Osteoblastic Wntless deletion differentially regulates the fate and functions of bone marrow-derived stem cells in relation to age.

Although functional association between Wnt signaling and bone homeostasis has been well described through genetic ablation of Wntless (Wls), the mechanisms of how osteoblastic Wls regulates the fate of bone marrow stromal cells (BMSCs) and hematopoietic stem cells (HSCs) in relation to age are not yet understood. Here, we generated Col2.3-Cre;Wlsfl/fl mice that were free from premature lethality and investigated age-related impacts of osteoblastic Wls deficiency on hematopoiesis, BM microenvironment, and maintenance of BMSCs (also known as BM-derived mesenchymal stem/stromal cells) and HSCs. Ablation of osteoblastic Wls deteriorated BM microenvironment and bone mass accrual along with age-independent effects on functions of BMSCs. Osteoblastic Wls deletion impaired HSC repopulation and progeny with skewing toward myeloid lineage cells only at old stage. As proven by hallmarks of stem cell senescence, osteoblastic Wls ablation differentially induced senescence of BMSCs and HSCs in relation to age without alteration in their BM frequency. Our findings support that deletion of Wls in Col2.3-expressing cells induces senescence of BMSCs and impairs BM microenvironment in age-independent manner. Overall, long-term deterioration in BM microenvironment contributes to age-related HSC senescence with impaired progeny and hematopoiesis, which also suggests possible roles of osteoblastic Wls on the maintenance of BM HSCs.

Local supplementation with plant-derived recombinant human FGF2 protein enhances bone formation in critical-sized calvarial defects.

Numerous studies have demonstrated the advantages of plant cell suspension culture systems in producing bioactive recombinant human growth factors. This study investigated the biological activity of recombinant basic human fibroblast growth factor (rhFGF2) protein produced by a plant culture system to enhance new bone formation in a bone defect mouse model. The human FGF2 cDNA gene was cloned into a plant expression vector driven by the rice α-amylase 3D promoter. The vector was introduced into rice calli (Oryza sativa L. cv. Dongjin), and the clone with the highest expression of rhFGF2 was selected. Maximum accumulation of rhFGF2 protein (approximately 28 mg/l) was reached at 13 day post-incubation. Male C57BL/6 mice underwent calvarial defect surgery and the defects were loaded with absorbable collagen sponge (ACS) only (ACS group) or ACS impregnated with 5 µg of plant-derived rhFGF2 (p-FGF2) protein or E. coli-derived rhFGF2 (e-FGF2) protein. Similar to the effects of e-FGF2, local delivery with p-FGF2 enhanced bone healing in the damaged region to higher levels than the ACS group. Exogenous addition of p-FGF2 or e-FGF2 exhibited similar effects on proliferation, mineralization, and osteogenic marker expression in MC3T3-E1 cells. Together, the current findings support the usefulness of this plant-based expression system for the production of biologically active rhFGF2.

Oral supplementation with p-coumaric acid protects mice against diabetes-associated spontaneous destruction of periodontal tissue.

