Novel therapy to reverse the cellular effects of bisphosphonates on primary human oral fibroblasts

Combinatorial effects of hydroxyapatite and Tualang honey on medication-related osteonecrosis of the jaw (MRONJ): An in vitro study

BACKGROUND

Medication-related osteonecrosis of the jaw (MRONJ) is a severe complication associated with prolonged bisphosphonate therapy. Increasing evidence shows that mucosal damage plays an important role in the pathogenesis of MRONJ. This study investigates the combinatorial effects of hydroxyapatite with Tualang honey on cell viability and wound healing in MRONJ.

MATERIALS AND METHODS

The incorporation of Tualang honey into hydroxyapatite was assessed using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and field emission scanning electron-energy dispersive X-ray analysis microscopy (FESEM-EDX). The effect of hydroxyapatite combined with Tualang honey on cell viability was determined by WST-1 assay and wound healing was assessed by scratch assay.

RESULTS

The incorporation of Tualang honey into hydroxyapatite altered the functional groups, structure, size, morphology, and components of the crystal as evidenced by FTIR, XRD and FESEM-EDX analysis. High concentrations of pamidronic acid inhibit oral fibroblast viability and wound healing. Low and high concentrations of hydroxyapatite demonstrate non-toxicity towards fibroblast cells. Furthermore, hydroxyapatite reversed the action of pamidronic acid on the cells; it increased fibroblast viability but did not close the wound. Tualang honey promotes fibroblast viability and wound closure. However, the addition of Tualang honey is unable to overcome the inhibitory effects of pamidronic acid on fibroblasts. The addition of Tualang honey and hydroxyapatite improved the cell viability and accelerated wound closure of fibroblast exposed to pamidronic acid.

CONCLUSION

These findings demonstrated that the combination treatment protects oral fibroblasts by preventing bisphosphonate toxicity.

In Vitro Cytotoxicity of Antiresorptive and Antiangiogenic Compounds on Oral Tissues Contributing to MRONJ: Systematic Review

BACKGROUND

Invasive dental treatment in patients exposed to antiresorptive and antiangiogenic drugs can cause medication-related osteonecrosis of the jaw (MRONJ). Currently, the exact pathogenesis of this disease is unclear.

METHODS

In March 2022, Medline (Ovid), Embase (Ovid), Scopus, and Web of Science were screened to identify eligible in vitro studies investigating the effects of antiresorptive and antiangiogenic compounds on orally derived cells.

RESULTS

Fifty-nine articles met the inclusion criteria. Bisphosphonates were used in 57 studies, denosumab in two, and sunitinib and bevacizumab in one. Zoledronate was the most commonly used nitrogen-containing bisphosphonate. The only non-nitrogen-containing bisphosphonate studied was clodronate. The most frequently tested tissues were gingival fibroblasts, oral keratinocytes, and alveolar osteoblasts. These drugs caused a decrease in cell proliferation, viability, and migration.

CONCLUSIONS

Antiresorptive and antiangiogenic drugs displayed cytotoxic effects in a dose and time-dependent manner. Additional research is required to further elucidate the pathways of MRONJ.

MicroRNA in medication related osteonecrosis of the jaw: a review

Medication related osteonecrosis of the jaw (MRONJ) is a condition caused by inhibition of the osteoclast activity by the anti-resorptive and anti-angiogenic drugs. Clinically, there is an exposure of the necrotic bone or a fistula which fails to heal for more than 8 weeks. The adjacent soft tissue is inflamed and pus may be present as a result of the secondary infection. To date, there is no consistent biomarker that could aid in the diagnosis of the disease. The aim of this review was to explore the literature on the microRNAs (miRNAs) related to medication related osteonecrosis of the jaw, and to describe the role of each miRNA as a biomarker for diagnostic purpose and others. Its role in therapeutics was also searched. It was shown that miR-21, miR-23a, and miR-145 were significantly different in a study involving multiple myeloma patients as well as in a human-animal study while miR-23a-3p and miR-23b-3p were 12- to 14-fold upregulated compared to the control group in an animal study. The role of the microRNAs in these studies were for diagnostics, predictor of progress of MRONJ and pathogenesis. Apart from its potential diagnostics role, microRNAs have been shown to be bone resorption regulator through miR-21, miR-23a and miR-145 and this could be utilized therapeutically.

Bisphosphonate affects the behavioral responses to HCl by disrupting farnesyl diphosphate synthase in mouse taste bud and tongue epithelial cells

Little is known about the molecular mechanisms underlying drug-induced taste disorders, which can cause malnutrition and reduce quality of life. One of taste disorders is known adverse effects of bisphosphonates, which are administered as anti-osteoporotic drugs. Therefore, the present study evaluated the effects of risedronate (a bisphosphonate) on taste bud cells. Expression analyses revealed that farnesyl diphosphate synthase (FDPS, a key enzyme in the mevalonate pathway) was present in a subset of mouse taste bud and tongue epithelial cells, especially type III sour-sensitive taste cells. Other mevalonate pathway-associated molecules were also detected in mouse taste buds. Behavioral analyses revealed that mice administered risedronate exhibited a significantly enhanced aversion to HCl but not for other basic taste solutions, whereas the taste nerve responses were not affected by risedronate. Additionally, the taste buds of mice administered risedronate exhibited significantly lower mRNA expression of desmoglein-2, an integral component of desmosomes. Taken together, these findings suggest that risedronate may interact directly with FDPS to inhibit the mevalonate pathway in taste bud and tongue epithelial cells, thereby affecting the expression of desmoglein-2 related with epithelial barrier function, which may lead to alterations in behavioral responses to HCl via somatosensory nerves.

