The lysine methyltransferase SMYD2 facilitates neointimal hyperplasia by regulating the HDAC3-SRF axis

Coronary restenosis is an important cause of poor long-term prognosis in patients with coronary heart disease. Here, we show that lysine methyltransferase SMYD2 expression in the nucleus is significantly elevated in serum- and PDGF-BB-induced vascular smooth muscle cells (VSMCs), and in tissues of carotid artery injury-induced neointimal hyperplasia. Smyd2 overexpression in VSMCs (Smyd2-vTg) facilitates, but treatment with its specific inhibitor LLY-507 or SMYD2 knockdown significantly inhibits VSMC phenotypic switching and carotid artery injury-induced neointima formation in mice. Transcriptome sequencing revealed that SMYD2 knockdown represses the expression of serum response factor (SRF) target genes and that SRF overexpression largely reverses the inhibitory effect of SMYD2 knockdown on VSMC proliferation. HDAC3 directly interacts with and deacetylates SRF, which enhances SRF transcriptional activity in VSMCs. Moreover, SMYD2 promotes HDAC3 expression via tri-methylation of H3K36 at its promoter. RGFP966, a specific inhibitor of HDAC3, not only counteracts the pro-proliferation effect of SMYD2 overexpression on VSMCs, but also inhibits carotid artery injury-induced neointima formation in mice. HDAC3 partially abolishes the inhibitory effect of SMYD2 knockdown on VSMC proliferation in a deacetylase activity-dependent manner. Our results reveal that the SMYD2-HDAC3-SRF axis constitutes a novel and critical epigenetic mechanism that regulates VSMC phenotypic switching and neointimal hyperplasia.

Numerical Simulation on Fluid Flow within Rat Alveolar Bone under Orthodontic and Occlusal Loading / 医用生物力学

Objective To study fluid flow within alveolar bone under orthodontic and occlusal loading, so as to provide references for understanding the regulatory mechanism of bone remodeling during orthodontics. Methods An animal model for orthodontic tooth movement on rats was first constructed. The finite element model of tooth-periodontal ligament-alveolar bone was established based on micro-CT images and the strain field in alveolar bone under orthodontic or constant occlusal loading was analyzed. Then finite element model of alveolar bone was constructed from the bone near the cervical margin or apical root of mesial root. The fluid flow in this model under orthodontic and cyclic occlusal loading was further predicted by using fluid-solid coupling numerical simulation. Results The fluid velocity within alveolar bone cavity mainly distributed at 0-10 μm/s, and the fluid shear stress (FSS) was mainly distributed at 0-10 Pa. FSS on the surface of alveolar bone near the apical root was higher than that close to the cervical margin. Conclusions FSS at different levels could be produced at different location within alveolar bone cavity under orthodontic and cyclic occlusal loading, which might further activate biological response of bone cells on the surface of trabeculae and finally regulate the remodeling of alveolar bone and orthodontic movement of tooth. The results provide theoretical guidance for the clinical treatment of orthodontics.

Fluid-solid coupling numerical simulation on ideal porous structure of rat alveolar bone / 生物医学工程学杂志

Fluid shear stress (FSS) caused by interstitial fluid flow within trabecular bone cavities under mechanical loading is the key factor of stimulating biological response of bone cells. Therefore, to investigate the FSS distribution within cancellous bone is important for understanding the transduction process of mechanical forces within alveolar bone and the regulatory mechanism at cell level during tooth development and orthodontics. In the present study, the orthodontic tooth movement experiment on rats was first performed. Finite element model of tooth-periodontal ligament-alveolar bone based on micro computed tomography (micro-CT) images was established and the strain field in alveolar bone was analyzed. An ideal model was constructed mimicking the porous structure of actual rat alveolar bone. Fluid flow in bone was predicted by using fluid-solid coupling numerical simulation. Dynamic occlusal loading with orthodontic tension loading or compression loading was applied on the ideal model. The results showed that FSS on the surface of the trabeculae along occlusal direction was higher than that along perpendicular to occlusal direction, and orthodontic force has little effect on FSS within alveolar bone. This study suggests that the orientation of occlusal loading can be changed clinically by adjusting the shape of occlusal surface, then FSS with different level could be produced on trabecular surface, which further activates the biological response of bone cells and finally regulates the remodeling of alveolar bone.

