Zoledronate induces osteonecrosis of the jaw in sheep

Digoxin attenuates bisphosphonate related osteonecrosis of the jaws by RORγt-dependent Th17 response in male rats

OBJECTIVE

The study aimed to evaluate digoxin, an RORγt inhibitor, in Medication-Related Osteonecrosis of the Jaws (MRONJ) in male rats treated with zoledronic acid (ZA).

STUDY DESIGN

Forty male Wistar rats were divided into a negative control group (0.1 mL/kg saline), a positive control group (ZA, 0.20 mg/kg), and three test groups treated with ZA and digoxin at 1 (DG1), 2 (DG2), or 4 (DG4) mg/kg. These groups received treatment three times weekly. ZA was administered intravenously on days 0, 7, and 14, followed by extraction of the left lower first molar on day 42, a final ZA dose on day 49, and euthanasia on day 70. Analyses included radiographic, histomorphometric, and immunohistochemical evaluation of the mandibles, western blotting of gingiva, and mechanical tests on femurs. Statistical analysis was performed using ANOVA/Bonferroni tests (P < .05).

RESULTS

Digoxin reduced radiolucency of MRONJ (P < .001), inflammatory cells, empty osteocyte lacunae (P < .001), apoptotic osteoclasts (P < .001), and Caspase-3-positive osteocytes (P = .021). ZA increased immunoreactivity for most markers except c-Fos, while digoxin reduced interleukin 17, TNF-α, IL-6, IL-2, FOXP3, c-Jun, NFκB (P < .001), TGF-β (P = .009), RANKL (P = .035), and OPG (P = .034). Digoxin also reversed RORγt expression (P < .001), increased diarrhea scores (P = .028), renal and cardiac indexes (P < .001), and enhanced femur mechanical properties (P < .013).

CONCLUSIONS

Digoxin attenuated MRONJ by inhibiting RORγt and reducing the Th17 response.

Inflammation Can Be a High-Risk Factor for Mucosal Nonunion of MRONJ by Regulating SIRT1 Signaling When Treated with an Oncologic Dose of Zoledronate

Purpose

Zoledronate (ZA) stands as a highly effective antiresorptive agent known to trigger medication-related osteonecrosis of the jaw (MRONJ). Its clinical dosages primarily encompass those used for oncologic and osteoporosis treatments. While inflammation is recognized as a potential disruptor of mucosal healing processes associated with ZA, prior research has overlooked the influence of varying ZA dosages on tissue adaptability. Therefore, a deeper understanding of the specific mechanisms by which inflammation exacerbates ZA-induced MRONJ, particularly when inflammation acts as a risk factor, remains crucial.

Methods

Cell proliferation and migration of human oral keratinocytes (HOK) was analyzed after treatment with different doses of ZA and/or lipopolysaccharide (LPS) to assess their possible effect on mucosal healing of extraction wounds. Mouse periodontitis models were established using LPS, and histological changes in extraction wounds were observed after the administration of oncologic dose ZA. Hematoxylin and eosin (HE) staining and immunofluorescence were used to evaluate mucosal healing.

Results

In vitro, LPS did not exacerbate the effects of osteoporosis therapeutic dose of ZA on the proliferation and migration of HOK cells, while aggravated these with the oncologic dose of ZA treatment by inducing mitochondrial dysfunction and oxidative stress via regulating SIRT1 expression. Furthermore, SIRT1 overexpression can alleviate this process. In vivo, local injection of LPS increased the nonunion of mucous membranes in MRONJ and decreased the expression of SIRT1, PGC-1α, and MnSOD.

Conclusion

Inflammation aggravates oncologic dose of ZA-induced mitochondrial dysfunction and oxidative stress via a SIRT1-dependent pathway, enhancing the risk of impaired mucosal healing in MRONJ. Our study implies that inflammation becomes a critical risk factor for MRONJ development at higher ZA concentrations. Elucidating the mechanisms of inflammation as a risk factor for mucosal non-healing in MRONJ could inform the development of SIRT1-targeted therapies.

A large animal model of periodontal defects in bisphosphonate-related osteonecrosis of the jaw: a comparison of clinical and radiological findings

PURPOSE

The objective of this study was to demonstrate the suitability of cone-beam computed tomography (CBCT) for in vivo research in periodontology, with implications for oral implantology, facial traumatology, and all disciplines involved in treating patients with bisphosphonate-related osteonecrosis of the jaw (BRONJ).

