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This is rather a bunch of questions that I decided to post on Chemistry StackExchange since I thought the chemists would have the most knowledge about the chemical processes of life.

So recently I have came across stem cells and a lot of revolutionary medical products that can rebuild tissue and even organs.

And then I thought that can we use these products to transplant our organs and in a sense, rebuild our own body. I have even came across making a heart and lungs as well.

If so is there any thing that stands between having a longer life?

What else do we need to have in order to prolong and in a sense immortalize ourselves.

I know that it would be impossible to do this for everyone since our planet cannot sustain more life, but theoretically is it possible to do this?

What are you views into this?

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Ageing is a disease. Just as treatments have been found for other diseases, ageing can be slowed or reversed as well.

Not that long ago, scientists noticed that at the end of each DNA strand there were thousands of nucleotides. Nucleotides are used for genetic coding. That is to say, certain sequences of nucleotides instruct the body to synthesize certain proteins when the genetic code in the DNA is being read. DNA is really like a massive software program.

In any case, when scientists noticed all of this code at the end of a DNA strand, at first they couldn't figure out what is was for, so they thought it must be gibberish. Later they noticed that everytime a cell divided (e.g. everytime the DNA was read) a piece of this gibberish was lopped off. Eventually it became understood that this "gibberish" was the basis of aging.

Each lopped off piece was termed a telomere. Each telomere contains the same nucleotide sequence (code). There are about 15,000 telomere nucleotides at the end of the DNA strands in an embryo. This has been shortened to about 10,000 when you are born and when it reaches a length around 5,000, the body dies. It turns out that the telomeres play a role in stabilizing DNA strands during the copying process, when their length gets down to around 5,000 nucleotides the telomere length becomes to short to provide adequate stabilization and errors (genetic mutations) occur in the copying process and/or the cells become senescent (become inactive, go to sleep). Errors or sleep, either way, the body stops functioning efficiently.

This telomere shortening occurs during cell division in all human cells except for sperm and egg cells. Sperm and egg cells are immortal. There is an enzyme called telomerase, it is expressed only in the sperm and egg cells. After these cells divide a telomere is lopped off, but telomerase re-adds a telomere to the DNA in sperm and egg cells. Hence, their telomere length never shortens - they live forever.

All cells contain the code to make telomerase, but that code (or signaling) is turned off in all cells except for sperm and egg cells. A specific protein combines with a certain portion of DNA and that is all that is required to prevent telomerase expression in a cell.

If scientists could find a way to prevent that (repressor) protein from complexing with DNA, then telomerase expression could be turned on and that cell would then be immortal.

As you can imagine, this is a big area of research. Here is a link to a company that has been active in this area for a long time, and here is a link to a basic tutorial on the subject of telomeres. Poke around the web site, the videos and other tutorials are extremely interesting. Even aspects such as the social consequences of curing aging are discussed.

Enough progress has been made that you can buy products in the over-the-counter market that reduce telomere shortening, but they're very expensive at the present time.

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    $\begingroup$ -1: I'm no expert on microbiology, but I believe there's a lot more than just telomere shortening that causes aging. There's a biologist, Aubrey de Grey, who identifies 7 causes of aging of which only the first will benefit from a fix to telomere shortening. $\endgroup$ – Garrett Mar 29 '15 at 19:32
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    $\begingroup$ @Garrett wrote, "I believe there's a lot more than just telomere shortening that causes aging. ". There probably is. Like all diseases there are probably multiple approaches to delay, eradicate and/or reverse the effects of ageing. Take a look at this link where a number of experiments are described that provide a "proof of concept" for the significant involvement of telomeres on ageing. Again, I agree that there may well be other approaches, but a lot of money and effort appears to have been focused on this one. $\endgroup$ – ron Mar 29 '15 at 21:45
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    $\begingroup$ There's oodles of evidence that teleomere shortening is not the primary cause of aging, ranging from little to no correlation between telomerase activity and lifespan through to an almost complete lack of significant lifespan extension in model organisms from modifications to telomeres (save for early death if they get really short really fast--but that's true of everything). $\endgroup$ – Rex Kerr Mar 30 '15 at 2:22
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    $\begingroup$ Also, sperm and egg cells are absolutely not immortal. In fact, they age faster than many other cell types (e.g. human women's eggs lower in quality dramatically by the 40s, when many other cellular processes are still humming along fine). Instead, it is that they are a step in the immortally-privileged process of the lineage of the species; exactly what step in that process confers immortality (or age-reversal) is not fully clear, but it is clear that it is not the lack of aging of sperm and egg cells themselves (or their progenitors). $\endgroup$ – Rex Kerr Mar 30 '15 at 2:31
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    $\begingroup$ @RexKerr I agree that sperm and egg cells are not immortal, it was the DNA contained in these cells I was speaking about. Let's agree to disagree. $\endgroup$ – ron Mar 30 '15 at 2:38
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There is no chemical reason why life couldn't be prolonged at least somewhat. There are a huge variety of undesirable biochemical reactions (oxidation of proteins for instance) that cells must deal with as part of being alive, and given that lineages are immortal (as the process of growing up and creating germ cells and then fusing them into a new being somehow resets the aging process) we can see that chemical immortality is entirely possible.

In fact, that's what DNA is: the chemically immortal molecule.

But there are all sorts of practical reasons why it may be difficult. There is extensive research in a variety of organisms implicating all sorts of fundamental biochemistry in lifespan: insulin signaling, the EGF pathway, TOR, the unfolded protein response, and so on. Ultimately it is not the chemistry which is the barrier: life already knows how to select and grow its way out of any undesirable side-reactions. It is the biology: can you actually regulate yourself to do the biochemistry you need to do to live longer?

So the answer to this chemistry question is: chemically speaking, it's a biology question.

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To provide a more abstract answer not particularly founded in science, have you considered that we have a finite lifetime in order to encourage us to reproduce and therefore create/promote genetic variability.

Thus providing a far greater chance for our DNA to live on forever (albeit in a different form). This seems to already offer us immortality in some way. Unless of course global disaster strikes causing total extinction.

To me it seems this is the only way to achieve true immortality as something as simple as a disease mutating could wipe us all out, variation is what allows DNA to continue to live.

Ultimately what would living forever allow us to achieve, there would be no goal in life and instead the potential for our DNA's death would increase as other reproductive organisms evolve and adapt.

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