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:
Repair Damaged Heart Tissue:
- 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.
- Goal: Use stem cells to outwit type 1 diabetes.
- What's being done: Two different approaches are being explored. One is to use patients' own stem cells to make pancreatic cells, called beta cells, that can release insulin on demand for people with type 1 diabetes. If successful, the treatment could free patients from insulin injections.
- Does it work: In an early study, the experimental procedure using patients' own stem cells, plus drugs to suppress the immune system, helped 15 teens with type 1 diabetes stay off insulin injections for about 1.5 years, on average. There were some side effects, most of which were temporary, and the study's small size means the results are preliminary. Clinical trials of the treatment using human embryonic stem cells have not begun.
- Goal: Use stem cells to offset brain damage done by stroke.
- What's being done: A clinical trial is under way in Scotland. The trial, called "PISCES" (Pilot Investigation of Stem Cells in Stroke) involves 12 men who were disabled by stroke caused by a blood clot (the most common type of stroke). The researchers give the patients one brain injection of fetal neural stem cells 6-24 months after their stroke. The study is designed to test safety. If safe, the long-term goal is to repair tissue in the stroke-damaged areas of the brain and to reverse disabilities that can result from stroke (such as problems with movement, memory, attention, speech, language, or daily living). The U.K. company ReNeuron is doing this work.
- Does it work? So far, the procedure appears to be safe. As of June 2012, six patients had gotten the stem cell injections. The therapy caused "no cell-related adverse events" and "no deterioration in the health of any of the patients," according to a news release from ReNeuron, the company doing the work. Another study is slated to start in 2013.
Spinal Cord Injury
- Goal: Use stem cells to treat chronic spinal cord injury in patients with varying degrees of paralysis.
- What's being done: A preliminary trial is under way, using adult neural stem cells. That trial is being done at Switzerland's University of Zurich and will involve 12 patients who have thoracic (chest-level) spinal cord injury. The stem cells will be directly transplanted into the patients' spinal cords. They'll be followed for 12 months after the procedure. A California biotech company, Geron, was testing using human embryonic stem cells to restore spinal cord function in patients with recent spinal cord injuries. But Geron discontinued the study in November 2011 when it ended all of its stem cell programs to focus on cancer programs.
- Does it work? So far, there's no proof of lasting effect. In 2009, scientists at the University of Sao Paulo School of Medicine in Brazil published a study involving 39 patients with chronic spinal cord injury. They took stem cells from the patients' blood and delivered the cells back into the femoral artery in the patients' legs. The therapy was safe and 26 of the patients (66%) showed some improvement in responding to stimuli, the researchers reported in the journal Spinal Cord. But ultimately, the therapy hasn't yet shown much effectiveness, according to a stem cell trial review published in 2011 in BMC Medicine.
Two clinical trials of stem cell treatments are listed on the National Institutes of Health's clinical trials web site. One of those trials is in China, using stem cells from patients' own bone marrow. The other trial, listed as taking place in Mexico, uses stem cells from patients' fat. Both trials are very small (20 patients for the Chinese trial and 10 for the one in Mexico). It is far too early to know if either approach will work.
Stem cell research has been done in mice but not in people with Alzheimer's disease.
ALS (Lou Gehrig's Disease)
- Goal: Test that safety of delivering embryonic stem cells to the spinal cord.
- What's being done: This trial is being conducted at Emory University and is led by the University of Michigan's Eva Feldman, MD.
- Does it work? So far, three patients have gotten the stem cell procedure. No side effects were seen, so the FDA has approved them getting a second treatment, higher up in the spinal cord. This trial is not designed to see if the procedure improves their ALS -- just to see if it's safe.
- Goal: Use stem cells to suppress and then reset the immune system to work without MS.
- What's being done: Clinical trials involve suppressing a multiple sclerosis patient's immune system, then transplanting adult stem cells to rebuild the immune system -- without MS. The stem cells used are those that make blood and are typically found in the bone marrow or umbilical cord blood.
- Does it work? It's too soon to know. However, an Italian study shows some success. Researchers at Italy's University of Genoa studied 74 MS patients. First, their immune systems were suppressed. Then they got transplants of their own blood-forming (hematopoietic) stem cells. Two patients died from "transplant-related causes," the researchers report. After five years, 66% of patients had remained stable or improved. The study concluded that the therapy "has a sustained effect in suppressing disease progression in aggressive MS cases unresponsive to conventional therapies" and "can also cause a sustained clinical improvement," especially in people with the relapsing-remitting form of MS.
Caution: Because the immune system has to be suppressed before stem cell treatment, "the benefits need to substantially outweigh the risk," states a review of stem cell treatment trials published in BMC Medicine.
Stem cell clinical trials are also being done for other autoimmune diseases, including lupus, Crohn's disease, and rheumatoid arthritis, according to the review published in BMC Medicine. It's not yet clear how well those treatments work.
- Goal: Neural stem cells are being used in clinical trials that aim to destroy glioblastoma, a type of brain cancer, when surgery isn't an option.
- What's being done: The City of Hope, a medical center in California, is genetically modifying neural stem cells to make an enzyme that converts a nontoxic drug (5-Fluorocytosine or 5-FC) into an cancer drug (5-Fluorouracil or 5-FU). The researchers inject the modified neural stem cells into the patient's brain, hoping that the stem cells will travel to the tumor and latch onto it. Then the patients get 5-FC. When 5-FC reaches the tumor site, the attached stem cells help convert it to the cancer drug, 5-FU. The goal is to shrink or destroy the glioblastoma, while sparing the rest of the body from the toxic effects.
- Does it work? The trial, the first to test this treatment in people, is still under way, so it's too soon to know if it's safe and effective.
Leukemia and Other Blood Cancers and Disorders:
One of the original uses of stem cells (from bone marrow and umbilical cord blood) is to treat blood and immune disorders. Bone marrow or cord blood transplant has become standard treatment for some of these conditions.
The National Bone Marrow Donor Program web site has a list of diseases that can now be treated with hematopoietic (blood-forming) stem cells. These include various leukemias and lymphomas.
- Goal: Use stem cells to make new cartilage.
- What's being done: There haven't been many trials in people yet. Some researchers have reported using patients' own adult stem cells (typically taken from their bone marrow), embedding those stem cells into a gel or onto a collagen sheet, and placing it onto the area of cartilage damage (such as the knee or ankle).
- Does it work? There haven't been enough studies to tell. So far, the results are mixed because the tissue made by the stem cells seems to vary in its quality and durability, according to a 2011 review published in the Open Orthopaedics Journal.