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endothelialization
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Control of Blood Flow by Endothelial-Secreted Biochemicals NO, Ca2+ and Growth Factor VEGF: Numerical Simulation Using Lattice Boltzmann-Finite Difference Hybrid
, M.Sc. Thesis Sharif University of Technology ; Firoozabadi, Bahar (Supervisor)
Abstract
Endothelial cells that cover the inner wall of blood cells and are sensitive to receiving mechanical signals play important role in regulating many vital activities of the human body especially the function of the cardiovascular system. One of the factors affecting the mechanical functions of these cells is the shear stress applied to them. Due to blood velocity increasing or decreasing the endothelial cells shear stress change and leads to some chemical reactions and finally releasing biochemical substances including Nitrogen-Monoxide and Calcium-ion. Nitrogen-Monoxide produced by endothelial cells by affecting the smooth muscle cells in the vessel wall causes dilating of the vessel wall,...
Simulation of NO Production Process from Endothelial Cells and its Effect on Coronary Artery Flow Field
, M.Sc. Thesis Sharif University of Technology ; Firoozabadi, Bahar (Supervisor)
Abstract
Endothelial derived nitric oxide (NO) and its role in regulating the physiological conditions of blood vessels is one of the favorite topics among researchers. The majority of previous studies have focused on nitric oxide transport in blood vessels, less attention has been paid to its vasodilative effects in blood vessels. The main aim of this study is to propose an integrated model to study the effects of endothelial-derived nitric oxide on hemodynamic conditions of blood vessels. Nitric oxide is produced by endothelial cells upon exposure to mechanical forces such as hemodynamic shear stress. The synthesized nitric oxide then diffuses into the neighboring vascular smooth cells, where it...
Multiscale Modeling of Coronary Blood Flow and Effects on Endothelial Cells
, Ph.D. Dissertation Sharif University of Technology ; Saeedi, Mohammad Saeed (Supervisor) ; Firoozabadi, Bahar (Co-Advisor)
Abstract
Atherosclerosis in coronary arteries is one of the most important topics due to its high prevalence and the importance of these arteries for supplying blood to the heart. The morphology of endothelial cells (ECs) is an independent index for determining the atheroprone sites. The ECs show a regular elongated and aligned configuration to the blood flow, at the atheroprotected regions; on the other hand, at the atheroprone regions, the cells have a polygonal, randomly oriented morphology. The thesis intended to propose a method for coronary artery simulation, which is able to determine the atheroprone sites regarding the ECs morphology. In addition, the attempts were made to investigate the...
Simulation of the Blood Flow in a Stenotic Left Coronary Bifurcation to Study the Effects on the Endothelial Cells
, M.Sc. Thesis Sharif University of Technology ; Saeedi, Mohammad Saeed (Supervisor)
Abstract
Morphology and alignment of endothelial cells (ECs) have great influence on plaque formation. These alignments are based on the cyclic strains and wall shear stress (WSS) on the arterial wall. In the present study, cyclic strains and WSS are investigated to predict the secondary plaque locations downstream of the primary stenosis. Therefore, left coronary artery (LCA) with its branches to left anterior descending (LAD) and left circumflex (LCX) are 3D located on a virtual sphere to consider the cardiac motion. Stenoses are placed at the beginning of the bifurcation with varying degrees from 40% to 70% based on diameter reduction. Healthy coronary is also constructed to compare with those of...
Numerical Modeling of Endothelial Cell’s Groups Migration in a Microfluidics Device
, M.Sc. Thesis Sharif University of Technology ; Shamloo, Amir (Supervisor)
Abstract
Cell migration plays a key role in many biological processes including metastasis, wound healing, inflammatory response, body immune response and formation of new blood vessels. The migration of cells in response to the gradient of concentration gradient is regarded as chemotaxis. In the present study, the group chemotaxis of endothelial cells is simulated in response to gradient concentration of biochemical species using a developed cell migration model. At the first step, the numerical simulation of fluid flow and concentration transport of biochemical species is performed using a developed FVM code. At the second part, a model is developed to mimic the group migration of endothelial...
