Taylor, Alison S.; (1996) Human parthenogenesis. An investigation to determine whether human parthenogenetic embryos can be used as an alternative model for embryo research. Doctoral thesis (M.D), UCL (University College London).

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Abstract

Research involving the use of human embryos has resulted in the development of assisted conception techniques and has also facilitated the development of other potential uses of IVF such as preimplantation diagnosis of genetic disease. However, it also provokes intense ethical debate and, with increasing numbers of assisted conception units offering cryopreservation, the number of embryos available for research is likely to decline. The proposal under investigation was that human parthenogenetic embryos may provide a useful alternative source of material for embryo research. The historical background to the development of in vitro fertilisation, embryonic development, the problems of performing embryo research and alternative models for such research are reviewed. A series of experiments are presented which examine how closely the development of human parthenogenetically activated oocytes and their ability to synthesise DNA and proteins conform to those observed in fertilised embryos. Blastomeres obtained from parthenogenetic embryos were used as a template for DNA amplification using the polymerase chain reaction (PCR) in order to test whether there might be a practical application for these embryos. It was possible to induce parthenogenetic development in 69% oocytes exposed to the calcium ionophore A23187 and activation rates were found to be related to culture media, patients age and previous obstetric history, oocyte grade and age of oocyte at activation. Cleavage is possible in the absence of the paternal genome and parthenote embryos appear similar morphologically to normally fertilised embryos. However, most of the parthenogenetic embryos showed developmental arrest at the 2-4 cell stage, the possible reasons for which are discussed. DNA content measurement confirmed the assumption that single proncleate oocytes have a DNA content compatible with a haploid chromosome complement while those with 2 pronuclei are diploid, and showed that parthenogenetically activated oocytes are capable of replicating their DNA. Attempts to characterise the protein synthetic patterns of parthenogenetic embryos were beset with problems which are discussed. Signals were obtained for the two loci amplified by PCR, although the amplification efficiency appears to be lower than that observed for fertilised embryos, the reasons for which are considered. It was concluded that the developmental arrest observed is likely to be the biggest obstacle to the extensive use of human parthenogenetic embryos in research, and presents an interesting challenge to overcome. Nevertheless, it may be possible to use parthenogenetically activated oocytes as a model for the early stages of human development, at a time when fertilised embryos are rarely available.

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