Séminaire PMMH - Lorraine Montel (UPMC)

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11 décembre 2020 11:00 » 12:00 — Salle réunion PMMH 1

Emulsion droplets as a model biomimetic system

Emulsion droplets recapitulate the deformability and surface fluidity of biological objects, in a simpler and tunable fashion. Thus, they can be used as a model biomimetic system to study cell-cell interactions. During this talk, I will demonstrate this use in two different systems : the study of phagocytosis, and the study of the role adhesion plays in tissues.

During phagocytosis, immune cells identify, internalize and digest foreign objects or dying cells, a process essential for immunity, but also for the homeostasis of tissues. Phagocytic cells are able to internalize objects bigger than themselves, yet, how the size of their target impacts their ability to phagocyte remains a controversial question. Using polydisperse emulsions and a new automated analysis method, we could show that the phagocytes do not select the size of their targets. Instead, they are limited in the total surface they can engulf, and can thus internalize less of the bigger objets. Moreover, this surface limitation is common to diverse types of cells, of ligands and of objects across all ranges of sizes.

During morphogenesis, cell differenciate and reorganize acquire their shape and function. In addition to biological cues, the mechanical properties of cells and their interactions are essential to this process. Yet, in biological systems, it is challenging to isolate the role of one parameter. Adhesive emulsion droplets can also be used as a model system to question the role of adhesion in tissue mechanics, without the interference of biochemical signalling, feedback loops and active processes. We sheared an adhesive emulsion in a microfluidic constriction, and observed with confocal microscopy how adhesion impacted the shape of droplets and their rearrangements. In dynamics, we found that T1 rearrangement events occur more slowly and at much higher deformation in the presence of adhesion. At a global scale, the topology of rearrangements is not impacted, however, the adhesion creates a global polarization of the deformation in the direction of the flow.

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