A Tumor Suppressor Gene Product, Platelet-Derived Growth Factor Receptor-Like Protein Controls Chondrocyte Proliferation and Differentiation.

The platelet-derived growth factor receptor-like (PDGFRL) gene is regarded as a tumor suppressor gene. However, nothing is known about the molecular function of PDGFRL. In this study, we initially clarified its function in chondrocytes. Among all cell lines examined, the PDGFRL mRNA level was the highest in chondrocytic HCS-2/8 cells. Interestingly, the proliferation of chondrocytic HCS-2/8 cells was promoted by PDGFRL overexpression, whereas that of the breast cancer-derived MDA-MB-231 cells was inhibited. Of note, in PDGFRL-overexpressing HCS-2/8 cells, the expression of chondrocyte differentiation marker genes, SOX9, ACAN, COL2A1, COL10A1, and ALP, was decreased. Moreover, we confirmed the expression of PDGFRL mRNA in normal cartilage tissue and chondrocytes. Eventually, the expression of PDGFRL mRNA in condrocytes except in the case of hypertrophic chondrocytes was demonstrated in vivo and in vitro. These findings suggest that PDGFRL plays the different roles, depending upon cell types. Particularly, in chondrocytes, PDGFRL may play a new and important role which is distinct from the function previously reported. J. Cell. Biochem. 118: 4033-4044, 2017. © 2017 Wiley Periodicals, Inc.

Stress distribution prevents ischaemia and bone resorption in residual ridge.

OBJECTIVE: Intensive mechanical stress and/or inflammation are known to induce alveolar bone resorption. This study investigated whether a distribution of mechanical stress would reduce residual ridge resorption or improve ischaemia. DESIGN: Thirty rats were divided into six experimental groups (n=5). The control group received no intentional stimulation, but rats in the experimental groups wore denture stimulators made of acrylic resin or a soft lining material. The stimulator transmitted masticatory pressure to the rats' palates for four weeks. The four types of soft lining materials investigated in this study dispersed the applied pressure, with compressive stress ranging from 20.8 to 90.8kPa. Volumes of blood flow and bone resorption of denture foundations were measured every week for 4 weeks. Statistical evaluation of these results was performed using two-way ANOVA and Holm-Sidak test within 5% error limits. RESULTS: Non-viscoelastic material clearly induced bone resorption and ischaemia of denture foundations, while viscoelastic materials reduced these phenomena to different extents according to their viscoelastic properties. Ischaemia in the alveolar ridge preceded residual ridge resorption, because the amount of residual ridge resorption and blood flow rate showed a simple linear regression. CONCLUSION: Animal model of this study suggested that a distribution or reduction of mechanical stress could improve blood flow and decrease alveolar ridge resorption.

Distribution, gene expression, and functional role of EphA4 during ossification.

EphA4 receptor tyrosine kinase has been shown to be critically involved in neural tissue development. Here, we found EphA4 was also distributed among hypertrophic chondrocytes and osteoblasts in the growth plate of developing mouse long bones. In vitro evaluation revealed that ephA4 expression was elevated upon hypertrophic differentiation of chondrocytes and that markedly stronger expression was observed in osteoblastic SaOS-2 than chondrocytic HCS-2/8 cells. Of note, RNAi-mediated silencing of ephA4 in SaOS-2 cells resulted in the repression of osteocalcin gene expression and alkaline phosphatase activity. Interestingly, confocal laser-scanning microscopic analysis revealed the presence of EphA4 molecules in the nucleus as well as on the surface of SaOS-2 cells. These findings are the first indication of a critical role of EphA4 in ossification, especially at the final stage in which osteoblasts and hypertrophic chondrocytes play major roles.

Ultrasonic cleaning of silica-coated zirconia influences bond strength between zirconia and resin luting material.

The purpose of this study was to evaluate how ultrasonic cleaning of silica-coated zirconia surfaces would influence the latter's bond strength to resin luting material. Forty zirconia specimens were divided into four groups: one air abrasion group and three silica-coated groups. Silica-coated specimens were cleaned with distilled water using an ultrasonic cleaner after tribochemical silica coating and then divided into three groups according to cleaning durations: 1 minute, 5 minutes, or without cleaning. Following which, resin luting material was polymerized against the specimens. After storage in water for 24 hours, the specimens were subjected to shear bond strength test. Shear bond strength of silica-coated group without cleaning was significantly higher than the other three groups, but there were no statistically significant differences among the three latter groups. SEM images suggested visible differences among the treatment methods. With EDXS analysis, it was revealed that ultrasonic cleaning decreased the silica content on the treated surfaces. Therefore, results showed that ultrasonic cleaning of tribochemically silica-coated zirconia surfaces decreased the adhesion efficacy to resin luting material.

