Serotonergic modulation of nicotine-induced kinetic tremor in mice.

We previously demonstrated that nicotine elicited kinetic tremor by elevating the neural activity of the inferior olive via α7 nicotinic acetylcholine (nACh) receptors. Since α7 nACh receptors reportedly facilitate synaptic monoamine release, we explored the role of 5-HT receptors in induction and/or modulation of nicotine tremor. Treatment of mice with nicotine induced kinetic tremor that normally appeared during movement. The 5-HT1A agonist, 8-hydroxydipropylaminotetraline (8-OH-DPAT), significantly enhanced nicotine-induced tremor and the action of 8-OH-DPAT was antagonized by WAY-100135 (5-HT1A antagonist). In addition, the cerebral 5-HT depletion by repeated treatment with p-chlorophenylalanine did not reduce, but rather potentiated the facilitatory effects of 8-OH-DPAT. In contrast, the 5-HT2 agonist, 2,5-dimethoxy-4-iodoamphetamine (DOI), significantly attenuated nicotine tremor, which was antagonized by ritanserin (5-HT2 antagonist). The 5-HT3 agonist SR-57227 did not affect nicotine-induced tremor. Furthermore, when testing the direct actions of 5-HT antagonists, nicotine tremor was inhibited by WAY-100135, but was unaffected by ritanserin, ondansetron (5-HT3 antagonist) or SB-258585 (5-HT6 antagonist). These results suggest that postsynaptic 5-HT1A receptors are involved in induction of nicotine tremor mediated by α7 nACh receptors. In addition, 5-HT2 receptors have an inhibitory modulatory role in induction of nicotine tremor.

Effects of high-dose major components in oral disinfectants on the cell cycle and apoptosis in primary human gingival fibroblasts in vitro.

We evaluated the effects of high-dose major components in oral disinfectants on oral cells from the standpoints of the cell cycle and apoptosis. We examined the viability and cell cycle of human gingival fibroblasts (HGFs) treated with the components of dental disinfectants, benzethonium chloride (BEC), benzalkonium chloride (BAC), and povidone iodine (PVD-I) using a cell counting kit and flow cytometry. The IC(50) inhibitory concentration value in HGF cultures at 24 hours was 1.3x10(-2) mM BEC, 6.0x10(-3) mM BAC, and 2.6x10(-1) mM PVD-I. In the cell cycle analysis, propidium iodide-stained HGFs were arrested in G(0)/G(1) of the cell cycle by all three disinfectants, and in the apoptosis assay, annexin V-FITC/PI-stained HGFs that became apoptotic at 5.0x10(-2) and 1.0x10(-1) mM BEC and 5.0x10(-2) and 1.0x10(-1) mM BAC, but not in PVD-I at concentrations as high as 5.0x10(-1) mM. Our findings describe the effects of high-dose oral disinfectants, rather than clinical concentrations. Nevertheless, appreciating the effects of high-dose disinfectants absorbed into the human body is important, where they may accumulate in specific tissues and cells.

Mechanism Underlying Organophosphate Paraoxon-Induced Kinetic Tremor.

Organophosphates (OPs) inhibit cholinesterase and hyperactivate the acetylcholinergic nervous system in the brain, causing motor disorders (e.g., tremor and seizures). Here, we performed behavioral and immunohistochemical studies in mice and rats to investigate the tremorgenic mechanism of paraoxon, an active metabolite of parathion. Treating animals with paraoxon (0.15-0.6 mg/kg, i.p.) elicited kinetic tremor in a dose-dependent manner. Expressional analysis of Fos protein, a biomarker of neural excitation, revealed that a tremorgenic dose of paraoxon (0.6 mg/kg) significantly and region-specifically elevated Fos expression in the cerebral cortex (e.g., sensory cortex), hippocampal CA1, globus pallidus, medial habenula, and inferior olive (IO) among 48 brain regions examined. A moderate increase in Fos expression was also observed in the dorsolateral striatum while the change was not statistically significant. Paraoxon-induced tremor was inhibited by the nicotinic acetylcholine (nACh) receptor antagonist mecamylamine (MEC), but not affected by the muscarinic acetylcholine receptor antagonist trihexyphenidyl (THP). In addition, paraoxon-induced Fos expression in the IO was also antagonized by MEC, but not by THP, and lesioning of the IO markedly suppressed tremorgenic action of paraoxon. The present results suggest that OPs elicit kinetic tremor at least partly by activating IO neurons via nACh receptors.

