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Abstract:The mechanobiological mechanism in vascular homeostasis and vascular remodeling is one of the most important areas in stress-growth research, which is still unclear. Proteomics analysis, which is a high-throughput and systemic technic, is recently combined with biomechanics, bioinformatics and traditional molecular biology, and applied to demonstrate the mechanism of vascular remodeling induced by different kinds of mechanical stresses. These multidisciplinary and integrated technologies give new insights into understanding the mechanobiological mechanism of vascular remodeling and provide novel potential targets of clinical therapy on cardiovascular diseases. During recent years, the Institute of Mechanobiology & Medical Engineering of Shanghai Jiao Tong University has launched systematic researches with 3 steps: phenomenon exploration with mechanobiological experiments, bioinformatics analysis, and biological and experimental verifications, which established a potential mechanotransduction networks and more than 60 kinds of the novel mechanoresponsive molecules as well. Further researches were performed to demonstrate the role of these molecules in regulation of cellular functions under different kinds of mechanical stimuli. This paper reviews the recent progresses in vascular proteomics and the relative researches on mechanobiology. Researches based on mechanics-proteomics technics may contribute to the understanding of the pathogenesis of cardiovascular diseases, and provide novel therapeutic targets for vascular remodeling during hypertension and atherosclerosis.

Abstract:Objective To study the general mechanical behavior pattern of sensing angular velocity by 3 pairs of human semicircular canals. Methods Sinusoidal head rotation of a healthy subject was simulated by finite element method to analyze the dynamic responses in the above 3 pairs of canals in the left and right inner ear. Results Compared with the complicated node displacement distribution, the volumetric strain distribution of cupula was regular. Specifically, each pair of cupulae expanded or contracted within the same amplitude with the same response frequency to the angular velocity. The ratio of absolute volumetric strain among the horizontal semicircular canal cupula (HC cupula), the anterior semicircular canal cupula (AC cupula), and the posterior semicircular canal cupula (PC cupula), was approximately 1.00︰0.80︰1.72, which kept constant. In addition, the volumetric strain of HC cupula was in phase with that of AC cupula, but showing 14.4° out of phase with the angular velocity, and 180° out of phase with that of PC cupula. Conclusions The volumetric strain of cupula can preferably characterize the directional coding function of semicircular canal, and the amplitude, frequency and phase of the cupular volumetric strain can encode those of the stimulated angular velocity, respectively. These results will lay the foundation for establishing quantitative relationship of vestibulo-ocular reflex, and provide theoretical references for quantitative assessment for vestibular function by nystagmus examination.

Abstract:Objective To study the influence of noise under normal and high pressure environment on the cochlea, so as to make up for the defect caused by the lack of testing means to study the noise effect on behavioral characteristics of cochlear hearing by using numerical simulation method. Methods Based on CT scan images of healthy cochlea, and combined with self-programming, the three-dimensional finite element model of the cochlear spiral was established by using PATRAN software. Analysis on flow solid coupling frequency response and transient response was conducted by using NASTRAN software, and the impact of noise under normal and high pressure environment on the cochlea was numerically simulated. Results The calculated results were in agreement with the experimental results reported in the literature, which verified the correctness of the model. When the frequency was lower than 5 kHz, the basement membrane displacement by noise excitation under normal and high pressure environment was basically the same; when the frequency was higher than 5 kHz, the basement displacement by noise excitation under normal environment decreased gradually. Conclusions Under high pressure environment, the high-frequency noise shows a more obvious effect on the basilar membrane. The numerical simulation results can make up for the deficiency in studies about noise effect on characteristics of human cochlear hearing due to the lack of experimental methods, and provide new ideas and theoretical support for targeted experimental study of the cochlea in the future.

Abstract:Objective To design an improvement plan of piezoelectric actuator with displacement magnification structure, so as to reduce power consumption of the existing incus-stimulating piezoelectric actuator for middle ear implant. Methods First, based on anatomical structure of human ear, the piezoelectric actuator with displacement magnification structure and the one just composed of piezoelectric stack were designed, respectively, and the corresponding coupled mechanical models of the middle ear and the piezoelectric actuator were established. By comparing the calculation results from the two types of coupling mechanical models, the hearing compensation property and power consumption of the actuator before and after the implantation of displacement magnification structure were analyzed. Results After adding the displacement magnification structure, the sound pressure level (SPL) at 1 kHz frequency was increased from 100 dB to 113 dB, when the piezoelectric actuator was stimulated by 10.5 V effective voltage. In addition, when the actuator was stimulated by the piezoelectric stack, its power consumption at the frequency of 1, 2 and 4 kHz were 6.42, 1.56 and 0.28 mW, respectviely; after introducing the displacement magnification structure, power consumption at the above-mentioned 3 frequencies decreased to 0.39, 0.09 and 0.01 mW, resepectively. Conclusions Piezoelectric actuator with displacement magnification structure in this study can improve hearing compensation ability of the incus-stimulating middle ear implant and effectively reducing the power consumption. The research findings will help to further improve the structure design of middle ear implant, thus achieving better hearing compensation effect.

