Using a specially designed
chamber, an international research team has transplanted islet cells into a
patient with type 1 diabetes.
The new technique avoided
having to use immune-suppressing medications, while still allowing the islet
cells to function and make insulin. In theory, the chamber "hid" the
transplanted islet cells from the patient's immune system, the researchers
Islet cells are normally
found in the human pancreas. One critical function of these cells is producing
insulin – a hormone crucial for metabolising the carbohydrates in food. In
people with type 1 diabetes, an autoimmune disease, the islet cells have been
destroyed by the body's own immune system.
"In order to
transplant replacement cells, heretofore, the immune response to the foreign
cells has had to be controlled with immuno-suppression," explained study
co-author Dr Norman Block.
Protecting foreign cells
Now, he said, senior study
author Dr Stefan Bornstein "has found a way to implant foreign cells and
protect them without using immuno-suppression" – drugs to dampen the
Medications used to
suppress the immune system can come with significant risks and side effects.
The study was released online
in the Proceedings of the National Academy of Sciences.
Because their bodies lack
working islet cells, people with type 1 diabetes no longer produce enough
insulin to survive. They must take daily insulin injections or receive their
insulin through a small catheter underneath the skin that's attached to an
Maintaining the proper
levels is a difficult task. Too much insulin, and blood sugar levels can drop
to dangerously low levels that at their worst can cause seizures and even
death. Too little insulin, and blood sugar levels run high. Over time, these
high levels can put someone with diabetes at risk of complications, such as
vision problems and kidney disease.
Needed levels of insulin
vary from person to person, and according to the types of food someone eats,
how much they eat, how much they exercise and what type of stress they face.
Because islet cells can
currently only be transplanted with the use of immune-suppressing drugs, the
implant procedure is limited to patients who have difficult-to-control diabetes
and experience repeated episodes of life-threatening low blood sugar levels.
Immune-suppressing drugs have potential side effects, including the risk of
infection and certain cancers.
To try to make the implant
procedure available to more people, the researchers designed a semi-permeable
chamber to house the islet cells, with the hope that the immune system wouldn't
be able to "see" the new foreign cells.
However, when islet cells
are first transplanted, they haven't established their own blood supply and
aren't able to get oxygen when they're hiding in the chamber. For that reason,
the current version of the device had an oxygen port on the outside of the body
attached via tubing that had to be refilled daily by the patient for as long as
a month or two, Block explained.
The device was implanted
into a 63-year-old man, who'd had type 1 diabetes for 54 years. He was of
average weight, and didn't have any serious complications from his diabetes.
Blood tests for a substance
called C-peptide showed he wasn't producing any of his own insulin. C-peptide
is a by-product of insulin production, and is often used to measure the success
of diabetes treatments in research settings. If C-peptide levels rise, it means
insulin production has risen.
The transplant recipient
had modest increases in his C-peptide levels, and the levels of C-peptide and
insulin rose rapidly in response to an injection of glucose (a form of sugar).
Over time, his long-term blood sugar control improved slightly, and his need
for insulin decreased, though not to the point where he didn't need insulin
Immune system unaware
What was remarkable,
however, was that after 10 months, there were no signs that the immune system
was aware of the new cells. There were no signs of possible rejection of the
new cells, and no signs that the immune system initiated an attack on the new
The transplant only
contained about half the amount of islet cells normally transplanted. "We
only had a limited number of beta cells available from this one pancreas,"
explained Block, a distinguished professor of urologic research and clinical
director of the Endocrine Polypeptide and Cancer Institute at the Veterans
Affairs Medical Centre Research Service, in Miami.
The limited availability of
islet cells for transplant has been another barrier to more widespread use of
islet cell transplantation. Block said that the device used in this study could
help with that problem as well.
"The reality of this
device, since the device protects the incorporated islet cells from immune
attack, is that it doesn't really matter if you use human or porcine (pig)
islets. Going to xeno-transplantation could be a future step that would enable
an unlimited number of islet cells that produce human-like insulin," he
Xeno-transplantation is any
procedure that transplants cells, tissues or organs from an animal into a
human, according to the U.S. Food and Drug Administration.
A diabetes expert not
connected with the study called the finding "exciting."
"They've clearly shown
the ability to maintain some function without immuno-suppression," said
Julia Greenstein, vice president for cure therapies at JDRF (formerly the
Juvenile Diabetes Research Foundation).
But, she added, "It's
a study of one patient, and the level of C-peptide wasn't enough to
significantly impact the clinical situation of the recipient. The goal of
transplantation is normal [blood sugar levels] or insulin independence."
Neither of those goals was met in this study."
"This study is one
early step on the way to developing a practical approach to providing islet
function for a person with type 1 diabetes," Greenstein said.
Learn more about islet cell
transplantation from the US
National Institute of Diabetes and Digestive and Kidney Diseases.
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