In vitro Effect of Geranylgeraniol (GGOH) on Bisphosphonate-Induced Cytotoxicity of Oral Mucosa Cells

Medication-related osteonecrosis of the jaw (MRONJ) is an often-severe complication found in patients receiving bisphosphonates in the management of Paget's, osteoporosis and metastatic bone cancer. Mucosal breakdown with bone exposure is a primary clinical presentation of MRONJ linked to the inhibitory effect of nitrogen-containing bisphosphonates (N-BP) on the mevalonate pathway. Geranylgeraniol (GGOH) has demonstrated a rescue effect on N-BP-treated osteoclasts but the biological effects on oral soft tissues and cells remain unclear. This study aimed to determine whether GGOH could prevent bisphosphonate induced toxicity to oral mucosa cells in vitro. Primary oral fibroblasts and keratinocytes were exposed to different GGOH concentrations or GGOH in combination with two nitrogen-containing bisphosphonates, zoledronic acid (ZA) or pamidronic acid (PA), for 72 h. The metabolic activity of each cell type was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. GGOH without bisphosphonates significantly reduced the metabolic activity of oral mucosa cells. Fibroblasts treated with GGOH and ZA in combination showed a slight increase in metabolic status compared to fibroblasts treated with ZA alone, however this positive effect was not observed in keratinocytes. In the presence of PA, GGOH was unable to increase the metabolic activity of either cell type. These findings demonstrate that GGOH is toxic to oral mucosa cells and that GGOH was not able to prevent bisphosphonate induced toxicity. These data show that GGOH does not have therapeutic potential for bisphosphonate-induced soft tissue toxicity in MRONJ and the use of GGOH as an MRONJ treatment should be strongly reconsidered.

The Role of Geranylgeraniol in Managing Bisphosphonate-Related Osteonecrosis of the Jaw

Medication-related osteonecrosis of the jaw (ONJ) is a rare but significant adverse side effect of antiresorptive drugs. Bisphosphonate-related ONJ (BRONJ) is the most prevalent condition due to the extensive use of the drug in cancer and osteoporosis treatment. Nitrogen-containing bisphosphonates suppress osteoclastic resorption by inhibiting farnesyl pyrophosphate synthase in the mevalonate pathway, leading to deficiency of the substrate for GTPase prenylation. The bone remodelling process is uncoupled, subsequently impairing bone healing and causing ONJ. Targeted administration of geranylgeraniol (GGOH) represents a promising approach to mitigate BRONJ because GGOH is a substrate for GTPase prenylation. In the current review, the in vitro effects of GGOH on osteoclasts, osteoblasts and other related cells of the jaw are summarised. We also present and appraise the current in vivo evidence of GGOH in managing BRONJ in animal models. Lastly, several considerations of using GGOH in the clinical management of BRONJ are highlighted. As a conclusion, GGOH is a promising topical agent to manage BRONJ, pending more research on an effective delivery system and validation from a clinical trial.

A Review Into the Effects of Pamidronic Acid and Zoledronic Acid on the Oral Mucosa in Medication-Related Osteonecrosis of the Jaw

Medication-related osteonecrosis of the jaw (MRONJ) is a growing problem without an effective treatment, presenting as necrotic bone sections exposed via lesions in the overlying soft tissue. There is currently a lack of clarity on how the factors involved in MRONJ development and progression contribute to disease prognosis and outcomes. Bisphosphonates (BPs), the most common cause of MRONJ, affect bone remodeling, angiogenesis, infection, inflammation and soft tissue toxicity, all of which contribute to MRONJ development. This article reviews the cellular mechanisms through which BPs contribute to MRONJ pathology, with a focus on the effects on cells of the oral mucosa. BPs have been shown to reduce cell viability, reduce proliferation, and increase apoptosis in oral keratinocytes and fibroblasts. BPs have also been demonstrated to reduce epithelial thickness and prevent epithelial formation in three-dimensional tissue engineered models of the oral mucosa. This combination of factors demonstrates how BPs lead to the reduced wound healing seen in MRONJ and begins to uncover the mechanisms through which these effects occur. The evidence presented here supports identification of targets which can be used to develop novel treatment strategies to promote soft tissue wound healing and restore mucosal coverage of exposed bone in MRONJ.

Characterization of Mesenchymal Stem Cells Derived from Bisphosphonate-Related Osteonecrosis of the Jaw Patients' Gingiva

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a clinical condition that specifically occurs in the oral cavity, characterized by retarded wound healing in oral mucosa accelerating the exposure of bone. Moreover, the pathological mechanism remains poorly understood. Gingival mesenchymal stem cells (GMSCs) play a critical role in gingival healing and soft tissue regeneration. Although previous studies have showed that bisphosphonates (BPs) are highly toxic to healthy GMSC, there is overall lack of direct evidence demonstrating the characterization of GMSCs derived from BRONJ patients. In present study, we isolated GMSCs for the first time from the central area of BRONJ patients' gingiva (center-BRONJ GMSCs) and the peripheral area (peri-BRONJ GMSCs), and found that they exhibited decreased proliferation, adhesion, migration capacities and underwent early apoptosis in vitro compared control GMSCs. Notably, the central and peripheral BRONJ GMSCs transplantation in a mice excisional skin model also displayed lower cell survival rate and poor healing effects than that of controls. Mechanistically, TGF-β1 signaling pathway was suppressed not only in BRONJ patients' gingival lesions but also in BRONJ GMSCs transplantation animal model. The results above suggested that under the microenvironment of BRONJ patients, the dysfunction of GMSCs and the suppressed TGF-β1 signaling pathway may be the vital factors in impaired gingival healing, thus contributing to persistent exposure of underlying bone and development of BRONJ. This study provides new insights into the prevention for BRONJ by improving the functions of GMSCs and upregulating TGF-β1 in accelerating gingival wound healing. Schematic illustration of the dysfunction of BRONJ GMSCs in vitro and BRONJ GMSCs transplantation in a mice skin model delaying cutaneous wound healing mainly via suppressing TGF-β1 signaling pathway.

