杏吧原创

ETHICAL objections to harvesting cells from embryos face a challenge from the results of experiments on cloned frog embryos. Though the embryos were severely abnormal, and so were doomed to die, they still yielded useful cells. If the findings are repeated in human embryos, it could mean that valuable cells for therapy or research could be extracted from abnormal human embryos.

Many people object to destroying embryos that could eventually develop into a human. But an embryo destined to die within days is not a potential human, argues John Gurdon of the Wellcome Cancer Research Institute in Cambridge. 鈥淚f an embryo is certain to die, I can鈥檛 see why anyone would object to someone taking cells and working with them.鈥�

Gurdon has shown that even cloned embryos that will die contain normal stem cells that can develop into many tissue types. He made the clones using frogs鈥� gut cells which he fused into frog eggs emptied of their own genetic material.

Half the embryos Gurdon created failed to divide at all. Another quarter became 鈥減artial embryos鈥� in which normal cells developed in only part of the embryo. These embryos looked abnormal and died a day later.

But before they succumbed, Gurdon was able to extract normal cells and graft them into healthy frog embryos. As the embryos developed, Gurdon was able to spot tissues from the grafted cells because they glowed green, thanks to a gene he had inserted into the frogs that supplied the gut cells. 鈥淪ome of the cells from the cloned embryos did well, and amazingly grew for months in the new host embryo,鈥� says Gurdon.

If the same is true for human embryos, it would be possible to extract cells from them for growing into tissues for patients. Many of the human embryos produced at fertility clinics are visibly abnormal and will die within three days.

In Britain, campaigners opposed to abortion say harvesting cells from dying embryos would be acceptable, provided this does not in itself destroy or shorten the defective embryo鈥檚 life. 鈥淚t would only be acceptable if the embryo was allowed to live out its natural lifespan, even if it鈥檚 only three days,鈥� says Josephine Quintavalle of the Pro-Life Alliance.