Abstract:Mechanics regulates biological processes at the molecular, cellular, tissue, organ, and organism levels. The studies of mechanobiology encompass several broad research areas including the mechanical environment in health, disease, or injury, the mechanosensitive responses and their mechanisms, the inter-relations between mechanics and biological processes such as growth, remodeling, adaption, and repair, and the discoveries that advance therapeutic and diagnostic procedures. The recent advances in cardiovascular mechanobiology in China were presented. The researches on cardiovascular mechanobiology are a study in search of principles of stress-growth in vasculature to bring out how are mechanical factors developing biological effect resulting in vascular remodeling, and the analytical and computational models based on solid mechanics, fluid mechanics, or thermomechanics, as well as new experimental methods that expand measurement capabilities and facilitate analysis for cardiovascular clinic. These studies will have very important theoretical and practical significance for understanding the mechanical mechanism of blood circulation, the nature laws of growth and senility of vasculature, expounding pathological mechanism of cardiovascular diseases, and the research and development of new medicines and technology in cardiovascular clinic.

Abstract:Objective The influence of shear stress on the assembly of microtubules in endothelial cells (ECs) was elucidated in the co-culture system with vascular smooth muscle cells to provide some experimental evidences for molecular mechanisms of shear stress-induced vascular remodeling. Methods The assembly of microtubules in ECs co-cultured with vascular smooth muscle cells (VSMCs) under shear stressof 15dyne/cm2- was examined by Western Blot, immunocytochemistry and image analysis. ECs were co-cultured with VSMCs under static conditions as a control. Results The microtubule arrangements in the control group showed sparsely, emanative and ruleless. After laminar shear stress (1.5Pa, 15dynes/cm2) applied to ECs co-cultured with VSMCs for 12h, a distinct change in microtubule arrangement appeared to the regular state and oriented to the direction of shear stress. Application of shear stress to the co-cultured ECs also promoted the quantitative assembly of microtubules in ECs. The polymeric tubulin mass became decreased in ECs after exposed to shear stress for 3 hours. Conclusions Shear stress induces and promotes microtubule assembly in the co-cultured ECs. Furthermore, these data suggest that microtubules could be a potential target for translating changes in externally applied mechanical stimulation to alterations in cellular phenotype and functions such as adhesion and migration.

Abstract:Objective To investigate the role of Akt/PKB activation induced by mechanical strain on vascular smooth muscle cell (VSMC) migration. Methods VSMCs of rat aorta were subjected tocyclic tensile strain (15%, 1Hz) by using a FX-4000T system, with VSMCs in static conditions as a control. VSMC migration and the phosphorylation of Akt/PKB were examined by Transwell assay and Western blot. Results Tensile strain (15%, 1Hz) obviously enhanced both VSMC migration and Akt/PKB activation compared with the control. While Wortmannin, a specific inhibitor of phosphatidylinositol-3 kinase, can attenuate the phosphorylation of Akt/PKB stimulated by the strain so as to reduce VSMC migration. Conclusion Akt/PKB activation could be enhanced by tensile strain to promote VSMC migration, and Akt/PKB involved in such VSMC migration via PI3K-Akt/PKB signaling pathway.

Abstract:Objective The mean wall shear stress (WSS) and circumferential stress (CS) in common carotid artery (CCA) for spontaneously hypertensive rats (SHRs) were investigated by comparing with those in wistar Kyoto rats (WKYs) to determine the characteristics of WSS and CS in CCA in SHRs. Methods Five twelve-week-old SHRs were chosen as an experimental group, with 5 WKYs of the same age as control. The blood pressure and flow rate in CCA were simultaneously measured in vivo, the morphological indices of CCA at no-load state, and the pressure (p)-volume (V) relationship of CCA in vivo under longitudinal stretch ratios were measured in vitro in SHRs and WKYs. Using these data, the mean WSS and CS in CCA in SHRs and WKYs were calculated. The obtained blood pressure and blood flow, the geometrical sizes at no-load and load states, and the mean WSS and CS were compared between SHRs and WKYs. Results The blood pressure in SHRs was significantly higher than that in WKYs, and the flow rate in SHRs was obvious lower than that in WKYs; Both the inner and outer radius at no-load/load state in SHRs were higher than those in WKYs, while the vascular wall thickness in SHRs was smaller than that in WKYs. The mean WSS in SHRs was significantly lower than that in WKYs while the CS in SHRs was significantly higher than that in WKYs. Conclusion High blood pressure and low flow rate may induce the vascular remodeling in CCA. Low WSS together with high CS is important hemodynamic characteristic of CCA. The synergistic action of WSS and CS might be one of the most sensitive indices reflecting arterial remodeling.

