Embryonic stem cells have been created by cloning adult human DNA for the first time, offering potential for producing organs that will be accepted by a patients' immune system, while also injecting new urgency into ethical debates.
It has been 18 years since Dolly the sheep became the first cloned mammal. Nuclear DNA from one sheep was put into another's egg cell with its own nucleus removed. However, while some mammalian species proved easy to clone in this way, others have been harder, including humans. The first report of successful human cloning turned out to be fraudulent, and the process stalled.
Last year Shoukhrat Mitalipov of the Oregon Health and Science University announced success in Cell, Mitalipov replaced most of the DNA in human eggs with genetic material from other people's skin cells and found a combination of chemicals (including caffeine) and electrical pulses stimulate the transformed eggs to start developing into embryos.
Mitalipov didn't go close to producing a living human being. Instead he proved his cloned embryos could produce healthy stem cells capable of turning into the cells of various organs, a far more medically beneficial move. However, his technique, while a proof of concept, relied on using the DNA from infants and fetuses.
With so much of the medical world's efforts bent towards studying diseases of aging, it would be far more useful to be able to produce stem cells using DNA from older individuals. This is what has now been announced in Cell Stem Cell.
First author Young Gie Chung of the CHA Stem Cell Institute in South Korea injected the DNA from the skin cells of a middle-aged man into eggs from four women and using a tweak on Mitalipov's technique to produce embryonic stem cells, and then did it again with even older cells. "What we show for the first time is that you can actually take skin cells, from a middle-aged 35-year-old male, but also from an elderly, 75-year-old male" and use the DNA from those cells in this cloning process,” co-author Robert Lanza of Advanced Cell Technology told NPR.
The success rate remains low, just two viable cloned cells out of 77 attempts. While this is likely to improve with practice, if it doesn't the process will be very expensive. However, as Lanza notes, “from a small vial of those cells we could grow up as many cells as we would ever want.”
However, it remains uncertain how widely this technique will be used. Induced Plutipotent Stem Cells, have been made from adult cells for eight years without using human eggs. "We now have two ways and we're not sure which of the two methods is likely to work best," says Lanza.
In theory the technique could open up a world where anyone needing a new heart, lung or kidney would have their own DNA cloned to produce stem cells that create a suitable genetically matched organ, avoiding rejection by the immune system. However, the cost obstacles to such a situation are immense. Long before this we may have a library of a small number of cloned cells, with patients being allocated organs created from the stem cells that most closely match their own DNA.
Although there are several more steps required before the technique could produce a living cloned human being, Chung and Lanza's work does move us a step closer to that possibility, reigniting ethical concerns about the possibility of people being produced specifically because they are an exact genetic match for an existing human being.