Abstract:Objective To determine the hyperelastic parameters shear modulus (μ) and curvature parameter (α) of extraocular muscles (EOMs) in Ogden hyperelastic model, so as to provide theoretical basis for clinical EOM surgery by numerical modeling. Methods The passive behavior of fox EOMs in vitro was determined by the uniaxial tensile test, and the hyperelastic analysis was conducted by the first-order Ogden model and ABAQUS software. Results The experimental result showed that the passive behavior of fox EOMs was nonlinear. The corresponding hyperelastic parameters μ =(6.57±3.76) kPa and α=8.16±1.63 were obtained. When the strain of EOMs was larger than 6%, there were no statistical differences between the experimental result and the calculation result of the first-order Ogden hyperelastic model (P>0.05). Both the calculation result and the simulation result well fitted to the experimental result. Conclusions The hyperelastic parameters identified in this study can be used as the input for the corresponding numerical modeling of fox EOMs.

Abstract:Objective To investigate the effects of inflation pressures on mechanical environment of pathological carotid after stent implantation. Methods The carotid artery models with lipid and calcified plaques were constructed based on high-resolution MRI images. The artery-stent interaction model was developed in the finite element software. Based on the models, the von Mises stress distributions on the vascular wall and plague under 3 different inflation pressures (909, 1212 and 1515 kPa) were simulated. Results High inflation pressure would induce large Von Mises stress on the artery-stent interface. Moreover, the stress on the lipid plaque increased significantly with the increase of inflation pressure. However, the differences in stress distributions on the calcified plaque were very small under different inflation pressure. Conclusions Higher inflation pressure may severely damage the lipid plaque and artery-stent interface after stenting, which will contribute to the failure of stent. This research finding may provide clinical guidance for the selection of inflation pressure for arterial stent deployment and the assessment of plague stability after stent implantation．

Abstract:Objective To investigate the role of cervical spine finite element model in predicting the risk of cervical ligament injury during Sanda combat (Chinese boxing), and compare the differences in mechanical responses of cervical ligaments after Baiquan (hook boxing) and Straight punches (cross boxing). Methods After 3D reconstruction of the head-neck osseous structure by using Mimics software based on CT images, an accurate head-neck finite element model was developed with HyperMesh software. The moment-ROM (range of motion) of the model and the head acceleration after punching were validated. Then differences in ligament force and distribution were compared between Baiquan and Straight punches under different punching forces (2.60, 3.30, 4.35 kN). Results The established head-neck model was validated to have good biofidelity, and the predicted values of head linear acceleration and rotational acceleration after punching were in agreement with those reported in the literatures. As the punching force increased from 2.6 kN to 4.35 kN, the maximum force in cervical ligament was 207, 265, 263 N in Baiquan, and 96.8, 91.4 and 101.4 N in Straight punch, which was located at atlantoaxial ligaments. Under the same force level, Baiquan generated greater force in cervical ligament than Straight punch. Conclusions Compared with Straight punch, cervical ligament injuries are more likely to occur in Baiquan during Sanda combat, and the established finite element neck-head model can be used in studies of biomechanical mechanism of Sanda-induced injuries, which may provide a more accurate reference for Sanda training and injury prevention.

Abstract:Objective To explore the biomechanical mechanisms of correlation between lumbar disc degeneration and sacroiliac joint disorder though investigating the biomechanical characteristics of lumbar disc degeneration with sacroiliac joint disorders. Methods One normal healthy volunteer and two patients with lumbar disc herniation and sacroiliac joint disorders (one was with sacrum disorders and the other was ilium disorders) were selected. Their CT data were collected to establish three corresponding lumbar-pelvis finite-element models, and their gait data were also simultaneously collected to drive the AnyBody musculoskeletal model. The muscle force around the lumbar and pelvis as well as the hip joint force were acquired as loading condition for finite element analysis. The stress changes in L4 and L5 intervertebral discs and sacroiliac joints of the patients and normal volunteer were compared. Results There was no significant difference in the stress of the two sides of L4, L5 disc and two sacroiliac joints in normal model, with a bimodal stress curve. However, in the models of sacrum disorders and ilium disorders, the bimodal stress curve peaks changed, even disappeared. The peak stress differences in left and right side of L4 disc were 0.55 MPa and 0.80 MPa, respectively, the peak stress differences in left and right side of L5 disc were 4.05 MPa and 2.08 MPa, respectively, and the peak stress differences in left and right side of sacroiliac joints were 0.96 MPa and 3.32 MPa, respectively. Conclusions The lumbar disc degeneration with sacroiliac joint disorder leads to the tilt of the body loading line, and sacroiliac joint disorder can aggravate the imbalances of stress on the body sides. The impact of sacroiliac joint dysfunction cannot be ignored in the treatment of lumbar disc herniation.