Simulation of Dynamic Behavior of Endothelial Cell During Compression Test
, M.Sc. Thesis Sharif University of Technology ; Saidi, Mohammad Said (Supervisor) ; Firoozabadi, Bahar (Supervisor)
Abstract
Investigation of the behavior of living cells in different biological conditions could play a key role in exploring the main reasons of humans' disorders and diseases. In this regard, many researchers are studying different subjects related to the living cells. Although most of these research activities are based on experimental methods, numerical approach could be utilized to investigate some topics which cannot be studied by experimental methods.In this study a three dimensional model of endothelial cell is proposed for the investigation of cell performance during compression test. The model consists of cell membrane, nucleus and main components of cytoskeleton, namely actin filaments,...
Simulation of a Simple Model of Endothelial Cell Using Dissipative Particle Dynamics Method
, M.Sc. Thesis Sharif University of Technology ; Saeedi, Mohammad Saeed (Supervisor) ; Firoozabadi, Bahar (Co-Advisor)
Abstract
Endothelium is the interior layer of an artery made up of tremendous number of endothelial cells which are located side by side. Finding the effective parameters that cause the cells to obtain mechanical strength in different morphologies is a major effort in cell engineering studies. In this work a numerical model for endothelial cells is developed. This model has included cell's plasma membrane (the outer membrane of the cell), nucleus and cytoskeleton main components including intermediate and actin filaments as well as microtubules. The model has been validated by simulating the adhesion of the cells to a flat substrate and also atomic force microscopy (AFM) experiments. The two most...
Investigation of Molecular Interactions of VEGFR and its Inhibitors by Molecular Dynamics Simulation
, M.Sc. Thesis Sharif University of Technology ; Bastani, Daruoosh (Supervisor) ; Mashayekhan, Shohreh (Co-Supervisor) ; Karami, Layla (Co-Supervisor)
Abstract
One of the chief kinds of receptors in cancer angiogenesis is the tyrosine kinase VEGFR-2. This target receptor is presented in both forms; active and inactive. adenosine triphosphate (ATP) residue is the location of deformational change from inactive to active form. Small molecule inhibitors have been designed for various forms of this receptor. In current study, the interaction of small molecular inhibitors including; Regorafenib, Cabozantinib and Thiosanib with dual VEGFR-2 receptor forms was investigated by molecular dynamics with Gromacs software. Cabozantinib and Regorafenib inhibitors had a lower binding energy in interaction with the inactive state however, Thiosanib inhibitors in...
Design and Fabrication of a Microfluidic Device to Study the Growth of Breast Cancer Cell
, M.Sc. Thesis Sharif University of Technology ; Vosughi, Manuchehr (Supervisor) ; Shamloo, Amir (Supervisor) ; Naserifar, Naser (Supervisor)
Abstract
for decades Cancer has been one of the major causes of death universally. Though extensive efforts in developing new anticancer therapies, they face failures in clinical trials and curing the sick owing to time consuming and expensive preclinical models with poor predictions of drug responses in human. To address this challenge it is crucial to develop preclinical models mimicking the main aspects of a tumor that can provide effective prediction of therapeutic responses. Tumor on chip technology has appeared as a promising approach for providing effective cancer models and reliable preclinical predictions. In this project, collagen was first extracted as the main constituent of the tumor...
VEGF Isolation from Platelet Lysate
, M.Sc. Thesis Sharif University of Technology ; Abdekhodaie, Mohammad Jafar (Supervisor)
Abstract
Platelet-rich plasma as a juvenile to the narrow repertoire of orthopedic medicine, has risen hope to attain a generic autologous regenerative formula for different conditions. Vast plethora of GFs, cytokines and chemokines has endowed PRP with excellent regenerative properties, however not all of them would favor different conditions. Vascular endothelial growth factor has been demonstrated to be involved in the progress of Osteoarthritis by amplifying the catabolic processes which deteriorate the extracellular matrix of cartilage. Though cumbersome, the result of eliminating VEGF from platelet lysate would be promising. VEGF isolation from platelet lysate requires selectivity. By employing...
