On April 6, the journal Cell published work (subscription or online article purchase required) from the Salk Institute in San Diego, in which scientists have created a new “reprogrammed” stem cell.
These cells are called “extended pluripotent stem cells” or “EPS” cells. They are different from embryonic stem (ES) cells, which are removed from intact embryos that arise from fertilization—typically requiring specific creation and destruction of an embryo. Of course, ES cells can be human or non-human, depending on the source.
EPS cells are similar to “induced pluripotent stem cells,” or iPSCs, invented in 2006. The latter are generated from adult skin cells that have been reprogrammed, using genetic alterations.
EPS cells may be made by reprogramming ES cells or skin cells or, if I understand the work correctly, iPSCs. In this case, the reprogramming is done with a cocktail of chemicals in the lab.
But EPS cells are more capable than iPSCs. Unlike iPSCs, which can give rise to many different types of cells but not all—including not a placenta and not an entire intact new individual—EPS cells can do all of that. They are totipotent, meaning they can make all the cells of an individual from their species. Moreover, they are quite long-lived in the laboratory. EPS cells from one species—e.g., humans—can be placed into non-human (e.g., mouse) embryos to make hybrid animals that, it appears, survive quite well and can breed. And, remarkably, the authors of the Cell paper report (again, if I understand correctly, and I think I do) that they were able to use a mouse EPS cell to give rise to a whole new mouse, not “just” a laboratory tissue hybrid.
Upside? A remarkable, easy source of totipotent cells that appear easy to derive, without requiring production or destruction of embryos, and use in the laboratory, enabling a wide range of research into embryonic development.
The downside? To read a report in my local paper, the San Diego Union-Tribune, apparently not much. That paper quotes a couple of stem cell experts, one also a Roman Catholic bioethicist, as saying that EPS cells really don’t pose much of a moral issue. The other quoted expert says that it would be a “misconstrual” to think this work poses an ethical problem “(i.e., creating whole ‘designer’ organisms from a single cell…).” These statements are printed a couple of columns after the statement, remarkably breezy in my view: “[The Salk scientists] have even created human EPS cells. But legal and ethical considerations have prevented them from trying to turn those cells into babies.”
It seems that EPS cells are another step toward eventual synthetic organisms. The Salk scientists successfully, and stably, made mouse-human hybrids by injecting a single human EPS cell into a mouse embryo. At a minimum, that work would seem to raise similar ethical issues as those raised by animal-human chimeras more broadly. Indeed, the senior scientist on the recent paper has been working on human-pig hybrids, with growth of human organs, in pigs, for transplantation in eventual view. “It will be very interesting,” his colleague said, “to test [EPS cells] in the pig.”
And, if mouse EPS cells can be used to give rise to (dare I say “make?”) a whole mouse, what in principle would prevent using human EPS cells to give rise to a baby? This prospect would seem to invoke ethical concerns substantially similar to those posed by human cloning. And, because EPS cells can also give rise to non-embryonic tissues, including placenta, needed for reproduction, then ex vivo gestation could be envisioned, although one certainly could not say that it “can’t be far behind.” There would be rather some distance yet to cover.
So, readers, please set me straight—if this development is indeed not troubling, then what am I missing? Where am I going wrong? Or am I raising concerns that “used to be considered germane,” but maybe are not anymore, because we’ve gotten used to the ideas involved…
The comments line is open.