Role of Surface Coverage of Sessile Probiotics in Their Interplay with Pathogen Bacteria Investigated by Digital Holographic Microscopy.

The adhesion of probiotics plays an important role in the gastrointestinal tract. Understanding the effect of the coverage of colonized probiotics on enteric pathogens is critical for the design of effective probiotic therapies. In the present work, we have investigated the adaptive behaviors of the intestinal pathogenic bacteria Enterobacter sakazakii (ES) near the surfaces coated with a probiotic─Lactobacillus rhamnosus GG (LGG) as a function of surface coverage ratio (CRLGG) by using a home-setup digital holographic microscopy. It shows that ES cells can adaptively sense LGG within a distance of 4.2 µm, even at CRLGG values as low as 0.05%. The growth inhibition of ES cells slightly varies with CRLGG, but the near-surface acceleration and accumulation of ES cells have much dependence on CRLGG. As CRLGG increases from 0.05 to 24.6%, the percentage of actively swimming ES, the motion bias, the acceleration, and the interplay duration do not linearly vary with CRLGG. Instead, each of them shows an extreme at CRLGG of 13.4%, corresponding to the chemotaxis behaviors of ES cells induced by diffusing stimuli (organic acids, bacteriocins, etc.) released from LGG, which showed an extreme concentration gradient at CRLGG = 13.4% by simulations. Our study clearly demonstrates that surface coverage of sessile probiotics profoundly influences their interplay with pathogen bacteria, which should be taken into account in designing probiotic therapies.

A two-year retrospective study on traumatic dental injury in the primary dentition.

The aim of this study was to analyze the causes, clinical characteristics, social factors, and current status of treatment of traumatic dental injury (TDI) in the primary dentition. A retrospective analysis was performed on 144 children (213 teeth) with TDI in the primary dentition from our hospital between December 2017 and June 2020. Data were analyzed using the chi-square test and the Mann-Withney-Wilcoxon test. Boys accounted for 68.1% (98/144) and girls for 31.9% (46/144) of all 144 children with TDI in the primary dentition, with a boy-girl ratio of 2.13:1. The primary age of TDI in deciduous teeth was 2 to 4 years old, accounting for 59% of all cases. Collision with others and fall were the 2 main causes of trauma to the deciduous teeth, making up 52.1% and 44.4% of all causes, respectively. Crown fracture injury was the most common type of TDI in the primary dentition, accounting for 37% of all cases (53/144). Of the 144 cases, 17.4% (25/144) was accompanied by soft tissue laceration, while 22.2% (32/144) by swelling or contusion of tissue. Maxillary teeth (92.4%) were more vulnerable to injury than mandibular teeth (7.5%), with maxillary incisor being the most vulnerable 1 (91.5%). The percentage of children arrived at the hospital for treatment 24 hours after the injury was the highest (57.0%, 82/144). After the hospital visit, 74.3% of children received treatment for the dental trauma. In terms of the treatment modalities, extraction of the traumatized teeth (27.1%) and pulpectomy + resin filling (or preformed crown) restoration were predominant. Approximately 28.5% (41/144) of cases were reviewed within 2 years, with the proportion of children with pulpitis or periapical infection being the highest (29.3%, 12/41). Age, gender, collision, and fall are the factors linked to a higher risk of TDI in the primary dentition in children under the age of 7. Resin filling (or preformed crown) restoration and pulpectomy are effective in preserving the affected tooth and controlling infection. However, the preservation of the affected tooth and the prevention of infection may be hampered by late visits and low follow-up rates.

MiR-20a promotes osteogenic differentiation in bone marrow-derived mesenchymal stem/stromal cells and bone repair of the maxillary sinus defect model in rabbits.