Modeling the Relationship between Central Aortic Pressure and Radial Photoplethysmogram in Flow-mediated Dilation Test
, Ph.D. Dissertation Sharif University of Technology ; Vosughi Vahdat, Bijan (Supervisor) ; Zahedi, Edmond (Supervisor)
Abstract
According to the World Health Organization, about 35% of deaths worldwide are due to cardiovascular diseases, therefore the evaluation of vascular endothelial function has great prognostic and diagnostic value for cardiovascular diseases. The conventional noninvasive method for endothelial function evaluation is the measurement of flow-mediated dilation in brachial artery using ultrasound imaging (FMD-US). As the accuracy of FMD-US depends on the operator's skill and the resolution of the ultrasound images, this method has not been adopted. In this work, we propose to use a low cost, easily-accessible surrogate signal, the photoplethysmogram (PPG) to implement the FMD test. Whereas previous...
Modeling the Endothelial Function in the Brachial Artery Using Photoplethysmography
, M.Sc. Thesis Sharif University of Technology ; Zahedi, Edmond (Supervisor) ; Jahed, Mehran (Supervisor)
Abstract
Flow Mediated Dilation (FMD) is a non-invasive method for endothelial function assessment providing an index extracted from ultrasonic B-mode images. Although utilized in the research community, the difficulty of its application and high cost of ultrasonic device prevent it from being widely used in clinical settings. In this study we show that substituting the ultrasonic device with more easily handled and low cost photoplethysmography and electrocardiography is possible. We introduce new indices based on the photoplethysmogram (PPG) and electrocardiogram (ECG) and show that they are correlated with the ultrasound-based FMD index. To this end, conventional ultrasound FMD test was carried...
Analyzing the Endothelial Function by Means of Photoplethysmogram Signal Modeling
, M.Sc. Thesis Sharif University of Technology ; Zahedi, Edmond (Supervisor) ; Behnia, Fereidoon (Supervisor)
Abstract
The endothelial (the artery inner lumen cells) function is associated with cardiovascular risk factors. Its assessment methods can be classified into the two groups of invasive and noninvasive ones. The most widely used method among the current non-invasive tests employed in research settings is flow-mediated dilation (FMD). This technique measures endothelial function by inducing reactive hyperemia via the temporary arterial occlusion and measuring the resultant relative increase in the blood vessel diameter via ultrasound. The high price and large size of the device, and being operator dependent are the limitation of this method. In this work, we propose using the photoplethysmogram (PPG)...
Meaurement of Flow Mediated Dilation Using Photoplethysmography
, M.Sc. Thesis Sharif University of Technology ; Zahedi, Edmond (Supervisor)
Abstract
Endothelial cells cover the inner surface of blood vessels. In response to different physical (such as reactive hyperemia-RH) and pharmacological stimuli, they maintain homeostasis by changing the vascular diameter (by releasing chemical agents like nitric oxide). The endothelium inability to respond to metabolic need (endothelial dysfunction) is an early marker of cardiovascular diseases such as atherosclerosis. Flow mediated dilation (FMD) measurement using ultrasound imaging (FMD-US) has been established as a standard method for assessing the endothelial function. Recently, a less skilled-operator demanding method has been proposed based on the photoplethysmographic (PPG) signal changes...
Thickness as an important parameter in designing vascular grafts
, Article 2014 21st Iranian Conference on Biomedical Engineering, ICBME 2014 ; Nov , 2014 , p. 40-43 ; Shamloo, A ; Samani, S. A ; Dodel, M ; Sharif University of Technology
Abstract
The main goal of this study is to investigate the role of vascular graft thickness in wall stress gradient in anastomosis region. Atherosclerosis is a common heart disease causes high mortality rates every year. The gold standard treatment of atherosclerosis is replacing with autologous vein extracted from patient's body. Since proper autologous vein is limited, researchers have made efforts to achieve compliance engineered blood vessels. Mechanical stress has great effect on both smooth muscle cells and endothelial cells and it is considered as a stimulus in plaque formation. In this study, we evaluate the role of thickness in wall stress of anastomosis region. For this purpose, two...
