Diabetes mellitus and corticotherapy as risk factors for alendronate-related osteonecrosis of the jaws: a study in Wistar rats

The effects of sodium alendronate on socket healing after tooth extraction: a systematic review of animal studies

The aim of this systematic review was to answer the following question: "Does alendronate, a nitrogen-containing bisphosphonate, improve or impair alveolar socket healing after tooth extraction in animal models"? To this end, a systematic review of the literature was carried out in PubMed, Scopus, LILACS, Web of Science, as well as in the gray literature up to May 2023. Preclinical studies that evaluated alveolar healing after tooth extraction and the intake of sodium alendronate compared with placebo were included. Two investigators were responsible for screening the articles independently, extracting the data, and assessing their quality through the SYRCLE's RoB tool for randomized trials in animal studies. The study selection process, study characteristics, risk of bias in studies, impact of alendronate on bone healing, and certainty of evidence were described in text and table formats. Methodological differences among the studies were restricted to the synthesis methods. The synthesis of qualitative results followed the Synthesis Without Meta-analysis (SWiM) reporting guideline. From the 19 included studies, five were considered to have low risk, three were of unclear risk, and eleven presented a high risk of bias. The studies were considered heterogeneous regarding alendronate posology, including its dosage and route of administration. Furthermore, a variety of animal species, different age ranges, diverse teeth extracted, and exposure or not to ovariectomy contributed to the lack of parity of the selected studies. Our results indicated that alendronate monotherapy negatively affects the early phase of wound healing after tooth extraction in preclinical studies, suggesting that the bone resorption process after tooth extraction in animals treated with alendronate might impair the bone healing process of the extraction socket. In conclusion, alendronate administration restrains bone resorption, thereby delaying alveolar socket healing . Future studies should be conducted to validate these findings and to better understand the effects of alendronate therapy on oral tissues.

Rodents as an animal model for studying tooth extraction-related medication-related osteonecrosis of the jaw: assessment of outcomes

OBJECTIVE

To assess the outcomes of several rodent animal models for studying tooth extraction-related medication-related osteonecrosis of the jaw (MRONJ).

DESIGN

After a search of the databases, 2004 articles were located, and 118 corroborated the inclusion factors (in vivo studies in rodents evaluating tooth extraction as a risk factor for the development of MRONJ).

RESULTS

Numerous studies attempting to establish an optimal protocol to induce MRONJ were found. Zoledronic acid (ZA) was the most used drug, followed by alendronate (ALN). Even when ZA did not lead to the development of MRONJ, its effect compromised the homeostasis of the bone and soft tissue. The association of other risk factors (dexamethasone, diabetes, and tooth-related inflammatory dental disease) besides tooth extraction also played a role in the development of MRONJ. In addition, studies demonstrated a relationship between cumulative dose and MRONJ.

CONCLUSIONS

Both ZA and ALN can lead to MRONJ in rodents when equivalent human doses (in osteoporosis or cancer treatment) are used. Local oral risk factors and tooth-related inflammatory dental disease increase the incidence of MRONJ in a tooth extraction-related rodent model.

Effect of tyrosine kinase inhibitor sunitinib on tissue repair at tooth extraction sites

BACKGROUND

Both zoledronic acid, a potent bisphosphonate, and the antiangiogenic drug sunitinib are included in anticancer protocols and have also been associated with jaw osteonecrosis. Our aim was to compare the effect of these drugs on tissue repair at tooth extraction sites.

METHODS

Wistar rats were allocated into four groups: (1) sunitinib; (2) sunitinib/zoledronic acid; (3) zoledronic acid; (4) control group. The animals underwent tooth extractions and maxillae were macro- and microscopically analyzed.

