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Investigating the Role of Smooth Muscle in Carotid Arteries: A Finite Element Analysis
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
(English)Article in journal (Other academic) Submitted
Abstract [en]

Vascular smooth muscle is a slow muscle, which reach isometric active steady-state force within minutes and it is not well known how this influence the active response in arteries that are loaded to cardiac pressure cycles that act within seconds. The role of active smooth muscle in larger arteries was investigated by studying how changes in intracellular calcium and medial wall thickness affect the deformation and transmural circumferential stress in arteries when loaded with cardiac pressure pulses. A three-dimensional finite element model of a two-layer carotid arterial ring was constructed using an implemented mechanochemical model of the active smooth muscle, which couples intracellular calcium to mechanical contraction together with a hyperelastic anisotropic model representing the elastin and collagen in the arterial ring. The material parameters was taken from previous work fitted to swine carotid artery. Residual stresses and strain in arterial ring were considered by closing an initial opening angle in the arterial ring. The simulation results of the arterial ring exposed to realistic pressure pulses and varying intracellular calcium waves with same period as the pressure pulses, showed that changes in intracellular calcium amplitudes did not have significant impact on the radial deformation and the transmural stress of the arterial ring. Increase in the mean value of the intracellular calcium waves as well as in the medial wall thickness showed to have a more significant effect on the behavior of the arterial wall.

National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:kth:diva-66778OAI: oai:DiVA.org:kth-66778DiVA: diva2:484617
Note
QS 2012. QS 20120328Available from: 2012-01-27 Created: 2012-01-27 Last updated: 2012-03-28Bibliographically approved
In thesis
1. Mechanochemical Modeling of Smooth Muscle Activation
Open this publication in new window or tab >>Mechanochemical Modeling of Smooth Muscle Activation
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Smooth muscle has an important role in several physiological processes, where it regulates the wall tension and the size of hollow organs. In blood vessels, the contraction and relaxation of smooth muscle contribute to the mechanical stability of the vessel wall and determines the diameter. To better understand how the active tone of smooth muscle influences the passive layers of the artery wall and how dysfunctions of the smooth muscle are related to pathologies such as hypertension and vasospasm, a coupled chemomechanical model based on structural studies and contractile behavior was proposed in this thesis. Smooth muscle contraction arises when cross-bridges between the myosin and actin filament cycle, causing sliding of the filaments. The contraction is triggered when myosin is phosphorylated by an influx of intracellular calcium ions, which can be initiated through different excitation-contraction pathways.

The proposed model coupled a chemical model, where intracellular calcium ion concentration was related to myosin phosphorylation and the fraction of load-bearing cross-bridges, with a mechanical model which was based on the three-element Hill model. The mechanical model, which described a sarcomeric equivalent contractile unit based on structural observations had been developed and modified in different steps to capture the characteristics of smooth muscle behavior, such as isometric contraction, isotonic shortening velocities and length-tension relationships. The chemical material parameters were fitted to calcium-phosphorylation data found in the literature and the mechanical model was fitted against experiments on swine common carotid media performed at Karolinska Instititet, Stockholm. The final coupled model was implemented into a three-dimensional finite element code to simulate the active tone in a two layered artery exposed to realistic pressure pulses. Simulation results indicated that changes in intracellular calcium amplitudes did not have significant effects while changes in the mean value of the intracellular calcium and in the medial wall thickness had a more significant effect on the mechanical response of the arterial wall.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. 34 p.
Series
Trita-HFL. Report / Royal Institute of Technology, Solid mechanics, ISSN 1654-1472 ; 0517
Keyword
Biomechanics, Muscle contraction, Smooth muscle, Contractile unit, Filament overlap, Intracellular calcium, Carotid artery, Mathematical model
National Category
Biological Sciences
Identifiers
urn:nbn:se:kth:diva-66780 (URN)
Public defence
2012-02-10, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20120127

Available from: 2012-01-27 Created: 2012-01-27 Last updated: 2013-01-14Bibliographically approved

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