With the first-ever human test of a medical treatment based on embryonic stem cells gaining federal approval, researchers are optimistic that President Obama will soon lift a controversial Bush-administration ban on federal funding for embryonic stem cell research and speed work developing treatments for diabetes, heart disease, cancer, Parkinson's, and Alzheimer's.

The Food and Drug Administration today approved human tests of stem cells to repair spinal cord injuries. The first test will involve eight to 10 people with spinal cord injuries below the neck and will start sometime this summer, according to Thomas Okarma, president and CEO of Geron Corp. of Menlo Park, Ca., which developed the stem cell treatment. Patients will be injected seven to 14 days after being injured.

Although this Phase 1 test is intended just to test the safety of the stem cell treatment, the researchers will be looking closely to see if the injected cells bridge the gap in a severed spinal cord, as stem cells have done in mouse studies. Embryonic stem cells have the ability to turn into any type of human tissue cell, which is why researchers are so excited about their potential. The Geron researchers also will assess whether the patients gain any return of sensation, bowel or bladder function, or movement in their legs. "That would be a very exciting finding," Okarma said. If this trial does well, the company expects to expand it to include patients with cervical spinal cord injuries, which are much more common and cause paralysis in all four limbs.

The FDA's approval of the trial three days after Obama took office was coincidental, according to the agency and Geron officials. "We have no evidence that there was any political shadow over this process," Okarma said today. Indeed, the embryonic cells used by Geron come from stem cell lines created before the 2001 Bush administration ban on federal funding for embryonic stem cell research. The ban came about because embryonic stem cells are derived from human embryos that were made for in vitro fertilization but never used. Today's go-ahead raises hopes that either the Obama administration or Congress will soon rescind the ban, which researchers say has hindered their ability to move quickly on developing potential cures.

Scientists are trying to use stem cells in three ways: 1) In the laboratory, to create an infinite variety of living human cells to better test the disease-fighting ability of new drugs in test tubes; 2) As patch kits, with cells injected to repair injured body parts, such as spinal cord or heart muscle cells; 3) To create transplants that could be used to replace body parts.

For instance, Geron is also trying to develop embryonic stem cell treatments for heart disease, in which the injected cells would be used to rebuild damaged heart muscle, and for type 1 diabetes, with the goal being to rebuild islet cells in the pancreas that were destroyed by the patient's immune system. The biotech firm is also investigating making cartilage to repair arthritic joints, bone cells to combat osteoporosis, and liver cells to treat liver failure. Other companies and researchers are pursuing treatments for sickle cell, cystic fibrosis, Parkinson's, Tay-Sachs, leukemia, and Alzheimer's.

"We're quietly excited," says Douglas Melton, codirector of the Harvard Stem Cell Institute. Melton and other scientists who are trying to harness embryonic stem cells' power to turn themselves into many different types of human tissue have had to separate that work from the rest of their laboratories, with stickers marking which equipment could be used for stem cell work and which for all other work. They also couldn't collaborate with other scientists whose work was paid for by grants from the National Institutes of Health, the primary source of funding for biomedical research in the United States.

Since then, scientists have had success in using other forms of stem cells. In 2007, Rudolph Jaenisch, a researcher at the Whitehead Institute in Cambridge, Mass., created induced pluripotent stem cells (IPS cells), which can be made from cells taken from an adult and appear to have the same regenerative power as embryonic stem cells. Last year, Jaenisch used IPS cells to treat sickle cell anemia and Parkinson's in rodents.

If IPS cells work in humans, they could eliminate one of the biggest problems with embryonic stem cell therapy: Patients need to take immune-suppressing drugs, so that their bodies won't reject and attack the cells as foreign. In the Geron trial, patients will take low-level immune-suppressing drugs for six months. Adult stem cells also have been used to grow organs, including bladders, of the same type of cells. That way, they don't need to differentiate into the right kind of cell, as embryonic cells do.