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Human Fertilisation and Embryology Bill [HL]

The noble and learned Lord, Lord Mackay, raises an important issue with his amendment. I draw the attention of the Committee to one aspect of this in the research area. True stem cells, at best, are totipotent; that is, they can develop into any one of numerous cell types—in the case of the human body, it is about 220 different cell types. There are various degrees of potency. Some stem cells are pluripotent, which means that they can develop into many tissues, but not all. Some stem cells—mostly, it seems, from adult sources—have even more limited potential and can grow only into certain tissue types. There are many ways of assessing a stem cell’s potency for further development. One can look at the genes which the cells produce and get some idea of how they are likely to progress if allowed to differentiate into different tissues. One can look at the tissues which are produced in vitro in the laboratory, to see whether one is developing nerve cells, muscle cells, heart cells and so on. However, one of the best tests—it is almost the prime test, and the one that has been most used in the literature and the most valuable—is to mix stem cells with an animal embryo, usually that of a mouse, to see what happens to the human cells during that animal’s development, which is then sacrificed either before gestation has finished or shortly afterwards. The classic experiments have allowed it to be established that good stem cells, which one really might want to use, can be incorporated in a wide range of tissues—liver, spleen, kidney, brain, heart and so on. This is without doubt an extremely valuable test. The question is whether it would continue to be a viable possibility for experimenters in this country who look at stem cells in the future. It would seem to me very important that it does; there will be no question of producing a hybrid, which would in any case be monstrous or threatening. This apportionment and prediction of how tissues develop have been vital in the past and a key point in many of the papers published on stem cells.