Senescent Cells and the Hayflick Limit

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Senescent cells are old, dying zombie cells that are leak toxins into surrounding tissues, infecting them and turning them senescent in turn. They’re bad news They poison us from the inside out, and trigger autoimmune disease. So lots of people in the anti-aging community are trying to clean them out of their bodies.

But there’s also an argument for proceeding with caution, because they do play other roles in the body. One argument for keeping them is that they can’t get cancerous. This is their supposed “survival advantage.”

I see this point, but another way to look at it is: “Of course they can’t.. They’re half dead and toxic, a poisoned and decrepit soil that even cancer cells can’t grow in. Living with them in our bodies is like living into a house next door to a toxic waste dump which is poisoning our soil and water supply, then saying it’s good to have the dump there because burglars are afraid to come into the neighborhood. I’d rather take my chances with the burglars (or cancer).”

Another argument is that we shouldn’t get rid of senescent cells because when our body makes new cells to replace them, this moves us closer to the Hayflick Limit (the maximum times a cell can divide, as determined in lab studies using cell cultures). The warning here is that this could leave us one cell division closer to the maximum number, so might actually be moving us closer to the end of our lives.

This is an interesting argument, but also strikes me as ridiculous. The Hayflick Limit isn’t locked in stone. It’s an approximate number, a needle that can be moved at least a bit in either direction by outside intervention (such as stressing the cells or depriving them of nutrients). And the truth is that Zombie (senescent) cells can’t reproduce at all. They’re already at the end of their effective lifespan. We’re not losing anything of value when we lose them, particularly if we do so by doing a five day fast or fasting mimicking diet.

This is because at the end of a fast or FMD when we start eating again, our bodies replace the senescent cells that were cannibalized to survive the fast with new STEM cells, essentially resetting the process to the beginning. The notion that the cells they then differentiate into are bound by the same ticking clock as body cells which have been around for decades that I would question. I’m not saying they’re not, but that we should not necessarily assume that they are. We’re adding young cells, freshly created from stem cells, to an aging body; this is unlikely to set us back or result in our dying sooner.

The infusion of stem cells at the end of an FMD is in many ways a major system reboot. Till there’s more research, we shouldn’t assume that it’s just making us healthier. For all we know at this point, it could be leaving us with a larger number of total divisions remaining before we kick the bucket. There’s certainly no reason to assume it’s leaving us with fewer.

A third argument is that senescent cells may have important functions in the body. They appear to play a role in wound healing. But if we compare wound healing as it occurs in a child with healing as it occurs in an eighty year old, the immune system is clearly functioning better in the child, who has almost no senescent cells, than in a much older person.

Give me a kid’s immune system, instead of an old guy’s immune system that’s limping along trying to use whatever battered resources it can find to repair injuries and fight off intruding bacteria and viruses.

Image by Arek Socha from Pixabay 

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