Effect of zoledronate on oral wound healing in rats

The Preventive Effect of Preoperative and Postoperative Selenium on the Medication-Related Osteonecrosis of the Jaw: An Animal Study in Rats

BACKGROUND

Medication-related osteonecrosis of the jaw (MRONJ) is a condition that can occur primarily in patients undergoing or have previously undergone therapy with bisphosphonates, particularly in the presence of risk factors, such as tooth extraction (TE).

PURPOSE

This study aimed to evaluate the effect of selenium (SEL) administration on the prevention of osteonecrosis of the jaw in an MRONJ animal model.

STUDY DESIGN, SETTING, AND SAMPLE

This study was a longitudinal in vivo animal study using a TE model in a sample of 48 Wistar rats.

PREDICTOR VARIABLE

The predictor variables were SEL exposure, timing of SEL exposure, and zoledronic acid (ZOL) exposure. The animals were randomly assigned to 4 treatment groups (n = 12 per group): 1) saline (negative control), 2) ZOL (positive control), 3) SELpreop + ZOL, and 4) ZOL + SELpostop. The animals were administered saline (negative control) or ZOL (0.06 mg/kg, intraperitoneally) once a week for 5 weeks. All rats underwent TE at the end of the fifth week. SEL (0.3 mg/kg, intraperitoneally) was administered once daily for 15 days to the SELpreop + ZOL group before TE and to the ZOL + SELpostop group after TE. All animals were sacrificed at the end of the ninth week.

MAIN OUTCOME VARIABLES

The primary outcome variables were new bone area, necrotic bone area, fibrosis, new connective tissue formation, and inflammatory cell infiltration in the histopathological analysis, as well as angiogenesis and percentage of osteoblasts in the immunohistochemical analysis.

COVARIATES

There was none.

ANALYSES

Statistical analysis was conducted using the Kruskal-Wallis test, followed by post hoc Bonferroni-corrected Mann-Whitney U tests, with a significance level of P ≤ .05.

RESULTS

The new bone area was higher in the ZOL + SELpostop group (3.00 score) than in the saline group (0.58 ± 1.08 score, P < .001) and the ZOL group (0.82 ± 1.40 score, P = .001), while the necrotic bone area was lower in the ZOL + SELpostop group (0.08 ± 0.29 score) than in the ZOL group (2.82 ± 0.40 score, P < .001) and the SELpreop + ZOL group (1.67 ± 0.89 score, P = .007). The percentage of osteoblasts was higher in the ZOL + SELpostop group (18.73%) than in the saline group (8.63%, P < .001) and the ZOL group (0.07%, P < .001), and it was also higher in the SELpreop + ZOL group (18.49%) than in the ZOL group (0.07%, P < .001).

CONCLUSION AND RELEVANCE

In conclusion SEL prevents MRONJ, with postoperative SEL demonstrating greater prevention effects. Given these findings, we hypothesize that SEL exposure may decrease the risk of MRONJ.

Pathophysiology of Medication-Related Osteonecrosis of the Jaw-A Minireview

Medication-related osteonecrosis of the jaw (MRONJ) is a rare but serious adverse effect of antiresorptive medications administered for control of osseous malignancy, osteoporosis, or other bone metabolic diseases. Despite being reported in the literature two decades ago, MRONJ etiology, pathophysiology, and progression remain largely unknown, and current nonoperative or operative treatment strategies are mostly empirical. Several hypotheses that attempt to explain the mechanisms of MRONJ pathogenesis have been proposed. However, none of these hypotheses alone is able to capture the complex mechanistic underpinnings of the disease. In this minireview, we aim to highlight key findings from clinical and translational studies and propose a unifying model for the pathogenesis and progression of MRONJ. We also identify aspects of the disease process that require further investigation and suggest areas for future research efforts toward calibrating methodologic approaches and validating experimental findings. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Histopathological assessment of the preventive effect of leukocyte-platelet-rich fibrin on bisphosphonate-related osteonecrosis of the jaw following dental extraction: An animal study

Background

Leukocyte- and platelet-rich fibrin (L-PRF) could be considered a preventive measure in Bisphosphonate-Related Osteonecrosis of the Jaw (BRONJ). The present experiment aimed to assess the preventive effects of L-PRF on osteonecrosis of the jaw in rats.

Methods

In this interventional animal study with a split-mouth design, 28 rats were randomly allocated to saline (negative control), bisphosphonate (positive control), and Bis + L-PRF (case) groups. Bilateral extraction of maxillary molar teeth was performed followed by random application of L-PRF to one of the extraction sockets treated with Zoledronic acid for four weeks. Clinical occurrence of BRONJ and histopathologic evaluations were done, and data were subjected to the Kruskal-Wallis test, Mann-Whitney U test and exact Fisher test performed using SPSS 25. The significance level was set at 0.05.

Results

The application of L-PRF resulted in a 41.67% reduction in osteonecrosis centers and the number of osteoclast cells. Also, Kruskal Wallis test results showed a significant difference among the three groups regarding the frequency distribution of inflammation severity. However, no significant difference was detected regarding the frequency distribution of the blood vessels (Kruskal Wallis test, P-value = 0.649).

Conclusion

It could be inferred that possible preventive effects on the clinical occurrence of osteonecrosis could be expected from the application of L-PRF.

Intermittent parathyroid hormone enhances the healing of medication-related osteonecrosis of the jaw lesions in rice rats

Medication-related osteonecrosis of the jaw (MRONJ) is a potentially severe adverse event in patients treated with antiresorptives. Management of MRONJ is challenging, and no non-antibiotic, established medical treatment exists. Intermittent parathyroid hormone (iPTH) has been used off-label to treat MRONJ with favorable results. However, its medical efficacy has rarely been substantiated in clinical or preclinical experiments. Using a validated rice rat, infection-based model of MRONJ, we evaluated the effects of iPTH on established MRONJ. We hypothesize that iPTH contributes to MRONJ resolution by enhancing alveolar bone turnover and healing oral soft tissues. Eighty-four rice rats began a standard rodent chow diet at age 4 weeks to induce localized periodontitis. Rats were simultaneously randomized to receive saline (vehicle, VEH) or zoledronic acid (ZOL, 80 μg/kg IV) every 4 weeks. Oral exams were conducted bi-weekly to assign a gross quadrant grade (GQG, 0-4) to evaluate any lesion at the lingual aspect of the interdental space between maxillary molar (M2) and M3. 14 of 20 VEH-treated rice rats (70%) developed maxillary localized periodontitis with GQG 2-3 after 30 ± 10 weeks of saline. Additionally, 40 of 64 ZOL-treated rice rats with periodontitis developed MRONJ-like lesions after 30 ± 10 weeks of ZOL treatment. Rice rats with localized periodontitis or MRONJ-like lesions were treated with saline or iPTH (40 μg/kg) subcutaneously (SC) 3 times/week For 6 weeks until euthanasia. We found that iPTH -treated ZOL rats had a lower prevalence of MRONJ (p < 0.001), with lower severity extent of oral lesions (p = 0.003) and percentage of empty osteocyte lacunae (p < 0.001). ZOL rats treated with iPTH displayed a higher osteoblast surface (p < 0.001), more osteoblasts (p < 0.001), higher osteoclast surface (p < 0.001) and more osteoclasts (p = 0.002) at alveolar bone surfaces than ZOL/VEH rats. Greater gingival epithelial thickness and epithelial cell proliferation rate was found in the oral mucosa and gingiva of ZOL/PTH rats than in ZOL/VEH rats (p < 0.001). Our data suggest that iPTH is an efficacious non-operative medicinal therapy that accelerates oral healing and enhances the resolution of MRONJ lesions in ZOL-treated rice rats.

Dietary nitrate improves jaw bone remodelling in zoledronate-treated mice

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a serious complication that occurs in patients with osteoporosis or metastatic bone cancer treated with bisphosphonate. There is still no effective treatment and prevention strategy for BRONJ. Inorganic nitrate, which is abundant in green vegetables, has been reported to be protective in multiple diseases. To investigate the effects of dietary nitrate on BRONJ-like lesions in mice, we utilized a well-established mouse BRONJ model, in which tooth extraction was performed. Specifically, 4 mM sodium nitrate was administered in advance through drinking water to assess the short- and long-term effects on BRONJ. Zoledronate injection could induce severe healing inhibition of the tooth extraction socket, while addition of pretreating dietary nitrate could alleviate the inhibition by reducing monocyte necrosis and inflammatory cytokines production. Mechanistically, nitrate intake increased plasma nitric oxide levels, which attenuated necroptosis of monocytes by downregulating lipid and lipid-like molecule metabolism via a RIPK3 dependent pathway. Our findings revealed that dietary nitrate could inhibit monocyte necroptosis in BRONJ, regulate the bone immune microenvironment and promote bone remodelling after injury. This study contributes to the understanding of the immunopathogenesis of zoledronate and supports the feasibility of dietary nitrate for the clinical prevention of BRONJ.

