IRA FLATOW, HOST:
How do you cure a disease when you don't even know what causes it? Lou Gehrig's or ALS is one of those diseases. Only 10 percent of cases are known to be genetic. The rest are sort of a mystery to scientists. Whatever the cause, once the disease sets in, motor neurons start to die off. Muscles weaken in atrophy, and eventually full paralysis can set in and the patient can no longer breathe.
My next guest has come up with a way to slow that process using stem cells. Now, be warned that the research is just very preliminary. It's in mice. It is not a cure. And so far in mice, it's just a way to stave off the symptoms of the disease. But how close could we be to human treatment? What about trials? Is there a danger to using stem cells in these patients? All good questions. Here to answer them is Evan Snyder, director of the program in stem cells and regenerative biology at Sanford-Burnham Medical Research Institute in La Jolla. Welcome back to SCIENCE FRIDAY, Dr. Snyder.
EVAN SNYDER: Oh, thanks for having me, Ira. Good to be back.
FLATOW: Sanford. Tell us a little bit about this study.
SNYDER: Well, this is a study that actually had a very long gestation. And I should say that it was triggered by a lot of questions and foresight by a very active group of ALS patient advocates called Project A.L.S. out of New York that in the early, early days of the stem cell field saw this as a potential and decided to try to bring this new biology to confront this horrible disease. And I guess I was tasked with bringing together some of the best stem cell biologists, and they brought together some of the best ALS investigators. And we just tried to see what stem cells would do in a mouse model of this terrible, untreatable disease.
FLATOW: So, Evan, tell us what you actually did. What did you do there?
SNYDER: So what we did was, first, just to see what stem cells would do in the nervous system of a mouse who had a model of this disease, in other words, was very rapidly and very progressively losing all muscular activity, including respirations. What we found - and this was a surprise at the time - in the early days, we thought, well, stem cells should simply replace these dying motor neurons. What, in fact, we found is - and this reflected a growing sophistication of our knowledge about stem cells as well as a growing sophistication about our knowledge about ALS - that the stem cells did make a difference in these animals. It slowed the onset of the disease, its progression and prolonged survival fairly significantly. But it did it by protecting the neurons of this animal and also kind of counteracting many of the other disease processes that we started learning were going on in this disease.
FLATOW: So it didn't replace the dead neurons. It just protected the ones that were still alive?
SNYDER: Exactly. What it was doing was, A, protecting those neurons and their connections from dying. B, crowding out or suppressing the cells that we now know maybe actually causing the disease and also getting rid of a lot of inflammation, making growth factors, making the cells that were there actually healthier. Many different mechanisms, all part of the fundamental biology of the stem cell.
FLATOW: But do you still have any - no one has any idea why the cells are dying in the first place?
SNYDER: No. You know, there's lots of theories and we think that maybe the cells that actually should be protecting the motor neurons are instead not only not doing that job, but actually making toxins. That's one theory. But there's many, many other theories.
FLATOW: Yeah. This is SCIENCE FRIDAY from NPR, talking with Evan Snyder about stem cell theories and practices. So this not ready to be tried in humans or are there - I understand there are phase one trials going on right now.
SNYDER: There is phase one trial going on right now, and anybody who knows me knows that exceptionally, exceptionally cautious about trying to make leaps from animal studies to humans. One of my criteria is that if one tries this in a human that is very consistent, but the biology we know about the cell and consistent with the biology we know about the disease. This, with a great deal caution, is one area where I would, kind of with a lot of care, try this in humans.
And there is a clinical trial that is completing phase one now, where the patients are getting almost like a taste of stem cells, probably not enough to make a difference, but enough to show that they will be safe, and maybe a little bit of - have a little bit of efficacy. I think we can cautiously extend those trials for this particular disease as long as we recognize exactly why the cells are working.
FLATOW: Mm-hmm. And these are not embryonic stem cells, correct?
SNYDER: Correct. These are not embryonic stem cells. These are what we would call neural stem cells. In other words, these are stem cells that come from the nervous system.
FLATOW: And why - and, I guess, you give them a little - they have a little head start knowing they're going to be neurons from being injected.
SNYDER: Exactly. Well, they, you know, they have a head start in knowing at least that they're meant to be living in the nervous system, which means that there's a little bit of built-in safety and stability that may not quite exist in cells. They can become and kind cell to.
FLATOW: And how long are they effective for in the life of the mice they're injected into?
SNYDER: Well, in the mice that we've looked at, they were effective throughout the lifespan of the animal. So they were present, having their action and, you know, ultimately the animals do die. But it raises the question of, well, what about if we re-dose the animals? Would we have an even longer effect? Would we increase even the area that the stem cells were able to engraft in? Would we have a better effect? You know, that is where the investigations now need to go.
FLATOW: All right. Dr. Snyder, thank you for taking time to be with is today and happy holiday to you.
SNYDER: Oh, happy holiday to you as well.
FLATOW: Evan Snyder, director of the program in stem cells and regenerative biology at Sanford-Burnham Medical Research Institute in La Jolla. Transcript provided by NPR, Copyright NPR.