Human sperm and eggs will be grown from stem cells within five to fifteen years but the technology will not allow gay and lesbian couples to conceive children with genes from each partner, an international panel of scientists predicted yesterday.

While such artificial gametes (reproductive cells) could be used to treat infertility, the biological barriers to creating sperm from female cells and eggs from male ones will make same-sex conception impossible for the foreseeable future, according to the Hinxton group of leading stem-cell researchers.

Mouse sperm grown from stem cells have already been used to fertilise eggs and produce live pups, and the success has suggested that the technique could allow men and women who make no gametes of their own to have children.

Cells from an infertile man or woman would first be reprogrammed into an embryonic state, or used to make cloned embryonic stem cells. The resulting stem cells would then be turned into sperm or eggs, which would carry the patient’s DNA.

The research has also prompted speculation that sperm could be produced from a woman or eggs from a man, allowing lesbian or gay couples to have children to whom both partners make an equal genetic contribution. Some campaigners who object to the technology have even argued that it could lead to “ultimate incest”, by which a single person becomes mother and father of a child.

Researchers, however, dismissed the prospect of male eggs and female sperm as science fiction in the new Hinxton group report.

Human sex is determined by the inheritence patterns of the X and Y chromosomes: women have two copies of the X, while men have one X and one Y. As several genes that are critical to sperm production are carried on the Y chromosome, this will make it “difficult or even impossible” to turn female cells with two X chromosomes into sperm under any circumstances currently known to science.

The production of eggs from male cells is a little less problematic, but even this is likely to be “very difficult”, the report said.

Professor Robin Lovell-Badge, of the National Institute for Medical Research in London, a member of the group’s steering committee, said: “It would be very difficult to get eggs from XY cells, and even more difficult to get sperm from XX cells – my own view, indeed, is that the latter is impossible.”

Under the Human Fertilisation and Embryology Bill currently passing through Parliament, laboratory experiments with these cells will be permitted, but it will be illegal to use them in fertility treatment.

MPs are expected to table an amendment that would allow Parliament to approve their clinical use in the future, without recourse to primary legislation. Professor Lovell-Badge said he would support such an amendment. An American scientist has suggested that a new method for reprogramming adult cells into an embryo-like state could be used to produce genetically engineered children.

Stem cells produced with the technique could be added to human embryos, so that they developed into “chimeras” that contain cells with two distinct genetic signatures, according to Robert Lanza, of Advanced Cell Technologies.

Other scientists, however, questioned the usefulness of this approach, which would in any case be banned in Britain. Professor Lovell-Badge said: “I cannot think what might be gained by doing this.”

Reproductive cells

— Mouse sperm grown from stem cells have been used to fertilise eggs and produce live pups. All seven of the pups died prematurely, however

— Years more research will be needed to prove it is possible to make human sperm and eggs from stem cells, and to ensure embryos produced are normal

— Scientists expect it to be easier to make sperm from stem cells than eggs

Source: Times database / Hinxton Group

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