers of MRONJ cases that could be applied in experiments testing treatment modalities. The course of MRONJ, including stage 0 MRONJ, is characterized well enough that basic studies of the molecular or enzyme-level findings in different MRONJ stages are possible. This review provides a current overview of the existing models of MRONJ, their more significant features and findings, and important instances of their application in preclinical research.

Matrix-Bound Zolzoledronate Enhances the Biofilm Colonization of Hydroxyapatite: Effects on Osteonecrosis

(1) Background: The aim of this study was to test whether matrix-bound zoledronate (zol) molecules enhanced the oral biofilm colonization of a mineralized matrix, rendering the alveolar bone more susceptible to medication-related osteonecrosis of the jaw (MRONJ) following invasive dental procedures. (2) Methods: We tested the effect of matrix-bound zol on the growth and attachment of Porphyromonas gingivalis (Pg), Fusobacterium nucleatum (Fn) and Actinomyces israelii (Ai), and whether the nitrogen-containing component of zol contributed to such effect. The role of oral bacteria in the induction of osteonecrosis was then tested using an extra-oral bone defect model. (3) Results: The attachment of biofilm to hydroxyapatite discs increased when the discs were pre-treated with zol. Bacterial proliferation was not affected. Matrix-bound zol was more potent than non-nitrogen-containing etidronate in enhancing the colonization. Stimulation was dampened by pre-treating the bacteria with histidine. The delivery of oral biofilm to a tibial defect caused osteonecrosis in zol-treated rats. (4) Conclusions: We conclude that matrix-bound zol enhances the oral biofilm colonization of hydroxyapatite. This enhancement depended on the presence of the nitrogen-containing group. The oral biofilm rendered the extra-oral bone susceptible to medication-related osteonecrosis, suggesting that it has an important role in the induction of MRONJ.

Effective ancillary role and long-term course of daily or weekly teriparatide treatment on refractory medication-related osteonecrosis of the jaw: a clinical case series

Medication-related osteonecrosis of the jaw (MRONJ) is a potentially severe adverse side effect of antiresorptive agents. However, withdrawal of such agents in patients with osteoporosis may increase the risk of fracture. The treatment of MRONJ is challenging, and standard treatment guidelines have yet to be established. In this study, the aim was to find out whether adjuvant daily or weekly teriparatide (TPTD) injections were beneficial for exposed bony MRONJ lesions compared with standard conservative management. We also studied the complications and the patients' response to TPTD therapy. We enrolled 27 patients (January 2012 - December 2016) with chronic and refractory MRONJ. There were four men and 23 women (85% female). Nine patients who did not select TPTD therapy for several reasons formed the non-TPTD group; the remaining 18 were randomly assigned to the daily (n=9) or weekly (n=9) groups. All patients in both groups continued standard conservative therapy in addition to their daily or weekly subcutaneous injection of TPTD (20 μg or 56.5 μg, respectively). We evaluated the complications of TPTD and its benefits. Three patients in the daily group did not complete the study, resulting in six patients in the daily group, nine in the weekly group, and nine in the non-TPTD group in the final analysis. The exposed bone was completely covered with normal mucosa in all patients in the TPTD groups, and the healing period was shorter than that in the non-TPTD group. No patient had complications of atypical fractures of the femoral head. Daily and weekly TPTD treatment resulted in a shortened treatment period compared with standard conservative therapy, with no increase in the rate of complications or worsening of osteoporosis.

Nitrogen-containing bisphosphonates and lipopolysaccharide mutually augment inflammation via adenosine triphosphate (ATP)-mediated and interleukin 1β (IL-1β)-mediated production of neutrophil extracellular traps (NETs)

