Shaoxiong Yang, Ying‐Xin Qi, Zong-Lai Jiang, X. Gong
Vascular diseases during aging process are closely correlated to the age-related changes of mechanical stimuli for resident cells. Characterizing the variations of mechanical environments in vessel walls with advancing age is crucial for a better understanding of vascular remodeling and pathological changes. In this study, the mechanical stress, strain, and wall stiffness of the FPAs were compared among four different age groups from adolescent to young, middle-aged, and aged subjects. The material parameters and geometries adopted in the FPA models were obtained from published experimental results. It is found that high mechanical stress appears at different layers in young and old FPA walls respectively. The characteristics of the middle-aged FPA wall suggests that it is the most capable of resisting high blood pressures and maintaining a mechanical homeostasis during the entire life span. It is demonstrated that the variations of stress and strain rather than that of wall stiffness can be used as an indicator to illustrate the profile of FPA aging. Our results could serve as an age-specific mechanical reference for vascular mechanobiological studies, and allow further exploration of cellular dysfunctions in vessel walls during aging process.
{"title":"Characterizing the Mechanical Variations of Human Femoropopliteal Artery During Aging Process","authors":"Shaoxiong Yang, Ying‐Xin Qi, Zong-Lai Jiang, X. Gong","doi":"10.32604/MCB.2019.06096","DOIUrl":"https://doi.org/10.32604/MCB.2019.06096","url":null,"abstract":"Vascular diseases during aging process are closely correlated to the age-related changes of mechanical stimuli for resident cells. Characterizing the variations of mechanical environments in vessel walls with advancing age is crucial for a better understanding of vascular remodeling and pathological changes. In this study, the mechanical stress, strain, and wall stiffness of the FPAs were compared among four different age groups from adolescent to young, middle-aged, and aged subjects. The material parameters and geometries adopted in the FPA models were obtained from published experimental results. It is found that high mechanical stress appears at different layers in young and old FPA walls respectively. The characteristics of the middle-aged FPA wall suggests that it is the most capable of resisting high blood pressures and maintaining a mechanical homeostasis during the entire life span. It is demonstrated that the variations of stress and strain rather than that of wall stiffness can be used as an indicator to illustrate the profile of FPA aging. Our results could serve as an age-specific mechanical reference for vascular mechanobiological studies, and allow further exploration of cellular dysfunctions in vessel walls during aging process.","PeriodicalId":48719,"journal":{"name":"Molecular & Cellular Biomechanics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79806150","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wenjia Wang, Xiuqing Qian, Qi Li, Gong Zhang, Huangxuan Zhao, Tan Li, Yang Yu, Hongfang Song, Zhicheng Liu
Pupillary block is considered as an important cause of primary angle-closure glaucoma (PACG). In order to investigate the effect of pupillary block on the hydrodynamics of aqueous humor (AH) in anterior chamber (AC) and potential risks, a 3D printed eye model was developed to mimic the AH flow driven by fluid generation, the differential pressure between AC and posterior chambers (PC) and pupillary block. Particle image velocimetry technology was applied to visualize flow distribution. The results demonstrated obvious differences in AH flow with and without pupillary block. Under the normal condition (without pupillary block), the flow filed of AH was nearly symmetric in the AC. The highest flow velocity located at the central of AC when the differential pressure between AC and PC was under 5.83 Pa, while it appeared near the cornea and iris surface when the differential pressure was greater than 33.6 Pa. Once pupillary block occurred, two asymmetric vortices with different sizes were observed and the shear stress in the paracentral cornea and iris epithelium increased greatly. It can be concluded that the pupillary block and the elevated differential pressure between AC and PC could change the flow distribution and thus increase the risk of corneal endothelial cells detachment. This study could make a further understanding of the pathogenesis of PACG.