OBJECTIVE: Dietary bioactive materials having anti-inflammatory and antioxidant potentials are able to inhibit diabetes-associated periodontal complications. Although numerous studies indicate that administration of p-coumaric acid (p-CA) ameliorates diabetes and diabetes-related complications, the roles of p-CA on periodontal tissue destruction in diabetic mice and the possible mechanisms therein are not completely understood. In this study, we evaluated whether supplementation with p-CA protects mice against diabetes-associated spontaneous periodontal destruction and also explored the associated mechanism therein using in vivo and in vitro experimental systems. MATERIALS AND METHODS: C57BL/6 male mice were divided into sham, streptozotocin (STZ), and STZ+CA groups (n = 5/group). Sham group was intraperitoneally injected with sodium buffer, whereas other two groups were injected with the buffer containing 160 mg/kg of STZ. STZ-induced diabetic mice received oral gavage with p-CA (50 mg/kg) (STZ+CA group) or with buffer only (STZ group) daily for 6 weeks. The effect of p-CA on diabetes-associated spontaneous periodontal destruction was evaluated using µCT analysis, hematoxylin and eosin staining, tartrate-resistant acid phosphatase staining, and immunohistochemical staining methods. The efficacies of p-CA on cell proliferation, osteoblast differentiation, reactive oxygen species (ROS) accumulation, and antioxidant-related marker expression were examined using human periodontal ligament fibroblasts (hPLFs) cultured under high glucose condition. RESULTS: Streptozotocin group exhibited periodontal tissue destruction along with increased inflammation, oxidative stress, and osteoclast formation, as well as with decreased osteogenesis. However, oral administration with p-CA protected mice against STZ-induced periodontal destruction by inhibiting inflammation and osteoclastic activation. STZ+CA group also showed higher expression of antioxidant and osteogenic markers in periodontal tissue than did STZ group. Treatment with high glucose concentration (30 mmol/L) impaired proliferation and osteoblast differentiation of hPLFs along with cellular ROS accumulation, whereas these impairments were almost completely disappeared by supplementation with p-CA. CONCLUSION: These findings demonstrate that supplementation with p-CA inhibits diabetes-associated spontaneous destruction of periodontal tissue by enhancing anti-inflammatory, anti-osteoclastogenic, and antioxidant defense systems in STZ-treated mice.

Local delivery of recombinant human FGF7 enhances bone formation in rat mandible defects.

Fibroblast growth factor 7 (FGF7) plays an important role in regulating the proliferation, migration, and differentiation of cells. However, the role of FGF7 in bone formation is not yet fully understood. We examined the effect of FGF7 on bone formation using a rat model of mandible defects. Rats underwent mandible defect surgery and then either scaffold treatment alone (control group) or FGF7-impregnated scaffold treatment (FGF7 group). Micro-CT and histological analyses revealed that the FGF7 group exhibited greater bone formation than did the control group 10 weeks after surgery. With the exception of total porosity (%), all bone parameters had higher values in the FGF7 group than in the control group at each follow-up after surgery. The FGF7 group showed greater expression of osteogenic markers, such as runt-related transcription factor 2, osterix, osteocalcin, bone morphogenetic protein 2, osteopontin, and type I collagen in newly formed bone than did the control group. The delivery of FGF7 also increased the messenger RNA expression of stromal-cell-derived factor 1 (SDF-1) and CXCR4 in newly formed bone in the FGF7 group compared with the control group. Further, addition of exogenous FGF7 induced migration of rat bone marrow stromal cells and increased the expression of SDF-1 and CXCR4 in the cells. Furthermore, the addition of FGF7 augmented mineralization in the cells with increased expression of osteogenic markers, and this augmentation was significantly suppressed by an inhibitor specific for c-Jun N-terminal kinase (SP600125) or extracellular-signal-regulated kinase (PD98059). Collectively, these results suggest that local delivery of FGF7 increases bone formation in a mandible defect with enhanced osteogenesis and chemoattraction.

Fibroblast growth factor-7 facilitates osteogenic differentiation of embryonic stem cells through the activation of ERK/Runx2 signaling.

Fibroblast growth factor-7 (FGF7) is known to regulate proliferation and differentiation of cells; however, little information is available on how FGF7 affects the differentiation of embryonic stem cells (ESCs). We examined the effects of FGF7 on proliferation and osteogenic differentiation of mouse ESCs. Exogenous FGF7 addition did not change the proliferation rate of mouse ESCs. In contrast, the addition of FGF7 facilitated the dexamethasone, ascorbic acid, and ß-glycerophosphate (DAG)-induced increases in bone-like nodule formation and calcium accumulation. FGF7 also augmented mRNA expression of runt-related transcription factor-2 (Runx2), osterix, bone sialoprotein (BSP), and osteocalcin (OC) in the presence of DAG. FGF7-mediated increases in the mineralization and bone-specific gene expression were almost completely attenuated by pretreating with anti-FGF7 antibody. FGF7 treatment accelerated the DAG-induced activation of extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) in the cells. A pharmacological inhibitor specific to ERK, but not to JNK or p38 kinase, dramatically suppressed FGF7-mediated mineralization and accumulation of collagen and OC in the presence of DAG. This suppression was accompanied by the reduction in Runx2, osterix, BSP, and OC mRNA levels, which were increased by FGF7 in the presence of DAG. Collectively, our results suggest that FGF7 stimulates osteogenic differentiation, but not proliferation, in ESCs, by activating ERK/Runx2 signaling.