Geranyl-geraniol addition affects potency of bisphosphonates-a comparison in vitro promising a therapeutic approach for bisphosphonate-associated osteonecrosis of the jaw and oral wound healing

Purpose

Analysis of the influence of geranyl-geraniol (GG) addition on four bisphosphonate derivatives regarding their influence on cell viability and migration ability of bone metabolism and endothelial cells in vitro.

Methods

Clodronate, pamidronate, ibandronate, and zoledronate were observed with and without GG addition, for their effect on human osteoblasts (HOB), normal human dermal fibroblasts (NHDF), human endothelial progenitor cells (EPC), and endothelial cells of the human umbilical cord (HUVEC) using migration-, MTT-, and colony-forming cell assays.

Results

Data pointed to a depressing effect of all bisphosphonates on the migration ability of NHDF, EPC, and HOB. MTT assay demonstrated a decreased cell viability of HUVEC of all bisphosphonates in a 50 μM concentration and of NHDF when treated with 50 μM of clodronate, ibandronate, or zoledronate. Tested drugs showed a depressing effect on colony-forming potential of EPC even in a 5 μM concentration. GG addition demonstrated an attenuate impact on bisphosphonate effect on all primary cell cultures, respectively.

Conclusion

In vitro comparison showed that the addition of GG weakens the effect of all bisphosphonates examined. It supports investigations that suggest GG to be able to prevent bisphosphonate-associated osteonecrosis of the jaw (BP-ONJ) in vivo. Future clinical trials may discover the local therapeutic use of GG for the prevention of BP-ONJ.

Standardized Arrabidaea chica Extract Shows Cytoprotective Effects in Zoledronic Acid-Treated Fibroblasts and Osteoblasts

INTRODUCTION

Osteonecrosis of the jaw is a condition associated with intraoral ulceration and bone necrosis induced by antiresorptive medications, such as zoledronic acid, a bisphosphonate. Previous data on Arrabidaea chica (H&B.) Verlot wound healing activity prompted the study reported herein on A. chica standardized hydro alcoholic extract in vitro cytoprotective activity data on epithelial and osteoblastic cells exposed to zoledronic acid (ZA).

METHODS

Primary human gingival fibroblasts and murine pre-osteoblasts were treated with ZA 10 µM together with 5 or 10 µg.mL-1 A. chica extract for 24h and 48 h. At both times, cells were submitted to viability assay and caspase 3/7 activation evaluation. Statistical analysis used one-way ANOVA and p=0.05.

RESULTS

In cell viability assay, a drastic damage effect of ZA appeared after 48 h in both epithelial (55.8%) and pre-osteoblastic cells (39.7%). When treated with ZA in combination with A. chica extract, cells showed higher viability values: 74.1%-82.3% for fibroblasts and 66% for pre-osteoblasts. Furthermore, the combined treatment presented lower caspase 3/7 activation in fibroblasts and pre-osteoblasts.

CONCLUSION

At low concentrations, A. chica extract showed promising cytoprotective effects against ZA-induced damage actions; however, further in vitro and in vivo studies are required to establish the mechanism of action.

Synthetic Hydroxyapatite Inhibits Bisphosphonate Toxicity to the Oral Mucosa In Vitro

Medication-related osteonecrosis of the jaw (MRONJ) is a side effect of bisphosphonate therapy, characterised by exposed necrotic bone. The soft tissues of the oral mucosa no longer provide a protective barrier and MRONJ patients experience pain, infections and difficulties eating. We hypothesised that hydroxyapatite (Ca₅(PO₄)₃(OH)) could reduce bisphosphonate concentrations and protect the oral mucosa by exploiting bisphosphonate's calcium binding affinity. The effect of zoledronic acid (ZA) and pamidronic acid (PA) on the metabolism of oral fibroblasts, oral keratinocytes and three-dimensional oral mucosa models was investigated and then repeated in the presence of hydroxyapatite granules. Without hydroxyapatite, ZA and PA significantly reduced the metabolic activity of oral cells in a dose-dependent manner. Both drugs reduced epithelial thickness and 30 µM ZA resulted in loss of the epithelium. Hydroxyapatite granules had a protective effect on oral cells, with metabolic activity retained. Oral mucosa models retained their multi-layered epithelium when treated with ZA in the presence of hydroxyapatite granules and metabolic activity was comparable to controls. These results demonstrate hydroxyapatite granules protected oral soft tissues from damage caused by bisphosphonate exposure. Porous hydroxyapatite granules are currently used for socket preservation and this data suggests their potential to prevent MRONJ in at-risk patients.

Protective effects of resveratrol against osteonecrosis at the extraction site in bisphosphonate-treated rats

Resveratrol (RSV) is a phytoestrogen with a wide range of therapeutic effects, including antioxidant and anti-inflammatory effects. This study was performed to evaluate the protective role of RSV against osteonecrosis after tooth extraction in rats treated with bisphosphonates. Thirty-nine male Wistar rats, weighing 300-350 g, were divided into three groups (n = 13) according to the planned drug regimen: alendronate + dexamethasone (AL/DEX), alendronate + dexamethasone + RSV (AL/DEX/RSV), and no drugs (control group). The first and second molars of each rat were extracted and the extraction sites were analysed histologically 14 days later. The data collected were subjected to statistical analysis by means of Kruskal-Wallis, Mann-Whitney, χ², and Fisher's exact tests using IBM SPSS software at a significance level of 0.05. The incidence of osteonecrosis was significantly lower in the AL/DEX/RSV group (P = 0.001) and control group (P = 0.041) than in the AL/DEX group, while the amount of new bone formation did not differ significantly between the AL/DEX/RSV and AL/DEX groups (P > 0.05). RSV showed a protective effect by significantly reducing osteonecrosis, which could be due to its antioxidant effects.

