Stems Cells and Brain Injury: Slow and Steady Progress

Stem cell research and brain injury started to take off in the late 1990s. Learn about progress being made in the field.

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.
Posted on BrainLine October 25, 2011.

Produced by Brian King, Ashley Gilleland, and Noel Gunther, BrainLine.