RESULTS

On macroscopic evaluation, the zoledronic acid group showed a significantly higher frequency of oral mucosal lesion; lesions in the sunitinib/zoledronic acid group were larger, albeit not significantly so. The sunitinib/zoledronic acid group had significantly less epithelium than the zoledronic acid and control group, but showed no significant difference compared to the sunitinib group. The sunitinib/zoledronic acid and zoledronic acid groups did not differ from each other, but had significantly less connective tissue and more non-vital bone and microbial colonies than sunitinib and control groups, whereas these latter two groups did not significantly differ from each other. Vital bone and inflammatory infiltrate did not significantly differ between groups.

CONCLUSION

Sunitinib alone is not associated with non-vital bone, whereas the sunitinib/zoledronic acid combination and zoledronic acid alone are.

Medication-related osteonecrosis of the jaw, a risk to reassess in osteoporotic patients

INTRODUCTION

The use of antiresorptive drugs concerns many medical specialties either in relation to their prescription for osteoporosis or cancer, or in relation to the treatment of their side effects. In the literature, less than 10% of medication-related osteonecrosis of the jaw are related to patients treated for osteoporosis, while 90% are found in patients treated for cancer. Despite the increasing number of osteoporotic patients taking high doses of antiresorptive drugs, only few studies describe this topic. The main aim of this study was to highlight the occurrence of medication-related osteonecrosis of the jaw in osteoporotic patients compared to cancer patients. The second aim was to highlight risk factors in the two groups, to try to understand the high number of osteoporotic patients in our population.

MATERIALS AND METHODS

A retrospective study was conducted between December 2004 and March 2021 to identify all cases of medication-related osteonecrosis of the jaw in our department with emphasis on the osteoporotic population. Demographic, systemic and local risk factors were collected as well as the type, dose and duration of the anti-resorptive drugs treatment. Evolution and follow-up were also recorded.

RESULTS

One hundred sixty five patients presented with medication-related osteonecrosis of the jaw, of whom 67 (40,6%) were osteoporotic. Seventeen (25,4%) patients were males and 50 females (74,6%). Risk factors were tobacco consumption (28,4%), anemia (20,9%), alcohol consumption (19,4%). Use of corticoids or anticoagulant/antithrombotic therapy was related in 20,9% and 16,4%, respectively. The mean age at MRONJ diagnosis was 74,4 (50-98). The mean follow up time was 23,7 months (1-110).

CONCLUSION

Unlike the literature where medication-related osteonecrosis of the jaw in osteoporotic patients represents less than 10%, the rate in our series was much higher and represents 40% of the patients. This highlights the importance of a complete dental examination before and during antiresorptive drugs treatment, even in the case of osteoporotic patients.

The effects of metformin and alendronate in attenuating bone loss and improving glucose metabolism in diabetes mellitus mice

Background: To explore the anti-osteoporosis and anti-diabetes effects and potential underlying mechanisms of treatment with metformin and alendronate in diabetes mellitus mice.

Methods: Eight-week-old C57 BL/KS db/db and db/+ female mice were evaluated according to the following treatment group for 12 weeks: control group, diabetes mellitus group, diabetes mellitus with metformin group, diabetes mellitus with Alendronate group, diabetes mellitus with metformin plus alendronate group. Glucose level, glucose tolerance test, bone mineral density, bone microarchitecture, bone histomorphometry, serum biomarkers, and qPCR analysis.

Results: Combined metformin and alendronate can improve progression in glucose metabolism and bone metabolism, including blood glucose levels, blood glucose levels after 4 and 16 hours fasting, glucose tolerance test results, insulin sensitivity and reduces bone loss than the diabetes group. The use of alendronate alone can increase significantly serum glucagon-like peptide-1 levels than the diabetes group. The use of metformin alone can improve bone microstructure such as Tb.Sp and Tb.N of spine in diabetic mice.

Conclusion: The combined use of alendronate and metformin has an anti-diabetes and anti-osteoporotic effect compared with diabetic mice, but they appear to act no obvious synergistically between alendronate and metformin.

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.