Introduction: This study aimed to determine whether miR-20 promoted osteogenic differentiation in bone marrow-derived mesenchymal stem/stromal cells (BMSCs) and accelerated bone formation in the maxillary sinus bone defect model in rabbits. Methods: BMSCs were transfected with miR-20a or anti-miR-20a for 12 h, followed by detection of RUNX2, Sp7 mRNA, bone morphogenetic protein 2 (BMP2), and RUNX2 protein expression. Alkaline phosphatase (ALP) activity and Alizarin Red S staining were used to detect calcified nodule deposition. In the rabbit maxillary sinus bone defect model, miR-20a loaded with AAV and BMP2 protein were mixed with Bio-Oss bone powder for filling the bone defect. At 4 weeks and 8 weeks, bone density was detected by cone beam computed tomography (CBCT), and new bone, osteoblasts, and collagen type 1 were evaluated by hematoxylin and eosin (HE) staining and immunohistochemical (IHC) staining. Results: Overexpression of miR-20a enhanced the mRNA and protein levels of BMP2, RUNX2, and SP7, the activity of ALP, and the levels of matrix mineralization, whereas the levels and activity of the aforementioned factors were decreased by anti-miR-20a treatment of BMSCs. Furthermore, miR-20a significantly increased the bone density, the number of osteoblasts, and the secretion of collagen type 1 in bone defects compared with Bio-Oss bone powder in the rabbit maxillary sinus bone defect model. Conclusion: Overall, miR-20a can induce osteogenic differentiation in BMSCs and accelerate bone formation of maxillary sinus defects in rabbits.

lncRNA CYTOR Facilitates Osteogenic Differentiation of Human Periodontal Ligament Stem Cells by Modulating SOX11 via Sponging miR-6512-3p.

Periodontal ligament stem cells (PDLSCs) are considered ideal cell sources for the regeneration of periodontal and alveolar bone tissue. Cytoskeleton Regulator RNA (CYTOR), a newly discovered long noncoding RNA, has been reported to function as competing endogenous RNA (ceRNA) and to be involved in many biological processes. However, its roles in PDLSC osteogenic differentiation remain unclear. Here, we firstly found CYTOR was mainly sublocalized in the cytoplasm of PDLSCs and CYTOR expression was increased during osteogenic differentiation of PDLSCs. By employing gain- and loss-of-function approaches, we then identified CYTOR overexpression promoted osteogenic differentiation of PDLSCs while CYTOR knockdown inhibited this process. Furthermore, bioinformatics analysis was utilized to show that both CYTOR and SOX11 mRNA contained the same seed sites for miR-6512-3p, which was further confirmed by dual luciferase reporter assay and RNA-binding protein immunoprecipitation. Notably, CYTOR conferred its functions by directly binding to miR-6512-3p and an inverse correlation between CYTOR and miR-6512-3p on the level on SOX11 and osteogenic differentiation of PDLSCs was obtained. Additionally, miR-6512-3p could bind to SOX11 mRNA 3' UTR and repressed SOX11 expression. Moreover, level of SOX11 was significantly increased during osteogenic differentiation of PDLSCs. Knockdown of SOX11 attenuated the increasing effect of CYTOR overexpression on osteogenic differentiation of PDLSCs. Collectively, these data supported that CYTOR positively modulated the expression of SOX11 through competitively binding to miR-6512-3p, thus promoting osteogenic differentiation of PDLSCs. The CYTOR/miR-6512-3p/SOX11 axis could be a novel therapeutic target for periodontal regeneration medicine.

Comparison of cephalometric measurements of the Twin Block and A6 appliances in the treatment of Class II malocclusion: a retrospective comparative cohort study.

