Zoledronate induces bisphosphonate-related osteonecrosis of the jaw in osteopenic sheep

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.

Is the Use of Bisphosphonates Putting Horses at Risk? An Osteoclast Perspective

Simple Summary

Bisphosphonates are a group of drugs that intervene in the bone resorption process, producing cellular death of osteoclasts. These drugs are used for skeletal conditions, such as osteoporosis in humans, and are available for veterinary medical use. Clodronate and tiludronate are bisphosphonates approved for the treatment of navicular syndrome in horses over four years old. However, these drugs are sometimes used in juvenile animals under exercise, where osteoclast activity is higher. Bisphosphonate use in juvenile and/or exercising animals could have adverse effects, including maladaptation to exercise or accumulation of microdamage. Furthermore, bisphosphonates can be bound to the skeleton for several years, resulting in a prolonged effect with no pharmaceutical reversal available. This review presents an overview of osteoclast function and a review of bisphosphonate characteristics, mechanisms of action, and side effects in order to contextualize the potential for adverse/side effects in young or exercising animals.

Abstract

Osteoclasts are unique and vital bone cells involved in bone turnover. These cells are active throughout the individual’s life and play an intricate role in growth and remodeling. However, extra-label bisphosphonate use may impair osteoclast function, which could result in skeletal microdamage and impaired healing without commonly associated pain, affecting bone remodeling, fracture healing, and growth. These effects could be heightened when administered to growing and exercising animals. Bisphosphonates (BPs) are unevenly distributed in the skeleton; blood supply and bone turnover rate determine BPs uptake in bone. Currently, there is a critical gap in scientific knowledge surrounding the biological impacts of BP use in exercising animals under two years old. This may have significant welfare ramifications for growing and exercising equids. Therefore, future research should investigate the effects of these drugs on skeletally immature horses.

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.

Titanium implant alters the effect of zoledronic acid on the behaviour of endothelial cells

OBJECTIVES

To evaluate the effect of zoledronic acid (ZA) on human umbilical vein endothelial cells (HUVECs) attached to different surfaces.

MATERIALS AND METHODS

A total of three groups were evaluated in this study: sandblasting and acid etching (SLA) + HUVECs; mechanically polished (MP) + HUVECs; and plastic cell culture plates + HUVECs. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, surface roughness and water contact angle were tested for titanium surface characterisation. ZA was added at different concentrations (0, 1, 10, 50 and 100 μM). Cell adhesion, proliferation, viability, apoptosis and gene expression were evaluated.

RESULTS

Mechanically polished and SLA surfaces showed negative effects on cell adhesion and proliferation and promoted cell apoptosis with 100 μM ZA (p < .05). The highest expression of intercellular adhesion molecule-1 (ICAM-1) and angiopoietin-1 was found on SLA surfaces (p < .01). The lowest expression of platelet-endothelial cell adhesion molecule-1 and ICAM-1 was found on MP surfaces (p < .05). A significant decrease in von Willebrand factor was detected on MP and SLA surfaces (p < .001).

CONCLUSIONS

Zoledronic acid has an anti-angiogenic effect on HUVECs attached to titanium implants, while the SLA surface might stimulate HUVECs to express angiogenic and adhesive factor genes despite ZA treatment.

Medication-Related Osteonecrosis of the Jaw (MRONJ): Are Antiresorptive Drugs the Main Culprits or Only Accomplices? The Triggering Role of Vitamin D Deficiency

Osteonecrosis of the jaw (ONJ) is a severe clinical condition characterized mostly but not exclusively by an area of exposed bone in the mandible and/or maxilla that typically does not heal over a period of 6-8 weeks. The diagnosis is first of all clinical, but an imaging feedback such as Magnetic Resonance is essential to confirm clinical suspicions. In the last few decades, medication-related osteonecrosis of the jaw (MRONJ) has been widely discussed. From the first case reported in 2003, many case series and reviews have appeared in the scientific literature. Almost all papers concerning this topic conclude that bisphosphonates (BPs) can induce this severe clinical condition, particularly in cancer patients. Nevertheless, the exact mechanism by which amino-BPs would be responsible for ONJ is still debatable. Recent findings suggest a possible alternative explanation for BPs role in this pattern. In the present work we discuss how a condition of osteomalacia and low vitamin D levels might be determinant factors.

