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domingo, 19 de mayo de 2013
Human cloning developments raise hopes for new treatments
Lorraine Barnes suffered a heart attack in 2005 and has lived with the consequences – extreme exhaustion and breathlessness – ever since. "I was separated from my husband and so my children, Charlotte and James, had to grow up overnight because suddenly they were caring for me," she says.
Charlotte agrees: "It turns your world upside down. I worry about my mum day and night, 24/7."
Heart failure leaves Barnes, 49, "drowning and gasping for air", she says. What really preys on her mind, though, is not her present difficulty but her future. "It scares me, as obviously I want to be around to see my children grow up."
There is no cure for heart failure, the aftermath of a heart attack, and the condition is common. Every seven minutes a person has a heart attack in the UK, and some victims are left so weakened they can hardly walk a few metres.
Scientists have been working on such techniques (see box) for some time but their work has been hampered by the difficulties involved incloning human cells in the laboratory. But the team led by Shoukhrat Mitalipov, of the Oregon Health and Science University in Portland, got around this problem. By adding caffeine to cell cultures, their outputs were transformed. "We were able to produce one embryonic stem cell line using just two human eggs, which would make this approach practical for widespread therapeutic use," said Mitalipov.
The development was hailed as a major boost for patients such as Barnes, who might benefit from tissue transplants – and not just heart attack patients but those suffering from diabetes, Parkinson's diseaseand other conditions.
But the announcement was also greeted with horror. "Scientists have finally delivered the baby that would-be human cloners have been waiting for: a method for reliably creating cloned human embryos," said David King of Human Genetics Alert. "It is imperative we create an international ban on human cloning before any more research like this takes place. It is irresponsible in the extreme to have published this."
Several tabloid newspapers also carried banner headlines warning of the human cloning "danger". Such reactions have a familiar ring. When the cloning of Dolly the Sheep was revealed in 1997 there was an outpouring of hysteria about the prospect of multiple Saddam Husseins being created in laboratories.
"At the time the chances of these horrors occurring – when scientists had not even created a single clone of a human cell – were remote," said physiologist Professor Colin Blakemore of Oxford University. "Not that this worried the alarmists. The crucial point is that we should have spent the intervening time thinking about how we should react sensibly to the concept of a human clone when it does become possible. We have not done that and, although the science is still far off, it is getting closer. We need to ask, carefully and calmly: under what circumstances would we tolerate the creation of a human clone?"
At present such a creation is banned in Britain. No human embryo created by cloning techniques is allowed to develop beyond 14 days. "The research is very tightly regulated and I think there is little chance of a rogue laboratory creating a human clone," said James Lawford Davies, a lawyer who specialises in health sciences. "However, many US states which, ironically, banned therapeutic cloning work because of their strong anti-abortion stances have laws that would permit human clones to develop into foetuses."
Experts such as Professor John Harris, director of Manchester University's Institute for Science, Ethics and Innovation, see positive benefits in reproductive cloning which could have a place in society. He said: "If you take a healthy adult's DNA and use it to create a new person – by cloning – you are essentially using a tried and tested genome, one that has worked well for several decades for the donor. By contrast, a child born naturally has an 8% chance of succumbing to a serious genetic abnormality because of the random selection of their DNA. You can avoid that with a clone."
In fact, most arguments against human cloning are foolish, said Harris, adding: "It could be used in medically helpful ways. If a couple find they are carriers of harmful, possibly fatal recessive genetic illnesses, there is a one in four chance they will produce a child who will die of that condition. That is a big risk. An alternative would be to clone one of the parents. If you did that, then you would know you were producing a child who would be unaffected by that illness in later life.
"Or consider the example of a single woman who wants a child. She prefers the idea of using all her own DNA to the idea of accepting 50% from a stranger. But because we ban human cloning she would be forced to accept DNA from a stranger and have to mother 'his child'. I think that is ethically questionable. Just after Dolly the Sheep was born, Unesco announced a ban on human cloning. I think that was a mistake."
This point was backed by Blakemore. He said: "Many people react with horror at the thought of a human clone, yet three out of every 1,000 babies born today are clones – in the form of identical twins. These twins share not just the same DNA but have grown up in the same uterus and have had the same parenting – features that only intensify their similarities. Society is quite happy about this situation, it appears, but seems to find it odd when talking about cloning."
However, a note of caution was sounded by Ian Wilmut, who led the team that created Dolly the Sheep. He said: "The new work may encourage some people to attempt human reproductive cloning but the general experience is that it still results in late foetal loss and the birth of abnormal offspring." It would be cruel to cause this in humans until techniques had been vastly improved, he added.
However, most scientists see Mitalipov's work as encouraging. If nothing else, the prospects for Lorraine Barnes – and countless other patients whose lives could be transformed by transplants – have greatly improved in the long term.
How it works
The nucleus is removed from a human egg cell and the nucleus from a skin cell is inserted.
An electric shock fuses the skin cell nucleus inside the egg and it begins to divide into new cells. An embryo starts to form.
After a few days the growth of the embryo is halted and cultures of its constituent stem cells created.
By treating stem cells with different chemicals they can be transformed into specialised cells such as those that make up heart muscle, brain, pancreas and other organs. These cells are genetically identical to the original skin cell and can be used to create tissue for transplanting into the skin cell's donor .