Kazuro Satoh

Mechanical properties of several nickel-titanium alloy wires in three-point bending tests

The purpose of this study was to clarify the mechanical properties of 42 brands of nickel-titanium alloy orthodontic wires from 9 manufacturers by conducting three-point bending tests under uniform testing conditions. Manufacturers included A-Company, Hoya Medical, Lancer, Ormco, Rocky Mountain, Sankin, Tomy (GAC), TP, and 3M/Unitek. Cobalt-chrome, and titanium-molybdenum alloy wires were also tested as a reference for comparison of force levels. All reported data were recorded during the unloading process to simulate the force that a wire exerts on a tooth as it is moved into the dental arch from a position of malocclusion. The following results were obtained for the nickel-titanium wires tested. (1) Among the 0.016 inch round wires tested under a maximum deflection of 1.5 mm, the difference between the smallest (Copper nickel-titanium 35) and the largest (Aline) load values was 136 g. For the 0.016 x 0.022 inch rectangular wires tested, the difference between the smallest (Copper nickel-titanium 40) and the largest (Aline) load values was 337 g. (2) The change in load between 1.5 and 0.5 mm of deflection was examined to clarify the superelastic properties of the wires tested. For the 0.016 inch wires, 17 wire brands produced a load difference of less than 100 g, and two brands produced a difference of at least 100 g (Aline and Titanal = 100 g). For the 0.016 x 0.022 inch wires, 15 brands produced a load difference of less than 100 g, and eight brands produced a difference of over 100 g. The smallest and largest load differences were 3 g (Copper nickel-titanium 35) and 200 g (Aline). (3) The majority of the samples with a smaller load difference between deflections of 1.5 mm and 0.5 mm in the unloading process were found among super-elastic wires, while samples with a larger load difference were predominantly found among work-hardened wires. Compared with cobalt-chrome and TMA wires, nickel-titanium alloy wires exert significantly less force. However, the amount of force varies greatly from brand to brand. Consequently, when using nickel-titanium alloy wires, brands must be selected carefully by taking into consideration the severity of the malocclusion and the stage of orthodontic treatment in each case. It is the intent of this study to offer clinicians an unbiased guide for the selection of appropriate nickel-titanium alloy wires.

SCRG1 suppresses LPS-induced CCL22 production through ERK1/2 activation in mouse macrophage Raw264.7 cells

Recently, we identified the scrapie responsive gene 1 (SCRG1) secreted from mesenchymal stem cells (MSCs) and its receptor bone marrow stromal cell antigen 1 (BST1) as positive regulators of stem cell qualities such as self-renewal, migration abilities, and osteogenic differentiation potential. Here, we examined the effect of the paracrine activity of SCRG1 in macrophages. The mouse macrophage-like cell line Raw264.7 expressed BST1/β1 or BST1/β2 integrin as possible SCRG1 receptors. Unexpectedly, recombinant SCRG1 did not enhance cell proliferation, migration, or adhesion in these macrophages. However, further examination of the effect of SCRG1 in Raw264.7 cells did reveal a potent anti-inflammatory effect whereby SCRG1 suppressed LPS-induced CCL22 production. SCRG1 also induced the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) in these cells and, moreover, a mitogen-activated protein kinase (MAPK)/ERK kinase inhibitor U0126 significantly suppressed the effect of SCRG1 on LPS-induced chemokine CCL22 production. Taken together, these data indicate that SCRG1 signals through the MAPK pathway and suppresses the LPS signaling pathway. CCL22 is generally known to be chemotactic for monocytes, dendritic cells, natural killer cells and chronically activated T lymphocytes, suggesting that MSC-derived SCRG1 may block infiltration of these cells. A mechanism is proposed by which MSCs play their immunosuppressive role through suppressing chemokine expression in monocyte/macrophage lineage cells.

Establishment of immortalized mesenchymal stem cells derived from the submandibular glands of tdTomato transgenic mice

Transgenic mice that overexpress the red fluorescent protein tdTomato (tdTomato mice) are well suited for use in regenerative medicine studies. Cultured cells from this murine model exhibit strong red fluorescence, enabling real-time in vivo imaging through the body surface of grafted animals. Mesenchymal stem cells (MSCs) have marked potential for use in cell therapy and regenerative medicine; however, the mechanisms that regulate their dynamics in vivo are poorly understood. In the present study, an MSC line was derived from the submandibular gland fibroblasts of tdTomato mice. The fluorescent signal from this cell line was observed in organs throughout the body, as well as in salivary glands. Primary culture cells derived from the submandibular gland were immortalized with SV40 large T antigen (GManSV cells); these cells exhibited increased migratory ability, as compared with those isolated from the sublingual gland. GManSV cells were tdTomato-positive and exhibited spindle-shaped fibroblastic morphology; they also robustly expressed mouse MSC markers: Stem cell antigen-1 (Sca-1), CD44, and CD90. This cell line retained multipotent stem cell characteristics, as evidenced by its ability to differentiate into both osteogenic and adipogenic lineages. These results indicate that Sca-1+/CD44+/CD90+-GManSV cells may be useful for kinetic studies of submandibular gland-derived MSCs in the context of in vitro co-culture with other types of salivary gland-derived cells. These cells may also be used for in vivo imaging studies, in order to identify novel cell therapy and regenerative medicine for the treatment of salivary gland diseases.