{"title":"Experimental Study of Aqueous Humor Flow in a Transparent Anterior Segment Phantom by Using PIV Technique","authors":"Wenjia Wang, Xiuqing Qian, Qi Li, Gong Zhang, Huangxuan Zhao, Tan Li, Yang Yu, Hongfang Song, Zhicheng Liu","doi":"10.32604/MCB.2019.06393","DOIUrl":"https://doi.org/10.32604/MCB.2019.06393","url":null,"abstract":"Pupillary block is considered as an important cause of primary angle-closure glaucoma (PACG). In order to investigate the effect of pupillary block on the hydrodynamics of aqueous humor (AH) in anterior chamber (AC) and potential risks, a 3D printed eye model was developed to mimic the AH flow driven by fluid generation, the differential pressure between AC and posterior chambers (PC) and pupillary block. Particle image velocimetry technology was applied to visualize flow distribution. The results demonstrated obvious differences in AH flow with and without pupillary block. Under the normal condition (without pupillary block), the flow filed of AH was nearly symmetric in the AC. The highest flow velocity located at the central of AC when the differential pressure between AC and PC was under 5.83 Pa, while it appeared near the cornea and iris surface when the differential pressure was greater than 33.6 Pa. Once pupillary block occurred, two asymmetric vortices with different sizes were observed and the shear stress in the paracentral cornea and iris epithelium increased greatly. It can be concluded that the pupillary block and the elevated differential pressure between AC and PC could change the flow distribution and thus increase the risk of corneal endothelial cells detachment. This study could make a further understanding of the pathogenesis of PACG.","PeriodicalId":48719,"journal":{"name":"Molecular & Cellular Biomechanics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89299155","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The contractile behavior of smooth muscle cells (SMCs) in the aorta is an important determinant of growth, remodeling, and homeostasis. However, quantitative values of SMC basal tone have never been characterized precisely on individual SMCs. Therefore, to address this lack, we developed an in vitro technique based on Traction Force Microscopy (TFM). Aortic SMCs from a human lineage at low passages (4-7) were cultured 2 days in conditions promoting the development of their contractile apparatus and seeded on hydrogels of varying elastic modulus (1, 4, 12 and 25 kPa) with embedded fluorescent microspheres. After complete adhesion, SMCs were artificially detached from the gel by trypsin treatment. The microbeads movement was tracked and the deformation fields were processed with a mechanical model, assuming linear elasticity, isotropic material, plane strain, to extract the traction forces formerly applied by individual SMCs on the gel. Two major interesting and original observations about SMC traction forces were deduced from the obtained results: 1. they are variable but driven by cell dynamics and show an exponential distribution, with 40% to 80% of traction forces in the range 0-10 µN. 2. They depend on the substrate stiffness: the fraction of adhesion forces below 10 µN tend to decrease when the substrate stiffness increases, whereas the fraction of higher adhesion forces increases. As these two aspects of cell adhesion (variability and stiffness dependence) and the distribution of their traction forces can be predicted by the probabilistic motor-clutch model, we conclude that this model could be applied to SMCs. Further studies will consider stimulated contractility and primary culture of cells extracted from aneurysmal human aortic tissue.
{"title":"Traction Force Measurements of Human Aortic Smooth Muscle Cells Reveal a Motor-Clutch Behavior","authors":"C. Petit, A. Guignandon, S. Avril","doi":"10.32604/mcb.2019.06415","DOIUrl":"https://doi.org/10.32604/mcb.2019.06415","url":null,"abstract":"The contractile behavior of smooth muscle cells (SMCs) in the aorta is an important determinant of growth, remodeling, and homeostasis. However, quantitative values of SMC basal tone have never been characterized precisely on individual SMCs. Therefore, to address this lack, we developed an in vitro technique based on Traction Force Microscopy (TFM). Aortic SMCs from a human lineage at low passages (4-7) were cultured 2 days in conditions promoting the development of their contractile apparatus and seeded on hydrogels of varying elastic modulus (1, 4, 12 and 25 kPa) with embedded fluorescent microspheres. After complete adhesion, SMCs were artificially detached from the gel by trypsin treatment. The microbeads movement was tracked and the deformation fields were processed with a mechanical model, assuming linear elasticity, isotropic material, plane strain, to extract the traction forces formerly applied by individual SMCs on the gel. Two major interesting and original observations about SMC traction forces were deduced from the obtained results: 1. they are variable but driven by cell dynamics and show an exponential distribution, with 40% to 80% of traction forces in the range 0-10 µN. 2. They depend on the substrate stiffness: the fraction of adhesion forces below 10 µN tend to decrease when the substrate stiffness increases, whereas the fraction of higher adhesion forces increases. As these two aspects of cell adhesion (variability and stiffness dependence) and the distribution of their traction forces can be predicted by the probabilistic motor-clutch model, we conclude that this model could be applied to SMCs. Further studies will consider