15 replies to this topic

[John Schloendorn]

Outline for a putative project “Cell therapy for aged mice”

Stem cell therapies are being used to treat mouse models of various degenerative diseases with increasing success. The following outlines a project that would attempt to synthesize these techniques to treat wild-type, but aged mice. The ultimate goal of this type of research would be full functional rejuvenation of every renewing tissue, with a clear prospect of translatability to humans. Cellular replacement offers a unique opportunity for rejuvenation, in that it can potentially reverse all intracellular causes of aging in one blow, without even the need to know anything about them. The project being considered here understands itself not only as an attempt to accomplish part of this ambitious goal also as an incentive for others to join in.
The project has the advantage of being highly modular: The number of tissues, cell lines, genetic modifications, animals (and animal species?) is adjustable to the resources available and the observed rate of progress.

An obvious organ to start with is the hematopoietic system, which has three key advantages: First, its complete replacement is fairly established in mice and humans. Second, immune tolerization can be achieved by hematopoietic replacement, opening the door for allogenic transplantations for further rejuvenation therapies in other organs. [1] Third, it is thought that hematopoietic stem cells can, in principle, home to and regenerate a number of other organs. Perhaps, engineering appropriate homing capabilities into these cells can be a starting point to rejuvenate such organs. Bispecific antibodies could also be valuable here. [2]
A first milestone of the project in question would be the total replacement of the hematopoietic system with young cells and the subsequent monitoring of blood cell age markers, (t-cell subpopulations ect.) blood cell function and incidence of blood cell degenerative diseases and cancers.
If a sufficient degree of hematopoietic rejuvenation can be achieved, milestone2 would be multiple repetition of the procedure in the same animals to see if blood cell aging can be continually suppressed, while the animal’s other tissues continue to age. Suicide, chemosusceptibility and chemoresistance genes might be used to facilitate later rounds of hematopoietic replacement and ease the side effects of the cell removal on other tissues of the aging animals. In such a scheme, each subsequent generation of hematopoietic cells would carry a different combination of such genes, so that they can be selectively removed, without harming subsequent populations of cells. The treatment of cancers that may derive from the new cells using inbuilt suicide mechanisms should also be investigated.
The multiple genetic modifications to the hematopoietic stem cells might be effected using a highly reliable mammalian artificial chromosome (MAC). Recently, a suitable MAC engineering (ACE) system has been announced.[3] MAC-carrying stem cells may be generated by direct transfection by “sonoporation” [4] or the generation of transgenic animals that may serve as cell donors. [5]

For other tissues/organs, the basic strategy would remain the same. The choice of subsequent tissues/organs should depend on the observed causes of disease and death in the hematopoietically rejuvenated animals and on future research results and methodological improvements achieved by then.
One putative organ is skeletal muscle, where it has been prominently noted that the rejuvenating effect of any fresh cells is limited by the systemic environment of the old animals.[6] A potential remedy is to short-circuit the respective signaling receptors, as to make them permanently active in the absence of ligand.[7] It is conceivable that such short-circuiting may result in excessive proliferation under some circumstances. This could be controlled by keeping the respective genes under the control of an inducible promoter. Once the desired degree of cellular abundance is reached, the inducer would be withdrawn, arresting proliferation.
The heart is close to postmitotic, but still bone marrow derived stem cells can be utilized to heal limited lesions.[8] This may provide a starting point for the very gradual replacement of all heart cells: Limited lesions would be inflicted, perhaps using ultrasound or surface-marker targeted toxins, and assisted regeneration would be initiated. It would be interesting to see if such a process can be repeated until all heart cells have been replaced, without compromising the heart’s structure and function.
Early attempts to replace the rapidly renewing gut by reseeding of its stem cells showed some promise, but do not seem to have been developed much further since then.[9] If other tissues can be rejuvenated to a degree that makes serious gut problems become apparent, it could be attempted to revive this technology.
The skin is another rapid-turnover organ that should be looked into. We now have a fair understanding of the role of epidermal stem cells in skin turnover[10] , but there do not seem to be any actual skin stem cell reseeding techniques. Given the importance of ECM modifications in skin aging[11] , stem cell therapy might have a limited effect. Tissue engineering of skin patches and repeated transplantations could be an alternative approach, to effect full skin rejuvenation. [12]

