Brain cells can live longer than the body they were born in
On a cellular level, our bodies are basically modular systems. Individual cells can be worn out and replaced without necessarily disrupting the whole system, and those life spans vary according to the type of cell and the work it does. Cells in your stomach lining only hold up around five days before they need replacing, while red blood cells can remain functional for 120 days. The cells that make up the lens of your eye and the muscles in your heart seem to last your whole life (so take care of them!) The true survivors though, are your neurons. Studies in mice and rates have found that brain cells might be able to live twice as long as your entire lifespan, given the opportunity.
When do you get new neurons?
The brain cells of your cerebral cortex, where most of your complex cognition takes place, are formed before your born. As you experience and learn about the world, connections between these cells are trimmed and created, helping you organize and make use of memories you accrue in your life. It makes some sense then that you’d like these to be as durable as possible, allowing you to make sense and consciously interact with the world until you die. The main exception seems to be the cells of the hippocampus, which are associated with short- and long-term memory management, and can be created into adulthood. The rest of your gray matter is in for the long haul though, outlasting the original body that they grew up in.
Living longer in a rat’s brain
To test the durability of neurons, scientists raised mice from birth to adulthood, then took some of their brain cells and implanted them in developing rat fetuses. Those rats were then brought up with healthy lifestyles, right up until a day or two before they seemed ready to die of old age. The rats were then euthanized and dissected to see how the original mouse neurons fared in this surrogate brain. The neurons showed no signs of degeneration, happily carrying on despite outliving their original owner. While alive, the rats showed no signs of problems or enhancement, indicating that their brains were fairly hospitable to the neurological guest tissue.
So while much of our body needs regular rejuvenation, brain cells seem to be especially suited for their life-long tour of duty in our heads. What’s more, if we get better at caring for everything outside our skulls, it may be possible that our brains will be happy to keep up with the extended lifespan on their own.
My first grader asked: How long do the mice and rats live?
The lab mice generally lived around 18 months, as they’re not bred for longevity, which makes this kind of study on aging easier for scientists to manage. Rats usually live twice as long, meaning the mouse neurons at the end of this study were around four-and-a-half years old— 300% of their normal lifespan!
Source: Brain Cells Can Outlive the Body by Tia Ghose, Live Science
