November 1, 2001
WASHINGTON, Oct 31, 2001 (United
Press International via COMTEX) -- Existing stem cell lines could accrue
genetic abnormalities over time and new stem cell lines will likely be
needed, experts told a Senate panel Wednesday.
"The current stem cell lines are
problematic because they accumulate mutations as they grow," said Dr. Bert
Vogelstein, chairman of a key stem cell research committee of the National
Research Council and Institute of Medicine. "Every time a cell divide in
a tissue culture it accumulates mutations. In aggregate those mutations
may cause certain problems."
Vogelstein and other medical experts
testified before a Senate appropriations subcommittee.
Stem cells are unspecialized cells
that can become any cell type with specialized functions. They can be gleaned
from several sources, such as placenta, umbilical cords and adult cells,
but scientists say those derived from human embryos are most useful for
therapeutic and research applications.
Stem cells, if implanted in a patient,
could grow cells afresh, offering cures for intractable diseases like Parkinson's
disease, Alzheimer's and diabetes.
On August 9 President Bush announced
that embryonic stem cell research should receive federal funding. But that
decision permits federal funding only on the some 60 existing stem cell
lines that have already been derived.
While stem cell providers the world
over are looking to the National Institutes of Health to fund stem cell
research on those existing lines, experts like Vogelstein warn of problems.
One issues is that many of the existing
lines were "cultured with animal cells and serum" creating the fear that
pathogens in mice or cows could be transmitted to humans if the stem cells
are used for therapeutic applications.
Another problem is that patient's
immune system may attack the newly introduced stem cells. One way of sidestepping
the problem is through a process known as somatic cell nuclear transfer
or SCNT. That procedure, also known as therapeutic cloning, involves taking
DNA from a cell belonging to a patient and inserting it into an egg whose
nucleus has been removed. When the cell divides, it produces stem cells
that can be put in the patient without causing an immune response.
But some lawmakers would like to
see so-called therapeutic cloning -- which, unlike reproductive cloning,
will never result in a birth -- outlawed.
A proposed measure by Sen. Sam Brownback,
R-Kan., would outlaw the act of therapeutically cloning a human embryo.
It would also ban the importation of products derived from therapeutic
cloning.
Vogelstein said such a ban could
mean that "regenerative medical applications will never occur and people
with terrible diseases won't be healed."
He also said that since much biomedical
research is international, "it's likely most useful lines and reagents
will be developed outside the U.S." Therefore, a ban on importation would
also curtail important research.
Another witness, James Thompson,
the cell biologist from the University of Wisconsin-Madison who discovered
stem cells, said despite the President's Aug. 9 decision, "the existing
human embryonic stem cell lines will not fulfill their promise unless the
National Institutes of Health begins to aggressively fund this area of
research."
Thompson point out that the NIH Human
Embryonic Stem Cell registry, which is necessary to initiation federal
funding, had not been completed.
Later in the hearing, Sen. Arlen
Specter, D-Pa., asked another witness, Wendy Baldwin, deputy director for
extramural research at the NIH, why the registry was still operating.
Baldwin said the project was behind
schedule due to the terrorist strikes but promised that it would be up
on the NIH website within a week.
Copyright 2001 by United Press International
United Press International