Gingival fibroblasts and medication-related osteonecrosis of the jaw: Results by real-time and wound healing in vitro assays

OBJECTIVE

This study investigated the effects of bisphosphonates and denosumab on human gingival fibroblasts (HGFs) that could influence inflammation, wound healing, and angiogenesis in medication-related osteonecrosis of the jaw (MRONJ).

METHODS

A real-time in vitro assay was performed on HGFs with and without the addition of bacterial lipopolysaccharide and a mononuclear cell co-culture to observe the effects of zoledronate, ibandronate, alendronate, clodronate, denosumab, and combinations of zoledronate and denosumab at varied concentrations. A wound healing assay was performed, and gene and protein expression was analyzed for inflammatory, angiogenic, and osteoclastogenic cytokines and mediators including interleukin (IL)-1β, IL-6, tumor necrosis factor alpha (TNFα), IL-8, vascular endothelial growth factor (VEGF), RANKL, and osteoprotegerin.

RESULTS

Higher concentrations of antiresorptives resulted in impaired wound healing and HGF death, which also occurred without mechanical damage. These effects were increased with bacterial lipopolysaccharide and mononuclear cells. Increased levels of IL-1β, TNFα, IL-8, VEGF, osteoprotegerin, and decreased levels of IL-6 were observed.

CONCLUSIONS

Antiresorptive exposure was associated with HGF death and delayed wound healing, which could be attributed to an elevated inflammatory response and immune dysfunction contributing to MRONJ development. There was no evidence of anti-angiogenic effects. Our experiments present the first results of denosumab with HGFs.

Geranylgeraniol (GGOH) as a Mevalonate Pathway Activator in the Rescue of Bone Cells Treated with Zoledronic Acid: An In Vitro Study

Bisphosphonates (BPs) are the keystone to treat bone disorders. Despite the great benefits of BPs, medication-related osteonecrosis of the jaw (MRONJ) arouse as a potential side effect. Nitrogen-containing BPs (N-BPs) as zoledronate (ZA) act by the inhibition of specific enzymes of the mevalonate pathway resulting in altering protein prenylation which is required for the posttranslational maturation of the small GTP-binding proteins. Geranylgeraniol (GGOH) is an intermediate product in the mevalonate pathway having positive effects on different cell types treated with BPs by salvaging protein prenylation improving cell viability and proliferation in tissue regeneration, thus overcoming N-BP-induced apoptosis. Here, the effect of different concentrations of zoledronate (ZA) on the bone cells has been investigated by cell viability assay, live/dead staining, and western blot to understand if GGOH was able to rescue bone cells and levels of statistical significance were indicated at ^∗P < 0.05, ^∗∗P < 0.01, ^∗∗∗P < 0.001, and ^∗∗∗∗P < 0.0001. Although the high concentration of ZA had significantly decreased the cell viability in the bone cells, GGOH reversed the action of ZA on the cells while at very high concentration; it caused severe reduction in the cell viability. Rap1A, a member of the GTPases family, was expressed in the negative controls but was absent in cells treated with high concentrations of ZA. The addition of GGOH had increased the expression of Rap1A up to a certain limit. The experiments proved that ZA acts directly on the mevalonate pathway and protein prenylation and that GGOH could be applied as a future local therapy to MRONJ.

In vivo effects of geranylgeraniol on the development of bisphosphonate-related osteonecrosis of the jaws

BACKGROUND

Bisphosphonate-related osteonecrosis of the jaws (BRONJ) is a complication of the bisphosphonate (BP) treatment and its pathopysiology is still not fully understood. The existing preventive and treatment options require updates and more attention. Geranylgeraniol (GGOH) so far demonstrated an increased activity and viability of the cells previously treated with zoledronic acid (ZA). The aim of this study was to evaluate the in vivo effects of GGOH on the development of BRONJ.

MATERIALS AND METHODS

A total of 30 male Wistar rats were included in the study, divided into three groups: two experimental groups (EG1 and EG2) and a control group (CG). Rats from EG1 and EG2 were treated with 0,06 mg/kg ZA ip weekly in a duration of five weeks, while CG received saline ip. On the third week all animals underwent extraction of the lower right first molars. The rats from EG2 received a local solution of GGOH in concentration of 5 mM in the socket every day after the tooth extraction. The analyses included clinical evaluation on the wound healing and pathohistological evaluation for presence and level of osteonecrosis.

RESULTS

EG2 showed significantly improved wound healing and tissue proliferation, when compared to EG1. EG2 significantly differed from EG1 and CG (p<0,05) for the presence of microscopical osteonecrosis (80% vs 22,2% vs 0%). Regarding to the number of empty lacunes without osteocytes and the level of necrosis, all groups demonstrated significant differences.

CONCLUSION

Geranylgeraniol in a form of local solution may be a promising option for prevention and treatment of BRONJ.

The effects of ozone application on genotoxic damage and wound healing in bisphosphonate-applied human gingival fibroblast cells

OBJECTIVES

Medication-related osteonecrosis of the jaws (MRONJ) is an extremely therapy-resistant disease involving the jaws especially following bisphosphonate treatment. Bisphosphonates accumulate in bone in concentrations sufficient to be directly toxic to the oral epithelium. Current therapeutic options are inadequate for the prevention and treatment of MRONJ. The aim of this study was to investigate effects of ozone gas plasma therapy on wound healing in bisphosphonate-applied human fibroblasts.

MATERIAL AND METHODS

Human primary gingival fibroblasts were cultured. Cytotoxic concentrations (IC50) of bisphosphonates (pamidronate (PAM), alendronate (ALN), and zoledronate (ZOL)) were determined by MTT test. A 60 μg/μl for 30 s of ozone gas plasma application was performed to all experimental culture flasks after drug treatment at 24-h intervals as 3 s/cm². Genotoxic damages were evaluated by comet assay and wound healing was determined by in vitro scratch assay.