Background: Skeletal Class II malocclusion is a common malocclusion that seriously affects patients' profile and occlusal function. The key to treatment is to use functional appliances guide the mandible forward. This study aimed to evaluate the clinical efficacy of traditional functional appliance Twin Block (TB) and invisible functional appliance (A6). Methods: In the retrospective cohort study, 46 patients with Class II Division 1 mandibular retrognathia (23 females, 23 males; mean age 13.66±4.25 years) from the Third Affiliated Hospital of Sun Yat-sen University were selected. They were divided into A6 group and TB group according to the type of appliance guided mandibular forward used in orthodontic treatment (n=23 each; average treatment time 9.82±3.52 months). Lateral cephalometric radiographs were taken before and at the end of each treatment, and paired t-test or paired rank-sum tests were performed when appropriate to detect any statistical significance at the level of α=0.05. Results: The baseline characteristics of the two groups of patients were similar. Treatment with both appliances helped correct Class II malocclusion, improve the discrepancy between the maxilla and mandible, reduce the labial inclination of the maxillary anterior teeth, and relieve the deep overbite. A comparison of the treatment effects of the TB and A6 groups showed that the A6 had a better effect when moving Point A backward, and performed better in the abduction of the anterior teeth. TB group has more advantages than A6 group in moving forward point B and improving the nasolabial angle. Conclusions: Both the A6 and TB can significantly improve Class II malocclusion. A6 showed an obvious advantage in moving Point A backward and adducting the anterior teeth, which better corrects a skeletal Class II malocclusion.

Dopamine Suppresses Osteogenic Differentiation of Rat Bone Marrow-Derived Mesenchymal Stem Cells via AKT/GSK-3ß/ß-Catenin Signaling Pathway.

Nervous system is critically involved in bone homeostasis and osteogenesis. Dopamine, a pivotal neurotransmitter, plays a crucial role in sympathetic regulation, hormone secretion, immune activation, and blood pressure regulation. However, the role of dopamine on osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells (rBMSCs) remains poorly understood. In this study, we firstly investigated the effect of dopamine on the apoptosis, proliferation, and osteogenic differentiation of rBMSCs. Dopamine did not, however, interfere with the apoptosis and proliferation of rBMSCs. Interestingly, dopamine suppressed the osteogenic differentiation of rBMSCs, as characterized by reduced ALP staining, ALP activity, mineralized nodule formation, and the mRNA and protein levels of osteogenesis-related genes (Col1a1, Alp, Runx2, Opn, and Ocn). Furthermore, dopamine inactivated AKT/GSK-3ß/ß-catenin signaling pathway. Treatment of LiCl (GSK-3ß inhibitor) rescued the inhibitory effects of dopamine on osteogenic differentiation of rBMSCs. LY294002 (AKT inhibitor) administration exacerbated the inhibitory effects of dopamine on osteogenic differentiation of rBMSCs. Taken together, these findings indicate that dopamine suppresses osteogenic differentiation of rBMSCs via AKT/GSK-3ß/ß-catenin signaling pathway. Our study provides new insights into the role of neurotransmitters in bone homeostasis.

MiR-20a: a mechanosensitive microRNA that regulates fluid shear stress-mediated osteogenic differentiation via the BMP2 signaling pathway by targeting BAMBI and SMAD6.

Background: MicroRNAs (miRNAs) are crucial regulators of diverse biological and pathological processes. This study aimed to investigate the role of microRNA 20a (miR-20a) in fluid shear stress (FSS)-mediated osteogenic differentiation. Methods: In the present study, we subjected osteoblast MC3T3-E1 cells or mouse bone marrow stromal cells (BMSCs) to single bout short duration FSS (12 dyn/cm2 for 1 hour) using a parallel plate flow system. The expression of miR-20a was quantified by miRNA array profiling and real-time quantitative polymerase chain reaction (qRT-PCR) during FSS-mediated osteogenic differentiation. The expression of osteogenic differentiation markers such as Runt-related transcription factor 2 (RUNX2), alkaline phosphatase (ALP), and SP7 transcription factor (SP7) was detected. Bioinformatics analysis and a luciferase assay were performed to confirm the potential targets of miR-20a. Results: Osteoblast-expressed miR-20a is sensitive to the mechanical environments of FSS, which are differentially up-regulated during steady FSS-mediated osteogenic differentiation. MiR-20a enhances FSS-induced osteoblast differentiation by activating the bone morphogenetic protein 2 (BMP2) signaling pathway. Both BMP and activin membrane-bound inhibitor (BAMBI) and mothers against decapentaplegic family member 6 (SMAD6) are targets of miR-20a that negatively regulate the BMP2 signaling pathway. Conclusions: MiR-20a is a novel mechanosensitive miRNA that can enhance osteoblast differentiation in FSS mechanical environments, implying that this miRNA might be a target for bone tissue engineering and orthodontic bone remodeling for regenerative medicine applications.

