For the first time, scientists have grown stem cells using human embryos cloned from adults. The research, announced Thursday, expands the technical capabilities of cloning science, while prompting larger ethical concerns.
Scientists have created human clones in the lab before, but the latest research, published in the online edition of Cell Stem Cell, takes that feat further by using cloned embryos to produce stem cell lines. A similar experiment, announced 11 months ago, did the same thing, but involved DNA cloned from fetuses and infants, whereas the new research uses DNA from two adult men. In both cases, the cloning technique was similar to the one that produced Dolly, the famous cloned sheep, in 1996.
In the latest experiment, Robert Lanza and his colleagues from Advanced Cell Technology in Massachusetts extracted complete sets of nuclear DNA from adult skin cells and implanted them in egg cells (whose nuclei had been removed) donated by four women. They shocked the resulting, quasi-fertilized eggs, causing them to begin dividing and growing into blastocysts, early-stage embryos just a few days old.
Cloning is an especially touchy process, with a low success rate. Out of 77 eggs Lanza and his team used, only two grew to become normal, late stage blastocysts. Genetically, these tiny embryos were almost completely identical to the two adult men, ages 35 and 75, whose skin cells had been used to grow them.
After creating the clones, the researchers extracted their cells to create a reproducible stem cell line, a process that destroys the embryos. Since the resulting stem cells genetically match the male donors, in theory they would be ideal cells for treating diseases in those individuals. The researchers say their goal is cloning for medical purposes, and claim they have no interest in reproductive cloning.
However, embryonic stem cells, such as those created by the latest experiment, are controversial and morally problematic because they involve the destruction of living embryos. They’ve also been eclipsed by newer types of stem cells that don’t involve embryos. Induced pluripotent stem cells, or iPS cells, can be created using only cells from adults, and scientists generally consider them the most promising route to advanced stem cell therapies. Like cloned cells, iPS cells are genetically matched to a patient, eliminating the problem of a patient’s body rejecting the stem cell treatment.
Lanza admits that stem cell scientists are more interested in using iPS cells than cloned ones, but says cloning offers “another way to skin the cat,” according to Time. “The hope is that iPS cells work out, but for the future application of stem cell therapies to treating disease, it’s good knowing there is another way to make stem cells should we need to,” Lanza said.
The United States still has no federal ban on reproductive cloning, although some states have preemptively outlawed the practice.