[Analysis of pathological characteristics of medication-related osteonecrosis of the jaw and discussion of clinical treatment strategies based on the pathological analysis results]

OBJECTIVE

To summarize the pathological characteristics of medication-related osteonecrosis of the jaw (MRONJ) specimens after jaw curettage or jaw osteotomy treatment and to comprehensively analyze the relationship between the different pathological features, treatment methods, and treatment effects to provide new ideas for effective treatment of MRONJ in clinical work.

METHODS

The clinical and pathological data were collected from 23 patients with MRONJ who were treated with curettage (18 patients) and jaw osteotomy (5 patients) at the Department of Oral and Maxillofacial Surgery of Peking University Hospital of Stomatology between June 2014 and December 2015. The pathological characteristics of MRONJ were summarized and analyzed with treatment effects based on various surgical treatment methods. The diagnostic criteria and disease staging of MRONJ were determined according to the 2014 American Association of Oral and Maxillofacial Surgeon's Position Paper.

RESULTS

In this study, 5 patients have treated with jaw segmental osteotomy, and all of them were in stage Ⅲ; the other 18 patients were treated with jaw curettage, including 5 patients in stage Ⅱ and 13 patients in stage Ⅲ. The pathological features of MRONJ in five cases of jaw segmental osteotomy were divided into three adjacent regions from shallow to deep: inflammation region (IR), sclerosis region (SR), and bone remodeling layer (BRL). Moreover, three types of pathological features of specimens from traditional curettage were defined as type 1 (IR), type 2 (IR + SR), and type 3 (IR + SR + BRL). The pathological features of the patients treated with jaw curettage were: type Ⅰ, 38.9% (7/18); type Ⅱ, 44.4% (8/18); type Ⅲ, 16.7% (3/18). Complete healing was achieved in 5 patients treated with jaw segmental osteo-tomy. Moreover, 2 cases with type Ⅰ, 1 case with type Ⅱ, and 1 with type Ⅲ completely healed after jaw curettage, while 5 cases with type Ⅰ, 7 cases with type Ⅱ, and 2 cases with type Ⅲ experienced recurrence after surgery.

CONCLUSION

Pathological features of continuous regions of inflammation, sclerosis, and bone remodeling layer were identified from shallow to deep, based on the microscopic observation of jaw segmental osteotomy samples. Insufficient removal of the sclerotic region during jaw curettage that blocks the required blood, nutritional factors, and mesenchymal stem cells seems to be a common cause for failed treatment of MRONJ after curettage surgery.

Impacts of bisphosphonates on the bone and its surrounding tissues: mechanistic insights into medication-related osteonecrosis of the jaw

Bisphosphonates are widely used as anti-resorptive agents for the treatment of various bone and joint diseases, including advanced osteoporosis, multiple myeloma, bone metastatic cancers, Paget's disease of bone, and rheumatoid arthritis. Bisphosphonates act as an anti-osteoclast via the induction of osteoclast apoptosis, resulting in a decreased rate of bone resorption. Unfortunately, there is much evidence to demonstrate that the long-term use of bisphosphonates is associated with osteonecrosis. The pathogenesis of osteonecrosis includes the death of osteoblasts, osteoclasts, and osteocytes. In addition, the functions of endothelial cells, epithelial cells, and fibroblasts are impaired in osteonecrosis, leading to disruptive angiogenesis, and delayed wound healing. Osteonecrosis is most commonly found in the jawbone and the term medication-related osteonecrosis of the jaw (MRONJ) has become the condition of greatest clinical concern among patients receiving bisphosphonates. Although surgical treatment is an effective strategy for the treatment of MRONJ, several non-surgical interventions for the attenuation of MRONJ have also been investigated. With the aim of increasing understanding around MRONJ, we set out to summarize and discuss the holistic effects of bisphosphonates on the bone and its surrounding tissues. In addition, non-surgical interventions for the attenuation of bisphosphonate-induced osteonecrosis were reviewed and discussed.

Zoledronic Acid Deteriorates Soft and Hard Tissue Healing of Murine Tooth Extraction Sockets in a Dose-Dependent Manner

The pathophysiology, histopathology, and immunopathology of bisphosphonate-related osteonecrosis of the jaw (BRONJ) Stage 0 remain unclear. The aim of this study was to investigate the effects of high-dose bisphosphonates on tooth extraction socket healing by creating a murine model of BRONJ Stage 0-like lesions using 8-week-old female C57BL/6J mice. Zoledronic acid (Zol) was administered subcutaneously twice a week for 7 weeks at doses of 0.1 mg/kg/week (moderate dose; Zol-M), 0.5 mg/kg/week (high dose; Zol-H1), and 1.0 mg/kg/week (higher dose; Zol-H2). Saline was used as a control (VC). Both maxillary first molars were extracted 3 weeks after drug treatment. Maxillae, long bones, and sera were collected 4 weeks post-extraction (n = 7 mice/group). Microcomputed tomography, histological, immunohistochemical, and ELISA analyses were performed. A ceiling effect for Zol was noted at the Zol-H1 dose. Osseous healing of extraction sites was significantly impaired with increased necrotic bone and the number of empty lacunae in a Zol dose-dependent manner. Zol significantly decreased epithelial thickness, due to a decrease in thickness of the stratum spinosum, in both Zol-H1 and Zol-H2. Both Zol-H1 and Zol-H2 significantly suppressed the distribution of F4/80⁺ macrophages in the connective tissue of tooth extraction sockets, although gross healing appeared to be normal. Intriguingly, both Zol-H1 and Zol-H2 significantly increased the numbers of TRAP⁺ mononuclear cells and detached osteoclasts in the connective tissue and bone marrow of extraction sites compared to VC and Zol-M, correlated with serum TRAcP5b levels. The created murine model of BRONJ Stage 0-like lesions becoming more severe in a dose-dependent manner may help to understand the pathophysiology and histopathology of BRONJ Stage 0 in humans.

Effects of Soft Tissue Closure on Medication-Related Osteonecrosis of the Jaw in a Rabbit Model with Tooth Extraction: A Pilot Study

Objectives

The study investigated the effect of soft tissue closure after tooth extraction on the prevention of medication-related osteonecrosis of the jaw in a rabbit model.

Materials and Methods

Twenty female New Zealand white rabbits were randomly assigned into the experimental group administrated with zoledronic acid (ZA) and control groups treated with saline. Bilateral lower premolar extraction was performed 4 weeks after ZA/saline administration. Immediately after extraction, the wound on the right mandible was closed by suture while the other side was left open. Animals were sacrificed 4 weeks and 8 weeks after tooth extraction. Fluorochrome labeling solutions were injected subcutaneously to evaluate the bone growth rates. The mandibles were harvested and subjected for microcomputed tomography, confocal microscope, and histomorphological examinations.

Results

All extraction sites healed well without any signs of infection. Trabecular thickness (Tb.Th) was significantly higher in the ZA-treated group than in the control group at both week 4 and week 8, while no significant difference was detected in the rest of the assessed parameters. The bone growth rate in mandibles showed gradual reduction in the ZA-treated group. Histological analysis showed that at week 8, the animals in the ZA-treated group had significantly higher incidence of osteonecrosis than that in the control group, while no significance was revealed between the sutured and nonsutured side.

Conclusions

ZA treatment significantly reduces bone growth rates but does not reveal a significant effect on bone mineral density and bone microarchitecture. Soft tissue closure of the extraction socket does not reduce the incidence of ONJ in the ZA-treated rabbit model.

Medication Related Osteonecrosis of the Jaw: 2021 Position Statement of the Korean Society for Bone and Mineral Research and the Korean Association of Oral and Maxillofacial Surgeons

Antiresorptives are the most widely prescribed drugs for the treatment of osteoporosis. They are also used in malignant bone metastases, multiple myeloma, and Paget's disease, and provide therapeutic efficacy on those diseases. However, it was reported that the occurrence of osteonecrosis of the jaw (ONJ) could be related to antiresorptive exposures, and there have been many cases regarding this issue. Therefore, a clearer definition and treatment guidelines were needed for this disease. The American Society for Bone and Mineral Research and the Amnerican Association of Oral and Maxillofacial Surgeons reported statements on bisphosphonate-related ONJ (BRONJ), and a revised version was recently presented. In the revised edition, the diagnosis BRONJ was changed to medication-related ONJ (MRONJ), which reflects consideration of the fact that ONJ also occurs for denosumab, a bone resorption inhibitor of the receptor activator of the nuclear factor-κB ligand antibody family, and bevacizumab, an anti-angiogenesis inhibitor. The Korean Society for Bone and Mineral Research and the Korean Association of Oral and Maxillofacial Surgeons had collectively formed a task force for the preparation of an official statement on MRONJ based on a previous position paper in 2015. The task force reviewed current knowledge and coordinated dental and medical opinions to propose the guideline customized for the local Korean situation.