Relationship of the maxillary posterior teeth and maxillary sinus floor in different skeletal growth patterns: A cone-beam computed tomographic study of 1600 roots.

Purpose: This study evaluated the distance from the posterior root apices to the maxillary sinus floor (MSF) and the frequency of roots touching or protruding through the MSF using cone-beam computed tomography (CBCT). Materials and Methods: This study included 100 subjects divided into different vertical and anteroposterior skeletal growth patterns. On CBCT images, the distance from the posterior root apices to MSF was measured and the frequency of roots touching or protruding through the MSF was evaluated using NNT software (version 5.3.0.0; ImageWorks, Elmsford, NY, USA). Results: No statistically significant differences were found in the distance from the posterior root apices to the MSF among vertical skeletal groups (P>0.05). The palatal roots of the first molar and the palatal, mesio-buccal and disto-buccal roots of the second molars had significantly less distance from MSF in skeletal class II than in class III (P<0.05). The high-angle group had the highest frequencies of roots touching or protruding into the maxillary sinus (49.8%); the lowest proportion of these roots was found in skeletal class III (28.3%) and the highest proportion in class II (50.3%). Males had shorter distances from the posterior root apices to the MSF and higher frequencies of roots protruding through or touching the MSF than females. Conclusion: Anteroposterior skeletal growth patterns and sex affected the distances from the maxillary posterior roots to the MSF. The frequency of roots protruding into or touching the sinus was affected by both vertical and anteroposterior skeletal groups and sex. These findings have implications for dental practice.

Evaluation of maxillary sinus volume in different craniofacial patterns: a CBCT study.

INTRODUCTION: Few studies have compared the relationship of MSV in the different craniofacial patterns. Hence, the purpose of this research was to evaluate maxillary sinus volume in different craniofacial patterns using cone-beam computed tomography. MATERIALS AND METHODS: This cross-sectional study included 100 pre-orthodontic patients mean aged 26.40 ± 6.77 (age ranged 21-64) years divided into different anteroposterior and vertical skeletal groups. From the cone beam computed tomography images using MIMICS 14.1 software, three-dimensional image of the maxillary sinus was constructed, and its volume was calculated. RESULTS: The mean maxillary sinus volume was 20,279.50 ± 7800.33 mm3. Among the anteroposterior skeletal groups, the mean maxillary sinus volume in skeletal Class II group is significantly larger than class III group (P < 0.05). Among the vertical skeletal groups, High-angle groups tend to have the largest maxillary sinus volume, though there were no significant differences among the groups (P > 0.05). Similarly, males have significantly larger maxillary sinus volume than females (P < 0.05). There was a positive correlation between ANB and maxillary sinus volume (P < 0.01). CONCLUSION: Maxillary sinus volume is significantly larger in skeletal class II than in skeletal class III group and in males than in females (P < 0.05). These inferences have several implications in orthodontics, endodontics and oral surgery.

Egr-1 mediates low-dose arecoline induced human oral mucosa fibroblast proliferation via transactivation of Wnt5a expression.