Evaluation of osseointegration of Ti-6Al-4V alloy orthodontic mini-screws with ibandronate-loaded TiO2 nanotube layer.

Recently, the use of orthodontic mini-screws as an anchorage for orthodontic treatment is increasing, and the degree of osseointegration of the mini-screws affects the performance of orthodontic treatment. This study aimed to evaluate the biocompatibility and osseointegration of Titanium 6Aluminum 4Vanadium (Ti-6Al-4V) alloy orthodontic mini-screws with an ibandronate-loaded TiO2 nanotube (TNT) layer. The TNT layer was formed on the surface of the Ti-6Al-4V alloy orthodontic mini-screws and loaded with ibandronate. The TNT formed by anodic oxidation formed a completely self-organized and compact structure and was stably released for 7 days after loading with ibandronate. Mini-screws loaded with ibandronate were implanted into both tibias of rats, confirming rapid initial bone regeneration. We demonstrate that the release of stable ibandronate from the TNT layer of Ti-6Al-4V alloy orthodontic mini-screws can effectively improve biocompatibility and osseointegration.

Streptococcus mutans GS-5 antigen I/II stimulates cell survival in serum deprived-cultures through PI3K/Akt pathways.

The antigen I/II (AgI/II) protein is a major surface protein that mediates the attachment of Streptococcus mutans (S. mutans) to the saliva-coated pellicle. Numerous studies have investigated not only the mechanisms by which AgI/II signaling is transduced within cells, but have also attempted to use AgI/II-specific antibodies to treat dental caries and host immune responses. However, little information is available about the effects of AgI/II on basic cellular events in bone cells. In this study, we examined the effects of the His-tagged recombinant N-terminal half of the AgI/II protein (rAgI/II-N) generated from S. mutans GS-5 on the viability, proliferation, and cell cycle progression of primary calvarial osteoblasts. We also investigated the mechanisms involved in the rAgI/II-N-mediated survival of serum-starved osteoblasts. We found that rAgI/II treatment attenuated the serum deprivation-induced decrease in cell viability and proliferation of osteoblasts. rAgI/II-N also prevented the loss of mitochondrial membrane potential (MMP), alterations in levels of two key mitochondrial Bcl-2 family proteins, and the accumulation of numerous cells into the sub-G(1) phase that were observed in serum-starved osteoblasts. Pharmacological inhibitors of phosphoinositide 3-kinase (PI3K), but not of extracellular signal-regulated kinase or Ras, blocked the rAgI/II-N-mediated protection against serum deprivation-induced cell death. Additional experiments revealed that the integrin α5ß1-mediated PI3K pathway is required for rAgI/II-N-mediated Akt phosphorylation in osteoblasts. Collectively, these results suggest that rAgI/II-N induces survival signals in serum-starved osteoblasts through integrin-induced PI3K/Akt signaling pathways.

Sodium fluoride induces apoptosis in mouse embryonic stem cells through ROS-dependent and caspase- and JNK-mediated pathways.