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.

Comparison of Vascular Morphometry in Jawbones and Long Bones: Micro-CT Study in a Rat Model Treated with Zoledronic Acid

The study was aimed at investigating the effect of zoledronic acid on vascular morphometry in jawbones and long bones on a rat model. Twenty-four skeletal mature Sprague-Dawley female rats were administered oncologic dose of zoledronic acid (ZA) or normal saline for 4 weeks and then subjected to tooth extraction on the mandible and maxilla and a bone defect creation on the femur. After the surgical procedures, ZA or saline treatment was continued until sacrifice at week 2, week 4, and week 8 postoperatively. Vascular perfusion with MICROFIL was performed on all the animals. Micro-CT analysis demonstrated a tendency of decreased vessel density and vessel number in ZA-treated groups but no statistical difference. In conclusion, the neovessel formation is suppressed but not significantly by ZA treatment, indicating that angiogenesis inhibition may contribute to the development of MRONJ but does not play a key role.

Gene expression analysis of fresh extraction wounds prior to onset of bisphosphonate-related osteonecrosis of the jaw-like lesions in mice: A preliminary animal study

PURPOSE

The aim of the present study was to investigate the effects of chemotherapeutic/bisphosphonate combination therapy with tooth extraction on gene expression patterns of fresh extraction wounds during initial stages prior to their diagnosis as bisphosphonate-related osteonecrosis of the jaw (BRONJ)-like lesions in mice.

METHODS

Female C57BL/6J mice were used. To create a high-prevalence BRONJ mouse model, combination therapy with the chemotherapy drug cyclophosphamide (CY) and zoledronic acid (ZA) was performed (CY/ZA). Both maxillary first molars were extracted 3 weeks after drug therapy. Saline was used as the control (VC). Soft tissues near the fresh extraction wounds were dissected at 72 h postextraction to investigate the gene expression patterns. Maxillae and long bones at 2 and 4 weeks postextraction were also analyzed.

RESULTS

CY/ZA significantly increased the relative expression levels of IL-6 and decreased those of IL-10 and IGF-1 when compared with those in VC. Moreover, CY/ZA significantly reduced the relative expression levels of CCR-7, cxcl12, cxcr4, and CD105 when compared with those in VC, whereas the level of F4/80 was significantly increased by CY/ZA. Furthermore, CY/ZA significantly decreased the relative expression levels of VEGFA, VEGFB, and VEGFC at 72 h postextraction compared with those in VC.

CONCLUSIONS

Considering that the present study lacked adequate in vitro models, CY/ZA markedly changed the gene expression patterns associated with wound healing from the initial stages prior to onset of BRONJ-like lesions, which may help us to understand the pathophysiology of BRONJ in humans.

Preventing or controlling periodontitis reduces the occurrence of osteonecrosis of the jaw (ONJ) in rice rats (Oryzomys palustris)

INTRODUCTION

Osteonecrosis of the jaw (ONJ) is an adverse event that requires association of both systemic risk factors, such as powerful anti-resorptives (pARs; e.g. zoledronic acid [ZOL]), and local oral risk factors (e.g. tooth extraction, periodontitis). Whereas optimal oral health prior to initiate pARs is recognized as critically important for minimizing ONJ risk, the efficacy of preventive/maintenance measures in patients who are taking pARs is understudied. Rice rats fed a standard diet (STD), rich in insoluble fiber, develop localized periodontitis. STD-rats with localized periodontitis treated with ZOL for 18-24 wk develop ONJ. Hence, we hypothesized that controlling/preventing localized periodontitis in the ZOL-treated rats, reduces ONJ occurrence.

METHODS

We used two approaches to attempt reducing periodontitis prevalence: 1) periodontal cleaning (PC); and 2) replacing the STD-diet with a nutritionally-equivalent diet high in soluble fiber (SF). 75 four-week-old male rats were weight-randomized into five groups (n = 15) in a 24-week experiment. Three groups ate the STD-diet and two the high SF-diet. STD-diet groups received intravenous (IV) vehicle (VEH) q4wks (STD + VEH), 80 μg/kg ZOL q4wks IV (STD + ZOL), or ZOL plus PC q2wks (STD + ZOL + PC). The SF-diet groups received VEH (SF + VEH) or ZOL (SF + ZOL). Jaws were processed for histopathology and evaluated for ONJ prevalence and tissue-level periodontitis.

RESULTS

1) 40% of STD + VEH rats developed maxillary localized periodontitis with no ONJ; 2) 50% of STD + ZOL rats developed ONJ; 3) 7% of STD + ZOL + PC rats developed ONJ (p < 0.01 vs. STD + ZOL); and 4) one SF + ZOL rat developed localized periodontitis, and no SF + VEH or SF + ZOL rats developed ONJ (p < 0.001 vs. STD + ZOL).

CONCLUSIONS

1) Periodontal cleaning in ZOL-treated rats decreases localized periodontitis severity and reduces ONJ prevalence; and 2) feeding a SF-diet to ZOL-treated rats reduces both incidence of localized periodontitis and ONJ. Our data indicates strong oral microbial community shifts according to oral health condition and trends in the shifts associated with diet.

The Role of the Immune Response in the Development of Medication-Related Osteonecrosis of the Jaw

Medication-related osteonecrosis of the jaw (MRONJ) is a rare but serious adverse drug effect. There are multiple hypotheses to explain the development of MRONJ. Reduced bone remodeling and infection or inflammation are considered central to the pathogenesis of MRONJ. In recent years, increasing evidence has shown that bisphosphonates (BPs)-mediated immunity dysfunction is associated with the pathophysiology of MRONJ. In a healthy state, mucosal immunity provides the first line of protection against pathogens and oral mucosal immune cells defense against potentially invading pathogens by mediating the generation of protective immunoinflammatory responses. In addition, the immune system takes part in the process of bone remodeling and tissue repair. However, the treatment of BPs disturbs the mucosal and osteo immune homeostasis and thus impairs the body's ability to resist infection and repair from injury, thereby adding to the development of MRONJ. Here, we present the current knowledge about immunity dysfunction to shed light on the role of local immune disorder in the development of MRONJ.

Effect of bisphosphonates on healing of tooth extraction wounds in infectious osteomyelitis of the jaw

OBJECTIVES

Antiresorptive agent-related osteonecrosis of the jaw (ARONJ) and infectious osteomyelitis of the jaw (OMJ) in antiresorptive-naïve patients are different disease entities. Although osteoclast inhibition is at the center of the pathogenesis of ARONJ, the role of osteoclast inhibition in infectious OMJ is unknown. The objective of this study was to determine the effect of bisphosphonate osteoclast inhibition in infectious OMJ.

METHODS

Osteomyelitis was induced in mice by S. aureus inoculation. The establishment of OMJ was verified by the culture of bone marrow samples obtained from the mandible. Infected animals received either zoledronic acid (ZA) or saline starting at week-2. Treated animals along with non-infected animals underwent tooth extractions at week-4 post-infection. Healing was assessed every week using in vivo micro-computed tomography and intraoral photos. Animals were euthanized at week-8 and cervical lymph nodes were assessed for lymphatic and blood vessels.

RESULTS

Tooth extraction wounds did not heal in animals with OMJ. These wounds were characterized by incomplete soft tissue coverage, sporadic bone fill in the sockets, and inflammatory cell accumulation in the connective tissue at 4 weeks after tooth extractions. Conversely, the majority of tooth extraction wounds in the infected animals treated with ZA had improved healing with better bone fill than even non-infected control animals. Consistently, atrophic lymphatic vessels were noted in the draining lymph nodes in animals with OMJ. However, infected animals treated with ZA had lymphatic vessels that were unaltered and showed a similar appearance to those in non-infected control animals.

CONCLUSION

ZA treatment promoted wound healing in the jaw with infectious osteomyelitis. Clearly, antiresorptive therapy is contraindicated in patients with ARONJ. However, our finding suggests that osteoclast inhibition is potentially an effectual remedy for infectious OMJ in antiresorptive-naïve patients.

Intramedullary injury combined with osteoporosis therapeutics regulates targeted local osteogenesis

Bone marrow ablation prompts transient bone formation in nearly the entire medullary cavity before marrow regeneration occurs. Here, we establish a procedure to direct bone formation in a desired particular site within the medullary cavity for support of biomedical devices. Local intramedullary injury was performed in the tibiae of rats and parathyroid hormone (PTH), alendronate, or saline was administered. Newly generated bone in the medulla was assessed by micro-CT and histology. To evaluate the function of newly generated bone, animals received intramedullary injury in tibiae followed by daily PTH. At day-14, implants were placed in the endocortical bone and the bone response to the implants was assessed. The fate of newly generated bone was compared with and without implants. We found that neither intramedullary injury nor medication alone resulted in bone formation. However, when combined, substantial bone was generated locally inside the diaphyseal medulla. Newly formed bone disappeared without implant placement but was retained with implants. Bone was especially retained around and between the implants. This study found that local bone marrow disruption followed by PTH or alendronate generated substantial cancellous bone locally in the diaphyseal medulla. This approach offers promise as a tissue engineering tool in medicine and dentistry.

