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Mesure des déplacements cellulaires dans les tissus non transparents : une application de la diffusion dynamique de la lumière

Abstract : As a tumor grows, it exerts a mechanical pressure on its surrounding tissue and is compressed back as a reaction. Recent experiments on an in vitro tumor model, called spheroid, have shown that this pressure is crucial for the fate of the cancerous tissue. In particular, the pressure slows down its growth, but makes it more invasive. To further understand the latter effect, we decided to study the migration of cells inside spheroids under pressure. However, imaging the inside of a spheroid is technically challenging as usual microscopy methods do not work on thick tissues (> 100 μm). Standard imaging methods are limited in terms of depth penetration because of light scattering. For this reason, we decided to take advantage of this scattered light with a method called Dynamic Light Scattering (DLS). We developed its application to cell migration in order to measure the distribution of cells displacements over time. The measurement is label-free and works with spheroids as thick as 400 μm in diameter. By this means, we revealed a radial organization inside the spheroid in terms of mobility, with fast cells at the surface and slower cells in the core. We also showed that applying a pressure onto spheroids decreases the average cell speed by a factor up to two for pressure greater than 15 kPa. Another team reported an increase in the speed of cells located at the surface of a compressed spheroid, which implies that the radial organization is also true for the impact of pressure. We demonstrated that this sensitivity to an external pressure is a 3D emergent property, in which the extracellular matrix plays an essential role. Finally, we explored the potential of our technique by addressing another question: how do apoptotic cells signals affect the migration of macrophages? We found that early apoptotic cells increase the speed of macrophages whereas late apoptotic cells decrease it. In both cases, the persistence length of the motion is the same.
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Submitted on : Friday, February 22, 2019 - 6:25:06 PM
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  • HAL Id : tel-02046692, version 1




Benjamin Brunel. Mesure des déplacements cellulaires dans les tissus non transparents : une application de la diffusion dynamique de la lumière. Biophysique []. Université Grenoble Alpes, 2018. Français. ⟨NNT : 2018GREAY047⟩. ⟨tel-02046692⟩



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