Among the bisphosphonates (BPs), nitrogen-containing BPs (N-BPs) have much stronger anti-bone-resorptive actions than non-N-BPs. However, N-BPs have various side effects such as acute influenza-like reactions after their initial administration and osteonecrosis of the jawbones after repeated administration. The mechanisms underlying such effects remain unclear. To overcome these problems, it is important to profile the inflammatory nature of N-BPs. Here, we analyzed the inflammatory reactions induced in mouse ear pinnae by the N-BPs alendronate (Ale) and zoledronate (Zol). We found the following: (i) Ale and Zol each induced two phases of inflammation (early weak and late strong ear swelling); (ii) both phases were augmented by lipopolysaccharides (LPSs; cell-surface constituent of gram-negative bacteria, including oral bacteria), but prevented by inhibitors of the phosphate transporters of solute carrier 20/34 (SLC20/SLC34); (iii) macrophages and neutrophils were involved in both phases of Ale+LPS-induced ear-swelling; (iv) Ale increased or tended to increase various cytokines, and LPS augmented these effects, especially that on interleukin 1β (IL-1β); (v) adenosine triphosphate (ATP) was involved in both phases, and Ale alone or Ale+LPS increased ATP in ear pinnae; (vi) the augmented late-phase swelling induced by Ale+LPS depended on both IL-1 and neutrophil extracellular traps (NETs; neutrophil-derived net-like complexes); (vii) neutrophils, together with macrophages and dendritic cells, also functioned as IL-1β-producing cells, and upon stimulation with IL-1β, neutrophils produced NETs; (viii) stimulation of the purinergic 2X7 (P2X7) receptors by ATP induced IL-1β in ear pinnae; (ix) NET formation by Ale+LPS was confirmed in gingiva, too. These results suggest that (i) N-BPs induce both early-phase and late-phase inflammation via ATP-production and P2X7 receptor stimulation; (ii) N-BPs and LPS induce mutually augmenting responses both early and late phases via ATP-mediated IL-1β production by neutrophils, macrophages, and/or dendritic cells; and (iii) NET production by IL-1β-stimulated neutrophils may mediate the late phase, leading to prolonged inflammation. These results are discussed in relation to the side effects seen in patients treated with N-BPs. © 2021 American Society for Bone and Mineral Research (ASBMR).

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.

Infection as an Important Factor in Medication-Related Osteonecrosis of the Jaw (MRONJ)

Medication-related osteonecrosis of the jaw (MRONJ) has become a well-known side effect of antiresorptive, and antiangiogenic drugs commonly used in cancer management. Despite a considerable amount of literature addressing MRONJ, it is still widely accepted that the underlying pathomechanism of MRONJ is unclear. However, several clinical and preclinical studies indicate that infection seems to have a major role in the pathogenesis of MRONJ. Although there is no conclusive evidence for the infection hypothesis yet, available data have shown a robust association between local infection and MRONJ development. This observation is very critical in order to implement policies to reduce the risk of MRONJ in patients under antiresorptive drugs. This critical review was conducted to collect the most reliable evidence regarding the link between local infection and MRONJ pathogenesis.

Antiresorptive medication in oncology: the clinical and dental profile of patients in a reference center

Objectives

: The aim of this study was to evaluate the profile of patients on antiresorptive therapies for cancer treatment and assess presence of oral lesions, oral hygiene status, and knowledge regarding medication-related osteonecrosis of the jaw (MRONJ).

Materials and Methods

This was an observational cross-sectional study that evaluated patients treated with antiresorptive medication at a single cancer hospital. Clinical data were collected and oral examination was performed to assess patient oral health.

Results

From July 2017 to December 2018, 90 patients were assessed; 64 were female and 26 were male, and the mean age was 61 years. The most common drug was an intravenous bisphosphonate, zoledronic acid. Among the 90 patients, 47 presented with some type of oral disease, isolated or associated. Among these 47 patients, 9 patients (10%) developed osteonecrosis. Oral hygiene was evaluated, and most patients, with or without MRONJ, presented with regular to poor condition. Regarding patient knowledge of the risks of MRONJ and the risks associated with dental surgery, 60% stated that they were not aware of the risks.

Conclusion

Identifying the profile of patients and their needs facilitates not only the preventive process, but also the emergence of new therapeutic options. Our study shows that most patients are weakened both by metastatic disease and antineoplastic treatment as well as by issues associated with aging because most were over 60 years of age. Collectively, this information should be considered for management of preventive and therapeutic measures.

