billions in new stimulus money for it, researchers are almost giddy
with enthusiasm about progress in the field. They’re confident stem
cells will treat — maybe someday cure — heart disease, diabetes, spinal
cord injury and other disorders.
But the excitement is not generated by stem cells harvested from human embryos.
Instead, researchers are coming to believe they can
get results almost as good from adult stem cells taken from the
patient’s own bone marrow or belly fat, and even full-fledged adult
cells from muscle tissue or skin.
“Adult stem cells have more flexibility than we thought,” says Dr.
“The embryonic stem cell might not be the most valuable property in
actual therapy. When you’re treating a heart attack, you might do
better with an adult stem cell.”
Already at the
stem cells have been injected around a patient’s heart to help heal a
heart attack, and adult cells are being applied around injured spinal
cords in hopes of restoring movement.
Another new development exciting researchers is the “induced pluripotent adult stem cell.” Scientists at
took cells from the skin on a patient’s arm and genetically
reprogrammed them to be almost as flexible as embryonic stem cells —
without destroying an embryo. They hope to use them someday to build up
entire human organs, cell by cell.
“This is really exciting,” says Dr.
“If you need a liver transplant, you can make a liver out of cells from
your own body. The same with a heart. It might replace embryonic stem
cells in some ways.”
Some adult stem cell experiments could get
Using adult cells avoids the controversy of
destroying embryos. And, coming from the patient’s own body, they avoid
the risk of rejection.
The excitement doesn’t mean researchers are losing respect for the value of human embryonic stem cells.
“The embryotic stem cell is the prototype, the
ultimate stem cell,” Hare says. “It has the greatest capacity to become
any other type of tissue. It’s essential to work with both kinds of
stem cells.”
“Embryonic stem cells remain central to our plan,” says Dr.
But the process of approving new lines of embryonic
stem cells is complex, and is going slowly. The first new line created
since Obama’s ruling was approved only in December. Only 50 lines have
been approved so far, with 300 more still awaiting action. The NIH has
awarded
stem cells in treating blood disorders, cancer, diabetes and diseases
of the heart, kidney and nervous system.
One researcher who has received some of the new cell lines approved by the Obama administration is
He plans to use them first in test tubes, then in lab animals and
someday in humans to create blood cells, also to help fight leukemia.
But he says: “Most embryonic stem cell research is still very basic. My human tests could be years away.”
In January, the
biopharmaceutical firm, plans to inject the cells around the severed
spinal cords of 10 paralyzed human patients to see if they can repair
them. But the trial hasn’t reached the human stage. It was suspended in
October over safety concerns in pre-clinical testing in lab animals.
The company hopes to resume the trial later this year.
At
are using both human embryonic stem cells and adult stem cells in
studying how to repair the heart after a heart attack. The embryonic
stem cells are used in basic lab research in test tubes but not in
humans, says
Hare, McNiece and colleagues are conducting a
clinical trial using adult stem cells to treat 53 human heart attack
patients. They extracted adult “mesenchymal” stem cells from the
patients’ bone marrow, purified and multiplied them, then injected them
into veins in the patients’ arms and legs.
The stem cells migrated to the heart, drawn by
chemical signals put out by the heart’s damaged tissue. The stem cells
appeared to become heart cells, helping to repair the damaged organ. In
early results, the mended hearts pumped blood more strongly and had
fewer dangerous arrhythmias.
At
In a trial with lab rodents, embryonic stem cells
were harvested from a human donor, reprogrammed into pancreatic cells
and transplanted into the pancreas of a diabetic mouse — with some
success.
“We’ve shown we can reverse diabetes in rodents. We’ve had them off insulin for a month. In
In another trial, with human patients, adult
pancreatic islet-cell clusters containing insulin-producing beta cells
were harvested from a cadaver’s pancreas and injected into the
patients’ pancreas.
“We dramatically reduced insulin requirements and got better control of glucose levels,” Ricordi says.
At the
researchers are working not with stem cells, but with full-fledged
adult cells called Schwann Cells. They are extracting the cells from
muscles in the patient’s arms or legs, injecting them around the
injured spine and trying to induce them to turn into myelin, a sheath
that wraps around the spinal cord and protects it.
In an earlier trial, the method restored the ability of lab rats to walk, albeit imperfectly.
Given the advances in both embryonic and adult stem
cell research, researchers debate which will be more important in
fighting disease.
“If I had to bet which will be the most important in
the long run, it would be adult cells from the patient’s own body,”
Ricordi says.
Says Simmons: “There’s a whole array of diseases
that afflict humans. Some will be amenable to therapy with adult stem
cells. Other more complicated procedures will probably be based on
embryonic stem cells.
“You need different horses for different courses.”
———
(c) 2010, The Miami Herald.
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