Structural and functional changes in the alveolar bone osteoclasts of estrogen-treated rats

Effects of different calcium-silicate based materials on fracture resistance of immature permanent teeth with replacement root resorption and osteoclastogenesis

Objectives

This study evaluated the effects of Biodentine (BD), Bio-C Repair (BCR), and mineral trioxide aggregate (MTA) plug on the fracture resistance of simulated immature teeth with replacement root resorption (RRR) and in vitro-induced osteoclastogenesis.

Materials and Methods

Sixty bovine incisors simulating immature teeth and RRR were divided into 5 groups: BD and BCR groups, with samples completely filled with the respective materials; MTA group, which utilized a 3-mm apical MTA plug; RRR group, which received no root canal filling; and normal periodontal ligament (PL) group, which had no RRR and no root canal filling. All the teeth underwent cycling loading, and compression strength testing was performed using a universal testing machine. RAW 264.7 macrophages were treated with 1:16 extracts of BD, BCR, and MTA containing receptor activator of nuclear factor-kappa B ligand (RANKL) for 5 days. RANKL-induced osteoclast differentiation was assessed by staining with tartrate-resistant acid phosphatase. The fracture load and osteoclast number were analyzed using 1-way ANOVA and Tukey's test (α = 0.05).

Results

No significant difference in fracture resistance was observed among the groups (p > 0.05). All materials similarly inhibited osteoclastogenesis (p > 0.05), except for BCR, which led to a lower percentage of osteoclasts than did MTA (p < 0.0001).

Conclusions

The treatment options for non-vital immature teeth with RRR did not strengthen the teeth and promoted a similar resistance to fractures in all cases. BD, MTA, and BCR showed inhibitory effects on osteoclast differentiation, with BCR yielding improved results compared to the other materials.

Effects of Vitamin A (Retinol) Release from Calcium Phosphate Matrices and Porous 3D Printed Scaffolds on Bone Cell Proliferation and Maturation

Vitamin A is a fat-soluble compound widely known for vision health. Highly variable reports on its effects on bone health have necessitated further research to truly understand its role on bone cell proliferation. Retinol, one bioactive form of vitamin A, is incorporated into synthetic bone graft scaffolds for low load-bearing clinical bone treatment. The objective of this work is to understand the effects of retinol on osteoblast and osteoclast cells when embedded within calcium phosphate matrices, including interconnected porous 3D printed tricalcium phosphate scaffolds. Results show that hydrophobic retinol can be released from bone scaffolds when a combination of biodegradable polymers, polycaprolactone and polyethylene glycol, are employed as drug carriers. The release of retinol in vitro can support a 20 ± 1% increase in osteoblast (bone-forming) cell proliferation with proper cell adhesion and filopodial extensions. Osteoclast cell morphology is necrosed and torn with a reduction in proliferation at approximately 6 ± 1% when retinol is present. In addition, inhibition of osteoclastic resorption pit bays is noted using scanning electron microscopy. With the scaffolds' round pore interconnectivity facilitating retinol release, this system can provide an alternative to traditional bone grafts while additionally supporting bone healing through enhanced osteoblast cell proliferation and inhibition of osteoclast resorption activity.

Associations of Fat Mass and Fat Distribution With Bone Mineral Density in Non-Obese Postmenopausal Chinese Women Over 60 Years Old

BACKGROUND

Bone mineral density (BMD) loss is a major complication of menopause, and this loss is closely associated with Fat mass (FM). The relationship between FM, fat distribution (FD), and BMD in postmenopausal women, however, remains incompletely understood. The present study was thus developed to explore these associations between body fat accumulation, FD, and BMD among non-obese postmenopausal women over the age of 60.

METHODS

This was a cross-sectional analysis of 357 healthy postmenopausal women between the ages of 60.2 and 86.7 years. Dual-energy X-ray absorptiometry (DXA) was utilized to measure total and regional BMD as well as fat-related parameters including total FM, android and gynoid fat, body fat percentage (BF%), and total lean mass (LM) for all subjects. The android-to-gynoid fat ratio (AOI) was used to assess FD. Pearson's correlation testing and multiple regression analyses were used to explore relationships among AOI, LM, FM, and BMD.

