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Biomechanics and Modeling in Mechanobiology

Zainab Altai, Marco Viceconti, Amaka C Offiah, Xinshan Li
Fractures of bone account 25% of all paediatric injuries (Cooper et al. in J Bone Miner Res 19:1976-1981, 2004. ). These can be broadly categorised into accidental or inflicted injuries. The current clinical approach to distinguish between these two is based on the clinician's judgment, which can be subjective. Furthermore, there is a lack of studies on paediatric bone to provide evidence-based information on bone strength, mainly due to the difficulties of obtaining paediatric bone samples...
March 10, 2018: Biomechanics and Modeling in Mechanobiology
Jorge Escribano, Raimon Sunyer, María Teresa Sánchez, Xavier Trepat, Pere Roca-Cusachs, José Manuel García-Aznar
Collective cell migration is regulated by a complex set of mechanical interactions and cellular mechanisms. Collective migration emerges from mechanisms occurring at single cell level, involving processes like contraction, polymerization and depolymerization, of cell-cell interactions and of cell-substrate adhesion. Here, we present a computational framework which simulates the dynamics of this emergent behavior conditioned by substrates with stiffness gradients. The computational model reproduces the cell's ability to move toward the stiffer part of the substrate, process known as durotaxis...
March 2, 2018: Biomechanics and Modeling in Mechanobiology
Michele Marino, Markus von Hoegen, Jörg Schröder, Peter Wriggers
Soft tissues are characterized by a nonlinear mechanical response, highly affected by the multiscale structure of collagen fibers. The effectiveness and the calibration of constitutive models play a major role on the reliability and the applicability of computational models in biomechanics. This paper presents a procedure for the identification of the relationship between collagen-related structural features in soft tissues with model parameters of classical polynomial- and exponential-based constitutive models...
February 28, 2018: Biomechanics and Modeling in Mechanobiology
Marissa R Grobbel, Sheikh Mohammad Shavik, Emma Darios, Stephanie W Watts, Lik Chuan Lee, Sara Roccabianca
We quantify the contribution of myocytes, collagen fibers and their interactions to the residual stress field found in the left ventricle (LV) using both experimental and theoretical methods. Ring tissue samples extracted from normal rat, male and female, LV were treated with collagenase and decellularization to isolate myocytes and collagen fibers, respectively. Opening angle tests were then performed on these samples as well as intact tissue samples containing both constituents that served as control. Our results show that the collagen fibers are the main contributor to the residual stress fields found in the LV...
February 24, 2018: Biomechanics and Modeling in Mechanobiology
J Vroon, J H de Jong, A Aboulatta, A Eliasy, F C T van der Helm, J C van Meurs, D Wong, A Elsheikh
Rhegmatogenous retinal detachment (RD) is a sight threatening condition. In this type of RD a break in the retina allows retrohyaloid fluid to enter the subretinal space. The prognosis concerning the patients' visual acuity is better if the RD has not progressed to the macula. The patient is given a posturing advice of bed rest and semi-supine positioning (with the RD as low as possible) to allow the utilisation of gravity and immobilisation in preventing progression of the RD. It is, however, unknown what external loads on the eye contribute the most to the progression of a RD...
February 24, 2018: Biomechanics and Modeling in Mechanobiology
Sofia André Dias, Emmanuelle Planus, Christelle Angely, Luc Lotteau, Renaud Tissier, Marcel Filoche, Bruno Louis, Gabriel Pelle, Daniel Isabey
During total liquid ventilation, lung cells are exposed to perfluorocarbon (PFC) whose chemophysical properties highly differ from standard aqueous cell feeding medium (DMEM). We herein perform a systematic study of structural and mechanical properties of A549 alveolar epithelial cells in order to characterize their response to PFC exposure, using DMEM as control condition. Changes in F-actin structure, focal adhesion density and glycocalyx distribution are evaluated by confocal fluorescent microscopy. Changes in cell mechanics and adhesion are measured by multiscale magnetic twisting cytometry (MTC)...
February 15, 2018: Biomechanics and Modeling in Mechanobiology
Shengmao Lin, Marsha C Lampi, Cynthia A Reinhart-King, Gary Tsui, Jian Wang, Carl A Nelson, Linxia Gu
Cell contraction regulates how cells sense their mechanical environment. We sought to identify the set-point of cell contraction, also referred to as tensional homeostasis. In this work, bovine aortic endothelial cells (BAECs), cultured on substrates with different stiffness, were characterized using traction force microscopy (TFM). Numerical models were developed to provide insights into the mechanics of cell-substrate interactions. Cell contraction was modeled as eigenstrain which could induce isometric cell contraction without external forces...
