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Abstract:An abdominal aortic aneurysm (AAA) is a vascular pathology associated with localized and balloon-like dilatations of abdominal aorta. An untreated AAA may lead to an eventual rupture with a high mortality rate. In recent studies, the biomechanics of AAA has been widely used to assess the rupture risk in clinic. In this review paper, biomechanical testing methods on intraluminal thrombi and AAA are discussed, so as to fully understand biomechanical properties of intraluminal thrombi and aneurysmal tissues, as well as the influence of mechanical property changes on the AAA growth and remodeling under pathological environment. Then representative research findings on prediction of rupture risk by a series of experimental and computational biomechanical methods are reviewed, including finite element analysis on stress distributions on AAA wall, assessment of rupture risk index and judgment of rupture locations. The relevant microstructural changes caused by thrombus aging are described in detail, and the current situation of biomechanical studies on AAA and future challenges are briefly summarized.

Abstract:There is an emerging and continuous interest in research about influence of biomechanics on repair and regulation of tissue injury. The development of tissue repair and regenerative medicine provides a new platform for biomechanical research, and biomechanics plays an important role in promoting the development of tissue repair and regenerative medicine. The papers published in special issue of biomechanics and tissue repair in Journal of Medical Biomechanics (Issue No. 5, 2016) were briefly analyzed and reviewed, and the researches in this field were also reviewed and prospected.

Abstract:Objective To investigate the effects of brusatol on mechanical properties of the cytoskeleton as well as the invasion behavior of rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS). Methods Cytoskeleton staining method was used to determine the regulatory effects of brusatol on mechanical properties of the RA FLS cytoskeleton. Transwell chamber assay was used to detect the effects of brusatol on the cytoskeleton and invasion behavior of RA FLS. The effects of brusatol on the expression of matrix metalloproteinase-2/3 (MMP-2/3) of RA FLS were measured by zymography and Western blotting methods. Results Cytoskeleton staining and microscope observation showed that brusatol could significantly reduce the formation number of RA FLS pseudopodia, thus inhibited cell movement ability via regulating mechanical properties of cytoskeleton. The invasion behavior of RA FLS was inhibited by brusatol, and brusatol could down-regulate the expression of MMP-2/3. Conclusions Brusatol plays an important role in regulating mechanical properties of cytoskeleton and inhibiting the invasion behavior of RA FLS. Meanwhile, brusatol can inhibit the invasion behavior of RA FLS through down-regulating the expression of MMP-2/3. The research findings provide the corresponding experimental basis for further development of new drugs for RA treatment.

Abstract:Objective To examine the effects of fluid shear stress (FSS) on epithelial-mesenchymal transition (EMT) in Hep2 cells. Methods Hep2 cells were exposed to 140 mPa FSS. The morphologic changes of Hep2 cells exposed to FSS at different durations were observed using inverted microscope. The migration ability of Hep2 cells after FSS loading was investigated using scratch wound assay. The distribution and expression of cytoskeleton protein F-actin were examined by confocal microscope. The expression of the EMT marker proteins were detected by Western blotting. Results Most of Hep2 cells changed their morphology from polygon to elongated spindle with well-organized F-actin under FSS. After removing FSS, Hep2 cells recovered their initial morphology with flat polygon. FSS regulated Hep2 cells to enhance their migration capacity in a time-dependent manner. FSS promoted the rearrangement of cytoskeletal protein F-actin，which enhanced the migration behavior of Hep2 cells. In addition, FSS induced a time regularity of expression of the EMT marker proteins in Hep2 cells. Conclusions FSS as an important physical factor can induce EMT in Hep2 cells.

Abstract:Objective To investigate the effect of lysophosphatidic acid (LPA) on migration of hepatocellular carcinoma MHCC97H cells and its involved mechanisms. Methods Transwell was utilized to investigate the impact of LPA on cell migration of MHCC97H cells. Furthermore, the role of ROCK in the migration of MHCC97H cells through Y-27632 (a specific inhibitor of ROCK). Then, the expression of F-actin was observed with immunofluorescence staining and Western blotting. Atomic force microscopy (AFM) was employed to investigate elastic modulus of MHCC97H cells. Results LPA significantly promoted the migration of MHCC97H cells, while Y-27632 significantly blocked the migration of MHCC97H induced by LPA. Moreover, LPA up-regulated the expression of F-actin and decreased the elastic modulus of MHCC97H cells. Conclusions LPA promotes MHCC97H cell migration through decreasing the cell stiffness via ROCK/F-actin.

