Embryology

House of Lords written question – answered on 16th July 2008.

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Photo of Lord Alton of Liverpool Lord Alton of Liverpool Crossbench

asked Her Majesty's Government:

Further to the Written Answers by Lord Darzi of Denham on 21 April (WA 234), 2 May (WA 109—10), 19 June (WA 177—78), 24 June (WA 227 and 1 July (WA 27—8) regarding the evidence available to the Human Fertilisation and Embryology Authority (HFEA), to what extent the scientific consensus referred to was based (1) on personal opinions and (2) an objective analysis of all published data; and whether they will provide references for all scientific papers considered by the HFEA which demonstrate (a) the potential of currently licensed cytoplasmic hybrids to develop into a human being if implanted in a woman; and (b) the intrinsic lack of potential in any embryo cultured on a layer of feeder cells for more than 14 days, despite the ability of mouse embryos to develop contractions resembling a heart beat after cultivation in vitro.

Photo of Lord Darzi of Denham Lord Darzi of Denham Parliamentary Under-Secretary, Department of Health, Parliamentary Under-Secretary (Department of Health)

We have been advised by the Human Fertilisation and Embryology Authority (HFEA) that the scientific consensus formed was largely based on an extensive review of published literature on the scientific context and biological issues surrounding the creation of human-animal embryos for research, including nuclear reprogramming, the interaction of the nuclear and mitochondrial genome and the mixing of human and animal mitochondria.

The literature review also analysed alternative avenues of research and alternative sources of stem cells. In addition, the HFEA consulted a small number of stakeholders on specific scientific questions concerned with human-animal embryos. Responses were gathered from the HFEA's Scientific and Clinical Advances Group, the HFEA Horizon Scanning Panel and external stakeholders including the British Fertility Society, Human Genetics Alert and the Motor Neurone Disease Association.

No research has been published specifically on the potential of cytoplasmic hybrids to develop if implanted in a woman. This is because cytoplasmic hybrids cannot be transferred into a woman, as this activity is prohibited by the Reproductive Cloning Act 2001. The HFEA therefore did not consider any specific studies on this as part of their consultation. However, the HFEA did consider published literature on the development of cytoplasmic hybrid embryos in vitro and on the interaction between mitochondria and nuclear DNA. This included:

Illmensee K, Levanduski M & Zavos P (2006) "Evaluation of the embryonic preimplantation potential of human adult somatic cells via an embryo interspecies bioassay using bovine oocytes". Fertility and Sterility 85(Suppl 1): 1248-60;Chen Y et al. (2003) "Embryonic stem cells generated by nuclear transfer of human somatic nuclei into rabbit oocytes". Cell Res. 13(4): 251-63;Chang K H et al.(2003) "Blastocyst formation, karyotype, and mitochondrial DNA of interspecies embryos derived from nuclear transfer of human cord fibroblasts into enucleated bovine oocytes". Fertility and Sterility 80: 1380-87;Bowles E J, Campbell K & St. John J (2007) Chapter 10, "Nuclear Transfer: Preservation of a Nuclear Genome at the Expense of Its Associated mtDNA. Genome(s)" Current Topics in Developmental Biology 77: 251-90; andSt John & Lovell-Badge (2007) "Human-animal cytoplasmic hybrid embryos, mitochondria, and an energetic debate" Nature Cell Biology 9: 988-92.

No published data on the potential of embryos cultured on feeder cells beyond 14 days were considered. This is because embryos are not permitted to be cultured in vitro beyond 14 days. This issue was therefore not considered to be relevant to the consultation.

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