May 26, 2008
If You Could Rejuvenate Three Parts Of Your Body

Suppose you find a lamp that contains a genie. Suppose the genie grants you 3 wishes to make parts of your body young again. You have to use the wishes by age 55 (before most old age diseases become apparent) or immediately if you are already over 50. The wishes are for only parts of the body. Each could make an organ (and the skin is an organ) or subsystem (e.g. immune cells or spine) young again. You couldn't wish your entire chest or entire leg be young again. But you could wish your heart or your muscles to return to youthfulness. Also, you could wish any other single organ (or pairs in the case of eyes, kidneys, or other organs that come in pairs or all the parathyroids that come in quadruplets) to be young again.

Okay, with these restrictions in mind what would you wish to make young again in your body?

A woman friend of mine would waste no time in wishing her skin young again. No sags, discolorations, wrinkles. But she'd be at least partially disappointed since the bones in her face and the rest of her body also age and shift around. Also, one would really need to rejuvenate fat cells as well in order to rejuvenate the face. Would you go for appearances? You could opt for younger skin, fat cells, and bones. This would yield benefits other than with appearances.

Some people will have an easy decision to make if they already have heart problems or perhaps failing kidneys or liver damaged by hepatitis C or alcohol. Imminent threats make prioritizing a much simpler task.

Before reading further have you made up your mind? Next I'll say what I would choose for my top rejuvenation wishes.

The first thing I'd go for is a totally rejuvenated vascular system. This would greatly reduce the risk of heart attack or stroke among other cardiovascular diseases. But it would also help the brain substantially by cutting back on brain microbleeds, probably reducing inflammation that leads to Alzheimer's disease, and reducing risk of dementia. My problem would be in deciding when to opt for the therapy. At 50? Or at 55? If I wait longer will I suffer from some otherwise avoidable brain damage? Or will I benefit more by protecting my body into a more distant future?

After the rejuvenated vascular system I would opt for a rejuvenated immune system. Why? Of course some old folks die from influenza and other diseases because their immune systems are too weak. But that is not my biggest reason. One of the most interesting research reports of the last year reported aging immune systems become less able to kill early stage cancer cells. If I could know exactly which organ I might get cancer I would opt to rejuvenate that organ. But since I can't know which organ poses the biggest threat the next best way to cut my cancer risk (short of total body rejuvenation) is to make my immune system young again and far more able to kill aberrant cells before they develop into a full cancer.

Notice how I'm not going for internal organ rejuvenation. That's because I do not know which internal organ of mine puts me at greatest risk. Now, maybe 5 or 10 years from now blood tests and biopsies of internal organs will provide us much longer warnings of which organ looks likely to fail first. In the future then I'd want to have up-to-date lab tests before using my wishes. Heck, given such wishes I would want to go for a full physical even with today's testing capabilities. But absent a firm idea on which organ will fail first my preferences lean toward the circulatory system and immune system.

My third choice is hardest. I could just guess on some internal organ like the heart or maybe the liver or prostate and say "give me a new one". Maybe it would make sense to look at a list of causes of death and choose the organ that rates highest in combined causes. For example, liver failure and liver cancer both kill.

But I'm strongly biased toward rejuvenating my brain. First off, doing so will boost my productivity. Second, I'll avoid the risk of assorted causes of dementia, especially when combined with vascular rejuvenation. Plus, the brain does a lot of chemical endocrine signaling to the rest of the body (e.g. from the hypothalamus). That signaling will be done better by a younger brain.

So what's your list? Got good reasons for rejuvenating one part of your body or another?

Share |      Randall Parker, 2008 May 26 11:10 PM  Aging Debate

David Govett said at May 27, 2008 12:29 AM:

Might want to consider rejuvenating your stem cells, which also age.

ldom said at May 27, 2008 1:15 AM:

rejuvenate your pen1s!

Lyle said at May 27, 2008 4:11 AM:

I'm been reading you for too long Randall as I also chose the brain and immune systems as well (assuming that my current personality and immunities wouldn't be destroyed). For my third, I'd choose my pulmonary system. By the time I'm 55, I expect (hope) that my major internal organs (eyes, liver, heart, kidneys) will be relatively replaceable through achievable methods. My lungs on the other hand probably won't be replaceable, and the quality of life issues and damages related to difficulty breathing (strokes, brain damage) is something I would like to avoid.

