Neuroplasticity: The Secret’s in the Stem Cell
Time was, we were taught that brain cells were irreplaceable. While we could grow new skin cells or lining cells for the gastrointestinal tract, brain cells were all created before birth. Then we learned that stroke victims regained function best when they were returned to activity quickly after the stroke -- and that gave us the first clue that the brain might be able to regenerate. Before, we let the stroke victim rest and get out of bed when and if they felt they were able. Many times, they were never able to walk again. Now stroke victims go to special rehabilitation centers where they are more-or-less forced to walk long before they think they can. We’ve learned that recovery from stroke is much more complete this way.
A stroke results from damaged brain tissue. Most often a clot blocks a major brain artery, and within minutes the brain tissue sustained by that artery begins to die. (Sometimes the damage results from bleeding; the symptoms are often similar, the medication quite different; the benefit from rapid return to activity the same.) Once that particular chunk of brain dies, that’s it. It’s not coming back. But the brain tissue just next to it can take over its function. We call this neuroplasticity, meaning that the adjacent tissue remodels itself to take over the function of the destroyed tissue. How is this possible?
Researchers have found that the brain contains stem cells. Stems cells have the ability to divide and form themselves into other, specialized cells. For example, at conception, the ovum can be considered a stem cell; it will divide and the daughters will differentiate themselves into kidney cells, skin cells, blood cells, brain cells, and all the other tissues of the body. The bone marrow of an adult contains stem cells, which have no other purpose than to divide and provide daughter cells that become red blood cells and all the different kinds of white blood cells. A careful search of the brain has, in recent years, uncovered stem cells that can, when encouraged, divide and change into neurons and glial cells.
Neurotrophins Enable the Birth of New Cells
While we have but recently discovered that the brain can grow new cells, we’ve known for some time that the synapses that connect cells form new connections and lose old ones all our lives. This is part of the process of learning, be it physical, mental, or emotional, and it occurs through the mediation of brain-tissue growth factors called neurotrophins (“trophin” from a Greek word meaning birth). These neurotrophins are produced as a result of brain activity and have a more important role in certain areas of the brain, including the frontal cortex and hippocampus.
One of the better known among the many different neurotrophins is brain derived neurotrophic factor (BDNF). It contributes not just to the synaptic reconnections, but also to neurogenesis, the growth of new cells. . BDNF helps us form our brain after birth and as we grow3. BDNF is critically important to the hippocampus. Perhaps it shouldn't be a surprise that levels of BDNF are low in people with Alzheimer’s
Summary: Your Wonderful Brain
Your brain is subject to damage through the normal slings and arrows of time. In most cases, it has the ability to repair itself if you take good care of it. This month we’ve look specifically at the brain’s ability to form new cells that will replace those that have been damaged. This is good news and a good reason not to give up and accept dimming memory and abilities as a part of life. When you exercise your mind and your body, you give your brain what it needs to form new cells and new synapses. Sure, and you’re not likely to be the exception to the general rule that we all return to dust, but you can make the best of what you are given. My wish for you is that you can be that sharp, snappy, respected elder, still loved and valued by your friends and family.
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