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Cdc42 (cell division cycle 42) is ubiquitously expressed small GTPases belonging to the Rho family of proteins. Previously, we generated limb bud mesenchyme-specific Cdc42 inactivated mice (Cdc42 conditional knockout mice; Cdc42  fl/fl ; Prx1-Cre), which showed short limbs and cranial bone deformities, though the mechanism related to the cranium phenotype was unclear. In the present study, we investigated the role of Cdc42 in cranial bone development. Our results showed that loss of Cdc42 caused a defect of intramembranous ossification in cranial bone tissues which is related to decreased expressions of cranial suture morphogenesis genes, including Indian hedgehog (Ihh) and bone morphogenetic proteins (BMPs). These findings demonstrate that Cdc42 plays a crucial role in cranial osteogenesis, and is controlled by Ihh- and BMP-mediated signaling during cranium development., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Rac1 and Cdc42, Rho family low molecular weight G proteins, are intracellular signaling factors that transmit various information from outside to inside cells. Primarily, they are known to control various biological activities mediated by actin cytoskeleton reorganization, such as cell proliferation, differentiation, and apoptosis. In order to investigate the functions of Rac1 and Cdc42 in bone formation, we prepared cartilage-specific double conditional knockout mice, Rac1 fl/fl ; Cdc42 fl/fl ; Col2-Cre (Rac1: Cdc42 dcKO mice), which died just after birth, similar to Cdc42 fl/fl ; Col2-Cre mice (Cdc42 cKO mice). Our findings showed that the long tubule bone in Rac1: Cdc42 dcKO mice was shorter than that in Rac1 fl/fl ; Col2-Cre mice (Rac1 cKO mice) and Cdc42 cKO mice. Abnormal skeleton formation was also observed and disordered columnar formation in the growth plate of the Rac1: Cdc42 dcKO mice was more severe as compared to the Rac1 cKO and Cdc42 cKO mice. Together, these results suggest that Rac1 and Cdc42 have cooperating roles in regulation of bone development., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Osteoclasts are multinucleated giant cells differentiated from monocyte-macrophage-lineage cells under stimulation of receptor activator of nuclear factor κ-B (RANK) ligand (RANKL) produced by osteoblasts and osteocytes. Although it has been reported that nitric oxide (NO) and reactive oxygen species (ROS) are involved in this process, the mechanism by which these labile molecules promote osteoclast differentiation are not fully understood. In this study, we investigated the formation and function of 8-nitro-cGMP, a downstream molecule of NO and ROS, in the process of osteoclast differentiation in vitro. 8-Nitro-cGMP was detected in mouse bone marrow macrophages and osteoclasts differentiated from macrophages in the presence of RANKL. Inhibition of NO synthase suppressed the formation of 8-nitro-cGMP as well as RANKL-induced osteoclast differentiation from macrophages. On the other hand, RANKL-induced osteoclast differentiation was promoted by addition of 8-nitro-cGMP to the cultures. In addition, 8-nitro-cGMP enhanced the mRNA expression of RANK, the receptor for RANKL. However, 8-bromo-cGMP, a membrane-permeable derivative of cGMP, did not have an effect on either RANKL-induced osteoclast differentiation or expression of the RANK gene. These results suggest that 8-nitro-cGMP is a novel positive regulator of osteoclast differentiation, which might help to explain the roles of NO and ROS in osteoclast differentiation., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Recent studies have revealed that Toll-like receptors (TLRs) are highly expressed and activated in many types of cancer. Physiologically, TLR2 recognizes bacteria and other microorganisms in the oral cavity; however, the role of TLR2 in oral squamous cell carcinoma (OSCC) is unclear. In this study, we demonstrated that TLR2 is highly expressed in OSCC in comparison with adjacent non-malignant tissue. TLR2 was also expressed in OSCC-derived cell lines, and its expression was activated by ligands derived from bacteria and mycoplasma. Furthermore, to elucidate the mechanism of OSCC progression via TLR2 signal transduction, we focused on microRNAs (miRNAs) that are induced by TLR2 activation. Interestingly, ligand activation of TLR2 induced the expression of miR-146a and we found that downregulation of caspase recruitment domain-containing protein 10 (CARD10) mRNA in OSCC-derived cell lines. Moreover, knockdown of CARD10 induced resistance to cisplatin-induced apoptosis in OSCC cells. These findings suggest that the activation of TLR2 by bacterial components can enhance the progression of OSCC and may be implicated in acquired resistance to cisplatin-induced apoptosis through regulation of the miR-146a pathway., (Copyright © 2017. Published by Elsevier Inc.)