RESULTS

Both LM and FM were positively correlated with total and regional BMD in univariate analysis (all P < 0.01), whereas BMD was not significantly associated with AOI in any analyzed site other than the head. Multivariate linear regression models corrected for age, height, and years post-menopause, revealed a sustained independent positive relationship between FM and BMD (standard β range: 0.141 - 0.343, P < 0.01). The relationship between FM and BMD was unaffected by adjustment for LM (standard β range: 0.132 - 0.258, P < 0.01), whereas AOI had an adverse impact on BMD at most analyzed skeletal sites (total body, hip, femoral neck, arm, leg, and head) (standard β range: -0.093 to -0.232, P < 0.05). These findings were unaffected by using BF% in place of FM (standard β range: -0.100 to -0.232, P < 0.05).

CONCLUSIONS

In this cohort of non-obese postmenopausal women over the age of 60 from China, total FM was positively associated with BMD, while AOI was negatively correlated with BMD. As such, a combination of proper weight gain and the control of central obesity may benefit the overall bone health of women after menopause.

The phytochemical plumbagin reciprocally modulates osteoblasts and osteoclasts

Bone metabolism is essential for maintaining bone mineral density and bone strength through a balance between bone formation and bone resorption. Bone formation is associated with osteoblast activity whereas bone resorption is linked to osteoclast differentiation. Osteoblast progenitors give rise to the formation of mature osteoblasts whereas monocytes are the precursors for multi-nucleated osteoclasts. Chronic inflammation, auto-inflammation, hormonal changes or adiposity have the potential to disturb the balance between bone formation and bone loss. Several plant-derived components are described to modulate bone metabolism and alleviate osteoporosis by enhancing bone formation and inhibiting bone resorption. The plant-derived naphthoquinone plumbagin is a bioactive compound that can be isolated from the roots of the Plumbago genus. It has been used as traditional medicine for treating infectious diseases, rheumatoid arthritis and dermatological diseases. Reportedly, plumbagin exerts its biological activities primarily through induction of reactive oxygen species and triggers osteoblast-mediated bone formation. It is plausible that plumbagin's reciprocal actions - inhibiting or inducing death in osteoclasts but promoting survival or growth of osteoblasts - are a function of the synergy with bone-metabolizing hormones calcitonin, Parathormone and vitamin D. Herein, we develop a framework for plausible molecular modus operandi of plumbagin in bone metabolism.

Bothrops moojeni Venom and Its Components Strongly Affect Osteoclasts' Maturation and Protein Patterns

Osteoclasts (OCs) are important for bone maintenance, calcium balance, and tissue regeneration regulation and are involved in different inflammatory diseases. Our study aimed to evaluate the effect of Bothrops moojeni's venom and its low and high molecular mass (HMM and LMM) fractions on human peripheral blood mononuclear cell (PBMC)-derived OCs' in vitro differentiation. Bothrops moojeni, a Brazilian lanced-head viper, presents a rich but not well-explored, venom composition. This venom is a potent inducer of inflammation, which can be used as a tool to investigate the inflammatory process. Human PBMCs were isolated and induced to OC differentiation following routine protocol. On the fourth day of differentiation, the venom was added at different concentrations (5, 0.5, and 0.05 µg/mL). We observed a significant reduction of TRAP+ (tartrate-resistant acid phosphatase) OCs at the concentration of 5 µg/mL. We evaluated the F-actin-rich OCs structure's integrity; disruption of its integrity reflects bone adsorption capacity. F-actin rings phalloidin staining demonstrated that venom provoked their disruption in treated OCs. HMM, fraction reduces TRAP+ OCs at a concentration of 5 µg/mL and LMM fraction at 1 µg/mL, respectively. Our results indicate morphological changes that the venom induced cause in OCs. We analyzed the pattern of soluble proteins found in the conditioned cell culture medium OCs treated with venom and its fractions using mass spectrometry (LC-MS/IT-Tof). The proteomic analyses indicate the possible pathways and molecular mechanisms involved in OC reduction after the treatment.