RESULTS

PAM, ALN, and ZOL applications caused genotoxic damage on primary human gingival fibroblast DNA. Ozone gas plasma therapy significantly decreased the genotoxic damage (p < 0.05), and this application provided 25, 29, and 27% less genotoxic damage in order of ALN, PAM, and ZOL groups. Ozone gas plasma therapy significantly increased wound healing rates both in postsurgical 24th and 48th hours for all doses of experimental drug groups (p < 0.05).

CONCLUSION

The ozone gas plasma application decreased genotoxic damage effect of bisphosphonate usage while improved the wound closure rate on human gingival fibroblasts.

CLINICAL RELEVANCE

Ozone gas plasma therapy may be helpful in prevention of gingival healing delay in MRONJ pathogenesis especially when applied simultaneously with surgical intervention.

Effects of zoledronic acid and geranylgeraniol on the cellular behaviour and gene expression of primary human alveolar osteoblasts

INTRODUCTION

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a serious complication of bisphosphonate therapy. The mechanism underlying BRONJ pathogenesis is poorly understood.

OBJECTIVES

To determine the effects of zoledronic acid (ZA) and geranylgeraniol (GGOH) on the mevalonate pathway (MVP) in osteoblasts generated from the human mandibular alveolar bone in terms of cell viability/proliferation, migration, apoptosis and gene expression.

MATERIALS AND METHODS

Primary human osteoblasts (HOBs) isolated from the mandibular alveolar bone were phenotyped. HOBs were cultured with or without ZA and GGOH for up to 72 h. Cellular behaviour was examined using a CellTiter-Blue® viability assay, an Ibidi culture-insert migration assay, an Apo-ONE® Homogeneous Caspase-3/7 apoptosis assay and transmission electron microscopy (TEM). Quantitative real-time reverse transcriptase polymerase chain reaction (qRT²-PCR) was used to determine the simultaneous expression of 168 osteogenic and angiogenic genes modulated in the presence of ZA and GGOH.

RESULTS

ZA decreased cell viability and migration and induced apoptosis in HOBs. TEM revealed signs of apoptosis in ZA-treated HOBs. However, the co-addition of GGOH ameliorated the effect of ZA and partially restored the cells to the control state. Twenty-eight genes in the osteogenic array and 27 genes in the angiogenic array were significantly regulated in the presence of ZA compared with those in the controls at one or more time points.

CONCLUSION

The cytotoxic effect of ZA on HOBs and its reversal by the addition of GGOH suggests that the effect of ZA on HOBs is mediated via the MVP.

CLINICAL RELEVANCE

The results suggest that GGOH could be used as a possible therapeutic/preventive strategy for BRONJ.

The bisphosphonate zoledronic acid regulates key angiogenesis-related genes in primary human gingival fibroblasts

BACKGROUND

Osteonecrosis of the jaws is recognised as a serious complication for patients receiving bisphosphonates. The anti-angiogenic effects of bisphosphonates have been implicated in the pathogenesis of bisphosphonate-related osteonecrosis of the jaw (BRONJ). The purpose of this study was to determine the effects of zoledronic acid on cultured human gingival fibroblasts in relation to the modulation of genes associated with angiogenic regulation.

METHODS

Primary cultures of fibroblasts were developed from gingival tissues excised during crown-lengthening surgery from three patients. Cells were cultured with and without 30μM zoledronic acid for 6, 12 and 24h and cellular proliferation and migration investigated using CellTiter-Blue and scratch wound assays, respectively. Gene expression was determined using semi-quantitative PCR array technology that allowed the analysis of 84 pathway-focused genes known to be important in the regulation of angiogenesis.

RESULTS

Zoledronic acid increased the proliferation of the gingival fibroblasts in a dose dependent manner with 12 and 24h of exposure. Scratch wounding of the human gingival fibroblasts and treatment with increasing doses and time exposure to zoledronic acid (ZA) inhibited their migration. Statistically significant increases in gene expression were found for RHOB, VEGFA, CD55 and BMP2 (p≤0.05) in response to 30μM zoledronic acid. CCL2 and IL6 genes were significantly downregulated (p≤0.05).

CONCLUSIONS

The regulation of the prenylated protein RHOB in this study was consistent with the known effects of zoledronic acid on the mevalonate pathway. The down regulation of CCL2 and IL6 and the upregulation of CD55 may be associated with suppression of inflammation. An increase in VEGFA and BMP2 gene expression suggests that fibroblasts respond to zoledronic acid by producing a proangiogenic environment.

Photodynamic Inactivation of Actinomyces naeslundii in Comparison With Chlorhexidine and Polyhexanide--A New Approach for Antiseptic Treatment of Medication-Related Osteonecrosis of the Jaw?

PURPOSE

Local antimicrobial therapy is a fundamental principle in the treatment of lesions of medication-related osteonecrosis of the jaw. Antimicrobial photodynamic therapy (aPDT) as a local application for the treatment of microbial infections has become more widely used in recent years. In the mouth, the bone surface is in constant contact with saliva and thus cannot be kept sterile, making the development of strategies for disinfection even more important. Different methods currently in use include local rinses with chlorhexidine (CHX), polyhexanide (PHX), or aPDT. This study compared the efficiency of these 3 methods.

MATERIALS AND METHODS

The in vitro activity of 3 different agents against slowly growing Actinomyces naeslundii isolated from a patient with osteonecrosis was evaluated. PHX 0.04% solution, CHX 0.12% solution, and methylene blue (MB) based dye with a laser light of 660-nm wavelength (aPDT) were compared.

RESULTS

The decrease in colony-forming units by each method was measured using an in vitro killing assay based on a water-exposed surface in a well plate. MB dye with laser (10 seconds) decreased the bacterial load by more than 4 orders of magnitude and was superior to PHX and CHX exposure for 60 seconds.