Sodium fluoride (NaF) is used as a source of fluoride ions in diverse applications. Fluoride salt is an effective prophylactic for dental caries and is an essential element required for bone health. However, fluoride is known to cause cytotoxicity in a concentration-dependent manner. Further, no information is available on the effects of NaF on mouse embryonic stem cells (mESCs). We investigated the mode of cell death induced by NaF and the mechanisms involved. NaF treatment greater than 1mM reduced viability and DNA synthesis in mESCs and induced cell cycle arrest in the G(2)/M phase. The addition of NaF induced cell death mainly by apoptosis rather than necrosis. Catalase (CAT) treatment significantly inhibited the NaF-mediated cell death and also suppressed the NaF-mediated increase in phospho-c-Jun N-terminal kinase (p-JNK) levels. Pre-treatment with SP600125 or z-VAD-fmk significantly attenuated the NaF-mediated reduction in cell viability. In contrast, intracellular free calcium chelator, but not of sodium or calcium ion channel blockers, facilitated NaF-induced toxicity in the cells. A JNK specific inhibitor (SP600125) prevented the NaF-induced increase in growth arrest and the DNA damage-inducible protein 45α. Further, NaF-mediated loss of mitochondrial membrane potential was apparently inhibited by pifithrin-α or CAT inhibitor. These findings suggest that NaF affects viability of mESCs in a concentration-dependent manner, where more than 1mM NaF causes apoptosis through hydroxyl radical-dependent and caspase- and JNK-mediated pathways.

Astaxanthin Protects against Hyperglycemia-Induced Oxidative and Inflammatory Damage to Bone Marrow and to Bone Marrow-Retained Stem Cells and Restores Normal Hematopoiesis in Streptozotocin-Induced Diabetic Mice.

Hyperglycemia has various adverse health effects, some of which are due to chronic oxidative and inflammatory impairment of bone marrow (BM), hematopoietic stem cells (HSCs), and mesenchymal stem cells (MSCs). Astaxanthin (ASTX) has been shown to ameliorate hyperglycemia-associated systemic complications and acute mortality, and this effect is partially associated with restoration of normal hematopoiesis. Here, the effects of ASTX on diabetes-induced complications in BM and BM stem cells were investigated, and the underlying molecular mechanisms were elucidated. Ten-week-old C57BL/6 mice received a single intraperitoneal injection of streptozotocin (STZ; 150 mg/kg) in combination with oral gavage of ASTX (12.5 mg/kg) for 30 or 60 consecutive days. Supplemental ASTX ameliorated acute mortality and restored the STZ-impaired bone mass accrual and BM microenvironment in STZ-injected mice. Oral gavage of ASTX suppressed osteoclast formation in the BM of STZ-injected mice. Specifically, supplementation with ASTX inhibited oxidative stress and senescence induction of BM HSCs and MSCs and ameliorated hematopoietic disorders in STZ-injected mice. These effects of ASTX were associated with BM restoration of angiopoietin 1, stromal cell-derived factor 1, ß-catenin, and Nrf2. Long-term ASTX gavage also recovered the STZ-induced dysfunction in migration, colony formation, and mineralization of BM-derived stromal cells. Further, a direct addition of ASTX exhibited direct and dose-dependent inhibition of osteoclastic activation without cytotoxic effects. Collectively, these results indicate that ASTX protects against diabetes-induced damage in the BM microenvironment in BM, HSCs, and MSCs and restores normal hematopoiesis and bone accrual in STZ-injected mice.

Functional improvement of collagen-based bioscaffold to enhance periodontal-defect healing via combination with dietary antioxidant and COMP-angiopoietin 1.

Scaffolds combined with bioactive agents can enhance bone regeneration at therapeutic sites. We explore whether combined supplementation with coumaric acid and recombinant human-cartilage oligomeric matrix protein-angiopoietin 1 (rhCOMP-Ang1) is an ideal approach for bone tissue engineering. We developed coumaric acid-conjugated absorbable collagen scaffold (CA-ACS) and investigated whether implanting CA-ACS in combination with rhCOMP-Ang1 facilitates ACS- or CA-ACS-mediated bone formation using a rat model of critically sized mandible defects. We examined the mechanisms by which coumaric acid and rhCOMP-Ang1 regulate behaviors of human periodontal ligament fibroblasts (hPLFs). The CA-ACS exhibits greater anti-degradation and mechanical strength properties than does ACS alone. Implanting CA-ACS loaded with rhCOMP-Ang1 greatly enhances bone regeneration at the defect via the activation of angiogenic, osteogenic, and anti-osteoclastic responses compared with other rat groups implanted with an ACS alone or CA-ACS. Treatment with both rhCOMP-Ang1 and coumaric acid increases proliferation, mineralization, and migration of cultured hPLFs via activation of the Ang1/Tie2 signaling axis at a greater rate than treatment with either of them alone. Collectively, this study demonstrates that CA-ACS impregnated with rhCOMP-Ang1 enhances bone regeneration at therapeutic sites, and this enhancement is associated with a synergistic interaction between rhCOMP-Ang1-mediated angiogenesis and coumaric acid-related antioxidant responses.