Gene expression and distribution of connective tissue growth factor (CCN2/CTGF) during secondary ossification center formation.

CCN2/connective tissue growth factor (CCN2/CTGF) is a critical signaling modulator of mesenchymal tissue development. This study investigated the localization and expression of CCN2/CTGF as a factor supporting angiogenesis and chondrogenesis during development of secondary ossification centers in the mouse tibial epiphysis. Formation of the secondary ossification center was initiated by cartilage canal formation and blood vessel invasion at 7 days of age, and onset of ossification was observed at 14 days. In situ hybridization showed that CCN2/CTGF mRNA was distinctively expressed in the region of the cartilage canal and capsule-attached marginal tissues at 7 days of age, and distinct expression was also observed in proliferating chondrocytes around the marrow space at 14 days of age. Immunostaining showed that CCN2/CTGF was distributed broadly around the expressed cells located in the central region of the epiphysis, where the chondrocytes become hypertrophic and the cartilage canal enters into the hypertrophic mass. Furthermore, an overlapping distribution of metalloproteinase (MMP)9 and CCN2/CTGF was found in the secondary ossification center. These findings suggest that the CCN2/CTGF is involved in establishing epiphyseal vascularization and remodeling, which eventually determines the secondary ossification center in the developing epiphysial cartilage.

Tensile bond strength between custom tray and elastomeric impression material.

The aim of this study was to investigate how to achieve sufficient and stable adhesive strength between impression material and tray. Impression materials were molded between autopolymerizing resin columns, and tensile strength was measured as a function of these factors: tray storage time (1, 2, 4, 7, and 10 days), adhesive drying time (0, 1, 5, 10, and 15 minutes), and tray surface roughness (air abrasion, bur-produced roughness, and no treatment). Tensile bond strength was not affected by tray storage time throughout the entire evaluation period of 10 days. As for tray adhesive drying time, Reprosil and Exaimplant yielded extremely low values for drying times of 10 minutes or less (P<0.05), while Imprint II and Impregum were not influenced by drying time. Vinyl polysiloxane achieved the highest adhesive strength with bur-produced roughness, which was significantly higher than with air abrasion or no treatment (P<0.05), whereas polyether achieved the lowest value with bur-produced roughness (P<0.05). It was concluded that surface treatment of custom tray should be adapted to the type of impression material used to achieve optimum bond strength.

Possible role of LRP1, a CCN2 receptor, in chondrocytes.

Low density lipoprotein receptor (LDLR)-related protein 1 (LRP1/CD91) is one of the receptors of CCN2 that conducts endochondral ossification and cartilage repair. LRP1 is a well-known endocytic receptor, but its distribution among chondrocytes remains to be elucidated. We herein demonstrate for the first time that the distribution of LRP1 in chondrocytes except for hypertrophic chondrocytes in vivo and in vitro. Interestingly, the LRP1 levels were higher in mature chondrocytic HCS-2/8 and osteoblastic SaOS-2 than in other cells, whereas the other LDLR family members involved in ossification were detected at lower levels in HCS-2/8. It was interesting to note that in HCS-2/8, LRP1 was observed not only on the cell surface and in the cytoplasm, but also in the nucleus. Exogenously added CCN2 was incorporated into HCS-2/8, which was partially co-localized with LRP1, and targeted to the recycling endosomes and nucleus as well as the lysosomes. These findings suggest specific roles of LRP1 in cartilage biology.

Modified direct relining method produces an accurate adaptation of denture.

The purpose of this study was to examine if a modified direct relining method could result in excellent denture adaptation compared to a conventional method. Direct relining was done using heat-polymerized acrylic resin base on a maxillary cast with two times of three seconds of cooling using dichloro-difluoro-methane coolant. Discrepancy between cast and intaglio surface at residual ridge and center of palate was measured at 12 minutes after mixing of resin (Time 0) and at 24 hours or seven days after water immersion (36 degrees C). At Time 0 (with three seconds of cooling), the discrepancy at ridge (0.39 +/- 0.27) and palate (0.66 +/- 0.31) was significantly lower compared to that of control (ridge = 0.93 +/- 0.51; palate = 1.14 +/- 0.13, P < 0.05); and the same observations occurred at 24 hours and seven days too. On intaglio side (with three seconds of cooling), the peak temperature was 5 degrees C lower than that of control and it occurred at a delay of about 60 seconds. Based on the results of this study, we therefore suggested that this delayed and lowered temperature served to improve the adaptability of denture base.

Collaborative action of M-CSF and CTGF/CCN2 in articular chondrocytes: possible regenerative roles in articular cartilage metabolism.

