Turning Cells Into Stem Cells: No Retroviruses Required

In the last few months there has been a downpour of discoveries in the area of stem cell research. Three of the latest findings reveal new ways to turn back the clock on mature cells and transform them so that they resemble the cells of human embryos. As a result, scientists may be closer to the goal of using new stem cell therapies to treat diseases, from Parkinson’s to diabetes.

The embryonic state is desirable because these cells have the potential to become any type of cell in the human body. Last year, two studies showed that human skin cells could be ‘reprogrammed’ into cells that behave like embryonic stem cells. The scientists achieved this by inserting just four genes into the skin cells.

However, this method for creating stem cells came with drawbacks. In order to insert the genes, scientists had to use viruses that can cause cancer in humans. These recent studies use alternative techniques for transforming cells into an embryonic-like state

The first method, published online in Science Express, an outlet for papers that will appear in the journal Science, still uses viruses, but of a different type. Scientists previously used retroviruses, which are good at transporting genes into cells. Once inside, however, they integrate themselves into DNA and can make the cell cancerous. In the latest study, researchers at Harvard have found a way to insert genes into cells using adenoviruses, viruses that do not integrate into DNA. This method reduces, but does not eliminate, the cancer risk.

Another study reprogrammed cells using a completely different approach. The paper, published in a recent on-line issue of Nature, showed that cells from human testes can be turned into cells that are similar, but not identical, to embryonic stem cells by using specific chemicals and growing conditions. The scientists were able to coax these cells into various cell types, including muscle, bone, and neural cells.

Finally, another study published in Science Express, showed that the genes critical for transforming cells back into an embryonic-like state can be inserted without using a virus at all. Instead, the researchers used a plasmid vector, a circular piece of DNA, to insert the genes. However, this technique was much less efficient than the retrovirus method.

Although none of these methods are ready for human use, they represent progress toward beneficial therapies using stem cells.

—

Related on Scienceline:

Listen to an audio podcast about the controversy surrounding embryonic stem cells.

A company proposes using stem cells to treat the injuries of professional athletes.