Microcirculatory consequences of limb ischemia/reperfusion in ovariectomized rats treated with zoledronic acid

Background

Nitrogen-containing bisphosphonates (BIS) are potent therapeutics in osteoporosis, but their use may result in osteonecrotic side-effects in the maxillofacial region. Periosteal microcirculatory reactions may contribute to the development of bone-healing complications, particularly in osteoporotic bones, where ischemia–reperfusion (IR) events often develop during orthopaedic/trauma interventions. The effect of BIS on the inflammatory reactions of appendicular long bones has not yet been evaluated; thus, we aimed to examine the influence of chronic zoledronate (ZOL) administration on the periosteal microcirculatory consequences of hindlimb IR in osteopenic rats.

Materials and methods

Twelve-week-old female Sprague–Dawley rats were ovariectomized (OVX) or sham-operated, and ZOL (80 μg/kg iv, weekly) or a vehicle was administered for 8 weeks, 4 weeks after the operation. At the end of the pre-treatment protocols, 60-min limb ischemia was induced, followed by 180-min reperfusion. Leukocyte-endothelial interactions were quantitated in tibial periosteal postcapillary venules by intravital fluorescence videomicroscopy. CD11b expression of circulating polymorphonuclear leukocytes (PMN, flow cytometry) and plasma TNF-alpha levels (ELISA) were also determined. Two-way RM ANOVA followed by the Holm–Sidak and Dunn tests was used to assess differences within and between groups, respectively.

Results

Limb IR induced significant increases in PMN rolling and firm adhesion in sham-operated and OVX rats, which were exacerbated temporarily in the first 60 min of reperfusion by a ZOL treatment regimen. Postischemic TNF-alpha values showed a similar level of postischemic elevations in all groups, whereas CD11b expression only increased in rats not treated with ZOL.

Conclusions

The present data do not show substantial postischemic periosteal microcirculatory complications after chronic ZOL treatment either in sham-operated or OVX rats. The unaltered extent of limb IR-induced local periosteal microcirculatory reactions in the presence of reduced CD11b adhesion molecule expression on circulating PMNs, however, may be attributable to local endothelial injury/activation caused by ZOL.

Medication-related osteonecrosis of the jaw in a minipig model: Parameters for developing a macroscopic, radiological, and microscopic grading scheme

OBJECTIVES

To devise a macroscopic, radiological, and histological scale for assessing pathological changes associated with medication-related osteonecrosis of the jaw in a minipig model.

MATERIALS AND METHODS

Medication-related osteonecrosis of the jaw was induced in Göttingen minipigs by weekly intravenous administration of bisphosphonate (zoledronic acid) combined with a tooth extraction procedure. Controls either did not receive zoledronic acid or did not undergo tooth extraction. After 20 weeks, minipigs were euthanized and underwent computed tomography and micro-computed tomography scanning. The mandible underwent additional histological examination.

RESULTS

The most consistent macroscopic findings in animals that had developed bisphosphonate-related osteonecrosis of the jaw (BRONJ) were necrotic, denuded bone, and formation of fistula and pus. Under radiological examination, impaired extraction socket healing, decrease in attenuation of bone beneath the extraction site, and periosteal reaction were observed. Under histological examination, demineralization of the extracellular bone matrix, denuding of bone, and osteonecrosis were recorded.

CONCLUSION

These parameters were used to develop a scoring system for grading BRONJ.