February 5, 2018: Biomechanics and Modeling in Mechanobiology
C Masri, G Chagnon, D Favier, H Sartelet, E Girard
This work aims at observing the mechanical behavior of the membranous and spongy portions of urethrae sampled on male cadavers in compliance with French regulations on postmortem testing, in accordance with the Scientific Council of body donation center of Grenoble. In this perspective, a thermostatic water tank was designed to conduct ex vivo planar tension tests in a physiological environment, i.e., in a saline solution at a temperature of [Formula: see text] [Formula: see text]. In order to observe the anisotropy of the tissues, the samples were tested in two directions...
January 29, 2018: Biomechanics and Modeling in Mechanobiology
Bahador Marzban, Xin Yi, Hongyan Yuan
Durotaxis refers to the phenomenon in which cells can sense the spatial gradient of the substrate rigidity in the process of cell migration. A conceptual two-part theory consisting of the focal adhesion force generation and mechanotransduction has been proposed previously by Lo et al. to explain the mechanism underlying durotaxis. In the present work, we are concerned with the first part of the theory: how exactly is the larger focal adhesion force generated in the part of the cell adhering to the stiffer region of the substrate? Using a simple elasticity model and by assuming the cell adheres to the substrate continuously underneath the whole cell body, we show that the mechanics principle of static equilibrium alone is sufficient to account for the generation of the larger traction stress on the stiffer region of the substrate...
January 22, 2018: Biomechanics and Modeling in Mechanobiology
Peta L Hitchens, Peter Pivonka, Fatemeh Malekipour, R Chris Whitton
In Thoroughbred racehorses, fractures of the distal limb are commonly catastrophic. Most of these fractures occur due to the accumulation of fatigue damage from repetitive loading, as evidenced by microdamage at the predilection sites for fracture. Adaptation of the bone in response to training loads is important for fatigue resistance. In order to better understand the mechanism of subchondral bone adaptation to its loading environment, we utilised a square root function defining the relationship between bone volume fraction [Formula: see text] and specific surface [Formula: see text] of the subchondral bone of the lateral condyles of the third metacarpal bone (MCIII) of the racehorse, and using this equation, developed a mathematical model of subchondral bone that adapts to loading conditions observed in vivo...
January 17, 2018: Biomechanics and Modeling in Mechanobiology
Maayan Lustig, Amit Gefen, Dafna Benayahu
Adipocyte fate commitment is characterized by morphological changes of fibroblastic pre-adipocyte cells, and specifically by accumulation of lipid droplets (LDs) as part of the adipogenesis metabolism. Formation of LDs indicates the production of triglycerides from glucose through an insulin-regulated glucose internalization process. In obesity, adipocytes typically become insulin resistant, and glucose transport into the cells is impaired, resulting in type 2 diabetes. In the present study, we monitored the adipogenesis in 3T3-L1 cultured cells exposed to high (450 mg/dL hyperglycemia) and low (100 mg/dL physiological) glucose concentrations, in a novel cell culture model system of diabesity...
January 15, 2018: Biomechanics and Modeling in Mechanobiology
J J Vaca-González, M Moncayo-Donoso, J M Guevara, Y Hata, S J Shefelbine, D A Garzón-Alvarado
Long bone formation starts early during embryonic development through a process known as endochondral ossification. This is a highly regulated mechanism that involves several mechanical and biochemical factors. Because long bone development is an extremely complex process, it is unclear how biochemical regulation is affected when dynamic loads are applied, and also how the combination of mechanical and biochemical factors affect the shape acquired by the bone during early development. In this study, we develop a mechanobiological model combining: (1) a reaction-diffusion system to describe the biochemical process and (2) a poroelastic model to determine the stresses and fluid flow due to loading...
January 10, 2018: Biomechanics and Modeling in Mechanobiology
Rodrigo Méndez Rojano, Simon Mendez, Franck Nicoud
Thrombosis is a major concern in blood-coated medical devices. Contact activation, which is the initial part of the coagulation cascade in device-related thrombosis, is not considered in current thrombus formation models. In the present study, pro-coagulant reactions including the contact activation system are coupled with a fluid solver in order to evaluate the potential of the contact system to initiate thrombin production. The biochemical/fluid model is applied to a backward-facing step configuration, a flow configuration that frequently appears in medical devices...