BACKGROUND: Arecoline is an alkaloid natural product found in the areca nut that can induce oral submucous fibrosis and subsequent development of cancer. However, numerous studies have shown that arecoline may inhibit fibroblast proliferation and prevent collagen synthesis. RESULTS: High doses of arecoline (> 32 µg/ml) could inhibit human oral fibroblast proliferation, while low doses of arecoline (< 16 µg/ml) could promote the proliferation of human oral fibroblasts. Wnt5a was found to be both sufficient and necessary for the promotion of fibroblast proliferation. Egr-1 could mediate the expression of Wnt5a in fibroblasts, while NF-κB, FOXO1, Smad2, and Smad3 did not. Treatment with siRNAs specific to Egr-1, Egr inhibitors, or Wnt5a antibody treatment could all inhibit arecoline-induced Wnt5a upregulation and fibroblast proliferation. CONCLUSIONS: Egr-1 mediates the effect of low dose arecoline treatment on human oral mucosa fibroblast proliferation by transactivating the expression of Wnt5a. Therefore, Egr inhibitors and Wnt5a antibodies are potential therapies for treatment of oral submucosal fibrosis and oral cancer.

Effects of 17ß-Estradiol combined with cyclical compressive stress on the proliferation and differentiation of mandibular condylar chondrocytes.

OBJECTIVE: The aim of this study is to investigate the effects of 17ß-Estradiol (E2) at different concentrations combined with cyclical compressive stress on the proliferation and differentiation of mandibular condylar chondrocytes (MCCs). DESIGN: MCCs, isolated from female Sprague-Dawley rats, were exposed to E2 at different concentration, cyclical compressive stress or the combination, effects of which on MCCs proliferation and differentiation were detected. RESULTS: E2 at physiological concentration (10-9 mol/L) has lower proliferative effects on MCCs, compared with non-physiological concentration (10-12 mol/L or 10-6 mol/L). For MCCs differentiation, effects of E2 at different concentration are totally opposite: E2 at 10-9 mol/L promotes MCCs differentiation, but at 10-12 mol/L or 10-6 mol/L, it inhibits MCCs differentiation. When combined with E2 at 10-9 mol/L, cyclical compressive stress shows synergistic effect on proliferation and differentiation. However, when combined with E2 at 10-12 mol/L or 10-6 mol/L cyclical compressive stress reverses the inhibition in MCCs differentiation provoked by E2 at 10-12 mol/L or 10-6 mol/L. CONCLUSION: Effects of E2 combined with cyclical compressive stress on MCCs proliferation and differentiation are different, which suggests that orthodontist should take fully consideration of the levels of E2 and adopt comprehensive strategies, so as to achieve better orthodontic effect.

Suppressing MicroRNA-30b by Estrogen Promotes Osteogenesis in Bone Marrow Mesenchymal Stem Cells.

MicroRNAs (miRNAs) have been widely demonstrated to interact with multiple cellular signaling pathways and to participate in a wide range of physiological processes. Estradiol-17ß (E2) is the most potent and prevalent endogenous estrogen that plays a vital role in promoting bone formation and reducing bone resorption. Currently, little is known about the regulation of miRNAs in E2-induced osteogenic differentiation. In the present study, the primary bone marrow mesenchymal stem cells from rats (rBMSCs) were isolated and incubated with E2, followed by miRNA profiling. The microarray showed that 29 miRNAs were differentially expressed in response to E2 stimulation. Further verification by real-time reverse-transcriptase polymerase chain reaction revealed that E2 enhanced the expression of let-7b and miR-25 but suppressed the miR-30b expression. Moreover, a gain-of-function experiment confirmed that miR-30b negatively regulated the E2-induced osteogenic differentiation. These data suggest an important role of miRNAs in osteogenic differentiation.

Expression of lubricin in rat posterior mandibular condylar cartilage following functional mandibular forward repositioning.

