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Stem cell science offers new hope to diabetics
By Deena Beasley
LOS ANGELES, Oct 11 (Reuters) - Type 1 diabetes patients may be able to avoid
the need for daily insulin shots through transplants of insulin-producing
stem cells, but the procedure faces problems finding the cells and dealing
with immune-system rejection, researchers said on Friday.
"We have done 38 islet cell transplant procedures since 1999 -- 87 percent of
those patients are free of insulin therapy a year after transplantation,"
said Dr. Jonathan Lakey, of the University of Alberta in Edmonton.
Research from Edmonton and other islet stem cell transplantation centers is
being presented at a diabetes conference this week in Anaheim, California.
Diabetes, which can lead to heart and circulatory disease, kidney failure and
blindness, is caused by a shortage of insulin, a hormone that regulates blood
sugar levels, or by the body's failure to respond to it.
In Type 1 diabetes, the body's immune system attacks cells in the
insulin-making parts of the pancreas, called the islets of Langerhans. The
body is then unable to control blood sugar levels and insulin must be
Type 2 diabetes, which is more common, arises when the body becomes resistant
to insulin, often as a result of obesity.
Researchers have sought for decades to prove that islet cell transplantation
could be a cure for Type 1 diabetes, said Taylor Mayo, a spokesman for the
City of Hope Cancer Center in Duarte, California, one of 10 research centers
chosen by the U.S. National Institutes of Health to conduct studies aimed at
duplicating on a larger scale the islet cell transplantation done in Canada.
CELLS CULLED FROM DONATED ORGANS
The goal is to transplant stem cells into a patient's body where they can
produce their own insulin. Research so far has been with purified pancreatic
islet cells salvaged from donated organs, but experts acknowledge that there
are not enough.
"Spain is the No. 1 country in terms of organ donors, but even we would only
be able to cover 1 to 2 percent of the need," said Dr. Bernat Soria, of the
Universidad Miguel Hernandez in Alicante, Spain.
His group is working on ways to generate insulin-secreting cells from
embryonic stem cells and has succeeded in deriving, and successfully
transplanting into mice, cells from mouse embryonic stem cells.
In the United States, there are 5,000 to 6,000 donated pancreases available
each year, compared with 37,000 new cases of type 1 diabetes and the 1.5
million Americans already diagnosed with the disease, according to City of
Experts have been able to coax islet stem cells - precursors of
insulin-producing cells - to mature. Stem cells are the body's master cells,
and the embryonic versions are considered especially powerful.
Stem cell researchers can use adult stem cells found in the blood or other
tissue, but they are rare and difficult to work with; they can try to
transform normal adult cells; or they can use stem cells from embryos, which
have the potential to become any kind of cell in the body at all.
Some groups oppose using this last group of cells on ethical grounds, at
least from humans, and the debate is only partly settled in the United States
and some other countries.
"One of the critical problems is the islet shortage and the need to explore
new sources," said Dr. Craig Smith, associate professor of transplant surgery
at the University of California at Los Angeles School of Medicine and
associate director of the Southern California Islet Cell Resource Center.
Ultimately, an individual's own genes will likely be cloned, inserted into an
egg which is then allowed to develop as an early stage embryo, producing the
crucial stem cells, said Dr. Fouad Kandeel, director of the department of
diabetes and endocrinology at City of Hope.
This method would solve the problem, seen with any transplant of foreign
tissue, of immune system rejection.
There are drugs now available to suppress the immune systems of organ
transplant patients, but they are expensive and have side effects, Kandeel
"There are a multitude of ways to reprogram the immune system to accept a
transplant. But we have an existing treatment for this disease - insulin -
that is not toxic and not expensive and a new treatment cannot be more
daunting than the existing one," the City of Hope scientists explained.
"This dilemma is forcing scientists to think very hard about strategies for
immune tolerance without having to go to the big guns."
The multicenter trial of the islet cell transplants, sponsored by the NIH
Immune Tolerance Network, is currently underway, with enrollment expected to
complete this year.
"Our goal is to facilitate the efforts ... to provide human islets and figure
out the best way to generate functional islets," said Richard Knazek a
medical officer at the NIH National Center for Research Resources.
10/11/02 21:31 ET
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