METHODS

Halves of the jaws of 9 Swiss mountain sheep, assigned to a control group (n=3), an osteoporosis group (n=3) and a zoledronate-exposed group (n=3), were examined. Clinical and radiological evaluations were conducted using CBCT imaging to assess whether periodontitis and bone defects were observed to a significant extent after surgical tooth extraction.

RESULTS

In contrast to the control and osteoporosis groups, the zoledronate group exhibited significant residual bone defects following tooth extraction (P<0.05). CBCT more objectively revealed these effects and enabled a numerical evaluation (in mm3).

CONCLUSIONS

Evaluating residual defects in bone blocks from sheep using CBCT analysis was found to be as effective as a clinical examination conducted by specialists in oral and maxillofacial surgery. The strong correlation between radiological findings and clinical conditions suggests that CBCT may become increasingly important in the future, particularly in periodontological research related to BRONJ.

Clodronate disodium does not produce measurable effects on bone metabolism in an exercising, juvenile, large animal model

Bisphosphonates are commonly used to treat and prevent bone loss, but their effects in active, juvenile populations are unknown. This study examined the effects of intramuscular clodronate disodium (CLO) on bone turnover, serum bone biomarkers (SBB), bone mineral density (BMD), bone microstructure, biomechanical testing (BT), and cartilage glycosaminoglycan content (GAG) over 165 days. Forty juvenile sheep (253 ± 6 days of age) were divided into four groups: Control (saline), T0 (0.6 mg/kg CLO on day 0), T84 (0.6 mg/kg CLO on day 84), and T0+84 (0.6 mg/kg CLO on days 0 and 84). Sheep were exercised 4 days/week and underwent physical and lameness examinations every 14 days. Blood samples were collected for SBB every 28 days. Microstructure and BMD were calculated from tuber coxae (TC) biopsies (days 84 and 165) and bone healing was assessed by examining the prior biopsy site. BT and GAG were evaluated postmortem. Data, except lameness data, were analyzed using a mixed-effects model; lameness data were analyzed as ordinal data using a cumulative logistic model. CLO did not have any measurable effects on the skeleton of sheep. SBB showed changes over time (p ≤ 0.03), with increases in bone formation and decreases in some bone resorption markers. TC biopsies showed increasing bone volume fraction, trabecular spacing and thickness, and reduced trabecular number on day 165 versus day 84 (p ≤ 0.04). These changes may be attributed to exercise or growth. The absence of a treatment effect may be explained by the lower CLO dose used in large animals compared to humans. Further research is needed to examine whether low doses of bisphosphonates may be used in active juvenile populations for analgesia without evidence of bone changes.

Significance of bisphosphonates on angiogenesis in vivo and their effect under geranyl-geraniol addition - could it alter the treatment of bisphosphonate-associated necrosis of the jaw?

PURPOSE

The aim of this study was to contribute to the understanding of the inhibitory effects of bisphosphonates on tissues, with a special focus on angiogenesis. Referring to bisphosphonate-associated osteonecrosis of the jaw (BP-ONJ), it should be shown that the local addition of the isoprenoid geranyl-geraniol (GGOH) prevents vascularization processes.

METHODS

A mouse model with n = 24 animals which received an injection of a collagen matrix was used. In 4 subgroups (n = 6), we examined the effect of zoledronate on the sprouting of capillary-like structures into the matrix, with and without the presence of geranyl-geraniol, as well as testing against control groups with PBS injections or collagen matrix containing PBS instead of GGOH. This was followed by a histological evaluation of the capillary-like structures.

RESULTS

Zoledronate inhibits the sprouting of blood vessels into a collagen matrix in vivo; in the presence of GGOH this effect is significantly weakened by a factor of 3.9 (p = 0.00068).

CONCLUSION

This work commits to the investigation of the pathophysiology of BP-ONJ and shows a possible causal therapeutic path via the topical application of GGOH.

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.