Allan said at May 27, 2008 7:43 AM:

Salamander-inspired therapy may aid injured vets

Brock said at May 27, 2008 9:08 AM:

I guess it depends on whether or not further rejuvenation will be available in the future. If not I'd make the same picks as Randall to get the most mileage out of the body I have. If yes than I might make more short-term quality of life decisions (like Randall's lady friend). I'm too far removed from 55 though to know what those would be; nothing is particularly worn out yet at 30.

bfwebster said at May 27, 2008 9:28 AM:

I'd definitely go for vascular system and brain for 1 and 2 -- third would probably be muscular system. ..bruce..

Fritz said at May 27, 2008 9:47 AM:

Oh, I would most definitely start with the skin. My brain is doing ok...everything else is functioning real well. ;)

But the skin, mainly sun damage from years of enjoying the outdoors. Check out my blog to see what I have been going through this month.

Fly said at May 27, 2008 2:56 PM:

"Might want to consider rejuvenating your stem cells, which also age."

Yes. In particular bone marrow stem cells. I think you could do this by injecting a few hundred stem cells in your blood each day. The injected cells would gradually replace the original stem cells in the bone marrow. (The replacement could be accelerated by using a drug that mobilizes stem cells.) By injecting "young", genetically enhanced cells you might become better than original.

Bone marrow is the source for the cells that become the immune system. I suspect bone marrow stem cells also re-supply stem cell niches in other tissues. If so, young bone marrow might lead to young skin or better memory from rejuvenated stem cells in the hippocampus.

Young stem cells aren't a complete answer to tissue rejuvenation. The signaling environment of old tissue hampers healing. Essentially all tissues have a replacement rate. E.g., intestinal lining turns over every three days while skeleton and fat average about a decade. (Even heart muscle cells and brain neurons are replaced, but too slowly to significantly repair damage.) If the tissue replacement rate could be locally accelerated, heart damage and strokes might self heal.

TTT said at May 27, 2008 5:12 PM:

1). Brain for sure.

Everything else is secondary.

It is all just fantasy, though. While aging will slow down to enable lifespans of about 110-120, there will never be a reversal of aging. Even inanimate objects like cars, clothes, and electronics age and deteriorate over time. Nothing can stop it. Fantasy to the contrary can be fun, but merely wanting something badly does not make it happen.

Randall Parker said at May 27, 2008 5:38 PM:

Stem cells:

1) They are not a single kind. Therefore all together count for more than one wish.

2) The body has many different stem cell reservoirs. Just knowing which type to put in each place is a huge research project. Creating each type is another huge research project. We haven't even found all the places where stem cells can be found or what each type is in each place.

3) Still, we do have some obvious candidates. Stem cells for the immune system are an obvious possibility. Stem cells for bones are another obvious possibility. Also, stem cells in the brain.


If you can replace parts you can turn back the clock. The more parts you replace the more you turn back the clock.

Larry said at May 28, 2008 6:23 AM:


Fly said at May 28, 2008 6:47 AM:

"1) They are not a single kind. Therefore all together count for more than one wish."

Yes, but bone marrow may act as a stem cell source for several different tissues. (E.g., blood, immune system, fat, muscle, bone, sperm and egg progenitor cells.) When BM stem cells engineered to make green florescent dye were injected into a mouse the marked cells were found to migrate among stem cell niches in different body tissues. Also, tissue analysis of females who received BM transplants from males found a small percentage of male cells incorporated into some of their organs. Finally, when a mother is pregnant with a male fetus some of the male cells (not BM stem cells) enter the mother's blood system and become part of her body.

There is also evidence that stem cell reservoirs in different body tissues age at similar rates. This is surprising since different tissues have very different metabolic rates and cell replacement rates. A common stem cell reservoir that acts as a replacement source for all stem cell niches would explain this result. Admittedly such a general source would require adult totipotent stem cells or de-differentiation steps which haven't yet be observed in humans. (De-differentiation does occur in salamander limb regeneration.)

Imagine a small implant powered by glucose and radio controlled. The implant would allow nutrients to flow into the capsule and wastes to leave. Inside the implant would be totipotent, young, genetically engineered stem cells. Under remote control the capsule would cause the cells to divide and then provide the necessary mechanical and chemical signals for differentiation into the desired cell type. (Imagine a manufacturing line with totipotent stem cells entering and progenitor cells leaving.)

Implants might be specialized for different body tissues. I.e., some engineered cells would make better muscles and would be used in an implant for muscle regeneration. Other engineered cells would be better for neuron genesis in the hippocampus. Specialized implants would placed in critical tissues.

