iPS Takes Another Step

Although we are still celebrating President Obama’s executive order on stem cell research, it’s important to remember that the policy change was proceeded by new research involving the creation of virus-free induced pluripotent cells. The discovery came courtesy of Rudolf Jaenisch’s team at the Whitehead institute.

Publishing their research in the journal Cell, the group described a method for turning adult human skin cells into pluripotent stem cells and then differentiating them into nerve cells without leaving in the tumor-causing viruses or DNA sequences that are also needed to make the cells pluripotent.

The team was also able to turn the iPS cells into the specific kind of nerve cell that deteriorates in Parkinson’s disease. These are the nerve cells that produce dopamine, which is a neurotransmitter that transports reward signals between nerve cells.

As in previous techniques, Jaenisch’s team utilized three viruses to induce pluripotency, each of which contained one of the three reprogramming genes. The LA Times noted that unlike previous techniques, however, these reprogramming genes had added DNA sequences at each end known as loxP sequences. After the cells had been reprogrammed, the team used enzymes to cut out everything between the loxP sequences. The result was tumor-free dopamine producing nerve cells.

This technique is different from the one used in the study published in the online editions of Nature two weeks ago. Instead of using a virus to deliver the reprogramming genes, that technique attached each reprogramming gene to a delivery gene known as a transposon. That technique also used four reprogramming genes instead of three.

Based on comments from Dr. Anders Bjorklund of Lund University in Sweden, The New York Times notes that there are still several more steps required before these reprogrammed dopamine-producing nerve cells can be made identical to the nerve cells that are found in the brain region called the substantia nigra, which Parkinson’s affects directly. Also, before transplantation is even considered, scientists need to prove that all of the reprogrammed cells are fully mature since there is still a risk of tumor formation with immature cells.

We still have much to learn about the complete molecular and developmental mechanics of the cell. Only then can we work out all of these kinks in the reprogramming process. And for that, we need to research human cells going all the way back to the embryonic stem stage.

Image: Neural Cells by flickr.com/neurollero

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