Improvement of osseointegration of Ti-6Al-4V ELI alloy orthodontic mini-screws through anodization, cyclic pre-calcification, and heat treatments.

BACKGROUND: Mini-screws are widely used as temporary anchorages in orthodontic treatment, but have the disadvantage of showing a high failure rate of about 10%. Therefore, orthodontic mini-screws should have high biocompatibility and retention. Previous studies have demonstrated that the retention of mini-screws can be improved by imparting bioactivity to the surface. The method for imparting bioactivity proposed in this paper is to sequentially perform anodization, periodic pre-calcification, and heat treatments with a Ti-6Al-4V ELI alloy mini-screw. MATERIALS AND METHODS: A TiO2 nanotube-structured layer was formed on the surface of the Ti-6Al-4V ELI alloy mini-screw through anodization in which a voltage of 20 V was applied to a glycerol solution containing 20 wt% H2O and 1.4 wt% NH4F for 60 min. Fine granular calcium phosphate precipitates of HA and octacalcium phosphate were generated as clusters on the surface through the cyclic pre-calcification and heat treatments. The cyclic pre-calcification treatment is a process of immersion in a 0.05 M NaH2PO4 solution and a saturated Ca(OH)2 solution at 90 °C for 1 min each. RESULTS: It was confirmed that the densely structured protrusions were precipitated, and Ca and P concentrations, which bind and concentrate endogenous bone morphogenetic proteins, increased on the surface after simulated body fluid (SBF) immersion test. In addition, the removal torque of the mini-screw fixed into rabbit tibias for 4 weeks was measured to be 8.70 ± 2.60 N cm. CONCLUSIONS: A noteworthy point in this paper is that the Ca and P concentrations, which provide a scaffold suitable for endogenous bone formation, further increased over time after SBF immersion of the APH group specimens. The other point is that our mini-screws have a significantly higher removal torque compared to untreated mini-screws. These results represent that the mini-screw proposed in this paper can be used as a mini-screw for orthodontics.

Quercetin inhibits α-MSH-stimulated melanogenesis in B16F10 melanoma cells.

Quercetin is known to inhibit tyrosinase activity and melanin production in melanocytes. However, several reports suggest that quercetin has different and opposite effects on melanogenesis. This study examined the precise effects of quercetin on melanogenesis using cell-free assay systems and melanocytes. Quercetin inhibited the monophenolase and diphenolase activities of tyrosinase, and melanin synthesis in cell-free assay systems. Quercetin induced mild stimulation of the tyrosinase activity and dihydroxyphenylalaminechrome tautomerase (TRP-2) expression but only at low concentrations (<20 µm) in B16F10 melanoma cells. In contrast, the addition of 50 µm quercetin to the cells led to a significant decrease in the activity and synthesis of tyrosinase, as well as a decrease in the expression of tyrosinase-related protein-1 and TRP-2 proteins, regardless of the presence or absence of α-melanocyte stimulating hormone (α-MSH). Quercetin also reduced the intracellular cAMP and the phosphorylated protein kinase A levels in α-MSH-stimulated B16F10 cells. Moreover, quercetin (20 µm) diminished the expression and activity of tyrosinase, and melanin content in cultured normal human epidermal melanocytes. These effects were not related to its cytotoxic action. Although the in vivo effects of quercetin are still unclear, these results suggest that quercetin could play important roles in controlling melanogenesis.

Supplemental Ferulic Acid Inhibits Total Body Irradiation-Mediated Bone Marrow Damage, Bone Mass Loss, Stem Cell Senescence, and Hematopoietic Defect in Mice by Enhancing Antioxidant Defense Systems.