The effects of zoledronic acid on the progression of experimental periodontitis in rats: histological and microtomographic analyses

Purpose

Periodontitis is considered a local risk factor for medication-related osteonecrosis of the jaws (MRONJ). However, little is known about the progression of periodontitis in the presence of zoledronic acid (ZOL). The aim of this study was to evaluate the effects of the systemic use of ZOL on the progression of experimental periodontitis (EP) in rats, as ZOL could modulate the progression of periodontitis and concomitantly cause MRONJ in individuals with periodontitis.

Methods

Forty-eight male Wistar rats were randomly distributed in 6 groups (n=8 each). To induce EP, ligatures were placed around the right first mandibular molars. Three groups were treated with ZOL (0.15 mg/kg/week, intraperitoneal), and 3 with 0.9% saline solution (controls). In the ZOL/Lig30 and ZOL/Lig 15 groups, after 4 weeks of treatment with ZOL, EP was induced and euthanasia was performed after 30 and 15 days of EP induction, respectively. In both groups, the animals continued to receive ZOL after EP until the end of the experiment. In the Lig/ZOL group, EP was induced first, and 15 days later, ZOL was administered for 8 weeks, with euthanasia 1 week after the last dose. After euthanasia, the mandibles were evaluated using micro-computed microtomography (micro-CT) and histomorphometry. Bone loss was measured, and the presence of osteonecrosis was evaluated histologically. The data were evaluated using the Student t-test and the Mann-Whitney test, with a significance level of 5%.

Results

In the Lig/ZOL group, micro-CT revealed less alveolar bone resorption in the distal root (P<0.01) than in the control group (Lig/Con). Histomorphometric analysis confirmed less alveolar bone resorption in the Lig/ZOL group (P=0.001). Histologically, osteonecrosis was more common in the ZOL groups.

Conclusion

ZOL decreased alveolar bone resorption in rats with EP. However, it presented a higher risk for MRONJ.

Distinct immunopathology in the early stages between different antiresorptives-related osteonecrosis of the jaw-like lesions in mice

There is limited information about denosumab-related osteonecrosis of the jaw (DRONJ), unlike bisphosphonate-related ONJ (BRONJ). The mode of action is clearly different between denosumab and bisphosphonates. DRONJ occurs mainly following tooth extraction in cancer patients treated with the combination of denosumab and other drugs including chemotherapy. However, DRONJ animal models similar to these clinical situations have not been developed. The aims of this study were to 1) create a new model of high-prevalence chemotherapy/anti-RANKL antibody-related ONJ-like lesions to mimic patients receiving a denosumab/chemotherapy combination; and 2) compare the histopathological and immunopathological findings in the early stages of BRONJ-like and anti-RANKL antibody-related ONJ-like lesions. Cyclophosphamide (CY) and anti-mouse RANKL monoclonal antibody (mAb) or zoledronate combination therapy (CY/mAb and CY/ZA, respectively) was performed to create ONJ-like lesions in female C57BL/6J mice. Both maxillary first molars were extracted at 3 weeks after drug administration. The animals were euthanized at either 2 or 4 weeks after tooth extraction. Increased necrotic bone and empty lacunae with decreased living bone and osteocyte numbers were common histopathological findings in CY/mAb- and CY/ZA-induced impaired wound healing at 4 weeks after tooth extraction, and they were diagnosed as ONJ-like lesions based on validation of BRONJ and DRONJ in humans. In areas of impaired healing at 2 weeks post-extraction, decreases in angiogenesis and F4/80⁺LYVE-1^- macrophages were noted as common immunopathological findings, although anti-angiogenesis was worse with CY/mAb than with CY/ZA. Interestingly, CY/mAb did not reduce F4/80⁺LYVE-1⁺ cells and normal lymphangiogenesis remained, whereas CY/ZA profoundly suppressed the larger size of F4/80⁺LYVE-1⁺ cells, similar to vessels with a concomitant decrease in lymphangiogenesis. Therefore, the distribution of the larger size of F4/80⁺LYVE-1⁺ cells differed in the early stages between different antiresorptive-induced ONJ-like lesions in conjunction with lymphangiogenesis, although the histopathological findings were similar. These findings suggest that the pathogenesis of BRONJ and DRONJ may differ due to the distributions of F4/80⁺LYVE-1⁺ tube-like-structured cells.

Allogeneic Bone Marrow Mesenchymal Stem Cell Transplantation in Tooth Extractions Sites Ameliorates the Incidence of Osteonecrotic Jaw-Like Lesions in Zoledronic Acid-Treated Rats

Medication-related osteonecrosis of the jaw (MRONJ) is defined as the exposed necrotic bone involving the maxillofacial structures in bisphosphonate treated patients, and the pathophysiology of this disease remains unclear. The aim of this study was to assess the effects of the allogeneic transplantation of bone marrow-derived mesenchymal stem cells (BM-MSCs) in a model of Wistar mice with induced MRONJ disease. BM-MSCs from five male Wistar rats were characterized and cultured on β-tricalcium phosphate (β-TCP) granules. Thirty female Wistar rats were injected intraperitoneally with zoledronic acid and afterwards upper jaw molars were extracted. The animals were randomized to receive: Group 1: 1 × 10⁶ BM-MSCs/β-TCP construct in the alveolar socket; and Group 2: Saline solution/β-TCP construct. A clinical and histological analysis was performed. Nested polymerase chain reaction (PCR) was assessed to verify the presence of transplanted male rat cells in the female recipient jaws. Clinical and histological findings evidenced that none of the animals in Group 1 exhibited uncovered sockets or bone exposure associated to MRONJ, whereas we detected 33% of MRONJ cases in Group 2. In addition, male rat cells were detected in the maxillae site four weeks after transplantation in the BM-MSCs-group. Allogeneic BM-MSCs in extractions sites ameliorates MRONJ incidence in zoledronic acid-treated rats compared to non-MSC treatments.

An evaluation of the effects of caffeic acid phenethyl ester and Ankaferd blood stopper on secondary wound healing of oral mucosal tissue

Background/aim

Caffeic acid phenethyl ester (CAPE) and Ankaferd Blood Stopper (ABS) are considered to contribute to wound healing. The purpose of this study was to investigate the effect of ABS and CAPE on secondary wound healing of oral mucosal tissue.

Materials and methods

In total, 63 male Sprague-Dawley rats were used in this study. The animals were randomly divided into three groups and anaesthetized with ketamine (8 mg/100 g, intraperitoneally): a control group, CAPE group, and ABS group. A full-thickness excisional wound was created using a 4 mm punch biopsy tool. Topical ABS and CAPE were then applied in each group for 7, 14, and 21 days (n = 7 in each group). The animals in each group were sacrificed after 7, 14, and 21 days. Palatal specimens were stained with haematoxylin-eosin. Vascular endothelial growth factor (VEGF) and tumour necrosis factor-inducible gene 6 (TSG-6) protein expressions were determined using the Western blot method.

Results

Inflammation, vessel dilatation, and haemorrhages were significantly lower in the CAPE group as compared with these parameters in the other groups (P < 0.05). Fibrosis was significantly higher in the ABS group as compared with that in the other groups (P < 0.05). VEGF protein levels were elevated in the 21-day CAPE group and 7-day ABS group. The expression of TSG-6 increased in the 7-day CAPE group and 21-day ABS group.

Conclusion

Based on our findings, ABS and CAPE had positive effects on the oral wound healing process.

Anti-vascular endothelial growth factor antibody monotherapy causes destructive advanced periodontitis in rice rats (Oryzomys palustris)

OBJECTIVE

Angiogenesis inhibitors (AgI) are commonly used in combination chemotherapy protocols to treat cancer, and have been linked to osteonecrosis of the jaw (ONJ). However, it is unknown if AgI therapy alone is sufficient to induce ONJ. We have previously established an ONJ model in rice rats with localized periodontitis that receive zoledronic acid (ZOL). The purpose of this study was to use this model to determine the role of anti-vascular endothelial growth factor A (anti-VEGF) antibody treatment of rice rats with localized maxillary periodontitis. We hypothesized that rice rats with localized maxillary periodontitis given anti-VEGF monotherapy will develop oral lesions that resemble ONJ, defined by exposed, necrotic alveolar bone.

