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14 Septembre 2017 Annie VIALLAT

« Two stories of microflows and active biological matter. When red blood cells pass a physical test in the spleen and the physics of the mucociliary escalator »

Annie VIALLAT du Centre Interdisciplinaire de Nanoscience Marseille

Jeudi 14 Septembre 2017 de 11h à 12h « Salle des conférences » RDC bâtiment NANOBIO DCM 570 rue de la Chimie (en face du bâtiment E) badge pour entrer

The two most frequent red blood cells (RBC) diseases, the sickle cell disease (SCD) and the hereditary spherocytosis (HS), are characterized by an increase of the cell rigidity. This leads to circulatory problems in thin capillaries and the inter-endothelial splenic slits. The latter have sub-micron dimensions and play the role of RBC filter ; less deformable cells are trapped at the slits entrance and are further eliminated by white blood cells. The mechanical parameters of RBCs that control their behavior in micro-flow are yet not understood. We developed a microfluidic device of PDMS containing slits with physiological dimensions. We reveal novel modes of deformations of healthy and diseased RBCs squeezing through splenic-like slits under physiological interstitial pressures. At the slit exit, the cytoskeleton of HS RBCs seemed to be detached from the lipid membrane whereas RBCs from healthy donors (H) and from patients with SCD exhibited peculiar tips at their front. These tips disappeared much slower in patients’ cells, allowing estimating a threefold increase in RBC cytoplasmic viscosity in SCD.

Mucus is propelled along bronchial airways by the continuous coordinated beating of microscopic cilia located on ciliated epithelial cells. We find that ciliary activity self-organizes to generate local flow patterns at the epithelium surface. We relate mucus transport to hydrodynamic interactions and cilia beats and reveal active mechano-transductional effects.

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