While total body irradiation (TBI) is an everlasting curative therapy, the irradiation can cause long-term bone marrow (BM) injuries, along with senescence of hematopoietic stem cells (HSCs) and mesenchymal stem cells (MSCs) via reactive oxygen species (ROS)-induced oxidative damages. Thus, ameliorating or preventing ROS accumulation and oxidative stress is necessary for TBI-requiring clinical treatments. Here, we explored whether administration of ferulic acid, a dietary antioxidant, protects against TBI-mediated systemic damages, and examined the possible mechanisms therein. Sublethal TBI (5 Gy) decreased body growth, lifespan, and production of circulating blood cells in mice, together with ROS accumulation, and senescence induction of BM-conserved HSCs and MSCs. TBI also impaired BM microenvironment and bone mass accrual, which was accompanied by downregulated osteogenesis and by osteoclastogenic and adipogenic activation in BM. Long-term intraperitoneal injection of ferulic acid (50 mg/kg body weight, once per day for 37 consecutive days) protected mice from TBI-mediated mortality, stem cell senescence, and bone mass loss by restoring TBI-stimulated disorders in osteogenic, osteoclastic, and adipogenic activation in BM. In vitro experiments using BM stromal cells supported radioprotective effects of ferulic acid on TBI-mediated defects in proliferation and osteogenic differentiation. Overall, treatment with ferulic acid prevented TBI-mediated liver damage and enhanced endogenous antioxidant defense systems in the liver and BM. Collectively, these results support an efficient protection of TBI-mediated systemic defects by supplemental ferulic acid, indicating its clinical usefulness for TBI-required patients.

Astaxanthin Inhibits Diabetes-Triggered Periodontal Destruction, Ameliorates Oxidative Complications in STZ-Injected Mice, and Recovers Nrf2-Dependent Antioxidant System.

Numerous studies highlight that astaxanthin (ASTX) ameliorates hyperglycemic condition and hyperglycemia-associated chronic complications. While periodontitis and periodontic tissue degradation are also triggered under chronic hyperglycemia, the roles of ASTX on diabetes-associated periodontal destruction and the related mechanisms therein are not yet fully understood. Here, we explored the impacts of supplemental ASTX on periodontal destruction and systemic complications in type I diabetic mice. To induce diabetes, C57BL/6 mice received a single intraperitoneal injection of streptozotocin (STZ; 150 mg/kg), and the hyperglycemic mice were orally administered with ASTX (12.5 mg/kg) (STZ+ASTX group) or vehicle only (STZ group) daily for 60 days. Supplemental ASTX did not improve hyperglycemic condition, but ameliorated excessive water and feed consumptions and lethality in STZ-induced diabetic mice. Compared with the non-diabetic and STZ+ASTX groups, the STZ group exhibited severe periodontal destruction. Oral gavage with ASTX inhibited osteoclastic formation and the expression of receptor activator of nuclear factor (NF)-κB ligand, 8-OHdG, γ-H2AX, cyclooxygenase 2, and interleukin-1ß in the periodontium of STZ-injected mice. Supplemental ASTX not only increased the levels of nuclear factor erythroid 2-related factor 2 (Nrf2) and osteogenic transcription factors in the periodontium, but also recovered circulating lymphocytes and endogenous antioxidant enzyme activity in the blood of STZ-injected mice. Furthermore, the addition of ASTX blocked advanced glycation end products-induced oxidative stress and growth inhibition in human-derived periodontal ligament cells by upregulating the Nrf2 pathway. Together, our results suggest that ASTX does not directly improve hyperglycemia, but ameliorates hyperglycemia-triggered periodontal destruction and oxidative systemic complications in type I diabetes.

Activation of RhoA and FAK induces ERK-mediated osteopontin expression in mechanical force-subjected periodontal ligament fibroblasts.

