Imperfections mar hopes for “ethical” reprogrammed stem cells
When scientists announced five years ago they could reprogram ordinary skin cells into behaving like embryonic stem cells, religious conservatives and others who opposed the use of stem cells cheered the advance. But while they have proven to be a powerful new way to study human disease, the reprogrammed cells — known as induced pluripotent stem cells, or iPS cells — are no substitute for embryonic stem cells.
“This has strong policy implications,” Dr. George Daley of the Harvard Stem Cell Institute and Harvard Medical School said in a telephone interview. “It has not ever been a scientifically driven argument that iPS cells are a worthy and complete substitute for embryonic stem cells. Those arguments were always made based on political and religious opposition to embryonic stem cells.”
Stem cells are the body’s master cells, the source material for all other cells. Proponents of embryonic stem cells say they could transform medicine, providing treatments for blindness, juvenile diabetes or severe injuries. Scientists typically harvest embryonic stem cells from leftover embryos at fertility clinics. But the issue has been a point of controversy for some religious conservatives, for example the Roman Catholic Church, who believe the destruction of any human embryo is wrong.
When they were first discovered in 2006, induced pluripotent stem cells looked like a perfect solution to this ethical debate. Instead of destroying an embryo, iPS cells are made in a lab from ordinary skin or blood cells. Using various methods, scientists introduce three or four genes that return these cells to an embryonic-like state in which they, too, are able to turn into any type of cell.
But recently, scientists have started to raise concerns about iPS cells. Last year, a group led by Dr. Robert Lanza, chief scientific officer of Advanced Cell Technology, compared batches of iPS cells to embryonic stem cells and noticed the iPS cells died more quickly and were much less capable of growing and expanding.
“It was the first study showing there were problems. No one wanted to believe it,” Lanza said.