Sahara N.,Matsumoto Dental University
Anatomical Record | Year: 2014
The horse is a grazing herbivore whose cheek teeth are hypsodon; that is, they possess long crowns that are completely covered by coronal cement at eruption. For elucidation of the sequential events in the formation of this coronal cementum in the mandibular horse cheek teeth, in the present study the lower 3rd permanent premolar teeth (PM4) from 3.5-, 4-, and 5-year-old horses were compared by using radiography, microcomputed tomography (Miro-CT), light microscopy (LM), and scanning electron microscopy (SEM). The present study clearly showed that prior to coronal cementogenesis tartrate-resistant acid phosphatase (TRAP)-positive odontoclasts resorbed on the enamel surface of the reserve crown in horse cheek tooth. Enamel resorption areas were relatively narrow, and started from the cuspal tips, and moved in the apical direction during tooth development. A primary cementum was initially deposited on the irregularly pitted enamel-cementum junction (ECJ) of the infolding and peripheral enamel. The infolding cementum filled grooves completely by the time of tooth eruption. On the other hand, in the peripheral cementum, the secondary and tertiary cementum layers were sequentially deposited on the primary cementum. These two cementum layers were sites for the insertion of the periodontal ligaments, and were continually laid down on the primary cementum coronally rather than apically throughout the life. The results of the present study suggest that the coronal cementum of horse cheek teeth is a multistructural and multifunctional tissue, meeting the requirements of its many different functions. Anat Rec, 297:716-730, 2014. © 2014 Wiley Periodicals, Inc.
Kobayashi Y.,Matsumoto Dental University
Clinical calcium | Year: 2012
Wnts, palmitoylated and glycosylated molecules play a central role in the early development of organs and tissues. Wnts bind to receptor complexes of frizzled and low density lipoprotein-related protein 5/6, which in turn, activate theβ-catenin-dependent canonical pathway. Wnt5a, a typical non-canonical ligand, activates theβ-catenin-independent noncanonical pathways such as the Wnt/Ca pathway and the Wnt/planar cell polarity pathway. Recent studies have established that Wnt-mediated signals are crucial for bone formation and resorption. This review summarizes the current knowledge of the roles of Wnt signaling in bone formation and resorption.
Taguchi A.,Matsumoto Dental University
Oral Diseases | Year: 2010
Oral Diseases (2010) 16, 316-327 Many patients with osteoporosis go undiagnosed because typically no symptoms are present before a fracture. Triage screening to refer patients to appropriate medical professionals for further investigation would be useful to address the increase in the incidence of osteoporotic fractures. Dental clinics may offer a new triage screening pathway because dentists frequently take radiographs of bones in the course of dental treatment. A major premise for such triage screening in dental clinics is that dentists can readily use a screening tool in their dental practice. For example, cortical width and shape of the mandible detected on panoramic radiographs may be appropriate indices for triaging individuals with osteoporosis. To date, several investigators have demonstrated significant associations between cortical indices on panoramic radiographs and bone mineral density of the skeleton generally, such as the spine and femur, biochemical markers of bone turnover and risk of osteoporotic fractures. Further, in two recent Japanese clinical trials, approximately 95% of women who were identified by trained dentists in their clinics using cortical shape findings did have osteopenia or osteoporosis. These findings support the possibility that dental clinics may offer a new triage platform to identify individuals with otherwise undetected osteoporosis. © 2009 John Wiley & Sons A/S.
Yamazoe M.,Matsumoto Dental University
Dental Materials Journal | Year: 2010
Metal ions released in 1% lactic acid solution from combinations of titanium fixtures with superstructures made of dental precious metal alloys (dental alloys) and titanium and differences based on the fixing method were investigated. In combinations of titanium with dental alloys, the level of Ti release was influenced by micro-structure of titanium: it was lower when the grain size was smaller. In titanium-titanium combinations, differences in the micro-structure of metal also markedly influenced the dissolution: the level of release increased when the micro-structure of titanium was different. The Ti and V release levels were higher in combination with titanium alloy and titanium than with titanium alloy and dental alloys. Regarding the superstructure-fixture fixing method, the level of Ti release was significantly lower in cement than in direct fixation.
Nakamura M.,Matsumoto Dental University
Clinical calcium | Year: 2014
Osteoclasts, the multinucleated cells that resorb bone, originate from monocyte-macrophage lineage cells. Various hormones, cytokines and growth factors are involved in osteoclastogenesis, via interaction with osteoblasts. In this review, we summarize the regulatory mechanism of bone resorption by various cytokines derived from osteoblasts and hematopoietic inflammatory cells.
Takahashi N.,Matsumoto Dental University
Advances in Experimental Medicine and Biology | Year: 2010
How are sites suitable for osteoclastogenesis determined? We addressed this issue using in vivo and in vitro experimental systems. We first examined the formation of osteoclasts in ectopic bone induced by BMP-2. When collagen disks which contained BMP-2 BMP-2-disks) or vehicle control-disks) were implanted into wild-type mice osteoclasts and osteoblasts appeared in the BMP-2-disks but not in the control disks. RANKL-deficient RANKL-/-) mice exhibited osteopetrosis with an absence of osteoclasts. BMP-2 and control disks were implanted into RANKL-/- mice which were intraperitoneally injected with RANKL. Osteoclasts formed in the BMP-2-disks but not in the control disks. In the BMP-2-disks osteoclasts were observed in the vicinity of osteoblasts. Cell cycle-arrested quiescent osteoclast precursors QOP) were identified as the committed osteoclast precursors in vitro. Experiments in vivo showed that QOPs survived for several weeks and differentiated into osteoclasts in response to M-CSF and RANKL. QOPs were identified as RANK and c-Fms double-positive cells and detected along bone surfaces in the vicinity of osteoblasts in RANKL-/- mice. QOPs were also observed in the ectopic bone induced by BMP-2 implanted into RANKL -/- mice suggesting that QOPs were circulating. These results imply that osteoblasts support the homing of QOPs to bone tissues. In response to bone-resorbing stimuli QOPs promptly differentiate into osteoclasts. Therefore the distribution of QOPs appears to determine the correct site of osteoclastic development. © 2010 Springer Science+Business Media LLC.