stimulated contractility and primary culture of cells extracted from aneurysmal human aortic tissue.","PeriodicalId":48719,"journal":{"name":"Molecular & Cellular Biomechanics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82158192","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Cardiac pacing has been an effective treatment in the management of patients with arrhythmia. Different pacemaker location may have different impact on pacemaker effectiveness. A novel image-based ventricle animal modeling approach was proposed to integrate echocardiography images, propagating dynamic electric potential on ventricle surface to perform myocardial function assessment. The models will be used to simulate ventricular electrical signal conduction and optimize pacemaker location for better cardiac outcome. One health female adult pig weight 42.5kg was used to make pacing animal model with different ventricle pacing locations. Pig health status was assessed before undergoing experimental procedures. Ventricle surface electric signal, blood pressure and echo image were acquired 15 minutes after the pacemaker was implanted. Echo-based left ventricle (LV) fluid-structure interaction (FSI) models were constructed to perform ventricle function analysis and investigate impact of pacemaker location on cardiac outcome. The nonlinear Mooney-Rivlin model was used for ventricle tissue material model. With the measured electric signal map from the pig associated with the actual pacemaker site, electric potential conduction of myocardium was modeled by material stiffening and softening in our model, with stiffening simulating contraction and softening simulating relaxation. Material stiffness parameters were adjusted in a cardiac cycle to match Echo-measured LV deformation and volume variations. Mapping between material stiffness and ventricle electric signal was quantified using data measured from the animal with different pacemaker locations. Ventricle model without pacemaker and three ventricle models with the following pacemaker locations were simulated: right ventricular apex (RVA), posterior interventricular septum (PIVS) and right ventricular outflow tract (RVOT). Data for ventricle volume change, ejection fraction, stress and strain, flow velocity and shear stress data were collected for comparisons. Our results demonstrating that PIVS pacing model had higher peak flow velocity and stress/strain. It indicated that PIVS pacemaker site may be the best location. This modeling approach could be used as “virtual surgery” to try various pacemaker locations and avoid risky and dangerous surgical experiments on real patients.
{"title":"Echo-Based FSI Models to Simulate Ventricular Electrical Signal Conduction in Pig Pacemaker Models","authors":"Longling Fan, Jing Yao, Chun Yang, Di Xu, D. Tang","doi":"10.32604/MCB.2019.05720","DOIUrl":"https://doi.org/10.32604/MCB.2019.05720","url":null,"abstract":"Cardiac pacing has been an effective treatment in the management of patients with arrhythmia. Different pacemaker location may have different impact on pacemaker effectiveness. A novel image-based ventricle animal modeling approach was proposed to integrate echocardiography images, propagating dynamic electric potential on ventricle surface to perform myocardial function assessment. The models will be used to simulate ventricular electrical signal conduction and optimize pacemaker location for better cardiac outcome. One health female adult pig weight 42.5kg was used to make pacing animal model with different ventricle pacing locations. Pig health status was assessed before undergoing experimental procedures. Ventricle surface electric signal, blood pressure and echo image were acquired 15 minutes after the pacemaker was implanted. Echo-based left ventricle (LV) fluid-structure interaction (FSI) models were constructed to perform ventricle function analysis and investigate impact of pacemaker location on cardiac outcome. The nonlinear Mooney-Rivlin model was used for ventricle tissue material model. With the measured electric signal map from the pig associated with the actual pacemaker site, electric potential conduction of myocardium was modeled by material stiffening and softening in our model, with stiffening simulating contraction and softening simulating relaxation. Material stiffness parameters were adjusted in a cardiac cycle to match Echo-measured LV deformation and volume variations. Mapping between material stiffness and ventricle electric signal was quantified using data measured from the animal with different pacemaker locations. Ventricle model without pacemaker and three ventricle models with the following pacemaker locations were simulated: right ventricular apex (RVA), posterior interventricular septum (PIVS) and right ventricular outflow tract (RVOT). Data for ventricle volume change, ejection fraction, stress and strain, flow velocity and shear stress data were collected for comparisons. Our results demonstrating that PIVS pacing model had higher peak flow velocity and stress/strain. It indicated that PIVS pacemaker site may be the best location. This modeling approach could be used as “virtual surgery” to try various pacemaker locations and avoid risky and dangerous surgical experiments on real patients.","PeriodicalId":48719,"journal":{"name":"Molecular & Cellular Biomechanics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79423712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Caili Li, Jing Yao, Chun Yang, Di Xu, Liang Wang, D. Tang