Abstract:Objective To evaluate the effect of commonly used anti-adhesion products on the healing of abdominal muscles, and to provide guidance for surgeons to use anti-adhesion products in their clinical practice. Methods Adult SD rats were used. Except the sham group, surgical traumas were created on the serosal layer of the cecum and the underlying muscles of the abdominal wall. The wounds were covered without (Adhesion group) or with anti-adhesion products. Fourteen days after the surgery, the mechanical properties and histology of abdominal muscles were investigated to evaluate the healing of injured muscles. Results The ultimate tensile force and stiffness of the healing abdominal muscles in the groups of Polylactic acid membrane and Medical polyethylene glycol berberis lye were the same as those of normal muscles (P>0.05). The ultimate tensile force of the healing muscle in the groups of Chitosan gel and Seprafilm was significantly smaller than that of normal muscles (P<0.05). But their stiffness did not show any significant differences (P>0.05). The significant losses of mechanical properties of the healing muscles occurred in the Adhesion and Medical sodium hyaluronate gel group (P<0.05). HE staining indicated that more capillaries were found in Medical sodium hyaluronate gel, Polylactic acid membrane and Medical polyethylene glycol berberis lye group. The wound in Medical sodium hyaluronate gel group had less fibroblasts and fewer inflammatory cells, while the inflammatory cells were fully infiltrated with dense fibers in the other product groups. Conclusions Polylactic acid membrane and Medical polyethylene glycol berberis lye can promote abdominal muscle healing and are superior to Medical sodium hyaluronate gel, Chitosan gel and Seprefilm.

Abstract:Objective To realize the high-efficient capture of circulating tumor cells (CTCs) in the blood of tumor patients by analytic modeling and optimization on the herringbone micro-fluidic chip. Methods By simulating the fluid flow within the herringbone chip with Fluent 15.0 and calculating the capture efficiency with MATLAB to understand how geometric parameters (the herringbone groove width, spacing between herringbone grooves, herringbone groove height and channel height), flow rates and flow directions (forward flow, reverse flow) affected the cell-surface contact for capture of the CTCs, the capture efficiency was predicted and then validated by experiments. Results The herringbone micro-fluidic chip could achieve the optimal capture rate when the herringbone groove width, spacing between herringbone grooves, herringbone groove height and channel height were 75, 125, 70 and 30 μm, respectively, at a flow rate of 1 mL/h with forward direction. Conclusions In this study, cell capture in different micro-fluidic chips was simulated by the method of computational fluid dynamics. The statistic model of capture efficiency is established by MATLAB and optimized to quickly screen a group of physical parameters for high-efficient cell capture. These optimized micro-fluid chip parameters are validated by experiment, which can realize the high-efficient capture of CTCs.

Abstract:Objective To investigate the role of microRNAs (miRs) in the proliferation of vascular smooth muscle cells （VSMCs）induced by endothelial insulin-like growth factor-1 (IGF-1) under low shear stress (LowSS). Methods Endothelial cells (ECs) and VSMCs were co-cultured and exposed to normal shear stress (NSS, 1.5 Pa) and LowSS (0.5 Pa) for 12 h with parallel plate flow chamber system, respectively. Real-time PCR was used to examine the expression levels of miRs. The target genes of miR-133b were predicted by multiple algorithms. The expression of polypyrimidine tract binding protein 1 (Ptbp1) and N-myc downstream regulated 1 (Ndrg1) in VSMCs was detected by Western blotting. The VSMC proliferation was detected by EdU flow cytometry assay. Results After treated with recombinant IGF-1, the expression of both miR-133b and miR-378a in VSMCs was increased. Compared with NSS, LowSS significantly induced the expression of miR-133b in the co-cultured VSMCs, but had no obvious effect on miR-378a. In VSMCs, the protein and mRNA levels of Ptbp1 and Ndrg1 were down-regulated by miR-133b mimics. miR-133b inhibitor up-regulated the mRNA levels of Ptbp1 and Ndrg1. miR-133b overexpression promoted the proliferation of VSMCs significantly. Conclusions IGF-1 secreted by ECs in response to LowSS can upregulate the expression of miR-133b in the co-cultured VSMCs, which subsequently depresses the expression of Ptbp1 and Ndrg1, and induces the proliferation of VSMCs eventually. The research findings provide a potential new target for cardiovascular disease therapy.