I have tentatively picked the mouse as model animal, obviously because of the huge amount of mouse methods available. However, mice usually show a distribution of causes of death that is fairly different from human aging. Perhaps animals should be chosen that more closely resemble humans in this respect, where appropriate methods are available. Rats, cats and dogs seem attractive, but I can’t say that I’m very familiar with these models at this time.


[1] Werkerle T et al. Mechanisms of tolerance induction through the transplantation of donor hematopoietic stem cells: central versus peripheral tolerance. Transplantation 75(9 Suppl): 21S-25S

[2] Lum LG et al. 2004 Targeting of Lin- Sca+ hematopoietic stem cells with bispecific antibodies to injured myocardium. Blood Cells, Molecules, and Diseases 32: 82-87

[3] Lindenbaum M et al. 2004 A mammalian artificial chromosomen engineering system (ACE system) applicable to biopharmaceutical protein production, transgenesis and gene-based cell therapy Nucleic Acids Research 32(21): e172

[4] Vanderbyl S et al. 2004 Transfer and stable expression of a mammalian artificial chromosome into bone marrow-derived human mesenchymal cells. Stem Cells 22(3): 324-33

[5] Co DO et al. 2000 Generation of transgenic mice and germline transmission of a mammalian artificial chromosome introduced into embryos by pronuclear microinjection. Chromosome Research 8(3): 183-91

[6] Conboy I and Rando T 2005 Aging, stem cells and tissue regeneration: Lessons from muscle. Cell Cycle 4(3): [Epub ahead of print]

[7] Conboy IM et al 2003 Notch-mediated restoration of regenerative potential to aged muscle. Science 302(5650): 1575-7

[8] Davani S et al. 2005. Can stem cells mend a broken heart? Cardiovascular Research 65: 305-16

[9] Tait IS et al. 1994 Generation of neomucosa in vivo by transplantation of dissociated rat postnatal small intestinal epithelium. Differentiation 56: 91-100

[10] Morasso MI and Tomic-Canic M 2005. Epidermal stem cells: The cradle of epidermal determination, differentiation and wound healing. Biol Cell 2005 97(3): 173-83

[11] Giacomoni PU and Rein G 2001 Factors of skin ageing share common mechanisms. Biogerontology 2001. 2(4): 219-29

[11] Greenberg S, Margulis A, Garlick JA 2005. In vivo transplantation of engineered human skin Methods in molecular biology 289: 425-30

[John Schloendorn]

Provided that they get a grant I will be doing this at the tissue engineering department of the uni of Sheffield, UK.

[jwb1234567890]

Looks like a very interesting project! my random thoughts:

I didn't really get the method for inducing immune tolerance from the abstract, how does this method stop the newly introduced stem cells from attacking the host cells? (is it by clonal deletion of the T cells which would attack the body? if so how are they recognised?)

One issue I see with your initial approach is that if you suddenly give the host a whole new immune system then it spots lots of old damaged cells and ablates them leading to a more rapid decline in the host.

Also I wonder if it is possible to reverse the process that is talked about in [1]. I.e. induce tolerance within the host body then do the transplantation. I am thinking here more of other organs such as liver etc for which currently there are problems as you have to match the person up directly. This would have the benefit of being immediately applicable in the medical arena. Also this means that when we get to the stage of tissue engineering organs we will then immediately be ready to implant them without fear of immune rejection.

For your other putative target tissue which is muscle... one of the main reasons that the muscle deteriorates is the ramping down of various hormones, So rather than fiddling around with Delta and Notch of the muscle cell why not replace the source of the problem the endocrine system, Of course the problem with this is that then you would end up causing increased incidence of cancer, so this would have to be heavily coupled with an anti-cancer therapy.