Pulmonary valve stenosis (PVS) is one common post-operative problem in patients with tetralogy of Fallot (TOF) after repair. Congenital bicuspid pulmonary valve (BPV) is a condition of valvular stenosis, and the occurrence of congenital BPV is often associated with TOF. Compared with the biomechanical simulation model of the bicuspid aortic valve, the BPV is often neglected. In this study, we developed a dynamic biomechanical model of a simulated normal pulmonary root (PR) with tri-leaflet and a model of simulated PR with BPV in patients with repaired TOF in order to describe the effect of geometric structure with BPV on the stress and strain distribution. The geometry of PR included valvular leaflets, valsalva sinuses, inter leaflet triangle and annulus. Mechanical properties of PV leaflet were obtained from biaxial testing of human PV leaflet, and characterized by an anisotropic hyperelastic material model. Our model simulated complete cardiac cycles to observe valve leaflet dynamic stress/strain behaviors. Our results indicated that stress/strain distribution patterns of normal PV and the BPV were similar on pulmonary root and valve leaflets, but their values were different. When the valve was completely closed, maximum stresses were found leaflet attachment boundary, with their values at 17.1 kPa and 17.2 kPa respectively. When the valve was fully open, maximum stresses were found at the vicinity of commissures of sinus and leaflet, that is, near the annulus, with the values at 115.0 kPa and 143.0 kPa respectively. Compared with normal PR, the valve orifice area in the completely opened position in congenital BPV is significantly reduced. Our initial results demonstrated that geometrical variations with BPV may be a potential risk factor linked to occurrence of PVS in patients with repaired TOF. Computational models could be a useful tool in identifying possible linkage between valve disease development and biomechanical factors. Large-scale clinical studies are needed to validate these preliminary findings.
{"title":"Biomechanical Implications of Bicuspid Pulmonary Valve Dynamic Deformation in Patients with Repaired Tetralogy of Fallot","authors":"Caili Li, Jing Yao, Chun Yang, Di Xu, Liang Wang, D. Tang","doi":"10.32604/MCB.2019.05745","DOIUrl":"https://doi.org/10.32604/MCB.2019.05745","url":null,"abstract":"Pulmonary valve stenosis (PVS) is one common post-operative problem in patients with tetralogy of Fallot (TOF) after repair. Congenital bicuspid pulmonary valve (BPV) is a condition of valvular stenosis, and the occurrence of congenital BPV is often associated with TOF. Compared with the biomechanical simulation model of the bicuspid aortic valve, the BPV is often neglected. In this study, we developed a dynamic biomechanical model of a simulated normal pulmonary root (PR) with tri-leaflet and a model of simulated PR with BPV in patients with repaired TOF in order to describe the effect of geometric structure with BPV on the stress and strain distribution. The geometry of PR included valvular leaflets, valsalva sinuses, inter leaflet triangle and annulus. Mechanical properties of PV leaflet were obtained from biaxial testing of human PV leaflet, and characterized by an anisotropic hyperelastic material model. Our model simulated complete cardiac cycles to observe valve leaflet dynamic stress/strain behaviors. Our results indicated that stress/strain distribution patterns of normal PV and the BPV were similar on pulmonary root and valve leaflets, but their values were different. When the valve was completely closed, maximum stresses were found leaflet attachment boundary, with their values at 17.1 kPa and 17.2 kPa respectively. When the valve was fully open, maximum stresses were found at the vicinity of commissures of sinus and leaflet, that is, near the annulus, with the values at 115.0 kPa and 143.0 kPa respectively. Compared with normal PR, the valve orifice area in the completely opened position in congenital BPV is significantly reduced. Our initial results demonstrated that geometrical variations with BPV may be a potential risk factor linked to occurrence of PVS in patients with repaired TOF. Computational models could be a useful tool in identifying possible linkage between valve disease development and biomechanical factors. Large-scale clinical studies are needed to validate these preliminary findings.","PeriodicalId":48719,"journal":{"name":"Molecular & Cellular Biomechanics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76986117","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The prevalence of coronary bifurcation lesions (CBL) in the percutaneous coronary intervention (PCI) was reported to be approximately 15-20 % [Steigen (2006)]. The complex surgical techniques and the high incidence of restenosis make the treatment of CBL is still one of the most challenging fields in PCI. Even the single stent technique showed prognosis in most CBL treatment, dual stenting technique is still required in some cases. Our clinical follow-ups of dual stent implantation showed that the optimized provisional T-stenting (OPT) technique in CBL treatment has a lower restenosis rate compare with the Culotte stenting technique and T-stenting and small protrusion (TAP) technique. Though the local hemodynamic characteristics have been suggested as a key factor of the restenosis post PCI, the detailed hemodynamics features of the different dual stent implantation configurations are yet to be explored. In this study, the numerical simulations were performed to investigate the flow characteristics in coronary bifurcations with different dual stenting techniques.
