PARIS, May 20: Scientists announced on Thursday they had made a giant stride forward in the tantalizing quest to transform cells harvested from early embryos into a cure for sickness. Analysts hailed the advance in stem cell research as magnificent, although they also cautioned that a technical and ethical maze still lies ahead.

Any stem cell cure for damaged heart muscle, severed nerves, Alzheimer’s, Parkinson’s and other degenerative diseases remains years away, they said. Heading two announcements was a South Korean team, which reported in the US journal Science that it had made cloned stem cells tailored to match the DNA of patients suffering from disease or spinal cord injury.

They took donated human eggs and replaced the eggs’ core of genetic programming with DNA from skin cells from people aged two to 56, who were suffering from spinal injuries, juvenile diabetes and an inherited form of immune deficiency. Using chemicals, the team then kicked these fused cells into life.

Roughly the same principle was used to create Dolly the sheep, the world’s first cloned animal, in 1996. But in this case, there was no intention at all to clone a human being.

Instead, the researchers let the embryos develop for six days, long enough to develop into a cluster of the early cells that are said to develop into any of the more than 200 different types of cells in the body. The idea behind stem cells is to coax them into growing into fresh tissue that can then be transplanted into the body to replace or replenish damaged cells.

But a big hurdle is to ensure that these replacement tissues are not rejected as hostile by the body’s immune system. Thus the interest in cloned stem cells. As they are duplicates of the body’s own DNA, they should, in theory, not encounter any rejection problem.

The South Korean team, led by Seoul National University professor Woo Suk Hwang, is in the vanguard of efforts to clone stem cells. In March last year, they became the first to carry out stem cell cloning, but they used an egg and a programming nucleus that came from the same donor, a healthy female.

This time, the egg and the programming DNA are from different people, which in itself is a major step forward. Just as significant is the numbers of cloned embryos and stem cell lines, thanks to major improvements in handling the eggs and replacing their nucleus.

In addition, the chromosomes of the cloned embryo and of the donor were apparently identical, which suggests that the operation had been carried out without damage to genes. And there was a reduced use of animal enzymes and serum in the chemical “bath” in which the cloned egg is placed.

From 185 donated eggs — an enormously high number, and obtained from young volunteers — the South Koreans were able to obtain 31 clusters of cloned cells. From these clusters, called blastocysts, 11 stem cell lines developed. This success rate “is spectacular,” said Marc Peschanski, a director of research at France’s medical institute Inserm. “It’s enormous ... they have provided a real technological advance which is going to benefit everyone.”

Peschanski said the South Korean achievement destroyed a long-standing objection that it is so difficult to get large numbers of cloned embryos that stem cell research is not worth pursuing.

In parallel, a team at Britain’s Newcastle University also announced it had successfully produced a cloned blastocyst, although details remained sketchy and the work has yet to be published in a peer-reviewed journal.

TWO CHALLENGES: Despite the success, two big challenges remain before stem cells can ever be used as a therapy.

In the lab, scientists must learn more how stem cells can be coaxed into developing into specific tissues. They must also figure out how this novel material can be transplanted without causing cancer.

Another is ethical, given the objections in some quarters to the use of embryonic cells and the almost universal repugnance about reproductive (as opposed to therapeutic) cloning.

“If, as they claim, these South Korean scientists can reliably produce cloned embryos healthy enough to survive to the blastocyst stage for cell harvesting, we can assume that they can reliably produce embryos healthy enough to try implanting them in women,” the British anti-abortion charity Life said. “This Frankenstein science should be banned in every civilized society.”—AFP