ROCK/actin/MRTF signaling promotes the fibrogenic phenotype of fibroblast-like synoviocytes derived from the temporomandibular joint

Malocclusion caused by abnormal jaw development or muscle overuse during mastication results in abnormal mechanical stress to the tissues surrounding the temporomandibular joint (TMJ). Excessive mechanical stress against soft and hard tissues around the TMJ is involved in the pathogenesis of inflammatory diseases, including osteoarthritis (OA). OA-related fibrosis is a possible cause of joint stiffness in OA. However, cellular and molecular mechanisms underlying fibrosis around the TMJ remain to be clarified. Here, we established a cell line of fibroblast-like synoviocytes (FLSs) derived from the mouse TMJ. Then, we examined whether the Rho-associated coiled-coil forming kinase (ROCK)/actin/myocardin-related transcription factor (MRTF) gene regulatory axis positively regulates the myofibroblast (MF) differentiation status of FLSs. We found that i) FLSs extensively expressed the MF markers α-smooth muscle actin (α-SMA) and type I collagen; and ii) an inhibitor against the actin-polymerizing agent ROCK, Y-27632; iii) an actin-depolymerizing agent cytochalasin B; iv) an inhibitor of the MRTF/serum response factor-regulated transcription, CCG-100602, clearly suppressed the mRNA levels of α-SMA and type I collagen in FLSs; and v) an MF differentiation attenuator fibroblast growth factor-1 suppressed filamentous actin formation and clearly suppressed the mRNA levels of α-SMA and type I collagen in FLSs. These results strongly suggest that the ROCK/actin/MRTF axis promotes the fibrogenic activity of synoviocytes around the TMJ. Our findings partially clarify the molecular mechanisms underlying the emergence of TMJ-OA and may aid in identifying drug targets for treating this condition at the molecular level.

Characterization of PAX9 variant P20L identified in a Japanese family with tooth agenesis

Transcription factors PAX9 and MSX1 play crucial roles in the development of permanent teeth at the bud stage, and their loss-of-function variants have been associated with congenital tooth agenesis. We sequenced the coding regions of the PAX9 and MSX1 genes from nine patients with non-syndromic tooth agenesis, and identified a missense mutation, P20L, of PAX9 in a single familial case involving three patients in two generations. Identical mutation was previously reported by other authors, but has not been characterized in detail. The mutation was located in a highly conserved N-terminal subdomain of the paired domain and co-segregated as a heterozygote with tooth agenesis. The patients showed defects primarily in the first and second molars, which is typical for cases attributable to PAX9 mutation. Luciferase reporter assay using the 2.3-kb promoter region of BMP4 and electrophoretic mobility shift assay using the CD19-2(A-ins) sequence revealed that P20L substitution eliminated most of the transactivation activity and specific DNA binding activity of PAX9 under the experimental conditions we employed, while some residual activity of the mutant was evident in the former assay. The hypomorphic nature of the variant may explain the relatively mild phenotype in this case, as compared with other PAX9 pathogenic variants such as R26W.

Influence of dexamethasone on masseter muscle wet weight in growing rats

Abstract The objective of this study was to investigate the influence of corticosteroids on the masseter wet weight and changes after discontinuation of the administration by comparison with those of hind leg skeletal muscles. Thirty-five male Wister rats, 9 weeks old, were used for the experiment. As a corticosteroids, dexamethasone was administered in drinking water for 14 days in consentrations 0.5 and 3.0 μg/ml administration groups: LD (Low Dose group) and HD (High Dose group), respectively. A 21-day recovery period was set after the discontinuation. Recovery groups: LD-r and HD-r. Non-treated groups: CO (CO-b, CO, CO-r). After the experimental period, the superficial masseter and the rectus femoris and gastrocnemius were excised, and the wet weights were measured. The wet weights of each muscle were significantly lower in the LD and HD than in the CO (p < 0.05). More significant wet weight losses of hind leg were noted in the HD (p < 0.05). The wet weight reduction rates of the rectus femoris and gastrocnemius relative to those in the CO were 50 and 44% in the HD, but that of the masseter was only 25%. The reductions recovered to weights similar to those in the CO-r after the discontinuation in the LD-r, but the weights in the HD-r were significantly lower than those in the other 2 groups (p < 0.05). Dexamethasone reduced the wet weight of the superficial masseter in the growing rats, but the influence was smaller than that on the hind leg muscles, suggesting that the reduction can be recovered by discontinuation when the corticosteroids is not administered at high doses.