37 replies to this topic

[Mind]

I am no expert (so please bear with me). I am wondering what part of the change in environment produced the reversal of aging. Did the old skin respond to the hormones of the young mouse and become young skin again. Do you think it was a progressive transformation from the outer cells of the old skin patch (in contact with the young mouse skin) toward the inner cells. What do you think would happen if all of the skin of the mouse was replaced with old grafted-on skin? Would it still reverse itself? Does the old skin become new because it is in contact with new skin cells, or because it is in contact with a young body?

[olaf.larsson]

Yes microarray is the way to go. But it will only show changes in m-RNA not the cause of the changes. Damit this things are so fascinating and amazingly complex!!!!! I would like to work with this things even if there would be no chance of acctually make any progress in anti aging and even if I didn´t get any money for the work.

[Hypermere]

I am with you wolfram, I've always felt that this research is so critical that I'd be happy to do it for free. Now I'm being paid to work on Southern blots, building gene targeting constructs, ordering, supervising work study students, on and on. It is like being close but still not having direction. Lately I have been trying to think of experiments or a project or something using my lab's resources and my personal goals. Cuz really, there are not many labs with enough balls to dedicate themselves to aging.

It's tough getting my finger on what would be the fastest way to actually make a therapy for real-life use...youth in a bottle. Any changes in gene expression patterns after reaching adulthood should definitely be characterized over lifespan from maturation until death. The results can be standardized across a sample of species. Then maybe a universal pattern common to all life (except trees and galapagose turtles) which leads to aging could be better defined.

Then once we know what genes are being turned on/off at the dropoff point from adulthood to old, all you have to do is figure out what these genes do and how they interact. Play with some more experiments with knockouts of these genes in different combinations, and then something should come out of it. Kinda like what Wexler is doing. So, long story short, you can use that as a starting point to look for your microcentrifuge of youth.

But that may be way off, but I'm trying to come up with something...soon.

[John Schloendorn]

... unless these gene expression changes are just ways to cope with even deeper, underlying causes. Such as cell senescence, which may ultimately be a means to escape the effects of nuclear DNA mutations (E.g. check out the SENS talk by Campisi). If you reverse senescence, you may well face the consequences of the problem that it acted to solve. These somatic cell "rejuvenation" studies typically content themselves with short-term observation of a few aging markers, but do not provide data to assess what diseases these tissues/animals develop over time, how and when they actually die and whether the procedure can be repeated.
Thus, my favourite approach is replace the cells and don't bother much with what's going on inside them, as long as you don't have to.

[John Schloendorn]

SCNT (using a somatic cell derived from the patient for whom the treatment is intended) can plausibly reverse multiple intracellular causes of aging present in the somatic cell, such as methylation, chromatin state, mitochondrial mutations and lysosomal junk. But nuclear mutations present in the somatic cell nucleus obviously persist.

Thus, I would expect that SCNT-based cell replacement therapy has a good potential to achieve short to medium term rejuvenation, but in the very long run we will want to refresh our nuclear DNA from a more pristine source.

If a long-term post-mitotic cell is used, the nuclear mutation factor might not bear as much weight, since such cells tend not to accumulate mutations over time, because they don't replicate their DNA. (They don't translate DNA damage into mutations like dividing cells do.) But that's wild speculation and only a massive cell replacement therapy based on SCNT derived cells with long-term follow-ups will tell. Btw, I'd love to do just that type of thing and may soon have the chance to try with the hematopoietic system .

[marcus]

Off in the future...What about massive cell repacement using stem cells either derived from the patient or cultured using fertilization techniques? Stem cells are already being used to attempt to repair damaged tissues...what about extending this "repair" to re-seed an organ with fresh cells derived from stem cells?

These cells could potentially be manipulated ex-vivo with gene therapy(ex-vivo gene therapy is likely to be vastly easier than in vitro) to yield cells bearing optimized genomes for overall health and function of their target organ. It seems using stem cells would give you a chance for a "fresh start" on the cellular level and the problem of nuclear mutations would be obviated.

Obviously, I'm thinking off in the future. However, I think there is something to be gained from attempting to paint a picture of what a therapy that reverses aging may look like and then work backwards to understand what steps need to be taken to get there.