Abstract:Objective To investigate the adjustive tendency of cardiomyocytes’ morphological changes at low temperature. Method Compared the morphological changes of mcardiomyotytes cultured in low temperature (4 oC) with which cultured in normal temperature(37 oC), and detected cells’ interactions among cell colonies with inverted phase contrast microscope. Data were analyzed by imagine tool and mathematical statistic principles. Result (1) At the initial stages of low temperature culturing, cells assume obvious contraction with cell-cell clearance among cultured confluent cells and the orientation of clearances consistent with cell’s long axis; (2) at metaphase, present rounded or elliptical holes among the confluent cardiomyotytes; (3) at anaphase, the morphology, size and distribution of tensional holes tend to identical and cells turn to shank shape. Conclusion (1) low temperature may induce cells contract, destroy the cell-cell connection and result in histopathology; (2) Through the morphological changes and the cell-cell connective form’s regulation,Cardiomyocytes maximized the stabilization of the whole structure at low temperatures.

Abstract:Objective To investigate the effect of antiangiogenic factors : “Angiostatin” and “Endostatin” on tumor- induced angiogenesis. Methods A 2D discrete mathematical model of tumor-induced angiogenesis was built to simulate the growth of microvascular networks inside and outside of the tumor, with specific terms for endothelial cell proliferation, degradation, random motility, chemtaxis, haptotaxis and angiostatin and endostatin inhibitions. The effect of antiangiogenic factors: “Angiostatin” and “Endostatin” on tumor-induced angiogenesis were discussed. Results The antiangiogenic factor Angiostatin had inhibiting effects on the rates of growth and development of vascular networks inside and outside of the tumor. Endostatin together with Angiostatin could obviously inhibit tumor-induced angiogenesis ,and decreased the numbers of tumor blood vessels at medium-term and terminal stages of tumor vessels growth. Conclusion The inhibiting effects of angiostatin and endostatin on endothelial cell proliferation and migration can be simulated better by using the present model.

Abstract:Objective To improve the biomechanics properties of completely biological tissue engineered blood vessel (TEBV). Methods Porcine common carotid arteries were used to make the decellularised vascular scaffolds by enzyme digestion, and then the scaffolds seeded with VSMC from canine thoracic aorta were cultured in the vascular culture system, vascular bioreactor with automatic rotation and the effect of mimic pulsatile flow for 3 weeks in vitro, and EC from canine thoracic aorta were seeded subsequently on the scaffolds in the same way and cultured for one more week. After TEBV had been cultured over 4 weeks, the micro-structure of TEBV was examined by histological staining. Meanwhile, the ultrastructure of VSMC and EC in TEBV was also investigated by TEM and SEM. After that, the biomechanics properties of the TEBV were measure by a multi-function mechanical instrument. Results Well-proportioned distribution of VSMC was acquired on the scaffolds in the vascular culture system after 3 weeks. However, there was not such a perfect result even after seeding and culturing for 4 weeks without using the culture system. Endothelization of scaffoldswas achieved in 7 days by using the culture system, but not by using the common pressure perfusion method. The improved TEBV had a histological structure similar to normal physiological one. Normal physiological connections between cells could be found under TEM. Plentiful collagens were also found from seeded VSMCs. The biomechanics properties, including viscoelasticity of TEBV were similar to that of the physiological vessels. Conclusion Both VSMC and EC could adhere or develop into the decellularized scaffolds easier and sooner by using the improved vascular culture system with the effect of automatic rotation and hydromechanics. The improved TEBV presented the better histological structure and biomechanics properties that should be advantageous and significant for TEBV substitute to bear the effect of hydromechanics in vivo.

