The blood vessel research conducted by Professor Markus Affolter and his team at the Biozentrum of the University of Basel could prove indispensable in the development of new cancer treatments by REBECCA PARSONS (Jun. '10)
Professor Markus Affolter is in charge of a zebra fish embryo study researching angiogenesis, which means the recruitment of new blood vessels as a normal process in growth and development, but also as an essential component of tumours’ metastatic pathway. The main implication is that these vessels provide the main route by which tumour cells exit the main tumour site and enter the bloodstream. A highly vascularized tumour has indeed a higher chance to metastasize. Zebra fish looks like one of the most promising animal systems in the study of angiogenesis just now. The formation of intersegmental blood vessels (ISVs) in the zebra fish embryo serves as a paradigm to study angiogenesis in vivo. To investigate the cellular architecture and the development of ISVs in detail, Professor Affolter’s team have analysed the arrangement of endothelial cell junctions and have performed single cell live imaging.
Which are the advantages of using Zebra fish for analysing the development of embryos and organs at a cellular level?
It is easy to breed, develops from egg to larvae within 3 days and river crabs suffice for its nutritional needs. This makes it particularly useful for research purposes. Yet the most important reason for choosing the zebra fish is the fact that the fish develops outside of the mother's body and remains transparent throughout its embyonic development. This has enabled our team to observe the entire process of organ development within the embryo. What we are really interested in is how the blood vessels grow. The embryos remain transparent and we are able to collect hundreds of embryos each day. This makes it a perfect specimen for the study of blood vessel development.
How is it possible to study the blood vessel development in a Zebra fish?
Under ideal conditions a female zebra fish lays between 50 and 100 eggs at a time. The eggs then sink to the bottom of the breeding tank, where they are fertilised by the male fish. The fish eggs, which are a mere 0.5mm in size, are injected with a special flourescent DNA. This allows the process of blood vessel development to be studied in the embryo at a later stage. For best results, the egg should be in the single-cell or four-cell stage of growth. The needle penetrates the shell of the egg, also known as chorion, and enters the cell. The DNA solution is dyed a reddish colour in order to be able to judge whether enough liquid has entered into the cell. The DNA then enters into the nuclei of the cells, including the nuclei of blood vessel cells. In these cells a fluorescent protein is formed that illuminates under UV light. In this way, the blood vessel cells are made visible throughout embryonic development. Successful impregnation with the special DNA means that within a few hours the embryos can be studied and filmed with the help of a special microscope.
What have you discovered about the functioning of cell development through Zebrafish research?
We have developed a revolutionary recording method has enabled us to be the first to capture the process of how a cluster of cells becomes an organ. In order to be able to film the organisms, the fish embryos are mildly sedated with a special solution. Under the confocal microscope the embryos are then illuminated by means of a laser, which makes the fluorescent protein in the blood vessels light up. Recordings of up to 30 frames per second make the behaviour of each individually marked cell visible. Blood circulation development occurs in the early stages of embryonic development, because without blood circulation no other development would be possible. What we are able to do here is a scientific revolution! In this way, any person is able to understand this process.
What we have since discovered is that each cell does not operate on its own. Instead, they behave collectively and in accordance with the other's respective functions. When a cell divides, it still needs to remain within its lattice. Previous models for understanding this development have been proven false. The formation of tubes is different from what we had imagined in the past. Among many other things, this has important consequences for cancer research.
How can this type of research help finding new solutions for cancer treatments?
Despite no visual similarity, the genes and genetic functioning of the zebra fish are surprisingly similar to that of humans. This makes them invaluable for research into genetic functioning. What we are able to observe in zebra fish embryos, will function in a similar manner in humans. This means that any breakthrough in zebra fish research is a breakthrough in understanding human genetic functioning and development. Blood vessels form the channels of nourishment for any cell in the body – including cancerous cells. Blood vessel research is vital in cancer treatments. If we are able to ascertain exactly which substances are vital for the development of blood vessels, then we would be able to prevent blood vessels from growing and supplying the tumor with nutrients. The aim of many treatments is to prevent the cancer from accessing blood vessels. This then inhibits the growth of the cancer due to a lack of oxygen. New treatments for cancer are thus possible through this type of research.
(24 June 2010)
Rebecca Parsons