[Mondey]

Hi there here I am back with to many questions (and a hallo :-0)

The skin graft experiment is a very nice experiment and not the only one into this direction. What is always missing in these experiments is that they did not follow it up for a longer time. Can the old skin be rejuventaed for a longer time, as long as the young mouse would live, or is it only the last bloom before death ?? And could they proof that not young stem/progenitor cells from the young mouse invaded the old skin through blood vessels in addition to young soluble factors of the young skin ?? The senescence phenotype seems to be not very stable. Sometimes the induction/activation of one gene is sufficient to reverse it (( for a while ??? or permanently ??). But what happens to short telomeres (OK ther is ALT, but does it always work ??), they are not rejuvenated throught the exposure of old cells to a young enviroment or ???

Grettings,

Mondey

[John Schloendorn]

I think these are just the right questions. Given way the academia seems to work, some of these questions might not get the attention they need -- So let's find out for ourselves.

[vortexentity]

The mouses brain is creating new peptides telling this piece of skin that it needs to be repaired. The skin responds to the chemical messages. The mouse due to the fact that it is small and has a fast life time gives the skin a flood of peptide signals to heal quickly.

This is not antiaging on the human skin this is mutation and chemical interaction as these foreign DNA are adapted to the mouse.

I think this has no relavance to antiaging directly but does indicate that the aged human body tissue responds more to peptide messages than a young persons skin no matter that the peptides come from a mouse hypothalamus and not from a human. In older cells there are likely to be more peptide receptor sites than in young skin, thus young skin will not respond to these peptide singals as do older cells that have adapted to an array of peptide messengers over many years.

That is my opinion at least. [glasses]

[DJS]

John

SCNT (using a somatic cell derived from the patient for whom the treatment is intended) can plausibly reverse multiple intracellular causes of aging present in the somatic cell, such as methylation, chromatin state, mitochondrial mutations and lysosomal junk. But nuclear mutations present in the somatic cell nucleus obviously persist.

Thus, I would expect that SCNT-based cell replacement therapy has a good potential to achieve short to medium term rejuvenation, but in the very long run we will want to refresh our nuclear DNA from a more pristine source.

Interesting. I believe that a similar view was expressed by Osiris in his paper and that he suggested the development of "artifical chromosomes as a template which could maintain *perfect* genomic integrity, or at least close to perfect.

In what way would such an artifact be maintained? Please excuse my ignorance on the subject, but I have only recently begun to ponder this issue. Could a template of an individual's genome be maintained ex vivo and used to verify the integrity of a DNA molecule that is to be used in SCNT? Certainly, even in the mitotic tissues of older organisms, there are cells whose DNA is unmutated and fully functional. Basically, couldn't a screening process be used to test for genomic integrity? And -- even if there was a problem in finding "pristine" DNA, couldn't a more fully developed form of gene therapy correct this type of problem?

[DJS]

Ah, I see someone else had similar thoughts here in this thread.

Marcus

These cells could potentially be manipulated ex-vivo with gene therapy(ex-vivo gene therapy is likely to be vastly easier than in vitro) to yield cells bearing optimized genomes for overall health and function of their target organ. It seems using stem cells would give you a chance for a "fresh start" on the cellular level and the problem of nuclear mutations would be obviated. 

[John Schloendorn]

In what way would such an artifact be maintained?

I would prefer to rejuvenate my replacement cells by in-vitro fertilization (IVF). Nature has a fairly powerful system in place here that can perfectly rejuvenate the next generation's cells from adult ones, so I see no urgent need to play with chromosome synthesis and the likes. It seems that we do not have to understand perfectly well how rejuvenation by fertilization works to derive pristine cells for therapy from the process. IVF could arguably lose some quality controls from mate selection and vaginal selection, but this does not seem to strongly impair IVF-derived kids. So the molecular mechanisms seem to be fine.
An interesting experiment would be to derive ESCs by IVF, differentiate them into gametes, IVF them and derive a new ESC line from the blastocyst. Would you get any deterioration after multiple rounds?

Aside, current ESC differentiation methods are no longer an objection. Tissues where models of diseases have been corrected using ESC-derived cells/progenitors include brain, liver, heart, bone-marrow, pancreas and cochlear sensory epithelium (Feel free to ask me for the respective refs or check pubmed).

[olaf.larsson]

How about to take two geneticaly identical or SCID mice, one old and one young and fuse their circulation? I guess the old mouse would be rejuvenated while the young would be aging faster.

