Researchers from Notre Dame's Keck Center for Transgene Research have been
investigating cellular transplantation as a possible cure for hemophilia, said Elliot
Rosen, associate director of the center.
The Center has been studying the genes involved in dissolving and forming blood
clots. In order to perform this research, the Center has used mice with genetic
modifications that affect this process.
"One of the main challenges we faced was that a lot of these animals died early
on [after their birth] so we couldn't study them," said Rosen.
A possible solution came in 1999, when Rosen attended a scientific meeting,
where he learned about an in-utero technique for transplanting blood cells.
By the summer of 2001, the concept of using in-utero transplantation techniques
to prolong the lives of the genetically modified mice had gained momentum.
Given the possible medical impact of this research today, the initial results of
this innovative research were featured in the inaugural run of the Journal of
Thrombosis and Homeostasis.
Rosen discussed the social dimensions of the research by expanding upon the
relationship between hemophilia in humans and the condition present in the
mice. Hemophilia is caused by a missing or defective protein known as factor VII
or IXI. The mice Rosen works with present a rare and deadly form of hemophilia
because of their lack of a protein necessary for proper blood coagulation
known as Factor X. Because of this, many of the mice exhibit massive
hemorrhaging upon birth and die shortly after.
The strategy Rosen and his team developed involves taking cells from healthy
mice embryos and transplanting them to the livers of sick mice.
"Currently, the donors have a gene that allows us to track the cells in the
recipients by adding X-gal to the cells, turning them blue," Rosen said.
If the cells from the donor embryos survive and colonize in the liver of the
recipient, they could make enough of the Factor X to allow the mice to survive.
Rosen explained several positive factors about the current research.
"Because the defective genes that cause hemophilia are known, it is possible to
detect the disease before the child is born by genetic screening of a fetus in
utero. Genetic screening would be focused on potential carriers eliminating the
need for an impractical general screening of all unborn children," said Rosen.
The strategy he and his researchers developed transplants cells in utero so that
the disease could be cured before it develops.
The second advantage of this strategy is related to current cures for
hemophilia.
"Currently, if a person manifests the disease, you can inject the missing protein
and manage the illness [and] sometimes 15 to 20 percent of the patient's immune
systems begin to recognize the protein as alien to the body and build antibodies
to inhibit the injected factors," said Rosen. "We are injecting the cells before
the immune system forms, thus our hypothesis, which we still have to prove, is
that the immune system will recognize these cells as `self' and will not develop
antibodies inhibiting the therapeutic proteins."
In order to use the strategy in humans, however, the team needs to increase
the efficiency of the procedure and find a more convenient source of donor
cells than isolating them from another embryo. Additionally, the team must
prove that the recipients do not reject the donor cells as alien, explained
Rosen.
At present, the research team has successfully increased the life expectancy of
50 percent of the mice in the experiments. The next series of experiments are
designed to test if the mice are developing the antibodies that would inhibit the
curative factors, said Rosen.
Scientists bypass major hurdle to hemophilia gene therapy
Scientists bypass major hurdle to hemophilia gene therapy; animal studies yield
high levels of clotting protein
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