METHODS

At age 4 weeks, 45 male rice rats were randomized into three groups (n = 15): 1) VEH (saline), 2) ZOL (80 μg/kg body weight, intravenously once monthly), and 3) anti-VEGF (5 mg B20-4.1.1/kg body weight, subcutaneously twice weekly). After 24 weeks, rats were euthanized, jaws were excised and a high-resolution photograph of each quadrant was taken to assign a severity grade based on gross appearance. Jaws were then fixed, scanned by MicroCT, decalcified and sectioned for histopathologic and immunohistochemical analyses.

RESULTS

40-80% of the rats in the three groups developed gross oral lesions. 50% of ZOL rats developed ONJ. In contrast, 80% of the anti-VEGF rats developed destructive advanced periodontitis that was characterized by extreme alveolar bone loss and fibrosis. Anti-VEGF rats never developed exposed, necrotic bone. Furthermore, only anti-VEGF rats developed mild to severe mandibular periodontitis. Compared to VEH rats, more T-cells were found in periodontal lesions of anti-VEGF rats and more cells of the monocyte lineage were found in ONJ lesions of ZOL rats.

CONCLUSIONS

Anti-VEGF monotherapy administered to a validated rodent model of ONJ caused a destructive advanced form of periodontitis that differed significantly from ONJ.

Dental care for patients taking antiresorptive drugs: a literature review

Antiresorptive drugs (ARDs), such as bisphosphonates or denosumab, that prevent bone resorption are widely used in patients with osteoporosis or with cancer that has metastasized to the bones. Although osteonecrosis of the jaw (ONJ) is a well-documented complication of ARD use, the benefits ARDs outweigh the complication. Thus, research has focused on finding ways to prevent or reduce the risk of developing ONJ. Dentists, as part of a multi-professional team, have a critical role in preventing ONJ. However, many dentists tend to hesitate to provide dental care to patients with ONJ, or tend to think that it is a problem to be dealt with by oral surgeons. This review gives an overview of ARD-related ONJ and provides the guidelines for dental care in patients taking ARDs to lower the risk of developing ONJ.

Effects of local application of alendronate on early healing of extraction socket in dogs

OBJECTIVE

The aim of the present study was to assess the effects of alendronate (ALN) on bone remodeling following tooth extraction in a dog model.

MATERIAL AND METHODS

For the study, fifteen male Beagles dogs of approximately 12 months of age were used. Mesial roots of four mandibular premolars were endodontically treated, and the distal roots were removed. ALN concentrations of 0.5, 1, and 2 mg/mL were topically applied for 15 min, while a sterile saline was used as a negative control. After the healing period of 1, 2, and 8 weeks, the samples were analyzed by micro-CT and histology.

RESULTS

Treatment with ALN increased vertical distance between the lingual and the buccal crestal bones. While the ALN-treated sockets had preserved more lingual bone areas, control sockets showed better preservation of the buccal bone areas. ALN treatment resulted in more osteoid formation within the extraction sockets compared with the control. Higher bone volume was found in ALN groups than in the control at 2-week and 8-week healing periods, reaching the significant difference only for the extraction sockets pooled for the ALN treatment.

CONCLUSIONS

Although ALN treatment could not prevent buccal bone resorption following tooth extraction in dogs, it proved beneficial for the preservation of the lingual bone and formation of new bone within the socket. There was no clear relation between the ALN dosages and the alterations within the extraction sockets.

CLINICAL RELEVANCE

ALN affects bone remodeling of the extraction socket. The optimal concentration remains to be determined in future studies.

Systemic administration of quality- and quantity-controlled PBMNCs reduces bisphosphonate-related osteonecrosis of jaw-like lesions in mice

BACKGROUND

Definitive treatment strategies for bisphosphonate-related osteonecrosis of the jaw (BRONJ) have not been developed. Cell-based therapy is an attractive treatment method for intractable diseases in the medical and dental fields; however, approval has been challenging in dentistry. Recently, we developed quality- and quantity (QQ)-controlled peripheral blood mononuclear cells (PBMNCs) that have anti-inflammatory and pro-angiogenesis effects. The aim of this study was to investigate the effects of QQ-controlled PBMNC transplantation on BRONJ-like lesions in mice.

METHODS

To create high-prevalence BRONJ-like lesions, cyclophosphamide (CY) and zoledronate (ZA) were used with tooth extraction. Drug treatment was performed for 5 weeks. QQ-controlled PBMNC transplantation was performed immediately following tooth extraction of both maxillary first molars at 3 weeks after drug administration. Mice were euthanized at 2 weeks post-extraction. Histomorphometric and immunohistochemical analyses, microcomputed tomography assessment, and quantitative polymerase chain reaction evaluation were conducted using maxillae and long bones.

RESULTS

ZA effects on long bones were noted, regardless of CY. Severely inhibited osseous and soft tissue wound healing of tooth extraction sockets was induced by CY/ZA combination therapy, which was diagnosed as BRONJ-like lesions. QQ-controlled PBMNC transplantation reduced BRONJ-like lesions by improving soft tissue healing with increased M1 and M2 macrophages and enhanced neovascularization in the connective tissue of tooth extraction sockets. QQ-controlled PBMNC transplantation also reduced inflammation by decreasing polymorphonuclear cells and TNF-α expression in the tooth extraction sockets. Additionally, QQ-controlled PBMNC transplantation partially improved osseous healing of tooth extraction sockets. Interestingly, only 20,000 QQ-controlled PBMNCs per mouse induced these transplantation effects. QQ-controlled PBMNC transplantation did not affect the systemic microenvironment.

CONCLUSIONS

Our findings suggest that transplantation of a small amount of QQ-controlled PBMNCs may become novel therapeutic or prevention strategies for BRONJ without any adverse side effects.

Low-Intensity Pulsed Ultrasound Prevents Development of Bisphosphonate-Related Osteonecrosis of the Jaw-Like Pathophysiology in a Rat Model

We developed a rat model of bisphosphonate-related osteonecrosis of the jaw (BRONJ) by removing a maxillary molar tooth (M1) from ovariectomized rats after treatment with alendronate. To mimic periodontitis, some of the rats were administered Porphyromonas gingivalis (p. gingivalis) at the M1 site every 2 to 3 d for 2 wk. Rats pretreated with alendronate plus p. gingivalis showed delayed healing of socket epithelia, periosteal reaction of alveolar bone formation and lower bone mineral density in the alveolus above adjacent M2 teeth. These abnormalities were prevented by tooth socket exposure to 20 min/d low-intensity pulsed ultrasound (LIPUS), which restored diminished expression of RANKL, Bcl-2, IL-6, Hsp70, NF-κB and TNF-α messenger ribonucleic acids in remote bone marrow, suggesting LIPUS prevented development of BRONJ-like pathophysiology in rat by inducing systemic responses for regeneration, in addition to accelerating local healing. Non-invasive treatment by LIPUS, as well as low-level laser therapy, may be useful for medication-related osteonecrosis of the jaw patients.

Bisphosphonate-related osteonecrosis. Application of adipose-derived stem cells in an experimental murine model

Background

Bisphosphonate-related osteonecrosis of the jaw is a pathological condition without effective established treatment and preventive strategies. The aim of this study was to analyse the effect of adipose-derived stem cells (ASC) in an experimental murine model of osteonecrosis.

Material and Methods

38 Wistar rats were injected intraperitoneally with zoledronic acid. After treatment, upper jaw molars were extracted. The animals were randomly assigned to one of two groups. In the control group, saline solution was applied over the alveolar sockets after the tooth extractions. In the treatment group, ASCs were applied instead of saline solution. The control and treatment groups were subdivided based on the time of euthanasia. A clinical and histological analysis was performed.

Results

The presence of osteonecrosis in alveolar bone was observed in a similar distribution in both groups. In the ASC-treated group, new bone formation was greater than in controls.

Conclusions

In this study, application of ASCs showed greater new bone formation in an osteonecrosis-like murine model. Previous inhibited post-extraction bone remodelling could be reactivated, and these findings appeared to be secondary to implantation of ASCs.

Key words:Osteonecrosis; bisphosphonates, Mesenchymal stem cells (MSC), adipose-derived stem cells (ASCs), zoledronic acid.

