Health

After years of failed attempts, researchers have finally generated stem cells from adults using the same cloning technique that produced Dolly the sheep in 1996.

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.

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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.

VIDEO: Breakthrough in Cloning Human Stem Cells: Explainer

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.

While a 5% efficiency may not seem laudable, Lanza says that its not so bad given that the stem cells appear to have had their genetic history completely erased and returned to that of a blank slate. This procedure works well, and works with adult cells, says Lanza.

The results also teach stem cell scientists some important lessons. First, that the nuclear transfer method that the Oregon team used is valid, and that with some changes it can be replicated using older adult cells. It looks like the protocols we described are real, they are universal, they work in different hands, in different labs and with different cells, says Shoukhrat Mitalopov, director of the center for embryonic cell and gene therapy at Oregon Health & Science University, and lead investigator of that study.

Read more:
Researchers Clone Cells From Two Adult Men

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