The Immortality of the human soul is endlessly debatable until at least we find out what a soul is. The Immortality of the human body is a subject we can now talk about, thanks to the progress in biology. It is possible for us to live indefinitely long provided:
- We don’t get a rapid fatal injury of the body organs and systems.
- Our habitat doesn’t get destroyed with us in apocalypse.
What stops us from becoming immortal right now?
- We are programmed to senesce and die at certain age.
- We are susceptible to fatal infections.
- We are targetted by mutations and other genetic alterations causing disease and pre-mature death.
How can we fight these things?
- We need to crack the molecular program controlling our ageing.
- We need to clarify the molecular mechanisms of infections.
- We need to unravel the genetic and epigenetic basis of disease.
These three “needs” have been keeping biologists busy for the last half a century, since the discovery of DNA and its structure as a hereditary molecule. Things turned out more complex than we thought, they always do. It’s not just about DNA, but genes.
A gene encodes a certain final product, RNA or protein, and is physically a long double-stranded stretch of DNA monomers (called nucleotides) connected by phosphodiester bonds.
Our genome is as big as 20 000 genes encoding tens of thousands of proteins interacting with each other in a vast spatiotemporal network inside cells and in the extracellular milieu.
The work of each gene is controlled by chemical modifications of DNA, it consists of, and modifications of proteins associated with our DNA, which are executed by dedicated protein enzymes. Yes, our genome is not naked DNA but a dynamic structure called chromatin: DNA is covered with proteins called histones, which help to structure our genome and cram it into nuclear compartment of the cell. On top of histones, there are hundreds of other proteins, which associated with a gene’s DNA and help to regulate gene’s activity. These get chemically modified as well. And their modifiers get modified too in their own unique way, depending on the time, place, magnitude and other characteristics of the incoming signal. I actually simplify here.
So, twenty thousand genes, tens of thousands of proteins, hundreds of different cell types in our body. Complexity is enormous.
It is not surprising that several million scientists, including me, work in different areas of natural sciences.
Now, before you get bored, I have to assure you that we’ve made a lot of progress and discovered many mechanisms of ageing and dying. The scientific results led to improved treatments of hundreds infectious diseases.
Hey, what about ageing and life expectancy? – you may ask me. – Nothing’s really changed in the past 50 years. Science has been sleeping or what?
Science is as busy as it ever was. We discovered and characterized causes for many diseases on the molecular level, including ageing.
Here is one of them. We found that cells in our body are programmed to age because chromosomes, vessels for our genes, are capped with structures called telomeres. Shortening of the telomeres controls how many times each cell can divide, before it stops and dies eventually. There is a mechanism to sustain telomere length, which is active in stem cells and cancer cells. These cells can divide as many times as they want. They are immortal. So, part of us is immortal.
Stem cells – are the ones that can self-renew and also give rise to progenitors dividing into specialized cells in the organism, to replace the old or damaged ones. You may ask why we don’t just make stem cells to renew all our tissues indefinitely. This way we won’t age. That’s one of the goals of stem cell research. Using stem cells in tissue and organ repair and cosmetic purposes is already in progress. We are yet to find out why and how stem cells are programmed to allow for only a century but not a longer lifespan.
Another factor limiting our lifespan is cancer. There’s a theory that any cancer cell is in fact a stem cell gone wild. Mutations accumulate in cells, including the stem cells. In norm, stem cells only divide when instructed by specific internal or external signals. In case of cancer, cells divide ignoring any instructions to stop and turn into big tumors. Our immune system tries to kill misbehaving cells, but cancer cells can evade this by rapidly changing, dividing and accumulating more mutations. Ironically, our organism kills all the weak cancer cells and selects the toughest. We need to have a reliable method to track and eradicate malignant cells missed by our immunity.
So, all the longevity research focuses on these two main tasks: make stem cells to work forever and kill them if they turn into cancer.
But there are alternatives. They may be fictional at the moment, but they are plausible nonetheless. I’d like to hear about them from you. Do you have ideas of how to live forever?
What if the Earth is dying and the only way to stop it is to become immortal yourself. What would you try to do? What risks would you take?
In the future posts I will come back to the meaning of immortality and discuss whether we really need it.
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