I'm Dr. Deborah Shear, and I work at Walter Reed Army Institute of Research.
I'm a section chief there for the in vivo neuroprotection laboratories.
Stem cell research has been around for a while, and in terms of
stem cell research for the brain, I would say back in 1998-1999
it really started to take off with discoveries that Fred Gage's group
and a guy named Erickson made when they started going around the country.
They received permission from a number of human patients to look at their brains
and they discovered that endogenous neurogenesis occurs in the brain.
The thinking for many years had been--the dogma had been that we're born with
all the neurons we're ever going to have
and that we only lose them as time goes on.
You know how people joke when they go out drinking,
"Oh, I killed a billion neurons, but I'm still okay."
Well, there is some truth to that, and we do--our brains do go through a lot of pruning,
but there is also tremendous evidence that's surfaced over the last decade
showing that, indeed, there are new cells that are born in the brain
and that these new cells do generate not only glial cells, which are
the support cells of the brain, but new neurons,
and it's these new neurons, especially the ones that come from, say, the
dentate gyrus region of the hippocampus, the hippocampus being kind of the
learning and memory center of the brain,
that these neurons travel up into the cortex and that they make functional connections.
And so that started the whole focus of different areas of research,
looking at the possibility of either harnessing these--what we call
endogenous repair mechanisms in the brain--and learning how to use them
to promote functional recovery in disease and in injury.
And, also, it promoted the whole idea of cellular replacement therapy,
which has been very, very important in terms of Parkinson's research,
Alzheimer's research, spinal cord injury.
Now, in terms of traumatic brain injury, it's a far, far more complex venture,
doing stem cell transplantation in traumatic brain injury or looking at
replacing multiple cell types.
There is--you're not just trying to remyelinate damaged axons in a spinal cord
that are arranged in a liner fashion.
You're not just trying to replace cells that would innervate the dopaminergic system
in Parkinson's disease, but when you experience a traumatic brain injury,
especially a severe traumatic brain injury, you're losing
all types of cells.
When we started this research about a decade ago,
I think there was a tremendous amount of excitement in terms of
the thought that we might be able to rewire the brain to replace that lost circuitry.
As time went on, what we kept seeing from study after study,
from lab to lab, across different cell choices
ranging from mouse to rat to human, we would see functional recovery
in stem cell transplantation with traumatic brain injury
but that recovery would occur far too rapidly for it to be attributed to
any functional reconnectivity and, further, we haven't been able to demonstrate
that functional reconnectivity of--you know--of cellular replacement.
So it's--the field has kind of turned to looking at the real potential--the
real therapeutic potential with these cells as possibly this very elegant,
very exquisite cocktail, if you might say, of neuroprotective factors
and neurorestorative factors that are secreted by the cells, so they act
as little mini living pumps--little living mini pumps, per se, when you put them in the brain
and they put out these factors that will help protect against further cell death
and perhaps restore connectivity.