Abstract:Objective To analyze the torque performance of lingual brackets with slots in different directions and the influence pattern of arch wires with different sizes and materials on torque of these lingual brackets. Methods The finite element models of the anterior maxilla lingual brackets with vertical and horizontal slot were constructed, including three kinds of materials (stainless steel, beta-titanium, nickel-titanium) and two sizes of arch wires (0.43 mm×0.56 mm, 0.41 mm×0.56 mm), so as to compare and analyze their mechanical properties after the application of torque load on the left upper central incisors with a rotation angle of ±20°. Results With the increase in elastic modulus of the arch wire, torque moments of lingual brackets with horizontal and vertical slot both increased gradually. Torque performance of lingual brackets was affected more by the sizes and materials of arch wires than the directions of slots. The lingual bracket with vertical slot produced 1-2 times of torque force than that with horizontal slot under the same degree of torque angle. The effect of arch wire sizes was smaller than that of arch wire materials, while the synergistic change in sizes and materials of arch wires had the largest influence on torque performance of lingual brackets. Conclusion The lingual brackets with different slot directions, sizes and materials of arch wires will influence the torque performance of lingual brackets. In clinical application, slot directions of lingual brackets as well as sizes and materials of arch wires should be adjusted properly according to the required torque force.

Abstract:Objective To study the effects of different parameters (thickness, orthodontic displacement, elastic modulus) of Invisalign on canine displacement and periodontal ligament (PDL) stress during mandibular canine intrusion treatment. Methods Forty-eight different Invisalign models were used to simulate canine intrusion treatment by using the finite element method. Results The initial displacement of the canine and stress on canine PDL were proportional to thickness, intrusion displacement, and elastic modulus of Invisalign. The intrusion displacement had the greatest influence on canine displacement. During canine intrusion treatment, the compressive stress on PDL was the most sensitive parameter and changed easily with the change of parameters. Conclusions The increase of Invisalign thickness, intrusion displacement and elastic modulus can increase canine displacement, however, the stress on PDL also increases, with the largest increasing magnitude in compressive stress on PDL. Therefore, to accelerate tooth movement in Invisalign treatment, it is suggested to use the assisted devices or measurements, such as attachment, supplement of bracket-wires treatment, or implant anchorage.

Abstract:Objective To investigate the effect of fluid shear stress (FSS) on the expression of B lymphoma Mo-MLV insertion region 1 (Bmi-1) in bone mesenchymal stem cells (BMSCs) and possible signal transduction mechanism. Methods BMSCs were isolated from SD rats and FSS at different magnitude (0.5, 1.5, 3.0 Pa) and under different time phase (1, 2, 6, 24 h) were loaded by parallel-plate flow chamber system. The expression of Bmi-1 was measured by real-time RT-PCR at mRNA level and the levels of phosphorylated Akt (p-Akt) and extracellular signalregulated kinase 1/2 (p-ERK1/2) were detected by Western blotting. The signaling inhibitors, wortmannin (PI3K specific inhabitor) and PD98059 (ERK1/2 specific inhabitor), were used to investigate possible mechanical signal transduction pathway. Results Bmi-1mRNA expression increased when BMSCs were exposed to 1.5 Pa FSS for 1 h and reached the peak at 24 h. All FSS with different magnitude could increase Bmi-1 expression, especial at high FSS (3.0 Pa). Meanwhile, FSS resulted in a significant activation of p-Akt and p-ERK1/2 in BMSCs. After treated with wortmannin, the expression of Bmi-1 was inhibited prominently, however, PD98059, the expression of Bmi-1 did not change. Conclusions FSS can activate the expression of Bmi-1, the amount of Bmi-1 expression was closely related to the stimulating time and the magnitude of FSS, and Akt signal molecule plays an important role during the process. These findings provide significant references for studying the mechanical biological mechanisms of stem cell differentiation.