Immunoexpression pattern of autophagy mediators in alveolar bone osteoclasts following estrogen withdrawal in female rats

It is known that estrogen deficiency increases osteoclast formation and activity. Autophagy, a cell survival pathway, has been shown to be crucial for osteoclast function. However, little is known about the effects of estrogen depletion on osteoclast autophagy. Here, we evaluated the effects of estrogen deficiency in the immunoexpression of autophagy mediators in alveolar bone osteoclasts of ovariectomized rats. Twelve adult female rats were ovariectomized (OVX-group) or SHAM-operated (SHAM-group). After three weeks, the rats were euthanized and maxillary fragments containing alveolar bone of the first molars were processed for light microscopy or transmission electron microscopy (TEM). Paraffin-sections were subjected to the TRAP method (osteoclast marker) or to the immunohistochemical detections of beclin-1, LC3α, and p62 (autophagy mediators); araldite-sections were processed for TEM. The number of TRAP-positive osteoclasts and the number of immunolabeled-multinucleated cells (MNCs) along the alveolar bone surface of the first molar were computed. The number of TRAP-positive osteoclasts and the number of beclin-1-, LC3α- and p62-immunolabelled osteoclasts were significantly higher in OVX-group than the SHAM-group. MNCs were frequently located juxtaposed to Howship lacunae along the alveolar bone surface, indicating that these cells are osteoclasts. TEM revealed osteoclasts exhibiting autophagosomes. Our data indicate that autophagy plays an important role during estrogen deficiency-induced osteoclastogenesis. Thus, our results contribute to a better understanding on the role of autophagy on osteoclasts under estrogenic deficiency, and reinforce the idea that modulation of autophagy may be a useful tool to inhibit excessive oral bone resorption in post-menopausal women.

Immunoinflammatory response and bioactive potential of GuttaFlow bioseal and MTA Fillapex in the rat subcutaneous tissue

To evaluate the effect of GuttaFlow bioseal (GFB) and MTA Fillapex (MTAF) in comparison with Endofill (EF) in the subcutaneous tissue. Polyethylene tubes with GFB, MTAF, EF or empty tubes (control group; CG) were implanted into subcutaneous of rats. After 7, 15, 30 and 60 days, the capsule thickness, inflammatory reaction, interleukin-6 (IL-6), vascular endothelial growth factor (VEGF), caspase-3, TUNEL-positive cells, von Kossa and ultrastructural features were evaluated. The data were statistically analyzed (p ≤ 0.05). At all periods, the number of IL-6- and VEGF-immunolabelled cells, and capsule thickness were lower in GFB than MTAF, which was lower than EF (p < 0.0001). At 60 days, the number of inflammatory cells was similar in GFB and MTAF (p = 0.58). Significant differences in the number of TUNEL- and caspase-3-positive cells were not observed among GFB, MTAF and CG whereas the highest values were found in EF specimens. The EF specimens exhibited several cells with condensed chromatin, typical of apoptosis. von Kossa-positive and birefringent structures were only observed in GFB and MTAF, suggesting the presence of calcite crystals. Taken together, these results show that cellular and structural damage induced by GFB and MTAF sealers were recovery over time. Moreover, these sealers express bioactive potential in subcutaneous tissue.

Osteoclasts in the Inflammatory Arthritis: Implications for Pathologic Osteolysis

The enhanced differentiation and activation of osteoclasts (OCs) in the inflammatory arthritis such as rheumatoid arthritis (RA) and gout causes not only local bone erosion, but also systemic osteoporosis, leading to functional disabilities and morbidity. The induction and amplification of NFATc1, a master regulator of OC differentiation, is mainly regulated by receptor activator of NF-κB (RANK) ligand-RANK and calcium signaling which are amplified in the inflammatory milieu, as well as by inflammatory cytokines such as TNFα, IL-1β and IL-6. Moreover, the predominance of CD4⁺ T cell subsets, which varies depending on the condition of inflammatory diseases, can determine the fate of OC differentiation. Anti-citrullinated peptide antibodies which are critical in the pathogenesis of RA can bind to the citrullinated vimentin on the surface of OC precursors, and in turn promote OC differentiation and function via IL-8. In addition to adaptive immunity, the activation of innate immune system including the nucleotide oligomerization domain leucine rich repeat with a pyrin domain 3 inflammasome and TLRs can regulate OC maturation. The emerging perspectives about the diverse and close interactions between the immune cells and OCs in inflammatory milieu can have a significant impact on the future direction of drug development.

