Stem
Cells Rescue Retina
Bone
marrow saves eyesight.
Bone
marrow stem cells might one day deliver drugs to the eye, halting age-
and diabetes-related blindness. The cells can treat a genetic
condition that causes mouse retinas to degenerate.
When
the stem cells - that usually make blood vessels - were injected into
the fluid-filled space of the eye they became part of developing blood
vessels in the retina.
Faulty
capillary formation is central to both the leading causes of adult
blindness in the US: diabetic retinopathy and age-related macular
degeneration.
"It
just blew me away that we could use these cells as magic
bullets," says one of the research team Martin Friedlander,
ophthalmologist at the Scripps Research Institute in La Jolla,
California.
His
team worked on mice carrying a genetic mutation for retina
development. Normally, these animals start to lose retina blood
vessels around two weeks after birth and become completely blind by
one month. Bone marrow stem cells stabilized capillaries for up to a
month after the injection.
Whether
the mice can see, remains to be tested, but the retinas appear normal.
"What's
so interesting about these cells is that they go directly to where
they are needed, incorporate into the normal developing [blood
vessels] and just sort of join the party," says ophthalmologist
Lois Smith of Harvard Medical School in Cambridge, Massachusetts, who
studies blindness in premature babies.
Excess
capillaries can also cause blindness. So Friedlander's group next
exploited
the
cells' targeting ability to deliver a protein to the retina that
stopped blood
vessels
growing. Before being injected the cells were genetically modified to
produce
the
protein.
More
than a million people a year loose vision due to diabetic retinopathy
and macular degeneration. Friedlander hopes that "in the
not-too-distant future" doctors will be able to treat these
diseases using stem cells from patients' own bone marrow.
Before
then, much more work must be done in animal models to rule out
dangerous side-effects. "You would have to be very careful that
the modified cells don't get out into other areas of body and kill
blood vessels in the heart, brain, and limbs," cautions Karl
Csaky, who studies macular degeneration at the National Eye Institute
in Bethesda, Maryland.
Nonetheless,
Csaky feels the work holds great promise because the cells can replace
degenerating blood vessels in a system that biologists believed up to
now was irreplaceable. Nature
Medicine, Published online doi: 10.1038/nm744, (2002