Spreading Shape and Area Regulate the Osteogenesis of Mesenchymal Stem Cells

BACKGROUND: Mesenchymal stem cells (MSCs) have strong self-renewal ability and multiple differentiation potential. Some studies confirmed that spreading shape and area of single MSCs influence cell differentiation, but few studies focused on the effect of the circularity of cell shape on the osteogenic differentiation of MSCs with a confined area during osteogenic process.METHODS: In the present study, MSCs were seeded on a micropatterned island with a spreading area lower than that of a freely spreading area. The patterns had circularities of 1.0 or 0.4, respectively, and areas of 314, 628, or 1256 µm² . After the cells were grown on a micropatterned surface for 1 or 3 days, cell apoptosis and F-actin were stained and analyzed. In addition, the expression of β-catenin and three osteogenic differentiation markers were immunofluorescently stained and analyzed, respectively.RESULTS: Of these MSCs, the ones with star-like shapes and large areas promoted the expression of osteogenic differentiation markers and the survival of cells. The expression of F-actin and its cytosolic distribution or orientation also correlated with the spreading shape and area. When actin polymerization was inhibited by cytochalasin D, the shape-regulated differentiation and apoptosis of MSCs with the confined spreading area were abolished.CONCLUSION: This study demonstrated that a spreading shape of low circularity and a larger spreading area are beneficial to the survival and osteogenic differentiation of individual MSCs, which may be regulated through the cytosolic expression and distribution of F-actin.

Effects of Fluid Shear Stress on Gene Expression of Piezo1 in the Cells During Osteogenic Differentiation / 医用生物力学

Objective To investigate the gene expression of Piezo1 in four types of bone cells at different stages of osteogenic differentiation under fluid shear stress (FSS). Methods The mouse-derived mesenchymal stem cells (MSC), osteoblast-like cells MC3T3-E1, post-osteoblasts MLO-A5 and osteocytes MLO-Y4 were exposed to FSS at different magnitude (0.1, 1.1 Pa) with a custom-made cone-plate flow chamber for 0.5, 1, 3, 6, 12 h, respectively. The expression of Piezo1 mRNA was assessed by quantitative real-time polymerase chain reaction. Results Both Piezo1 and Piezo2 were expressed in four types of bone cells. The expression of Piezo1 was significantly up-regulated in all cells under FSS stimulation, and the expression level under 1.1 Pa FSS was significantly higher than that under 0.1 Pa FSS. In addition, the expression of Piezo1 in MSC, MC3T3-E1 and MLO-A5 cells increased to the highest level at 1 h under FSS stimulation. The expression of Piezo1 in MC3T3-E1 cells was much higher than that in the other three types of cells. Conclusions The expression of Piezo1 was related to the process of osteogenic differentiation, FSS level and loading time, and this research finding is of great significance to reveal the mechanism of mechanotransduction in bone tissues and to establish clinical treatment for bone diseases.

Effect of Connexin43 on Mechanical Tension-stimulated Osteogenic Transcription Factors of Human Periodontal Ligament Fibroblasts / 中国医学科学院学报

<p><b>OBJECTIVE</b>To investigate the expression and effect of Connexin43 (Cx43) on tensile tension-stimulated osteogenic transcription factors of human periodontal ligament fibroblasts (hPDLFs).</p><p><b>METHODS</b>After hPDLFs were treated with 5% elongation tension for 1 h, 2 h, 4 h, 8 h, and 24 h, we examined the expressions of Cx43, Osterix, and RUNX2 at the mRNA level. After Cx43 expression was suppressed by siRNA or 18α-GA, the changes The mRNA in hPDLFs of Osterix and RUNX2 were observed.</p><p><b>RESULTS</b>The expressions of Cx43, Osterix, and RUNX2 mRNA in hPDLFs increased in a time-dependent fashion following tensile strain (all P<0.05), with the highest level at 5% elongation for 24 h. After Cx43 expression was blocked by two different methods, the increasing expressions of Osterix and RUNX2 were inhibited.</p><p><b>CONCLUSIONS</b>5% cyclic tension upregulates Cx43 expression and promotes the expression of Osterix and RUNX2 in a time-dependent manner. Cx43 may be involved in the osteogenic response of hPDLFs to mechanical tension.</p>