Osteonecrosis of the Jaw Beyond Bisphosphonates: Are There Any Unknown Local Risk Factors?

INTRODUCTION

Bisphosphonate (BP)-related osteonecrosis of the jaw (BRONJ) is a complication of intravenous (IV) BP therapy. BP therapy locally affects the dentoalveolar area, while systemic effects are associated with parenteral/IV BP use. Despite numerous publications, the pathogenesis of BRONJ is not fully understood, as only some patients receiving IV BPs develop BRONJ.

PURPOSE

Can impaired bone remodeling (found in aseptic-ischemic osteonecrosis of the jaw [AIOJ], bone marrow defects [BMD], or fatty-degenerative osteonecrosis of the jaw [FDOJ]) represent a risk factor for BRONJ formation?

PATIENTS AND METHODS

A literature search clarified the relationship between AIOJ, BMD, FDOJ, and BRONJ, in which common characteristics related to signal cascades, pathohistology, and diagnostics are explored and compared. A case description examining non-exposed BRONJ is presented.

DISCUSSION

Non-exposed BRONJ variants may represent one stage in undetected BMD development, and progression to BRONJ results from BPs.

CONCLUSION

Unresolved wound healing at extraction sites, where wisdom teeth have been removed for example, may contribute to the pathogenesis of BRONJ. With IV BP administration, persisting AIOJ/BMD/FDOJ areas may be behind BRONJ development. Therapeutic recommendations include IV BP administration following AIOJ/BMD/FDOJ diagnosis and surgical removal of ischemic areas. BPs should not be regarded as the only cause of osteonecrosis.

Influence of prostate cancer status on the prevalence of medication-related osteonecrosis of the jaw

OBJECTIVE

The aim of this study was to evaluate the risk of osteonecrosis of the jaw (ONJ) in patients with prostate cancer, particularly the relationship between prostate cancer progression and ONJ development.

STUDY DESIGN

This single-center, retrospective, observational study included 113 patients who received zoledronic acid or denosumab for prostate cancer with bone metastasis between January 2012 and March 2020. The risk of ONJ was evaluated regarding age; antiresorptive drugs; duration of antiresorptive treatment; prostate cancer status, including castration-resistant prostate cancer (CRPC) and prostate-specific antigen level; chemotherapy; radium-223 treatment; corticosteroid treatment; diabetes mellitus; and dental extractions.

RESULTS

Overall, 28 patients had ONJ; 10 patients received zoledronic acid and 18 patients received denosumab. Multiple logistic regression analysis demonstrated that CRPC (odds ratio = 6.01; 95% confidence interval, 1.76-20.05; P = .004) and dental extractions (odds ratio = 12.40; 95% confidence interval, 3.42-44.70; P < .001) were significantly associated with ONJ. In addition, antiresorptive treatment lasting more than 1 year partially mediated between CRPC and development of ONJ.

CONCLUSION

CRPC and dental extraction are risk factors for developing ONJ, and antiresorptive treatment lasting more than 1 year is a partial mediator between CRPC and ONJ.

Oral Rehabilitation With Dental Implants and the Importance of a Preventive Evaluation for Osteonecrosis of the Jaws Associated With Medications

Osteonecrosis of the jaw is a possible oral complication resulting from antiresorptive therapies, such as bisphosphonates (Bfs). Although the etiology is not entirely clear, it has been shown to be dependent on several factors, with the traumatic stimulation caused by the placement of teeth implants indicated as one of the predisposing factors to this pathology. The indications and preventive methods for performing these procedures have been questioned, making it essential to determine the proper protocols. Thus, the present study aims to discuss the risks of the development of osteonecrosis in patients undergoing dental implant surgery who use Bfs as well as to discuss related local and systemic factors and possible methods for preventing this side effect. The study also aims to present a clinical case of an osteopenic patient who used Bfs and underwent rehabilitation through implants according to specific protocols, which resulted in successful treatment.