Effect of continuous and intermittent sodium alendronate oral dosing on post-extraction alveoli healing in rats

OBJECTIVE

This study aimed to compare alveolar healing after tooth extraction in two experimental rat models using continuous or discontinuous dosing of sodium alendronate (ALN).

DESIGN

Forty-eight male Wistar rats were divided into eight experimental groups (n = 6/group) and administered ALN (2.5, 5.0, or 7.5 mg/kg) by gavage, weekly, either intermittently or following a continuous regimen (2.5, 5.0, or 7.5 mg/kg) before tooth extraction. The positive control rats were administered zoledronic acid (ZA; 0.2 mg/kg, intravenous), whereas negative control rats received sterile saline (0.9% NaCl, gavage).

RESULTS

Only the ZA-treated animals showed a larger radiolucent extraction site area compared to the saline group (p = 0.007). Small areas of bone tissue filling the alveoli were visualized in the 7.5 mg/kg continuous ALN group and compared with the saline group (p < 0.001). Increased amounts of empty osteocyte lacunae (p < 0.001) and osteoclasts with signs of apoptosis (p = 0.004) were observed in the continuous ALN groups (2.5, 5.0, and 7.5 mg/kg) compared with the saline group. Increased immunolabeling for TNF-α was observed in the 7.5 mg/kg discontinuous ALN group and all continuous ALN groups compared with the saline group (p < 0.001). The number of tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts was higher in the two continuous ALN groups (5.0 and 7.5 mg/kg) than in the saline group (p < 0.001).

CONCLUSIONS

Continuous administration of ALN impaired post-extraction alveolar bone healing in rats; however, discontinuation of ALN administration before tooth extraction allowed for adequate post-dental extraction alveolar healing.

Tooth extraction in mice administered zoledronate increases inflammatory cytokine levels and promotes osteonecrosis of the jaw

INTRODUCTION

Osteonecrosis of the jaw (ONJ) occurring after invasive dental treatment often adversely affects patients' activities of daily living. Long-term administration of strong anti-bone resorptive agents such as bisphosphonates prior to invasive dental treatment is considered an ONJ risk factor; however, pathological mechanisms underlying ONJ development remain unclear.

MATERIALS AND METHODS

We developed an ONJ mouse model in which a tooth is extracted during treatment with the bisphosphonate zoledronate.

RESULTS

We observed induction of apoptosis in osteocytes, resulting in formation of empty lacunae in jaw bones at sites of tooth extraction but not in other bones of the same mice. We also observed elevated levels of inflammatory cytokines such as TNFα, IL-6 and IL-1 in jaw bone at the extraction site relative to other sites in zoledronate-treated mice. We also report that treatment in vitro with either zoledronate or an extract from Porphyromonas gingivalis, an oral bacteria, promotes expression of inflammatory cytokines in osteoclast progenitor cells. We demonstrate that gene-targeting of either TNFα, IL-6 or IL-1 or treatment with etanercept, a TNFα inhibitor, or a neutralizing antibody against IL-6 can antagonize ONJ development caused by combined tooth extraction and zoledronate treatment.

CONCLUSIONS

Taken together, the cytokine storm induced by invasive dental treatment under bisphosphonate treatment promotes ONJ development due to elevated levels of inflammatory cytokine-producing cells. Our work identifies novel targets potentially useful to prevent ONJ.

Morphological and immunohistochemical features of tooth extraction sites in rats treated with alendronate, raloxifene, or strontium ranelate

OBJECTIVE

The aim of this study was to evaluate morphological and immunohistochemical features of tooth extraction sites in rats subjected to different antiresorptive drugs.

MATERIALS AND METHODS

Wistar rats were allocated into 4 groups according to the treatment: (1) alendronate, (2) raloxifene, (3) strontium ranelate, and (4) control. The animals underwent tooth extraction (60th day of treatment) and afterwards were euthanized (90th day of treatment). Tooth extraction sites were analyzed by means of scanning electron microscopy (SEM), hematoxylin-eosin staining (H&E), and immunohistochemical staining (RANKL and OPG).