Influence of chlorine dioxide on cell death and cell cycle of human gingival fibroblasts.

OBJECTIVES: The effects of chlorine dioxide (ClO2), sodium hypochlorite (NaOCl), and hydrogen peroxide (H2O2) on cell death and the cell cycle of human gingival fibroblast (HGF) cells were examined. METHODS: The inhibition of HGF cell growth was evaluated using a Cell Counting Kit-8. The cell cycle was assessed with propidium iodide-stained cells (distribution of cells in G0/G1, S, and G2/M phases) using flow cytometry. The patterns of cell death (necrosis and apoptosis) were analyzed using flow cytometry with annexin V-FITC/PI staining. RESULTS: The lethal doses for 50% of the cells (LD50) of ClO2, NaOCl, and H2O2 were 0.16, 0.79, and 0.11 mM, respectively. All three dental disinfectants induced G0/G1 cell cycle arrest. H2O2 induced apoptosis at concentrations of 0.05 and 0.1 mM, while NaOCl and ClO2 did not induce significant apoptosis at any concentration examined. CONCLUSIONS: These results suggest that ClO2 is sufficient for use as a dental disinfectant compared with H2O2 or NaOCl.

High-risk human papillomavirus type 16 E7 oncogene associates with Cdc25A over-expression in oral squamous cell carcinoma.

Cells expressing high-risk human papillomavirus (HPV) E7 protein display impaired checkpoint control after DNA damage and exhibit elevated rates of mutagenesis. Repression of HPV E7 expression results in the subsequent accumulation of hypophosphorylated retinoblastoma protein and repression of the Cdc25A genes. No study has been conducted to elucidate the role of Cdc25A in the development and progression of human oral carcinomas. To confirm Cdc25A protein expression together with HPV, immunohistochemistry, Western blotting, polymerase chain reaction (PCR), and reverse transcriptase (RT)-PCR were performed using various histological subtypes of oral carcinomas. Cdc25A protein was localized predominantly in the cell nuclei in carcinomas, and high expression was found in 54% of primary tumors. HPV-16 E7 was not found in non-neoplastic oral tissues, whereas it was observed in eight (36%) of 22 oral carcinomas. We found a significant correlation between Cdc25A over-expression and HPV-16 E7 positive carcinomas. There was a strong positive correlation between Cdc25A over-expression and tumor size and TNM stage. This study suggests that Cdc25A is likely to be an important mediator in the progression of oral tumors, and HPV-16 E7 may be a sensitive indicator of the involvement of viral oncogenes in oral carcinogenesis.

Apoptotic and necrotic influence of dental resin polymerization initiators in human gingival fibroblast cultures.

The aim of this study was to examine the apoptotic and necrotic influence of four dental resin polymerization initiators--namely benzoyl peroxide (BPO), camphorquinone (CQ), dimethylaminoethyl methacrylate (DMAEMA), and dimethyl-para-toluidine (DMPT)--on human gingival fibroblast (HGF) cells. To this end, the growth inhibition of HGF cells with 1 mM BPO, CQ, and DMAEMA, and 500 microM DMPT was evaluated using Cell Counting Kit-8. Then, cell cycle analysis by flow cytometry was used to assess propidium iodide-stained cells (distribution of cells in G0/G1, S, G2/M phases). All four dental resin polymerization initiators induced G0/G1 cell cycle arrest. As for the patterns of cell death (necrosis and/or apoptosis), they were analyzed using Annexin V-FITC/PI staining with flow cytometry. All four dental resin polymerization initiators most likely induced necrosis.

Immobilization of simulated reducing agent at the surface of SiO2 fillers in dental composite resins.

To reduce the leachability of reducing agents from composite resins, immobilization of a simulated reducing agent at the surface of SiO2 fillers was examined. SiO2 plates were immersed in 2% 3-aminopropyltriethoxy silane/ethanol solution, and then immersed in dimethyl sulfoxide with 0.25 wt% 4-dimethyl amino benzoic acid (DMABA), 2.0 wt% 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride, and 0.5 wt% N-hydroxysuccinimide. Wide-scan spectrum of X-ray photoelectron spectroscopy did not detect carbon contamination. However, narrow scan detected an O=C-N peak at 399.8 eV, suggesting that DMABA could be immobilized on silane-coupled SiO2 plates. Further, surface plasmon resonance analysis indicated the adsorption of MMA at the surface of reducing agent-immobilized plate.