Light-induced fluorescence enhancement in cells stained with Ca2+ indicators / 医用生物力学

Objective As the photostability of calcium ions (Ca2+) indicators is an important property for indicating the temporal features of cytosolic Ca2+ in cells, this study aims to quantitatively measure the light-induced fluorescence enhancement in cells stained with Ca2+ indicators. Methods Five cell lines, MC3T3-E1, RAW264.7, MLO-Y4, MEF3T3 and HEK293, were exposed to the light with five levels of optical power, respectively, so as to investigate the light induced responses of two commonly-used Ca2+ indicators, Fluo-4 AM and Oregon green. The light-induced fluorescence enhancement, the succeeding photobleaching and the thapsigargin (TG)-induced responsive peak followed by were observed. The characteristic parameters of responsive peaks were further analyzed. Results Light with higher power level would induce the fluorescence enhancement for both Fluo-4 AM or Oregon green, while the responsive percentage as well as the magnitude and time span of light-induced peak of Oregon green-stained cells were significantly lower than those of Fluo-4 AM-stained cells. Conclusions The use of Oregon green with low power level light shows better photostability to indicate the intracellular Ca2+.

Mathematic model of respiratory mechanics based on monitored physiological parameters / 医用生物力学

Objective To establish a model of respiratory mechanics with consideration of gas exchange and directly correlate with the gas content in blood during mechanical ventilation with the mechanics of respiratory system. Methods By coupling the physiological parameters of respiratory system and blood circulation system, including the molecular numbers of oxygen and carbon dioxide in alveoli and clinically monitored physiological parameters such as gas content, hemoglobin content, heart rate and cardiac output, a mechanical model was constructed to predict those dynamic parameters of gas content, pressure and flow rate in airway and alveoli in continuous breathing cycles. Results The gas content in different locations of a respiratory system was estimated by the model and the sensitivity of gas content in expiration to the undetermined parameters was evaluated. Conclusions The model of respiratory mechanics developed in the study is a preliminary attempt to predict the regulation roles of physiological parameters clinically monitored during mechanical ventilation, which will provide a theoretical support for the design and development of novel respirators in the follow-up experiment.

Dynamic investigation on the co-infection status of two pathogens in ticks from tourist point in Heilongjiang province / 中华流行病学杂志

Objective To monitor the co-infection status of Borrelia burgdorferi sensu lato (R.b.s.1) and spotted fever group Rickettsia (SFGR) in tourist areas of Heilongjiang province.Methods Polymerase chain reaction (PCR) was used to detect the 5S-23S rRNA intergenic spacer of B.b.s.1 and ompA of SFGR in ticks,dynamically collected from tourist areas of Heilongjiang province in 2010.Amplification products from positive ticks were sequenced,and phylogenetic analysis was conducted by Mega 5.0 software package.Results 849 ticks were collected from two tourist points,with the dominant ticks in Tiger Mountain and Jingpo Lake were Ixodes persulcatus and Haemaphysalis concinna.Regarding the Ixodes persulcatus from Tiger Mountain,the infection rates of B.b.s.1 and SFGR were 26.15％ and 10.05％.The infection rate of SFGR was 13.33％ in Haemaphysalis concinna and the B.b.s.1 was tndiscovered in the same ticks from Jingpo Lake.However,the co-infection could only be detected in Ixodes persulcatus of both tourist areas.Surveillance data showed that the major ticks were more likely to be appeared in July at Tiger Mountain and in June at Jingpo Lake.Data from the sequence analysis on B.b.s.1 showed that the B.b.s.1 in tourist areas could be classified into three different genotypes,other than B.garinii and B.afzelii.We first detected B.valaisiana-like group genotype in northeast of China.Results from the sequence analysis of SFGR positive products showed that the two DNA sequences of newly detected agents were completely the same as Rickettsia sp.HL-93 which was detected in Hulin and Rickettsia sp.H820 found in northeast,China.Conclusion The co-infection of B.b.s.1 and SFGR was detected in ticks from the tourist areas of Heilongjiang province,and data from the sequencing of specific fragment showed that various kinds of genotypes existed in this area.However; the rates of co-infectionitis-different according to environment,time and population that contributed to the kinds of and the index of ticks existed in the surveys points,also the infection rate of the ticks was studied.