Abstract:Objective To study the remodeling of alveolar bone and change in expression of forkhead box O1 (FOXO1) during orthodontic tooth movement (OTM) in rat, so as to preliminarily investigate the role of FOXO1 in alveolar bone remodeling induced by orthodontic force. Methods The rat OTM models were established and the left maxillary 1st molars were moved with force of 50 g. The rats were executed on the 1st, 3rd and 7th day of OTM, respectively. HE staining and immunohistochemical staining were used to observe the remodeling of alveolar bone in the inter-radicular region of the 1st molars and expression of FOXO1 at different time points during OTM. Results The 1st molars were constantly moved mesially under orthodontic force. There were more osteoclasts in the alveolar bone of OTM group than that in non-OTM group, and the osteoclasts on the 3rd day of OTM showed the highest activity. The number of active osteoblasts gradually increased in the inter-radicular region of alveolar bone under orthodontic force, with the enhanced osteoblast activity. Expression of FOXO1 in OTM group was elevated compared with non-OTM group. Most osteoblasts in alveolar bone during OTM were FOXO1 positive, and the expression of FOXO1 was gradually increased with the number of osteoblasts increasing. Conclusions Orthodontic force induces bone remodeling of alveolar bone in the inter-radicular region during OTM, and the change in FOXO1 expression may be related to alveolar bone remodeling during OTM.

Abstract:Objective To observe changes of surface electromyography (sEMG) in cervical traction under different loading weight and at different angles, and compare the muscle activity changes obtained by experiment with simulation results obtained by AnyBody cervical modeling, so as to verify the rationality of the simulation results. Methods Ten young volunteers with supine cervical traction were selected to test the sEMG signals of bilateral sternocleidomastoid (SCM) and upper trapezius (UT) muscles by using the JE-TB0810 surface EMG device. The average EMG (AEMG) and mean power frequency (MPF) were used to analyze the variation patterns of sEMG in cervical spine. Results The AEMG values of SCM and UT muscles increased as the loading weight and traction angles increasing, with a statistically significant difference (P<0.05). The AEMG values of UT muscles was higher than that of SCM muscles, also with a statistically significant difference (P<0.05). No statistical differences were found in the MPF values at different traction angles and under different loading weight for both SCM and UT muscles (P>0.05). The experimental results were consistent with muscle force activity characteristics of SCM and UT muscles by modeling and simulation of cervical traction. Conclusions The simulation results are reasonable. The traction weight should be loaded reasonably according to the excitation and fatigue of the cervical muscles in clinic. This can both reach the treatment effect and improve the patient’s comfort, which will provide an important reference for further development and improvement of the cervical traction device.

Abstract:Objective To investigate the coupling relationship between microcirculation loads and other arterial structure, so as to build a reasonable hemodynamic model. Methods Based on the two-way fluid-structure interaction hemodynamic model, a three-way fluid-structure-microcirculation load interaction hemodynamic model was built by considering the influence of microcirculation loads. Four cases were calculated according to different load and elastic modulus. The inlet condition was set as transient single pulse velocity inlet, and the outlet condition was set as free exit. Results The blood pressure always maintained within 80-120 mmHg (1 mmHg= 0.133 kPa) in the whole flow field. The diastolic pressure was finally raised to physiological blood pressure by increasing the total amount of the stored flow. With the increase of elastic modulus in vascular wall, the blood pressure maintained within 65-140 mmHg. With the increase of microcirculation resistance, the blood pressure maintained within 128-166 mmHg. Microcirculation load impeded the flow and reallocated the pressure in the artery. Conclusions It is necessary to consider the influence of microcirculation loads for construction of the hemodynamic model, which has an important clinical significance in analyzing pathogenesis of the circulatory system diseases.

Abstract:Objective To study effects from sand therapy of Uyghur medicine on hemodynamics in femoral artery branch and stress, so as to further discuss the functions and mechanisms of Uyghur sand therapy for treatment of femoral artery thrombosis formation. Methods Uyghur sand therapy was conducted on the subjects by indoor Uyghur sand therapy system. The peak values of blood flow velocity, inner diameter and resistance index (RI) of femoral artery before and after receiving Uyghur sand therapy were measured by the ultra-portable Doppler Diagnostic Ultrasound System for statistic analysis. Three-dimensional fluid-solid coupling model of femoral artery branch was reconstructed, and blood flow velocity, pressure, wall shear stress in the flow field as well as the equivalent stress, strain, total displacement on femoral artery wall were simulated and analyzed by the ANSYS Workbench. Results After receiving Uyghur sand therapy, the mean peak values of blood flow velocity and inner diameter of femoral artery increased by 32.43% and 2.68%, while the mean values of RI decreased by 4.88%, which showed it had the statistical difference(P<0.05).But no statistical difference was found in the inner diameter with or without Uyghur sand therapy (P>0.05).Besides, the maximum values of blood flow velocity, pressure and wall shear stress increased by 29.91%，68.51%,46.54%,respectively, while the maximum values of equivalent stress, equivalent strain, total displacement on femoral artery wall increased by 65.85%，45.45%，44%, respectively, after receiving Uyghur sand therapy. Conclusions Uyghur sand therapy can increase blood flow velocity and decrease RI obviously，and help to expand the inner diameter of femoral artery to make blood circulation inside improved. With Uyghur sand therapy, the shear stress, blood flow velocity, pressure as well as the stress, strain, total displacement on femoral artery walls also increase, meanwhile，high pressure area on femoral artery branch reduces to some extent, which shows it plays a certain positive role in reducing atherosclerosis and thrombus formation inside femoral artery.

