November 30, 2022

Were the sound and fury of the hybrid embryo debate pointless?

Therapeutic cloning’s star wanes

A few months ago, in the teeth of ferocious
opposition, the British parliament passed a law authorising the
creation of human-animal hybrid embryos. The idea was to create clones
using hollowed-out animal eggs and human genetic material. Now MPs may
feel that they wasted their time in an ethical Battle of the Somme: the
debate was pointless because the "cybrids" almost certainly will not
work.

Earlier this month, Robert Lanza of
Advanced Cell Technology, a California stem-cell company, published a
paper in the journal Cloning and Stem Cells, which showed that
human–cow, human–mouse and human–rabbit hybrid embryos fail to grow
beyond 16 cells. "there is no evidence that patient-specific human stem
cells can be generated using animal oocytes," his team concluded. Genes
thought to be critical for pluripotency — the ability to develop into a
wide variety of cell types – also failed to express properly. "At first
we thought it would just be a matter of tweaking the culture
conditions," Lanza told Nature. But "the problem was far more
fundamental".

Critics of the hybrids felt vindicated. A
British scientist commented on Nature’s blog recalled that "Those who
questioned the ethics or the prospects of this technology had to face
angry patients who had been convinced that cybrids would be the holy
grail that would cure them." He contended that "high profile public
hyping of very speculative proposals, like cybrids, is a disservice to
the public and to science".

But it was a bitter disappointment for
scientists who had hoped that they could get pluripotent stem cells
without having to use human eggs, which have proved all but impossible
to obtain ethically in the vast quantities required for serious
research. The unpalatable conclusion seems to be that the supernova of
"therapeutic cloning" is fading. ~ AFP, Feb 2; Nature, Feb 3; Cloning and Stem Cells