Effect of low-level laser therapy and zoledronic acid on bone repair process

This study aimed to evaluate, through histomorphometric analysis, the bone repair process in the tibia of rats treated with zoledronic acid and submitted to 808-nm low-level laser therapy (LLLT) by using arsenide aluminum gallium laser. For this purpose, 20 rats were used and distributed according to treatment: group 1-saline administration; group 2-treated with LLLT; group 3-treated with zoledronic acid; and group 4-treated with zoledronic acid and LLLT. The zoledronic acid was administered at a dose of 0.035 mg/kg every 2 weeks for 8 weeks. Subsequently, bone defects of 2 mm were prepared in the tibias of all groups. The bone defects in groups 2 and 4 were irradiated with LLLT in the immediate post-operative period. After 14 and 28 days of application, the animals were submitted and euthanized for histomorphometric analysis. The results were submitted to statistical analysis (α = 5%), and the intragroup comparison was performed using the t test. On the other hand, for intergroup comparison, the ANOVA test was performed, and to the groups presenting statistically significant difference, the Student-Newman-Keuls test was used. In intergroup comparison, group 1 (mean ± SD= 45.2 ± 18.56%) showed a lower bone formation compared with groups 2 (64.13 ± 3.51%) (p = 0.358) and 4 (15.2 ± 78.22%) (p = 0.049), at the 14-day period. Group 3 (20.99 ± 7.42%) also presented a lower amount of neoformed bone tissue, with statistically significant difference when compared with groups 1 (p = 0.002), 2, and 4 (p ≤ 0,001). After 28 days, group 1 presented a lower amount of neoformed bone tissue compared with the other groups, with p = 0.020. Thus, it was concluded that LLLT associated with zoledronic acid is effective for stimulating bone formation in surgically created defects in rats, at the periods studied.

Zoledronate treatment duration is linked to bisphosphonate-related osteonecrosis of the jaw prevalence in rice rats with generalized periodontitis

OBJECTIVES

To determine the extent that zoledronate (ZOL) dose and duration is associated with bisphosphonate-related osteonecrosis of the jaw (BRONJ) prevalence in rice rats with generalized periodontitis (PD), characterize structural and tissue-level features of BRONJ-like lesions in this model, and examine the specific anti-resorptive role of ZOL in BRONJ.

MATERIALS AND METHODS

Rice rats (n = 228) consumed high sucrose-casein diet to enhance generalized PD. Groups of rats received 0, 8, 20, 50 or 125 µg/kg IV ZOL/4 weeks encompassing osteoporosis and oncology ZOL doses. Rats from each dose group (n = 9-16) were necropsied after 12, 18, 24 and 30 weeks of treatment. BRONJ-like lesion prevalence and tissue-level features were assessed grossly, histopathologically and by MicroCT. ZOL bone turnover effects were assessed by femoral peripheral quantitative computed tomography, serum bone turnover marker ELISAs and osteoclast immunolabelling.

RESULTS

Prevalence of BRONJ-like lesions was significantly associated with (a) ZOL treatment duration, but plateaued at the lowest oncologic dose, and (b) there was a similar dose-related plateau in the systemic anti-resorptive effect of ZOL. ZOL and BRONJ-like lesions also altered the structural and tissue-level features of the jaw.

CONCLUSION

The relationship between BRONJ-like lesion prevalence and ZOL dose and duration varies depending on the co- or pre-existing oral risk factor. At clinically relevant doses of ZOL, BRONJ-like lesions are associated with anti-resorptive activity.

Effect of anti-angiogenesis induced by chemotherapeutic monotherapy, chemotherapeutic/bisphosphonate combination therapy and anti-VEGFA mAb therapy on tooth extraction socket healing in mice

Osteonecrosis of the jaw (ONJ), which is a rare but severe adverse effect, mainly occurs in oncology patients receiving chemotherapeutic agents and bisphosphonates. However, the combined impact of chemotherapy and bisphosphonates on wound healing after tooth extraction remains unknown. The aim of this study was to determine the precise etiology of ONJ induced by chemotherapy and bisphosphonate combination therapy. Mice received zoledronate (ZA) monotherapy, cyclophosphamide (CY) monotherapy or CY/ZA combination therapy. The maxillary first molars were extracted 3 weeks after the initiation of drug treatment. Moreover, antivascular endothelial growth factor A (VEGFA) monoclonal antibody (mAb) was administered once every 2 days just after tooth extraction for 2 weeks. Soft and hard tissue wound healing was evaluated 2 and 4 weeks post-extraction using histomorphometry, microcomputed tomography and immunohistochemistry. ZA monotherapy did not induce impaired oral wound healing and ONJ-like lesions 2 and 4 weeks post-extraction, respectively. Tooth extraction socket healing worsened with severe anti-angiogenesis by CY monotherapy and CY/ZA combination therapy 2 weeks post-extraction. However, CY monotherapy rarely induced ONJ-like lesions with severe angiogenesis suppression, whereas CY/ZA combination therapy frequently induced ONJ-like lesions with severe angiogenesis inhibition 4 weeks post-extraction. Interestingly, anti-VEGFA mAb therapy delayed osseous wound healing with normal soft tissue wound healing of tooth extraction sockets, although this therapy significantly suppressed blood vessel formation. Our findings suggest that anti-angiogenesis alone is not the main cause of ONJ-like lesions induced by CY/ZA combination therapy. The combination of suppressed osteoclasts and anti-angiogenesis, in addition to other risk factors such as chemotherapy, may contribute to the development of ONJ.

Third-party regulatory T cells prevent murine acute graft-versus-host disease

BACKGROUND/AIMS

Adoptive therapy with regulatory T (Treg) cells to prevent graft-versus-host disease (GVHD) would benefit from a strategy to improve homing to the sites of inflammation following hematopoietic stem cell transplantation (HSCT). Although donor-derived Treg cells have mainly been used in these models, third-party-derived Treg cells are a promising alternative for cell-based immunotherapy, as they can be screened for pathogens and cell activity, and banked for GVHD prevention. In this study, we explored major histocompatibility complex (MHC) disparities between Treg cells and conventional T cells in HSCT to evaluate the impact of these different cell populations on the prevention of acute GVHD, as well as survival after allogeneic transplantation.

METHODS

To induce acute GVHD, lethally irradiated BALB/c (H-2d) mice were transplanted with 5 × 105 T cell-depleted bone marrow cells and 5 × 105 CD4+CD25- splenic T cells from C57BL/6 (H-2b) mice. Recipients were injected with 5 × 105 cultured donor-, host-, or third-party-derived CD4+CD25+CD62L+ Treg cells (bone marrow transplantation + day 1).

RESULTS

Systemic infusion of three groups of Treg cell improved clinicopathological manifestations and survival in an acute GVHD model. Although donor-derived Treg cells were immunologically the most effective, the third-party-derived Treg cell therapy group displayed equal regulation of expansion of CD4+CD25+- Foxp3+ Treg cells and suppressive CD4+IL-17+ T-helper (Th17) cells in ex vivo assays compared with the donor- and host-derived groups.

CONCLUSION

Our findings demonstrate that the use of third-party Treg cells is a viable alternative to donor-derived Treg cellular therapy in clinical settings, in which human leukocyte antigen-matched donors are not always readily available.

Prevalence of bisphosphonate-related osteonecrosis of the jaw-like lesions is increased in a chemotherapeutic dose-dependent manner in mice

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) worsens oral health-related quality of life. Most BRONJ occurs in multiple myeloma or metastatic breast cancer patients treated with bisphosphonate/chemotherapeutic combination therapies. Cyclophosphamide (CY), an alkylating chemotherapeutic drug, is used to treat multiple myeloma, although its use has been recently reduced. The aim of this study was to clarify the effects of CY dose on tooth extraction socket healing when CY is used with or without bisphosphonate in mice. Low-dose CY (50 mg/kg; CY-L), moderate-dose CY (100 mg/kg; CY-M), high-dose CY (150 mg/kg; CY-H), and bisphosphonate [Zometa (ZA): 0.05 mg/kg] were administered for 7 weeks. Each dose of CY and ZA in combination was also administered for 7 weeks. Both maxillary first molars were extracted at 3 weeks after the initiation of drug administration. Euthanasia was performed at 4 weeks post-extraction. Gross wound healing, microcomputed tomography analysis, histomorphometry, and immunohistochemistry were used to quantitatively evaluate osseous and soft tissue wound healing of tooth extraction sockets. ZA monotherapy induced no BRONJ-like lesions in mice. CY monotherapy rarely induced open wounds, though delayed osseous wound healing occurred in a CY dose-dependent manner. In contrast, CY/ZA combination therapy prevalently induced BRONJ-like lesions with compromised osseous and soft tissue healing in a CY dose-dependent manner. Interestingly, anti-angiogenesis was noted regardless of CY dose and ZA administration, even though only CY-M/ZA and CY-H/ZA combination therapies induced BRONJ-like lesions. Our findings suggest that high-dose CY may be associated with the development of BRONJ following tooth extraction only when CY is used together with ZA. In addition to anti-angiogenesis, other factors may contribute to the pathoetiology of BRONJ.

Zoledronic acid increases the prevalence of medication-related osteonecrosis of the jaw in a dose dependent manner in rice rats (Oryzomys palustris) with localized periodontitis

OBJECTIVE

Investigate role of dose/duration of zoledronic acid (ZOL), a powerful anti-resorptive (pAR), on prevalence of medication-related osteonecrosis of the jaw (MRONJ) in rice rats (Oryzomys palustris), a species with natural susceptibility to food impaction-induced localized periodontitis (FILP). We hypothesize that ZOL induces MRONJ lesions in rice rats with FILP, and that the prevalence of MRONJ rises with increasing dose and duration of ZOL treatment.