[DJS]

John

I would prefer to rejuvenate my replacement cells by in-vitro fertilization (IVF). Nature has a fairly powerful system in place here that can perfectly rejuvenate the next generation's cells from adult ones, so I see no urgent need to play with chromosome synthesis and the likes. It seems that we do not have to understand perfectly well how rejuvenation by fertilization works to derive pristine cells for therapy from the process. IVF could arguably lose some quality controls from mate selection and vaginal selection, but this does not seem to strongly impair IVF-derived kids. So the molecular mechanisms seem to be fine.
An interesting experiment would be to derive ESCs by IVF, differentiate them into gametes, IVF them and derive a new ESC line from the blastocyst. Would you get any deterioration after multiple rounds?

Aside, current ESC differentiation methods are no longer an objection. Tissues where models of diseases have been corrected using ESC-derived cells/progenitors include brain, liver, heart, bone-marrow, pancreas  and cochlear sensory epithelium (Feel free to ask me for the respective refs or check pubmed).

Sorry John, I didn't see your reply until just now. I'm not sure that I entirely agree with your assessment that "nature has a fairly powerful system in place here that can perfectly rejuvenate the next generation's cells from adult ones". This almost sounds to me as if you promoting the idea of the "immortal germ line" - which, I believe, is a bit of misconception. Mate selection and vaginal selection are not to minimized when discussing the robustness of the germ line; particularly vaginal selection. Developmental selection in the form of miscarriages would still obviously constitute a form of selection even in cases of IVF. However, none of this addresses the issue of senescence but rather points to the fact that our procreative cycle with its bottle neck allows for genomic selection in toto.

My basic point is this: I haven't heard an evolutionary rationale that would account for an endogenous mechanism for perfect genomic integrity. Without some form of (yet to be developed) screening there would be a slow creep in the genomic integrity, and thus compatability of cells created and used in rejuvination treatments. Regardless, I view this problem (if it even is a problem) as something that does not need to be addressed in the short term.

By the way, I like your idea of deriving ESCs via IVF and then "cycling" them to test for long term genomic deterioration. Such an experiment could be quite revealing.

Don

[DJS]

Hey Prometheus. I was merely reflecting John's terminology by using the phase vaginal selection. I guess in utero selection would be a more appropriate term?

As for your second question, let me get back to you on it. There is a reason why I said what I said, but I want to think over my response to make sure my line of reasoning is sound.

Later
Don

[Mark Hamalainen]

2. In which way is an immortal germ line a misconception?

Sorry I must add my two cents here... I'm also interested in your (Don's) opinion as well though.

I've been thinking about this and it seems to me that this is a problem of confused terminology. Aging and evolution are both a result of imperfect information copying. However, a distinction needs to be made between them.

The germ line is continually expanding and being culled by natural selection. The selection is a continual process throughout germ cell's existance. Whether a sex cell matures successfully, survives sexual reproduction (for example, vaginal selection), and produces a somatic body capable of reproducing are all part of this selection. Every cycle of reproduction contains a bottleneck where only one cell passes, only 1 cell from each pair of mating organisms is contributed to the new organism. All the other trillions of cells produced alongside that 1 die. This is not the sort of immortality we speak of in our quest to make our somatic bodies immortal, and to use the same term for both is confusing and inaccurate.

It is not at all suprising that out of the trillions of cells produced by the gametes that combined to make an organism that one of them contains information content capable of repeating the process.

Imagine taking a single germ cell and tracking its existance over time. Its probability of still being alive would inevitibly continue to decrease even if all extrinsic factors were removed.

The germ line is not immortal, it is evolving.

[John Schloendorn]

I'm not sure that I entirely agree with your assessment that "nature has a fairly powerful system in place here that can perfectly rejuvenate the next generation's cells from adult ones"

I meant this in a way that leaves no room not to be sure (except to question your senses). The next generation is perfectly rejuvenated, in the sense that species do not go extinct by cell damage that accumulates in the germ line. (As Osiris rightly points out, this type of rejuvenation can be said to be even slightly more than perfect, i.e. involves evolution). A valid question remains whether we can make "perfect" therapies from these cells, and in which sense of "perfect", which I suppose is what you meant? Here, I'm not sure what your point is, so I guess I'll wait for the post you announced before I really reply [sfty]

Vaginal selection is the selection of at most one sperm out of many incoming ones for fertilization. It is thought to be influenced by the legendary "sperm race", menstrual cycle phase, perceived male attractivity, nutrient availability and others. It might be thought to have effects on average cell fitness, but I have no clue. Just an idea. IVF could be used to test if it does.