The implants would be very small and replaceable. With mass production they would be cheap. (Cell lines would be engineered or tissue matched to prevent rejection.)

cancer_man said at May 28, 2008 9:06 AM:

Peak oil will doom us all anyway...

So we have rejuvination but no breakthroughs in energy until... 2030?

What an odd place this planet is to have so much potential in one area whilestagnation in another.

TTT said at May 28, 2008 12:13 PM:


That is what gets us to 110-120. But even in a car or TV, you can replace parts. That prolongs the life, but does not make it last indefinitely. Over time, every inanimate object and living creature eventually deteriorates.

I want immortality as much as you do. I just won't believe it until I see it.

Pops_Out said at May 28, 2008 12:35 PM:

"Each could make an organ (and the skin is an organ) or subsystem (e.g. immune cells or spine) young again."


Your second choice is, quote, "a rejuvenated immune system." Bearing the above^ in mind, would that include only the immune cells themselves, or the organs that synthesise them (bone marrow, thymus, etc), as well? If the latter, is there a case for lumping the heart together with the vasculature to protect one's cardiovascular system, rather than each component alone?

My choices, in order, are the cardiovascular system, brain and immune system.

You're doing a great job on this site, by the way. Keep it up.

David Govett said at May 28, 2008 3:44 PM:

Since each human body is a unique system, rejuvenating individual parts could have adverse effects. Imagine a young heart with an old vascular system. One stroke. Two strokes. Three strokes. You're out!

Randall Parker said at May 28, 2008 5:41 PM:


I take your point on the immune system. The thymus is a distinct gland. I suspect that if we just replace the circulating T cells that'll buy us a lot. I'm about to do a post quoting a recent Aubrey de Grey speech about immune system aging that I came across after writing the above post.

TheOldMan said at May 29, 2008 11:08 AM:

Brain, heart, lungs

Bob Buchanan said at May 29, 2008 11:22 AM:

You guys are all too young. How about: 1. New joints; 2. New muscles (if too broad then the multifidi). Now that the pain is gone I could consider a new brain, eyes, or perhaps new immune system

Jeff said at May 29, 2008 11:24 AM:

My feet/ankles/knees are my worst enemies - they're failing, painfully. So I'd go with tendons & ligaments.

Clancy said at May 29, 2008 11:30 AM:


Right now (I'm 39) I'd do:
eyes (I have extremely poor eyesight)
immune system (I have psorasis & arthritis - both immune system diseases)

I'd save the last wish, but probably use it on the vascular system

Achillea said at May 29, 2008 11:50 AM:

1) Spinal cord, since I suffer from RSD.

2) Spinal disks, to keep the herniated ones from again damaging the spinal cord.

3) Immune system, for the reasons listed above. Though, truth be told, I don't seem to get nearly as sick these days as I did when I was young.

Jack MacKenzie said at May 29, 2008 12:12 PM:

Brain, metabolism, hormones

TTT said at May 29, 2008 12:23 PM:

OK, I'll change my answer :

1) Brain
2) Eyes
3) Cardiovascular system (so as to avoid both heart attacks and strokes).

Mainly, I want to preserve my earnings capacity and ability to be independent in caring for myself. Brain and eye functions are the most important for that.

dustydog said at May 29, 2008 12:29 PM:

Soul, definitely the soul. Mom screwed me, scheduling my baptism before I got a chance to really sin it up.

Mark Buehner said at May 29, 2008 12:41 PM:

Can I get my liver done 3 times at 15 year intervals? Maybe 10 years, now that i think about it.

Rex said at May 29, 2008 12:53 PM:

Knees (which I'm having replaced soon), heart (which is now using a pacemaker), and either eyes (corrected by glasses) or shoulder (which I separated, but supposedly is correctable by surgery if I really need to). I'm interested in my current quality of life, rather than living longer than I normally would.

UncleFred said at May 29, 2008 1:02 PM:

Well its your poll but IMHO you are sort of cheating. If the heart counts as a single choice then so to should a particular vein or artery, or a particular muscle not a "system" like the immune system or the vascular system. Despite that my choices would be heart, kidneys, brain. These choices are based on failings in my family history.

sbw said at May 29, 2008 1:07 PM:

I'd go for the mitochondria. Without an energy-producing subsystem churning out ATP where are you.

Second I'd turn back the teleomeres to stop my cells going into senescence.

Third, I'd... I'd... Ask for three more wishes?

mark James said at May 29, 2008 1:11 PM:

There is a paradox with the immune system that is very misunderstood.