Simple one-week method to construct gene-targeting vectors: application to production of human knockout cell lines.

Targeted gene disruption is a powerful tool for studying gene function in cells and animals. In addition, this technology includes a potential to correct disease-causing mutations. However, constructing targeting vectors is a laborious step in the gene-targeting strategy, even apart from the low efficiency of homologous recombination in mammals. Here, we introduce a quick and simplified method to construct targeting vectors. This method is based on the commercially available MultiSite Gateway technology. The sole critical step is to design primers to PCR amplify genomic fragments for homologous DNA arms, after which neither ligation reaction nor extensive restriction mapping is necessary at all. The method therefore is readily applicable to embryonic stem (ES) cell studies as well as all organisms whose genome has been sequenced. Recently, we and others have shown that the human pre-B cell line Nalm-6 allows for high-efficiency gene targeting. The combination of the simplified vector construction system and the high-efficiency gene targeting in the Nalm-6 cell line has enabled rapid disruption of virtually any locus of the human genome within one month, and homozygous knockout clones lacking a human gene of interest can be created within 2-3 months. Thus, our system greatly facilitates reverse genetic studies of mammalian--particularly human--genes.

The human pre-B cell line Nalm-6 is highly proficient in gene targeting by homologous recombination.

Gene targeting provides a powerful means for analyzing gene function, as exemplified by knockout mouse studies and recent work with the highly recombinogenic chicken DT40 B-lymphocyte line. In human cultured cells, however, the low frequency of gene targeting is a serious barrier to efficiently generate knockout clones. Moreover, commonly used human cell lines are karyotypically abnormal or unstable. Here, we show using promoterless targeting constructs that Nalm-6, a human pre-B ALL cell line, is highly proficient for gene targeting by homologous recombination. Indeed, the efficiency of TP53 gene targeting in Nalm-6 appears nearly two orders of magnitude higher than that in HCT116, a colon cancer cell line popularly used for gene targeting. Expression analysis revealed a lack of MSH2 expression in this cell line. As Nalm-6 has a stable neardiploid karyotype with normal p53 status, our results underscore the usefulness of Nalm-6 for gene knockout studies in humans.

Estrogenic activity of phthalate esters by in vitro VTG assay using primary-cultured Xenopus hepatocytes.

Estrogenic activity of phthalate esters in dental soft resins was evaluated with an amphibian system consisting of a vitellogenin (VTG)-detecting Enzyme-Linked Immunosorbent Assay and a primary-cultured hepatocyte assay using adult male Xenopus laevis. In particular, phthalate esters--Di-n-butyl phthalate (DBP), Butyl phthalyl butyl glycolate (BPBG), Benzyl butyl phthalate (BBP), and Benzyl benzoate (BB)--were investigated. Bisphenol A (BPA) was prepared for comparison with these chemicals, and 17beta-estradiol (E2) was used as a positive control. The chemicals were diluted in dimethyl sulfoxide (DMSO) to obtain final concentrations ranging from 10(-11) to 10(-4) mol/l. BPA induced estrogenic activity at a concentration of 1.1x10(-6) mol/l, while E2 showed at 4.1x10(-11) mol/l. DBP, BBP, BB, and BPBG showed no estrogenic activity at concentrations between 4x10(-7) mol/l and 1x10(-4) mol/l. The latter result indicated that these phthalate esters might be metabolically transformed into non-estrogenic substances in Xenopus hepatocytes. Furthermore, this study demonstrated that through in vitro metabolism assessment, the estrogenic activity of chemical substances could be directly detected in terms of VTG secretion in primary-cultured Xenopus hepatocytes.

SEM observation of collagen fibrils secreted from the body surface of osteoblasts on a CO3apatite-collagen sponge.