Alternatively there has been success in rejuvenating muscle tissue by extraction of muscle stem cells, clonally expanding them then injecting them back in to the target tissue, again though if this was done body wide cancer increase might be an issue (however I am hopeful that as long as the stem cells go through a rigorous selection process before they are returned to the cell this should be much reduced).

If you do pick the mouse model then p66 should be an easy cancer reduction strategy for you.

Jack IANAB

[John Schloendorn]

Looks like a very interesting project! my random thoughts:

Heh, come on, they're far from random, but reflect a very informed opinion [thumb]

I didn't really get the method for inducing immune tolerance from the abstract, how does this method stop the newly introduced stem cells from attacking the host cells? (is it by clonal deletion of the T cells which would attack the body? if so how are they recognised?)

Good question. I don't think anybody knows for sure. Acute graft-versus-host disease (GVHD) is not caused by progenitor that differentiate into T-cells, but rather by mature T-cells present in the graft. When transplanted hematopoietic stem cells differentiate into T-cells, they seem to imitate the process of thymal selection even in the absence of a functional thymus, which amounts to clonal deletion of the alloreactive cells. (Interestingly they seem to do it in the small intestine.) [1]
An obvious approach is thus T-cell depletion of the graft. This is justly unpopular in the clinic, since bone-marrow transplanted patients tend to have leukemia and leukemia is usually the first thing that succumbs to GVHD (graft-versus-leukemia, GVL). Leukemia relapse is much more frequent in recipients of T-cell depleted grafts. But it is also for reasons of graft efficiency that I would like to avoid this approach. (All this is reviewed in [2])
Another elegant possibility is to deplete graft T-cells, but co-inject donor T-cells that have been transduced with an inducible suicide gene. When a recipient develops GHVD, substrate would be administered to selectively wipe out donor T-cells. If one was having leukemia patients, one could even wait until GVL was successful, before activating the suicide gene. This has been done in mice [3] and men [4]. I am considering the derivation of transgenic donor animals carrying such a suicide gene to avoid donor t-cell depletion and gene therapy.

A secondary issue is chronic GVHD, which seems to be an acquired autoimmune disease, as a consequence of impaired selection of T-cells, including host ones. Chronic GVHD seems to result from some kind of yet-to-be-characterized damage to the selection apparatus that occurred owing to acute GVHD or chemotherapy. [5]

Also I wonder if it is possible to reverse the process that is talked about in [1]. I.e. induce tolerance within the host body then do the transplantation. I am thinking here more of other organs such as liver etc for which currently there are problems as you have to match the person up directly. This would have the benefit of being immediately applicable in the medical arena. Also this means that when we get to the stage of tissue engineering organs we will then immediately be ready to implant them without fear of immune rejection.

Reverse? T-cell replacement has been used for the purpose to achieve donor-specific tolerance towards unrelated organ transplants. Another excellent review is here [6]. E.g. liver cancer patients received a bone-marrow transplant for the purpose of inducing tolerance towards an allogenic liver transplant, and did indeed not reject the graft, but liver cancer, as it usually does, recurred. Other cases include successful treatment of leukemia through allogenic bone marrow transplant, followed by a kidney transplant from the same donor, which was accepted, the loss of allergies and autoimmune diseases after bone marrow transplant, ect.
The major issue with this is that a number of people still die in the process. Suicide genes and other anti-GVHD strategies will hopefully soon enter clinical practise.

For your other putative target tissue which is muscle... one of the main reasons that the muscle deteriorates is the ramping down of various hormones, So rather than fiddling around with Delta and Notch of the muscle cell why not replace the source of the problem the endocrine system, Of course the problem with this is that then you would end up causing increased incidence of cancer, so this would have to be heavily coupled with an anti-cancer therapy.