Delayed alveolar bone repair and osteonecrosis associated with Zoledronic Acid therapy in rats: macroscopic, microscopic and molecular analysis

Objective

This study aims to evaluate bone repair and the development of the medication related osteonecrosis of the jaw (MRONJ) associated with the use of zoledronic acid in Wistar rats.

Methodology

48 male Wistar rats were divided into four groups: ZA, treated with intraperitoneal zoledronic acid, 0.6 mg/kg every 28 days, totaling five doses; control (C), treated with 0.9% sodium chloride; ZA-surgical (SZA) and C-surgical (SC), submitted to extraction of the right upper molars 45 days after the first application. Alveolar bone repair was evaluated by macroscopic and histological analysis. Protein expression evaluations were performed by qPCR.

Results

Macroscopic evaluation showed that 91.66% (11) of the animals in the SZA group and 41.66% (5) from the SC group presented solution of epithelium continuity (P<0.05). All animals in the SZA group and none in the SC group had bone sequestration. The area of osteonecrosis was higher in the SZA group than in the SC group (P<0.05). In molecular evaluation, the SZA group presented changes in the expression of markers for osteoclasts, with increased RANK and RANKL, and a decrease in OPG.

Conclusion

The results highlighted strong and evident interference of zoledronic acid in bone repair of the socket, causing osteonecrosis and delayed bone remodeling.

Decreased Osteogenic Ability of Periodontal Ligament Stem Cells Leading to Impaired Periodontal Tissue Repair in BRONJ Patients

Bisphosphonate-related osteonecrosis of the jaws (BRONJ) is a severe adverse reaction, which results in progressive bone destruction in the maxillofacial region of patients. To date, the pathological mechanisms remain largely unclear. Recently, we found that BRONJ patient had significantly deep periodontal pockets and severe periodontal bone defects before the exposed necrotic bone. Human periodontal ligament stem cells (hPDLSCs) play key roles in physiological maintenance and regeneration of periodontal tissues. However, the activities of hPDLSCs derived from BRONJ lesions and the role of hPDLSCs in BRONJ periodontal defect repair remain poorly understood. The aim of the present study was to elucidate the role of hPDLSCs in BRONJ. In this study, we found that the capacities of cell proliferation, adhesion, and migration of hPDLSCs derived from BRONJ lesions (BRONJ-hPDLSCs) were significantly decreased compared with control-hPDLSCs. BRONJ-hPDLSCs underwent early apoptosis compared with control-hPDLSCs. Importantly, we first demonstrated that BRONJ-hPDLSCs exhibited impaired osteogenic differentiation abilities in ectopic osteogenesis of nude mice. The above results suggested that the impaired BRONJ-hPDLSCs may be an important factor in deficient periodontal repair of BRONJ lesions and provide new insight into the underlying mechanism of BRONJ.

Bone mineralization and vascularization in bisphosphonate-related osteonecrosis of the jaw: an experimental study in the rat

OBJECTIVES

Pathogenesis of bisphosphonate-related osteonecrosis of the jaws (BRONJ) is not fully explained. An antiangiogenic effect of bisphosphonates (BPs) or an altered bone quality have been advocated. The aims of the present study were to analyze alveolar mandibular vascularization and bone quality in rats with BRONJ.

MATERIALS AND METHODS

Thirty-eight Sprague-Dawley rats were randomized into two groups: zoledronic acid (ZA), n = 27, and control (CTRL) n = 11. The ZA group received a weekly IV injection of ZA (100 μg/kg) during 10 weeks. The CTRL group received saline. After 6 weeks, extraction of the right mandibular molars was performed. Rats were sacrificed after 14 weeks. Microtomography characterized bone lesions and vascularization after injection of a radio-opaque material. Raman microspectroscopy evaluated bone mineralization.

RESULTS

Fifty-five percent of ZA rats presented bone exposure and signs of BRONJ. None sign was found at the left hemimandible in the ZA group and in the CTRL group. Vascular density appeared significantly increased in the right hemimandibles of the CTRL group compared to the left hemimandibles. Vascularization was reduced in the ZA group. A significantly increased of the mineral-to-amide ratio was found in the alveolar bone of ZA rats by Raman microspectroscopy.

