181st iCeMS Seminar: Prof Françoise Brochard-Wyart and Dr Grégory Beaune
Prof Françoise Brochard-Wyart
Soft Matter models of tissue "wetting of living drops":
Spreading and motility of cellular aggregates
In the eld of "Active Matter," active processes in both living and non-living matter
create a novel class of nonequilibrium materials composed of many interacting units
that individually consume energy and collectively generate motion or mechanical
stresses. Active systems span an enormous range of length scales, from the
cytoskeleton of individual living cells, to animal groups such as bird ocks, and insect
swarms. By analyzing the tissue mechanical properties of multicellular aggregates using
a new pipette aspiration technique, we characterized the biomechanics of these
aggregates, which exhibit a mechanosensitive viscoelastic response of the acto-myosin
cortex. We then studied the spreading of aggregates on rigid and soft substrates, and
found that the dynamics of spreading results from a balance between active cellular
driving forces and permeation of cells to enter into the lm. Finally we found that the
motility of aggregates on soft substrates leads to symmetry breakdown and a global
motion of the aggregate. We describe the ow eld and the force eld responsible of
the motion. We will also show strong similarities between aggregates of ants and cells!
Dr Grégory Beaune
Characterization of phosphorylcholine-modifi ed
chitosan fi lms that promote the formation of cell
aggregates and spreading of cell aggregates
Cellular aggregates are important for tissue engineering and pharmacological studies.
For in-vivo implantations studies, it is preferable to assemble spheroids directly on the
biomaterials to be implanted. I will describe the elaboration and characterization of
chitosan-phosphorylcholine (CH-PC) lms able to support the formation of cell
aggregates. Then, I will focus on cellular aggregates used as model system of tumors.
When deposited onto bronectin-coated glass or polyacrylamide gels, they adhere and
spread by protruding a cellular monolayer that expands around the living droplet. The
dynamics of spreading results from a balance between the pulling forces exerted by the
highly motile cells at the periphery of the lm, and friction forces associated with two
types of cellular ows: i) permeation, corresponding to the entry of the cells from the
aggregates into the lm, and ii) slippage as the lm expands. We characterize these
ows by using uorescent tracking of individual cells and particle imaging velocimetry
of cell populations. Also we study the spreading in function of the substrate rigidity. Our
results demonstrate that the mechanical properties of the environment in uence the
balance of forces that modulate collective cell migration.
| Lecturer |
Prof Françoise Brochard-Wyart Institut Curie-PCC Curie-UMR 168 Université Pierre et Marie Curie, Paris France Dr Grégory Beaune International Center for Materials Nanoarchitectonics (MANA) National Institute for Materials Science |
|---|---|
| Date / Time | November 25, 2014 / 10:00-12:00 |
| Venue | 2nd floor Seminar Room (#A207), iCeMS Main Building, Kyoto University
Directions |
| Flyer |  PDF (180KB) |
| Host | Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University |
| Registration | Not required. |
| Contact | iCeMS Chen Group | chen-g@icems.kyoto-u.ac.jp |