Inhibition of necrotic actions of nitrogen-containing bisphosphonates (NBPs) and their elimination from bone by etidronate (a non-NBP): a proposal for possible utilization of etidronate as a substitution drug for NBPs

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.

Release of Nitrogen-Containing Bisphosphonates (NBPs) from Hydroxyapatite by Non-NBPs and by Pyrophosphate

Bisphosphonates (BPs) are major anti-bone-resorptive drugs. Among them, the nitrogen-containing BPs (NBPs) exhibit much stronger anti-bone-resorptive activities than non-nitrogen-containing BPs (non-NBPs). However, BP-related osteonecrosis of the jaw (BRONJ) has been increasing without effective strategies for its prevention or treatment. The release of NBPs (but not non-NBPs) from NBP-accumulated jawbones has been supposed to cause BRONJ, even though non-NBPs (such as etidronate (Eti) and clodronate (Clo)) are given at very high doses because of their low anti-bone-resorptive activities. Our murine experiments have demonstrated that NBPs cause inflammation/necrosis at the injection site, and that Eti and Clo can reduce or prevent the inflammatory/necrotic effects of NBPs by inhibiting their entry into soft-tissue cells. In addition, our preliminary clinical studies suggest that Eti may be useful for treating BRONJ. Notably, Eti, when administered together with an NBP, reduces the latter's anti-bone-resorptive effect. Here, on the basis of the above background, we examined and compared in vitro interactions of NBPs, non-NBPs, and related substances with hydroxyapatite (HA), and obtained the following results. (i) NBPs bind rapidly to HA under pH-neutral conditions. (ii) At high concentrations, Eti and Clo inhibit NBP-binding to HA and rapidly expel HA-bound NBPs (potency Eti>>Clo). (iii) Pyrophosphate also inhibits NBP-binding to HA and expels HA-bound NBPs. Based on these results and those reported previously, we discuss (i) possible anti-BRONJ strategies involving the use of Eti and/or Clo to reduce jawbone-accumulated NBPs, and (ii) a possible involvement of pyrophosphate-mediated release of NBPs as a cause of BRONJ.

The Case of Medication-Related Osteonecrosis of the Jaw Addressed from a Pathogenic Point of View. Innovative Therapeutic Strategies: Focus on the Most Recent Discoveries on Oral Mesenchymal Stem Cell-Derived Exosomes

Bisphosphonates-related osteonecrosis of the jaw (BRONJ) was firstly reported by Marx in 2003. Since 2014, the term medication-related osteonecrosis of the jaw (MRONJ) is recommended by the American Association of Oral and Maxillofacial Surgeons (AAOMS). Development of MRONJ has been associated to the assumption of bisphosphonates but many MRONJ-promoting factors have been identified. A strong involvement of immunity components has been suggested. Therapeutic intervention includes surgical and non-surgical treatments, as well as regenerative medicine procedures for the replacement of the lost tissues. The literature confirms that the combination of mesenchymal stem cells (MSCs), biomaterials and local biomolecules can support the regeneration/repair of different structures. In this review, we report the major open topics in the pathogenesis of MRONJ. Then, we introduce the oral tissues recognized as sources of MSCs, summing up in functional terms what is known about the exosomes release in physiological and pathological conditions.

[Basic Studies on the Mechanism, Prevention, and Treatment of Osteonecrosis of the Jaw Induced by Bisphosphonates]

