But now, the scientists at Advanced Cell Technology are claiming that using animal eggs to make human cloned embryos doesn't work. From the story:
Researchers who tried to use mouse, cow and rabbit eggs to make human clones said on Monday the effort failed to produce workable embryos but added that they showed human cloning should work in principle. Mixing human and animal cells does not appear to program the egg properly, said Dr. Robert Lanza of Massachusetts-based Advanced Cell Technology.
But using human cells did reprogram the egg cell or oocyte and activate the genes needed to make a viable embryo, Lanza and colleagues reported in the journal Cloning and Stem Cells.
It isn't surprising that animal eggs don't work, since even ennucleated eggs (those that have had their nucleus removed) are more than mere empty shells. And it remains to be seen whether the intricacies of cloning will ever work reliably in humans.
What this does seem to mean, however, is that there is no immediate way around the egg dearth that is materially impeding the development of human cloning technology. With each cloning attempt requiring one human egg, tens of thousands of eggs will likely be needed just to perfect the technique--assuming it can be perfected. To ever use cloning as a treatment modality could take many times more. Thus, look for pressure to increase from "the scientists" for the creation of an egg market in which women would be paid to produce eggs for science--with potential devastating health consequences to the sellers.