CONCLUSIONS

In a rat model of BRONJ, microtomography evidenced osteonecrosis in BRONJ. Raman spectroscopy showed an increased mineralization. Vascularization after tooth extraction was impaired by ZA.

CLINICAL RELEVANCE

Prolonged BP administration caused an increase in the mineralization and a quantitative reduction of the vascularization in the alveolar bone; both factors might be involved concomitantly in the BRONJ pathophysiology.

Medication-related osteonecrosis of the jaw: definition and best practice for prevention, diagnosis, and treatment

Skeletal complications caused by osteoporosis or bone metastases are associated with considerable pain, increased mortality, and reduced quality of life. Furthermore, such events place a burden on health care resources. Agents that prevent bone resorption, such as bisphosphonates or denosumab, can reduce the risk of skeletal-related events and are widely used in patients with osteoporosis or bone metastases of cancer. Medication-related osteonecrosis of the jaw (MRONJ) is a rare, but potentially serious, adverse event associated with high cumulative doses of bisphosphonates or denosumab. However, MRONJ can be treated, and the likelihood of the development of this condition can be reduced through prophylactic dental care and the maintenance of good oral hygiene. Dentists, as part of a multiprofessional team, have a critical role in preventing MRONJ. This review describes the incidence and pathophysiology of MRONJ and provides guidance for dental practitioners with regard to the screening, prophylactic treatment, diagnosis, and management of patients with this condition.

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.

Zoledronic acid exacerbates inflammation through M1 macrophage polarization

Background

Zoledronic acid (Zol), one of the bisphosphonates, is frequently utilized for the treatment of osteoporosis and bone metastasis. However, the onset of medication-related osteonecrosis of the jaw (MRONJ) following dental treatments has become a serious issue. We reported previously that osteonecrosis can be induced by Zol and lipopolysaccharide (LPS) in vivo, suggesting the involvement of Zol in inflammation. Macrophages are divided into M1/M2 macrophages. M1 macrophages are involved in the induction and exacerbation of inflammation and express proinflammatory mediators including interleukin (IL)-1. On the other hand, M2 macrophages are associated with anti-inflammatory reactions through the expression of anti-inflammatory cytokines, such as IL-10. In the present study, we clarified the effects of Zol on M1/M2 macrophage polarization in vitro.

Methods

Human monocytic THP-1 cells were polarized to macrophage-like cells by phorbol 12-myristate 13-acetate (PMA), and, after culturing for an additional 24 h with or without Zol, then polarized to M1 macrophages by LPS or to M2 macrophages by IL-4. Cell viability was examined by the WST-8 assay. Gene expression was confirmed by the real-time polymerase chain reaction. Protein expression was detected by western blotting and enzyme-linked immunosorbent assays.

Results

Zol treatment upregulated the expression of IL-1β mRNA and protein through NLRP3 inflammasome activation in LPS-treated THP-1 cells. Zol treatment did not affect the expression of IL-10, IL-1ra, or CD206 in IL-4-treated THP-1 cells.

Conclusions

Zol enhanced LPS-induced M1, but not M2, macrophage polarization through the NLRP3 inflammasome-dependent pathway, resulting in the production of inflammatory cytokines in THP-1 cells.

Anti-inflammatory effect of polydeoxyribonucleotide on zoledronic acid-pretreated and lipopolysaccharide-stimulated RAW 264.7 cells