METHODS

We performed a toxicology experiment with clinically-relevant doses of ZOL in female rats (N=230) fed standard (STD) rodent chow. At age 4weeks (baseline), 12 rats were necropsied. The rest were randomized into five groups that began to receive 0, 8, 20, 50 or 125μg/kg ZOL IV/q 4weeks. After 12, 18, 24 and 30weeks, subgroups (N=9-16) from each of the dose groups were necropsied. High-resolution macroscopic photos of all jaw quadrants were given a gross quadrant grade (GQG) (0-4 or MRONJ) that classified FILP lesion severity and determined presence of gross MRONJ. Quadrants with GQG≥1 were examined histopathologically. Logistic regression analysis (ZOL dose/duration) of MRONJ prevalence was completed.

RESULTS

We found: 1) 75% of 0μg/kg ZOL rats developed FILP lesions; 2) baseline rats and rats treated with 0μg/kg ZOL had no MRONJ; 3) 29 gross MRONJ cases were identified; 4) all gross MRONJ cases were confirmed histopathologically by the observation of exposed necrotic bone, and 53 new cases were discovered (total=82); 5) ZOL dose (P<0.001), but not duration (P=0.326), was a significant predictor of MRONJ prevalence; 6) 13% prevalence of gross MRONJ among all rats, with 22% prevalence among rats exposed to ZOL oncologic doses (20-125μg/kg); 7) 38% prevalence of histopathologic MRONJ among all rats, with 73% prevalence among rats exposed to ZOL oncologic doses.

CONCLUSIONS

This is the first experiment to show a dose response relationship between clinically relevant doses of ZOL and MRONJ prevalence.

Effect of zoledronate, a third-generation bisphosphonate, on proliferation and apoptosis of human dental pulp stem cells

Clinical use of zoledronate is accompanied by osteonecrosis of the jaw but the pathogenesis is not well understood. We assumed that zoledronate may have cytotoxicity against stem cells of the oral cavity and in this way helps to initiate or promote osteonecrosis. Dental pulp stem cells (DPSCs) and gingival fibroblasts (GFs) were isolated from volunteers who were undergoing a third molar extraction. The proliferation of DPSCs and GFs was evaluated using the thiazolyl blue tetrazolium bromide assay. The effect of zoledronate on apoptosis was determined by propidium iodide staining and Western blotting analysis. Incubation with zoledronate for 72 h and 7 days significantly decreased proliferation of DPSCs and GFs at concentrations of more than 0.4 μmol/L (p < 0.001). The IC50 of zoledronate was lower for DPSCs than for GFs (0.92 versus 3.5 μmol/L for 7 days of treatment). After 72 h of treatment with zoledronate, the percentage of apoptotic DPSCs significantly increased, which was accompanied by an increased level of pro-apoptotic proteins caspase-3 and Bax and decreased the level of the anti-apoptotic protein Bcl-2. In conclusion, zoledronate has anti-proliferative and pro-apoptotic effects in DPSCs. These effects may be involved in promoting zoledronate-induced osteonecrosis and suggest an unfavorable impact of this drug on regenerative potentials of the body stem cells.

Transplantation of Noncultured Stromal Vascular Fraction Cells of Adipose Tissue Ameliorates Osteonecrosis of the Jaw-Like Lesions in Mice

The precise pathoetiology and effective treatment strategies for bisphosphonate-related osteonecrosis of the jaw (BRONJ) remain unknown. Transplantation of noncultured stromal vascular fraction (SVF) cells has been shown to be a useful method for regenerative medicine in place of stem cell therapy. This study investigated the effects of noncultured SVF transplantation on tooth extraction socket healing in mice. Both chemotherapeutic/bisphosphonate combination therapy for 7 weeks and tooth extraction of maxillary first molars at 3 weeks after drug administration were performed using female C57BL/6J mice. Osseous and soft tissue wound healing were validated at 4 weeks postextraction using gross wound healing and histomorphometry. Here, we created a new animal model of high-prevalence ONJ-like lesions that mimic human progression, because human ONJ mainly occurs in female patients taking both chemotherapeutic and bisphosphonate following tooth extraction. Moreover, mice with chemotherapeutic and bisphosphonate combination therapy for 5 weeks received SVF transplantation just after tooth extraction at 3 weeks post-drug administration. Euthanasia was performed at 2 weeks postextraction to assess the transplantation effects on wound healing using gross wound healing, histomorphometry, immunohistomorphometry, quantitative real-time polymerase chain reaction, and microcomputed tomography. We showed that systemic transplantation of noncultured SVF cells ameliorates ONJ-like lesions by improving both osseous and soft tissue healing of tooth extraction sockets. SVF therapy significantly increased blood vessels and the ratio of M2/M1 macrophages. In addition, SVF transplantation reduced the increases in tartrate-resistant acid phosphatase-positive (TRAP⁺ ) mononuclear cells (MNCs) and nonattached osteoclasts from the bone surface, which were significantly detected in the connective tissue of tooth extraction sockets and bone marrow by chemotherapeutic/bisphosphonate combination therapy. Our findings suggest that transplantation of noncultured SVF cells is a suitable treatment for BRONJ. Abnormal TRAP⁺ MNCs and nonattached osteoclasts in systemic and local environments may contribute to the development of BRONJ. © 2017 American Society for Bone and Mineral Research.

Case-Based Review of Osteonecrosis of the Jaw (ONJ) and Application of the International Recommendations for Management From the International Task Force on ONJ

Osteonecrosis of the jaw (ONJ) has been associated with antiresorptive therapy in both oncology and osteoporosis patients. This debilitating condition is very rare and advances in diagnosis and management may now effectively reduce the risk of its development and offer valuable treatment options for affected patients. This paper provides a case-based review of ONJ and application of the International Task Force on ONJ (referred to as the "Task Force") recommendations for the diagnosis and management of ONJ. The Task Force was supported by 14 international societies and achieved consensus from representatives of these multidisciplinary societies on key issues pertaining to the diagnosis and management of ONJ. The frequency of ONJ in oncology patients receiving oncology doses of bisphosphonate (BP) or denosumab is estimated at 1%-15%, and the frequency in the osteoporosis patient population receiving much lower doses of BP or denosumab is estimated at 0.001%-0.01%. Although the diagnosis of ONJ is primarily clinical, imaging may be helpful in confirming the diagnosis and staging. In those with multiple risk factors for ONJ for whom major invasive oral surgery is being planned, interruption of BP or denosumab therapy (in cancer patients) is advised, if possible, before surgery, until the surgical site heals. Major oral surgery in this context could include multiple extractions if surgical extractions are required, not simple forceps extractions. ONJ development may be reduced by optimizing oral hygiene and postoperatively using topical and systemic antibiotics as appropriate. Periodontal disease should be managed before starting oncology doses of BP or denosumab. Local debridement may be successful in disease unresponsive to conservative therapy. Successful surgical intervention has been reported in those with stage 3 disease; less severe disease is best managed conservatively. Teriparatide may be helpful in healing ONJ lesions and may be considered in osteoporosis patients at a high fracture risk in the absence of contraindications. Resumption of BP or denosumab therapy following healing of ONJ lesions is recommended, and there have not been reports of subsequent local recurrence.

Short-term perioperative teriparatide therapy for the prevention of medication-related osteonecrosis of the jaw: A randomized, controlled preclinical study in rats

OBJECTIVE

Dentoalveolar procedures in patients receiving bisphosphonates and other antiresorptive agents are associated with an increased risk of medication-related osteonecrosis of the jaw (MRONJ). The aim of present study was to evaluate the effects of perioperative teriparatide (TPD) therapy in prevention of MRONJ.

SUBJECTS AND METHODS

Two protocols of TPD therapy were studied. For protocol A, 25 TPD-treated (AT) and 25 control (AC) rats received 5 weekly injection of 0.06 mg/kg zoledronate. At the end of week 5, extraction of bilateral mandibular first molars was performed for all rats, and 4-week TPD (20 μg/kg/day) and saline therapy was started for AT and AC rats, respectively. For protocol B, 25 TPD-treated (BT) and 25 control (BC) rats received 5 weekly injection of 0.06 mg/kg zoledronate. One week later, 4-week TPD and saline therapy was started for BT and BC rats, respectively. Both groups underwent tooth extraction at the end of week 7 of the experiment. All rats were sacrificed 8 weeks after tooth extraction and assessed clinically for bone exposure/fistula, and histologically for density of osteocytes in newly formed bone and empty osteocyte lacunae in alveolar bone.

