Bush’s bioethicist on stem cell alternatives

MSNBC: Some scientists have said it's difficult to know whether an embryo is dead or alive.

Kass: It’s true. And part of what they want to do is do the kind of natural history study which then might issue in the discovery of certain kinds of cell markers that say “this is now dead for all practical purposes, and it’s not going to continue to divide.” If we see these markers, then the ballgame is over for this embryo as an organism. But individual cells might still be viable.

It’s a new concept. Nobody has thought about organismic death for a little unfolding bag of cells, but we now know that it’s not just a bag of cells, that the embryo’s cell division is coordinated, that there is polarity even in the fertilized egg. Even though it looks to the naked eye as a symmetrical sphere, the place where the sperm penetrated now defines a certain pole in that embryo. These little organisms are wholes and dividing as a whole at a very early stage, and until people start to look to see whether there aren’t criteria for organismic death, I think scientists are being irresponsible when they say we simply can’t find out or don’t know when death occurs.

It’s a challenge, but it’s a scientific challenge, and skepticism about what science can show is usually not the proclivity of scientists. They usually are willing to say, well, let’s see what can be done.

The next alternative is to use a biopsy, that is, cell removal from still-living embryos, presumably in ways that will not do damage to that embryo. We now practice, at least on a small scale, what’s called preimplantation genetic diagnosis, where couples are at risk of a child with a genetic disease known to run in the family. At the roughly eight-cell stage, one or even two cells are taken out for genetic testing. And maybe 10,000 babies have already been born, more or less healthy, following this procedure. ... If you take out a couple of cells and you test them, and the embryo is shown not to carry the genetic disease of concern, that embryo is then transferred to a woman, and if all goes well, nine months later you’ve got a baby free of the disease. The thought is that maybe you biopsy these embryos, and you take out the individual cells, not for genetic testing, but to try to produce stem cell lines from them.

No one has yet converted a single blastomere from an eight-cell embryo into a stem cell line. That’s a scientific challenge. But the council was quite concerned about the ethics of this. We didn’t think that one could justify putting a child-to-be at additional risk, not for its own benefit. Until it could be proved by animal studies, or by much longer studies of preimplantation genetic diagnosis, that embryo biopsy is really risk-free to the child who results from all of this, the council is unprepared to pronounce this particular approach as ethically acceptable at this time.

MSNBC: Some feel that if you extract a cell at the blastomere stage, and somehow are able to have it proliferate, and apply this to stem cell research, then that would answer the ethical concern.

Kass: Yeah, that’s possibly the case. But the demands of the clinical decision with the genetic testing for PGD don’t really permit the kind of long-term cultivation of cells. In other words, the couples in there want to know. … It’s got to be very quickly timed. They need an answer within a day to know whether this embryo is transferable or not. And I don’t think those clinical decisions of seeking pregnancy will allow us the leisure to grow out cells in sufficient number to then harvest some for testing and keep the rest for stem cell lines.

The idea, by the way, that you could turn this into benefit for the very child much later in his life, when at the age of 50 or 60 he needs to have heart muscle cells — look, we’ve got cord blood to do that right now, and by that time answers to questions of immune rejection are much more likely to be available. I don’t think you can justify this in terms of the very benefit to the child from whom you’re taking these cells. It’s yet to be demonstrated that you can go from these single cells to pure stem cell lines. The timing of growing out enough cells to get around the ethical objection of added risk, I think, makes this logistically not a practical prospect. But if people want to try this in animals and show me I’m mistaken about this, I’m willing to look at the data.

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