Bisphosphonates are generally used as therapeutic agents for bone diseases. However, previous reports on bisphosphonates-related osteonecrosis of the jaw (BRONJ) demonstrated that inflammation triggers and worsens the disease. Recently, polydeoxynucleotide (PDRN), an A_2A receptor agonist, has been suggested for the treatment of various diseases and broadly studied for its anti-inflammatory effect. The present study aimed to measure the effect of PDRN on macrophage cells treated with zoledronic acid (ZA) and lipopolysaccharide (LPS). Macrophage cells were cultured with ZA for 24 h, following which they were stimulated with LPS in the presence or absence of varying concentrations of PDRN for 24 h. The cell viability and nitric oxide (NO) production of the cells were analyzed. In addition, protein expression levels were quantified by western blotting. Cell viability was compromised and NO was overexpressed by ZA and LPS stimulation. However, under ZA and LPS stimulation cell viability was enhanced, and NO production, and inducible nitric oxide synthase, interleukin (IL)-1β, -6, and tumor necrosis factor-α overexpression were suppressed on exposure to PDRN. A_2A receptor and vascular endothelial growth factor (VEGF) expression levels increased following PDRN treatment. These results indicate that PDRN treatment of macrophages inhibits the inflammatory cytokines induced by ZA and LPS stimulation. It was hypothesized that the inflammatory cytokines were inhibited through A_2A activation by PDRN. In addition, increased VEGF expression may contribute to increased vascularization and subsequently improve the pathological condition in BRONJ. As inflammation and LPS may stimulate the occurrence of BRONJ, the present study postulated that PDRN is possibly a candidate for the therapeutic management of BRONJ by decreasing inflammation and increasing vascularization.

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

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

Osteonecrosis of the jaws (ONJ) in mice after extraction of teeth with periradicular disease

Osteonecrosis of the jaws (ONJ) is a complication of antiresorptive medications, such as denosumab or bisphosphonates, prescribed to patients with bone malignancy or osteoporosis. The most common instigating local factor in ONJ pathogenesis is tooth extraction. However, in adults the great majority of teeth are extracted due to dental disease. Here, we have investigated alveolar bone healing after extraction of healthy teeth or teeth with naturally occurring periradicular disease in mice treated with high dose zoledronic acid (ZA), a potent bisphosphonate, or OPG-Fc, a RANKL inhibitor. C57BL/6 mice were treated for eight weeks and in vivo micro-CT was performed to identify spontaneously occurring periradicular lesions around the roots of maxillary molars. Then, extractions of molars with and without dental disease were performed in all groups. Four weeks later, animals were euthanized and maxillae were dissected and analyzed. Clinically, all vehicle animals with extraction of healthy or diseased teeth, and most OPG-Fc or ZA animals with extraction of healthy teeth showed normal mucosal healing. On the contrary, most animals with OPG-Fc or ZA treatment and extraction of diseased teeth demonstrated impaired healing with visible mucosal defects. Radiographically, bone socket healing was significantly compromised in OPG-Fc and ZA-treated mice with periradicular disease in comparison to other groups. Histologically, all vehicle animals showed normal mucosal healing and socket remodeling. OPG-Fc and ZA animals with extraction of healthy teeth showed normal mucosal healing, woven bone formation in the socket, and decreased remodeling of the original socket confines. OPG-Fc and ZA animals with extraction of diseased teeth showed mucosal defects, persistent prominent inflammatory infiltrate, bone exposure and areas of osteonecrosis. These findings support that dental disease is critical in the pathogenesis of ONJ, not only as the instigating cause for tooth extraction, but also as a compounding factor in ONJ development and pathophysiology.

Histopathological features of bisphosphonates related osteonecrosis of the jaw in rats with and without vitamin d supplementation

OBJECTIVE

Aim of this study was to investigate the effect of vitamin-D3 on the osteonecrosis of bone that was induced after tooth extraction was conducted on rats that were given zoledronic acid (Z.A).

MATERIAL AND METHODS

Animals were divided into four groups. Two of the experimental groups were divided into two subgroups, third study group was not divided into subgroups, and control group was divided into three subgroups. Z.A was administered twice per week over the course of 7 weeks, dexamethasone was administered twice a week during the 5th-6th-7th weeks to all groups. Dental extraction was performed by drilling around the tooth at 7th week. In study-group-1; vitamin-D was administered twice per week during the 5th-6th-7th weeks. In study-group 2; vitamin-D was administered twice per week during the 8th-9th-10th weeks. In study-group-3; vitamin-D was administered twice per week during the 15th-16th-17th weeks. The animals were sacrificed at 10th-15th-17th weeks, and histologic samples were taken.

