WASHINGTON — The political controversy over restrictions on federal funding for embryonic stem cell research is unlikely to end with Tuesday's news that mature human cells can be made to acquire the powers of embryonic stem cells, because scientists say research on both types of cells is closely related and is needed to inspire and cross-check each other.
President Bush has twice vetoed legislation that would lift restrictions on federal funding for embryonic stem cell research, and Congress has not mustered the two-thirds majority in each chamber required to override presidential opposition.
The scientific breakthrough that makes mature cells act like embryonic cells will allow the Bush administration to approve funding for a promising new line of research, but backers of embryonic research said that the older approach was too far along to abandon.
"I must say, this is a very exciting breakthrough, and it shows great promise, but it's still in its very early stages," said Rep. Diana DeGette (D-Colo.), a leading supporter of loosening federal restrictions on human embryonic research. "People like me feel we have to encourage all forms of the research, because you never know where the cure is going to come from."
Amy Comstock Rick, chief executive of the Parkinson's Action Network, said research on embryonic stem cells was much more advanced. "Unless something has been shown to fail, it should not be taken off the table, and embryonic stem cell research has shown great promise," she said.
The two kinds of scientific research will probably move in tandem for some time.
"I think we will see parallel science until we get a sense of whether the new alternative really is an alternative," said medical ethicist Arthur Caplan of the University of Pennsylvania. "If it proves to be real, I think you will see a diminishment of interest in human embryonic research."
In theory, stem cells can be grown into any type of cell in the body, so they are seen as holding the key to a new era of regenerative medicine. Some scientists believe their use could eventually result in cures for Parkinson's disease and other intractable illnesses. Many have thought that cells taken from human embryos hold the greatest promise, but scientists have now shown that skin cells and fibroblasts can be manipulated to acquire the same kinds of transformative powers possessed by stem cells.
