Science in Mind

Scientists clone human embryonic stem cells -- finally -- but now seen as minor advance

A stem cell colony developed from cloned human embryos.
A stem cell colony developed from cloned human embryos. Credit: Oregon Health & Science University

Less than a decade ago, the quest to clone human embryonic stem cells fueled a heated scientific race toward a technology that seemed to hold the promise of transforming medicine, by giving doctors the power to create replacement parts customized for individual patients. The quest was front page news and sparked ethical debates.

Harvard University launched an effort to clone human cells in 2006. A major scandal erupted when a South Korean scientist claimed he had successfully cloned embryonic stem cells and then was revealed to be a fraud. A biotech company founded by a fringe movement claimed in 2002 to have cloned such cells and used them for reproductive purposes, generating a media firestorm.

On Wednesday, scientists from Oregon Health and Science University finally—and apparently legitimately—declared success. Yet their paper, published in the journal Cell, is generating little excitement. It is a key technical advance, but not a breakthrough.

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The discovery would no doubt be a bigger deal if in 2007, scientists had not discovered that there was a different, simpler way to create stem cells that bear a patient’s own genome and are pluripotent, possessing the capacity to develop into any of the myriad cells and tissues in the body. Instead of replacing the genetic material in an egg with the genome of a patient—the procedure known as cloning—the researchers found they could flip genetic switches that turned back time, reprogramming normal skin cells and turning them into embyronic-like stem cells.

This method negated the difficult need for egg donors, and avoided many of the ethical quandaries that had bogged down the field. The developers of the powerful alternate technique received the Nobel Prize in short order, in 2012 and the number of laboratories working on stem cell research widened.

Many teams moved on, no longer attempting to clone embryonic stem cells the other way. Harvard researchers published papers as recently as two years ago explaining some of the technical difficulties with traditional cloning, reporting that they had almost done it—except that the cells’ development screeched to a halt without an extraneous genome. But Douglas Melton, co-director of the Harvard Stem Cell Institute, said in an interview this week that no one there is working on the technique anymore.

Shoukhrat Mitalipov, a senior scientist at the Oregon National Primate Reserach Center who led the new work, said the method adds a new class of pluripotent cells to scientists’ toolkit. Those cells could be compared to the reprogrammed stem cells and to true embryonic stem cells, to better understand them. He also noted that the technique, unlike reprogramming skin cells, would give researchers a way to correct genetic glitches that might exist in mitochondria, the power plants of the cell.

Melton said that the paper described a significant advance for the field, but added that a number of factors made it unlikely to have a broad impact on stem cell research. The emergence of reprogrammed stem cells, the difficulty of the involved method, and the obstacles to obtaining donor eggs for the procedure all make the advance more an important technical feat than a game-changer for stem cell scientists or a platform for new therapies.

And so a major quest in science comes to an end, in a saga that shows how a major scientific quest can fall to the wayside with advances in technology and knowledge. Moreover, grand scientific missions are often just the first step toward transforming human health. Even if the technique turns out to have some advantage over reprogramming, what lies ahead is the long road toward taking a technique and turning it into something that could be a useful therapy.

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