{"title":"Numerical Investigation of the Hemodynamics Characteristics in Coronary Bifurcation Region with Different Dual Stent Implantation Techniques","authors":"Guangyu Zhu, Wei Cai, Q. Yuan, Lianglong Chen","doi":"10.32604/MCB.2019.05733","DOIUrl":"https://doi.org/10.32604/MCB.2019.05733","url":null,"abstract":"The prevalence of coronary bifurcation lesions (CBL) in the percutaneous coronary intervention (PCI) was reported to be approximately 15-20 % [Steigen (2006)]. The complex surgical techniques and the high incidence of restenosis make the treatment of CBL is still one of the most challenging fields in PCI. Even the single stent technique showed prognosis in most CBL treatment, dual stenting technique is still required in some cases. Our clinical follow-ups of dual stent implantation showed that the optimized provisional T-stenting (OPT) technique in CBL treatment has a lower restenosis rate compare with the Culotte stenting technique and T-stenting and small protrusion (TAP) technique. Though the local hemodynamic characteristics have been suggested as a key factor of the restenosis post PCI, the detailed hemodynamics features of the different dual stent implantation configurations are yet to be explored. In this study, the numerical simulations were performed to investigate the flow characteristics in coronary bifurcations with different dual stenting techniques.","PeriodicalId":48719,"journal":{"name":"Molecular & Cellular Biomechanics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76404424","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Caining Zhang, Xiaoya Guo, D. Tang, D. Molony, Chun Yang, H. Samady, Jie Zheng, G. Mintz, A. Maehara, M. Matsumura, D. Giddens
Cardiovascular diseases are closely associated with sudden rupture of atherosclerotic plaques. Previous image modalities such as magnetic resonance imaging (MRI) and intravascular ultrasound (IVUS) were unable to identify vulnerable plaques due to their limited resolution. Optical coherence tomography (OCT) is an advanced intravascular imaging technique developed in recent years which has high resolution approximately 10 microns and could provide more accurate morphology of coronary plaque. In particular, it is now possible to identify plaques with fibrous cap thickness < 65 µm, an accepted threshold value for vulnerable plaques. However, the current segmentation of OCT images are still performed manually by physicians and the process is time consuming. Automatic segmentation and recognition of vulnerable plaques through quantification of plaque components have great clinical significance for cardiovascular research. Two segmentation methods for intracoronary OCT image based on support vector machine (SVM) and convolutional neural network (CNN) were performed to detect the lumen borders and characterize the plaque component. In vivo IVUS and OCT coronary plaque data from 5 patients were acquired at Emory University with patient’s consent obtained. Seventy-seven matched IVUS and OCT slices with good image quality and medium to large lipid cores were selected for our segmentation study. Manual OCT segmentation was performed by experts and used as gold standard in the automatic segmentations. VH-IVUS was used as references and guide by the experts in the manual segmentation process. Three plaque component tissue classes were identified from OCT images in this work: lipid tissue (LT), fibrous tissue (FT) and background (BG). Procedures using two machine learning methods (CNN and SVM) were developed to segment OCT images, respectively. For CNN method, the U-Net architecture was selected due to its good performance in very different biomedical segmentation and very few annotated images. For SVM method, local binary patterns (LBPs), gray level co-occurrence matrices (GLCMs) which contains contrast, correlation, energy and homogeneity, entropy and mean value were calculated as features and assembled to feed SVM classifier. The accuracies of two segmentation methods were evaluated and compared using the OCT dataset. Segmentation accuracy is defined as the ratio of the number of pixels correctly classified over the total number of pixels. The overall classification accuracy based CNN method reached 95.8%, and the accuracies for LT, FT and BG were 86.8%, 83.4%, and 98.2%, respectively. The overall classification accuracy based SVM was 71.9%, and per-class accuracy for LT, FT and BG was 75.4%, 78.3%, and 67.0%, respectively. The two methods proposed can automatically detect the lumen borders and characterize the composition of the superficial plaque in OCT images and greatly reduce the time spent by doctors in segmenting and identifying plaques. CNN
