Abstract:

Abstract:Objective To study the role of cyclic strain-modulated tumor necrosis factor-α (TNF-α) played in the quantity and intercellular cell adhesion molecule-1(ICAM-1) expression of endothelial microparticles (EMPs). Methods The endothelial cells (ECs) primarily cultured from rat aorta were applied with 5% cyclic strain (to simulate normal physiological condition) and 18% cyclic strain (to simulate hyper-tension condition), respectively, by using FX-4000T cyclic stain loading system for 24 hours at the loading frequency of 1.25 Hz. The mRNA expression of TNF-α under different amplitudes of cyclic strain was determined by real time-PCR. The TNF-α was then used to stimulate the ECs from rat aorta, and the supernatants were collected and ultracentrifuged to get endothelial microparticles (EMPs), which were then identified by lipophilic styryl membrane staining and transmission electron microscope for morphological identification. The quantities of Annexin V positive EMPs under TNF-α stimulation were counted by flow cytometer and ICAM-1 expression on EMPs was detected as well. Results Compared with the 5% normal cyclic strain, under 18% high cyclic strain condition,the mRNA expression of TNF-α in ECs increased significantly. TNF-α could then significantly up-regulate the production of Annexin V positive EMPs and promote the expression of ICAM-1 on EMPs. Conclusions The over-expression of TNF-α in ECs under high cyclic strain might mediate the high production of EMPs and over-expression of ICAM-1 on EMPs. The research findings will provide new experiment evidence for further studying the role of EPCs in the mechanobiological mechanism of vascular remodeling.

Abstract:Objective To study the different effects from different concentration ratios of polymorphonuclear neutrophil (PMN) to tumor cell (TC) on the process of tumor cell adhesion to endothelial cell (EC) in shear flow. Methods PMNs and TCs with different concentration ratios (PMN-TC ratio) were added into the parallel plate flow chamber, and changes in the numbers of transient and accumulative adhered TCs on ECs at different shear rates (50 s-1，100 s-1，200 s-1) were analyzed. Results The transient and accumulative adhesion of TCs on ECs at PMN-TC ratio of 3︰1 significantly increased as compared to that at PMN-TC ratio of 1︰1, especially under high shear flow condition (100 s-1 and 200 s-1). Moreover, in the 5 minute-observation period, the effect of PMN-TC ratio on TC adhered to ECs occurred earlier when the shear rate increased. Conclusions The increase of PMN-TC concentration ratio can promote TC adhesion to ECs in shear flow, and the research findings provide significant references for studying TC metastasis in blood vessels and the target therapy of tumors.

Abstract:Objective To develop a musculoskeletal multi-body dynamic model of the patient-specific total knee replacement (TKR), and to simulate knee joint biomechanical characters of the patient during right-turn gait. Methods Based on the musculoskeletal dynamic software AnyBody and the method of force-dependent kinematics as well as the related data from a patient with TKR, the corresponding patient specific lower extremity musculoskeletal multi-body dynamic model was constructed and then used to simulate the right-turn gait of the patient. The knee contact forces, motion, muscle activations and ligament forces were predicted simultaneously by inverse dynamics analysis on such right-turn gait. ResultsThe root mean square error of the predicted average tibiofemoral medial contact force and lateral contact force were 285 N and 164 N, respectively, and the correlation coefficients were 0.95 and 0.61, respectively. The predicted average patellar contact force was 250 N. The predicted contact forces and muscle activations were consistent with those in vivo measurements obtained from the patient. In addition, the model also predicted the average range of tibiofemoral rotations of flexion-extension, internal-external, varus-valgus as 3°-47°, -3.4°-1.5°, 0.2°--1.5°, and the average range of tibiofemoral translations of anterior-posterior, inferior-superior, medial-lateral as 2.6-9 mm, 1.6-3.2 mm, 4.2-5.2 mm, respectively. The predicted average peak value of the medial, lateral collateral ligament force and posterior cruciate ligament force were 190, 108, 108 N, respectively. Conclusions The developed model can predict in vivo knee joint biomechanics, which offers a robust computational platform for future study on the failure mechanisms of knee prosthesis in clinic.