Abstract:Objective The paper discussed the preparation of human acellular amniotic membrane (HAAM), morphology and ability of releasing nitrous oxide (NO) and the adhesion after endothelial cells seeding on HAAM so as to offer an improved approach for preventing in-stent restenosis by making HAAM cover to modify intravascular stent and seed endothelial cells on it. Methods HAAM was prepared by removing the original epithelium by pancreatic enzymeas the substrate for human umbilical vein endotholical cells (HUVECs) seeded on it and its morphology, ability of releasing NO and the adhesion were examined. Results HUVECs were successfully seeded and could proliferate on HAAM, the monolayer was formed after cultivating 67 days. Their morphology, ability of releasing NO and the adhesion showed better than that of the endothelial cells of control. Conclusion HAAM can be used as a substrate for cultivating HUVECs and improving its function.

Abstract:Objectives To investigate if the radiographically quantifiable new bone would be able to serve as an non- destructive index for predicting healing quality of bone to tendon junction repair in a patella-patellar tendon complex. Methods An established partial patellectomy was performed on 15 mature female rabbits. Patella-patellar tendon (PPT) complex was harvested at 8 (n=7) and 16 weeks (n=8) post-operatively for evaluation of new bone size, length, bone mineral density (BMD), tensile force, strength and energy at failure. Results No significant differences were found in new bone size, length and BMD compared between week 8 and week 16. However, greater failure force, strength and energy were found in week 16 group than that of week 8 group (all p<0.05). The new bone size was found significantly correlated with failure force and strength (p<0.05 for both), but not the new bone length and BMD. Conclusion The findings of this study may suggest that the radiographically quantifiable new bone size formed from the remaining patella after partial patellectomy may serve as a useful non-destructive index in evaluation of the quality of direct bone-tendon repair within PPT healing complex.

Abstract:Objective To research a dynamic image measurement approach to aortic arch. Methods A dynamic tracing approach to aortic arch edge based on normal feature matching is presented. The edge of the first frame-image is detected by means of manual points selecting and curve fitting to overcome the shortcoming of incontinuous edge resulted from threshold image segmentation . Then a method based on normal feature matching is applied to detect the edge of sequential image of aortic arch. The smooth edge curve can be obtained by the proposed approach and realize the dynamic tracing of sequential image of aortic arch. Results The movement and deformation parameters of aortic arch are precisely measured by the proposed approach. Conclusion The study showed that the image measuring techniques could give quantitative analysis for the movement and deformation rule of the aortic arch in vivo successfully and provided a favorable base for finite element analysis of aortic arch.

Abstract:Objective In early stage of femoral head osteonecrosis, bone grafting in necrosis region are used to prevent collapse. This paper studied the influence on mechanical ability of bone defects in human femoral head’s weight bearing region and the restoration degree of mechanical ability after being planted by different structural bone. Methods Four normal proximal femur of human were harvested. Bone defects (20 mm in diameter and 30mm in depth) within the femoral heads’ principal weight-bearing region were drilled and the biomechanical properties of both the intact and the defected proximal femur were tested in vitro by simulating single-leg stance phase. Rigidity of the whole proximal femur and the strain value at the juncture of femoral head and neck under 1400N load were evaluated. And then, the bone defects were implanted with three different structural bone graftings. Group I was femoral head block allograft. Group II was femoral condyle block allograft. Group III was impacted with cancellous bone chips. The rigidity and the strain value were recorded same as above. Results Compared with the intact group, the strain of the top junction of femoral head and neck in defect group increased 93.0% and the strain of the bottom junction increased 203.4%. After implanted with different structural grafts and compared with the intact group, the strain of top conjunction of femoral head and neck increased 6.6% in group I, 33.7% in group II and 150.4% in group III,respectively, while the strain of bottom conjunction increased 67.6%, 136.9% and 206.1%. Conclusion Bone defects of the weight-bearing region in human femoral head would increase the strain distribution around the conjunction of femoral head and neck. The change of strain value would be found obviously in the top and bottom conjunction. After implanted with femoral head block allograft, the stress concentration could be lessened. However, there is no obvious improvement in biomechanical properties after implantedwith cancellous bone chips.