RESULTS

Postoperative-15-group had a lower osteoblast number, which was statistically significant as compared to preoperative-15 and control-15-group. Control-10-group showed significantly lower osteoclast number in comparison to preoperative-10 and postoperative-10-group. Osteoclast number was significantly higher in the osteonecrosis-17-group as compared to control-17-group. Preoperative-10-group showed significantly higher inflammation in comparison to control-10-group. Postoperative-15-group had a lower histologic osteonecrosis, which was statistically significant as compared to the control-15-group. Macroscopic osteonecrosis was significantly higher in the control-17-group in comparison to the osteonecrosis-17-group.

CONCLUSIONS

We concluded that there are some proofs for the treatment of BRONJ with systemic using of vitamin-D.

Introducing a protocol to create bisphosphonate-related osteonecrosis of the jaw in rat animal model

OBJECTIVE

Previously published animal investigations on bisphosphonate-related osteonecrosis of the jaws (BRONJ) showed a variety of methods for BRONJ induction and inconsistent findings. The aim of present study was to develop a reliable protocol for BRONJ induction in rat animal model.

SUBJECTS AND METHODS

In a pilot study, 64 rats were randomly divided into 4 groups and 16 subgroups (each containing 2 experimental and 2 control rats) based on the timing of tooth extraction and euthanasia. The experimental and control rats received intraperitoneal injection of 0.06 mg/kg zoledronate and saline, respectively, once a week until sacrificed, and evaluated for presence of bone exposure clinically, and osteonecrosis and new bone formation histologically. The protocol that successfully produced BRONJ in pilot study was tested in a randomized controlled experimental investigation using 45 rats.

RESULTS

In pilot investigation, the highest rate of BRONJ was obtained after four weekly zoledronate injections, at least 4 weeks after tooth extraction. The randomized controlled experimental study verified this finding with a success rate of 83%, and also showed that more prolongation of zoledronate therapy did not increase the BRONJ rate.

CONCLUSION

The protocol developed in the present study could be used reliably for future BRONJ investigations on rats.

Medication-Related Osteonecrosis of the Jaw: Basic and Translational Science Updates

In the late 1990s and the early 2000s, bisphosphonates had become the clinical pillar of excellence for treating metabolic bone disease, and thus their connection with osteonecrosis of the jaw (ONJ) caused significant concern. Over the past decade, progress has been made in understanding what is now referred to as medication-related ONJ (MRONJ), because of its connections to agents other than bisphosphonates, although in many respects the progress has been slow. This review highlights the key basic science and translational (animal) studies in the area of MRONJ and suggests areas of focus as the field moves into the next decade.

Impact of Actinomyces naeslundii on bisphosphonate-related osteonecrosis of the jaws in ovariectomized rats with periodontitis

Bisphosphonates-related osteonecrosis of the jaws (BRONJ) is a severe complication of BPs therapy with unknown pathogenesis. This study aimed to evaluate the impact of Actinomyces naeslundii (A. naeslundii) on the progression of BRONJ in ovariectomized (OVX) rat model with periodontal diseases. Sixty rats were randomly assigned into four groups. All rats underwent bilateral ovariectomy. Six weeks after surgery, animals with periodontitis induced by ligature placement were administrated with normal saline (NS), NS &A. naeslundii inoculation, zolecdronic acid (ZA) and ZA &A. naeslundii inoculation for 12 weeks, respectively. Loads of total bacteria and A. naeslundii in the mouth were assessed by real time PCR. After sacrifice, the mandibles were harvested for micro-computed tomography (micro-CT) and histological examination. Real-time PCR demonstrated that A. naeslundii was not routinely found in the rats and ZA treatment did not promote its accumulation. Micro-CT examination disclosed that ligature placement induced significant alveolar bone loss, which was greatly attenuated by ZA treatment and aggravated by A. naeslundii. Histological assessment demonstrated that ZA treatment increased the risk of developing BRONJ-like disease but this condition was not worsen with the presence of A. naeslundii. Our study suggested that oral A. naeslundii inoculation aggravated periodontal disease but not BRONJ in our animal model.