I do not know enough about the endocrine system to respond, but I will look into it, thanks for bringing it up. Delta though is secreted locally by injured motorneurons and muscle cells and this secretion is impaired in old muscle.
I don't know about cancer. You're saying old stem cells would get activated that had better remained silent, right? I think on this cancer-senescence frontline the possibilities are still open, but you could be right. I hope to bring some light into these things with the research.

Alternatively there has been success in rejuvenating muscle tissue by extraction of muscle stem cells, clonally expanding them then injecting them back in to the target tissue, again though if this was done body wide cancer increase might be an issue (however I am hopeful that as long as the stem cells go through a rigorous selection process before they are returned to the cell this should be much reduced).

Do you have a reference at hand to back that up? To my knowlege this process requires short-circuiting notch in the transplanted satellite cells. Otherwise, they will not regenerate the old muscle due to the absence of delta. [7]
I do not think cancers from the graft are the main issue, because it is young (and thus is not far down the microevolutionary road to cancer) and it might carry multiple suicide genes just in case. Again, I think the largest part of the problem is unintentional activation of slumbering damaged host cells. This is only a problem in the first generation of cells - If all goes well, in subsequent generations the old host cells will be gone. And the younger you are when you receive the first treatment, the better your chances. We shall see anyways.

If you do pick the mouse model then p66 should be an easy cancer reduction strategy for you.

Thanks, I'm not aware of this at all. I found this. Is that what you mean? Do you have more references at hand, especially for background cancer rates rather than specifically induced cancers?

Thanks for writing, best, John.

Edited by John Schloendorn, 28 March 2005 - 02:20 AM.

[jwb1234567890]

Thanks for the info on GVHD.

Why its interesting to induce immune tolerance.. In one scenario you get ESC put aging host dna in them, then tissue engineer organs for transplantation. This has the disadvantage that organs have a longer lead time to be produced. If you could induce tolerance in the host then the organs could be pre created and stored and be instantly available.


http://www.gen.cam.a...abg10/talks.htm - have a look at pawalec slides for why the strategy of replacing the aging immune system may reduce cancer rates.


Your right that notch certainly is involved with muscle loss but I think its upstream of hormones and if you fix the hormones you fix the muscle loss rather than fixing notch which may not be broken. See articles below for an stopping the muscle atrophy of aging via igf-1

http://archives.cnn....arch/index.html
http://www.embl-heid...rt/rr03_158.pdf
If your looking into sarcopenia then look into Nadia Rosenthal who is working heavily in this area.


I am worried about unintentional activation of slumbering damaged host cells. I do believe that one of the reasons that the body doesn't bother keeping hormones at youthful levels is that otherwise cancer incidence would increase. (and from an evolutionary perspective grandparents don't need to be jumping around to take care of children or impart their knowledge so its not such a big loss).


Rejuvenating muscle tissue by extraction of muscle stem cells:
http://www.rsna.org/..._stemcells.html


For the p66 I am afraid I can't find the paper in my notes at the moment so I must have it printed out, I will look for it on Tuesday when I get my hands on my stash of aging papers.

Jack

[John Schloendorn]

Thanks for the exciting IGF-1 stuff! So delta clearly is not only mediator sufficient for muscle repair. These guys should try to combine the two and get a few gold medals in mouse olympics! Unfortunately neither of all these adult stem cell activation works says anything about cancer. Almost suspicious, isn't it. (Or do you know any that do?) I fully agree with you, in that I would be very surprised if the repeated activation of endogenous cells could be sustained in the long run. Sounds almost like a way towards "compression of morbidity" -- live like 21 until cancer gets you.

