USC Health Now

There’s much excitement about the promise of stem cells in curing a host of debilitating injuries and diseases—cancer, Alzheimer’s, and spinal cord injury to name a few. But will stem cells ever shed their controversy? A USC researcher gets to the science of stem cells and the source of the debate.

June 2, 2008
by Veronica Jauriqui

Imagine an abundant source of human cells, tissues and organs, ones that can be used to replace damaged muscle after a heart attack, re-grow spinal cord or restore the body’s ability to produce insulin. Then you can understand the excitement surrounding stem cells as a potential treatment for injury and disease.

This spring, the state of California gave that promise a boost when it awarded $271 million in grants to 12 state research institutions through its California Institute for Regenerative Medicine. USC was one of them, receiving nearly $27 million to fund construction of a five-story research center dedicated exclusively to the study of stem cells and regenerative medicine.

But the potential of stem cells is one often mired in controversy. USC Health Now asked Francesca Mariani, Ph.D., an assistant professor of cell and neurobiology and a researcher at the Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell Research at USC, to talk about the science behind the debate.

The Basics

Stem cells are the body’s starter cells. As the name implies, they are the root cells with the marvelous ability to develop into most of the body’s specialized cells—from skin and neurons, to those that make up our blood, our heart, our brain. In addition to their ability to differentiate, stem cells have the capacity to self-renew, that is, to divide frequently while still remaining in their undifferentiated state.

But that capacity to differentiate depends on the kind of stem cell they are, as Mariani explains.

“Can they become any kind of cell in the body, or are they restricted to a set of cell types or one cell type?” she says. “This is defined as its potency.”

Embryonic stem cells are considered the most potent, or totipotent, of stem cells given that they can be trained to become any kind of cell type. But along with all of their potential comes an equal share of controversy in large part because of embryonic cells’ origins.

The Debate

Embryonic stem cells originate from the blastocyst, a hollow ball of about 150 cells that forms about five days after conception. Smaller than a grain of sand, the blastocyst includes the trophoblast—which eventually forms the placenta—and the inner cell mass, from which embryonic stem cells are extracted.

The ability of these stem cells to differentiate gives hope that they can one day be used to grow tissue or even entire organs in the laboratory.

“Embryonic stem cells have been used to repair damaged heart tissue in mice, and have been trained into certain types of neurons that might be used to recoup damage after a brain injury like a stroke,” Mariani says. “The results are very interesting and exciting.”

Many embryonic stem cells are taken from embryos discarded from fertility treatments. Strict political limitations on embryonic stem cell use have pushed researchers to investigate alternative sources for this renewable material.

For example, embryonic stem cells have been extracted from the amniotic fluid, as well as the umbilical cord.

“With in-vitro fertilization it is also possible to create an embryo and remove only a couple of embryonic stem cells. The embryo recovers and develops perfectly normally,” she says. “These are ways around the ethical issues.”

Stem cells also exist within adult cells, in bone marrow for example, albeit with limited potency. Researchers are also exploring ways to convert adult stem cells into embryonic ones. Only last year, in fact, a research team from Wisconsin and Japan was able to transform human skin cells into those that have properties similar to embryonic stem cells.

“But we really haven’t gotten to the point where we can efficiently and safely create embryonic stem cells from adult cells,” she says.

The Potential

There’s little doubt that stem cell research has great potential for indescribable breakthroughs in medicine. And though researchers have come light years in unlocking the biology of these miniscule medical marvels, there is still much to understand.

“We are still trying to grasp the basic science of stem cells,” Mariani says. “How do these cells know to become one cell type rather than another? How do they know to self-renew?”

Mariani says that using stem cells in therapeutics may be many years away.

“But the exciting thing right now is that people are willing to try a lot of innovative and creative experiments… When you have the spirit of innovation, people have the courage to try new things.

“Who knows what will come of it? But I’m sure we’ll have many wonderful discoveries,” she says.