The precise mechanism by which Rho kinase translates the mechanical signals into OPN up-regulation in force-exposed fibroblasts has not been elucidated. Human periodontal ligament fibroblasts (hPLFs) were exposed to mechanical force by centrifuging the culture plates at a magnitude of 50 g/cm(2) for 60 min. At various times of the force application, they were processed for analyzing cell viability, trypan blue exclusion, and OPN expression at protein and RNA levels. Cellular mechanism(s) of the force-induced OPN up-regulation was also examined using various kinase inhibitors or antisense oligonucleotides specific to mechanosensitive factors. Centrifugal force up-regulated OPN expression and induced a rapid and transient increase in the phosphorylation of focal adhesion kinase (FAK), extracellular signal-regulated kinase (ERK), and Elk1. Pharmacological blockade of RhoA/Rho-associated coiled coil-containing kinase (ROCK) signaling markedly reduced force-induced FAK and ERK1/2 phosphorylation. Transfecting hPLFs with FAK antisense oligonucleotide diminished ERK1/2 activation and force-induced OPN expression. Further, ERK inhibitor inhibited significantly OPN expression, Elk1 phosphorylation, and activator protein-1 (AP-1)-DNA binding activation, but not FAK phosphorylation, in the force-applied cells. These results demonstrate that FAK signaling plays critical roles in force-induced OPN expression in hPLFs through interaction with Rho/ROCK as upstream effectors and ERK-Elk1/ERK-c-Fos as downstream effectors.

Surgical approach and orthodontic treatment of mandibular condylar osteochondroma.

Osteochondroma is a common benign tumor of bones, but it is rare in the mandibular condyle. With its outgrowth it manifests clinically as deviation of the mandible limitation of mouth opening, and facial asymmetry. After the tumor is diagnosed on the basis of clinical symptoms and radiographic examination including cone-beam computed tomography (CBCT) analysis, an appropriate surgery and treatment plan should be formulated. Herein, we present the case of a 44-year-old female patient who visited our dental hospital because her chin point had been deviating to the left side slowly but progressively over the last 3 years and she had difficulty masticating. Based on CBCT, she was diagnosed with skeletal Class III malocclusion accompanied by osteochondroma of the right mandibular condyle. Maxillary occlusal cant with the right side down was observed, but it was confirmed to be an extrusion of the molars associated with dental compensation. Therefore, after intrusion of the right molars with the use of temporary anchorage devices, sagittal split ramus osteotomy was used to remove the tumor and perform orthognathic surgery simultaneously. During 6 months after the surgery, continuous bone resorption and remodeling were observed in the condyle of the affected side, which led to a change in occlusion. During the postoperative orthodontic treatment, intrusive force and buccal torque were applied to the molars on the affected side, and a proper buccal overjet was created. After 18 months, CBCT revealed that the rate of bone absorption was continuously reduced, bone corticalization appeared, and good occlusion and a satisfying facial profile were achieved.

Growth observation and orthodontic treatment of a hemifacial microsomia patient treated with distraction osteogenesis.

Hemifacial microsomia (HFM) patients may experience emotional withdrawal during their growth period due to their abnormal facial appearance. Distraction osteogenesis at an early age to improve their appearance can encourage these patients. Some abnormalities of the affected side can be overcome by distraction osteogenesis at an early age. However, differences in the growth rate between the affected and unaffected sides during the rest of the growth period are inevitable due to the characteristics of HFM. Therefore, re-evaluation should be performed after completion of growth in order to achieve stable occlusion through either orthognathic surgery or camouflage orthodontic treatment. An eight-year-old patient visited the clinic exhibiting features of HFM with slight mandibular involvement. He received phase I treatment with distraction osteogenesis and a functional appliance. Distraction osteogenesis was performed at the right ramus, which resulted in an open bite at the right posterior dentition. After distraction osteogenesis, a functional appliance and partial fixed appliance were used to achieve extrusion of the affected posterior dentition and settlement of the occlusion adjustment on the unaffected posterior dentition. The patient visited the clinic regularly for follow-up assessments, and at the age of 20 years, he showed facial asymmetry of the mandible, which had deviated to the right side. He received orthodontic treatment to improve the occlusion of his posterior dentition after the growth period. Without orthognathic surgery, stable occlusion and a satisfactory facial appearance were obtained through camouflage orthodontic treatment.