Hiraga T.,Matsumoto Dental University |
Ito S.,Shinshu University |
Nakamura H.,Matsumoto Dental University
Cancer Research | Year: 2013
CD44, an adhesion molecule that binds to the extracellular matrix, primarily to hyaluronan (HA), has been implicated in cancer cell migration, invasion, and metastasis. CD44 has also recently been recognized as a marker for stem cells of several types of cancer. However, the roles of CD44 in the development of bone metastasis are unclear. Here, we addressed this issue by using bone metastatic cancer cell lines, in which CD44 was stably knocked down. Tumor sphere formation and cell migration and invasion were significantly inhibited by CD44 knockdown. Furthermore, the downregulation of CD44 markedly suppressed tumorigenicity and bone metastases in nude mice. Of note, the number of osteoclasts decreased in the bone metastases. Microarray analysis revealed that the expression of HA synthase 2 was downregulated in CD44-knockdown cells. The localization of HA in the bone metastatic tumors was also markedly reduced. We then examined the roles of CD44-HA interaction in bone metastasis using 4-methylumbelliferone (4-MU), an inhibitor ofHAsynthesis. 4-MU decreased tumor sphere and osteoclast-like cell formation in vitro. Moreover, 4-MU inhibited bone metastases in vivo with reduced number of osteoclasts. These results collectively suggest that CD44 expression in cancer cells promotes bone metastases by enhancing tumorigenicity, cell migration and invasion, and HA production. Our results also suggest the possible involvement of CD44-expressing cancer stem cells in the development of bone metastases through interaction with HA. CD44-HA interaction could be a potential target for therapeutic intervention for bone metastases. © 2013 American Association for Cancer Research.
Matsumoto Dental University and Hi Lex Corporation | Date: 2012-10-15
An object of the present invention is to provide an implant structure assuring that substances accelerating breeding of bacteria are hard to be induced. The implant structure comprises: an artificial tooth root including an artificial tooth root main body having a distal end portion and a proximal end portion and a thread being formed at least on the distal end portion side and an induction portion for inducing a soft tissue provided on an outer periphery of the proximal end portion of the artificial tooth root main body; and a support base having a covering portion at the proximal end portion side of the support base covering the whole surface of the proximal end portion side of the induction portion, wherein the support base is provided with a step portion along its outer periphery from the covering portion toward a distal end side of the support base.
Takahashi N.,Matsumoto Dental University
Journal of Steroid Biochemistry and Molecular Biology | Year: 2013
Bone-resorbing osteoclasts differentiate from hematopoietic precursors under the strict regulation of bone-forming osteoblasts. Osteoblasts express two cytokines essentially required for osteoclastogenesis; macrophage-colony stimulating factor (M-CSF) and receptor activator of nuclear factor κB ligand (RANKL). Osteoblasts express constitutively M-CSF, and inducibly RANKL in response to bone resorptionstimulating factors. The active form of vitamin D3, 1α,25-dihydroxyvitamin D3 [1α,25(OH) 2D3], is known to be a hormone which enhances RANKL expression in vitro. Nevertheless, Calcitoriol [1α,25(OH) 2D3] and its prodrug, Alfacalcidol (1α- hydroxyvitamin D3) have been taken as therapeutic drugs in osteoporotic patients in Japan. In addition, Eldecalcitol [2β-(3- hydroxypropoxy)-1α,25(OH)2D3], a new analog of 1α,25(OH)2D3, was approved as a therapeutic agent for osteoporosis in Japan in 2011. Interestingly, those vitamin D compounds increased bone mineral density due to the suppression of bone resorption in vivo. We previously showed that cycle-arrested quiescent osteoclast precursors (QOPs) were the direct osteoclasts precursors in vivo. We then investigated effects of daily administration of Eldecalcitol on bone resorption in mice. Bone mineral density was increased through the suppression of RANKL expression in osteoblasts in mice treated with Eldecalcito. The number of QOPs remained unchanged in bone. These results suggest that a long-term exposure of osteoblasts to vitamin D compounds down-regulate RANKL expression. © 2012 Elsevier Ltd. All rights reserved.
Harada S.,Matsumoto Dental University
Clinical calcium | Year: 2011
Differentiation and function of osteoclasts is regulated by RANKL and OPG, both of which are produced by osteoblasts. Osteoclast precursors express RANK, the receptor of RANKL. The activation of the RANKL-RANK system stimulates osteoclast differentiation and function. OPG is a decoy receptor of RANKL, which inhibits the RANKL-RANK interaction. Several genetic disorders in RANKL, RANK and OPG genes cause osteoclast abnormalities. Therefore, the development of anti-osteoporosis drugs that suppress the RANKL-RANK system is advanced now. Recently, anti-RANKL antibody, denosumab, is developed and being used as a new treatment for osteoporosis.