A randomized clinical trial evaluating maxillary sinus augmentation with different particle sizes of demineralized bovine bone mineral: histological and immunohistochemical analysis

This study was performed to investigate sinus floor augmentation with two different particle sizes of demineralized bovine bone mineral (DBBM) by means of histological and immunohistochemical (IHC) analysis. A randomized clinical trial was conducted involving 10 individuals requiring two-stage bilateral maxillary sinus augmentation for implant installation. The patients were randomly divided into two groups following a split-mouth design: the maxillary sinus on one side was filled with small-sized particles (0.25-1mm) and on the contralateral side with large-sized particles (1-2mm). After a healing period of 8 months, 25 implants were placed. During implant site preparation, bone biopsies were obtained from each sinus, perpendicular to the long axis of the implant (buccal-palatal direction), for descriptive and histomorphometric analyses. IHC staining for protein expression of osteocalcin (OCN), vascular endothelial growth factor (VEGF), and tartrate-resistant acid phosphatase (TRAP) was also performed. Histomorphometric analysis revealed no statistically significant difference in the percentage of biomaterial (32.4±8.56% and 38.0±6.92%), newly formed bone (36.1±9.60% and 36.7±5.79%), or connective tissue (30.4±8.63% and 23.8±6.16%) between the small- and large-sized particle groups, respectively. IHC analysis did not reveal differences in the expression of OCN, VEGF, or TRAP. These findings suggest that both particle sizes of DBBM are effective for bone augmentation in the maxillary sinus.

Silicosis decreases bone mineral density in rats

Silicosis is the most common occupational lung disease in China, and is associated with a variety of complications, many of which are poorly understood. For example, recent data indicate that silicosis associates with the development of osteopenia, and in some cases this bone loss is severe, meeting criteria for osteoporosis. Although many factors are likely to contribute to this relationship, including a sedentary lifestyle in patients with advanced silicotic lung disease, we hypothesized that silica might directly reduce bone mineral density. In the present study, six Wistar rats were exposed to silica for 24 weeks in order to induce pulmonary silicosis and examine the relationship to bone mineral density. As expected, all rats exposed to silica developed severe pulmonary fibrosis, as manifested by the formation of innumerable silicotic nodules and the deposition of large amounts of interstitial collagen. Moreover, micro-CT results showed that bone mineral density (BMD) was also significantly reduced in rats exposed to silica when compared control animals and this associated with a modest reduction in serum calcium and 25-hydroxyvitamin D levels. In addition, we found that decreased BMD was also linked to increased osteoclast activity as well as fibrosis-like changes, and to the deposition of silica within bone marrow. In summary, our findings support the hypothesis that silicosis reduces bone mineral density and provide support for ongoing investigations into the mechanisms causing osteopenia in silicosis patients.

Contributions of fat mass and fat distribution to hip bone strength in healthy postmenopausal Chinese women

The fat and bone connection is complicated, and the effect of adipose tissue on hip bone strength remains unclear. The aim of this study was to clarify the relative contribution of body fat accumulation and fat distribution to the determination of proximal femur strength in healthy postmenopausal Chinese women. This cross-sectional study enrolled 528 healthy postmenopausal women without medication history or known diseases. Total lean mass (LM), appendicular LM (ALM), percentage of lean mass (PLM), total fat mass (FM), appendicular FM (AFM), percentage of body fat (PBF), android and gynoid fat amount, android-to-gynoid fat ratio (AOI), bone mineral density (BMD), and proximal femur geometry were measured by dual energy X-ray absorptiometry. Hip structure analysis was used to compute some variables as geometric strength-related parameters by analyzing the images of the hip generated from DXA scans. Correlation analyses among anthropometrics, variables of body composition and bone mass, and geometric indices of hip bone strength were performed with stepwise linear regression analyses as well as Pearson's correlation analysis. In univariate analysis, there were significantly inverse correlations between age, years since menopause (YSM), hip BMD, and hip geometric parameters. Bone data were positively related to height, body weight, LM, ALM, FM, AFM, and PBF but negatively related to AOI and amount of android fat (all P < 0.05). AFM and AOI were significantly related to most anthropometric parameters. AFM was positively associated with height, body weight, and BMI. AFM was negatively associated with age and YSM. AOI was negatively associated with height, body weight, and BMI. AOI positively associated with age and YSM. LM, ALM, and FM had a positive relationship with anthropometric parameters (P < 0.05 for all). PLM had a negative relationship with those parameters. The correlation between LM, ALM, FM, PLM, ALM, age, and YSM was not significant. In multivariate linear regression analysis, the hip bone strength was observed to have a consistent and unchanged positive association with AFM and a negative association with AOI, whereas its association with other variables of body composition was not significant after adjusting for age, years since menopause, height, body weight, and BMI. AFM may be a positively protective effect for hip bone strength while AOI, rather than android fat, shows a strong negative association with hip bone strength after making an adjustment for confounders (age, YSM, height, body weight, and BMI) in healthy postmenopausal Chinese women. Rational weight control and AOI reduction during menopause may have vital clinical significance in decreasing postmenopausal osteoporosis.