Mechanical force induces type I collagen expression in human periodontal ligament fibroblasts through activation of ERK/JNK and AP-1.

Type I collagen (COL I) is the predominant collagen in the extracellular matrix of periodontal ligament (PDL), and its expression in PDL fibroblasts (PLF) is sensitive to mechanical force. However, the mechanism by which PLF induces COL I to respond to mechanical force is unclear. This study examined the nature of human PLF in mediating COL I expression in response to centrifugal force. Signal transduction pathways in the early stages of mechanotransduction involved in the force-driven regulation of COL I expression were also investigated. Centrifugal force up-regulated COL I without cytotoxicity and activated extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 kinase. ERK and JNK inhibitor blocked the expression of COL I but p38 kinase inhibitor had no effect. Centrifugal force activated activator protein-1 (AP-1) through dimerization between c-Fos and c-Jun transcription factors. ERK and JNK inhibitors also inhibited AP-1-DNA binding, c-Fos nuclear translocation, and c-Jun phosphorylation that were increased in the force-exposed PLF. Further, transfecting the cells with c-Jun antisense oligonucleotides almost completely abolished the force-induced increase of c-Jun phosphorylation and COL I induction. Our findings suggest that mechanical signals are transmitted into the nucleus by ERK/JNK signaling pathways and then stimulate COL I expression through AP-1 activation in force-exposed human PLF.

Mechanical force inhibits osteoclastogenic potential of human periodontal ligament fibroblasts through OPG production and ERK-mediated signaling.

Periodontal ligament and gingival fibroblasts play important roles in bone remodeling. Periodontal ligament fibroblasts stimulate bone remodeling while gingival fibroblasts protect abnormal bone resorption. However, few studies had examined the differences in stimulation of osteoclast formation between the two fibroblast populations. The precise effect of mechanical forces on osteoclastogenesis of these populations is also unknown. This study revealed that more osteoclast-like cells were induced in the co-cultures of bone marrow cells with periodontal ligament than gingival fibroblasts, and this was considerably increased when anti-osteoprotegerin (OPG) antibody was added to the co-cultures. mRNA levels of receptor activator of nuclear factor-kappaB ligand (RANKL) were increased in both populations when they were cultured with dexamethasone and vitamin D(3). Centrifugal forces inhibited osteoclastogenesis of both populations, and this was likely related to the force-induced OPG up-regulation. Inhibition of extracellular signal-regulated kinase (ERK) signaling by a pharmacological inhibitor (10 microM PD98059) or by siERK transfection suppressed the force-induced OPG up-regulation along with the augmentation of osteoclast-like cells that were decreased by the force. These results suggest that periodontal ligament fibroblasts are naturally better at osteoclast induction than gingival fibroblasts, and that centrifugal force inhibited osteoclastogenesis of the periodontal fibroblasts through OPG production and ERK activation.

Role of MAPK in mechanical force-induced up-regulation of type I collagen and osteopontin in human gingival fibroblasts.

In addition to periodontal ligament, the gingival plays an important role in alveolar bone remodeling induced by physiological and mechanical stimuli. However, there are few reports showing the cellular responses of human gingival fibroblasts (HGF) to a mechanical force. This study examined the effects of centrifugal force on the proliferation of the bone tissue components, such as type I collagen (COL I), osteopontin (OPN), and osteonectin (ONN) in the HGF. The roles of extracellular signal-regulated kinase (ERK), c-Jun-N-terminal kinase (JNK), and p-38 kinase were also investigated. Centrifugal force induced cell cycle arrest in the G(1) phase without any cytotoxic effects and increased the levels of COL I and OPN expression in the cells but had no effect on ONN. The force-induced up-regulation of COL I was found to be mediated by both the ERK-c-Fos-COL I and JNK-c-Jun-COL I pathways, while that of OPN was mediated only by the ERK-mediated pathway. Our present findings suggest that centrifugal force up-regulates COL I and OPN expression in HGF, where both ERK and JNK play indispensable roles.