RESULTS

On H&E analysis, the alendronate group showed greater amounts of non-vital bone, biofilm, inflammatory infiltrate and root fragment, and smaller amount of vital bone. The strontium ranelate group showed great amount of non-vital bone. This group also had lower levels of OPG, while the alendronate group showed lower OPG and RANKL than the other groups. On SEM analysis, the alendronate group showed a considerable number of microcracks on the alveolar bone surface and few Howship lacunae and lack of bone cells as well. The raloxifene, strontium ranelate, and control groups showed a large number of bone cells and Howship lacunae on the bone surface and few microcracks.

CONCLUSION

Alendronate therapy is associated with macro- and microscopic features of medication-related osteonecrosis of the jaw at tooth extraction sites, whereas raloxifene therapy is not, and strontium ranelate therapy is associated with non-vital bone.

CLINICAL RELEVANCE

Osteonecrosis of the jaws is a serious side effect of alendronate therapy, where tooth extraction is a major risk factor. Considering the significant number of patients undergoing antiresorptive therapies worldwide, the present study investigated whether raloxifene and strontium ranelate interfere with bone repair after tooth extraction in a similar way to bisphosphonates.

Review and update on drugs related to the development of osteonecrosis of the jaw

Background

Medication-related osteonecrosis of the jaw (MRONJ) is a rare, but serious adverse effect of certain drugs, of which bisphosphonates are the most widely known. This pathology is also associated with other medications such as the biologic antiresorptive agent, denosumab and some antiangiogenics such as sunitinib, bevacizumab or aflibercept. Very recently, new medications have also been associated with osteonecrosis of the jaw (ONJ). The objectives were to update the list of medications associated with ONJ, to analyze the fundamental aspects of this list and to describe the level of evidence available.

Material and Methods

A narrative bibliographic review was made, using the PubMed-MedLine, DOAJ and SCIELO databases. Additional information was obtained through the online Medication Information Centre of the Spanish Agency of Medicines and Medical Devices (AEMPS – CIMA), the websites of the US Food & Drugs Administration (Drugs@FDA) and the European Medicines Agency (EMA).

Results

The latest drugs identified as potential facilitators of this pathology include a number of anti-VEGF based antiangiogenic drugs and anti-TKI and different types of immunomodulators. Neither the level of evidence in this association nor the risk are equal for all these drugs. On the other hand, over the coming years, new drugs will be marketed with similar action mechanisms to those that are recognized as having this adverse effect.

Conclusions

No effective therapy is currently known for the treatment of ONJ. Therefore, in order to prevent new cases of MRONJ, it is essential for all oral healthcare professionals to be fully up-to-date with the etiopathogenic aspects of this pathology and to be aware of those drugs considered to be a risk.

Key words:Osteonecrosis of the jaw, MRONJ, bisphosphonates, antiresorptives, antiangiogenics.

Refractory healing after surgical therapy of osteonecrosis of the jaw: associated risk factors in aged patients

Purpose: Osteonecrosis of the jaw (ONJ), both medication-related and non medication-related, mainly occurs in aged patients. It needs surgical intervention. Refractory healing after an operation of ONJ can significantly lower the quality of life of elderly patients. The purpose of this study was to determine risk factors associated with refractory healing in aged patients.

Patients and methods: We performed a retrospective study of ONJ in aged patients who underwent surgical treatments in a single institute during a 12-year period. Multiple logistic regression analysis was used to determine independent risk factors associated with refractory healing.

Results: A total of 122 patients were included. Of them, 25 patients were identified as the refractory group and 97 patients as the control group. Diabetes mellitus (DM) (AOR=5.03, 95% CI: 1.74–14.52) and glucocorticoid administration (AOR=7.97, 95% CI: 2.52–25.23) were found to be significant risk factors for refractory healing of ONJ.