Nephronectin (Npnt), an extracellular matrix protein, is considered to play critical roles in development of various tissues and their functions. In basic science experiments, we found that interleukin-1β (IL-1β), well known to have an important role in inflammatory response, inhibited Npnt gene expression in MC3T3-E1 cells, a mouse osteoblastic cell line. The purpose of this study was to investigate mechanisms that govern the regulation of Npnt gene expression by IL-1β in osteoblasts., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Nephronectin (Npnt), an extracellular matrix protein, is considered to play critical roles as an adhesion molecule in the development and functions of various organs and tissues, such as the kidneys and bone. In the present study, we found that Wnt3a strongly enhanced Npnt mRNA expression in osteoblast-like MC3T3-E1 cells, while it also induced an increase in Npnt gene expression in both time- and dose-dependent manners via the Wnt/β-catenin signaling pathway. These results suggest novel mechanisms for Wnt3a-induced osteoblast proliferation and cell survival via Npnt gene expression., (Copyright © 2017 Elsevier Inc. All rights reserved.)

It is known that diabetes aggravates alveolar bone loss associated with periodontitis. While insulin depletion increases the blood concentration of ketone bodies, i.e., acetoacetate and β-hydroxybutyrate, their roles in bone metabolism have not been much studied until today. We investigated the effects of acetoacetate and β-hydroxybutyrate on mineralization of extracellular matrix in cultures of mouse osteoblastic MC3T3-E1 cells and primary mouse osteoblasts in the presence and absence of bone morphogenetic protein-2. Acetoacetate potentiated alkaline phosphatase activity in MC3T3-E1 cells in a concentration-dependent manner, ranging from physiological to pathological concentrations (0.05-5 mmol/L). In contrast, β-hydroxybutyrate lowered it in the same experimental settings. Mineralization in cultures of these cells was also up-regulated by acetoacetate and down-regulated by β-hydroxybutyrate. Similar results were obtained in cultures of mouse primary osteoblasts. Neither alkaline phosphatase mRNA nor its protein expression in MC3T3-E1 cells was affected by acetoacetate or β-hydroxybutyrate, indicating that these ketone bodies control the enzyme activity of alkaline phosphatase in osteoblasts and hence their mineralization bi-directionally. Finally, either gene silencing of monocarboxylate transporter-1, a major transmembrate transporter for ketone bodies, nullified the effects of ketone bodies on alkaline phosphatase activity in MC3T3-E1 cells. Collectively, we found that ketone bodies bidirectionally modulates osteoblast functions, which suggests that ketone bodies are important endogenous factors that regulate bone metabolism in both physiological and pathological situations., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Bropirimine is a synthetic agonist for toll-like receptor 7 (TLR7). In this study, we investigated the effects of bropirimine on differentiation and bone-resorbing activity of osteoclasts in vitro. Bropirimine inhibited osteoclast differentiation of mouse bone marrow-derived macrophages (BMMs) induced by receptor activator of nuclear factor κB ligand (RANKL) in a concentration-dependent manner. Furthermore, it suppressed the mRNA expression of nuclear factor of activated T-cells, cytoplasmic, calcineurin-dependent 1 (NFATc1), a master transcription factor for osteoclast differentiation, without affecting BMM viability. Bropirimine also inhibited osteoclast differentiation induced in co-cultures of mouse bone marrow cells (BMCs) and mouse osteoblastic UAMS-32 cells in the presence of activated vitamin D3. Bropirimine partially suppressed the expression of RANKL mRNA in UAMS-32 cells induced by activated vitamin D3. Finally, the anti-interferon-β (IFN-β) antibody restored RANKL-dependent differentiation of BMMs into osteoclasts suppressed by bropirimine. These results suggest that bropirimine inhibits differentiation of osteoclast precursor cells into osteoclasts via TLR7-mediated production of IFN-β., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Objectives: The aim of this study was to establish a simple method for the early detection of bisphosphonate-related osteonecrosis of the jaw (BRONJ) using computed tomography (CT)., Materials and Methods: CT images of the mandible were obtained from a total of 20 patients with BRONJ and 20 control subjects. BRONJ was classified into 2 groups, with bone exposure (Stage 1-3 BRONJ) or without (Stage 0 BRONJ). In each patient, 15 transaxial CT images were selected and 30 configured regions of interest (ROI) were identified. The ANOVA test was applied to test the relationship between the severity of systemic risk factors., Results: Regarding the local status of the mandible, significant differences were observed among the Stage 0 BRONJ, Stage 1-3 BRONJ, non-BRONJ and control groups in the cancellous bone CT radiodensity values, but there were no significant differences between the Stage 0 and Stage 1-3 BRONJ groups. In the cortical bone widths, significant differences were observed only between BRONJ and the controls., Conclusions: Measuring cancellous bone CT radiodensity value has the potential to be a simple and quantitative method to detect the early stages of BRONJ., (Copyright © 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.)