{"title":"Automatic Segmentation Methods Based on Machine Learning for Intracoronary Optical Coherence Tomography Image","authors":"Caining Zhang, Xiaoya Guo, D. Tang, D. Molony, Chun Yang, H. Samady, Jie Zheng, G. Mintz, A. Maehara, M. Matsumura, D. Giddens","doi":"10.32604/MCB.2019.05747","DOIUrl":"https://doi.org/10.32604/MCB.2019.05747","url":null,"abstract":"Cardiovascular diseases are closely associated with sudden rupture of atherosclerotic plaques. Previous image modalities such as magnetic resonance imaging (MRI) and intravascular ultrasound (IVUS) were unable to identify vulnerable plaques due to their limited resolution. Optical coherence tomography (OCT) is an advanced intravascular imaging technique developed in recent years which has high resolution approximately 10 microns and could provide more accurate morphology of coronary plaque. In particular, it is now possible to identify plaques with fibrous cap thickness < 65 µm, an accepted threshold value for vulnerable plaques. However, the current segmentation of OCT images are still performed manually by physicians and the process is time consuming. Automatic segmentation and recognition of vulnerable plaques through quantification of plaque components have great clinical significance for cardiovascular research. Two segmentation methods for intracoronary OCT image based on support vector machine (SVM) and convolutional neural network (CNN) were performed to detect the lumen borders and characterize the plaque component. \u0000In vivo IVUS and OCT coronary plaque data from 5 patients were acquired at Emory University with patient’s consent obtained. Seventy-seven matched IVUS and OCT slices with good image quality and medium to large lipid cores were selected for our segmentation study. Manual OCT segmentation was performed by experts and used as gold standard in the automatic segmentations. VH-IVUS was used as references and guide by the experts in the manual segmentation process. Three plaque component tissue classes were identified from OCT images in this work: lipid tissue (LT), fibrous tissue (FT) and background (BG). Procedures using two machine learning methods (CNN and SVM) were developed to segment OCT images, respectively. For CNN method, the U-Net architecture was selected due to its good performance in very different biomedical segmentation and very few annotated images. For SVM method, local binary patterns (LBPs), gray level co-occurrence matrices (GLCMs) which contains contrast, correlation, energy and homogeneity, entropy and mean value were calculated as features and assembled to feed SVM classifier. The accuracies of two segmentation methods were evaluated and compared using the OCT dataset. Segmentation accuracy is defined as the ratio of the number of pixels correctly classified over the total number of pixels. \u0000The overall classification accuracy based CNN method reached 95.8%, and the accuracies for LT, FT and BG were 86.8%, 83.4%, and 98.2%, respectively. The overall classification accuracy based SVM was 71.9%, and per-class accuracy for LT, FT and BG was 75.4%, 78.3%, and 67.0%, respectively. \u0000The two methods proposed can automatically detect the lumen borders and characterize the composition of the superficial plaque in OCT images and greatly reduce the time spent by doctors in segmenting and identifying plaques. CNN ","PeriodicalId":48719,"journal":{"name":"Molecular & Cellular Biomechanics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84321782","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sheng-Liang Chen, Candra Ratna Sari, P. Segers, Guixue Wang, Xingshuang Ma
. Introduction Mitral valve is a complex structure including the annulus, the anterior leaflet, the posterior leaflet, the papillary muscles (PM), and the chordae tendineae connecting the leaflets and PM. The mechanical properties of the chordae play an important role in the normal functioning of the mitral valve: the chordae assists in maintaining the opening and closing configuration of the valve during cardiac cycle. Failure of certain chordae may lead to failure of the mitral valve and in severe cases, will lead to heart disease and mortality. In some cases, the ruptured chord need to be corrected by repair or replacement. Therefore, there has been high interest in the analysis of the function, mechanical properties and shape features of the mitral apparatus to improve the surgical effect. Chordae can be distinguished by leaflet location insertion as primary and secondary chordae. These finger-like chords connect the mitral valve to either anterolateral papillary muscle (APM) or posteromedial papillary muscle (PPM). The PPM has a higher risk to necrose and rupture in myocardial ischemia and infarction in clinic, but it is underlying mechanism is still unknown. Previous studies have shown importance in maintaining the asymmetric structure and realistic material property of the mitral valve for physiological load condition, but simplified the chord as symmetric structure, which is not true. In this study, the porcine heart chords were classified and measured according to the attached PMs. The uniaxial tensile test was utilized to analyze the biomechanical properties of the papillary muscle related chordae and histology observation was carried out for microstructure analysis. This study aims to analyze the anatomical and mechanical property