Abstract:Objective To investigate the structure and biomechanical property differences in different regions of the femoral head for elderly patients with femoral neck fractures, and to study its influence on internal fixation for fracture. Methods Twenty femoral head specimens were collected from elderly patients with femoral neck fracture after joint replacement. The femoral head was divided into 3 parts (lateral, inferior and medial region) with reference to anatomical markers on surface of the femoral head. After the position and drilling direction of the ring drill were determined, a circular drill was used to obtain the cylindrical cancellous bone columns with 10 mm in diameter and 10 mm in height. The data of cancellous bone columns in different regions were analyzed by Micro-CT scanning system, including bone volume fraction (BVF), trabecular space (Tb.Sp), trabecular thickness (Tb.Th), the number of trabecular number (Tb.N), the bone surface volume ratio (bone surface/bone volume, BS/BV), structural model index (SMI). Mechanical property differences of bone tissues in different regions were calculated by micro-finite element analysis. ResultsBone mass in the elderly osteoporotic femoral head decreased, and there were significant differences in bone microstructure and mechanical properties in different regions of the femoral head. Bone microstructure and mechanical properties in medial region were obviously superior to those in lateral and interior region. Conclusions The bone structure and mechanical strength in medial region of the femoral head are obvious superior to those in lateral and inferior regions. The position for internal fixation should be fully considered during treatment of osteoporotic femoral neck fracture in clinic.

Abstract:Objective To investigate the role and influence of physiological loading and overloading on microgravity-induced osteoporosis, so as to find a reliable way to prevent or treat related-orthopedic disorders in astronauts induced by long-time space activity. Methods The microgravity environment in space was simulated by tail-suspension experiment, then the osteoporosis models of mice were built. A total of 32 C57BL/6J mice were randomly and evenly separated into four groups: normal group (normal), tail-suspension group (TS), physiological loading group (loading) and overloading group (overloading). Periodic dynamic mechanical load was applied on the left tibia in loading group and overloading group during tail-suspension test. After four weeks, tibial mechanical properties, micro-parameters of bone trabecular, biochemical indices and osteogenesis-related gene expression in each group were compared and analyzed. Results A great loss of tibial cancellous bone, significantly lower tibial biomechanical expression, serious damage of microstructure and weaker osteogenic activity were found in tail-suspended mice as compared with those of normal group. Physiological loading could clearly improve mechanical properties of bones, microstructure of bone trabecular, osteogenic activity and relative gene expression (P＜0.05). Overloading could also improve the condition of microgravity-induced osteoporosis, but the effect was not obvious (P＞0.05). Conclusions Tail-suspension can successfully simulate microgravity environment and duplicate osteoporosis model. Physiological loading can effectively prevent the emergence and development of microgravity-induced osteoporosis, while overloading can also counter microgravity-induced osteoporosis, but the results have no significant differences.

Abstract:Objective To launch systematic research on long-term asymptomatic hyperuricemia (HUA) from hemorheological viewpoint, so as to provide references for clinical treatment of asymptomatic HUA. Methods Twenty rats were randomly and evenly divided into normal control group and model group. The rats were intraperitoneally injected with 250 mg/(kg?d) oxonate for 8 weeks to induce the model of asymptomatic HUA. The blood samples were obtained to measure the serum uric acid, hemorheological parameters, oxidative and anti-oxidative indices. Results The aggregation index, haemolysis rate, serum xanthine oxidase (XOD), plasma fibrinogen and blood viscosity significantly increased, while the orientation index, electrophoresis rate, serum superoxide dismutase (SOD), activated partial thromboplastin time (APTT) and prothrombin time (PT) significantly induced. Conclusions The asymptomatic HUA can lead to more serious oxidative stress, deteriorate the hemorheological parameters of red blood cells in rats, and induce higher blood viscosity and coagulation status. The research findings indicate that asymptomatic HUA should be correctly understood and timely intervened in clinical diagnosis.

Abstract:The function of health care and rehabilitation in Tai Chi has been recognized by the world. Studies on the mechanism of health care in Tai Chi have been conducted by domestic and international experts using the methods of sports biomechanics, most of which focus on human lower extremity. Twenty research literatures (15 articles in English and 5 articles in Chinese) during the year 2007-2015 about biomechanics of the lower extremity in Tai Chi were searched. According to the research purpose and evaluation index, this paper mainly reviewed from 3 aspects: the kinematic & kinetic characteristics of Tai Chi and its influence on the lower extremity, the effect of Tai Chi on muscle activity of the lower extremity, and the impact of Tai Chi movement on interaction between biomechanical parameters of the lower extremity and other system parameters. The prospects and limitations in biomechanical studies on the lower extremity in Tai Chi were also summarized.

Abstract:Orthodontic tooth movement is a dynamic process, which includes bone resorption on the pressure side and osteogenesis on the tension side. Bone mesenchymal stem cells (BMSCs), which are force-sensitive cells, have potentials for differentiation into cells with various types. Their biological characteristics can change functionally according to the appropriate stimulation in vitro, in order to reach the optimal demand of the stimulation. Many signal pathways are involved in osteogenesis. Signal transducers and activators of transcription 3 (STAT3) is a ubiquitously expressed transcription factor, mediating cell proliferation, differentiation, survival, apoptosis and cellular immunity. It has been reported that STAT3 can regulate the differentiation process of BMSCs into osteoblasts. This paper summarizes the recent progress about effect of STAT3 on bone differentiation of BMSCs and the possible mechanism.