5 questions: Reijo Pera on stem cell progress

Renee Reijo Pera

Major advances in stem cell research have been reported by three sets of researchers worldwide in the past few weeks, giving promise to similar lines of work being done by School of Medicine researchers.

Researchers from Wisconsin and Japan announced on Nov. 20 that they had reprogrammed adult human skin cells to act like embryonic stem cells. A week earlier, researchers at the Oregon Health & Science University reported they had produced primate embryonic stem cells from adult monkey cells using nuclear transfer, a technique that requires creating an embryo to extract genetically identical stem cells.

Medical Center Report's Amy Adams discussed these findings with Renee Reijo Pera, PhD, director of human embryonic stem cell research, who is one of those hoping to generate human embryonic stem cells using nuclear transfer.

1. What is significant about last week's reports from Wisconsin and Japan?

Reijo Pera: These two groups of researchers both took skin cells from an adult human and reprogrammed the nucleus so that the cells behaved like embryonic stem cells. The resulting stem cells are an exact match to the person who donated the adult cell. This work avoids the need to use human eggs and doesn't produce an embryo, avoiding what some consider to be an ethically troubling aspect of nuclear transfer.

2. What is significant about the Oregon primate results?

Reijo Pera: That work is the first time people have used a process called nuclear transfer to generate embryonic stem cells in a primate, giving hope that it can one day succeed in humans. In nuclear transfer, researchers remove the nucleus from an egg and then replace it with the nucleus from an adult cell. After a few days the resulting embryo contains embryonic stem cells that can be pulled out and grown in a lab dish. The newly created stem cell lines are an exact genetic match for the animal that donated the nucleus. This is the same technique that a research group in South Korea claimed to use to generate human embryonic stem cell lines in 2004, only to have the work refuted in 2006.

3. Why are these two advances important for people hoping to find cures for human diseases?

Reijo Pera: Producing embryonic stem cells that are genetically identical to a person is an important step toward learning how to use embryonic stem cells in new therapies and will also be a valuable research tool. Embryonic stem cells created from a person with a genetic disease could help researchers understand how that disease develops and might eventually lead to new ways of preventing or treating the disease. These genetically identical stem cells could also be transplanted into a person with a disease such as Alzheimer's without triggering an immune reaction.

4. As someone who has attempted nuclear transfer to create human embryonic stem cell lines, does the Oregon work make you more optimistic about your chances of success?

Reijo Pera: It gives us hope that you can do this work in primates. There's been widespread skepticism about human nuclear transfer. One of the concepts in the field of stem cell research is that it might be impossible for some biological reasons to carry out nuclear transfer in primates, including humans. That had dampened enthusiasm for doing the work in humans. If the nonhuman primate work is verified and repeated, then it's likely that some aspect of the protocol will also be successful in humans. The first author of that paper, James Byrne, PhD, recently came to Stanford, where he is helping us recreate that protocol for humans.

5. Now that researchers have reprogrammed adult human cells, is it still necessary to pursue nuclear transfer in humans?

Reijo Pera: Yes, for two reasons. First, we don't know which approach will be the most successful long-term. We want to pursue all avenues that could lead to new therapies for disease. Also, my personal interest is in the earliest stages of human development. You can't study those early events in reprogrammed adult cells. Nuclear transfer will give us a way of studying the events that are critically involved in human fertility and in the chromosomal rearrangements that can lead to birth defects. We can make important advances in women's health by continuing to pursue nuclear transfer.