February 3, 2009

experts comment on research into hybrid embryos, as published in the journal Cloning and Stem Cells

The paper claimed to call into question the effectiveness of human-animal hybrid embryos as an avenue of research, and suggested that it could be more difficult than previously thought, or even impossible, to derive significant quantities of embroynic stem cells that would be viable for research and treatments.

Prof Chris Mason, Professor of Regenerative Medicine, University College London, said:

“Until this particular experiment is repeated by an independent laboratory, the jury must remain out. Science can never rely upon the results of single experiment regardless of the world class status of the researchers involved.”

Prof Colin Blakemore, University of Oxford & former Chief Executive of the MRC, said:

“It’s hard to judge the significance of this study without seeing the details. But on face value it appears to contradict the results emerging from Lyle Armstrong’s research in Newcastle where they have derived apparently functional stem cells from cybrid embryos. Either way it would certainly be premature to conclude that this technique will be of no value. Indeed even if this research is replicated, it will provide important information about the re-programming process. Far from suggesting that these results mean that the debate over hybrid embryos was ‘a waste of time’, all such findings show how important it was that the HFE Bill allowed for such research to go ahead in the UK.”

Prof Robin Lovell-Badge, Head of Division, MRC National Institute For Medical Research, said:

“Although interesting, I find this paper a little lacking, both technically and in imagination. If true, it suggests that there is something missing in rabbit or cow eggs, but which is present in human eggs, that allows the somatic cell nucleus from human cells to be reprogrammed. Rather than give up trying, as the authors imply, I would want to do even more experiments to find out what this is. It could be a very important factor to provide understanding and to help reprogramming in other ways.

“But I am not sure it is true. The genome in the early embryo needs to be “kick-started” to begin the programme of gene activity required for early development. This probably depends on factors in the cytoplasm of the egg, but the precise stage at which these work is species-dependent: at the 2-cell stage in mice, around 4-cells in humans, and the 8-cell stage in rabbits and cows. Lanza and his team looked for reprogramming in the cloned embryos not long after the 8-cell stage. But quite possibly this was simply too early for the interspecies combinations: they should have waited another day. Furthermore, they used culture medium designed for the species of egg that was used. If reprogramming begins to occur, then the embryos may suffer if the medium was inappropriate for the species from which the nucleus was obtained. It follows that the human into rabbit or cow would do less well than human nucleus into human egg. Perhaps they should have tried to change the medium to one appropriate for human embryos at the 4-8 cell stage.”