Abstract:Objective To propose a personalized design of anatomic ankle prosthesis that can avoid and reduce the high failure rate and risk of ankle prosthesis in clinic. Methods The 3D finite element non-linear model of normal human ankle system was established and verified. The anatomic ankle prosthesis was then designed to simulate total ankle replacement, and the 3D finite element model with both the prosthesis and ankle system was established. The biomechanical characteristics of this prosthesis were calculated and analyzed after gait loads were applied. Results For the normal ankle system, the maximum plantar contact stress was 214.6 kPa and the maximum Von Mises stress of foot bone was 8.96 MPa. The reliability of the normal ankle system model was verified by comparing the simulated results with those reported by literature. After the prosthesis implantation, the simulated maximum Von Mises stresses of talus prosthesis, tibial UHMWPE liner, tibial prosthesis were 23.88, 19.24 and 73.01 MPa, respectively. The stress of the ankle prosthesis increased drastically compared with that of normal ankle system. Conclusions The comparison results by finite element analysis examine the feasibility of the personalized ankle prosthesis, and provide references for optimization of prosthesis design and its clinical application.

Abstract:Objective To study biomechanical properties of two types of cylindrical nitinol stent-grafts under working condition of self-expanding, full deployment and bending, and analyze effects of structural change on biomechanical indexes of the grafts by numerical simulation methods. MethodsFirstly, the finite element models of two annular stent-grafts (i.e. stent-graft Ⅰ, stent graft Ⅱ, and a connecting rod was added to each stent unit of stent-graft Ⅱ for reinforcement) and target vessels were built. The stent-graft was transported to target vessel by delivery sheath, which was then removed to self-expand the stent-graft, and the contact between the vessel and the stent-graft was established. Secondly, the arterial pressure of 6.65-19.95 kPa (50 150 mmHg) was applied to inner surface of the stent-graft when the stent graft was fully deployed. Thirdly, the angular displacement was applied to both ends of the stent-graft to bend and deform the stent-graft. Finally, the maximum Von Mises stress (VMS) of the deformed vessel, the maximum principal strain (MPS), the maximum VMS and structural changes of the stent-graft were analyzed. ResultsFor both the stent-graft Ⅰ and Ⅱ, when they were self-expanding, the maximum VMS on the vessel was 0.349 MPa and 0.371 MPa, respectively; when they were fully deployed, the mean strain was 0.086% and 0.053%, the alternating strain was 0.049% and 0.027%, the maximum VMS on the membrane was 2.098 MPa and 2.430 MPa, respectively; when they were bent, the MPS was 0.069% and 0.101%, respectively, with more serious deformation on stent-graft Ⅰ. ConclusionsThe strain and stress of two stent-grafts under each working condition were less than their own material yielding limit. Stent-graft Ⅱ showed larger radial force in self-expanding, smaller strain under arterial pressure and better flexibility in bending deformation due to its connecting rod between each stent unit. These research results would provide an analysis method for structure design and material selection of the stent-graft, as well as a more intuitive and accurate technique guidance for intervention operation of the stent-graft in clinic.

Abstract:Objective To design a novel endoscopic successive hemostasis and closing device, and to validate whether the device can meet the needs of tissue closure by finite element analysis. Methods By using the novel device, the target tissue was clamped and the clip was then pushed to pierce the tissue. Under the compression between the clip and the inner side of the grasper, the thinner arms of the clip were forced to bend and close to stay in the tissue, and then the inverse displacement of 2 mm was applied on the clip. The elastic limit and tensile strength of the clip were set as 239.0 and 901.0 MPa, respectively. Results Deformation did not occur in the piercing process of the clip, with the maximum stress of 212.6 MPa. The deformed shape of the clip in the bending process matched its design expectation, with the maximum stress of 727.7 MPa. The maximum stress of the clip was 75.8 MPa under 2-mm inverse displacement. Material failure was not found in the bending process or with 2-mm inverse displacement, and the maximum stress in the whole process was 741.0 MPa. Conclusions The novel endoscopic successive hemostasis and closing device proposed in this study can deploy 4 clips at one time, together with an independent grasper for gathering tissues, which can shorten the reloading time and improve the accuracy of clip deployment. The effectiveness and safety of the device is also proved by using finite element method.

