laboratoire de physique statistique
 
 
laboratoire de physique statistique

Publications

Rechercher
 
2015
Growth and remodelling for profound circular wounds in skin - Wu, Min and Ben Amar, Martine
BIOMECHANICS AND MODELING IN MECHANOBIOLOGY 14357-370 (2015) 
LPS


Abstract : Wound healing studies both in vitro and in vivo have received a lot of attention recently. In vivo wound healing is a multi-step process involving physiological factors such as fibrinogen forming the clot, the infiltrated inflammatory cells, the recruited fibroblasts and the differentiated myofibroblasts as well as deposited collagens. All these actors play their roles at different times, aided by a cascade of morphogenetic agents and the result for the repair is approximatively successful but the imperfection is remained for large scars with fibrosis. Here, we want to study wound healing from the viewpoint of skin biomechanics, integrating the particular layered geometry of the skin, and the role of the neighbouring wound epidermis. After 2 days post-injury, it migrates towards the wound centre to cover the hole, the migration being coupled to proliferation at the wound border. Such a process is dominated by the skin properties which varies with ages, locations, pathologies, radiations, etc. It is also controlled by passive (actin, collagen) and active (myo-fibroblasts) fibres. We explore a growth model in finite elasticity of a bilayer surrounding a circular wound, only the interior one being proliferative and contractile. We discuss the occurrence of an irregular wound geometry generated by stresses and show quantitatively that it results from the combined effects of the stiffness, the size of the wound, eventually weakened by actin cables. Comparison of our findings is made with known observations or experiments in vivo.
Osmotic stress affects functional properties of human melanoma cell lines - La Porta, Caterina A. M. and Ghilardi, Anna and Pasini, Maria and Laurson, Lasse and Alava, Mikko J. and Zapperi, Stefano and Ben Amar, Martine
EUROPEAN PHYSICAL JOURNAL PLUS 130 (2015) 
LPS


Abstract : Understanding the role of microenvironment in cancer growth and metastasis is a key issue for cancer research. Here, we study the effect of osmotic pressure on the functional properties of primary and metastatic melanoma cell lines. In particular, we experimentally quantify individual cell motility and transmigration capability. We then perform a circular scratch assay to study how a cancer cell front invades an empty space. Our results show that primary melanoma cells are sensitive to a low osmotic pressure, while metastatic cells are less. To better understand the experimental results, we introduce and study a continuous model for the dynamics of a cell layer and a stochastic discrete model for cell proliferation and diffusion. The two models capture essential features of the experimental results and allow to make predictions for a wide range of experimentally measurable parameters.
Modelling fibers in growing disks of soft tissues - Wu, Min and Ben Amar, Martine
MATHEMATICS AND MECHANICS OF SOLIDS 20663-679 (2015) 
LPS


Abstract : Despite its simple geometry and pertinence to biological systems, the growth of soft tissue disks has not been studied systematically in finite elasticity. Here with this simple geometry, we perform theoretical studies of constitutive laws concerning fibrous samples in growth or atrophy. Considering the radial growth of an incompressible neo-Hookean disk of matter, reinforced by fibers, we focus on the possible shape bifurcation from the circular to the wavy geometry. By analytical means based on a variational formulation of the theory of elasticity with growth we show that the radial geometry is lost for a critical growth anisotropy coefficient which plays the role of a control bifurcation parameter. Above a threshold which depends on the fiber invariants, the border of the disk becomes undulated with selection of a low wavenumber for low anisotropic coefficient. Radially or circumferentially oriented fibers favor undulations, but not intermediate cross-linked fibers, which inhibit undulations. Our systematic analysis shows the key role of the anisotropic growth coefficient as well as the fiber orientation for the observation of undulated patterns. Such models can explain experimental observations for skin tumors, biofilms and yeast colonies.
Morphogenesis of early stage melanoma - Chatelain, Clement and Ben Amar, Martine
EUROPEAN PHYSICAL JOURNAL PLUS 130 (2015) 
LPS


Abstract : Melanoma early detection is possible by simple skin examination and can insure a high survival probability when successful. However it requires efficient methods for identifying malignant lesions from common moles. This paper provides an overview first of the biological and physical mechanisms controlling melanoma early evolution, and then of the clinical tools available today for detecting melanoma in vivo at an early stage. It highlights the lack of diagnosis methods rationally linking macroscopic observables to the microscopic properties of the tissue, which define the malignancy of the tumor. The possible inputs of multiscale models for improving these methods are shortly discussed.
Faraday instability in floating drops - Pucci, G. and Ben Amar, M. and Couder, Y.
PHYSICS OF FLUIDS 27 (2015) 
LPS
Morpho-elasticity of inflammatory fibrosis: the case of capsular contracture - Ben Amar, Martine and Wu, Min and Trejo, Miguel and Atlan, Michael
JOURNAL OF THE ROYAL SOCIETY INTERFACE 12 (2015) 
LPS


Abstract : Inflammatory fibrosis is a wound-healing reaction of the immune system in mammals against aggression. After a signalling cascade, fibroblasts and potentially myofibroblasts make a stiff collagenous tissue inside the body that modifies the original healthy tissue. We focus here on the implant-induced fibrosis that aims to encapsulate the implant with a typical fibrous tissue called the capsule. Focusing on breast capsules, we aim to understand the mechanical properties of these tissues, to test the validity of fibre models that have been established in other contexts such as arteries. For this purpose, we perform force-extension experiments and show that mechanical constitutive laws of these tissues are especially difficult to derive, because models are sensitive to fibre orientation and dispersion, independently of the variation between individuals. In addition, fibre breakdown, and possibly remodelling, occur during the extension experiments. However, the high stiffness of the capsular tissue, compared with the healthy tissue, added to the fact that an inflammatory process has no reason to cease, is at the origin of large compressive stresses in vivo, which explains the pain and unaesthetic deformity. We evaluate the stresses responsible for the pain and the buckling instability, which have no reason to stop if the inflammation persists.
The role of pressure in cancer growth - Taloni, Alessandro and Ben Amar, Martine and Zapperi, Stefano and La Porta, Caterina A. M.
EUROPEAN PHYSICAL JOURNAL PLUS 130 (2015) 
LPS


Abstract : The response to external mechanical forces is increasingly seen as a crucial aspect of cancer growth and a topic where the contribution of physics ideas and methods is important. Understanding if tumor progression towards increased malignancy reflects the geometry and mechanics of the microenvironment is an important issue still to be fully explored. In order to grow, tumors have to overcome the mechanical resistance posed by the tissues in which they originate, while cancer cells involved in metastasis are often subject to fluid pressure. Here we review the recent literature describing the role of solid and fluid pressure on tumor growth and progression. We discuss a variety of in vitro experiments as well as computational models used to interpret them. We conclude discussing future perspectives.