Two publications (Science and Cell) published papers today showing that scientists have succeeded in reprogramming human adult cells to behave much like human embryonic stem cells (hESCs). Following on findings published several months using mouse rather than human cells, the researchers responsible for today's results were able to spur the reprogramming by inserting four genes into the adult cells.
The big question is whether this new technique will quell the stem cell research controversy, which arises largely from the fact that the stem cells scientists believe have the greatest medical potential are today derived from 5-day old embryos. The answer is "maybe." Scientists interviewed in today's New York Times article were ebullient about the results, but it is worth remembering that there have been two major scientific discoveries in the last 18 months that promised to end the debate and then quickly faded from public view. In the summer of 2006, scientist Robert Lanza showed that it was possible to produce hESC lines without destroying embryos by carefully removing single cells from many 8-cell embryos. Although long term effects are unknown, we know that removing a single cell from an embryo at that stage does not prevent it from developing. This technique is routinely used to obtain genetic material for preimplantation genetic testing, and the embryos (less one cell) are successfully used for implantation by in vitro fertility clinics. In January of this year, scientists from Harvard and Wake Forest Universities reported that they had discovered stem cells in amniotic fluid that possessed many traits of hESCs.
I am optimistic about today's discovery, but three questions remained to be answered, two scientific and one philosophical.
The scientific questions: First, will further research show that these reprogrammed cells actually have all the features of hESCs that make the latter so promising? This means they not only must be able to create all the body's cell types, but they must be able to proliferate as rapidly and maintain their unspecialized characteristics in culture as well as hESCs do. Second, will the reprogrammed cells create cancers or other gentic abnormalities? The work done using mouse cells earlier this year suggests the answer is probably yes at the moment, although improvements in the technique might solve this problem. If this problem cannot be overcome, reprogrammed cells might be just as useful as hESCs for some research purposes but not suitable as the basis for stem cell preparations that could be used as treatments for patients.
The philosophical question: Will opponents of embryo research embrace the concept of reprogramming cells to their embryonic state? The technology suggests it might one day be possible to use a cell reprogrammed in this way to create an entire person, in the same way that an implanted embryo can develop into a person. Given this possibility, will people who believe embryos have the same moral value as persons and thus should not be used for experimentation believe that reprogrammed cells also have the same moral value as persons and thus also should not be used for experimentation? There is a substantial difference between an embryo and and embryonic stem cell, but not everyone who favors the protection of embryos thinks this difference is dispositive of the question. When Robert Lanza demonstrated the possibility of using single cells from a 8-cell embryos to create cell lines, some opponents of embryo research (including Senator Sam Brownback) protested on the ground that the single cell in question deserved protection. More discussion of the Lanza technique and the response to it can be found in Stem Cell Century: Law and Policy for a Breakthrough Technology).