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Quick study
Don Sakaguchi and Harvard colleagues take first step in using cell
replacements for human eye diseases
Don Sakaguchi has known Harvard scientist Michael Young for a number of
years. At a professional meeting last December, the two decided it was time
to work together.
Less than a year later they have positive results.
"For my lab to start out on this project would have taken much longer,"
Sakaguchi said. "We're interested in how the brain develops, but we
didn't have the expertise to transplant mice stem cells."
From the collaboration has come research which found that transplanted mice
stem cells successfully become integrated into the eyes of Brazilian opossums.
Both Sakaguchi and Young see this as a positive sign for future treatment
of human eye diseases. The research was presented at the society of Neuroscience's
annual meeting in New Orleans in early November.
"The research is a promising step for using cell replacements to treat
diseases of the human eye like glaucoma, macular degeneration and diabetic
retinopathy," said Sakaguchi, a developmental neurobiologist and associate
professor of zoology and genetics.
"The work also may have implications for treating brain disorders such
as Parkinson's and Alzheimer's as well as injuries to the brain or spinal
cord." The transplanted cells were neural stem cells from mice. Stem
cells are cells that the body has not yet assigned a specific identity.
Biochemical and genetic signals cause stem cells to differentiate into liver
cells, skin cells, nerve cells or other cell types.
Young and his colleagues engineered the mice stem cells so that they produced
a fluorescent protein. Once the cells were transplanted into Brazilian opossums,
the researchers could determine their fate by tracking the green-glowing
protein.
The mice stem cells were transplanted into the eyes of opossums ranging
from 10 days old to two years old. Eye tissue from the animals was examined
after one to 12 weeks. The researchers found the transplanted cells differentiated
into nerve cells and glial cells, cell types that are normally found in
the eye.
In general, the researchers found that the younger the opossum, the greater
the chance for stem cells to integrate and differentiate.
"Experiments by other scientists have had limited success in integrating
neural stem cells into adult animals," Sakaguchi said. "Our results
suggest stem cells stand a better chance if they can be transplanted into
an embryo-like environment."
That kind of environment is what the Brazilian opossum provides. The opossum's
pea-sized newborns are very immature.
"With the newborn opossum, we essentially have access to an embryonic
stage of brain development," Sakaguchi said. "This makes the opossum
a good model to study cellular connections in the brain as they become established."
The next step of the research will be to identify the conditions in this
embryo-like environment that enhance the survival and differentiation of
stem cells. With this information, researchers can try to mimic the conditions
so stem cells stand a better chance for use in adult animals. In the future,
the researchers would like to transplant stem cells into animals with eye
or other brain disorders to see whether the cells help treat the disease.
--Brian Meyer Agriculture Communications
--Additional information by Dave Gieseke
Around LAS
December 4-31, 2000
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