Potential
Problem with Using Embryonic Stem Cells to Cure Diabetes?? As
reported by Joe Palca
All
Things Considered National Public Radio January 17, 2003
Scientists at Harvard
University have uncovered a potential problem with using embryonic stem cells
to treat diseases like diabetes. In theory, embryonic stem cells can turn into
any cell type in the body, including the cells that make insulin. Two years
ago, one team of scientists said that they'd succeeded in doing just that. But
new research suggests that the cells aren't really producing insulin after
all, and that means that they might not be useful for therapies
Joe
Rajagopal is a scientist at Harvard. He and his colleagues are trying to make
human embryonic stem cells turn into the kind of cells that make insulin. So
when another team reported two years ago they managed to do that with mouse
cells, Rajagopal called team leader Ron McKay and asked for details.
Dr.
Rajagopal and his team were actually very eager to repeat their protocols
because Dr. Mcay’s protocols were originally performed in mouse embryonic
stem cells, and they actually were very grateful for their collaboration in
attempting to do the same thing with human ES cells.
Rajagopal
and his colleagues tried to follow McKay's protocols to the letter. They took
ES cells, or embryonic stem cells, and coaxed them into differentiating,
changing into cells that produce insulin. The only difference was they used
human ES cells, not mouse. But there was a problem.There was plenty of evidence for insulin protein, but there wasn't as
much evidence for the actual production of insulin in the cells.
Rajagopal
says McKay's protocol called for growing the cells in a nutrient soup that
contained insulin, and he thinks the cells were sucking up that insulin rather
than producing their own. Rajagopal did the experiments again, this time using
mouse embryonic stem cells, just as McKay did. It didn't matter. The results
were the same. He and his colleagues reported their finding in the journal
Science.
Ron
McKay, who works at the National Institutes of Health in Bethesda, has seen
Rajagopal's paper, and states “My own view is that our work still stands and
that we have multiple lines of evidence that suggest that when we
differentiated the cells they produced insulin. And what the current paper
says is that you have to be careful about one of those pieces of evidence,
which I kind of agree with.
Besides, McKay says his is
not the only team that's been working with mouse embryonic stem cells to
pursue treatments for diabetes.More
than one group has now shown that you can take ES cells and differentiate them
in a way that's similar to the way we did and produce cells that will secrete
insulin. One of those groups is at Stanford University in Palo Alto.
Group
leader Seung Kim says not only have he and his colleagues successfully
repeated McKay's protocol, they've improved on it. What we found was by
changing conditions we could produce more than 10 to 30 percent of cells
producing insulin, we actually got over 95 percent.
Even
though there are several ways of doing it, Kim says it's tricky to prove that
the cells are really making insulin, not just storing it. In this sort of
thing, if you change something slightly, even unknowingly, you may wind up
with a completely different product than what was previously reported.
However
back at Harvard, Jay Rajagopal says it's possible that there were some slight
changes in the way he did the experiments that caused the results he observed.
But it's also possible that researchers may be overanxious to see positive
results from their studies. We just think that our finding is important in the
sense that it will prevent people from chasing red herrings and that is
important in a fast-moving field like embryonic stem cell research. In fact I
have just seen
something
else has just come online from a group in Germany; I knew that they were
working in this area, but this is the first time I've seen the data. So
really, since we talked, there's new evidence. Very exciting.
Exciting,
indeed. But it's also possible doubts will be cast on that study as well. It's
just the way science works.
This
information from Joe Palca, NPR News, Washington.
