TOPICS > Science

Peter Mombaerts and the Cloning Debate

May 1, 2002 at 12:00 AM EDT


SUSAN DENTZER: As you said, this is a concept at this point. No mouse has ever been cured, certainly no human has ever been cured, but that’s the objective, right? Why else are we engaged in all of this research?

PETER MOMBAERTS: The last few years have witnessed a real explosion in research on stem cells, not only adult stem cells, but also embryonic stem cells, and it has become pretty clear that sooner or later — I don’t want to put a year on it — this will become clinically useful. Now with nuclear transplant technology, which developed entirely independently of the stem cell research, the merger of these two technologies allows us to make customized stem – embryonic stem cells. You’re obviously no longer an embryo, so it’s impossible to make embryonic stem cells from you. But thanks to nuclear transfer, one can make these really magical cells, embryonic stem cells that can differentiate into any cell type you wish.

It’s a concept still. Bits and pieces of it have been done, including in human. We are the farthest advanced in mouse, although no mouse — no diabetic mouse, no mouse with Parkinson’s symptoms has ever been cured. And there is no other species in which this type of research is being done.



SUSAN DENTZER: One of the key points here with respect to doing this — we obviously have lots of research going on about embryonic stem cells — but the reason to do this through the process of therapeutic cloning, to create those cells in the first place is this whole belief that it’s going to be important going forward to have genetically identical tissue, or something close to genetically identical tissue.

How important do we think that is really going to be, and since we do have some at least growing evidence that perhaps the tissue isn’t exactly genetically identical, is that going to make a difference in the long run?

PETER MOMBAERTS: A lot can be done with the embryonic stem cell lines that are available, and the human stem cells lines, and the famous 60 that are now available for federal funding. However, they are derived from embryos that have a totally different genetic makeup of the prospective patient.

If President Bush would ever develop a disease and these differentiated cells coming from the stem cell lines would be implanted, he would simply reject those cells, or any other person. It’s the same old problem of rejection of foreign cells, of foreign organs by the immune system. That’s a problem we have been struggling with in medicine for 50 years already, ever since the first kidney grafts were done.

So, to some extent, I feel like this whole problem is going to surface again. These foreign cells would be rejected, that is absolutely certain. There is a way around it, which is to immune-suppress the patient, to give him or her drugs either for a short time, or chronically forever, for his whole life, and suppress his immune response. That’s what is typically done when a patient gets a kidney from an unrelated person, or a heart.

However, that immune suppressive theory is quite nasty. I don’t have any other word to describe it. It’s not pleasant, it has a lot of side effects. After all, the immune system is good for something. It fights infections. So we should learn from the history of organ transplantation and try to be more clever and go to the next step, which is to make customized cells that are identical to the genetic makeup of the patient.

We won’t be able to do this for a very long time probably, create a heart that has the identical genetic makeup as the patient. That is probably too much wishful thinking. But we will be able to do this with cells. Cells make up tissues, tissues make up organs, so we can make customized cells, maybe customized tissues, probably not customized organs for quite a while.

So we should learn from the history of 50 years of transplantation medicine, realize that immune suppressive therapy is with a lot of side effects, and try to do better.