Since the first report in 2003, bisphosphonate-related osteonecrosis of the jaw (BRONJ) has been increasing, without effective clinical strategies. Osteoporosis is common in elderly women, and bisphosphonates (BPs) are typical and widely used anti-osteoporotic or anti-bone-resorptive drugs. BRONJ is now a serious concern in dentistry. As BPs are pyrophosphate analogues and bind strongly to bone hydroxyapatite, and the P-C-P structure of BPs is non-hydrolysable, they accumulate in bones upon repeated administration. During bone-resorption, BPs are taken into osteoclasts and exhibit cytotoxicity, producing a long-lasting anti-bone-resorptive effect. BPs are divided into nitrogen-containing BPs (N-BPs) and non-nitrogen-containing BPs (non-N-BPs). N-BPs have far stronger anti-bone-resorptive effects than non-N-BPs, and BRONJ is caused by N-BPs. Our murine experiments have revealed the following. N-BPs, but not non-N-BPs, exhibit direct and potent inflammatory/necrotic effects on soft-tissues. These effects are augmented by lipopolysaccharide (the inflammatory component of bacterial cell-walls) and the accumulation of N-BPs in jawbones is augmented by inflammation. N-BPs are taken into soft-tissue cells via phosphate-transporters, while the non-N-BPs etidronate and clodronate inhibit this transportation. Etidronate, but not clodronate, has the effect of expelling N-BPs that have accumulated in bones. Moreover, etidronate and clodronate each have an analgesic effect, while clodronate has an anti-inflammatory effect via inhibition of phosphate-transporters. These findings suggest that BRONJ may be induced by phosphate-transporter-mediated and infection-promoted mechanisms, and that etidronate and clodronate may be useful for preventing and treating BRONJ. Our clinical trials support etidronate being useful for treating BRONJ, although additional clinical trials of etidronate and clodronate are needed.

Effects of local administration of tiludronic acid on experimental periodontitis in diabetic rats

BACKGROUND

Tiludronic acid (TIL) presents antiresorptive and anti-inflammatory properties and has not been evaluated in the periodontitis-diabetes mellitus (DM) association to date, to the best knowledge of the authors. This study evaluates effects of local administration of TIL on experimental periodontitis (EP) in rats with streptozotocin-induced DM.

METHODS

Thirty-two animals (Rattus norvegicus albinus, Wistar) were divided into groups DM/C (Control), DM/EP, DM/EP/TIL1, and DM/EP/TIL3. In EP groups, a ligature was placed around mandibular first molars. In groups DM/EP/TIL1 and DM/EP/TIL3, TIL solutions (1 and 3 mg/kg, respectively) were injected into the gingival tissue of mandibular molars every other day for 10 days, until euthanasia. Periodontal tissues were analyzed by microcomputed tomography (micro-CT), histomorphometry, immunohistochemistry (tartrate-resistant acid phosphatase [TRAP], receptor activator of nuclear factor-κB ligand [RANKL], osteoprotegerin, cleaved caspase 3), and quantitative reverse transcription-polymerase chain reaction (interleukin [IL]-1β, vascular endothelial growth factor [VEGF]).

RESULTS

In micro-CT analyses, groups DM/EP/TIL1 and DM/EP/TIL3 presented reduced alveolar bone resorption (P < 0.05). Group DM/EP/TIL3 presented decreased attachment loss (P < 0.05). The amount of TRAP-positive multinucleated cells was decreased in TIL groups (P < 0.05). Group DM/EP/TIL3 presented a lower immunolabeling pattern for RANKL (P < 0.05). TIL treatment decreased genic expression of IL-1β, and in group DM/EP/TIL3, expression of VEGF was increased (P < 0.05).

CONCLUSION

Local administration of TIL promoted a protective effect against tissue destruction in EP in diabetic rats, and the dosage of 3 mg/kg of TIL promoted the best results regarding its antiresorptive and anti-inflammatory effects.

Medication-Related Osteonecrosis of the Jaw: MASCC/ISOO/ASCO Clinical Practice Guideline

PURPOSE

To provide guidance regarding best practices in the prevention and management of medication-related osteonecrosis of the jaw (MRONJ) in patients with cancer.

METHODS

Multinational Association of Supportive Care in Cancer/International Society of Oral Oncology (MASCC/ISOO) and ASCO convened a multidisciplinary Expert Panel to evaluate the evidence and formulate recommendations. Guideline development involved a systematic review of the literature and a formal consensus process. PubMed and EMBASE were searched for studies of the prevention and management of MRONJ related to bone-modifying agents (BMAs) for oncologic indications published between January 2009 and December 2017. Results from an earlier systematic review (2003 to 2008) were also included.

RESULTS

The systematic review identified 132 publications, only 10 of which were randomized controlled trials. Recommendations underwent two rounds of consensus voting.