Pathogenesis of medication-related osteonecrosis of the jaw: a comparative study of in vivo and in vitro trials

Objective This study was performed to determine whether the results of prevailing in vivo and in vitro studies offer a reliable model for investigation of medication-related osteonecrosis of the jaw (MRONJ). Methods Embase, Medline, and the Cochrane Library were searched for articles published from September 2003 to June 2017 involving experimental approaches to the pathogenesis of MRONJ. In vivo and in vitro trials were analyzed with respect to the scientific question, study design, methodology, and results. Results Of 139 studies, 87, 46, and 6 conducted in vivo, in vitro, and both in vivo and in vitro experiments, respectively. Rats, mice, dogs, minipigs, sheep, and rabbits were the preferred animal models used. Osteoblasts, osteoclasts, fibroblasts, keratinocytes, macrophages, and human umbilical vein endothelial cells were the preferred cell types. Zoledronate, alendronate, ibandronate, and risedronate were the most frequent bisphosphonates used. MRONJ was most reliably induced in minipigs because of the close relationship with human bone physiology. In vitro studies showed that reduced viability, growth, and migration of cells in the bone and soft tissues were causative for MRONJ. Other than exposed jawbone after tooth extraction, no reliable cofactors were found. Conclusion The minipig is the most suitable animal model for MRONJ.

Role of Periapical Diseases in Medication-Related Osteonecrosis of the Jaws

Objective

The present study aimed to investigate the role of periapical diseases in inducing medication-related osteonecrosis of the jaws (MRONJ) using an ovariectomized (OVX) mice model.

Materials and Methods

Twenty C57BL/6N female mice were randomly assigned to two groups. All mice were subjected to bilateral ovariectomy and then treated with oncologic dose of zoledronic acid (ZA) or vehicle for twelve weeks. Eight weeks after commence of drug administration, a pulpal exposure (PE) operation was performed on the first right lower molar to induce periapical periodontitis; the contralateral non-PE tooth was used as control. All animals were sacrificed four weeks after pulpal exposure, and the mandibles were harvested for radiological and histomorphometrical analysis.

Results

Micro computed tomography (μ-CT) examination demonstrated that periapical diseases significantly increased alveolar bone resorption, and the resorption was greatly attenuated by ZA treatment. Concurrent ZA therapy significantly increased bone density and histological osteocyte necrosis in the presence of periapical lesions.

Conclusion

ZA treatment reduced bone absorption resulting from periapical disease but increased the risk of developing MRONJ in the ovariectomized mouse model.

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.

Evaluation of BP-ONJ in osteopenic and healthy sheep: comparing ZTE-MRI with µCT

OBJECTIVES

Bisphosphonate-associated osteonecrosis of the jaw (BP-ONJ) is a side effect of antiresorptive treatment that is increasingly prescribed for patients with osteoporosis or malignant diseases with bone metastases. Surgical treatment of BP-ONJ requires adequate pre-operative imaging. To date, CT is the imaging standard in clinical routine; however, defining the extent of the pathological area is difficult and soft tissues are poorly displayed. MRI with zero echo time (ZTE-MRI) to display hard tissues enables a precise display of calcified structures and soft tissues for the delineation of bone necrosis and soft-tissue reactions.

METHODS

BP-ONJ was induced in eight sheep by extraction of two premolars in the left mandible and zoledronate (ZOL) administration. Eight sheep without ZOL administration served as the control group. Four sheep of each main group underwent osteopenia induction via ovariectomy, glucocorticoid administration and a calcium-free diet. After sacrifice, the area of tooth extraction was harvested and scanned with micro-CT (µCT) and ZTE-MRI. Two trained dentists analyzed digital imaging and communications in medicine data sets using three-dimensional imaging software. The periosteal reaction and the remaining extraction sockets were measured.

RESULTS

BP-ONJ was evident, and the remaining extraction sockets were observed in all animals treated with ZOL. Periosteal reactions were more pronounced in animals treated with ZOL, and they appeared broader in ZTE-MRI.

CONCLUSIONS

BP-ONJ lesions in the sheep mandible can be detected using µCT and ZTE-MRI. Although illustration of sequester was more consistent using the µCT, ZTE-MRI was advantageous in evaluation of periosteal reaction.