Facts of artefacts—epigenetic or episcientific?

Jacques Testart

INSERM Unité 355, 32 Rue de Carnets, 92140 Clamart, France

Dear Sir,

My contribution to the debate on `safety of embryo cryopreservation' led me to make `a severe attack' (Testart, 1998Go) on the methodology and conclusions of the only available work on the long-term effects of this technique in mice (Dulioust et al., 1995Go). In their answer (Dulioust et al., 1999Go), the authors go to great lengths in justifying themselves, while omitting the main thrust of my criticism.

They consider that `all the embryos from one stain were genetically identical since they were F1 hybrids derived from unbred parents'. If it were so easy to obtain genetically identical embryos, cloning would be useless and gametogenic meiosis could be confused with somatic mitosis. However, over and above any possible embryonic selection effect with freeze-drying, their reply (Dulioust et al., 1999Go) leaves two important questions unanswered.

When results are obtained thanks to a policy of fishing for significant differences among the numerous pieces of experimental data, they can be suspected of statistical bias and the only way to give them scientific status is to repeat the experiment. There is a big difference between using 1000 mice to give an average result and using 200 mice five times to check whether the same result is reproducible. One can only regret that in the 4 years since their first article (Dulioust et al., 1995Go) the authors have not run such a check to put an end to the discussion.

In contrast with their opinion (Dulioust et al., 1999Go), I do not believe that publication of such data (which are hypothetical to say the least), serves `to provide full information' to couples, but rather worries them unnecessarily. If patients can legitimately request `that doctors help us to act with responsibility, even if this means not acting at all', then today's responsible answer cannot be to advise them to abstain from freezing `supernumerary' embryos. Certainly `with respect to the child, future parents and physicians share a responsibility which obliges them to face facts', but only facts which conform to proper scientific practices.

We all agree that it will be a few dozen more years before the harmlessness of freeze-drying human embryos can be accepted as a proven fact and that, therefore, the follow-up of such acts is of the utmost importance. Still, no-one can imagine that such proof will appear if the acts are never carried out. Our mission must also include not refusing to act in the absence of any serious reason to believe that a clinically useful intervention could be biologically dangerous or ethically reprehensible.

References

Dulioust E., Toyama K., Busnel M.C. et al (1995) Long-term effects of embryo freezing in mice. Proc. Natl. Acad. Sci. USA, 92, 589–593.[Abstract]

Dulioust, E., Busnel, M.C., Carlier, M. et al. (1999) Embryo cryopreservation and development: Facts, questions and responsibility. Hum. Reprod., 14, 1141–1145.[Free Full Text]

Testart, J. (1998) Episcientific aspects of the epigenetic factors in artificial procreation. Hum. Reprod., 13, 783–785.[Free Full Text]





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