RECOMMENDATIONS

Currently, MRONJ is defined by (1) current or previous treatment with a BMA or angiogenic inhibitor, (2) exposed bone or bone that can be probed through an intraoral or extraoral fistula in the maxillofacial region and that has persisted for longer than 8 weeks, and (3) no history of radiation therapy to the jaws or metastatic disease to the jaws. In patients who initiate a BMA, preventive care includes comprehensive dental assessments, discussion of modifiable risk factors, and avoidance of elective dentoalveolar surgery (ie, surgery that involves the teeth or contiguous alveolar bone) during BMA treatment. It remains uncertain whether BMAs should be discontinued before dentoalveolar surgery. Staging of MRONJ should be performed by a clinician with experience in the management of MRONJ. Conservative measures comprise the initial approach to MRONJ treatment. Ongoing collaboration among the dentist, dental specialist, and oncologist is essential to optimal patient care.

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.

Paradoxical side effects of bisphosphonates on the skeleton: What do we know and what can we do?

Bisphosphonates are considered the most effective drugs for controlling adult and pediatric osteolytic diseases. Although they have been used successfully for many years, several side effects, such as osteonecrosis of the jaw, delayed dental eruption, atypical femoral fracture, and alterations to the bone growth system, have been described. After an overview of nitrogenous bisphosphonate, the purpose of this article is to describe their mechanisms of action and current applications, review the preclinical and clinical evidence of their side effects in the skeleton ("what we know"), and describe current recommendations for preventing and managing these effects ("what we can do"). Finally, promising future directions on how to limit the occurrence of these side effects will be presented.

Evaluation of the bisphosphonate effect on stem cells derived from jaw bone and long bone rabbit models: A pilot study

BACKGROUND AND OBJECTIVE

Bisphosphonates have been widely used and the number of patients experiencing medication-related osteonecrosis of the jaw (MRONJ) has been increasing. This study was designed to evaluate the effect of zoledronate on stem cells derived from different tissues.

DESIGN

Stem cells derived from four different tissues were compared using rabbit models (JPO: periosteum from the jaw bone (mandible), JBM: bone marrow from the jaw bone, LPO: periosteum from long bone (tibia), and LBM: bone marrow from long bone). Stem cells were grown in the presence of zoledronate at final concentrations ranging from 10-6M to 10-10M. Morphology was viewed under an inverted microscope, and the analysis of cell proliferation was performed using a Cell Counting Kit-8 (CCK-8) on days 1, 2, 4, and 7.

RESULTS

The CCK-8 results for LBM showed that the increase of CCK-8 values was correlated with a longer incubation time. Compared to the untreated control, growth in the presence of zoledronate at 10-10M and 10-8M resulted in decreased CCK-8 values for LBM on day 7 (P<0.05). The CCK-8 results for JBM, LPO, and JPO on days 1, 2, 4, and 7 showed that the presence of zoledronate did not produce statistically significant changes compared with the untreated control.

CONCLUSION

Zoledronate in the tested concentrations from JBM, LPO, and JPO did not produce noticeable alterations in the viability of mesenchymal stem cells. This in vitro experiment suggests that the occurrence of MRONJ solely in the oral cavity is not due to differences in the cellular proliferation of stem cells in the response to zoledronate.

Etidronate down-regulates Toll-like receptor (TLR) 2 ligand-induced proinflammatory cytokine production by inhibiting NF-κB activation

BACKGROUND

Etidronate is a non-nitrogen-containing bisphosphonate (non-NBP) used for anti-bone resorptive therapy as well as having inhibitory effects on atherosclerotic plaques. The present study examined the effects of etidronate on the production of proinflammatory cytokines and chemokines by the macrophage-like cell line, J774.1, incubated with Pam₃Cys-Ser-(Lys)₄ (Pam₃CSK₄, a Toll-like receptor (TLR) 2 agonist) and lipid A (a TLR4 agonist).

METHODS

J774.1 cells and human monocytic THP-1 cells were pretreated with or without etidronate for 5min, and then incubated with or without Pam₃CSK₄ or lipid A for 24h. Levels of secreted interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), and macrophage inflammatory protein-1α (MIP-1α) in culture supernatants were measured by enzyme-linked immunosorbent assay (ELISA). Cytotoxicity was determined by LDH activity in the supernatants. We also examined the effects of etidronate on the activation of nuclear factor-κB (NF-κB) and p38 mitogen-activated protein kinase (MAPK) in J774.1 cells by ELISA and Western blotting.

