The scientists claim to have identified a completely new mechanism for how communication can be regulated between cells. This clears the way for the creation of new drugs that can regulate the new generation of blood vessels. Such drugs could improve the treatment of specific eye diseases also.
The team from Uppsala University, studied blood vessels grown from embryonic stem cells from mice.
By genetic modification of the stem cells, the scientists demonstrated that production of the sugar molecule heparan sulfate is essential for the formation of blood vessels.
"We made use of stem cells with two types of genetic modifications. In the first we removed the gene that produces the enzyme needed for sugar chains to bind various growth factors," said Lars Jakobsson, one of the researchers of the study.
"In the other we removed the gene that produces the receptor for the growth factor VEGF (vascular endothelial growth factor)," he added.
Blood vessels are made up of tubes consisting of endothelial cells, support cells, and membranes in various layers. The inside of the vessel is covered with endothelial cells.
To carry out this assignment and to form new blood vessels, it is necessary to have close contact and communication between the various cells and membranes of the blood vessels.
The first modification resulted in cells with defective heparan sulfate and the other in the cells' not being able to form the receptor for VEGF. Neither of these two types of stem cells was able to generate blood vessels on their own.
The researchers think that the new stem cell model makes it possible to create cultures in which heparan sulfate is produced solely by support cells and not by endothelial cells.
It has previously been known that heparan sulfate binds various growth factors, including VEGF, and 'introduces' these factors to the receptors on the surface of the cell.
The Uppsala researchers are now demonstrating that VEGF that is introduced by heparan sulfate to support cells (as opposed to the heparan sulfate found on endothelial cells) provides a much stronger and longer-lasting effect on the activation of endothelial cells.
The conclusion is that both the amount and the position of the heparan sulfate play a decisive role in the formation of new blood vessels.
"To further study the role of heparan sulfate in cells, we developed a model in which we let the different stem cell modifications grow together. It turned out that under these conditions the cells were able to generate lots of blood vessels," added Jacoksson.
"This is highly surprising, and exciting. It provides us with new information about how various cells can communicate and support each other in forming various organs in the body."
The study is being published on May 9 in the prominent journal >Developmental Cell.