Discrimination of bilateral finger photoplethysmogram responses to reactive hyperemia in diabetic and healthy subjects using a differential vascular model framework
, Article Physiological Measurement ; Volume 34, Issue 5 , 2013 , Pages 513-525 ; 09673334 (ISSN) ; Aghajani, H ; Zahedi, E ; Sharif University of Technology
2013
Abstract
Endothelial dysfunction assessment has received considerable attention due to its potential in early screening of cardiovascular diseases. Since the seminal work by Celermajer in flow-mediated dilation (FMD) based on B-mode ultrasound measurement of the brachial artery dilation following limb ischemia, many attempts have been made toward applying this method to clinical, non-invasive endothelial dysfunction assessment. One major obstacle toward achieving this objective has been the relative high cost of the required setup and skilled manpower. Such limitations have prompted the investigation of other non-invasively accessible signals such as the photoplethysmogram (PPG) in relation to FMD....
Modeling of photoplethysmography signal for quantitative analysis of endothelial cells during reactive hyperemia
, Article 2012 19th Iranian Conference of Biomedical Engineering, ICBME 2012 ; 2012 , Pages 174-178 ; 9781467331302 (ISBN) ; Firoozabadi, B ; Saidi, M. S ; Sharif University of Technology
2012
Abstract
In this study, at first the cardiovascular system is modeled based on the 1D method and then the simulation of the reactive hyperemia experiment has been applied on the model. In this simulation, by applying a cuff at the brachial artery, the flow downstream of the cuff is occluded. Then with releasing the cuff immediately, a large amount of shear stress, about 4 times the basal amount, is applied downstream of the cuff and consequently to the endothelial cells in a very short moment. Considering a reported experimental transfer function between shear stress and vasodilation, the increase of the artery diameter due to the sudden increase of the shear stress is obtained. Finally, the...
Autoregressive modeling of the photoplethysmogram AC signal amplitude changes after flow-mediated dilation in healthy and diabetic subjects
, Article 2012 19th Iranian Conference of Biomedical Engineering, ICBME 2012 ; 2012 , Pages 170-173 ; 9781467331302 (ISBN) ; Zahedi, E ; Behnia, F ; Sharif University of Technology
2012
Abstract
It is proved that the endothelial (artery inner lumen cells) function is associated with cardiovascular risk factors. Among all the common non-invasive methods employed in the research setting for assessing endothelial function, flow-mediated dilation is the most widely used one. This technique measures endothelial function by inducing reactive hyperemia using temporary arterial occlusion and measuring the resultant relative increase in blood vessel diameter via ultrasound. In this paper, the limitations associated with the ultrasound technique are overcome by using the photoplethysmogram (PPG) signal recorded during FMD. The correctness of this approach is investigated by modeling the AC...
Electrical analog model of arterial compliance during reactive hyperemia
, Article 2011 1st Middle East Conference on Biomedical Engineering, MECBME 2011, 21 February 2011 through 24 February 2011, Sharjah ; 2011 , Pages 49-53 ; 9781424470006 (ISBN) ; Zahedi, E ; Sharif University of Technology
2011
Abstract
Flow mediated dilation (FMD) measurement using ultrasound imaging (FMD-US) has been established as a standard method for assessing the endothelial function. Recently, a less skilled-operator demanding method has been proposed based on the photoplethysmogram (PPG) changes during reactive hyperemia. It was shown that the amplitude of the PPG pulse (FMD-PPG) changed in a quite similar manner to that of the artery diameter in the method of the FMD-US i.e. increases following releasing the cuff and then gradually returns to baseline. In this study PPG changes following reactive hyperaemia were modelled using time-varying passive electrical elements (R, L and C). The output of the electric analog...
Thickness as an important parameter in designing vascular grafts
, Article 2014 21st Iranian Conference on Biomedical Engineering, ICBME 2014, 26 November 2014 through 28 November 2014 ; November , 2014 , Pages 40-43 ; 9781479974177 (ISBN) ; Shamloo, A ; Samani, S. A ; Dodel, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2014
Abstract
The main goal of this study is to investigate the role of vascular graft thickness in wall stress gradient in anastomosis region. Atherosclerosis is a common heart disease causes high mortality rates every year. The gold standard treatment of atherosclerosis is replacing with autologous vein extracted from patient's body. Since proper autologous vein is limited, researchers have made efforts to achieve compliance engineered blood vessels. Mechanical stress has great effect on both smooth muscle cells and endothelial cells and it is considered as a stimulus in plaque formation. In this study, we evaluate the role of thickness in wall stress of anastomosis region. For this purpose, two...