A major obstacle to the creation of human stem cells from an adult patient's skin tissue has been overcome with the help of a little patience and a drop of caffeine, scientists have discovered.
For the first time, researchers have been able to produce human stem cells from early-stage embryos cloned from a man's skin cells using the same cloning technique used to produce Dolly the sheep nearly 20 years ago.
A previous claim that Korean investigators had succeeded in the feat turned out to be fraudulent. Then last year, a group at Oregon Health & Science University generated stem cells using the Dolly technique, but with cells from fetuses and infants.
In this case, cells from a 35-year-old man and a 75-year-old man were used to generate two separate lines of stem cells. The process, known as nuclear transfer, involves taking the DNA from a donor and inserting it into an egg that has been stripped of its DNA. The resulting hybrid is stimulated to fuse and start dividing; after a few days the embryo creates a lining of stem cells that are destined to develop into all of the cells and tissues in the human body. Researchers extract these cells and grow them in the lab, where they are treated with the appropriate growth factors and other agents to develop into specific types of cells, like neurons, muscle, or insulin-producing cells.
Reporting in the journal Cell Stem Cell, Dr. Robert Lanza, chief scientific officer at biotechnology company Advanced Cell Technology, and his colleagues found that tweaking the Oregon teams process was the key to success with reprogramming the older cells. Like the earlier team, Lanzas group used caffeine to prevent the fused egg from dividing prematurely. Rather than leaving the egg with its newly introduced DNA for 30 minutes before activating the dividing stage, they let the eggs rest for about two hours. This gave the DNA enough time to acclimate to its new environment and interact with the eggs development factors, which erased each of the donor cells existing history and reprogrammed it to act like a brand new cell in an embryo.
The team, which included an international group of stem cell scientists, used 77 eggs from four different donors. They tested their new method by waiting for 30 minutes before activating 38 of the resulting embryos, and waiting two hours before triggering 39 of them. None of the 38 developed into the next stage, while two of the embryos getting extended time did. There is a massive molecular change occurring. You are taking a fully differentiated cell, and you need to have the egg do its magic, says Lanza. You need to extend the reprogramming time before you can force the cell to divide.
The achievement was designed to produce viable embryonic stem cells ultimately for medical transplant operations, but the same technology could also be used to produce viable cloned human embryos for reproductive cloning - which is illegal in Britain and many other countries.
"The whole point of this is to help older people in the population who are more likely to suffer from the range of age-related diseases that could be addressed with embryonic stem cells, such as heart disease, diabetes or progressive disorders of the brain," Dr Lanza said.
"Although there's a shortage of human eggs, it's important to realise that the future of stem-cell technology isn't making hundreds of millions of patient-specific stem cell lines but rather making banks of matching tissue types," he said.
"In the United States, for instance, just 100 human embryonic stem cell lines would generate a complete tissue type match for over half the population. And in say Korea or Japan, you could probably get a complete tissue-type match for most of the population with less than a dozen lines," he added.
