Neural stem cell drug delivery is encapsulating
By Katrtina Megget
05/11/2007 - Inherited genetic disorders could be treated with a new
stem cell-based drug delivery therapy through the use of
microcapsules.
Researchers at Carnegie Mellon University have created genetically
engineered adult neural stem cells which can be delivered to the
brain to produce and supply missing proteins.
"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,
developer and Carnegie Mellon biomedical engineering assistant
professor Stefan Zappe said.
Zappe, who is working in conjunction with Dr Raymond Sekula, a
neurosurgeon at Allegheny General Hospital, said he selected adult
neural stem cells because they could be harvested from the patient's
brain, had the potential to be multiplied outside the body, could be
genetically engineered, could disperse within the brain once re-
implanted, and could replace all major cell types of the brain.
The one problem facing the researchers was that re-implanted stem
cells produced an inflammatory response and would cause the stem
cells to differentiate into mature cell types which would not be
clinically effective as the cells would not disperse.
To address the problem, the researchers have developed cell-
instructive microcapsules that contain the genetically engineered
neural stem cells. These protect the stem cells from premature
differentiation.
The caviar-sized microcapsules also control whether the stem cells
proliferate, whether they differentiate into more specialised cells
types and the extent of migration.
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 thereby freeing the stem
cells which then migrate into the surrounding brain tissue where they
are programmed to produce the missing protein.
The idea behind the technology being developed is to give clinicians
the ability to genetically engineer neural cells from the patient, 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 the drugs that are given to the patient in
pill form," Zappe said.
The team is currently looking at Hunter syndrome, where patients lack
the enzyme iduronate-2-
certain waste products. One in every 130,000 boys is born with the
rare but deadly genetic disorder.
"Hunter syndrome is a devastating illness. 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-sulfatase to the central nervous system of these children, we may
change the course of this disease," Sekula said.
"Our technology and methodology also will likely have far-reaching
implications for hundreds of other diseases of the central nervous
system."
Analysts have estimated the gene therapy market will reach more than
$5bn by 2011.
http://www.in-
mellon-university-
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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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