Embryonic stem cells (ES cells) are praised as "cells with great potential“ for the healing of various illnesses. Ethically, however, they are strongly controversial and opponents of stem cell research often doubt their therapeutic usefulness. Thomas Krähenbühl, ETH mechanical engineer with accent on biomedical engineering, has seen for himself how ES cell research has already led to first successes. In spring he wrote his diploma thesis in Boston, USA, in the lab of Robert Langer (1), which is embedded between Harvard University and the Massachusetts Institute of Technology (MIT). Krähenbühl's thesis should tie in with the recently achieved breakthrough of his coach, Shulamit Levenberg: the formation of a three-dimensional nervous tissue from human embryonic stem cells.

Hope for paraplegia sufferers?

The objective of Krähenbühl's work was to develop a higher organised, three-dimensional nervous network from human embryonic stem cells. This neuronal cell network, developed outside of the human body could help, for example, to heal paraplegia. Until now, ES cells have usually been cultivated in flat dishes and incited to form specific cell types. The structure of this three-dimensional neuronal network corresponds better with the natural development of the organ, however. "The nearer the developed tissue comes to mimicking naturally formed tissue, the quicker it can integrate itself into the patient's own injured spinal cord after engraftment," says Krähenbühl. This method has already been successfully tested on animals, but Krähenbühl says, "In no way will we be able to carry out such transplants in humans in the next few years. 15 or 20 years are more likely. In the meantime, we need to focus on fundamental research."

Krähenbühl took up this challenge in Boston. Based on recent findings, the hypothesis was advanced that the synthetic carriers which are metabolisable in the human body can physically support stem cells in developing stable, three-dimensional tissue. He also identified nerve growth factors to direct the differentiation of ES cells into neurons. Adding the chemical factor "NT-3“ turned out to be "a great idea" in the process. The success of the study was that, after just 14 days in the incubator, human embryonic stem cells, nerve growth factors and the metabolisable synthetic carrier grew into stable nervous tissue.

Stem cell research in the States

Asked about the ethical aspects of handling human embryonic stem cells in research, Krähenbühl explains that in a course, which MIT organises for all those who want to work with ES cells, he received intensive preparation for his work. "With a historical overview, stretching back to Nazi Germany, we were reminded of the circumstances and consequences surrounding experiments on human beings. One has to be fully aware at all times that one is working with human cells." It therefore went without saying that these cells be handled with the greatest circumspection and respect. The experiments were minutely planned to avoid wasting of cells. Asked about how he personally had experienced the work, Krähenbühl says that he never had the feeling that he was "fiddling around" with a human being. It was much more important to him, he says, to find and maintain a balance between respect for the embryonic stem cell and the lives of patients waiting for cures.

Thomas Krähenbühl had decided to do ES cell research in the USA. Such research is allowed there if it is financed by private funding, and restricted if subsidised by the state (cf. box).

Gained first experience of working on human embryonic stem cells in the USA: ETH graduate student Thomas Krähenbühl. large

Professor Ralph Müller from the Institute for Biomedical Engineering of ETH and the University of Zurich (2) put him in touch with contacts and oversaw his plans. The aim of such exchanges is to enable motivated students to get to know the new technologies involved in order to help them better understand and assess the advantages, but also the disadvantages, of such controversially discussed studies.

Stem cell research in Switzerland

On the 28th November 2004, Switzerland's electorate will decide the future of stem cell research at the ballot box. The proposed Stem Cell Research Law provides a legal framework for the use of human ES cells (3). Thomas Krähenbühl sees this law as the right step and an important one. "If it is passed researchers in Switzerland will have a clear ethical and scientific framework. The bill affords the embryo appropriate protection and dignity. Surplus embryos resulting from artificial fertilisation procedures would have to die according to today's valid laws. Why shouldn't embryonic stem cells be used, with the consent of the parents, to develop possibilities of treatment to help people who are waiting for cures?“ Asked whether cloning would not be the logical consequence of successful stem cell research, Krähenbühl answers, somewhat noncommitally, "At the moment I can't see the necessity of allowing therapeutic cloning.“ The Stem Cell Research Law mainly aimed at controlling research on human embryonic stem cells within a clear scientific and ethical framework . The result of this vote was also important for the attractiveness of Switzerland as a location of research.

Still, independently of the results of Sunday's ballot, Thomas Krähenbühl will probably return to the States for his next steps in research.