BioWorld International Correspondent

LONDON - One of the UK's leading medical organizations has spoken out against government plans to restrict research involving human/animal hybrid embryos, saying such work is "vital" to the development of embryonic stem cell therapies.

The report by the Academy of Sciences comes a month after the government published a draft bill that would impose an outright ban on hybrids that involve fusing gametes. And while the government accepted in the preamble to the bill that there is a good case for allowing embryos to be created by fusing human adult cells with enucleated animal oocytes, the proposed bill as it stands would not allow that research either.

In its report, the academy, an independent body comprising of 800 of the UK's leading medical scientists, acknowledged that currently there is no reason to generate hybrid embryos by mixing human and animal gametes. But Martin Bobrow, chair of the group that conducted the study, said, "Given the speed of this field of research, [we] could not rule out the emergence of scientifically valid reasons in the future."

On the other hand, applying somatic cell nuclear transfer to create embryos using an enucleated animal egg, such as a rabbit or cow oocyte with the nucleus of an adult human cells has evident value, providing a possible route to controlling the genetic make-up of embryonic stem cells. The report said that this is an "essential step if the full opportunities of disease modeling, drug discovery or individualized stem cell therapy are to be realized."

The report stressed that human eggs are in very short supply and it is therefore not appropriate to use them for nuclear transfer research. Using animal oocytes would allow research to progress without being compromised by the shortage of human eggs.

The academy argued there is a broad consensus in the scientific community that the research should go ahead. "Animal eggs could provide an essentially unlimited supply of oocytes with which to hone the techniques and skills of somatic cell nuclear transfer, allowing more rapid progress and sparing the use of valuable human eggs."

In the longer term, such research could lead to the development of methods for reprogramming adult cells to produce human embryonic stem cells.

At least three UK research groups want to use animal oocytes, both to create embryonic stem cell lines as disease models, and also to perfect the use of the technique. Two of the groups have applied for licenses under the current legislation, but the regulator, the Human Fertilisation and Embryology Authority has deferred a decision.

The current UK law permits embryonic stem cell research, under license, on human embryos up to 14 days. The academy claims there is no substantive ethical or moral reason not to allow research on embryos based on animal oocytes under similar regulatory controls.

In such a rapidly moving scientific field, it is impossible to create an exhaustive list of techniques that should be allowed or banned, the report concluded. "We are concerned that a general prohibition on research involving human embryos incorporating animal material will not provide sufficient flexibility for research to proceed in a timely and effective manner."

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