The purpose of this study was to evaluate tray fit and bone quality of particulate cancellous bone and marrow (PCBM) mandibular reconstruction using custom-made bioresorbable forged composites of a raw particulate hydroxyapatite/poly-L-lactide (HA/PLLA) tray in a dog model. Mesh sheets of HA/PLLA were formed in a tray shape according to the mandible stereolithographs of 14 beagle dogs. Platelet-rich plasma (PRP) was obtained from venous blood, and PCBM was harvested from the iliac crest. Bone defects were made bilaterally on the lower borders of the mandible. The PCBM and PRP were mixed and compressed into the defects and a custom-made HA/PLLA or a manually adopted titanium tray was fixed by screws. Tray fit and bone qualities were evaluated using computed tomography, microfocus computed tomography and confocal laser scanning microscopy. In buccal side, there is no significant difference with tray fit between the HA/PLLA and the titanium type, but in lingual side, it was better in the HA/PLLA type than that of the Ti type. Bone volume fraction (BV/TV) had markedly increased on the HA/PLLA side at 12 months. In conclusion, the custom-made HA/PLLA tray was easily and accurately adapted to the mandible, and had achieved sufficient bone quality by 12 months., (Copyright © 2012 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.)

Introduction: Hepatocellular carcinoma (HCC) is a common neoplasm worldwide, with more than half of the tumors associated with regional metastasis. Extrahepatic metastasis is also common, and the most frequently affected sites are the lungs, abdominal lymph nodes, diaphragm, and bone. However, HCC metastasis to the mandible is rare, with approximately 50 cases reported in the literature., Methods: In this report, we describe a case of HCC metastasis to the mandible at the apex of #18 root in a 62-year-old man. This patient had already been diagnosed with metastasis to pancreatic caput lymph node. The radiographic features of the mandible resembled radicular cyst and did not show typical findings of malignancy., Results: Under the first diagnosis of radicular cyst, root canal treatment was initially performed, and then surgical treatment of the removal of the cystic lesion and #18 extraction were performed. Finally, the lesion was diagnosed as HCC metastasis from pathological examination. Consequently, he received constitutional chemotherapy in the hepatitis unit and is now in remission., Conclusion: This case shows the importance of considering the differential diagnosis of malignancy., (Copyright 2010 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Tumor-induced osteomalacia (TIO) is a rare acquired paraneoplastic disease characterized by renal phosphate wasting and hypophosphatemia. Recently, it was reported that tumors associated with TIO produce fibroblast growth factor (FGF) 23, identified as the last member of the FGF family and of which excessive action causes several hypophosphatemic diseases whereas deficient FGF23 activity results in hyperphosphatemic tumoral calcinosis. In this case, although it was difficult to locate the associated tumor, an abnormal mass in the left maxilla was detected by imaging. The tumor was removed by partial resection of the left maxillary alveolar region. Thereafter, serum level of FGF23 rapidly decreased, hypophosphatemia improved, and the clinical symptoms greatly improved. Histopathologic diagnosis of the tumor was phosphaturic mesenchymal tumor, mixed connective tissue variant. Immunohistochemical findings confirmed that the removed tumor produced FGF23. These results indicate that development of osteomalacia in this patient was related to the maxillary tumor, which overexpressed FGF23., (Copyright 2010 Mosby, Inc. All rights reserved.)

This study reports on 15 mandibular reconstructions using the Dumbach Titan Mesh-System and particulate cancellous bone and marrow harvested from bilateral posterior ilia. All cases showed segmental defects. Eleven cases involved patients with malignant tumor. Six patients had received irradiation of 40-50 Gy. Reconstructions were performed immediately in 1 patient and secondarily in the remaining 14 patients. In 13 cases, mandibles were successfully reconstructed. Of these 13 patients, 9 reconstructions were completed without complications, whereas the other 4 cases showed complications. In 2 cases, reconstruction failed completely. Overall success rate was 87%. Statistical analysis revealed the extent of mandibular defect, but not malignancy of the original disease or radiotherapy of

Basic fibroblast growth factor (bFGF) induced osteoclast formation in co-cultures of mouse spleen cells and osteoblasts. Osteoclastogenesis inhibitory factor (OCIF) and a selective cyclooxygenase-2 (COX-2) inhibitor, NS-398, abolished bFGF-induced osteoclast formation. bFGF did not affect spleen cells, but it did affect osteoblasts, to stimulate osteoclast formation. Northern blot analysis revealed that bFGF up-regulated the expression of osteoclast differentiation factor (ODF) and COX-2 and down-regulated the expression of OCIF in primary osteoblastic cells. NS-398 abolished the increase of ODF mRNA, but it had no effect on the decrease of OCIF mRNA. NS-398 suppressed the binding of (125)I-labeled OCIF to osteoblastic cells treated with bFGF. Enzyme-linked immunosorbent assay showed that bFGF inhibited OCIF production by osteoblastic cells, and the inhibition was not affected by NS-398. We conclude that bFGF induces osteoclast formation by stimulating ODF production through COX-2-mediated prostaglandin synthesis and by suppressing OCIF production through a mechanism independent of prostaglandin synthesis., (Copyright 1999 Academic Press.)