The reason some live to a very long age is apparently not the strength of the immune system, it is the weakening of the immune system which keeps us alive longer. Its a paradox.

The reason is the Mitochondria. That is the first "organ" you want to regenerate, (although they are an organism or some say simply DNA, but not an organ).

As Mitochondria age, they begin to "leak" free oxygen into the cells, which starts the degeneration process. A strong, healthy immune system will aggressively attack this free oxygen, killing you with kindness and good intentions. ;-)

A weaker immune system does not attack free-radical oxygen very effectively. So while the free-radical oxygen does damage to cells and tissues, slowly causing breakdowns, but not as much as an over-hyped immune system. Its been suggested that the best predictor of longevity is a life-threatening, or serious illness when young, i.e, a weaker immune system.

It would be interesting to see if treated HIV positive individuals live longer than the general population, as this theory suggests they might.

But the two first "organs" I would regenerate are the Brain and Mitochondria. After that, there are many candidates. ;-)

Dave in St. Louis said at May 29, 2008 3:15 PM:

Well, my priorities are a bit more urgent than most. I have Islet Cell or Neuroendocrine Tumors. They have spread to my liver. I had a partial pancreatectomy. The Number One thing I'm going to want is a regenerated, disease-free liver. Number Two is a regenerated pancreas (so I can quit being a surgically induced diabetic). After that, it's pretty much a crap shoot (even though my spleen is gone). But, probably a regenerated vascular system makes the most sense. Rewinding the telomeres would probably be a good idea, but that and the mitochondria seem beyond the scope of the question.

GeoffB said at May 29, 2008 5:05 PM:

I'm only 35, but the future is a bit foreshadowed for me, so here they are:

1) Teeth - very useful for good digestion
2) Colon - I have ulcerative colitis
3) Spine - to keep the spinal cord and nerves coming out from it happy

Peggy Snow Cahill said at May 30, 2008 5:54 AM:

Brain, heart, spine

Speedwell said at May 30, 2008 6:31 AM:

Kidneys... had trouble with mine and wouldn't mind do-overs.
Brain. Just because.
Metabolism. Is that a body part?

Philip Efiom said at December 9, 2008 9:50 AM:

It is my blessed day to find people thinking of rejuvenating. This is what nature has as the factor for limitless existence. Genesis 1:29 is the diet man must GO BACK to for the bodyto reverse the old age syndrome of sickness and death. The enamel on my upper left molar has OBEYED. I call the diet ECOLOGY DIET or 4Fdiet (4F= Fire Free Fresh Food ) Fire degrades, therefore man has been existing on degraded nourishment hence the time frame.

jelal kader said at March 17, 2010 4:09 PM:

my pituitary gland you would become basicaly young again the growth and regrowth system so your fat cells your bones stem cells everything will be replaced with new younger cells and stuff so that almost takes care of the apearance and body issues if you think your body will get over zized it is impossible because we are made of genes and body evolved itself into its current form it will not change the genetic cod or you dna to make you a different size.if your muscles will also grow back

my brain because in early stages of development your brain can learn allot more but for example if your 2 years old you dont know the basics so if you get a new brain not only does the movement of the body become easier but you gain focus quick thinking and learning capabilities. because you lose cells in your brain over time and you need them to learn so making it young again would let you learn like a child in 1 month you could learn a language.

metabolism because it takse care of your body and eradicates most diseases thats why you never get that sick when your young like normally kids dont get cancer diabetes or other bad diseases that kill so in a sense i would fully regeneate my body and be maybe better than before.

i am 11 i do not need any of this just thought i would comment on this if you had that choice i highly recomend these body parts

jelal kader said at March 17, 2010 4:12 PM:

not metabolism imune system sorry i am the on with the comment above me

gejala stroke said at August 29, 2016 7:48 PM:

Gejala Storoke ringan dan cara menanganinya secara alami harus diperhatikan selalu secara serius , karena saat ini kasus penyakit stroke banyak terjadi dikalangan masyarakat dari mulai stroke ringan hingga stroke berat.
Meski yang dialami masih gejala stroke ringan tapi penanganannya harus secara tepat karena bisa berakibat fatal jika tidak diatasi dengan obat stroke yang ampuh. Sebelum kita membahas lebih lanjut mengenai pengobatan stroke, maka kita harus mempelajari dulu tentang apa itu penyakit stroke, penyebab penyakit stroke, gejala stroke,
serta bahaya apa yang bisa muncul? Setelah itu baru kita bisa memilih obat stroke yang tepat yang akan kita gunakan.

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