Islet Cell Transplant: Still Promising?
This experimental pancreas procedure might eliminate the need for insulin injections in some people with diabetes. But it isn't easy, so other islet-cell alternatives are being researched.
Islet-cell Transplants continued...
"The process of harvesting the pancreas, isolating the
cells, and then transplanting them all in one day is pretty tough, especially
when you also take into account the situation that you might actually spend
that entire day trying to isolate cells and never come up with enough cells
from that procedure," says Emmanuel Opara, PhD, associate research
professor in the department of experimental surgery and assistant research
professor in the department of cell biology at Duke University Medical Center
in Durham, North Carolina.
Opara and colleagues are looking at alternatives to human islet
cells, including the use of islets taken from pig pancreases. Although the use
of animal organs in humans is controversial, insulin derived from pig and cow
pancreases has been in use since the early 1920s, when commercial insulin
production began; the use of human insulin is a relatively recent
Pig islet cells are very similar in nature and function to
human islets, but because they come from an animal they are seen as foreign
invaders by the patient's immune system, which sends out specialized cells to
hunt them down, tag them for removal, and kill them.
To get around this problem, Opara and colleagues at Duke have
developed special drug-delivery spheres made up of a complex carbohydrate
called alginate. The spheres surround, or "encapsulate" the islet
cells, and are reported to be porous enough to let blood sugar come in and
insulin go out while protecting the islet cells from immune-system act. The
spheres are a little like the arrow slits used by archers defending ancient
The Duke researchers are also investigating methods for
freezing harvested islet cells. "One of the things I've been doing is to
design procedures that will enable us to store these cells in a very viable
state, so that when you require them you will approximate the situation of
going to a doctor to get a prescription [for islet cells] and then going to the
pharmacy to pick them up," Opara tells WebMD.
In addition to building islet-cell reserves, the technique has
the beneficial side effect of making the cells less offensive to the immune
system, thereby helping them to survive longer when transplanted into a patient
with type 1 diabetes, Opara says.
Islet Sheets, Viruses, and Stem Cells
Other research teams are working on sheets of islet cells that
are surrounded by a porous plastic; the resulting sheets could theoretically
act as bio-artificial pancreases. Still others are experimenting with viruses
that could make beta-islet cell transplants more acceptable to the immune
system, in a form of biological "stealth" technology.
And as reported by
WebMD in 2001, researchers at the National Institutes of Health are working
to develop a new method for restoring insulin production by coaxing embryonic
stem cells into becoming beta-islet cells specialized type of insulin-producing
cell. If the technique works in humans, it could represent a major breakthrough
in the treatment of diabetes and could even replace injected insulin, report
researchers in the April 26 issue of the journal Science.