Cartilage tissue provides compressive resistance in diarthrodial joints, and has been shown to be regulated by mechanical signals, in particular with regard to production of extracellular matrix proteins. However, less is understood about how chondrocytes in regions not solely purposed to provide compressive resistance may also be affected by mechanical forces. The growth plate is a small layer of cartilage that functions to facilitate longitudinal growth of the long bones from in utero through post-adolescent development. The growth plate maintains distinct regions of chondrocytes at carefully regulated stages of endochondral ossification that are in part characterized by their morphology and differential responsiveness to vitamin D metabolites. Understanding if mechanical cues could be harnessed to accelerate or delay the process of endochondral ossification might be beneficial for optimizing tissue engineering of cartilage or osteochondral interfaces. This study focused on three aims to provide a basis for future work in this area: 1) Develop a cell line culture model useful for studying growth plate chondrocytes, 2) Determine the response of primary growth plate chondrocytes and the cell line model to fluid shear stress, and 3) determine if expression of integrin beta 1 is important for the observed responses to shear stress. The findings of this study suggest that inorganic phosphate can promote differentiation in coordination with the 24,25(OH)2D3 metabolite of vitamin D, and that fluid shear stress generally inhibits differentiation and proliferation of growth plate chondrocytes in part through an integrin beta 1 mediated pathway.

Par rapport à un fluide Newtonien, les suspensions denses de particules présentent des propriétés rhéologiques différentes. Des comportements rhéofluidifiants ou rhéoépaississants liés à des phénomènes de migration de particules peuvent apparaitre. Pour des suspensions, le taux de cisaillement, la concentration et la taille des particules ont une grande influence sur ce comportement rhéologique (Denn et Morris 2014). Pour observer l'influence de ces facteurs, l'un des meilleurs moyens est de disposer d’un système simple dans lequel tous les facteurs mentionnés ci-dessus sont bien contrôlés. Ceci peut être réalisé par le développement d'une plate-forme expérimentale, sur laquelle les comportements d'écoulement de suspension (profil de vitesse et concentration locale de particules) à des vitesses de cisaillement et des concentrations de particules bien contrôlées peuvent être étudiés. Dans l'étude actuelle, 4 tâches ont été réalisées :1) Le développement d'une nouvelle formulation pour la préparation d’une suspension adaptée en indice de réfraction et en densité basée sur des particules de PMMA. 2) Le développement d'un dispositif expérimental consacré à l'étude des flux de suspension dense sous une large gamme de taux de cisaillement constant. 3) La caractérisation des profils de vitesse des flux de suspension dense sous un dispositif cône-plan utilisant des techniques de micro-PIV. 4) Une mesure préliminaire de la concentration locale de particules de la suspension sous écoulement cône-plan en utilisant des méthodes de traitement d'image. / Compared to general Newtonian fluids, highly concentrated mixtures of particles and fluid, so called dense suspensions, have different rheological properties and fluid dynamic behaviors. Such as, shear-thinning or shear-thickening effect, and apparent slip and particle migration behaviors under certain shear flow conditions. These properties are related to the application of suspension flow in real systems, for example, the blood.For suspensions, shear rate, particle concentration and particle size have a big influence of on their rheological behaviors (Denn and Morris 2014). To observe the influence of these factors, one of the best ways is to start the research from a simple case in which all the above mentioned factors are well controlled. This can be realized by developing such an experimental platform, on which the suspension flow behaviors (velocity profile and local particle concentration) at different shear rates and particle concentrations can be investigated.In the current study, 4 tasks were achieved:1) The development of a new recipe for the preparation of density and refractive index matched suspension with PMMA particles. 2) The development of an experimental set-up devoted to the investigation of dense suspension flow under a large range of constant shear rate. 3) The characterization of the velocity profiles of dense suspension flows under a cone-plate device by using micro-PIV techniques.4) A preliminary measurement of the local particle concentration of the suspension flow by using image processing techniques.