PURPOSE: The aim of the present study was to investigate the effects of mandibular forward repositioning on expression of lubricin in rat posterior condylar cartilage. METHODS: In total, fifty 5­week-old female Sprague Dawley rats were divided randomly into experimental groups and control groups. The animals in the experimental groups were fitted with modified acrylic inclined planes to advance the mandible, whereas rats in the normal control groups were left intact. Rats were sacrificed on days 3, 7, 14, 21, and 30, and temporomandibular joint (TMJ) samples were collected. The expression of lubricin of the posterior mandibular condylar cartilage was evaluated by immunohistochemistry. RESULTS: In the control groups, higher expression of lubricin was observed in the proliferative zone of the posterior mandibular condylar cartilage compared with the hypertrophic zone during the experimental period. Compared with the control group, the positive signals for lubricin of the posterior mandibular condylar cartilage in the experimental animals were significantly higher on days 7, 14, and 21; however, no statistical difference was found on day 3 or 30. CONCLUSIONS: Data analyses suggest that the bite jumping appliance temporarily enhanced lubricin expression, providing a good mechanical environment for the physiologic growth of the condyle and mandible, and contributes to TMJ remodeling by the regulation of condylar chondrocyte proliferation.

Cyclical compressive stress induces differentiation of rat primary mandibular condylar chondrocytes through phosphorylated myosin light chain II.

The role of myosin light chain II (MLC­II) in cellular differentiation of rat mandibular condylar chondrocytes (MCCs) induced by cyclical uniaxial compressive stress (CUCS) remains unclear. In the current study, a four­point bending system was used to apply CUCS to primary cultured MCCs from rats. It was identified that CUCS stimulated features of cellular differentiation including morphological alterations, cytoskeleton rearrangement and overproduction of proteoglycans. Furthermore, CUCS promoted runt­related transcription factor­2 (RUNX2) expression at mRNA (P<0.01) and protein levels (P<0.05) and elevated alkaline phosphatase (ALP) activity (P<0.01), which are both markers of osteogenic differentiation. Under conditions of stress, western blotting indicated that the ratio of phosphorylated MLC­II to total MLC­II was increased significantly (P<0.05). Silencing MLC­II by RNA interference reduced ALP activity (P<0.01), and eliminated RUNX2 mRNA expression (P<0.01). Addition of the MLC kinase inhibitor, ML­7, reduced the CUCS­associated upregulation of RUNX2 expression (P<0.01) and ALP activity (P<0.01). The data indicated that CUCS promoted cellular differentiation of rat primary MCCs, and this was suggested to be via the phosphorylation of MLC­II.

Treatment of a mandibular functional shift in an adolescent boy with temporomandibular disorder and crossbites.

A mandibular functional shift usually poses a challenge for orthodontists, especially when it is accompanied by a temporomandibular disorder (TMD). Accurate diagnosis and complete elimination of the etiologic factors are the keys to an esthetic and stable outcome. This article describes the treatment of a teenager with a mandibular functional shift, TMD symptoms, and facial asymmetry resulting from an asymmetric maxillary arch form and multiple crossbites as occlusal interferences. The treatment alternatives and effective orthodontic techniques are described. To optimize the treatment results and prevent the recurrence of the TMD after treatment, the displaced mandible was repositioned by full-time wearing of a splint for 10 months. Adhesive bite-blocks were used to maintain the newly acquired mandibular position during fixed appliance treatment. A series of nickel-titanium and stainless steel rectangular archwires was placed in the maxillary arch to reshape it for 8 months after alignment. Finally, the displaced mandible was steadily seated into its physiologic position with fine occlusion. The TMD symptoms disappeared and never relapsed after treatment. At 2 years 3 months of retention, there was good stability. The combined splint and fixed appliance approach resolved an intractable clinical problem and avoided using additional appliances. An esthetic, functional, and stable outcome was achieved that satisfied both the patient and his parents.

Fluid shear stress stimulates osteogenic differentiation of human periodontal ligament cells via the extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinase signaling pathways.

