Even if they do not want to clone babies, researchers must to learn how to produce duplicate human cells safely. That is the conclusion of experts who have outlined an ambitious program to identify and solve the problems that currently plague cloning.
Only a few renegade scientists claim they are ready to clone human beings, but many biologists are interested in using cloning techniques to genetically-match cells to patients for use as rejection-free transplants, and for research.
But Ian Wilmut, of Scotland’s Roslin Institute, says even these plans should be shelved until more is known about how cloning works – and why it fails so often. “There are a lot of questions to ask about cloned cells before you can justify putting them in a patient,” he told New Scientist.
Wilmut and his colleagues argue that the only way to answer those questions is to thoroughly dissect the failures of animal cloning, rather than continue to celebrate its successes.
“They are very fair and thorough,” says Robert Lanza of the cloning company Advanced Cell Technology in Massachusetts. “They lay out the way it is and where we need to go from here.”
In all uses of cloning, a cell from a donor is fused with an egg from which the genetic material has been removed. To create a live clone, the resulting embryo is implanted in a surrogate mother.
In therapeutic cloning, the embryo is destroyed to harvest embryonic stem cells (ESCs), special cells which can transform into any type of tissue. If the donor was a patient, then the stem-cell-derived tissues should be compatible with that patient’s immune system.
Wilmut’s team reported the birth of Dolly the sheep – the first clone of an adult mammal – five years ago. But despite much progress since then, the vast majority of embryos cloned for reproductive purposes continue to die before birth. Even the survivors can suffer from many life-threatening abnormalities.
Almost all scientists agree this makes cloning humans far too dangerous to contemplate, but many hope to develop the therapeutic uses of cloning. A few groups already claim to have harvested ESCs from cloned human embryos, though those results are not yet widely accepted.
But when cloned human ESCs become available, Wilmut says researchers need to realise they might also pose a risk to patients. For instance, gene activity in many animal clones is abnormal. So tissues created from cloned ESCs may also function abnormally, potentially triggering cancers or other diseases.
Little is currently known about what causes these problems with gene expression, because researchers have focused on creating and studying the few healthy animals created. Most of the data on dead ones is literally thrown away.
Instead, Wilmut says cloners need to systematically study every aspect of the cloning process, its genetic and physiological effects on embryo, placenta, fetus and live animal. In his plan, clones would be compared side by side to natural embryos and test-tube fertilised embryos.
Lanza at ACT agrees that the results from such studies would be tremendously valuable. However, he also points out they will be extremely expensive. “We have investors who want results yesterday and want products in the clinic,” he says. “They aren’t going to fund a Manhattan project for cloning.”
But Wilmut thinks the work would attract many academic labs because it could yield insights on basic issues in developmental biology. His team has already submitted one proposal to a funding agency aimed at cracking some of the mysteries of cloning.
“It was not successful,” he says. “But we’ll be seeking more funding, and I think we’ll get it.”
Journal reference: Nature Reviews Genetics (vol 4, p 855)