Zoologists succeed for the first time in transforming stem cells in freshwater polyps

Stem cells are versatile all-rounders. In the medical field, high hopes are resting on these miracle workers. However, we still understand very little about them.

Why adult stem cells sometimes begin to divide in an uncontrolled way is a mystery, as also is the fact that many stem cells lose this ability to divide under certain circumstances. Has man inherited these remarkable cells through an “invention” by his ancestors in the realm of the invertebrates? Zoologists at Kiel can now make the stem cells of a simple organism controllable.

An important breakthrough in stem cell research has been achieved at Kiel University: by microinjection into embryos of freshwater polyps, the scientists have been able for the first time to smuggle foreign genes into the stem cells of a simple biological organism. The fertilized egg cells that have been altered in this way produce offspring that all carry the foreign gene, which is then passed on from generation to generation.

The discovery is reported in the latest issue of the Proceedings of the American National Academy of Sciences. The zoologist Professor Thomas Bosch and his colleagues Jörg Wittlieb and Dr. Konstantin Khalturin of the Kiel University, together with Dr. Jan Lohmann of the Max Planck Institute for Developmental Biology in Tubingen, have thus opened up the possibility of exploiting completely new methods of analysis in research on simple organisms.

First of all, stem cells that are genetically labelled in this way, and which show green fluorescence (for example), make it possible to study in detail, in the completely transparent polyps, the ways in which the cells move about and become differentiated. The Kiel zoologists have already been able to show that these cells move actively into newly forming physical structures - such as the buds of the polyps - and thus enable them to form.

The stem cells altered in this way can also be used to “switch on” particular genes at a specific time and/or at a specific position in the body of the organism. If the genes that are thus activated are important, one can expect large effects on the organism. From such experiments one should be able to reach important conclusions about the functions of the genes concerned.

Furthermore, the altered stem cells of the polyp Hydra can now also serve as bioreactors, as they can produce animal or human protein molecules, such as antibacterial peptides, which can be used in research.

The research group of Thomas Bosch at the Zoological Institute of Kiel University has been studying stem cells in the freshwater polyp Hydra for many years. The scientists expect that their studies of the cells in this phylogenetically old and uniquely simple animal will give insights into the mechanisms that regulate the behaviour of stem cells, and have led to the development of complex cell systems in the course of evolution.

“This is a marvellous result, also for me personally”, explains Bosch, “because I began to work on this topic as long ago as 1985, as a young post-doc in the USA. This functionalisation of stem cells, with the ability to control them and use them as a research tool, will result in a great step forward. As Hydra possesses many of the genes that the human body also uses for development as well as pathogen defence, these new transgenic stem cells allow functional studies that cannot be carried out so easily in complex organisms and in humans. And last but not least, studies on the stem cells of lower life-forms do not present any ethical problems”.

Bosch is also involved in the two proposals of Kiel University for setting up of “centres of excellence”. One proposal, on the theme of “inflammation at interfaces”, is concerned with the defence mechanisms of the immune system, and the work reported here now makes it possible to study the evolutionary origin of genes involved in inflammation. In the proposed centre of excellence on “Future Ocean”, transgenic hydra will be used for functional studies of regulatory genes of marine organism. Both centre proposals have already passed through the first stage of approval by the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG). The full applications will go before the DFG in April 2006, and a decision is expected in October 2006.