Finally, cells from patient with laminopathies exhibit very abnormal nuclear deformation in microgrooves.
This opens to the possibility of using this system as a tool to detect pathological abnormalities in nuclear mechanics...

Surprisingly, the cytoskeleton is not mandatory for nuclear penetration inside grooves.
Cell-substrate adhesive forces are the main drivers of this process.

These nuclear deformations are dynamic: nuclei can in and out of the grooves cyclically.
Entry and exit from the grooves is associated with transient changes in perinuclear stiffness.

We observed significant 3D deformations of nuclei in microgrooves, from partial to full confinement inside a groove (caging), in various cell types.
The proportion of partial/full caging can be controled by the groove dimensions.

Oops wrong tag, out in @NatureComms of course!

And we think that this mechanism could be generalized in any borderless system where individual elements are externally oriented. To conclude, here is another example where biology successfully meets physics! A very fulfilling experience for me, thanks to all the people involved!

Then we teamed up with a physicist who built a model considering the monolayer as an active fluid. By adding in the model the constraint on cell orientation provided by the grooves, we were able to predict the emergence of the cell streams!

By studying further this phenomenon, we showed that the size of the streams can be specifically controlled by the groove depth, and that the presence of cell-cell junctions is necessary for the emergence of this pattern.

When recording the movement of monolayers of endothelial cells on the microgrooves, we were surprised to see the emergence of a very specific pattern of movement: corridors of cells moving alternatively from left-right or right-left that we called “antiparallel cell streams”.

To study this particular setting, we used microfabricated substrates composed of parallel arrays of micrometric grooves, which mimic the anisotropy often found in ECMs. Vascular endothelial cells cultured on these substrates align and elongate in the groove direction.

We know that confining cell assemblies on adhesive areas of different shapes creates very cool patterns of collective movement, but in vivo cells are often individually constrained and guided by physical topographical structures in their environment. So what happens in that case?