Funny you point me to Pawelec -- I know him, I studied some 6 years in that same little godforsaken german uni town where he chooses to do his work for some reason ;-) I certainly plan to look into cancer rates in multiple organs of my hopefully immuno-rejuvenated mice. But other organs' other age markers might also be revealing as for the role of mesenchymal stem cell homing in the repair of non-hematopoietic organs (see e.g. the present thread on gut aging).
Aside, cells from Pawelec's super-healthy senior donors (or younger relatives?) might be a cool way to augment the immune systems of the less fortunate. (Are there animals with a particularly anti-cancer effective immune system? (reptiles?) Can one use xeno-immune cells to gain resistance to human-specific infectious disease? Chimeric immune systems to unite the advantages of multiple species? Safe immune tolerization should really open the floodgates to many wonderful toys from nature's construction kit)

Why its interesting to induce immune tolerance.. In one scenario you get ESC put aging host dna in them, then tissue engineer organs for transplantation. This has the disadvantage that organs have a longer lead time to be produced. If you could induce tolerance in the host then the organs could be pre created and stored and be instantly available.

Unfortunately, even major HLA matched tissue recipients can catch GVHD, due to minor HLAs and individual variations in other, completely unrelated plasma and cell surface genes. [1] It's next to impossible to find your perfect match on all these at once -- Another point for tolerization. Such a generalized, local organ bank would sure be a cool thing to have around. (And the tech to engineer a range of organs even cooler [glasses]).

Rejuvenating muscle tissue by extraction of muscle stem cells

Hm, maybe this incontinence thing worked because things are different in smooth muscle. According to the Conboy data, the same thing would have little effect in skeletal muscle. I don't think much is known about smooth muscle notch signalling. Hopefully this is one thing less to worry about then.

Hehe, I used to have a paper stash like that, but now I'm completely digital - it's much easier [sfty] Thanks, from what you said, I'd really appreciate that p66 info.

[jwb1234567890]

Many of these mouse gene experiments are short term and they would have little interest in finding it also boost cancer rates as this would detract from their findings. For sure meddling in this has implication just look at all the issues with Hormone Replacement Therapy in humans.

Sorry about the Pawalec link I should have realised you already had this in mind.

Well there is a very very cancer resistant organism which lives in a high radiation environment unfortuntely its a bacteria (Deinoccus radiodurans) and it has 10 copies of its dna. Though maybe this does have implications with mitochondria.
http://www.wired.com...6,63993,00.html

I would be surprised if you found any organism which had a better anti-cancer immune system than our own. Maybe something like a bat... similar in many ways to a mouse (I am thinking in terms of oxidative stress it goes through) but can live to 38 (MLS).
http://www.pubquizhe...s/lifespan.html - pick your organism:)


I like having paper copies of papers, it allows for general doodles and highlighting which just is not the same on screen:)

I finally found the paper I was referring to I now know why I couldn't not find it on the web the gene was not p66 it is the Ink4a/Arf locus, an extra copy was given.

http://www.genesdev....ract/18/22/2736

Various types of cancer were induced and it was found that the Ink4a/Arf mice were more cancer restistant.

A comparison of the spontaneous death causes was made and it was found that while 60% of wild type mice died of cancer only 22% of Ink4a/arf. (60% seems like a very high cancer rate incidence for mice?) Also they did this on a very limited supply of mice (~10).

I think part of the problem is that it must cost quite a lot of money to do large scale full aging experiment (hotel and food for 1000+ mice?)

If you can't get access to the paper give me a pm.

I think many varied artificial organs/tissues are not too far off clinical use. Tissue Engineering as a discipline has really taken off.

As a half way house I think that immune system replacement + endocrine coupled with a few anti-cancer genes would increase your health/life span (less broken hips, less cold/flus, less cancer, higher energy levels).

What is your planned strategy for the brain? Does this encompass a treatment for alzheimers? (50% of 85 years have it).

Jack

[John Schloendorn]

it is the Ink4a/Arf locus, an extra copy was given.

Very cool! Definitely worth a thought if I should have some space left on any artificial chromosome thingy.

Sorry about the Pawalec link I should have realised you already had this in mind.

No worries, you can't help me too much, but only too little! Thanks again for the feedback!

Well there is a very very cancer resistant organism which lives in a high radiation environment unfortuntely its a bacteria (Deinoccus radiodurans) and it has 10 copies of its dna. Though maybe this does have implications with mitochondria.

