Last week, British transport secretary Ruth Kelly's resignation, plus new developments in creating stem cells again brought this controversial area of medical science into sharp focus. Claire O'Connellreports
STEM CELLS are rarely far from the headlines and last week was no exception, with both breakthroughs and barriers up for discussion.
On Thursday, Harvard scientists published details of a new way to take mature cells and generate functional stem cells that could be useful for treating disease.
Meanwhile, the resignation announcement of British transport secretary Ruth Kelly dredged up discussions about stem cells derived from animal-human hybrids, which she opposed earlier this year on religious grounds.
So what does it all mean? Stem cells have the potential to develop into many different cell types and so could bring enormous therapeutic possibilities for conditions where adult cell function is lost, such as Parkinson's disease or following a heart attack.
In theory, "embryonic" stem cells are the most versatile type, but sourcing these cells raises ethical concerns because it involves destroying human embryos.
That's why scientists around the world are trying to come up with ways of growing stem cells that act like they come from a human embryo, but which can be plentifully, ethically and safely sourced from adult tissue.
Earlier this year a landmark experiment in Japan successfully added viruses to isolated mature skin cells in the lab to "reprogram" them to act like embryonic stem cells. But there were concerns that these retroviruses, from the same family as HIV, increased the risk of cancer.
That worry was somewhat allayed last week with news that researchers in Boston repeated the trick on mouse skin cells but with a less risky "adenovirus" - from the same family as the common cold virus - and generated functional stem cells.
Even though the newer virus is less efficient at reprogramming the cells, it's a move in the right direction, according to Prof Frank Barry, scientific director at the Regenerative Medicine Institute (Remedi) at NUI Galway.
"It's a very helpful step forward as these viruses are generally regarded as being much safer," he says. "It seems that these cells now are even closer to being available for testing. However, the next step will be to repeat the experiment using human cells, not always an easy feat."
Meanwhile, another route to making functional stem cells has been raising eyebrows. The approach takes an egg cell from an animal (often a cow), takes out the bulk of its DNA and replaces it with DNA from a mature human cell (usually a skin cell).
"What's created is a hybrid, which contains genetic material which is human but it's encapsulated within an egg cell, which is derived from an animal source," explains Barry.
Scientists then grow the animal-human hybrid to embryo stage in the lab, so they can take stem cells out for research.
But Barry says it's unlikely that a full-term hybrid could be grown at this stage. "That hasn't been done and theoretically it's possible but it's very unlikely at this moment that we would be able to - it's a remote possibility."
And why use animal egg cells in the first place? Putting DNA into an egg in the lab is an inefficient process, and the approach requires large numbers of eggs to generate a cell that will divide and grow. Such quantities of eggs would be practically and ethically difficult to source from humans, explains Barry.
"It fails to work so frequently, that is an issue," he says. "The efficiency is strikingly low and our understanding is still poor about the biology of this entire process."
Barry knows of no group in Ireland that is attempting to create animal-human hybrids, but a handful of centres are working on it in Britain, where under law the hybrid embryos must be destroyed after 14 days.
Last May, the British parliament approved such research despite objections from some Catholic MPs, including Ruth Kelly, who objected to animal-human hybrids.
But Barry argues against such opposition. "It sounds scary and people react to it but I don't think it's any different than giving a human being a pig-heart valve," he says. "There are all sorts of places where we can find troublesome ethical questions but I don't think this is one of them."
However, he also warns that despite the hype, embryonic stem cells have yet to prove their medical mettle in large trials.
"I think there's a great deal of imprudent haste in this area because we still don't know truthfully whether embryonic stem cells will work or not, the database [on testing in human disease] is very limited.
"So we are jumping ahead very quickly into these other technologies like the reprogrammed cells and the animal [hybrids], when we don't know yet whether the original technology will work really," he says.
"The large, multi-centre randomised, controlled trials that are needed to be certain about all of these, those haven't been done."