RESULTS

Treatment of J774.1 cells with etidronate down-regulated TLR2 ligand-induced production of IL-6, TNF-α, MCP-1, and MIP-1α. Etidronate also inhibited Pam₃CSK₄-induced MCP-1 and TNF-α production by THP-1 cells. However, etidronate did not induce cytotoxicity and reduced lipid A-induced cytotoxicity in J774.1 cells. In addition, this agent did not down-regulate TLR4 ligand-induced proinflammatory cytokine production. Furthermore, etidronate inhibited the translocation of NF-κB but not p38 MAPK in J774.1 cells stimulated with Pam₃CSK₄ or lipid A.

CONCLUSION

Etidronate likely inhibits proinflammatory cytokine production in J774.1 cells by suppressing NF-κB activation in the TLR2 and not the TLR4 pathway.

A Strategy against the Osteonecrosis of the Jaw Associated with Nitrogen-Containing Bisphosphonates (N-BPs): Attempts to Replace N-BPs with the Non-N-BP Etidronate

Bisphosphonate (BP)-related osteonecrosis of the jaw (BRONJ) can occur when enhanced bone-resorptive diseases are treated with nitrogen-containing BPs (N-BPs). Having previously found, in mice, that the non-N-BP etidronate can (i) reduce the inflammatory/necrotic effects of N-BPs by inhibiting their intracellular entry and (ii) antagonize the binding of N-BPs to bone hydroxyapatite, we hypothesized that etidronate-replacement therapy (Eti-RT) might be useful for patients with, or at risk of, BRONJ. In the present study we examined this hypothesis. In each of 25 patients receiving N-BP treatment, the N-BP was discontinued when BRONJ was suspected and/or diagnosed. After consultation with the physician-in-charge and with the patient's informed consent, Eti-RT was instituted in one group according to its standard oral prescription. We retrospectively compared this Eti-RT group (11 patients) with a non-Eti-RT group (14 patients). The Eti-RT group (6 oral N-BP patients and 5 intravenous N-BP patients) and the non-Eti-RT group (5 oral N-BP patients and 9 intravenous N-BP patients) were all stage 2-3 BRONJ. Both in oral and intravenous N-BP patients (particularly in the former patients), Eti-RT promoted or tended to promote the separation and removal of sequestra and thereby promoted the recovery of soft-tissues, allowing them to cover the exposed jawbone. These results suggest that Eti-RT may be an effective choice for BRONJ caused by either oral or intravenous N-BPs and for BRONJ prevention, while retaining a level of anti-bone-resorption. Eti-RT may also be effective at preventing BRONJ in N-BP-treated patients at risk of BRONJ. However, prospective trials are still required.

Inflammatory Effects of Nitrogen-Containing Bisphosphonates (N-BPs): Modulation by Non-N-BPs

Bisphosphonates (BPs) are used against diseases with enhanced bone resorption. Those classed as nitrogen-containing BPs (N-BPs) exhibit much stronger anti-bone-resorptive effects than non-nitrogen-containing BPs (non-N-BPs). However, N-BPs carry the risk of inflammatory/necrotic side effects. Depending on their side-chains, BPs are divided structurally into cyclic and non-cyclic types. We previously found in mice that etidronate and clodronate (both non-cyclic non-N-BPs) could reduce the inflammatory effects of all three N-BPs tested (cyclic and non-cyclic types), possibly by inhibiting their entry into soft-tissue cells via SLC20 and/or SLC34 phosphate transporters. Tiludronate is the only available cyclic non-N-BP, but its effects on N-BPs' side effects have not been examined. Here, we compared the effects of etidronate, clodronate, and tiludronate on the inflammatory effects of six N-BPs used in Japan [three cyclic (risedronate, zoledronate, minodronate) and three non-cyclic (pamidronate, alendronate, ibandronate)]. Inflammatory effects were evaluated in mice by measuring the hind-paw-pad swelling induced by subcutaneous injection of an N-BP (either alone or mixed with a non-N-BP) into the hind-paw-pad. All of six N-BPs tested induced inflammation. Etidronate, clodronate, and the SLC20/34 inhibitor phosphonoformate inhibited this inflammation. Tiludronate inhibited the inflammatory effects of all N-BPs except ibandronate and minodronate, which have higher molecular weights than the other N-BPs. The mRNAs of SLC20a1, SLC20a2, and SLC34a2 (but not of SLC34a1 and SLC34a3) were detected in the soft-tissues of hind-paw-pads. These results suggest that etidronate, clodronate, and phosphonoformate may act non-selectively on phosphate transporter members, while tiludronate may not act on those transporting N-BPs of higher molecular weights.