Conclusion: DM and medication of glucocorticoid might be risk factors for refractory healing of ONJ.

Increased risk of bisphosphonate-related osteonecrosis of the jaw in patients with Sjögren's syndrome: nationwide population-based cohort study

OBJECTIVE

The aim of this study was to explore whether patients with Sjögren's syndrome (SS) were susceptible to bisphosphonate (BP)-related osteonecrosis of the jaw (BRONJ) after tooth extraction in the entire population of Taiwan.

DESIGN

A nationwide population-based retrospective cohort study.

SETTING

Data were extracted from Taiwan's National Health Insurance Research Database (NHIRD).

METHODOLOGY

Medical conditions for both the study and control group were categorised using the International Classification of Diseases, 9th Revision. ORs and 95% CIs for associations between SS and osteonecrosis of the jaw (ONJ) were estimated using Cox regression.

RESULTS

Overall, 13 398 patients diagnosed with SS were identified from the NHIRD. An additional 53 592 matched patients formed the control group. At the 3-year follow-up, patients with SS started to exhibit a significantly increased cumulative risk of developing BRONJ compared with that of patients without SS (log rank test <0.001). At the end of the follow-up period, patients with SS exhibited a significantly increased incidence of ONJ compared with that of the controls (0.08%vs0.03%, p=0.017). The Cox regression model showed that patients with SS also exhibited a significantly increased risk of developing BRONJ compared with that of the patients without SS (adjusted HR=7.869, 95% CI 3.235 to 19.141, p<0.001).

CONCLUSION

Patients with SS exhibit an increased risk of developing BRONJ after tooth extraction. BPs should be used with caution in patients with SS.

Knowledge and Attitude of Dentists Regarding Patients Undergoing Bisphosphonate Treatment: a Comparative Questionnaire

Background: Osteonecrosis of the jaw is an uncommon but serious complication related to oral and intravenous bisphosphonate (BP) therapy. Its pathogenesis is not well understood, and there are no universal protocols accepted to treat it.

The aim of our study was to use the same questionnaire as four years ago to evaluate the awareness of dentists in Tîrgu Mureș regarding the dental treatments that can be applied in patients on BP therapy, and to assess how their knowledge on the subject has evolved over these years.

Material and method: We used the same questionnaire-based study as four years ago among dentists in Tîrgu Mureș, raising important issues such as: is the patient asked about current or previous treatments with BPs, do they perform surgical treatment in these patients, do they know under what conditions they can perform this treatment, or do they deem it necessary to contact the prescriber before surgical treatment.

Results: One-hundred twenty questionnaires were returned. The majority of respondents (n = 113, 94.2%) included the question regarding the use of BPs in their medical records. Of all respondents, 48 (40%) perform dental or surgical treatments on patients undergoing BP therapy, 68 (56.7%) do not perform dental or surgical treatments on these patients, and four of the respondents (3.3%) did not know the answer. One hundred (83.3%) respondents always contact the prescriber prior to surgery in these patients, regardless of how BPs are administered.

Conclusions: According to the findings of the present study, many of the respondent doctors have heard about BPs and their complications, but they are not aware of the fundamental concepts of bisphosphonate-related osteonecrosis of the jaw prevention and treatment protocols. In the absence of appropriate protocols, the quality of life of these patients is compromised.

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.

Dental extraction following zoledronate, induces osteonecrosis in rat's jaw

BACKGROUND

Bisphosphonate-Related Osteonecrosis of the Jaw (BRONJ) is clinically characterized by the presence of exposed bone in the oral cavity that persists for more than eight weeks. Previous attempts to establish an animal model have not sufficiently considered disease features. Our aim was to establish an inexpensive and replicable animal model that develops BRONJ in a short time.

