|
The controversy over stem cells has been complicated by its
entanglement with the controversy over cloning. This confusion engendered by
this entanglement calls for clarification. The two controversies come together
on the issue of immune rejection. If we were to coax hES
cells to become differentiated neural cells, and if we were to implant those
cells into a patient, that patient’s immune system would likely put up a
blockade and fight off an invasion of what, genetically speaking, are foreign
cells. This problem of immune rejection, or ‘histocompatibility,’
represents a significant technical hurdle that scientists will need to clear if
the promise of hES cell transplantation is to be
realized. (Our experience with organ transplants demonstrates how serious a
problem histocompatibility can be.) If, however, the
stem cells could be made with the exact genetic code of the recipient, then the
transplant-recipient’s body would welcome the new cells as its own. The
technology of cloning appears to offer the possibility to achieve just such a
genetic match.
The process looks like this. The laboratory researcher
would begin with a woman’s egg, an oocyte, and remove
the DNA nucleus. Then using the technique of somatic cell nuclear transfer
(SCNT) developed in the Dolly experiments, a DNA nucleus taken from a skin cell
or some other somatic cell in the future
recipient’s body would be rendered quiescent and then transferred to this
enucleated oocyte. The egg would then possess a full
complement of DNA, the very DNA of the future recipient. The egg would be
activated, and at five days or so the stem cells would be harvested. They would
be teased into becoming heart tissue or liver tissue or whatever is needed.
They would be placed into the patient’s body. The stem cells would then
regenerate whatever organ welcomes them home. This technique is called
“therapeutic cloning” and promises perhaps the best way to overcome the problem
of immune rejection. It is generally distinguished from “reproductive” cloning,
which would be the use of somatic cell nuclear transfer to generate a child.
The addition of therapeutic cloning to stem cell research,
however, advances another set of ethical issues. Not only must the ethics of
stem cells deal with the problem of destruction of a blastocyst, but it
must also deal with the deliberate creation in the laboratory of a new
“embryo” that is slated for destruction. Some people believe that the
deliberate creation of an embryo with intent to destroy it is an even more
serious ethical issue than the destruction of embryos that were already “slated
for death” because they would not be implanted during the IVF process.
We turn now to the three moral frameworks that have
structured - and, in our view limited - the public debate over stem cells.
Email
link | Printer-friendly | Feedback
| Contributed by: Gaymon Bennett, Karen Lebacqz and
Ted Peters
|
