A Stem-Cell Revolution
Biologist Doug Melton talks about how disease-specific stem cells will reshape medicine.
Scientists at Harvard University recently announced a much anticipated milestone in regenerative medicine: the creation of stem cells from patients with a variety of diseases. The cells, which can be encouraged to develop into cell types damaged by disease, such as the insulin-producing cells in diabetes or neurons in Parkinson’s, are poised to give scientists an unprecedented view of disease.
Scientists have hoped to create such cells for more than a decade, initially attempting the feat through human cloning. But cloning proved more challenging than expected, and it wasn’t until the introduction of a novel technique, developed recently in Japan, that they succeeded. By exposing a patient’s skin cells to four genetic factors found in the developing embryo, scientists can turn back the clock, triggering the cells to look and behave like embryonic stem cells. Known as induced pluripotent stem cells (iPS), they eliminate the need for human eggs or the creation or destruction of embryos, thus bypassing major ethical and technical hurdles that have plagued the field of embryonic stem-cell research.
The scientists who created the cells at the Harvard Stem Cell Institute, including George Daley and Kevin Eggan, now plan to distribute them to colleagues around the world. Doug Melton, codirector of the institute and a longtime champion of stem-cell research, talks with Technology Review about the future of the field.
Technology Review: Why are disease-specific cell lines so important?
Doug Melton: If a patient has Parkinson’s disease, their dopamine-producing cells are gone. We don’t understand anything about what makes those cells go away–the field is kind of stuck because you can’t watch the progression of the disease.
Stem cells can make neurons in a dish. Imagine you have iPS cells from a healthy person and from a Parkinson’s patient. If you make dopamine neurons from both sets of cells in separate dishes, you can look at what went wrong with the diseased stem cell. The same approach will work with different degenerative diseases, such as diabetes or ALS [amyotrophic lateral sclerosis, a motor-neuron disease].
TR: How long will it take to get insight into these diseases?
DM: For ALS, Kevin Eggan published a paper on mice showing he could see a defect in cell survival in motor neurons [made from cells derived from an animal model of the disease]. He is now looking for that defect in human cells. The next step would be to determine if that defect is the same in all patients.
TR: Where will this field go in the future?
DM: I think it will change the way degenerative diseases are studied–we’ll reduce the whole process of disease to a petri dish. Within a few years, researchers the world over should have access to disease-specific cells that can be turned into cell types defective in a particular disease.
We can also start to study environmental factors. We know sun is important for skin cancer, and smoking is important for lung cancer. But what do we know about Parkinson’s, Alzheimer’s, ALS, and diabetes? That’s hard to study in people because there is a long time between the proximal cause and effect.
Now, scientists can start to think more about how to look at environmental factors in a dish. Let’s take food, oxidative insults, pesticides, and extracts and ask how they affect the cells. Scientists can also screen for drugs that slow or stop degeneration of those cells. If that were successful–and now we’re talking about a decade-long project–you could make a drug that would slow or stop disease progression.
TR: The Harvard Stem Cell Institute is planning to distribute these cell lines to scientists. Why?
DM: Science clearly works best when you have a lot of bright, motivated people working on these problems. The institute has sent thousands of human embryonic stem-cell lines to hundreds of labs all over the world. We like to think that has been helpful in encouraging basic research on embryonic stem cells. The new cells reported by George Daley and his colleagues may be in some instances even more helpful. They are more than just iPS cells; they are disease-specific stem cells.
TR: Do Harvard scientists plan to make more cell lines?
DM: Yes. These first lines are just the beginning.
TR: Why do you plan to make multiple lines for a single disease?
DM: To continue with the Parkinson’s example, suppose you have 50 people with Parkinson’s disease. We know that when they have the disease, dopamine neurons are gone. But we don’t know how many different ways their neurons are destroyed. Are there 50 different ways those neurons go kaput? It’s possible that in every case genetics and the environment conspire to make the same defect in the life of those neurons. If we’re going to watch the cells become defective, we want to make 50 dishes from 50 different patients. I hope they all get defective in the same way; that would make it much easier. If not, each variation might require its own strategy for treatment.
TR: How much will the cells cost?
DM: There will be a nominal cost for academics. We don’t have a plan for industry yet.
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