Abstract:Objective To investigate stress and bone density distribution changes in the mandible due to the interference fit in titanium dental implants for mandible reconstruction, and study the influence of interference magnitudes on mandibular bone remodeling. Methods Eight interference fit models with titanium implants were established by finite element method. Bone remodeling based on strain energy density (SED) algorithm was employed to investigate changes in stress and bone density of the mandible in the models during 36 months with inference magnitude of 5%, 10%, 15%, 20%, 25%, 30%, 35% and 40%, respectively. Results When the diameter of pilot hole was larger than the internal diameter of titanium screw, the increment of interference magnitude would gradually enhance the screw fixation at the bone titanium dental implant interface. However, once the magnitude of interference exceeded 30%, the increase in interference magnitude might weaken the screw fixation due to the failure and loss of bone. Conclusions The diameter of pilot hole equal to or slightly smaller than the internal diameter of titanium screw is recommended for mandibular reconstruction.

Abstract:Objective To investigate the effects from various angles between inferior vein cava (IVC) and right hepatic vein (RHV) on pathogenesis of IVC membranous obstruction for patients with Budd-Chiari syndrome (BCS). Methods The normal 3D solid model of IVC and hepatic veins was reconstructed using MRI angiograms, and the angle between IVC and RHV was 56°. The two models with IVC-RHV angle of 30° and 120° were established, respectively, based on the reconstructed model. The distributions of wall shear stress, static pressure and blood velocity of the 3 models were calculated by numerical simulation. Results The wall shear stresses, static pressure and blood velocity of the 3 models displayed significantly differences. Compared with the normal 56° model, the 30° model showed a higher wall pressure and lower blood velocity, while the 120° model presented a lower wall pressure and blood velocity with turbulence of blood flowing, and such hemodynamic changes would increase the risk of thrombosis. The 56° model had the fastest blood velocity. Conclusions Numerical simulation of the flow in IVC and RHV can promote to discover the pathogenesis of BCS, and help to predict risk of IVC membranous obstruction, and provide theoretical references for BCS treatment.

Abstract:Objective To investigate the mechanism of affinity down-regulation between Von Willebrand factor mutant G561S and its ligand. Methods Three molecular systems were constructed for WT-A1, G561S-A1, and R543Q-A1, respectively. G561S-A1 mutant was constructed by replacing the Gly561 with Ser561 in the wild-type A1 domain. The crystal structures of WT-A1 and R543Q-A1 were downloaded from Protein Data Base (PDB). Free molecular dynamics simulation was performed to observe the changes of conformation, alterations of flexibility, and the formation and evolution of hydrogen bond and/or salt bridge, among the three A1 domains (WT-A1, G561S-A1, and R543Q-A1). ResultsG561S mutation lowered the localized dynamic properties of α2 helix and increased the interactions between the N-terminal arm and body region in A1 domain, thus leading to the decreased binding affinity with its ligand GPIbα. However, the Gain-of-function mutation R543Q followed the pathway which was contrary to G561S. ConclusionsThe change of localized dynamic properties of α2 helix is a potential mechanism in the regulation of the binding affinity of A1, and this research finding is helpful in developing allosteric drugs against the activated A1 domain and relevant anti-thrombus drugs.