CONCLUSION

Laser exposure alone and MB dye exposure alone decreased bacterial loads slightly, but less efficiently than 60-second exposure to PHX or CHX. The most effective means of decreasing colony-forming units was achieved by a combination of laser light and dye, which also can be used clinically.

The influence of geranylgeraniol on human oral keratinocytes after bisphosphonate treatment: An in vitro study

This in vitro study analyzed the influence of geranylgeraniol (GGOH) on human oral keratinocytes (HOK) after exposure to bisphosphonates. HOK were incubated with four different bisphosphonates (clodronate, ibandronate, pamidronate, zoledronate) in two experimental set-ups: with and without GGOH. MTT and PrestoBlue assays were used to analyze HOK cell viability. HOK migration ability was examined with Boyden and Scratch assays, and Tunel and ToxiLight assays were used to detect the HOK apoptosis rate. No significant differences between the experimental set-ups, with and without GGOH, could be found for clodronate (p each >0.3). For the nitrogen-containing bisphosphonates, negative effects could be shown in the experimental set-ups without GGOH in all assays. In the GGOH experimental set-ups, the levels of HOK cell viability were significantly increased (MTT: p each ≤0.001; PrestoBlue: p each ≤0.012). The HOK migration ability was also greater (Boyden: p each <0.001; Scratch: p each ≤0.015). Regarding the apoptosis rate, reduced numbers of apoptotic HOK in the Tunel assay (p each <0.001) and decreased adenylate kinase release in the ToxiLight assay (p each ≤0.002) were observed. GGOH reversed the negative effects of bisphosphonates on HOK. These findings provide evidence that GGOH could be a promising treatment option for BP-ONJ.

Dysfunctional high-density lipoproteins in children with chronic kidney disease

OBJECTIVES

Our aim was to determine if chronic kidney disease (CKD) occurring in childhood impairs the normally vasoprotective functions of high-density lipoproteins (HDLs).

MATERIALS AND METHODS

HDLs were isolated from children with end-stage renal disease on dialysis (ESRD), children with moderate CKD and controls with normal kidney function. Macrophage response to HDLs was studied as expression of inflammatory markers (MCP-1, TNF-α, IL-1β) and chemotaxis. Human umbilical vein endothelial cells were used for expression of adhesion molecules (ICAM-1, VCAM-1, E-selectin) and adhesion. Cellular proliferation, apoptosis, and necrosis of endothelial cells were measured by MTS/PMS reagent-based assay, flow cytometry, and ELISA. Cholesterol efflux was assessed by gas chromatographic measurements of cholesterol in macrophages exposed to HDLs.

RESULTS

Compared with HDL(Control), HDL(CKD) and HDL(ESRD) heightened the cytokine response and disrupted macrophage chemotaxis. HDL(Control) reduced endothelial expression of ICAM-1, VCAM-1, E-selectin, whereas HDL(CKD) and HDL(ESRD) were less effective and showed reduced capacity to protect endothelial cells against monocyte adhesion. Compared with a dramatically enhanced endothelial proliferation following injurious stimulus by HDL(Control), neither HDL(CKD) nor HDL(ESRD) caused proliferative effects. HDLs of all three groups were equally protective against apoptosis assessed by flow cytometry and cleaved caspase-3 activity. Compared to HDL(Control), HDL(CKD) and HDL(ESRD) trended toward reduced capacity as cholesterol acceptors.

CONCLUSION

CKD in children impairs HDL function. Even in the absence of long-standing and concomitant risk factors, CKD alters specific HDL functions linked to control of inflammation and endothelial responses.

Effects of alendronate and pamidronate on apoptosis and cell proliferation in cultured primary human gingival fibroblasts

Data arising from the recent literature directed the researchers to study on the degree and extent of bisphosphonate toxicity on oral mucosa in further detail. The aim of this study is to determine the half maximal inhibitory concentration of pamidronate (PAM) and alendronate (ALN) on human gingival fibroblasts in vitro using 3-[4.5-thiazol-2-yl]-2.5-diphenyltetrazolium bromide (MTT) assay and to evaluate the effects of both agents on the proliferation and apoptotic indices. Cells used in the study were generated from human gingival specimens and divided into alendronate (n = 240), PAM (n = 240), and control groups (n = 60). Based on the MTT assay results, 10(-4), 10(-5), 10(-6), and 10(-7) M concentrations of both drugs were administered and the effects were evaluated for 6, 12, 24, 48, or 72 h periods. An indirect immunofluorescence technique was used to evaluate apoptotic (anti-caspase 3) and proliferation (anti-Ki67) indices. Toxicity of both PAM and ALN was found to be the most potent at 10(-4)-10(-5) M range. The apoptotic index of PAM group was found to be significantly higher than ALN group for all concentrations especially at 24 h incubation time (p < 0.05). The decrease in the proliferation index was found similar in first 48 h for both drugs; however, after 72 h of incubation decrease in proliferation index in PAM group was found to be significantly higher (p < 0.05). Micromolar concentrations of not only PAM but also ALN rapidly affect cells generated from human oral gingival tissue by inducing apoptosis together with inhibition of proliferation. Cytotoxic effects of both ALN and PAM on primary human gingival fibroblasts, which cause significant changes in apoptotic and proliferative indices as shown in this in vitro study, suggests that the defective epithelialization of oral mucosa is possibly a major factor on the onset of bisphosphonate-related osteonecrosis of the jaw cases.

Bisphosphonate-related osteonecrosis of the jaw: specificities

Bisphosphonate-related osteonecrosis of the jaws (BRONJ) is a severe complication that has recently emerged in patients treated with intravenous bisphosphonates for malignant diseases. This complication usually presents after a minor local trauma during a dental treatment. Several etiopathogenic mechanisms of this pathological condition have been proposed, but no model can explain all morphological changes observed at the macroscopic and microscopic level. BRONJ is likely to be related to direct toxicity in the bone and soft tissue cells, due to nitrogen-containing bisphosphonates. This review elucidates the clinical indications and mechanism of action of bisphosphonates, reports some clinical diagnostic criteria for BRONJ, describe the histopathological criteria for BRONJ diagnosis, the potential triggering pathways and the available treatment strategies.