Apoptosis and reduced microvascular density of the lamina propria during tooth eruption in rats

During tooth eruption, structural and functional changes must occur in the lamina propria to establish the eruptive pathway. In this study, we evaluate the structural changes that occur during lamina propria degradation and focus these efforts on apoptosis and microvascular density. Fragments of maxilla containing the first molars from 9-, 11-, 13- and 16-day-old rats were fixed, decalcified and embedded in paraffin. The immunohistochemical detection of vascular endothelial growth factor (VEGF), caspase-3 and MAC387 (macrophage marker), and the TUNEL method were applied to the histological molar sections. The numerical density of TUNEL-positive cells and VEGF-positive blood vessel profiles were also obtained. Data were statistically evaluated using a one-way anova with the post-hoc Kruskal-Wallis or Tukey test and a significance level of P ≤ 0.05. Fragments of maxilla were embedded in Araldite for analysis under transmission electron microscopy (TEM). TUNEL-positive structures, fibroblasts with strongly basophilic nuclei and macrophages were observed in the lamina propria at all ages. Using TEM, we identified processes of fibroblasts or macrophages surrounding partially apoptotic cells. We found a high number of apoptotic cells in 11-, 13- and 16-day-old rats. We observed VEGF-positive blood vessel profiles at all ages, but a significant decrease in the numerical density was found in 13- and 16-day-old rats compared with 9-day-old rats. Therefore, the establishment of the eruptive pathway during the mucosal penetration stage depends on cell death by apoptosis, the phagocytic activity of fibroblasts and macrophages, and a decrease in the microvasculature due to vascular cell death. These data point to the importance of vascular rearrangement and vascular neoformation during tooth eruption and the development of oral mucosa.

Biology of Bone Tissue: Structure, Function, and Factors That Influence Bone Cells

Bone tissue is continuously remodeled through the concerted actions of bone cells, which include bone resorption by osteoclasts and bone formation by osteoblasts, whereas osteocytes act as mechanosensors and orchestrators of the bone remodeling process. This process is under the control of local (e.g., growth factors and cytokines) and systemic (e.g., calcitonin and estrogens) factors that all together contribute for bone homeostasis. An imbalance between bone resorption and formation can result in bone diseases including osteoporosis. Recently, it has been recognized that, during bone remodeling, there are an intricate communication among bone cells. For instance, the coupling from bone resorption to bone formation is achieved by interaction between osteoclasts and osteoblasts. Moreover, osteocytes produce factors that influence osteoblast and osteoclast activities, whereas osteocyte apoptosis is followed by osteoclastic bone resorption. The increasing knowledge about the structure and functions of bone cells contributed to a better understanding of bone biology. It has been suggested that there is a complex communication between bone cells and other organs, indicating the dynamic nature of bone tissue. In this review, we discuss the current data about the structure and functions of bone cells and the factors that influence bone remodeling.

Bergapten prevents lipopolysaccharide mediated osteoclast formation, bone resorption and osteoclast survival

PURPOSE

This study was designed to investigate the potential effect of bergapten on lipopolysaccharide (LPS)-mediated osteoclast formation, bone resorption and osteoclast survival in vitro.

METHODS

After osteoclast precursor RAW264.7 cells were treated with bergapten (5, 20, 40 μmol/L) for 72 hours in the presence of LPS (100 ng/ml), osteoclastogenesis was identified by tartrate-resistant acid phosphatase (TRAP) staining, and the number of TRAP-positive multinucleated cells [TRAP(+)MNCs] per well were counted. To investigate the effect of bergapten on osteoclastic bone resorption, RAW264.7 cells were treated with bergapten for six days in the presence of LPS, and the area of bone resorption was analyzed with Image Pro-Plus. Next, we examined apoptosis of RAW264.7 cells after bergapten incubation for 48 hours by flow cytometer using annexin V/propidium iodide (PI) double labeling. Finally, osteoclast survival was observed by Hoechst 33342 labeling and Western blotting after bergapten treatment for 24 hours.

