Tadpole Soon To Help In The Fight Against Cancer And Lymphedema

Lymph: a very important colorless fluid

Fluid and proteinsleak out of the blood vessels during blood circulation in the body. Anetwork of lymphatic vessels catches this extravasated colorless fluid,lymph, and transports it back to the blood vessel network. Thelymphatic vessel network is of major importance. It is essential forregulating fluid in the body and for the support of the immune systemthat protects us from pathogenic organisms. Faults in the making orfunctioning of this network cause many disorders, such as inflammatoryand infectious diseases and lymphedema (a swelling caused by waterretention). On the other hand, a well-functioning lymphatic vesselnetwork can simplify the spread of cancer cells. A thoroughunderstanding of this network is thus essential for seeking a solutionfor these diseases.

The search for a suitable model system

As far back as in1627 Gasparo Asellius discovered the lymphatic vessels as 'milkyveins'. Yet the lymphatic network has not been studied much until nowand is therefore as good as unknown, quite amazing seeing itsimportance for our health. One of the reasons for this lack of study isthe fact that there was not a good model system until now. Lymphaticvessels can be studied in mice but this takes time and is extremelycomplex. Moreover, a study of mice only enables the examination of geneper gene, which complicates revealing the combined action betweenvarious genetic factors. For efficient research smaller model organismsare used, such as the zebrafish, which is popular in the study of theblood vessel system. But the zebrafish also offers little comfort, asit does not have any lymphatic vessels.

In the early 20th century studies suggested that tadpoles dohave lymphatic vessels. This urged Peter Carmeliet and his researchgroup to examine whether tadpoles can form a suitable model system forthe study of the lymphatic vessel network. Tadpoles can easily begenetically modified, which is why they are an ideal model system inwhich it is relatively easy to identify genes that are important in thedevelopment of complex biological structures like lymphatic vessels.

Unraveling the lymphatic vessel system through tadpoles

Withtheir research, the research group op Peter Carmeliet indicated thattadpoles are extremely suitable for the study of lymphatic vessels. Todo this they used Prox1, a protein that is essential for the formationof lymphatic vessels. With the help of coloration techniques theyvisualized the areas in tadpoles where Prox1 is made: the lymphaticvessels. With the same coloration techniques the researchers indicatedthat the development of lymphatic vessels in tadpoles is comparable tomice and humans. A second part of their research was altering tadpolesin such a way that they make much less Prox1 than normal tadpoles. Thisresulted in a badly developed lymphatic vessel system, because of whichthe tadpoles showed signs of lymphedema. It did not have any effect onthe blood vessel system.

With these results the VIB researchers are the first to provethat tadpoles are perfect model organisms for the study of lymphaticvessels. In the future tadpoles can be used to identify genes that areimportant for the development of this complex network. This paves theway for the search for solutions for illnesses caused by faults in thelymphatic vessel network.