Abstract:Objective To investigate the phenomenon of amorphous carbon coating delamination during crimping and expansion of the vascular stent, and study how to avoid such phenomenon from both material selection and dimension design of the stent. Methods Amorphous carbon coatings were deposited onto a bare metal stent by chemical vapor deposition method, and then to simulate the crimping and expansion process of the stent. Coating delamination at different regions of the stent was observed by scanning with electron microscope, and the force mechanism and influencing factors related with amorphous carbon coating delamination during stent crimping and expansion were analyzed by finite element method. Results The finite element results could perfectly agree with the experimental results. The thickness of amorphous carbon coatings determined the complexity, as well as the formation pattern of coating delamination at different regions of the stent. Larger elastic modulus of amorphous carbon coatings could cause the formation of coating delamination much easier to occur. Besides, the stent modulus would also have some impact with different influencing patterns at different regions on coating delamination. Conclusions In order to avoid coating delamination, the thickness of amorphous carbon coatings should be carefully designed, and the elastic modulus of both amorphous carbon coatings and stents should be rationally selected.

Abstract:Objective To develop a mechanobiological model of bone remodeling based on stress state at cellular and molecular level. Methods Through analysis of bone remodeling process and mechanical stimulus from an engineering perspective, as well as absorption from the idea of mechanical strength design theory, the equivalent stress as the mechanical stimulus and the appropriate calculation formula of mechanical stimulus based on stress state were selected to propose a mechanobiological model of bone remodeling based on stress state at the cellular and molecular level. The model was then used to simulate bone remodeling of alveolar bone in orthodontics. Results The reduction of the vascular porosity and increase of bone mass appeared in tensile stress area, while vascular porosity increased and bone mass reduced in compression stress area, which was consistent with the features of alveolar bone. Conclusions The mechanobiological model of bone remodeling based on stress state at cellular and molecular level considered the effect of stress state on failure forms of bone tissues, embodied bone remodeling as a cellular automaton optimization process under mechanical stimulus, which would contribute to investigating effects of stress state on bone remodeling at the cellular and molecular level. The study is a supplement and improvement of bone remodeling theory and will provide theoretical guidance for treatment of orthodontics.

Abstract:Objective To investigate brain responses from children during traffic accident and drop impact by developing a 3-year-old child head finite element (FE) model. Methods Based on the CT data from a 4-year-old child head, the FE child head model with detaile

Abstract:Objective To propose the design of a pulsate blood pump driven by magnetic coupling and verify its feasibility. Methods The blood pump was designed based on the magnetic transmission reciprocating force model and the push-and-pull structure, and the coupling force was calculated by building the magnetic force-driven model. The prototype of the blood pump was then manufactured, on which the extracorporeal circulation simulation test was conducted to obtain the pressure and flow rate. Results Physiological saline was used as the circulation medium. When the afterload was fixed and increase the preload, the output of the blood pump would decrease, but showing no obvious linear trend. While the preload was fixed and increase the afterload, the output of the blood pump was reduced, showing a linear trend. With the driving frequency set as 75 per minute, and the preload and afterload adjusted in the range of 0.665-3.990 kPa (5-30 mmHg) and 5.320-11.970 kPa (40-90 mmHg), respectively, the output of the blood pump could reach 2.0-3.1 L/min while guaranteeing the linear relationship. Conclusions The proposed magnetic coupling-driven pulsate blood pump can basically meet the need of extracorporeal membrane pulmonary circulation, while it still needs further improvement. The research results have a valuable application prospect, especially with great significance in replacement of blood pump currently used in the extra-corporeal membrane oxygenation (ECMO) equipment in clinic.

Abstract:In recent years, computational fluid dynamics (CFD) has been widely used in fundamental and clinical researches of cerebral aneurysms. The research direction involves: ① the hemodynamic risk factors associated with initiation, evolution and rupture of cerebral aneurysms, ② the assessment of flow field changes in cerebral aneurysms after the implantation of coils and stent as well as the effect of such endovascular treatment by establishing the patient-specific models. This review elaborates the research progress in hemodynamics of cerebral aneurysms from 3 aspects: the development of CFD models, the morphological and hemodynamic parameters for rupture risk assessment of aneurysms and the role of CFD in the endovascular treatment of cerebral aneurysms.