Bisphosphonate therapy and osteonecrosis of the jaw complicated with a temporal abscess in an elderly woman with rheumatoid arthritis: a case report

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is an adverse drug reaction described as the progressive destruction and death of bone tissue of the mandible or maxilla, in the course of bisphosphonate therapy. Orally administered bisphosphonates, widely used for the treatment of osteoporosis, are rarely associated with BRONJ. Instead, the risk greatly increases whether the patient is concomitantly taking steroid and/or immunosuppressant agents. The aims of this paper are to briefly discuss the evidence of the associations between bisphosphonate therapy and BRONJ, and the effects of co-occurring factors such as the presence of rheumatoid arthritis, dental surgery, and concomitant corticosteroid therapy. In particular, we present the case of an elderly woman with BRONJ suffering from rheumatoid arthritis, with a recent dental extraction and with a very unusual complication: a temporal abscess, who was successfully treated.

Atraumatic tooth extraction in patients taking bisphosphonates: a review of literature and experience with three cases

PURPOSE

Regev et al. first re-introduced the method of atraumatic tooth extraction with orthodontic elastics in 2008. Since then, the method has been mentioned regularly in literature. Nevertheless, the need for additional more detailed information remains.

METHODS

We present a review of literature and a retrospective analysis of our three patients receiving bisphosphonate medication. Two of our patients suffered from bisphosphonate-related osteonecrosis of the jaw (BRONJ). All three patients underwent atraumatic tooth extraction, which we describe in detail.

RESULTS

Regev et al. reported satisfactory results using the novel method. We removed six teeth in two patients with continued chemotherapy or bisphosphonate therapy in a time span of 26.2 ± 16.4 weeks successfully. None of the patients developed exposed bone in the follow-up (7.4 ± 0.2 months). In one case, the technique had to be discontinued due to increasing tooth soreness.

CONCLUSIONS

Atraumatic tooth extraction seems to be a safe method to prevent bone exposure, even in cases with BRONJ. The time required of our patients for exfoliation exceeded the time mentioned in literature considerably. This proved to be a major limitation. Our cases showed that patients with good compliance, no sore teeth, or painful BRONJ lesions, benefited from atraumatic tooth extraction. One of the method's major advantages might be the possibility to continue chemotherapy and bisphosphonate therapy throughout the treatment.

Zoledronic acid and geranylgeraniol regulate cellular behaviour and angiogenic gene expression in human gingival fibroblasts

The mevalonate pathway (MVP) and the anti-angiogenic effect of bisphosphonates have been shown to play a role in the pathogenesis of bisphosphonate-related osteonecrosis of the jaw (BRONJ). This study determined the effect of the bisphosphonate, zoledronic acid and the replenishment of the MVP by geranylgeraniol on human gingival fibroblasts. Cell viability, apoptosis, morphological analysis using transmission electron microscopy, and gene expression for vascular endothelial growth factor A, bone morphogenic protein 2, ras homologue gene family member B, epiregulin and interferon-alpha were conducted. Results showed cellular viability was decreased in the presence of zoledronic acid and the co-addition of zoledronic acid with geranylgeraniol restored cell viability to control levels. Caspase 3/7 was detected in zoledronic-acid-treated cells indicating apoptosis. Transmission electron microscopy revealed dilation of the rough endoplasmic reticulum with zoledronic acid and the appearance of multiple lipid-like vesicles following the addition of geranylgeraniol. Zoledronic acid significantly (P < 0.05, FR > ± 2) up-regulated vascular endothelial growth factor A, bone morphogenic protein 2, ras homologue gene family member B and epiregulin at one or more time points but not interferon-alpha. Addition of geranylgeraniol resulted in a reduction in the expression of all five genes compared with zoledronic-acid-treated human gingival fibroblasts. The study concluded geranylgeraniol partially reversed the effects of zoledronic acid in human gingival fibroblasts both at the cellular and genetic levels, suggesting the regulation of these genes is mediated via the mevalonate pathway.

Proceedings from the 2013 American Association of Oral and Maxillofacial Surgeons Research Summit

The American Association of Oral and Maxillofacial Surgeons, the Oral and Maxillofacial Surgery Foundation, and the International Association of Oral and Maxillofacial Surgeons sponsored the fifth research summit, which convened on May 2 and 3 in Rosemont, Illinois. The Research Summits are convened biennially to facilitate the discussion and collaboration of oral and maxillofacial surgeons with clinical and basic science researchers in fields affecting the specialty. The goal is to advance the field of oral and maxillofacial surgery through exposure and education in topics that ultimately benefit the oral and maxillofacial surgical patient. This edition of the research summit included the topics of robotic surgery and antiresorptive-related osteonecrosis of the jaws (ARONJ). Most importantly, this research summit saw the development of research interest groups (RIGs) in the fields of anesthesia, maxillofacial oncology and reconstructive surgery, obstructive sleep apnea and orthognathic surgery, temporomandibular joint surgery, and trauma. These RIGs developed specific research goals with a plan to continue working on potential projects at the AAOMS Clinical Trials Course on May 7 to 9, 2013 at the University of Michigan in Ann Arbor. The summit program was developed by the AAOMS Committee on Research Planning and Technology Assessment. The charge of the committee is to encourage and promote research within the specialty and to encourage interdisciplinary collaboration. The research summit serves as a platform for oral and maxillofacial surgeons to lead the goal of advancement of research relevant to the specialty. This article provides an overview of the presentations that were made in the sessions on robotic surgery and ARONJ. The research summit keynote address and two additional presentations on patient registries are summarized and updates from the RIGs that were formed at the 2013 research summit are highlighted.