RESULTS

Incidence of bone exposure/fistula and mean numbers of osteocytes and empty lacunae per 25 mm² (at 400× magnification) were 20%, 15.36, and 2.63 in AT group; 78%, 5.78, and 6.81 in AC group; 14%, 16.94, and 2.08 in BT group; and 78%, 7.54, and 5.95 in BC group; respectively. The differences between AT and AC and between BT and BC were statistically significant (P < 0.001). However, no statistically significant difference between AT and BT and between AC and BC was found.

CONCLUSION

Four weeks of TPD therapy, beginning at the same day or 2 weeks before tooth extraction, had a potential role in prevention of ONJ.

Role of Teriparatide in Medication-Related Osteonecrosis of the Jaws (MRONJ)

While the optimal treatment concept of medication-related osteonecrosis of the jaws (MRONJ) is still in debate, several adjunct therapies have been introduced. Among these adjunctive measures, recombinant human parathyroid hormone (rhPTH, teriparatide) seems to be the most promising treatment modality. Several studies have presented the beneficial effect of short-term teriparatide; they have shown an improved level of bone markers and radiographic evidence of bone healing. Although clinical validation by a controlled trial with prospective design would be essential, short-term teripratide therapy would be a good treatment option for MRONJ patients with impaired bone remodeling.

The starting point for bisphosphonate-related osteonecrosis of the jaw: Alveolar bone or oral mucosa? A randomized, controlled experimental study

OBJECTIVE

Although over a decade has passed since first introduction of BRONJ, the exact pathophysiology of this disease is still unclear. The present experimental study aimed to determine whether the oral mucosa or alveolar bone serves as the starting point for BRONJ development.

SUBJECTS AND METHODS

Sixty male Wistar rats were randomly assigned into study and control groups (each, n = 30), and received intraperitoneal injection of 0.06 mg/kg zoledronate and saline, respectively, once a week for 12 weeks. At the end of the week 4 of the experiment, all 60 rats underwent unilateral mandibular first molar extraction. A 4 mm defect was made in the contralateral canine alveolar mucosa. At the end of the experiment, rats were sacrificed, and the three areas of interest including extraction, soft tissue defect, and the non-intervention (canine area on the same side of extraction) sites were assessed clinically for presence of bone exposure/fistula, and histologically for status of bone remodeling (only at extraction site) and osteonecrosis.

RESULTS

In the study group, the frequency of bone exposure/fistula was 80%, 0%, and 0%; and the rate of histological bone necrosis was 83.3%, 20%, and 0%; at the extraction, soft tissue defect, and non-intervention sites, respectively. No clinical and histological sign of bone necrosis was found in the control group. Normal bone remodeling was observed in 0% and 100% of the extraction sockets in the study and control groups, respectively.

CONCLUSION

Injury to alveolar bone was a stronger trigger for BRONJ development compared to oral mucosal damages.

Zoledronate induces autophagic cell death in human umbilical vein endothelial cells via Beclin-1 dependent pathway activation

Zoledronate has been reported to exhibit pro-apoptotic and anti-angiogenic effects in endothelial cells, which partially contributes to bisphosphonate-associated osteonecrosis of the jaw (BP-ONJ). Zoledronate can also induce autophagic cell death. The present study hypothesized that Zoledronate may activate autophagy to exert pro-apoptotic effects in endothelial cells and aimed to investigate the effect of Zoledronate on human umbilical vein endothelial cells (HUVECs) and explore the underlying mechanisms. The current study demonstrated that Zoledronate induced autophagy in HUVECs in a dose-dependent manner, as demonstrated by increased levels of microtubule-associated proteins 1A/1B light chain 3B-II (LC3B-II) and Beclin-1, and decreased levels of sequestome 1 (SQSTM1). In addition, treatment with chloroquine further increased LC3B-II and increased SQSTM1 levels, indicating that Zoledronate induces autophagy by increasing autophagic activity. Flow cytometry and Hoechst 33258 staining revealed that inhibition of autophagy with 3-methyladenine markedly attenuated Zoledronate-induced apoptosis. Furthermore, genetic knockdown of Beclin-1 significantly inhibited autophagy and apoptosis induced by Zoledronate. The present study therefore demonstrated that Zoledronate may promote Beclin-1-mediated autophagy to induce endothelial cell apoptosis, and suggests that blocking autophagy may represent a novel approach for the prevention of BP-ONJ in patients receiving Zoledronate.

Osteonecrosis of the Jaw-a Bone Site-Specific Effect of Bisphosphonates

A known complication that can occur in patients using bisphosphonates (BPs) is osteonecrosis of the jaw (ONJ). ONJ features bone exposure that may be associated with severe pain, swelling, local infection, and pathological fracture of the jaw. Current literature indicates that a complex combination of factors is necessary to induce ONJ. Several hypotheses about the pathophysiology of ONJ were previously reported. Here, we review these hypotheses and introduce new ideas and suggestions on this topic, focusing on bone site-specific cells, and the effect that BPs and other anti-resorptive drugs have on those cells. Gaining more insight into bone site-specific effects may help to better understand the pathogenesis ONJ, and contribute to the development of new bone site-specific anti-resorptive drugs.

Doses effects of zoledronic acid on mineral apatite and collagen quality of newly-formed bone in the rat's calvaria defect

Due to their inhibitory effects on resorption, bisphosphonates are widely used in the treatment of diseases associated to an extensive bone loss. Yet, little is known about bisphosphonates effects on newly-formed bone quality. In the present study, adult male Sprague-Dawley rats (n=80) with a bone defect calvaria area were used and short-term effects of zoledronic acid (ZA) were studied on the healing bone area. Three ZA treatments were tested by using either: 1°) a low single dose (120μgZA/kg, n=10; equivalent to human osteoporosis treatment), 2°) a low fractionated doses (20μgZA/kg daily for 6days either a total of 120μg/kg, n=15), and 3°) a high fractionated doses, (100μgZA/kg weekly for 6weeks, n=15; equivalent to 6months of human bone metastasis treatment). For each treatment, a control "vehicle" treatment was performed (with an identical number of rats). After ZA administration, the intrinsic bone material properties were evaluated by quantitative backscattered electron imaging (qBEI) and Raman microspectroscopy. Neither single nor fractionated low ZA doses modify the intrinsic bone material properties of the newly-formed bone compared to their respective control animals. On the opposite, the high ZA treatment resulted in a significant decrease of the crystallinity (-25%, P< 0.05) and of the hydroxyproline-to-proline ratio (-30%, P<0.05) in newly-formed bones. Moreover, with the high ZA treatment, the crystallinity was positively correlated with the hydroxyproline-to-proline ratio (ρ=0.78, P<0.0001). The present data highlight new properties for ZA on bone formation in a craniofacial defect model. As such, ZA at high doses disrupted the apatite crystal organization. In addition, we report here for the first time that high ZA doses decreased the hydroxyproline-to-proline ratio suggesting that ZA may affect the early collagen organization during the bone healing.

Immune cellular profile of bisphosphonate-related osteonecrosis of the jaw

OBJECTIVES

Characterize the cell profile and immunostaining of proinflammatory markers in an experimental model of bisphosphonate-related osteonecrosis of the jaw (BRONJ).

MATERIALS AND METHODS

Male Wistar rats (n = 6-7) were treated chronically with saline solution or zoledronic acid (ZA) at 0.04, 0.20, and 1.00 mg kg(-1) (1.4 × 10(-7) , 6.9 × 10(-6) , and 3.4 × 10(-5)  mol kg(-1) ), and subsequently, the first left inferior molar was extracted. Were performed counting of viable and empty osteocyte lacunae, viable and apoptotic osteoclasts, polymorphonuclear neutrophil, mast cells (toluidine blue), and the positive presence cells for CD68, tumor necrosis factor-alpha (TNF-α), IL (interleukin)-1β, inducible nitric oxide synthase (iNOS), nuclear factor-kappa B (NF-kB) and IL-18 binding protein (IL-18 bp).

RESULTS

BRONJ was showed in ZA treated with 0.20 and 1.00 mg kg(-1) . There is a dose dependent increase in percentage of empty osteocyte lacunae (P < 0.001) and apoptotic osteoclasts (P < 0.001), counting of total osteoclasts (P = 0.003), polymorphonuclear neutrophil cells (P = 0.009), cytoplasmic-positive cells of CD68 (P < 0.001), TNF-α (P = 0.001), IL-1β (P = 0.001), iNOS (P < 0.001), NF-kB (P = 0.006), and nuclear-positive cells of NF-kB (P = 0.011). Consequently, there is no difference in mast cells (P = 0.957), and IL-18 bp immunostaining decreases dose dependently (P = 0.005).

CONCLUSIONS

BRONJ is characterized by increases in immunostaining for proinflammatory markers and NF-kB and inversely associated with cells exhibiting IL-18 bp.