Abstract:Objective To investigate the effects of gastrocnemius muscle forces on biomechanical mechanism of heel pain. Methods The finite element model of the foot including foot bone, soft tissues, ligaments and plantar fascia was reconstructed based foot CT images by Mimics software. The gastrocnemius force applied on the foot was 40%-90% of half-body weight（320 N） with increment of 5% of half-body weight（16 N）. The plantar surface pressure distribution and peak pressure as well as the plantar fascia stress were calculated. Results The plantar surface pressure distribution was mainly concentrated on the heel and metatarsal head. With the increase of gastrocnemius force, the peak plantar pressure at the heel decreased, while the peak pressure at the front of the foot decreased at first and then increased, which reached the minimum value with the load of 224 N. The plantar fascia stress increased with the gastrocnemius force increasing. Conclusions Gastrocnemius force applied on the foot has a significant influence on the plantar pressure distribution. Finite element analysis can contribute to understanding etiology and pathology of foot diseases, predicting the biomechanical results of the treatment and provide theoretical reference for treatments.

Abstract:Objective Aiming at reducing the restrictions on lower limbs imposed by traditional knee brace, a design scheme for knee brace complying with internal-external rotation is proposed. Methods By adding the internal-external hinge, the knee brace could help to release the degree of freedom (DOM) of internal-external rotation of the knee. In the experimental group, the subject was required to wear the bilateral unloading knee brace with or without internal-external hinges, respectively, while in the control group, the subject did not wear the knee brace. Then gait experiment and mechanical testing were conducted. Results In gait experiment, the bilateral unloading knee brace with internal-external hinges imposed less restriction on the knee than that from the knee brace without internal-external hinges, and it could also provide some distractive force for the knee joint. Conclusions The internal-external hinge design can help to reduce restrictions on the knee imposed from bilateral unloading knee brace.

Abstract:Objective To study the differences in physical characteristics of lacrosse balls and baseballs, so as to investigate the potential sports injuries caused by lacrosse balls. Methods Twelve lacrosse balls and 12 baseballs were used as testing samples. All testing balls were under conditioning control for 24 h to make sure temperature and humidity were consistent before measurement. The physical characteristics such as ball weight, circumference, compression-displacement and restitution coefficient were measured, respectively. Independent-sample t-test was used to compare the differences in lacrosse balls and baseballs. Results The lacrosse ball weighted (144.65±0.29) g, and its circumference, compression-displacement, and restitution coefficient were (19.97±0.02) cm, (91.76±1.23) kg and (0.633±0.011), respectively. The baseball weighted (146.12±0.45) g, and its circumference, compression-displacement and restitution coefficient were (23.20 ± 0.06) cm, (124.76±1.68) kg, and (0.528 ± 0.005), respectively. The lacrosse balls are significantly smaller in weight, circumference and compression-displacement than the baseballs (P<0.05). The restitution coefficient was significantly greater than baseballs (P<0.05). Conclusions The physical characteristics of lacrosse balls are in compliance with international standard. However, lacrosse balls have the same risk of causing serious injuries as baseballs. To reduce the risk of sports injuries, it is recommended that the specification of lacrosse balls need to be classified for different age and skill levels.

Abstract:The growth and metabolism of bone are controlled by osteogenesis of osteoblasts and absorption of osteoclasts, and osteoblasts play a main role in the process of osteogenesis. Overload will affect proliferation and differentiation of osteoblasts, while the loading mode, intensity, duration and other factors can change the biological properties of osteoblasts and further affect the functional activity of osteoblasts. However, the mechanism of osteoblast response to overload is still at the exploratory stage and needs in-depth study. Numerous studies have demonstrated that icariin, a kind of Chinese herbal medicine, can promote proliferation and differentiation of osteoblasts, and icariin with a certain concentration plays an important role in the repair of osteoblast injuries. In this paper, the response of osteoblasts to overload stimulation and repair of osteoblast injuries by icariin were summarized.

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.