Therapeutic Cloning

May 24, 2013

Imagine, for a moment, that you have been diagnosed with early Alzheimer’s disease, and the only cure for your condition involves using one of your cells and a human egg to make an embryo, which is a clone—or genetic copy—of yourself. From that embryo—or blastocyst, technically—stem cells are removed, thereby destroying the embryo, but providing a source for the neural tissue to treat you. Would you do it?

This scenario came a step closer to reality last week with the announcement from Oregon Health and Science University that for the first time, a human embryonic clone had been created and developed sufficiently for human stem cells to be removed. The technique, called human therapeutic cloning, requires the transfer of the nucleus from a body cell to a human egg whose nucleus has been removed. Then, an electric current prompts the egg to begin dividing. It becomes, in essence, an embryonic clone of the body cell’s donor. Stem cells are then taken from the inner cell mass of this embryo after only four to six days of development, before any body parts have begun to form. Stem cells can then be converted into most of the various types of cells within the body. Because cloned stem cells have the same genetics as the person from whom the embryo was made, the new cells can be transplanted back to the donor without the problems of tissue rejection.

The potential benefits of stem cell therapies are truly exciting—including possible treatments for Alzheimer’s and Parkinson’s disease, diabetes, and spinal cord injuries. But ethical issues loom as well. First, extracting stem cells from an embryo destroys it. Researchers don’t believe the embryo created by cloning is viable for achieving pregnancy, but the technology still thrusts us directly into the religious and philosophical questions of the moral status of the human embryo and our obligations toward it.

Then comes the question of the sources for the human eggs needed. Egg procurement is not free of risk or harm, and countless eggs could be needed. Finally, some critics of therapeutic cloning also worry that success now will lead to cloning for reproductive purposes in the future.

So then we must ask whether there are any ethically better alternatives to therapeutic cloning. Unfortunately, each possibility comes with ethical tradeoffs as well. One option is to take a different kind of stem cell from adults, rather than from embryos. But these so-called adult stem cells are already somewhat specialized and thus not as therapeutically useful. A second option would be to use some of the more than 400,000 surplus embryos currently stored in fertility clinics. As these embryos were originally created for reproduction but are now leftover and destined for destruction, they are thought to be ethically preferable to those created merely for research. But these other sources of embryos bring not only the problem of embryo destruction, they also couldn’t produce tissue genetically compatible with the patient who needs it.

Perhaps the most promising alternative comes from a recently developed technique in which adult cells are reprogrammed to behave like embryonic stem cells, without needing embryos as a source. These are called induced pluripotent stem cells. Like therapeutic cloning, this technique would produce genetically compatible cells. But it remains an open question whether this technology will ultimately be successful.

So what are we to do? Prioritizing research to maximize the potential of adult stem cells and induced pluripotent cells makes sense because no embryos are involved. But should we ban all embryonic stem cell research in the meantime? What if the more preferable options don’t pan out?

As the abortion debate has demonstrated, we’re not likely to get a strong consensus on the ethics of any action that involves embryos. Most Americans, however, do occupy what we might call an ethical “troubled middle” in relation to the moral status of an embryo, believing that even the pre-embryo has some moral standing or value, but not that of an adult. Roughly 75 to 80 percent of Americans support some form of embryonic stem cell research. In this case, society must face the ethical question fairly: When do we achieve an ethical tipping point at which the potential benefits of therapeutic cloning outweigh its ethical problems? I don’t think we’re there yet, but it’s the conversation we must have.

In the meantime, one place to start would be to enact wider bans on human reproductive cloning, to avoid the ethical slippery slope. Indeed, several states have already done this. We could also continue the ban on human cloning of all kinds in federally funded research. And as ongoing research clarifies the options, we could then decide whether therapeutic cloning should be banned or best left to private conscience. Which brings us back to the question, would you create a pre-embryonic clone of yourself to cure yourself of a dreadful condition?