The Spectacular Now: The Marvel of Stem Cells
Reprogramming Cellular Potential
The term “stem cell” refers to several types of cells that have the ability to divide and create identical copies of themselves and to develop into specialized tissues, such as skin, kidneys, or hair. The objective is to use them to treat various human diseases in which cells are damaged, dysfunctional, or diseased.
One type, the human embryonic-derived stem cell, exists only in the earliest days of an embryo’s development and can become any of the more than 200 different cell types in the human body. These cells are called pluripotent cells, because they can develop into so many various tissue types. Adult stem cells are undifferentiated cells found in people of all ages and in most of the body’s tissues, including the heart, skin, and intestine. They multiply by cell division to replenish dying cells and repair damaged tissues, and they self-renew indefinitely. These stem cells are destined to become cells from their tissue of origin, but they can grow into a variety of cells related to that tissue. Adult stem cells found in bone marrow, for example, can become red or white blood cells or platelets. Both types of stem cells are already in clinical trials.
Even more progressive, researchers have discovered a new source of stem cells, induced pluripotent stem (iPS) cells. These begin as any type of mature body cell and are genetically reprogrammed in the lab to return to an embryo-like state. They are then coaxed to become any of the different cell types in the body. In 2012, Shinya Yamanaka, MD of Kyoto University in Japan, and Sir John Gurdon of the Gurdon Institute in Cambridge, England, won the Nobel Prize for discovering iPS cells. The FDA has not yet approved the use of iPS cells in humans, although iPS therapies are preparing to enter non-human clinical trials. Research published in the journal Nature in January revealed a surprising new way to create pluripotent stem cells: exposing mature cells to environmental stress rather than cancer-causing factors. Hoping to identify a safer approach to reverting the cells back into an early, undifferentiated state, scientists found that soaking mature cells from mice in a mild acid solution for 30 minutes changed them into stem cells. More research is needed to learn why this occurs and to see if these stem cells behave as other stem-cell types do.
Public attitudes about stem cells for therapeutic use appear to be shifting. In the late 1990s, some groups expressed concern about the use of embryonic stem cells—taken from unused embryos donated by parents after they underwent in vitro fertilization—based on ethical, moral, or religious views. But that debate has largely subsided, researchers say, in part due to new technologies, including iPS cells. “The ability to reprogram cells to give us pluripotent cells from sources other than embryos has relieved the cloud of ethical concern that many people had, and that’s a net positive,” says David Scadden, MD, director of the Massachusetts General Hospital Center for Regenerative Medicine and co-director of the Harvard Stem Cell Institute.
Public support for stem-cell research has also grown with the hope that these therapies might someday treat or even cure devastating diseases, such as amyotrophic lateral sclerosis (ALS, or Lou Gehrig’s disease). “If you actually talk to people who have a relative or friend with a life-threatening or serious disease, they are very willing to accept stem-cell therapies if they are done in an ethically appropriate way,” explains Ellen Feigal, MD, senior vice president for research and development at the California Institute for Regenerative Medicine (CIRM). This agency was founded in 2004 after California voters approved Proposition 71, an initiative that devoted $3 billion over 10 years to stem-cell research. CIRM is currently the largest source of stem cell research funding in the world.