22 September 2009

Cell communication modelled

Animals and plants need to know what is happening throughout their organism. For that an organised communication system is needed, so that the body or the plant knows what is happening all the way out in the individual cells. Cells can communicate with each other with the help of signalling molecules, but how do they do it? Researchers at the Niels Bohr Institute have now worked out a theoretical dynamic model for how this done. The results are published in the scientific journal, Physical Review Letters.

By now it is well known how the genes within the cells are regulated and a number of genetic cycles have been mapped including how characteristics are switched on and off and how the feedback reactions function. The two most well-known examples are the network, which reacts to infection and the system that ensures that sick cells commit ’suicide’ and are removed from the body.

But all of the decisions that are made within the cells can be completely dependent upon neighbouring cells and the surrounding environment.

Spatial cell communication

Cells from fatty tissue

Cells from fatty tissue which are tightly packed.
The red lines diagram shows which cells are
communicating with each other. Typically a cell
has the strongest communication with its
neighbouring cells. These interactions can arrange
‘lattice’ and the communication often happens
through wave propagation.

”That is why we wanted to study cell communication and make a theoretical model, that clearly took the spatial position of different cells into consideration”, explains Mogens Høgh Jensen, professor with the research group Biocomplexity at the Niels Bohr Institute at the University of Copenhagen.

The starting point was two completely different cell environments – where the cells lie tightly packed next to each other so the cell membranes touch each other directly, and a fluid, where the cells float scattered around. The research is a collaboration between microbiologists, who perform the biological experiments with the cells and physicists, who calculate the mathematical models for the cell communication.

When looking at the tightly packed cells, the microbiologists’ research shows that channels are actually formed in the cell membranes, so that the one cell can send direct messages via signalling molecules to the other cell. But does the message spread evenly from neighbouring cells to neighbouring cells or is there a pattern of distribution? The biophysicists set out to determine this.

Well ordered network

The biophysicists Mogens Høgh Jensen, Sandeep Krishna and Simone Pigolotti constructed a mathematical model for, how the signalling molecules spread and how the cells react to it. Their model shows that a very well ordered network pattern forms for how the signalling molecules move in a tightly packed cell culture.

”It is always such that the cells ’talk’ with their nearest neighbour and it starts with the signalling molecules spreading outward. After that a pattern arises with a very well ordered structure which spreads in waves. The waves do not only travel forward, but also back to the original cells”, explains Mogens Høgh Jensen. In some special cases there could also arise a chaotic, almost panic like distribution.

The model calculations for environments with dispersed cells show that here the cells send signalling molecules out into the environment where they move around until they reach a cell, which the signalling molecule then enters, after which the cell sends the message further out in the surrounding environment. Here the communication goes much slower than in the tightly packed cell cultures.

A great deal is known about cell communication in biology, says Mogens Høgh Jensen and explains that the new biophysics models are a start in the systemisation of the communication system of cells. This knowledge can be used for medical research.

Physical Review Letters >>