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Peter Mombaerts on the Difficulty of Using Human Eggs

May 1, 2002 at 12:00 AM EDT


SUSAN DENTZER: Why is there such a big problem with the shortage of donor eggs?

PETER MOMBAERTS: The human eggs are very hard to combine. Typically, young, healthy women have to be recruited as volunteers. They will be treated with hormones — the same hormones, by the way, as the mice are treated with — and the super-ovulated woman then gives approximately 15 eggs instead of one. And those are collected by a needle that’s transvaginally introduced in the belly, and the eggs are thereby collected.

So it’s a very cumbersome procedure which has some risks for the volunteer. The whole procedure ends up costing approximately $1,000-$2,000 per egg, which is an immense number.

Now, we have to realize that nuclear transfer technology is a very inefficient procedure. It’s always been inefficient from the beginning. It’s the same level of inefficiency in different species, curiously enough.

SUSAN DENTZER: And when you say inefficient here, what you mean is?

PETER MOMBAERTS: The overall number that comes up over and over again is about one in 100 attempts to manipulate. An egg will give rise to a normal organism, to an organism that’s born. In the case of some cell lines, the data are not so good, but you probably need approximately 50 eggs, something in that order to make one embryonic stem cell line. For mice and cows and sheep, goats, we can get basically an unlimited number of eggs. We get 200 eggs from six mice, for instance, which cost $5 each and can be purchased.

So that’s never been an obstacle really. That’s never been a problem, the availability of material. In the case of humans, this is the key problem. The entire paper of then cell technology, I think about 70 eggs were used. This cost, you can make the calculation, 70, $140,000 just to get the eggs. Haven’t really done anything with them yet.

So, of course, the progress will be slower in humans. It will be slower in humans for anyone in this type of research because for ethical, medical and logistical reasons it is very difficult to get 200 eggs per day, because that’s what you would really need. …

Even if it’s allowed legally, it would still be difficult logistically. Women are not lining up in large numbers to donate their eggs. They probably shouldn’t. We have to be smart and think, “Can we do this in an egg-free way, or a human egg-free way?” And there are some rumors that Chinese scientists have been able to use rabbit eggs, for instance, and make human embryonic stem cell lines using the rabbit eggs as a recipient for the human nuclei.

So that would be one solution is to avoid the use of human eggs. And for those people who are used to the cloning technology and read those papers critically, the key difference is the poorly available material in the case of humans, and those people doing human nuclear transfer research are unethical. They don’t set up large organizations where– maybe in developing countries where people donate eggs for a small price. We realize that that is going to be a problem, financially, medically, ethically, and logistically.

Again, not surprisingly, therefore, that research on therapeutic cloning in human has been closed, and is slowed, and will be slow compared to other species like the mouse.