Alendronate impairs epithelial adhesion, differentiation and proliferation in human oral mucosa

OBJECTIVE

This study aimed at evaluating from a morphological point of view the effects of alendronate (ALN), a widely used nitrogen-containing bisphosphonate for the chronic treatment of osteoporosis, on the oral epithelium of healthy keratinized human oral mucosa. Bisphosphonate-related osteonecrosis of the jaw is a well-known severe consequence, but the effects during chronic therapy on the oral soft tissues are still matter of debate.

MATERIALS AND METHODS

Six women over 60 year-old undergoing treatment of osteoporosis with 70 mg per week of oral ALN (lasting at least 2 years) were recruited and compared with a gender and age-matched group (n = 6). Proliferation, apoptosis, intercellular adhesion and terminal differentiation (TD) were investigated by immunofluorescence. In parallel, ultrastructural analysis was carried out.

RESULTS

By immunofluorescence, a statistically significant decrease in keratinocyte proliferation was detected in the oral epithelium of the ALN group without any sign of apoptosis, but accompanied by a reduction in desmoglein 1 and keratin 10 expressions. In the uppermost layers of the oral epithelium of the ALN group, thin desmosomes were visible by transmission electron microscopy.

CONCLUSION

Our results show that epithelial adhesion, TD and proliferation are affected by ALN therapeutic doses in clinically healthy human oral mucosa.

Bisphosphonate-related osteonecrosis of jaw (BRONJ): diagnostic criteria and possible pathogenic mechanisms of an unexpected anti-angiogenic side effect

Recently, bisphosphonates (BPs) have been widely used in medical practice as anti-resorptive agents owing to their anti-osteoclatic action. In addition, these compounds are also used for their analgesic action and their potential anti-tumour effect. Patients treated with BPs may subsequently develop osteonecrosis of the jaw or maxillary bone after minor local trauma including dental work, recently labelled as bisphosphonate osteonecrosis of jaw (BRONJ). However, the etiopathogenic mechanisms of this pathological condition are poorly understood. Although, several pathways have been proposed for BRONJ occurrence, no single model can explain all morphological changes observed at the macro- and microscopic level. Recent research suggests that BPs may promote an anti-angiogenic effect which contributes directly to the clinical features associated with BRONJ. Remarkably, the anti-angiogenic effect promoting BRONJ might be in keeping with the anti-neoplastic action of BPs. The current review, presents clinical diagnostic criteria. In addition, based on our own experience we describe the histopathological criteria for diagnosis of BRONJ and the possible pathways which may lead to this frustrating pathological condition.

Effects of pamidronate on human alveolar osteoblasts in vitro

PURPOSE

Administration of bisphosphonates has recently been associated with the development of osteonecrotic lesions of the jaw (ONJ). To elucidate the potential contributions of osteogenic cells to the development and regeneration of ONJ, we have isolated primary cells from human alveolar and long/iliac bones, and examined the effects of pamidronate on cell viability, proliferation, osteogenesis, and wound healing.

MATERIALS AND METHODS

Primary human osteoblasts and bone marrow stromal cells were isolated from alveolar and iliac/long bone and marrow tissue. Cellular proliferation, alkaline phosphatase activity, apoptosis (terminal deoxynucleotidyl transferase dUTP nick end labeling, caspase-3, and 4,6-diamidino-2-phenylindole dihydrochloride assays) and wound healing in an in vitro scratch assay were assessed after exposure to pamidronate at a range of clinically relevant doses.

RESULTS

Primary alveolar osteoblasts proliferated at significantly higher rates than long/iliac bone osteoblasts in vitro. Upon exposure of alveolar osteoblasts and long/iliac bone marrow stromal cells to pamidronate for more than 72 hours, we have observed significantly decreased cell viability, proliferation, osteogenesis, and in vitro wound healing at ≥6 × 10(-5) mol/L pamidronate, with the induction of apoptosis in approximately 20% of cell population.

CONCLUSIONS

The remodeling activity of alveolar bone, indicated by higher proliferation of alveolar osteoblasts, could be negatively affected by exposure to high concentrations of pamidronate over extended periods. The absence of anabolic effects of pamidronate on alveolar osteoblasts and the induction of apoptosis in osteogenic cells could negatively affect bone balance at this site and contribute to osteonecrosis of the jaw.

Comparison of effects of clodronate and zoledronic acid on the repair of maxilla surgical wounds - histomorphometric, receptor activator of nuclear factor-kB ligand, osteoprotegerin, von Willebrand factor, and caspase-3 evaluation

BACKGROUND

The aim of this study was to compare clodronate and zoledronic acid regarding their influence on the repair of surgical wounds in maxillae (soft tissue wound and tooth extraction) and their relation to osteonecrosis.

MATERIAL AND METHODS

Thirty-four Wistar rats were allocated into three groups according to the treatment received: (i) 12 animals treated with zoledronic acid, (ii) 12 animals treated with clodronate and (iii) 10 animals that were given saline solution. All animals were subjected to tooth extractions and surgically induced soft tissue injury. Histological analysis of the wound sites was performed by means of hematoxylin-eosin (H&E) staining and immunohistochemical staining for receptor activator of nuclear factor-kB ligand (RANKL), osteoprotegerin (OPG), von Willebrand factor, and caspase-3.

RESULTS

The zoledronic acid group showed higher incidence of non-vital bone than did the clodronate group at the tooth extraction site. At the soft tissue wound site, there were no significant differences in non-vital bone between the test groups. RANKL, OPG, von Willebrand factor, and caspase-3 did not show significant differences between the groups for both sites of surgical procedures.

CONCLUSION

Both of the bisphosphonates zoledronic acid and clodronate are capable of inducing maxillary osteonecrosis. Immunohistochemical analysis suggests that the involvement of soft tissues as the initiator of osteonecrosis development is less probable than has been pointed out.