Do any cells last a lifetime?

13 March 2011

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Question

Hi Chris,

I had a question I was hoping you could help with.

I know that over the course of our lives we lose lots of cells that die and are replaced, but I wondered what cells are with us (if any) from birth until death? Presuming one lives to be 60 or so plus.

Thanks

Aron

Answer

Chris - There are lots of cells that you do replace on a minute-by-minute basis. There are other cells that you replace, never! In other words, they do have to last a lifetime. A good example of these are some of the brain cells. Although you can produce new brain cells during life, and that was a discovery made in the last 10 or 15 years, the vast majority of the brain cells that run your brain throughout your life, you have to make last a lifetime. One of the reasons why neurodegenerative diseases like Parkinson's and Alzheimer's disease are a problem is because once the nerve cells in certain parts of the brain die off, they're not replaced. So brain cells are a good example of a cell that lasts a lifetime.

Another one is some muscle cells. Let's take the heart as an example. Another reason why a heart attack is bad news is because when the heart is injured by a heart attack, there's an interruption of the blood flow to a territory of the heart so you will therefore lose muscle cells there, those cells in humans at least, and other high animals are not replaced. They are replaced instead by just fibrous tissue and scar tissue, so you lose physical muscle tissue, and this means the heart loses its ability to pump so well.

People used to think that fat cells were something that lasted a lifetime and that if you overfed the baby, the baby would make far too many fat cells when it was little, and this would be carried through the rest of its life and give it an increase risk of obesity. But in more recent years, there was a lady called Kirsty Spalding who's at the Karolinska Institute in Sweden, and she actually carbon dated fat cells, and found that they last about 12 years, and so, you make new ones on a roughly 12-year basis. So you make a fat cell, it will last an average of 12 years, then you can make more fat cells.

So the answer is, your body is a mixed bag. Some cells are made and they're killed off, and replaced very, very regularly, very, very rapidly, blood cells last 120 days for example, others do have to genuinely last you a lifetime.

Comments

do eye cells duplicate?

There are many different cell types in an eye. Some are post-mitotic, meaning that they are no longer dividing, like the rods and cones in the retina. Other cell types, on the other hand, like the epithelial cells that cover the cornea, are always constantly dividing (and can grow extremely fast when required to do so) to replace lost and damaged cells. 

Ideas are often born before the search for evidence finds said evidence.

With repect, let me add an alternative view.
Some cells contain important information and can not be allowed to die in an uncontrolled way. They have to be replaced in a tightly controlled way via a planned cell replacement program. Such cells indicate to its replacemen contoller that its life (for whatever reason), is nearing its end. A replacement cell is produced. When all parties are ready, the information held in the old cell it copied into the new cell. The old cell dies when instructed to do so. Programmed cell replacement is much more sensible than having some types of cells live very long lives. Cells that die due to injury die outside the programed replacement scheme and inportant information is lost. This explains the key purpose of sleep. Sleep is when the programmed cell replacement programme is running. Sleep well.

No, there's no evidence to support what you are saying.

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