A Drug Holiday Reduces the Frequency and Severity of Medication-Related Osteonecrosis of the Jaw in a Minipig Model

Treatment of medication-related osteonecrosis of the jaw (MRONJ) is challenging and no clear consensus has been achieved. This study investigated preventive measures recommended for tooth extractions under antiresorptive (AR) treatment and the role of discontinuation of AR therapy to avoid the onset of MRONJ in a minipig model. Thirty-six Göttingen minipigs were divided into four groups. Group 1 (negative control): tooth extractions but no zoledronate (ZOL). Group 2 (positive control): weekly ZOL infusions for 12 weeks followed by tooth extractions without wound management followed by 8 weeks of ZOL treatment. Group 3: weekly ZOL infusions for 12 weeks followed by tooth extractions; surgical wound management (resection of sharp bone edges, mucoperiosteal coverage); and continuation of ZOL infusions for 8 weeks plus antibiotic treatment. Group 4: 12 weeks of ZOL infusions followed by a drug holiday for 6 weeks. Tooth extractions with preventive wound management followed by antibiotic treatment for 8 weeks but no ZOL infusions. Jawbones were subjected to macroscopic, radiological (CT and micro-CT) and histopathological investigations. No clinical cases of MRONJ were observed in the negative group, in the positive control all animals developed MRONJ. Group 3 developed MRONJ in 83% of cases. With a drug holiday, 40% developed MRONJ in areas of tooth extraction. This is the first large animal model that reduces the occurrence of MRONJ following tooth extraction by the implementation of a drug holiday combined with antibiotic prophylaxis and smoothening of sharp bony edges. © 2020 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research..

Mitigating osteonecrosis of the jaw (ONJ) through preventive dental care and understanding of risk factors

It is well established that alterations in phosphate metabolism have a profound effect on hard and soft tissues of the oral cavity. The present-day clinical form of osteonecrosis of the jaw (ONJ) was preceded by phosphorus necrosis of the jaw, ca. 1860. The subsequent removal of yellow phosphorus from matches in the early 20th century saw a parallel decline in "phossy jaw" until the early 2000s, when similar reports of unusual jaw bone necrosis began to appear in the literature describing jaw necrosis in patients undergoing chemotherapy and concomitant steroid and bisphosphonate treatment. Today, the potential side effect of ONJ associated with medications that block osteoclast activity (antiresorptive) is well known, though the mechanism remains unclear and the management and outcomes are often unsatisfactory. Much of the existing literature has focused on the continuing concerns of appropriate use of bisphosphonates and other antiresorptive medications, the incomplete or underdeveloped research on ONJ, and the use of drugs with anabolic potential for treatment of osteoporosis. While recognizing that ONJ is a rare occurrence and ONJ-associated medications play an important role in fracture risk reduction in osteoporotic patients, evidence to date suggests that health care providers can lower the risk further by dental evaluations and care prior to initiating antiresorptive therapies and by monitoring dental health during and after treatment. This review describes the current clinical management guidelines for ONJ, the critical role of dental-medical management in mitigating risks, and the current understanding of the effects of predominantly osteoclast-modulating drugs on bone homeostasis.

Aminobisphosphonate-treated ewes as a model of osteonecrosis of the jaw and of dental implant failure

BACKGROUND

Bisphosphonate (BP)-related osteonecrosis of the jaw (BRONJ) and dental implant failure are two negative side effects of chronic aminoBP treatment.

METHODS

Eleven ovariectomized (OVX) ewes and four ewes subjected to sham surgery (SHAM) were treated as follows: OVX (n = 5): OVX plus saline solution; zoledronic acid-treated group (ZOL) (n = 6): OVX plus ZOL; SHAM (n = 4): SHAM plus saline solution. Extraction of the first upper molar was performed at 1 year, dental implant placement at 2 years, and sacrifice at 28 months.

RESULTS

Implants remained in place in SHAM and OVX ewes but were lost in all ZOL ewes. ZOL sheep (2/6) showed inflammation and necrotic bone at mandibular region. No differences in serum calcium (Ca), inorganic phosphate (Pi) or 25-hydroxyvitamin D were observed, whereas bone alkaline phosphatase levels decreased in the three studied groups (P < 0.05). The significantly lowest levels of carboxy-terminal telopeptide of type I collagen were observed in ZOL (P < 0.05), and showed no differences between SHAM and OVX. OVX showed the lowest and ZOL the highest Ca and Pi contents in femur and maxilla (P < 0.05). Bone volume (BV/TV%) and iliac crest were similar at baseline and at month 4. At the end of the study, BV/TV%, proximal femur and hemi-mandible bone mineral content and bone mineral density, and trabeculae number were similar in SHAM and ZOL, and lower in OVX (P < 0.05).

