Senescent Cells and Living Longer

March 07, 2016

To Live Long, Senescent Cells Gotta Go 

 Reference: Nature Feb 2016

 Your cells in your body are constantly dividing, up to a limit. Once they reach that limit, they stop. They are now “senescent”.   They have gotten old. Instead of doing their job, they are in the way and stop performing. Worse, they pump out all sorts of inflammatory compounds.   And that plays a role in your aging.  

  Hayflick described this limit some 40 years ago and it has been challenged, but continues to make sense as we come to understand how we age. As those cells get “senescent”, they build up a protein, p16, that tells them to commit Hari-Kari, or apoptosis.   P16 has been most studied in cancers where it appears to limit the ability of the cancer to multiply.   

Turning it off is useful. Turning it off slows down aging. Which means getting rid of those cells might slow aging. This is a useful line of attack for cancer, where cells don’t know to age and live way too long. And it is a useful concept to attack when we consider human aging. 

 Here is what this paper shows.   The researchers, Jan van Deursen, of the Mayo Clinic, and her team, added a snip of DNA to mice to manufacture a suicide protein when p16 shows up.   When p16 gets made, so does the suicide protein. But the protein only works when it has another chemical cofactor that is not naturally present in mice.   Then they waited until the mice were 60 years old in human terms; one year old in mice terms.   At that point they started injecting the partner chemical every 3 days.   That would make senescent cells that had started manufacturing p16 turn on the suicide gene. That would make the senescent cells die and be gotten rid of.   No inflammation, no damage to surrounding tissue.   The mice lived about 25% longer than the normal mice.   

In human terms, that would be adding 20 years of life to your life span. This sounds like a major leap forward in the anti-aging realm. But there is a very long way to go.   This is just showing us that we have a mechanism that can be manipulated in mammals to prolong life.   There are many barriers.   Inserting a gene into your DNA isn’t so easily done, quite yet. The technology is galloping ahead though, so it may not be long. 

 And, there are other problems. Senescent cells are required for wound healing.  They make PDGF-AA, which is a wound healing accelerant.   You can’t just turn off one function of cells. Somehow, in the mystery of how we all fit together, we have found useful features in senescent cells. That may explain why they have been allowed to hang around. The benefit is that you fix a cut, or a wound. The downside is you die, just a bit later.   

Well, then, if you need surgery or get a wound, stop injecting the partner chemical and presto, you go back to healing again. Is this ready for prime time? Humans? Not by a long shot. But at the speed at which medical research is racing ahead, it sure makes for interesting reading. But remember, you can already add 14 years to your life with a very simple strategy. 

The Harvard Professional Men’s study showed that getting your BMI to 25, exercising every day, not smoking, eating more vegetables and less sugar and flour and red meat, and a glass of wine a day and you add 14 years to your life. Start with that. By the time you’ve used that up, p16 and friends might be ready. 

 WWW. What will work for me.   I’m curious. I want to understand this stuff. I think my life time may see this advance.   But if I’m hanging around much longer than I want, hmmm.   I want control of when I exit too.   

 Pop Quiz

  1. Mice can live 25% longer if they can be programmed to clear out their senescent cells.   T or F                                 Answer:  That’s it in a nutshell.
  1. Senescent cells spew out inflammation, damaging tissue around them. T or F                Answer:  Again, right on
  1. You need senescent cells to help wound healing. T or F                Answer:  That’s their benefit.
  1. This technology might be ready for humans in a year or two. T or F                     Answer:  Whew, not likely. But this line of research may provide a path forward. We need more discoveries added on first.
  1. Time to buy your long term care policy quick? T or F                   Anwer:  Whoa Nellie. Not so fast. We have dozens of ethical and cellular engineering issues to work out before we get there.