The secretion of collagen by osteoblasts was observed by scanning electron microscopy (SEM). Osteoblast-like cells were cultured on a CO3apatite-collagen sponge reinforced with a porous HAp frame. After three days' incubation, a number of newly created matrix fibrils, forming a network structure, were observed at the cell surface. SEM also showed that osteoblasts secreted collagen fibrils from their membrane, and that the collagen fibrils were twisted together. When collagen in an aqueous sol solution was sprayed onto the extremely smooth surface of a mica plate to support the secretion of osteoblasts, a collagen network structure could be clearly observed with atomic force microscopy (AFM). With this in vitro phenomenon, we could confirm the formation of collagen network structure without biological function. Therefore, it was suggested that the CO3apatite-collagen sponge used in this study is a favorable scaffold biomaterial, on which osteoblasts could produce the unmistakable, characteristic extracellular matrix for mineralization. For therapeutic use of hard tissue biomaterials, collagen formation as an extracellular matrix (ECM) is very important because mineralization is subsequent to ECM.

ESR study of camphorquinone/amine photoinitiator systems using blue light-emitting diodes.

New light-activation units equipped with high-illuminant blue light-emitting diodes (LEDs) have recently been proposed as a replacement for the halogen units that are widely used in dentistry to polymerize light-cured resins. The photoinitiators in light-cured dental resins, typified by the camphorquinone (CQ)/amine photoinitiator system, generate primary radicals with light irradiation that attack the double bonds of resin monomers. The physical properties of the cured resins are affected by the generation of primary radicals during the initial stage of polymerization. This study examined two types of photoinitiator systems, CQ/DMPT and CQ/DMAEMA, and three types of curing units, a new LED unit and two conventional halogen units. The primary radicals generated by irradiation were quantified using electron spin resonance (ESR) spectroscopy with a trapping method, using phenyl-tert-butyl nitrone as the trapping agent. The energy efficiencies of the LED and halogen units were compared by quantifying the generated radicals and emitted light energy (J/cm(2)). The energy required to generate a given amount of radicals using the LED unit was smaller than that using the halogen units (p<0.05). These results suggest that the new LED unit performs better than conventional halogen units with respect to light energy.

The extracts of Japanese willow tree species are effective forapoptotic desperation or differentiation of acute myeloid leukemia cells.

BACKGROUND: The antileukemic activity of hot water extract of plant parts of some Japanese willow tree species grown at different levels of nitrogen were examined. MATERIALS AND METHODS: Water extracts of willow leaves were prepared for this studies in different level of nitrogen nutrition. RESULTS: The extracts obtained from the leaves and stem exhibited anti-leukemic activities prominently. The crude hot water extracts of the young growing parts including apex, matured leaves and stem, killed the blasts of acute myeloid leukemia (AML) cells, (HL60 and NB4) after 48h incubation, however, such desperation was far less in the root extract. Similar to the plant parts, response of extracts obtained from different willow species was not identical; the proportion of dead cells relative to whole cells of the culture medium ranged from 21% to 93% among the species. Leaf extracts obtained from the responsive willow species decreased the live cell percentage and increased the dead cell percentage at higher level of nitrogen nutrition. The mode of desperation of leaf extract treated AML cells in such species appeared to be cell apoptosis as shown by binding with fluorescein isothiocyanate (FITC) -labeled Annexin V. CONCLUSION: Differentiation of alive AML cells continued unabated and apoptosis was poor when extract of an unresponsive species added to the culture medium.

Irradiation effect on osteoclastogenesis stimulated by breast cancer cells.

To examine the effects of carbon ion and gamma ray irradiation on cancer-induced osteoclastogenesis, mouse calvaria MC3T3-E1 cells were cultured with conditioned medium from irradiated and non-irradiated MCF7 human breast cancer cells. The authors examined RANKL and OPG mRNA expression in osteoblastic MC3T3-E1 cells following treatment with conditioned MCF7 medium. Co-cultured MC3T3-E1 and bone marrow cells treated with conditioned medium from irradiated MCF7 cells showed decreased numbers of osteoclasts, assessed using TRAP staining. Conditioned medium from control MCF7 cells elevated the RANKL/OPG mRNA ratio in MC3T3-E1 cells; this effect was suppressed by carbon ion irradiation of the MCF7 cells. These data demonstrate that indirect interactions between breast cancer cells and MC3T3-E1 cells induce osteoclastogenesis in vitro through modulation of RANKL expression and that this process is suppressed by carbon ion irradiation.

Hydroxylated polychlorinated biphenyls (OH-PCBs) induce vitellogenin through estrogenic activity in primary-cultured hepatocytes of the Xenopus laevis.

