The brain is going to be the hardest organ in the body to rejuvenate. But prevention of damage is more important than repair because loss of brain cells means loss of information. Replacement of brain cells won't give you back lost memories. One way we can prevent brain cell loss is to prevent blockages in small arteries in the brain.

A team of UC San Diego physicists and neuroscientists has discovered a bottleneck in the network of blood vessels in the brain that makes it vulnerable to strokes. The finding may explain the origin of the puzzling damage to the brain’s gray matter often detected in brain scans, especially among the elderly.

In the study, published this week in the journal Proceedings of the National Academy of Sciences, the researchers used a laser technique they developed to precisely monitor changes in blood flow resulting from an induced blockage in a tiny artery, or arteriole, in the brains of anesthetized rats. They found that the penetrating arterioles, which connect the blood vessels on the brain’s surface with deeper blood vessels, are a vulnerable link in the network.

“The blood vessels on the surface of the brain are like a collection of city streets that provide multiple paths to get somewhere,” explained David Kleinfeld, a professor of physics at UCSD, who led the team. “If one of the vessels is blocked, blood flow quickly rearranges itself. On the other hand, the penetrating arterioles are more like freeways. When blocked, the blood flow is stopped or slowed significantly in a large region round the clot.”

Many more people have had strokes than are aware of it. So lots of old people suffer from reduced cognitive ability and loss of memory due to silent strokes.

The obstruction of blood flow resulted in damage to the surrounding brain area, which the researchers report resembled damage seen in the brains of humans and thought to be the result of “silent strokes.” Silent strokes have attracted attention recently because magnetic resonance imaging has made it possible to follow changes in the brains of individuals as they age. MRI scans have revealed that, over time, small holes accumulate in the gray matter of many patients, including those who have no obvious behavioral signs of a stroke.

I do not want to get lots of holes in my brain gray matter as the years go by.

The researchers say their results support the hypothesis, made by clinicians, that the penetrating arterioles may be the location of small strokes that cause the death of sections of brain tissue in humans. The accumulation of damage may lead to memory loss, and may be a risk factor for having a larger stroke, according to Pat Lyden, a professor of neurosciences at UCSD’s School of Medicine and head of the UCSD Stroke Center.

Development of youthful artery stem cells that can replace aged stem cells could help repair brain arteries and by doing so avoid silent strokes that wipe out pockets of neurons in the brain. Genetic engineering of the liver to improve blood cholesterol could also reduce the risk of brain damage from stroke and poor circulation.

We need faster progress on stem cell research. The survival of our brain cells is at stake.