Speaker: Joachim P. Spatz
Department: Cellular Biophysics at Max Planck Institute for Medical Research, Biophysical Chemistry at University of Heidelberg
Subject: Mechanotransduction in Collective Cell Migration and its Synthetic Mimic
Location: TU Delft (BN)
Author: Antoine Rolland
The lecture was divided into two parts. The first part was about the dynamic movement of skin cells, which is influenced by different forces acting on them. The second part was about how this behavior could potentially be mimicked in synthetic cells.
In the first part, Joachim Spatz began by saying that group movement is a very interesting topic in biology. From birds flying together to cells moving in groups, it is very exciting to study the way they move. Joachim Spatz has been looking at the way skin cells move when there is no boundary on one side of the cells. This is comparable to the way skin cells move in the process of healing a wound. What is well known is that there are so-called leader cells that begin to move into the open space, and that a group of cells go and follow that leader cell. What was found out is that these leader cells are already determined before they go and lead the other cells. This was discovered by measuring the force that was on the cells. What was observed was that there were strong forces behind the leader cells, when that cell cannot be distinguished yet. What was also very interesting, was that a leader cell always ‘recruited’ nearly the same amount of cells. This can be explained in a mechanical way, because this is the amount of cells that a leader cell can reach with the force that it exerts. What I found the most interesting and surprising about this part is how mostly physical properties determine the way the cells move, rather than the biological properties of the cells. Joachim Spatz explained that there are sensors in the cells that can sense the force on them, and that in this way the leader cells can be determined. Moreover, the density had a big impact on the way the cells moved into the open space. The process went a lot faster when the density was lower. A higher density required to first eject some cells into the upper layer, before the process could start properly.
In the second part, Joachim Spatz explained how this movement of the cells could potentially be mimicked in synthetic cells. For this, a stable cell environment is needed. This can be achieved by creating nanodroplets with a polymer outside layer. To make an equivalent of the cell membrane, a lipid bilayer was added that bound to this polymer. It was proven that by adding components to this nanodroplet one after another, the result was better than when adding pre-assembled components. These nanodroplets also showed forms of adhesion, making it possible to apply and let them exert forces to potentially make the system from the first part in a synthetic manner. After the talk, we discussed some things with Joachim Spatz. What was interesting was the following question that arose: what exactly is life? To Joachim Spatz, for his cells to really become artificial life, they should be able to replicate, to move by their own and to create energy for themselves from the environment.
Leader cell with its follower cells
What really stood out to me from this talk is that physics and forces inside cells are way more important than I thought. Also, analyzing group movements of different kind of cells, could be very interesting for future research. Maybe we would discover that in group movement forces are often a very important factor. For me, this group movement is very interesting, and I wouldn’t mind learning more about this. Also, I think we are very close to creating synthetic life. Of course, ethical questions will rise if eventually real synthetic life could be created. I think this will be a big challenge for the future.