MATERIAL AND METHODS

Thirty-two male Wistar rats were randomly divided into two groups: control and experimental. In the experimental group, we administered 0.06mg/kg intraperitoneal dose of zoledronic acid (ZA) 7 and 14 days prior to maxillary second molar extraction. At two, four and six weeks after tooth extraction, the animals were euthanized, and we dissected the maxilla following histological procedures. We stained serial slides with hematoxylin and eosin and Masson's trichrome. The samples were harvested for macroscopic, radiologic and histological evaluation of bone changes.

RESULTS

At two weeks postextraction, we observed exposed necrotic bone in dental socket areas in experimental groups. Radiological analysis revealed osteolytic lesions accompanied by extensive destruction and sequestrum formation in the same group. Histological examination confirmed the absence of necrotic bone in control groups in contrast with the experimental groups. The percentage of empty lacunae and the number of osteoclasts and the necrotic bone area were significantly increased (p<0.05) in the experimental groups.

CONCLUSIONS

The animal model using ZA administration to prior dental extraction successfully mimicked human BRONJ lesions. Also, the model was easily replicated, inexpensive and showed different features than other previous BRONJ models.

Diseases having an influence on inhibition of angiogenesis as risk factors of osteonecrosis of the jaw

Objectives

The objective of this study was to retrospectively investigate the association of diseases having an influence on inhibition of angiogenesis such as hypertension, diabetes mellitus type II, hypercholesterolemia, and rheumatoid arthritis (RA) with the development of osteonecrosis of the jaws.

Materials and Methods

The 135 patients were allocated into 4 groups of bisphosphonate-related osteonecrosis of the jaw (BRONJ) group (1A); non-BRONJ group (1B); osteonecrosis of the jaw (ONJ) group (2A); and control group (2B), according to histologic results and use of bisphosphonate. This retrospective study was conducted with patients who were treated in one institute from 2012 to 2013. Fisher's exact test and logistic regression analysis were used to analyze the odds ratios of diseases having an influence on inhibition of angiogenesis for development of ONJ.

Results

The effects of diabetes and hypertension were not statistically significant on development of ONJ. When not considering bisphosphonate use, RA exhibited a high odds ratio of 3.23 (P=0.094), while hyperlipidemia showed an odds ratio of 2.10 (P=0.144) for development of ONJ. More than one disease that had an influence on inhibition of angiogenesis showed a statistically significant odds ratio of 2.54 (P=0.012) for development of ONJ.

Conclusion

Patients without diseases having an influence on inhibition of angiogenesis were at less risk for developing ONJ.

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

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

Effect of hyperbaric oxygen therapy on tooth extraction sites in rats subjected to bisphosphonate therapy-histomorphometric and immunohistochemical analysis

OBJECTIVE

This study aimed to investigate the effect of hyperbaric oxygen therapy (HBOT) on tooth extraction sites in rats treated with bisphosphonate.

MATERIALS AND METHODS

Rats were treated with zoledronic acid, subjected to tooth extractions and allocated into groups: (1) 7 days of HBOT, (2) 14 days of HBOT, (3) 7-day control, and (4) 14-day control. The site of tooth extractions was analyzed by histomorphometry and immunohistochemistry.

RESULTS

On macroscopic analysis, HBOT did not significantly affect bone exposure volume either at 7 or 14 days. On hematoxylin and eosin (H&E) analysis, the 14-day HBOT group showed less non-vital bone compared to both controls and 7-day HBOT group. HBOT significantly lowered expression of vascular endothelial growth factor (VEGF), receptor activator NF-kB ligand (RANKL), bone morphogenetic protein-2 (BMP-2), and osteoprotegerin (OPG) at 7 days, compared to control, whereas at 14 days, there was no significant difference for these variables.

CONCLUSION

HBOT can reduce the amounts of non-vital bone microscopically detected in tooth extraction sites of rats subjected to bisphosphonate therapy. The effect seems to occur in a dose-dependent mode. Further studies are required to clarify the mechanisms accounting for this effect.

