Stem cell treatments are already being tested in people. Much of that work is in its early stages, focusing on the safety of the procedures -- safety always comes first in testing a new treatment. But there have been promising signs in some of these initial trials.
Here's where the research stands in 11 key areas:
Understanding Stem Cells
Find out what stem cells do, what's happening in stem cell research, and what it may mean for you.
Goal: Use stem cells to repair heart tissue damaged in a heart attack.
Does it work? This research is in its early stages and focuses on safety more than effectiveness.
Early success: Some patients in clinical trials have shown improvement. One early trial reported improvement in heart function in patients who got stem cell infusions based on their own heart stem cells. And in another trial, heart attack scars began to heal after patients got injections of stem cells taken from their own bone marrow.
Grow New Blood Vessels:
Goal: Angiogenesis -- the growth of new blood vessels.
Does it work? Stem cells from sources including bone marrow, umbilical cord blood, and fat tissue have been shown to stimulate the growth of new blood vessels called capillaries. Theoretically, this may help treat heart disease and heart attack damage, and help avoid the need to amputate limbs deprived of blood flow. In early trials with endothelial stem cells (which make cells that line the inner surface of blood vessels), this approach was safe, but there hasn't been clear evidence of patient benefit. Another approach is to use adult stem cells from bone marrow; a Cleveland company called Athersys is testing that. Those tests are still preliminary.
Early success: Four-year-old Angela Irizarry of Bridgeport, Conn., was born with a life-threatening heart defect that made it hard for her heart to pump blood to the body. Yale University surgeons used Angela's bone marrow stem cells to grow a new blood vessel to bypass the defective part of her heart. It's still an experimental procedure, but Angela has done well so far. Her parents hope to enroll her in school this fall, according to a Yale spokeswoman.
Goal: Use limbal stem cells (taken from the outer border of the patient's cornea) to improve vision for people with corneal disease, the No. 2 cause of blindness.
Does it work: A British study concluded that transplanting limbal stem cells "is a safe and effective method of reconstructing the corneal surface and restoring useful vision in patients."
Goal: Use human embryonic stem cells to make specialized cells to help treat Stargardt's macular dystrophy and dry macular degeneration.
Does it work: Testing is under way but is still in the early stages. The U.S. biotech company Advanced Cell Technology is conducting the trials.
Early success: Results have been reported for two patients, the first in each clinical trial for Stargardt's macular dystrophy and dry macular degeneration. Both patients had no side effects. Both had "measurable improvements in their vision that persisted for more than four months," the nonprofit Alliance for Regenerative Medicine states in its Annual Industry Report 2012. But larger studies are needed to check the procedure's effectiveness.