The Bisphosphonates Clodronate and Etidronate Exert Analgesic Effects by Acting on Glutamate- and/or ATP-Related Pain Transmission Pathways

Bisphosphonates (BPs) are typical anti-bone-resorptive drugs, with nitrogen-containing BPs (N-BPs) being stronger than non-nitrogen-containing BPs (non-N-BPs). However, N-BPs have inflammatory/necrotic effects, while the non-N-BPs clodronate and etidronate lack such side effects. Pharmacological studies have suggested that clodronate and etidronate can (i) prevent the side effects of N-BPs in mice via inhibition of the phosphate transporter families SLC20 and/or SLC34, through which N-BPs enter soft-tissue cells, and (ii) also inhibit the phosphate transporter family SLC17. Vesicular transporters for the pain transmitters glutamate and ATP belong to the SLC17 family. Here, we examined the hypothesis that clodronate and etidronate may enter neurons through SLC20/34, then inhibit SLC17-mediated transport of glutamate and/or ATP, resulting in their decrease, and thereby produce analgesic effects. We analyzed in mice the effects of various agents [namely, intrathecally injected clodronate, etidronate, phosphonoformic acid (PFA; an inhibitor of SLC20/34), and agonists of glutamate and ATP receptors] on the nociceptive responses to intraplantar injection of capsaicin. Clodronate and etidronate produced analgesic effects, and these effects were abolished by PFA. The analgesic effects were reduced by N-methyl-D-aspartate (agonist of the NMDA receptor, a glutamate receptor) and α,β-methylene ATP (agonist of the P2X-receptor, an ATP receptor). SLC20A1, SLC20A2, and SLC34A1 were detected within the mouse lumbar spinal cord. Although we need direct evidence, these results support the above hypothesis. Clodronate and etidronate may be representatives of a new type of analgesic drug. Such drugs, with both anti-bone-resorptive and unique analgesic effects without the adverse effects associated with N-BPs, might be useful for osteoporosis.

Differential modulation of zoledronate and etidronate in osseous healing of an extracted socket and tibia defect

OBJECTIVES

Osteonecrosis of the jaw has been increasing after dentoalveolar surgery in patients treated with an antiresorptive bisphosphonate (BP), especially strong zoledronate (ZA). The pathophysiology underlying why osteonecrosis occurs exclusively in the jaw bone remains unclear. This study investigated skeletal site-specific bone healing during the use of BPs to explore the preferential incidence of osteonecrosis of the jaw bone.

STUDY DESIGN

Extraction of mandibular molar and creation of a tibia defect were performed in rats 2 weeks after weekly intravenous injections with the potent ZA and the weaker BP etidronate. Bone healing was evaluated radiographically and histologically 1 and 4 weeks after defect creation.

RESULTS

Bone healing at the extracted socket showed that resorption precedes bone formation, while it was the opposite at the tibia defect. ZA use potentially suppressed bone remodeling, which led to impaired healing at the extracted socket but full regeneration of the tibia defect. However, etidronate showed less suppression of bone remodeling and resulted in increased bone formation at the extracted socket and full regeneration of the tibia defect.

CONCLUSIONS

These results suggest that skeletal site-dependent differences in the bone healing process underlie BP-related preferential occurrence of osteonecrosis of the jaw bone.

Medication Related Osteonecrosis of the Jaw: 2015 Position Statement of the Korean Society for Bone and Mineral Research and the Korean Association of Oral and Maxillofacial Surgeons

Bisphosphonates are the most widely prescribed drugs for the treatment of osteoporosis, and 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 occurrence of osteonecrosis of the jaw (ONJ) could be related with bisphosphonate 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 (ASBMR) and American Association of Oral and Maxillofacial Surgeons (AAOMS) 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 a consideration of the fact that ONJ also occurs for denosumab, a bone resorption inhibitor of the receptor activator of nuclear factor-kappa B ligand (RANKL) antibody family, and bevacizumab, an anti-angiogenesis inhibitor. In 2009, a statement on ONJ was also reported locally by a relevant organization, which has served as basis for clinical treatment in Korea. In addition to the new official stance of the AAOMS and ASBMR, with an increasing pool of ONJ clinical experience, a revised version of the 2009 local statement is needed. As such, the Korean Society for Bone and Mineral Research (KSBMR) and the Korean Association of Oral and Maxillofacial Surgeons (KAOMS) have collectively formed a committee for the preparation of an official statement on MRONJ, and have reviewed recent local and international data to propose guidelines customized for the local Korean situation.

