Carnegie Mellon Biomedical Engineering Researcher Works
To Develop New Drug Delivery System by Using Adult Neural Stem Cells
PITTSBURGH — Carnegie Mellon University's Stefan F. Zappe is using
adult neural stem cells to develop a new stem cell-based drug
delivery therapy that may ultimately help treat a variety of
inherited genetic disorders like Hunter syndrome.
Zappe, an assistant professor of biomedical engineering at Carnegie
Mellon, and his graduate student Sasha Bakhru, are creating
genetically engineered adult neural stem cells for delivery to
patients' brains, where they will be programmed to produce an
essential missing protein. In Hunter syndrome, for example, patients
are lacking the enzyme iduronate-2-
down certain waste products. One in every 130,000 boys is born with
the rare but deadly genetic disorder.
Zappe, who is working with Dr. Raymond Sekula, a neurosurgeon at
Allegheny General Hospital, said he selected adult neural stem cells
for his work because they can be harvested from a patient's brain,
have the potential to be multiplied outside of the body, can be
genetically engineered, can disperse within the brain once re-
implanted and can replace all major cell types of the brain.
To support their therapeutic goals, Zappe and his team have developed
cell-instructive microcapsules that contain neural stem cells. These
microcapsules efficiently control whether stem cells proliferate
(multiply), differentiate into more specialized cell types like
neurons and to what extent implanted stem cells will be allowed to
migrate to the host tissue.
Zappe will be using these caviar-sized capsules specifically for
rapid manipulation of stem cells outside the body and for reliable
delivery of stem cells to the brain. The acute inflammatory response
that usually occurs from implantation would normally cause implanted
neural stem cells to differentiate into mature cell types that are
not able to migrate extensively. Encapsulated stem cells will be
protected from such premature differentiation.
Once the brain has healed from the initial implant of the
encapsulated stem cells, the stem cells are genetically engineered to
produce an enzyme that eats the microcapsule, freeing the neural stem
cells. The stem cells can then migrate deep into the surrounding
brain tissue where they provide the missing enzyme.
"We are particularly interested in targeting the brain because this
area of the body is protected by the so-called blood-brain barrier
that has been very difficult to penetrate with therapeutic enzymes
that are usually injected into the patient's bloodstream,
Zappe and Sekula are working to develop technologies that will
ultimately enable clinicians to harvest neural stem cells from a
patient, genetically engineer them from outside the body and then re-
implant them and remotely control their actions in non-invasive ways.
"By using inducible gene expression, we hope to provide physicians
with external control over capsule degradation and the amount of
therapeutic enzyme released into the brain by engineered cells as
determined by the dose of drugs that are given to the patient in pill
form," Zappe said.
"Hunter syndrome is a devastating illness affecting more than 500
children in the U.S. alone. Over time, toxic waste products
accumulate in the cells of the body, and, although progression of the
disease varies, the majority of children die in their teens. If we
can reliably provide the missing enzyme iduronate-2-
central nervous system of these children, we may change the course of
this disease. Our technology and methodology also will likely have
far-reaching implications for hundreds of other diseases of the
central nervous system," Sekula said.
http://www.cmu.
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StemCells subscribers may also be interested in these sites:
Children's Neurobiological Solutions
http://www.CNSfoundation.org/
Cord Blood Registry
http://www.CordBlood.com/at.cgi?a=150123
The CNS Healing Group
http://groups.yahoo.com/group/CNS_Healing
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