Abstract:Objective To compare biomechanical properties of the helical and straight long PHILOS (proximal humerus internal locking system) plates (Synthes Inc., Switzerland), so as to provide some biomechanical evidence for treating proximal metaphyseal-diaphyseal humeral shaft fractures in clinic. Methods Twelve Synbone artificial bones of right humerus (SYNBONE Inc., Switzerland) were divided into two groups. In control group (n=6), the humerus was fixed with the 10 hole long straight PHILOS plate, while in experimental group (n=6), the humerus was fixed with the same long PHILOS plate which was precontoured for moulding (i.e. helical PHILOS plate). After the proximal metaphyseal-diaphyseal humeral shaft fractures were made in all artificial bones, the biomechanical properties of the specimens in two groups under 6 loading modes (i.e., axial tension and compression, torsion in the same and reverse direction, medial-lateral and anterior-posterior three-point bending) were tested en bloc and compared. ResultsCompare with control group, under 100-500 N tensile and compressive loads, the axial displacement at the fractured end in experimental group increased by about 95% and 58%, respectively. Under 0.6-3 N?m torsional moment in reversed direction, the tensional angle in experimental group was obviously smaller than that in control group, with a decrease of 55%-64%. Under medial-lateral bending moment of 1.5 and 3 N?m, no significant difference was found in deflection of the experiment and control group, while under medial-lateral bending moment of 4.5, 6 and 7.5 N?m, the deflection in experimental group decreased by 20% 30% as compared to control group. Under 0.6-3 N?m torsional moment in the same direction and 1.5-7.5 N?m anterior-posterior bending moment, both the torsional angle and the deflection in experimental group were larger than those in control group, with a significant difference (P＜0.05). Compared with control group, the tensile stiffness and compressive stiffness decreased by 49% and 36%, the torsional stiffness in the same direction decreased by 19% and that in reversed direction increased by 150%, three-point bending stiffness in medial lateral direction increased by 18% and that in anterior posterior direction decreased by 70% in experimental group, all with a significant difference (P＜0.05). ConclusionsCompared with the long straight PHILO plate, the long helical PHILOS plate has better biomechanical properties, which can meet the clinical need of proximal metaphyseal-diaphyseal humeral shaft fracture fixation and postoperative rehabilitation. This surgical technique is expected to be widely applied in clinic, especially with the advantage of minimal invasive surgery.

Abstract:There contains so much physiological/pathological information in pulse wave, which can reflect the early changes in cardiovascular function parameters. Therefore, it would be valuable to quantify the information revealed by pulse wave as important reference for cardiovascular diseases. In this review, the relationship between physiological/pathological information in cardiovascular system and pulse wave was described from the viewpoint of pulse wave formation mechanism, and to explain how the non-invasive detection indexes supplied by pulse wave could be applied in clinical use by analyzing the waveforms. Cardiovascular health evaluation index established by physiological/pathological information from cardiovascular system with pulse wave theory was also discussed. The development of non-invasive detection methods for cardiovascular system based on pulse wave theory can contribute to cardiovascular health care and provide important reference for the early detection, early prevention and early treatment of cardiovascular diseases. Besides, the non-invasive detection method can simplify the process of clinical testing and reduce the costs so as to achieve health assessment on cardiovascular diseases timely and reduce the mortality and disability rates.

Abstract:Inflammasome is a kind of multi-protein complexes which can mediate the release of several inflammatory cytokines such as IL-1β and thus plays an important role in the occurrence and development of inflammation. Along with the progressive researches on inflammasomes, recent literature has reported that inflammasomes might participate in some inflammatory diseases induced by mechanical forces. Meanwhile, recent studies have shown that mechanical forces can induce inflammation in periodontium, with the expression of IL-1β and caspase-1/-5. However, the role of inflammasomes and related proteins in periodontal inflammation has not been specified so far. In this article, the recent advances on characteristics of inflammasomes and their role in inflammatory diseases related to forces, as well as periodontal inflammation induced by mechanical forces and its relationship with inflammasomes and related proteins were reviewed.