BACKGROUND: Fluid shear stress (FSS) is a major type of mechanical stress that is loaded on human periodontal ligament cells (hPDLCs) during mastication and orthodontic tooth movement. This study aims to clarify the effect of FSS on the osteogenic differentiation of hPDLCs and to further verify the involvement of mitogen-activated protein kinase (MAPK) signaling in this process. METHODS: After isolation and characterization, hPDLCs were subjected to 2-hour FSS at 12 dynes/cm(2), and cell viability, osteogenic gene mRNA expression, alkaline phosphatase (ALP) activity, secretion of Type I collagen (COL-I), and calcium deposition were assayed. The levels of phosphorylated p38 and phosphorylated extracellular signal-regulated kinase 1/2 (ERK1/2) in response to FSS were detected by Western blot, and the involvement of ERK1/2 and p38 MAPK signaling pathways in hPDLC osteogenesis under FSS was investigated using the specific MAPK inhibitors U0126 (2Z,3Z)-2,3-bis[amino(2-aminophenylthio)methylene]succinonitrile,ethanol) and SB203580 (4-[4-(4-fluorophenyl)-2-(4-[methylsulfinyl]phenyl)-1H-imidazol-5-yl]pyridine). RESULTS: The application of FSS on hPDLCs induced an early morphologic change and rearrangement of filamentous actin. ALP activity, messenger RNA (mRNA) levels of osteogenic genes, COL-I, and osteoid nodules were significantly increased by FSS. Moreover, ERK1/2 and p38 were activated in different ways after FSS exposure. U0126 and SB203580 completely blocked the FSS-induced increases in ALP activity and osteogenic gene mRNA expression and osteoid nodules formation. CONCLUSIONS: FSS is an effective approach for stimulating osteogenic differentiation of hPDLCs. The ERK1/2 and p38 MAPK signaling pathways are involved in this cellular process.

Single bout short duration fluid shear stress induces osteogenic differentiation of MC3T3-E1 cells via integrin ß1 and BMP2 signaling cross-talk.

Fluid shear stress plays an important role in bone osteogenic differentiation. It is traditionally believed that pulsed and continuous stress load is more favorable for fracture recovery and bone homeostasis. However, according to our clinical practice, we notice that one single stress load is also sufficient to trigger osteogenic differentiation. In the present study, we subject osteoblast MC3T3-E1 cells to single bout short duration fluid shear stress by using a parallel plate flow system. The results show that 1 hour of fluid shear stress at 12 dyn/cm(2) promotes terminal osteogenic differentiation, including rearrangement of F-actin stress fiber, up-regulation of osteogenic genes expression, elevation of alkaline phosphatase activity, secretion of type I collagen and osteoid nodule formation. Moreover, collaboration of BMP2 and integrin ß1 pathways plays a significant role in such differentiation processes. Our findings provide further experimental evidence to support the notion that single bout short duration fluid shear stress can promote osteogenic differentiation.

miRNA expression profile during fluid shear stress-induced osteogenic differentiation in MC3T3-E1 cells.

BACKGROUND: Mechanical stress plays an important role in the maintenance of bone homeostasis. Current hypotheses suggest that interstitial fluid flow is an important component of the system by which tissue level strains are amplified in bone. This study aimed to test the hypothesis that the short-term and appropriate fluid shear stress (FSS) is expected to promote the terminal differentiation of pre-osteoblasts and detect the expression profile of microRNAs in the FSS-induced osteogenic differentiation in MC3T3-E1 cells. METHODS: MC3T3-E1 cells were subjected to 1 hour of FSS at 12 dyn/cm(2) using a parallel plate flow system. After FSS treatment, cytoskeleton immunohistochemical staining and microRNAs (miRNAs) were detected immediately. Osteogenic gene expression and immunohistochemical staining for collagen type I were tested at the 24th hour after treatment, alkaline phosphatase (ALP) activity assay was performed at 24th, 48th, and 72 th hours after FSS treatment, and Alizarin Red Staining was checked at day 12. RESULTS: One hour of FSS at 12 dyn/cm(2) induced actin stress fiber formation and rearrangement, up-regulated osteogenic gene expression, increased ALP activity, promoted synthesis and secretion of type I collagen, enhanced nodule formation, and promoted terminal differentiation in MC3T3-E1 cells. During osteogenic differentiation, expression levels of miR-20a, -21, -19b, -34a, -34c, -140, and -200b in FSS-induced cells were significantly down-regulated. CONCLUSION: The short-term and appropriate FSS is sufficient to promote terminal differentiation of pre-osteoblasts and a group of miRNAs may be involved in FSS-induced pre-osteoblast differentiation.