Vitellogenin (VTG)-inducing activities of 21 kinds of hydroxylated polychlorinated biphenyls (OH-PCBs) were investigated by an assay system using the primary-cultured hepatocyte of the adult male Xenopus laevis. An enzyme-linked immunoabsorbent assay (ELISA) was able to detect VTG at a minimum detection limit of 0.2ngmL(-1). The levels of VTG production in hepatocytes of male X. laevis exposed to six kinds of OH-PCB isomers (2'-OH-CB30, 3'-OH-CB30, 4'-OH-CB30, 4'-OH-CB50, 4'-OH-CB61 4'-OH-CB65) were significantly higher as compared to the control group (p<0.05). The relative ranking of the OH-PCBs was E2 (100%), 4'-OH-CB30 (2.0%)>2'-OH-CB30 (0.15%)>4'-OH-CB61 (0.046%)>3'-OH-CB30 (0.013%)>4'-OH-CB50 (0.002%)>4'-OH-CB65 (0.0001%). Although there were some differences between the estrogenicity values by the VTG-inducing activities and yeast two-hybrid assay for human estrogen receptor alpha (ERalpha). The results from VTG-assays suggested that an important factor for determining estrogenicity is the positions of the hydroxyl group and chlorine with the highest activity resulting from a para-hydroxyl group. The OH-PCB structures of high rank order in the VTG-assay had no chlorine substituted phenolic ring. Moreover, the meta-chlorine substituted phenolic ring is an important factor in determining estrogenicity. The OH-PCBs with meta-chlorine substituted phenolic ring did not show estrogenicity during VTG-assay.

Loss of 14-3-3 sigma protein expression and presence of human papillomavirus type 16 E6 in oral squamous cell carcinoma.

OBJECTIVE: To confirm the expression of 14-3-3 sigma in oral malignant lesions and in adjacent nonmalignant oral epithelium to provide a clue to the involvement in the cell cycle progression and note any association with human papillomavirus (HPV) status. 14-3-3 Sigma plays important roles in a wide range of vital regulatory processes, including signal transduction, apoptosis, cell cycle progression, and DNA replication. 14-3-3 Sigma is an exclusive epithelial marker, and data on its expression in different malignancies are very scarce. DESIGN: Western blotting, immunohistochemical analysis, and polymerase chain reaction were performed. SETTING: An academic university laboratory. PATIENTS: Adults with known oral squamous cell carcinomas (SCCs) that were surgically resected. MAIN OUTCOME MEASURES: The DNA of HPV-16 E6 was detected by polymerase chain reaction, and protein expression of 14-3-3 sigma was evaluated by Western blot and immunohistochemical analysis. RESULTS: The immunoreactive 14-3-3 sigma protein was detected mainly in the cytoplasm of differentiated squamous cells of oral SCC lesions as well as adjacent nonmalignant squamous mucosa. Immunoreactivity for 14-3-3 sigma was observed in 93% of SCC lesions (27 of 29), including HPV-negative cases. No significant association was observed between 14-3-3 sigma expression and clinicopathologic parameters. A statistically significant correlation was found between 14-3-3 sigma protein expression and the Ki-67 labeling index. 14-3-3 Sigma expression was correlated inversely with HPV-16 E6. CONCLUSION: These findings suggest that 14-3-3 sigma may act as a negative regulator of the cell cycle progression in oral SCC.

Human Mus81 and FANCB independently contribute to repair of DNA damage during replication.

Recent studies suggest a crucial role for homologous recombination (HR) in repairing replication-associated DNA lesions. In mammals, the Mus81 endonuclease and the Fanconi anemia (FA) pathway have been implicated in HR repair; however, their functional relationship has remained unexplored. Here, we knockout the genes for Mus81 and FANCB, a component of the FA core complex, in the human Nalm-6 cell line. We show that Mus81 plays an important role in cell proliferation to suppress cell death when FANCB is missing, indicating a functional linkage between Mus81 and the FA pathway. In DNA cross-link repair, roles for Mus81 and the FA pathway appear to have an overlapping function. Intriguingly, Mus81 and FANCB act independently in surviving exposure to camptothecin (CPT). Although CPT-induced FANCD2 and Mus81 foci co-localize with Rad51, loss of Mus81, but not FANCB, results in significantly decreased levels of spontaneous and CPT-induced sister chromatid exchanges (SCEs). In addition, Mus81, unlike FANCB, has no significant role in gene targeting as well as in repairing hydroxyurea (HU)-induced stalls of replication forks. Collectively, our results provide the first evidence for differential functions of Mus81 and the FA pathway in repair of DNA damage during replication in human cells.

