July 1, 2022

Therapeutic cloning proof of principle

But inefficiency dogs scientists’ efforts

In an exciting development on the therapeutic cloning front, scientists at
New York’s Sloan-Kettering Institute have used cloned cells to cure disease for
the first time. It was only in mice, but the experiment is being described as a
"proof of principle" for therapeutic cloning. The scientists took skin cells
from the tails of mice, plucked out their nuclei, and inserted them into egg
cells from other mice whose own nuclei had been removed. Each line of stem cells
that resulted was genetically identical to the mouse whose skin cells were
initially removed. The researchers coaxed the stem cells to turn into neurons
that produce dopamine. Those neurons were then injected back into mice suffering
from a form of Parkinson’s disease. The mice were killed 11 weeks after

Despite the excitement, the experiment had some drawbacks. One was that it
was very inefficient. The researchers reported in Nature Medicine that they used
5,099 eggs to generate 187 different stem cell lines — an efficiency of barely
4%. It is inconceivable that this rate would be tolerated for human therapeutic
cloning. Besides, there may be a better alternative. Evan Snyder, a leading stem
cell researcher in California told Nature News that reprogramming, a new
technique developed by Japanese scientist Shinya Yamanaka last year, may make
therapeutic cloning effectively obsolete. "The subtext that everybody is reading
into this is, now that we have reprogramming, who cares?" says Snyder. However,
since the effectiveness of neither technique is unproven, he contends that
scientists should push ahead on both fronts. ~ Nature News, Mar 21