Inhibition of phosphate transporters ameliorates the inflammatory and necrotic side effects of the nitrogen-containing bisphosphonate zoledronate in mice

Bisphosphonates (BPs) are pyrophosphate analogs. They are widely used against enhanced bone-resorption in various diseases. Nitrogen-containing BPs (N-BPs) exhibit strong anti-bone-resorptive effects but have inflammatory and necrotic side effects. The non-nitrogen-containing BPs (non-N-BPs) etidronate and clodronate lack such side effects, but their anti-bone-resorptive effects are weak. In mice, etidronate and clodronate reduce the inflammatory/necrotic effects of N-BPs, even those of zoledronate, the N-BP with the strongest anti-bone-resorptive effect yet reported and the highest risk of inflammation/necrosis. Here, to explore the mechanisms underlying this protection, we used a mouse model in which a single reagent or a mixture of two reagents was injected subcutaneously into ear-pinnas. These reagents included zoledronate, four non-N-BPs, pyrophosphate, and inhibitors of various organic-anion-transporters. Pyrophosphate and two of the four non-N-BPs (not etidronate or clodronate) had inflammatory/necrotic effects. These effects were reduced by etidronate and clodronate, but not by phosphonoformate, an inhibitor of two of the three known phosphate-transporter families. Phosphonoformate reduced the inflammatory/necrotic effects of zoledronate, but not those of pyrophosphate or of non-N-BPs. Conversely, pyrophosphate, at non-inflammatory/necrotic concentrations, reduced the inflammatory/necrotic effects of non-N-BPs, but not those of zoledronate. The efficacies of the protective effects against the inflammatory/necrotic effects of zoledronate were clodronate > etidronate > phosphonoformate. These findings suggest that (i) the N-BP zoledronate may enter soft-tissue cells via phosphonoformate-inhibitable phosphate-transporters, (ii) other phosphate-transporters may carry pyrophosphate and inflammatory/necrotic non-N-BPs into such cells, and (iii) etidronate and clodronate inhibit all these transporters, and they ameliorate the side effects of zoledronate by inhibiting phosphonoformate-inhibitable phosphate-transporters.

Pro-inflammatory and anti-angiogenic effects of bisphosphonates on human cultured retinal pigment epithelial cells

AIM

Bisphosphonates have been shown to induce ocular inflammatory diseases such as uveitis and scleritis, while being protective against angiogenic diseases like neovascular age-related macular degeneration (AMD). Therefore, we studied the effects of bisphosphonates on primary culture of human fetal retinal pigment epithelium (hRPE), a cell type known to secrete both inflammatory and angiogenic factors. Alendronate and etidronate were selected for this experiment as they are members of the two structurally different classes of bisphosphonates.

METHODS

Primary cultures of hRPE were serum-starved for 24 h and then treated for 24 h with alendronate (0.0001, 0.1, 100 µM) or etidronate (0.01, 1 µM). Cell viability was measured using the MTT assay. Investigation of secreted cytokines induced by bisphosphonates was performed using a human cytokine 29-Plex Panel (Bio-Plex) array and the results were analysed with an analysis of variance (ANOVA).

RESULTS

Etidronate, at the lower concentration, significantly increased the expression of interleukin (IL)-6 (p=0.03) and IL-8 (p=0.04). At the higher concentration, etidronate significantly decreased the expression of granulocyte macrophage colony-stimulating factor (p=0.02) and basic fibroblast growth factor (bFGF) (p=0.02). Alendronate, at the highest concentration, significantly increased the expression of IL-8 (p=0.02) and decreased the expression of eotaxin (p=0.02). Alendronate also significantly decreased the expression of bFGF at all concentrations (p<0.05) and demonstrated a trend towards decreasing vascular endothelial growth factor expression at low concentration.