Advances of mechanical stimulation induced calcium response and transfer in osteoblasts / 医用生物力学

Calcium is not only the important signaling molecule within and between bone cells, but also the primary component of extracellular matrix in bone. It has been demonstrated during the past over 100 years that mechanical stimulations can regulate the molecular signal transduction and intercellular communication in bone cells as well as the bone mineralization and resorption at tissue level, but further more researches are still needed to give insight into the mechanism of mechanical stimulation-induced bone remodeling. This paper will summarize the related works on the following aspects: (1) the primary experimental approaches for studying mechanical stimulation induced calcium response and transfer in osteoblasts, (2) the calcium sources and mechanism of calcium response in osteoblasts, (3) the intercellular calcium transfer pathways and (4) characteristic parameters of calcium response and transfer in osteoblasts. Finally, several potential research directions in this field are presented in the paper.

Calcium response in osteoblastic pattern without gap junction under flow shear stress / 医用生物力学

Objective To investigate the specific roles of gap junction and ATP in mechanical stimulation induced calcium transfer in osteoblasts. Methods The isolated osteoblastic pattern without gap junctions was established by using the micropatterning method. Then fluid shear stress was applied on cells using the flow chamber to observe and analyze the characteristic parameters of calcium response. Results Multiple calcium response still occurred in osteoblastic pattern without gap junction, but the response time to the first responsive peak was much longer than that with gap junction. When the intracellular and extracellular calcium ions were removed, only 40% cells responded to the mechanical stimulation, with single peak and multiple peaks accounting for 50%, respectively. If ATP pathway was blocked, only 20% cells responded, most of which showed single peak. Conclusions ATP was the major pathway mediating intercellular calcium transfer, while the gap junction was not the necessary one.

Measuring rupture forces of P-selectin/PSGL-1 bonds using an optical trap assay / 生物医学工程学杂志

Selectin/ligand interaction plays an important role in such biological processes as inflammatory reaction, tumor metastasis, etc. External forces affect dissociation of receptor-ligand bonds. A novel approach, upon optical trap technique, was developed in this study to investigate the dissociation of P-selectin/PSGL-1 (P-Selectin Glycoprotein Ligand 1) bindings. Stiffness of optical trap was calibrated with laser power using a viscous drag method. While P-selectin and PSGL-1 molecules were functionally coated on surfaces of glass beads, respectively, the dissociation of interacting molecule bond was studied by measuring the rupture force distribution. It was found that most probable rupture force increased with loading rate at < 25 pN/s. These results complemented and validated the current theory at low loading rates.

Two-dimensional finite element stress analysis of simulating restored teeth with wedge-shaped defects under loads / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To study the concentration of stresses at the cervix with simulating restoration of tooth defects.</p><p><b>METHODS</b>A two-dimensional finite element model of a mandible first premolar with defect from longitudinal section was developed. The model was simulatedly restored, respectively by composite resin and glass ionomer cement, and then investigated stress variation in the cervical area.</p><p><b>RESULTS</b>In the restored models, both of materials improved the concentration of stresses at the cervical area. The composite resin and the glass ionomer cement restorations made the maximum principal stresses declined respectively to 36.2 MPa and 42.5 MPa, which were close to the value of normal tooth in the deepest area of defects.</p><p><b>CONCLUSION</b>The concentration of stresses are improved in the cervical area with teeth defects restored.</p>