differences in chords based on PMs which may help to understand the mitral valve function and to optimize the design of the artificial implantation or repair. Methods and materials Studies have shown that porcine valve was identified as an appropriate model for further investigation of the mitral valve system when considering the rarity of human valve. A total of 16 fresh porcine hearts were collected, infused in 4°C PBS buffer and infiltrated in physiological saline during the experiment, 9 of which were used for tensile testing, 6 for histological section staining, and 1 for TEM scanning. Based on insert position to PM (APM or PPM) and leaflets (primary on free edge and secondary on belly), the chord were divided into the APM primary chord, APM secondary chord, and PPM primary chord, and PPM secondary chord. The chords were separated from the valve, and the chordae diameter and length were measured via microscope, Markers were added at the target area of the chord for strain measurement. The sample was then fixed on an Instron1000 uniaxial tensile test machine with sandpaper. Before the experiment, the specimens were preload from 0N to2N until the displacement curves were substantially coincident
{"title":"Papillary Muscle Related Biomechanical Properties of Mitral Valve Chordae Tendineae","authors":"Sheng-Liang Chen, Candra Ratna Sari, P. Segers, Guixue Wang, Xingshuang Ma","doi":"10.32604/MCB.2019.05740","DOIUrl":"https://doi.org/10.32604/MCB.2019.05740","url":null,"abstract":". Introduction \u0000Mitral valve is a complex structure including the annulus, the anterior leaflet, the posterior leaflet, the papillary muscles (PM), and the chordae tendineae connecting the leaflets and PM. The mechanical properties of the chordae play an important role in the normal functioning of the mitral valve: the chordae assists in maintaining the opening and closing configuration of the valve during cardiac cycle. Failure of certain chordae may lead to failure of the mitral valve and in severe cases, will lead to heart disease and mortality. In some cases, the ruptured chord need to be corrected by repair or replacement. Therefore, there has been high interest in the analysis of the function, mechanical properties and shape features of the mitral apparatus to improve the surgical effect. \u0000Chordae can be distinguished by leaflet location insertion as primary and secondary chordae. These finger-like chords connect the mitral valve to either anterolateral papillary muscle (APM) or posteromedial papillary muscle (PPM). The PPM has a higher risk to necrose and rupture in myocardial ischemia and infarction in clinic, but it is underlying mechanism is still unknown. Previous studies have shown importance in maintaining the asymmetric structure and realistic material property of the mitral valve for physiological load condition, but simplified the chord as symmetric structure, which is not true. In this study, the porcine heart chords were classified and measured according to the attached PMs. The uniaxial tensile test was utilized to analyze the biomechanical properties of the papillary muscle related chordae and histology observation was carried out for microstructure analysis. This study aims to analyze the anatomical and mechanical property differences in chords based on PMs which may help to understand the mitral valve function and to optimize the design of the artificial implantation or repair. \u0000 \u0000 Methods and materials \u0000 \u0000Studies have shown that porcine valve was identified as an appropriate model for further investigation of the mitral valve system when considering the rarity of human valve. A total of 16 fresh porcine hearts were collected, infused in 4°C PBS buffer and infiltrated in physiological saline during the experiment, 9 of which were used for tensile testing, 6 for histological section staining, and 1 for TEM scanning. Based on insert position to PM (APM or PPM) and leaflets (primary on free edge and secondary on belly), the chord were divided into the APM primary chord, APM secondary chord, and PPM primary chord, and PPM secondary chord. The chords were separated from the valve, and the chordae diameter and length were measured via microscope, Markers were added at the target area of the chord for strain measurement. The sample was then fixed on an Instron1000 uniaxial tensile test machine with sandpaper. Before the experiment, the specimens were preload from 0N to2N until the displacement curves were substantially coincident","PeriodicalId":48719,"journal":{"name":"Molecular & Cellular Biomechanics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84909012","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Philip M. Tan, Kyle S. Buchholz, Shulin Cao, Y. Aboelkassem, J. Omens, A. McCulloch, J. Saucerman
In this article, we summarize our systems model of cardiomyocyte mechano-signaling published in PLoS Computational Biology and discuss new approaches to extending these models to predict cardiac myocyte gene expression in response to stretch.