CONCLUSION

All ZOL-treated ewes on a schedule similar to that used in cancer patients showed extensive suppression of bone remodeling and implant failure. Some of the ZOL ewes developed BRONJ.

Further development of the MRONJ minipig large animal model

Medication-related osteonecrosis of the jaw (MRONJ) is a rare but serious and potentially severe side effect of antiresorptive therapy with bisphosphonates or denosumab. Recently, a large animal minipig MRONJ model was introduced which led to early necrotic lesions in the majority of extraction sites after bisphosphonate administration. The aim of this project was to modify the preoperative cumulative bisphosphonate dose (zoledronate) and hereby firstly to demonstrate the reliability and reproducibility of the established model. Secondly, the MRONJ lesions should be carefully investigated using clinical and μCT as well as detailed histological analyses. Twelve 1.5-year-old Göttingen minipigs were divided into three groups. In group 1 (n = 3) minipigs received weekly doses of zoledronate intravenously (0.05 mg/kg bodyweight) for 20 weeks. No interventions were performed. In group 2 (n = 6) animals received the identical zoledronate dosage as animals in group 1 and tooth extractions of two premolars (PM 2 and 4) in each jaw (maxilla and mandible) were performed after 12 weeks. Group 3 (n = 3) served as tooth extraction only control (no zoledronate administrations). The jaw-bones were subjected to detailed macroscopic, radiological and histological investigations. All extraction sites (24/24) in animals of group 2 showed clinical, radiological and histological signs of MRONJ (mainly stage II), whereas no bone necrosis was found in group 3. Animals of group 1 and group 2 showed further MRONJ lesions in areas where infections (periodontitis) were present. This is the first large animal model to show a 100% incidence of MRONJ at all extraction sites in bisphosphonate pretreated animals (group 2). In addition, in this preclinical model for MRONJ it is shown that tooth extractions are not mandatory for a MRONJ manifestation. MRONJ also developed in areas of gingival or periodontal infections.

The influence of geranylgeraniol on microvessel sprouting after bisphosphonate substitution in an in vitro 3D-angiogenesis assay

OBJECTIVES

Recent studies focused on angiogenesis in the pathophysiology of bisphosphonate-associated osteonecrosis of the jaws (BP-ONJ) and identified geranylgeraniol (GGOH) as a feasible option for BP-ONJ therapy. This study investigated the influence of GGOH on microvessel sprouting after BP-incubation in vitro.

MATERIALS AND METHODS

Ten experimental set-ups were randomly designed in an in vitro 3D-angiogenesis assay. Two groups included HUVEC cell spheroids with and without (±) GGOH substitution as controls and eight groups pairwise contained either clodronate or the nitrogen-containing bisphosphonates (N-BP) ibandronate, pamidronate, and zoledronate ± GGOH. The size of the cell spheroids including the outbranching sprouts (SpS) as well as the density (SpD) and length of the sprouts (SpL) were analyzed by a grid system after 0, 24, 48, and 72 h.

RESULTS

For controls and NN-BP clodronate, no significant differences at any tested parameter and any point of measurement could be detected within the experimental set-ups ± GGOH (p each ≥0.05). For N-BP ibandronate, the experimental set-ups +GGOH showed a significantly increased SpS, SpD, and SpL after 48 and 72 h (p each ≤0.002) compared to the experimental set-ups -GGOH. For N-BPs pamidronate and zoledronate, the experimental set-ups + GGOH demonstrated a significantly increased SpS, SpD, and SpL after 24, 48, and 72 h (p each ≤0.001) compared to the experimental set-ups -GGOH.

CONCLUSIONS

The strong negative influence of N-BPs on microvessel sprouting could be significantly reversed by GGOH.

CLINICAL RELEVANCE

Since supportive therapeutic options for BP-ONJ are lacking, GGOH might be a promising substitute for BP-ONJ prevention and therapy.