RESULTS

Data showed that bergapten (5-40 μmol/L) dose-dependently inhibited LPS-induced osteoclast formation and bone resorption. Treatment with bergapten triggered apoptotic death of osteoclast precursor RAW264.7 cells in a dose-dependent manner. Furthermore, bergapten significantly reduced the survival of mature osteoclast, as demonstrated by emergence of apoptotic nuclei and activation of apoptotic protein caspase 3/9.

CONCLUSIONS

These findings suggest that bergapten effectively prevents LPS-induced osteoclastogenesis, bone resorption and survival via apoptotic response of osteoclasts and their precursors. The study identifies bergapten as an inhibitor of osteoclast formation and bone resorption and provides evidence that bergapten might be beneficial as an alternative for prevention and treatment of inflammatory bone loss.

The effect of orally administered epigallocatechin-3-gallate on ligature-induced periodontitis in rats

BACKGROUND AND OBJECTIVE

Epigallocatechin-3-gallate (EGCG) is known for its beneficial properties, including anti-inflammatory and anti-oxidative activities. Recently, reports have suggested that EGCG plays a pivotal role in regulating cytokine expression and osteoclastic activity. In the present study, we investigated whether orally administered EGCG has a therapeutic effect on ligature-induced periodontitis.

MATERIALS AND METHODS

Forty-eight Sprague-Dawley rats were treated with EGCG or phosphate-buffered saline. Periodontitis was induced by tying a ligature for 7 d. After removing ligation, EGCG (200 mg/kg) or phosphate-buffered saline was administered via oral gavage on a daily basis. Rats were killed after 1, 2 and 4 wk of administration. Histologic and histomorphometric analyses, tartrate resistant acid phosphatase staining and immunohistochemistry were carried out.

RESULTS

In the control group, bone loss did not recover even after the causative factor of periodontitis was eliminated. On the other hand, distance from cemento-enamel junction to alveolar bone crest, long junctional epithelium and collagen destruction were reduced in the EGCG group. Decreased interleukin (IL)-6 expression was shown from the early stage of EGCG administration, followed by reduced tumor necrosis factor (TNF) expression at week 4 EGCG group. The CT area showed a higher decrease of IL-6 expression between the control and EGCG group than alveolar bone area. Downregulation of TNF and IL-6 expression led to a decrease in osteoclast number and activity, which resulted in reduced bone loss.

CONCLUSIONS

Systemic administration of EGCG could have a therapeutic effect on damaged periodontal tissue. Inhibited cytokine expression, including TNF and IL-6 is responsible for the reduction in osteoclast formation, osteoclastic activity and collagen destruction.

Increased apoptosis in osteoclasts and decreased RANKL immunoexpression in periodontium of cimetidine-treated rats

It has been demonstrated that histamine interferes with the recruitment, formation and activity of osteoclasts via H(1)- and H(2)-receptors. Cimetidine is a H(2)-receptor antagonist used for treatment of gastric ulcers that seems to prevent bone resorption. In this study, a possible cimetidine interference was investigated in the number of alveolar bone osteoclasts. The incidence of osteoclast apoptosis and immunoexpression of RANKL (receptor activator of nuclear factor κB ligand) was also evaluated. Adult male rats were treated with 100 mg kg(-1) of cimetidine for 50 days (CimG); the sham group (SG) received saline. Maxillary fragments containing the first molars and alveolar bone were fixed, decalcified and embedded in paraffin. The sections were stained by H&E or submitted to tartrate-resistant acid phosphatase (TRAP) method. TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling) method and immunohistochemical reactions for detecting caspase-3 and RANKL were performed. The number of TRAP-positive osteoclasts, the frequency of apoptotic osteoclasts and the numerical density of RANKL-positive cells were obtained. Osteoclast death by apoptosis was confirmed by transmission electron microscopy (TEM). In CimG, TRAP-positive osteoclasts with TUNEL-positive nuclei and caspase-3-immunolabeled osteoclasts were found. A significant reduction in the number of TRAP-positive osteoclasts and a high frequency of apoptotic osteoclasts were observed in CimG. Under TEM, detached osteoclasts from the bone surface showed typical features of apoptosis. Moreover, a significant reduction in the numerical density of RANKL-positive cells was observed in CimG. The significant reduction in the number of osteoclasts may be due to cimetidine-induced osteoclast apoptosis. However, RANKL immunoexpression reduction also suggests a possible interference of cimetidine treatment in the osteoclastogenesis.