It is known that expression of the macrophage colony-stimulating factor (M-CSF) gene is induced in articular chondrocytes upon inflammation. However, the functional role of M-CSF in cartilage has been unclear. In this study, we describe possible roles of M-CSF in the protection and maintenance of the articular cartilage based on the results of experiments using human chondrocytic cells and rat primary chondrocytes. Connective tissue growth factor (CTGF/CCN2) is known to be a potent molecule to regenerate damaged cartilage by promoting the growth and differentiation of articular chondrocytes. Here, we uncovered the fact that M-CSF induced the mRNA expression of the ctgf/ccn2 gene in those cells. Enhanced production of CTGF/CCN2 protein by M-CSF was also confirmed. Furthermore, M-CSF could autoactivate the m-csf gene, forming a positive feed-back network to amplify and prolong the observed effects. Finally, promotion of proteoglycan synthesis was observed by the addition of M-CSF. These findings taken together indicate novel roles of M-CSF in articular cartilage metabolism in collaboration with CTGF/CCN2, particularly during an inflammatory response. Such roles of M-CSF were further supported by the distribution of M-CSF producing chondrocytes in experimentally induced rat osteoarthritis cartilage in vivo.

Investigation of preferred viscosity of irreversible hydrocolloid on preliminary impression for edentulism.

This study aims to investigate the preferred viscosity of irreversible hydrocolloid used in the preliminary impression for edentulism. Thirteen modalities of irreversible hydrocolloid were prepared by changing the W/P ratio. Discrimination test for the preferred viscosity was performed on 11 prosthodontists (10.4+/-5.3 years of prosthetic experience). The parameter of discrimination test (P%) was calculated as the ratio of the number of adequate tests to the total number of tests. The P% and apparent viscosity coefficient (eta a) values measured by rheometer demonstrated good correlation (Y = -35.8X2 + 118.4X - 22.8, r=0.86, p<0.01). Prosthodontists could judge the preferred viscosity based on their clinical experiences. On the preliminary impression for edentulism, the preferred viscosity demonstrated in vitro using a polyurethane maxilla model was 1.21 x 10(3) Pa x s.

Does plasma irradiation improve shear bond strength of acrylic resin to cobalt-chromium alloy?

OBJECTIVES: Plasma treatment leads to surface modification such as the improved wettability of dental materials. Studies have suggested that plasma treatment may bring about an improvement in the shear bond strength between cobalt-chromium alloy and self-curing acrylic resin. METHODS: Forty-eight cobalt-chromium alloy specimens were randomly divided into four groups (each of the groups consisted of 12 specimens); air abrasion, adhesive primer, adhesive primer after air abrasion, or after plasma irradiation. A self-curing acrylic resin, 2 mm thick and 3.6 mm in diameter, was processed on all specimens before storage in distilled water at 37 degrees C for 24 h. Shear bond strength values were determined at a crosshead speed of 0.5 mm/min. Data was statistically analyzed using Scheffé's test. RESULTS: Adhesive primer clearly increased the shear bond strength compared with air abrasion (p < 0.05). The synergy of air abrasion and adhesive primer greatly increased the shear bond strength, showing a five-fold increase over air abrasion, or one and a half-fold over adhesive primer. A similar tendency in increase was observed in the adhesive primer after plasma treatment, but to a lower degree. Adhesive primer after plasma treatment showed half the shear bond strength of the treatment of adhesive primer after air abrasion (p < 0.05). Moreover, adhesive primer after plasma treatment showed a lower shear bond strength than adhesive primer alone although the difference was not statistically significant. SIGNIFICANCE: Plasma treatment does not improve adhesion between cobalt-chromium alloy and self-curing acrylic resin.

Effect of plasma treatment on adhesion of self-curing repair resin to acrylic denture base.

Plasma irradiation on surface of heat-cured acrylic resin prior to processing self-curing acrylic resin is likely to effectively increase the adhesive strength between these materials for short-term period. However, long-term reliability of adhesive strength between these materials has not been clarified yet. In the present study, these materials were stored in water for a long period (100 days), and the effect on their shear bond strength was investigated. Forty-four test specimens with flat bonding test surface were made with heat-cured acrylic resin. They were divided into four groups according to treatment procedures for bonding surface: plasma treatment, adhesive primer application, adhesive primer application after plasma treatment, and no treatment (for control). Self-curing acrylic resin was processed against all bonding surfaces. After storage in water for 100 days, shear bond strength values between heat-cured and self-cured acrylic resins were measured. Specimens in plasma treatment group exhibited higher shear bond strength value than those in control, although the difference was not significant.