The facility is led by EVGN member Marina Mione, IFOM scientist and leader of the Zebrafish group. Developed after an IFOM proposal to the consortium, the technological platform will provide EVGN members with the possibility to test and validate in this unique in vivo system data previously obtained in vitro. Funding comes from EVGN and it covers an initial period of 2 years (with 60.000€/yr). At present, there are 5 ongoing collaborative projects involving EVGN partner laboratories from Italy, Germany, Finland, U.K. and France, whose completion is expected in one or two years.
Zebrafish (Danio rerio) is an ideal low-cost powerful model widely used for screening the angiogenic and cardiovascular regenerative properties of novel genes, for the validation of new drugs and drug targets and for the investigation of other human diseases (neurodegenerative diseases, osteoarthritis etc.). This is not surprising, as this model organism is endowed with an immune system, and fully functional nervous and cardiovascular systems. Besides, many human genes have an equivalent in Zebrafish and a number of biochemical pathways are similar between fish and men, albeit the two species are distant.
Easy to grow, the individuals become sexually mature at three months and the females lay up to 300 eggs per mating. The most interesting feature, however, is represented by the eggs themselves, which are transparent and allow the direct observation of inner events. “For this reason – points out IFOM scientist Marina Mione - this system is particularly suitable to observe any experimental modification, especially those that involve the early steps of the vascular system’s development”.
Angiogenesis, the blood vessels growth that occurs during embryogenesis or after myocardial infarction and stroke, is a complex event. During its physiological course it is precisely modulated at the genetic level. However, there are times where it would be desirable to modulate this process at will: boosting it after an ischemic event that leaves tissues without oxygen, or dimming it in tumours that sprout their own vessels to nourish themselves. In both cases, Zebrafish proves to be the ideal model system for hypothesis testing and validation.
“The rapid life cycle of Zebrafish together with eggs’ transparency – confirms Marina Mione – are two of the most interesting features of this organism. They allow real time screening of any introduced modification and are especially useful when it comes to the analysis of the vascular development. Blood vessels growth starts early but Zebrafish needs functional vessels only after several days, since the embryo is vital even in the absence of a fully formed vascular system. This is a clear advantage over other experimental systems. We can monitor what happens whether blood vessels are defective, follow their anomalous growth and correlate any visible alteration to the mutation we introduced.”
Investigations carried out in Mione’s laboratory include the generation of transgenic Zebrafish to observe directly cell behaviour during vasculogenesis (de novo vessel formation) and angiogenesis (vessel sprouting), the suppression of a gene of interest (technically called knock-down) as well as the rescue of an original character. “Loss- and gain-of-function experiments are part of so-called reverse genetics”, says Mione. “They are easy to perform in Zebrafish and very informative, since they provide critical information for the study of candidate genes”. In gain-of-function experiments scientists ask what would happen if a specific gene is activated in the embryo where it is not normally active, whereas in loss-of-function experiments, they ask what happens when a particular function is removed from the embryo altogether.
The experiment design starts in one EVGN institution where initial data are gathered from in vitro systems; then Mione and colleagues carry out in vivo assays to confirm the hypotheses. Hence the collaborative effort between the partners helps to provide complete answers to asked questions. Among the projects that Mione is following, there is a study carried out in collaboration with the EVGN laboratory directed by Seppo Ylä-Herttuala, at the Department of Biotechnology and Molecular Medicine, A.I.Virtanen Institute, University of Kuopio, Finland. "We are studying vasculogenesis – says Kati Pulkkinen, who works in Seppo Ylä-Herttuala's laboratory in Kuopio – using a technique called knockdown morpholinos, to inactivate genes in a selective way. Our experiments are at an early stage. But results are coming, and we are in the middle of confirming them.
“Another important part of our research – says Mione – is the definition of the molecular mechanisms that govern angiogenesis during tumour growth, as well as the selection of antiangiogenic drugs”. To this purpose, fluorescence vascularization tests in Zebrafish are extremely useful because they allow to unveil the involvement of some genes in the angiogenesis of tumours, and to screen drugs potentially able to stop the process.
Angiogenesis, drug screening and drug targeting are some of the most important issues EVGN scientists are focussing on. This is why the newly established Zebrafish platform has been welcomed with much enthusiasm, as it is expected to give meaningful contribution to the understanding of the process and to suggest new strategies to modulate it at clinical level.
“Recent studies – observes Alain Tedgui, EVGN Scientific Coordinator from INSERM U689 in Paris - indicate that using Zebrafish we can investigate not only the molecular mechanisms of development, but also the cellular and molecular physiology and pathology in the adult. In the context of EVGN, cardiovascular pharmacology and angiogenesis are certainly the two areas in which we can expect fruitful findings. A potential limitation of this model system is that, so far, there is no report that atherosclerosis develops in Zebrafish vessels. However, it may be just a question of time to be able to do so!”
The European Vascular Genomics Network (EVGN) is a network of excellence funded by the European Commission under the 6th Framework Programme "Life Science, genomics and biotechnology for Health", aiming at integrating and strengthening the European research area in the field of Cardiovascular Diseases (Contract Number: LSHM-CT-2003-503254). Additional information on the EVGN is available at http://www.evgn.org/
Francesca Noceti | alfa
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