{"title":"Systems Modeling of Cardiomyocyte Mechanobiology","authors":"Philip M. Tan, Kyle S. Buchholz, Shulin Cao, Y. Aboelkassem, J. Omens, A. McCulloch, J. Saucerman","doi":"10.32604/MCB.2019.05693","DOIUrl":"https://doi.org/10.32604/MCB.2019.05693","url":null,"abstract":"In this article, we summarize our systems model of cardiomyocyte mechano-signaling published in PLoS Computational Biology and discuss new approaches to extending these models to predict cardiac myocyte gene expression in response to stretch.","PeriodicalId":48719,"journal":{"name":"Molecular & Cellular Biomechanics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91334115","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jifeng Li, Yanting He, Xiaoyun Zhang, Hong Li, Xiumei Guan, Min Cheng, Xiaodong Cui
Objective The propose of the study is to investigate the specific effects of the mechanically sensitive channel Kir2.1 on the transdifferentiation of EPCs so as to understand the molecular mechanism of pathological vascular remodeling. Methods Endothelial progenitor cells (EPCs) were isolated from rat bone marrow and cultured in EGM2 medium in vitro. The recombinant lentiviral vectors carrying Kir2.1 (NM_017296.1) gene was designed and constructed in order to overexpress the gene. The smooth muscle cells (SMCs) molecules marker on EPCs, such as α-SMA, FSP1 and α-SM22, were detected by RT-PCR and cellular immunofluorescence. In addition, cell angiogenic capacity and migration in vitro were assessed by Matrigel and Transwell methods respectively. Moreover, neointimal thickening was evaluated in the surgery model of balloon injury of rat carotid artery in vivo. Result The results showed that the expression levels of α-SM22, FSP1 and α-SMA were up-regulated in the Kir2.1 overexpression group compared with the control. The number of migrating cells in the Kir2.1 overexpression group was significantly higher than that in the scramble group, while quantitative assessment further confirmed that the Kir2.1 overexpression strongly attenuated the ability of bone marrow-derived EPC to form tube-like structures in Matrigel assay. Compared with the control group, morphometric analysis showed ratio of intimal area/medial area (I/M) in rats was increased in rats transplanted with Lenti-Kir2.1 overexpression. Conclusion It is indicated that the overexpression of channel Kir2.1 induces EPCs transdifferentiated into mesenchymal transition SMCs (EndoMT). It may provide a potential target for the treatment or prevention of pathological vascular remodeling disease.
{"title":"Effect and Mechanism of Kir2.1 Channel Overexpression on Transdifferentiation of Endothelial Progenitor Cells","authors":"Jifeng Li, Yanting He, Xiaoyun Zhang, Hong Li, Xiumei Guan, Min Cheng, Xiaodong Cui","doi":"10.32604/MCB.2019.05753","DOIUrl":"https://doi.org/10.32604/MCB.2019.05753","url":null,"abstract":"Objective The propose of the study is to investigate the specific effects of the mechanically sensitive channel Kir2.1 on the transdifferentiation of EPCs so as to understand the molecular mechanism of pathological vascular remodeling. Methods Endothelial progenitor cells (EPCs) were isolated from rat bone marrow and cultured in EGM2 medium in vitro. The recombinant lentiviral vectors carrying Kir2.1 (NM_017296.1) gene was designed and constructed in order to overexpress the gene. The smooth muscle cells (SMCs) molecules marker on EPCs, such as α-SMA, FSP1 and α-SM22, were detected by RT-PCR and cellular immunofluorescence. In addition, cell angiogenic capacity and migration in vitro were assessed by Matrigel and Transwell methods respectively. Moreover, neointimal thickening was evaluated in the surgery model of balloon injury of rat carotid artery in vivo. Result The results showed that the expression levels of α-SM22, FSP1 and α-SMA were up-regulated in the Kir2.1 overexpression group compared with the control. The number of migrating cells in the Kir2.1 overexpression group was significantly higher than that in the scramble group, while quantitative assessment further confirmed that the Kir2.1 overexpression strongly attenuated the ability of bone marrow-derived EPC to form tube-like structures in Matrigel assay. Compared with the control group, morphometric analysis showed ratio of intimal area/medial area (I/M) in rats was increased in rats transplanted with Lenti-Kir2.1 overexpression. Conclusion It is indicated that the overexpression of channel Kir2.1 induces EPCs transdifferentiated into mesenchymal transition SMCs (EndoMT). It may provide a potential target for the treatment or prevention of pathological vascular remodeling disease.","PeriodicalId":48719,"journal":{"name":"Molecular & Cellular Biomechanics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88571408","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：