Stem cells promising for diabetes patients
By MeganP. Hall
Sept. 21, 2002 9:00 p.m.
Lauren Behlmer is one of 17 million people suffering from
diabetes in the United States. She injects herself with insulin and
checks her blood sugar up to four times per day, calling it a
“pain, but necessary” for her survival. Unless a cure
is found, Behlmer will depend on insulin until the day she
dies.
Though there have been a number of advances in treating
diabetes, one of the most promising ““ and a potential cure
for at least one type of the disease ““ comes from stem
cells.
Stem cells are precursor cells that have the potential to become
any number of differentiated cells, like blood, brain or bone. Stem
cells can be isolated from embryos or adult tissue, and both may
one day offer treatments for a number of afflictions.
In 1998, James Thompson from the University of Wisconsin,
Madison, figured out how to grow human embryonic stem cells in the
lab. The beauty of embryonic stem cells lies in their ability to
regenerate and to become any of the over 200 types of cells in the
human body, opening the door to potential treatments for disorders
like Parkinson’s Disease, cancer, spinal cord injuries,
osteoporosis and in Behlmer’s case, diabetes.
This breakthrough sparked a flurry of advances, but it is not
without controversy. Because ES cell isolation requires the
destruction of week-old embryos (usually “leftovers”
from in vitro fertilization clinics that are slated for destruction
anyway), President Bush restricted the use of federal funds for
research using human ES cells. Any ES cells established
according to certain ethical standards prior to the beginning of
his speech at 9 p.m. on Aug. 9, 2001, were fair game, but the use
of federal money was not to be used for the isolation of new cells,
nor for research on any but an existing 71 cell lines.
Fifty-one of those 71 cell lines reside in foreign countries
like Australia, Sweden, Korea, India and Israel. Only 16 have been
well-characterized and are available for distribution. As of
today, researchers in the United States have their hands on only
four.
Sen. Edward M. Kennedy, D-Mass., along with a number of
politicians, disagrees with the president’s restrictions,
saying that “failure to seize this unprecedented medical
opportunity would be a tragic betrayal of the hopes and dreams of
the millions of patients who expect us to do all we can to develop
these new cures.”
Critics of ES cell research argue that adult stem cells,
isolated from differentiated adult tissue and therefore not
requiring the destruction of embryos, can be used in place of ES
cells.
Until recently, it was thought that adult stem cells could only
differentiate into cells of the tissues they were isolated from, so
fat stem cells would only become fat cells. A number of
researchers found that adult stem cells could indeed become other
types of differentiated cells. For example, Dr. Marc Hedrick,
an associate professor of surgery and pediatrics, found that adult
fat stem cells could be persuaded to grow into bone, muscle and
cartilage.
But while adult stem cells are hailed by some as negating the
need for ES cell research, they are in most cases rare, difficult
to grow, and their ability to differentiate into the over 200 types
of cells in the human body has not been established.
Dr. Yi Sun, a researcher at UCLA working with both mouse
embryonic and neural stem cells, prefers ES cells because
“manipulation is 10 times easier than neural stem
cells.” She emphasized the need for research on basic cell
development in both embryonic and adult stem cells before
“getting too excited” about therapeutics that are
perhaps years down the road. Sun sees her research moving into
human ES cells in the future, and while the federal restrictions
inhibit that at the moment, she is optimistic about the
restrictions being lifted.
Most cells grown in the lab, including ES cells, will accumulate
mutations and change as they age. ES cells are also grown in
culture in the presence of factors from other species like mice and
cows, and researchers are wary of depending on the already-existing
cell lines in human trials for fear of transferring potentially
harmful factors across species. To use stem cells as therapeutics,
research on and derivation of new ES cell lines must be allowed,
under specific guidelines, with federal funding.
The National Academy of Sciences convened a panel of scientists,
ethicists and physicians in 2001 ““ none of whom work with
stem cells or have any conflicts of interest ““ to establish
guidelines for stem cell research. They concluded that
“studies of both embryonic and adult human stem cells will be
required to advance the scientific and therapeutic potential of
regenerative medicine,” and recommend public funding of ES
cell research and the formation of a “national advisory group
to oversee research on human embryonic stem cells.”
Dr. Douglas Melton, a researcher at Harvard whose son suffers
from diabetes, testified before the Senate that “it is now
foreseeable that human (embryonic) stem cells could be stimulated
to develop into pancreatic islet (insulin-producing) cells to
replace those that have been destroyed in individuals with Type I
diabetes.”
Patients like Lauren could potentially have her cake and eat it,
without having to self-inject insulin ““ but it will take the
full support of and careful regulation by the U.S. government.