Endogenous in utero selection (by reabsorption of the fetus) could important here, too. IVF-derived kids would be subject to it, i.e. the fitness of those that make it could get statistically "fixed" by reabsorption of some broken ones, while embryonic stem cells would not, because they can be harvested before this type of selection is fully brought to bear. (I'm not sure how prevalent this mechanism is at all in humans)

My mate selection point was wrong (I just realized). Nearly all actual IVFs involve couples that did select each other.

I think these cell or fetal selection thingys are of minor or no importance for therapy, but I'm just saying I could be wrong.

[Mark Hamalainen]

In reality it is not the cell itself that concerns us, but the maintenance of genomic/epigenomic integrity and in the case of an organism, the maintenance of physiological function in cells, tissues and organs.

True, with each division cycle the probability of a cell in the pool undergoing apoptosis increases so statistically the possibility of it being still in existence decreases.

That is true, but it wasn't the factor I was thinking of. What proportion of mutations are deleterious as compared to beneficial (neutral mutations can be ignored)? Eventually the genetic information will be corrupted if there is no selection. We are not designed with internal selection capabilities capable of maintaining our information indefinitely. This applies to tissues as well as to cells. Our cells do perform selection on each other to an extent. The immune system can recognize and destroy misbehaving cells in some cases, but not all. Corruption of the information in cells is inevitable without intervention or natural selection.

But it is important to define what we mean by biological immortality

Exactly. The sort of immortality experienced by the germ line is not the same as what we desire for ourselves. Not to say that there is nothing we can learn from the germ line, but the sort of immortality it achieves is not translatable into immortality for a somatic body.

[DJS]

Prometheus

the germ line represents a pool of cells and not a single individual so that given the right conditions its genomic integrity can be maintained and is therefore biologically immortal.

The (right conditions) would be an adequate supply of viable germ line cells, plus external selection to weed out any biological deterioration. The way I see it, all biological integrity is maintained by the force of natural selection (directly or indirectly), regardless of the point in the life cycle at which it occurs. Why then must the germ line be distinguished as immortal rather than just "Life" itself?

Osiris

The sort of immortality experienced by the germ line is not the same as what we desire for ourselves. Not to say that there is nothing we can learn from the germ line, but the sort of immortality it achieves is not translatable into immortality for a somatic body.

Yes exactly Osiris, you've said everything I wanted to say, only better than I could say it. Your conceptual framework makes a lot of sense to me, but I wonder, are there any criticisms of it?

John

A valid question remains whether we can make "perfect" therapies from these cells, and in which sense of "perfect", which I suppose is what you meant?

Yes, in my usual confused way that was what I was getting at. [lol]

My point John is this "genetic creep" that I mentioned in my earlier post. You have stated that this would not be important for rejuvination therapies (I'm assuming you mean in the short term). But what would happen if the genetic content started to degrade? Would the cloned tissues lose some of their functionality? Or could there be more of a chance of an immune response to cells with a genetic content that is less than a 100% match (histocompatability issues)?

I'm curious, couldn't this type of genetic corruption be prevented by performing artificial selection in the form of genetic comparative screenings followed by the weeding out of less than perfect cells? How far away can we be from personal genomic sequencing? I'm sure its probably much more complicated than this...

[John Schloendorn]

Ah. Starts to make sense [thumb]. So you're saying we can't maintain the germ-line indefinitely without any natural selection. I imagine a bioconservative fiction writer could think of a scenario where immortals breed a reserve of mortal humans in a stone-age environment under high natural selection pressure to harvest germ cells for rejuvenation therapy from them [:o].
My honest guess is that this problem will vanish in the wake of accelearting change, and I don't normally say things like that. It might be where Osiris' de-novo chromosome synthesis come in. Or we will have some really old germ cells frozen, and we might find a way to exponentially amplify ESC from them.
In the end it all depends on two rates: How fast will we be running out of progeny willing to donate germ cells for rejuvenation therapy and how fast will our own germ line corrupt in the absence of natural selection, but under increasingly efficient human selection. It is the rationale behind the repeated IVF experiment I mentioned above to arrive at a crude guess of the latter.

[John Schloendorn]

histocompatability issues

These are huge issues for contemporary "spare parts" therapy of single disorders but I don't think it will remain one in rejuvenation therapy, because rejuvenation therapy will involve replacing the immune system, which tolerizes it against any antigens it finds. Immune-replaced patients get tolerant towards unrelated organ transplants, lose their allergies and autoimmune diseases, ect. If you have only the slightest objection against this reasoning, please speak up, this is really important to me.
(I have cited relevant references dispersed in this thread)