Abstract:Objective The effect of injection strategy on drug transport in 2D solid tumor were investigated to determine the suitable injecting method. Methods By using the tumor capillary network based on numerical angiogenesis, drug transport in a two-dimensional solid tumor was studied. The volume under the surface (VUS) of drug concentration when higher than minimum effective concentration (MEC) in tumor during 24 hours was choosed to evaluate the treatment of drug. Various drug injection methods were investigated and compared. Results When MEC is relatively low, there is not significant difference for various drug injection methods. Injecting drug in a short period would be more effective if MEC is relatively high. Conclusion The drug injection strategies for solid tumor therapy should be designed and optimized according to the characters of tumor cells and the effect of various typical drug injection-methods.

Abstract:Objective To study the stress of human femur under the bending moment and compressive load with considering accident twist or tumble happens to the human body in walk. Methods Adopted the Finite Element Method analysis software ANSYS. Based the trim size of human femur, develop plane model using plate42 cell. Excursion the load of node j to outside δ 0 mm、5 mm、10 mm、15mm passed by femur head, simulate the stress distributing of the femur head under the bending moment. Results Obtained the distortion deformation、stress nephogram、section stress of femur neck and upside of femoral shaft of the femur under the bending moment and compressive load. Conclusion There’s a large stress concentration at femur neck. The large tension stress is concentrated at the outside stress nephogram of femur neck, while the inside of it has large compressive stress. The outside of femoral shaft has large tension stress in perpendicular orientation, while the inside of it has large compressive stress. With the increase of bending moment, the stress of femur increases evidently.

Abstract:Objective A three dimensional finite element model after total hip replacement was established to analytically study the stress distribution of the artificial stem, bone cement and human femur. Methods The influence of the hollow shape and surface treatment of the stem on stress distribution of the prostheses and femur after total hip replacement was calculated and analyzed using 3-D reconstruction software, Pro/ Engineer software and ABAQUS finite element software. Results (1) The stress value of the cemented stem with a upside-down tapered hollow is lowest, and the proximal cement stress is lower. (2) Using the stem with the cement coat in the upper stem can reduce the stress of the proximal cement, the interface shear stress and relative slippage between the stem and cement. (3) The stress area in the human femur transfers down with the tiny-hole coating range in the uncemented stem increasing, so the proximal human femur stress descend. Conclusions (1) The use of upside-down tapered hollow stems to reduce proximal femur stress shielding could be profitable. (2) Using the stem with the cement coating in the upper stem can increase the adhesive strength at the interfaces with the stem and the cement, which is helpful to reduce prosthesis loosening of hip replacements. (3) The effects of the tiny-hole coating range of uncemented stems on the human femur stress are obvious, and the large tiny-hole coating range is disadvantageous tomaintaining suitable human femur stress and the stem fixation.

Abstract:Objective To research and develop the preoperative super-selection system for selecting proper prosthesis for patients. Methods This system integrates the latest achievements about hip prosthesis selection and analyse the characteristics of the hip prosthesis’ figure and size based on hip orthotopic radiograph to set up the super-selection regulations. This Hip Prosthesis Preoperative Super-selection System developed with both MATLAB and VB could be also used to evaluate the select results from geometry and stress aspects. Results To develop the preoperative super- selection system, the guides and the methods for this super-selection were established and evaluated. Conclusion The super-selection system can make the proper choice of hip prosthesis for patients according to femur characters of patient’s pelvis X-ray films.

Abstract:It is a trend for biomechanics development of spinal internal fixation device in the furture that how to attain fast fixation and retain maxiumum spinal movement function. The research and design of artificial anlanto-odontoid joint will be a feasible technique, which can not only rebuild the stability of atlanto-axial joint, but also reserve the rotation function between atlas and axis. This paper reviewed recent advancements on the biomechanics study of artificial anlanto- odontoid joint, with the focus on its design requirements and principles, implant feasible analysis and implant indication etc.

Abstract:Bone strength is dependent on bone quality. Bone material properties and micro-architecture are the important factors, which contribute to bone quality. In recent years, due to all kinds of micronano techniques and image proceeding application, much progress was made in studying micronano-mechanics of bone. Some of the advances were summarized in the following text.