CONCLUSIONS

Alendronate and etidronate display dose dependent effects in hRPE cells. Alendronate and etidronate administration resulted in concentration dependent elevations in inflammatory cytokines. Furthermore, alendronate and etidronate administration resulted in reduced expression of a number of angiogenic factors. These findings may explain the increased incidence of ocular inflammation as well as the therapeutic effect on neovascular AMD which have been described with bisphosphonates.

Analgesic effects of the non-nitrogen-containing bisphosphonates etidronate and clodronate, independent of anti-resorptive effects on bone

Nitrogen-containing bisphosphonates (NBPs) have greater anti-bone-resorptive effects than non-nitrogen-containing bisphosphonates (non-NBPs). Hence, NBPs are the current first-choice drug for osteoporosis. However, NBPs carry a risk of osteonecrosis of jaws. Some animal and human studies suggest that non-NBPs may have anti-bone-resorptive effect-independent analgesic effects, but there has been no detailed comparison between NBPs and non-NBPs. Here, we compared the analgesic effects of several non-NBPs and NBPs, using (a) writhing responses induced in mice by intraperitoneal injection of 1% acetic acid, (b) acetic acid-induced neuronal expression of c-Fos, (c) acetic acid-induced elevation of blood corticosterone, and (d) hindpaw-licking/biting responses induced by intraplantar injection of capsaicin. Among the NBPs and non-NBPs tested, only etidronate and clodronate displayed clear analgesic effects, with various routes of administration (including the oral one) being effective. However, they were ineffective when intraperitoneally injected simultaneously with acetic acid. Intracerebroventricular administration of etidronate or clodronate, but not of minodronate (an NBP), was also effective. The effective doses of etidronate and clodronate were much lower in writhing-high-responder strains of mice. Etidronate and clodronate reduced acetic acid-induced c-Fos expression in the brain and spinal cord, and also the acetic acid-induced corticosterone increase in the blood. Etidronate and clodronate each displayed an analgesic effect in the capsaicin test. Etidronate and clodronate displayed their analgesic effects at doses lower than those inducing anti-bone-resorptive effects. These results suggest that etidronate and clodronate exert potent, anti-bone-resorptive effect-independent analgesic effects, possibly via an interaction with neurons, and that they warrant reappraisal as safe drugs for osteoporosis.

Bisphosphonate related osteonecrosis of the jaw--manifestation in a microvascular iliac bone flap

Bisphosphonate related osteonecrosis of the jaw (BRONJ) is a side effect that may emerge due to a long-term bisphosphonate therapy. Although the timely diagnosis and initiation of treatment are associated with good outcome results, extended cases require whole parts of the jaw to be resected. A possible treatment option is the bony reconstruction of the jaw using microvascular bone flaps. We report, for the first time, the development of a bisphosphonate related osteonecrosis in a microvascular iliac bone graft, a reconstruction that was performed following a partial mandibulectomy due to BRONJ stage III. The observation of BRONJ manifestation in an osseous microvascular transplant is a novel finding that sheds new light on current pathogenesis theories that surround this entity. Furthermore, it is hypothesized that BRONJ is able to progress to adjacent bone. In addition, bone reconstruction in patients suffering from BRONJ may be seen more critically.

Survival of dental implants in post-menopausal bisphosphonate users

PURPOSE

To determine whether post-menopausal women with a history of bisphosphonate use are at greater risk for implant failure or osteonecrosis of the jaw (ONJ) than an age- and gender-matched population with no history of bisphosphonate use.

METHODS

A retrospective chart review and phone interview was conducted of patients seen at the Mayo Clinic who had implants placed after November 2006. Bisphosphonate users were identified by medical chart review. Dental implant survival and ONJ incidence were determined in a total of 82 post-menopausal non-bisphosphonate users and 55 post-menopausal bisphosphonate users using a phone interview. Implant failures were recorded and survival percentages were calculated for comparison.

RESULTS

ONJ was not observed consequent to implant placement in any of the bisphosphonate users or non-users. In non-users, 163 out of 166 implants were surviving for a cumulative survival rate of 98.19%. In bisphosphonate users, 120 out of 121 implants were surviving for a cumulative survival rate of 99.17%.

CONCLUSION

Dental implants placed in post-menopausal women have the same survival potential regardless of whether patients have a history of bisphosphonate use. Bisphosphonate users who undergo dental implant surgery are at low risk for osteonecrosis of the jaw and a bisphosphonate "drug holiday" is not indicated in these patients.