CLINICAL RELEVANCE

Treatment of bisphosphonate-related osteonecrosis of the jaw (BRONJ) has been a challenging task, where the effectiveness of HBOT is controversial. This study reports important effects of HBOT on the maxillae of rats subjected to bisphosphonate treatment, making an important contribution to the knowledge about the applicability of HBOT in BRONJ.

Bisphosphonate Induces Osteonecrosis of the Jaw in Diabetic Mice via NLRP3/Caspase-1-Dependent IL-1β Mechanism

Diabetes mellitus is an established risk factor associated with bisphosphonate-related osteonecrosis of the jaw (BRONJ). Sustained activation of Nod-like receptor (NLR) family, pyrin domain-containing protein 3 (NLRP3) inflammasome contributes to the persistent inflammation and impaired cutaneous wound healing in diabetic mice and human. We have recently demonstrated a compelling linkage between M1 macrophages and BRONJ conditions in both murine and human diseases. The aim of this study was to determine whether NLRP3 inflammasome activation is involved in BRONJ development in diabetic mice. We showed an increased incidence of delayed oral wound healing and bone necrosis of extraction sockets in db/db mice compared with those in nondiabetic db/+ controls, which correlated with an elevated expression of NLRP3, caspase-1, and IL-1β in macrophages residing at local wounds. Constitutively, bone marrow-derived macrophages from db/db mice (db/db BMDMs) secrete a relatively higher level of IL-1β than those from db/+ mice (db/+ BMDMs). Upon stimulation by NLRP3 activators, the secretion of IL-1β by db/db BMDMs was 1.77-fold higher than that by db/+ BMDMs (p < 0.001). Systemic treatment of mice with zoledronate (Zol), a nitrogen-containing bisphosphonate, resulted in a 1.86- and 1.63-fold increase in NLRP3/caspase-1-dependent IL-1β secretion by db/+ and db/db BMDMs, respectively, compared with BMDMs derived from nontreated mice (p < 0.001). Importantly, systemic administration of pharmacological inhibitors of NLRP3 activation improved oral wound healing and suppressed BRONJ formation in db/db mice. Mechanistically, we showed that supplementation with intermediate metabolites of the mevalonate pathway, inhibitors of caspase-1 and NLRP3 activation, an antagonist for P2X7 R, or a scavenger of reactive oxygen species (ROS), robustly abolished Zol-enhanced IL-1β release from macrophages in response to NLRP3 activation (p < 0.001). Our findings suggest that diabetes-associated chronic inflammatory response may have contributed to impaired socket wound healing and rendered oral wound susceptible to the development of BRONJ via NLRP3 activation in macrophages.

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.

Diabetes as a risk factor for medication-related osteonecrosis of the jaw

Medication-related osteonecrosis of the jaw (MRONJ) is a severe devastating complication for which the exact pathogenesis is not completely understood. Multiple systemic and local factors may contribute to the development of MRONJ. A growing body of evidence supports diabetes mellitus (DM) as an important risk factor for this complication; however, the exact mechanism by which DM may promote MRONJ has yet to be determined. The current review elucidates the role of DM in the pathogenesis of MRONJ and the mechanisms by which DM may increase the risk for MRONJ. Factors related to DM pathogenesis and treatment may contribute to poor bone quality through multiple damaged pathways, including microvascular ischemia, endothelial cell dysfunction, reduced remodeling of bone, and increased apoptosis of osteoblasts and osteocytes. In addition, DM induces changes in immune cell function and promotes inflammation. This increases the risk for chronic infection in the settings of cancer and its treatment, as well as antiresorptive medication exposure, thus raising the risk of developing MRONJ. A genetic predisposition for MRONJ, coupled with CYP 450 gene alterations, has been suggested to affect the degradation of medications for DM such as thiazolidinediones and may further increase the risk for MRONJ.