Zoledronate induces osteonecrosis of the jaw in sheep

INTRODUCTION

The treatment of bisphosphonate-related osteonecrosis of the jaw has become routine in maxillofacial hospitals. However, the etiopathology has not yet been fully understood. The aim of this study was to develop a large animal model for medication-related osteonecrosis of the jaw (MRONJ).

MATERIAL AND METHODS

Eight Swiss mountain sheep were randomly assigned into two groups. Group I received 0.075 mg/kg zoledronate (ZOL) intravenously every third week for 16 weeks. After 16 weeks, extraction of the first and second lower left premolar was performed. Group II underwent surgery and no ZOL was administered. After surgery, Group I continued to receive ZOL infusions; after 16 weeks, all animals were euthanized. The jaw bones were investigated macroscopically, radiographically (computed tomography) and histologically.

RESULTS

Osteonecrosis of the jaw was observed at all extraction sites in all the animals receiving ZOL, and at none of the sites in animals without ZOL. All ZOL-treated animals spontaneously developed exposed bone lesions in the oral cavity at sites where no surgical intervention was performed. CT imaging shows persistent alveolar extraction sockets 16 weeks after surgery in all animals of the ZOL-group, and healed alveolar extraction sockets in non-ZOL-treated animals.

CONCLUSION

Sheep treated with ZOL reproducibly demonstrated osteonecrosis of the jaw after tooth extraction, and spontaneous development of exposed bone in the oral cavity at sites where no manipulation was performed. This animal model can be used for further research in the fields of BP-ONJ etiopathology, oral implantology, bone and fracture healing and periodontology.

RANK/RANKL/OPG signaling pathways in necrotic jaw bone from bisphosphonate-treated subjects

Osteonecrosis of the jaw (ONJ) is a chronic complication affecting long-term bisphosphonate-treated subjects, recognized by non-healing exposed bone in the maxillofacial region. The pathophysiological mechanism underlying ONJ has not been fully elucidated. The aim of the present study was to investigate the role of RANK/RANKL/OPG signaling pathway and, in parallel, to evaluate angiogenic and matrix mineralization processes in jaw bone necrotic samples obtained from bisphosphonate-treated subjects with established ONJ. Necrotic bone samples and native bone samples were processed for Light and Field Emission in Lens Scanning Electron Microscope (FEISEM) analyses, for Real-Time RT-PCR to evaluate the gene expression of TNFRSF11A (RANK), TNFSF11 (RANKL), and TNFSF11B (OPG) and for immunohistochemical analyses of VEGF and BSP expression. Morphological analyses performed by Light microscope and FEISEM show empty osteocytic lacunae and alteration of lamellar organization with degradation of the mineralized bone matrix in necrotic bone samples. A significant increase in TNFRSF11A, TNFSF11, TRAF6 and NFAT2 gene expression, and a reduction of TNFSF11B gene transcription level compared is also showed in necrotic bone compared to control samples. No significant difference of VEGF expression is evidenced, while lower BSP expression in necrotic bone compared to healthy samples is found. Even if the pathogenesis of bisphosphonate-associated ONJ remains unknown, a link between oral pathogens and its development seems to exist. We suppose lipopolysaccharide produced by bacteria colonizing and infecting necrotic bone and the surrounding viable area could trigger RANK/RANKL/OPG signaling pathway and, in this context, osteoclasts activation could be considered as a protective strategy carried out by the host bone tissue to delimitate the necrotic area and to counteract infection.

Is bisphosphonate-related osteonecrosis of the jaw an infection? A histological and microbiological ten-year summary

The role of infection in the etiology of bisphosphonate-related osteonecrosis of the jaw (BRONJ) is poorly understood. Large-scale epidemiological descriptions of the histology and microbiology of BRONJ are not found in the literature. Herein, we present a systematic review of BRONJ histology and microbiology (including demographics, immunocompromised associations, clinical signs and symptoms, disease severity, antibiotic and surgical treatments, and recovery status) validating that infection should still be considered a prime component in the multifactorial disease.