Mechanical loading induced expression of bone morphogenetic protein-2, alkaline phosphatase activity, and collagen synthesis in osteoblastic MC3T3-E1 cells.

BACKGROUND: Bone morphogenetic protein (BMP)-2, alkaline phosphatase (ALP), and collagen type I are known to play a critical role in the process of bone remodeling. However, the relationship between mechanical strain and the expression of BMP-2, ALP, and COL-I in osteoblasts was still unknown. The purpose of this study was to investigate the effects of different magnitudes of mechanical strain on osteoblast morphology and on the expression of BMP-2, ALP, and COL-I. METHODS: Osteoblast-like cells were flexed at four deformation rates (0, 6%, 12%, and 18% elongation). The expression of BMP-2 mRNA, ALP, and COL-I in osteoblast-like cells were determined by real-time quantitative reverse transcription polymerase chain reaction, respectively. The results were subjected to analysis of variance (ANOVA) using SPSS 13.0 statistical software. RESULTS: The cells changed to fusiform and grew in the direction of the applied strain after the mechanical strain was loaded. Expression level of the BMP-2, ALP, and COL-I increased magnitude-dependently with mechanical loading in the experimental groups, and the 12% elongation group had the highest expression (P < 0.05). CONCLUSION: Mechanical strain can induce morphological change and a magnitude-dependent increase in the expression of BMP-2, ALP, and COL-I mRNA in osteoblast-like cells, which might influence bone remodeling in orthodontic treatment.

Rapid tooth movement through distraction osteogenesis of the periodontal ligament in dogs.

BACKGROUND: Animal models are needed for the study of rapid tooth movement into the extraction socket through distraction osteogenesis of the periodontal ligament. METHODS: Modified distraction devices were placed on eight dogs between the first and third mandibular premolars on the left sides; similar placement of traditional straight wise appliances on the right sides served as the control. The experimental distractors were activated (0.25 mm/d) twice a day and the control devices were activated (100 g) for two weeks with consolidation periods at weeks two, three, six, and ten. Two dogs were sacrificed at each consolidation time point; rates and patterns of tooth movement, loss of anchorage, and periapical films were evaluated, and the affected premolars and surrounding periodontal tissues were decalcified and examined histologically. General observations, X-ray periapical filming and histology examination were performed. RESULTS: Distal movement ((3.66+/-0.14) mm) measured two weeks after modified distraction exceeded that achieved using the traditional device ((1.15+/-0.21) mm; P<0.05). Loss of anchorage was minimally averaged (0.34+/-0.06) mm and (0.32+/-0.07) mm in the experimental and control sides, respectively. By radiography, apical and lateral surface root resorptions on both sides were minimal. Alveolar bone lesions were never evident. Fibroblasts were enriched in periodontal ligaments and bone spicules formed actively along directions of distraction. CONCLUSIONS: The canine model is suitable for the study of rapid tooth movement through distraction osteogenesis of the periodontal ligament. The technique accelerates tooth movement, periodontal remodeling, alveolar bone absorption, and may induce fibroblast formation, as compared to the traditional orthodontic method, without adversely affecting root absorption, bone loss, tooth mobility and anchorage loss.