Acceleration of bone formation with BMP2 in frame-reinforced carbonate apatite-collagen sponge scaffolds.

The development is expected of scaffold biomaterials that feature a shape-maintaining property in addition to high porosity and large pores that cells can easily invade. To develop a new biodegradable scaffold biomaterial reinforced with a frame, synthesized carbonate apatite (CO3Ap) was mixed with neutralized collagen gel, and the CO3Ap-collagen mixtures were lyophilized into sponges in a porous hydroxyapatite (HAp) frame ring. X-ray diffraction and Fourier transform infrared spectroscopy (FT-IR) analyses together with chemical analysis indicated that the synthesized CO3Ap had a crystalline nature and a chemical composition similar to that of bone. Scanning electron microscope (SEM) observation showed that the CO3Ap-collagen sponge had a sui pore size for cell invasion. In proliferation and differentiation experiments with osteoblasts, alkaline phosphatase and osteopontin activity were clearly detected. When these sponge-frame complexes with bone morphogenic protein (rh-BMP2) were implanted beneath the periosteum cranii of rats, significant new bone was created at the surface of the periosteum cranii after 4 weeks of implantation. These reinforced CO3Ap-collagen sponges with rh-BMP2 are expected to be used as hard tissue scaffold biomaterials for the therapeutic purpose of the rapid cure of bone defects.

UCN-01 (7-hydroxystaurosporine) induces apoptosis and G1 arrest of both primary and metastatic oral cancer cell lines in vitro.

OBJECTIVE: Our aim was to clarify the in vitro antiproliferative effects of UCN-01 on human oral squamous cell carcinoma (OSCC) cell lines. STUDY DESIGN: Cell growth was measured by MTT assay, and cell cycling was assessed by flow cytometry. Changes in the levels of protein and protein phosphorylation were analyzed by Western blotting. In addition, tumor cell apoptosis was assessed by propidium iodide (PI) and annexin double-staining. RESULTS: UCN-01 significantly inhibited the proliferation of all the OSCC cell lines, with a 50% inhibition concentration of about 300 nmol/L, and induced G1 arrest in these cell lines in a dose-dependent manner. Primary and metastatic oral cancer cell lines had different sensitivities to UCN-01. Our results showed that HSC-3 cells (primary-type OSCC) are less sensitive than LMF4 cells (metastatic-type OSCC) to UCN-01. In addition, the induction of p21 in OSCCs was found to be important for the suppression of tumor growth. CONCLUSION: The results of this study suggest that UCN-01 induces apoptosis and G1 arrest in OSCCs, albeit with different sensitivity of the primary and metastatic cell lines to UCN-01.

Different effects of carbon ion and gamma-irradiation on expression of receptor activator of NF-kB ligand in MC3T3-E1 osteoblast cells.

We investigated the effects of carbon ion and gamma-irradiation on osteoblastic MC3T3-E1 cells by comparing mRNA expression levels for RANKL and osteoprotegerin by RT-PCR. MC3T3-E1 cells were irradiated with 2, 4, or 6 Gy of carbon ions or gamma-rays, and total RNA was harvested 1, 2, 3, 5, or 7 days after irradiation. The RANKL mRNA/OPG mRNA ratio in carbon ion-irradiated MC3T3-E1 cells was lower, while in gamma-irradiated MC3T3-E1 cells this ratio was higher than in non-irradiated cells. To evaluate osteoclastogenesis of MC3T3-E1 cells, carbon ion- or gamma-irradiated cells were co-cultured with non-irradiated cells from murine bone marrow. Staining for tartrate-resistant acid phosphatase (TRAP) in co-cultures showed that carbon ion irradiation suppressed osteoclastogenesis. This result is consistent with the lower RANKL/OPG mRNA ratio for carbon ion-irradiated cells. These results suggest that carbon ion irradiation acts primarily on osteoblastic cells, leading to a decrease in the RANKL/OPG mRNA ratio. This effect, in turn, leads to a decrease in osteoclastogenesis and osteoclast activity, which results in an increase in bone volume.