News Details

Blood Vessel Network Formation Observed Live for the First Time

Prof. Markus Affolter’s research group at the Biozentrum, University of Basel, has been successful in documenting the formation of blood vessel networks live in a living organism, the zebrafish, for the first time. The scientists have been able to establish two mechanisms by which blood vessels build networks. The findings are being published in the journal Current Biology.

Until recently, it was not possible to investigate the formation of blood vessel networks at the cellular level in living organisms since no suitable method for live imaging was available. Markus Affolter’s research group at the Biozentrum of the University of Basel has now succeeded in observing this process in a living organism, through the introduction of a fluorescent protein that is involved in the building of blood vessels. The scientists took advantage of the special feature of the zebrafish, which is almost transparent, making it possible to observe blood vessels network formation inside the living animal. Important in this process is the behavior of the leading cells of growing vessels, the so-called tip cells. It is at this point, via the connection of two tip cells, that two blood vessels join and thus build a network.

Blood vessel formation through blood pressure or reshaping

Through their observations, the researchers were able to establish that the formation of blood vessels is based on different underlying processes. On the one hand, a vessel already perfused with blood can extend the lumen further due to the blood pressure causing tip cells to widen and become indented until they reach the tip cell of the neighboring blood vessel and connect with it. On the other hand, a different  process can be observed in blood vessels that are not perfused yet  and is therefore not caused by blood pressure. In this case, the tip cells of two vessels in close proximity meet and build a hollow at the point of contact.. The two tip cells of the blood vessels then change shape and rearrange thereby enabling the vessel lumens to finally merge to one.

Selectively stopping blood vessel growth in cancer 

For Markus Affolter’s team, the most important question for future studies is how tip cells from two blood vessels recognize their growth destination and eventually connect to each other and which genes drive these processes. A deeper understanding of the cellular steps in blood vessel formation could help to identify new approaches for targeted blood vessel formation bringing improved blood circulation to specific parts of the body or, alternatively, to suppress blood flow. It is conceivable that such a selective intervention could, for example, impede blood vessel development in growing tumors, and thereby improve the treatment of diseases such as cancer.

Original article:

Lukas Herwig, Yannick Blum, Alice Krudewig, Elin Ellertsdottir, Anna Lenard, Heinz-Georg Belting and Markus Affolter (2011): Distinct cellular mechanisms of blood vessel fusion in the zebrafish embryo. Current Biology, Published online 10 November 2011.
http://www.cell.com/current-biology/abstract/S0960-9822%2811%2901140-7

Contact: Communications, Heike Sacher