January 4, 2018: Biomechanics and Modeling in Mechanobiology
David Elad, Uri Zaretsky, Sharon Avraham, Ruthie Gotlieb, Michael Wolf, Itzhak Katra, Shlomo Sarig, Eli Zaady
Dust storms are common phenomena in many parts of the world, and significantly increase the level of atmospheric particulate matter (PM). The soil-derived dust is a mixture of organic and inorganic particles and even remnants of pesticides from agricultural areas nearby. The risk of human exposure to atmospheric dust is well documented, but very little is known on the impact of inhaled PM on the biological lining of the nasal cavity, which is the natural filter between the external environment and the respiratory tract...
January 4, 2018: Biomechanics and Modeling in Mechanobiology
Mohammad M Faghih, M Keith Sharp
Hemolysis is a persistent issue with blood-contacting devices. Many experimental and theoretical contributions over the last few decades have increased insight into the mechanisms of hemolysis in both laminar and turbulent flows, with the ultimate goal of developing a comprehensive, mechanistic hemolysis model. Many models assume that hemolysis scales with a resultant, scalar stress representing all components of the fluid stress tensor. This study critically evaluates this scalar stress hypothesis by calculating the response of the red blood cell membrane to different types of fluid stress (laminar shear and extension, and three turbulent shear and extension cases), each with the same scalar stress...
January 3, 2018: Biomechanics and Modeling in Mechanobiology
Alexander Synek, Dieter H Pahr
A micro-finite element-based method to estimate the bone loading history based on bone architecture was recently presented in the literature. However, a thorough investigation of the parameter sensitivity and plausibility of this method to predict joint loads is still missing. The goals of this study were (1) to analyse the parameter sensitivity of the joint load predictions at one proximal femur and (2) to assess the plausibility of the results by comparing load predictions of ten proximal femora to in vivo hip joint forces measured with instrumented prostheses (available from www...
December 30, 2017: Biomechanics and Modeling in Mechanobiology
Akinjide R Akintunde, Kristin S Miller
Tendon injuries are common to all ages. Injured tendons typically do not recover full functionality. The amount and organization of tendon constituents dictate their mechanical properties. The impact of changes in these constituents during (patho)physiologic processes (e.g., aging and healing) are not fully understood. Toward this end, microstructurally motivated strain energy functions (SEFs) offer insight into underlying mechanisms of age-dependent healing. Several SEFs have been adapted for tendon; however, most are phenomenological...
December 12, 2017: Biomechanics and Modeling in Mechanobiology
Pablo Gómez, Anne Schützenberger, Stefan Kniesburges, Christopher Bohr, Michael Döllinger
This study presents a framework for a direct comparison of experimental vocal fold dynamics data to a numerical two-mass-model (2MM) by solving the corresponding inverse problem of which parameters lead to similar model behavior. The introduced 2MM features improvements such as a variable stiffness and a modified collision force. A set of physiologically sensible degrees of freedom is presented, and three optimization algorithms are compared on synthetic vocal fold trajectories. Finally, a total of 288 high-speed video recordings of six excised porcine larynges were optimized to validate the proposed framework...
December 11, 2017: Biomechanics and Modeling in Mechanobiology
Quan Shi, Qiang Chen, Nicola Pugno, Zhi-Yong Li
Implantation of biodegradable scaffold is considered as a promising method to treat bone disorders, but knowledge of the dynamic bone repair process is extremely limited. In this study, based on the representative volume cell of a periodic scaffold, the influence of rehabilitation exercise duration per day on the bone repair was investigated by a computational framework. The framework coupled scaffold degradation and bone remodeling. The scaffold degradation was described by a function of stochastic hydrolysis independent of mechanical stimulation, and the bone formation was remodeled by a function of the mechanical stimulation, i...
December 8, 2017: Biomechanics and Modeling in Mechanobiology
Jeyendran Nadarasa, Caroline Deck, Frank Meyer, Nicolas Bourdet, Jean-Sébastien Raul, Rémy Willinger
Retinal hemorrhages (RH) are among injuries sustained by a large number of shaken baby syndrome victims, but also by a small proportion of road accident victims. In order to have a better understanding of the underlying of RH mechanisms, we aimed to develop a complete human eye and orbit finite element model. Five occipital head impacts, at different heights and on different surfaces, and three shaking experiments were conducted with a 6-week-old dummy (Q0 dummy). This allowed obtaining a precise description of the motion in those two specific situations, which was then used as input for the eye model simulation...
December 5, 2017: Biomechanics and Modeling in Mechanobiology
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