What is the future of stem cell research? Embryonic cells were once so controversial that President George W. Bush limited federal funding in 2001 (a policy that was overturned by President Obama in 2009). Now there is a new type of stem cell, similar to embryonic stem cells, called induced pluripotent stem cells. We’ve all heard the claims concerning the extraordinary potential of stem cells (be they embryonic or induced) in the treatment of human disease. What will be the first commonly used stem cell therapy?
The first human embryonic stem cell lines were grown by Dr. James Thomson in Wisconsin in 1998. These cells had the ability to make every cell type in the body, an unlimited source of material, but we couldn’t yet use them to study disease. In 2006, Dr. Shinya Yamanaka, this year’s Noble Prize recipient, was trying to understand what made embryonic stem cells so special. Why did they have this special ability to turn into, to differentiate, into all other cell types? And he narrowed it down to just four genes. If you turn four genes on in a skin cell, it gains this ability to make all other cells types – it becomes an induced pluripotent stem cell.
Many people imagine that the future of stem cell research is cell replacement therapy. That is to say, they imagine that doctors will one day use stem cells to grow new nerve cells to repair the spinal cord in a paralyzed patient, inject new retinal cell into the eye of a blind person, or even just inject new cartilage into their aging knee. These treatments could all become reality, and in fact, clinical trials for many such possibilities are already underway. Though charlatan clinics have sprung up around the world to take advantage of desperate patients, the truth is that it will be years before stem cell replacement therapies are routine and affordable options – issues ranging from immune rejection, the possibility of stem cell derived tumors, and technical obstacles in generating sufficient cells in a timely manner will all need to be overcome.
What should not be forgotten in the hype of stem cell replacement therapies is the other major promise of stem cell research: suddenly, practically overnight, scientists gained the ability to make stem cells from every person on the planet. And by making stem cells from anyone, they can make stem cells with any disease, and from these, make the cell types affected by any disease, and then watch them get sick.
In fact, that’s precisely what my laboratory does. We obtained skin cells from patients with schizophrenia and from healthy controls. We turned the skin cells into brain cells, and then compared them. Our goal is to observe what is going wrong, understand why it is happening and then discover how to prevent it. We have learned that in many ways, the brain cells from schizophrenic patients are the same as those from healthy controls. But in a few important ways, we can already see how they are different; for example, they don’t connect to each other as well. Our goal is to use our near limitless supply of live human neurons affected by schizophrenia to screen thousands of drugs, hoping to find one that improves the connections between schizophrenic brain cells. The hope is that this type of drug might help patients too.
So when you think of stem cell research, remember that scientists are working in two directions. Some are trying to replace diseased cells with healthy cells in patients. And others are using diseased cells in the laboratory to identify new drugs with which to treat patients. In fact, the first stem cell derived therapies might just arrive in pill form.
Kristen Brennand, PhD
Assistant Professor of Psychiatry and Neuroscience