Cancer is not an issue for unicellulars. Unrestrained growth is their general hallmark and selective advantage, not a disease state. But you're right, DNA repair for mitos certainly comes to mind, especially if we can tolerize against the respective enzymes. You might want to have a chat with Prometheus about this.

A comparison of the spontaneous death causes was made and it was found that while 60% of wild type mice died of cancer only 22% of Ink4a/arf. (60% seems like a very high cancer rate incidence for mice?) Also they did this on a very limited supply of mice (~10).

Most mice usually die of cancer. This is one of the major ways I was citing in the proposal in which mouse aging differs from human.

What is your planned strategy for the brain?

I have no concrete plans for the brain. There is hope that considerable loss of neurons can be regenerated by ES derived cell therapy, [1] but it is totally unclear what effects such massive cell replacement would have on personality. If I ever get my hands on this type of work, I would like to do some classical conditioning on the recipient animals to confer a model-personality trait, then perform massive neuron replacement, both gradually and in one go, and see if the conditioning persists or can be recovered after dementia.

Does this encompass a treatment for alzheimers? (50% of 85 years have it).

Alzheimers can hopefully be treated in early stages as a storage disease [2], but once neuronal loss occurred one should to consider cell replenishment. But this will probably not be part of my work here anytime soon.


[2] De Grey et al. Medical bioremediation: prospects for the application of microbial catabolic diversity to aging and several major age-related diseases. Aging Research Reviews, in press.

[caliban]

John

I'm sure you don't need me to say that, but be careful not to get carried away.

jwb1234567890 is obviously quite interrested in cancer, and I agree it's very relevant, but if you want to feature that thematic complex in your proposal you are looking at a very different project. Similary with brain etc.
Its always better to be qute distinct in the proposal and do your own stuff by the side.

about the animal model: mice are not great, nor are rats. However, if you want the work in the UK my guess is that you can forget about cats or dogs. Quite expensive, lots of hassle. (But we could look into that if you really wanted to go for it)
Also, you might want to throw in transplantation from aged donors, not only out of scientific interest but to get another selling point (can we use bone marrow transplants from the elderly?) and that would be much easier with rodents. However, are you braced for the fidely bit? I'd imagine that injections with anything that small are a real hassle?

Perhaps, engineering appropriate homing capabilities into these cells can be a starting point to rejuvenate such organs. Bispecific antibodies could also be valuable here

You'll have to elaborate here. Have you discussed Blau's stuff?

This could be controlled by keeping the respective genes under the control of an inducible promoter. Once the desired degree of cellular abundance is reached, the inducer would be withdrawn, arresting proliferation.

Hui. Can I hear the buzzword nano knocking at the door?

Tissue engineering of skin patches and repeated transplantations

Why is this even in there? Once again, if you want to get funding, keep is simple and sane. Don't go for curing death in the first year of your PhD. I'd stick to one organ, (apart from blood)

These are just tidbits, first time I have seen this. I'll have to give it a lot more thought when I get a bit of time.

Caliban

PS:

So delta clearly is not only mediator sufficient for muscle repair.

I don't think Mondey claims as much. I certainly don't. Its always more complex than one would like.

[John Schloendorn]

I'm sure you don't need me to say that

Please, say it anyway ;-) It does help.

Also, you might want to throw in transplantation from aged donors

Yes by all means.

are you braced for the fidely bit? I'd imagine that injections with anything that small are a real hassle?

That's not a real argument, of course, or nobody here would be doing what they do. Others have done it and with such a promise for life-extension, it's worth learning. But sure I have to be aware that I have no experience with these methods at this time. I have taken apart newborn mice often, but not in a way that could compare to surgery, which the animal is supposed to survive ;-)

cats or dogs. Quite expensive, lots of hassle. (But we could look into that if you really wanted to go for it)

I am not so convinced of cats and dogs. I would dare to say that in in cell therapy, the peculiarity of mouse aging should matter less than in other anti-aging disciplines. The rationale behind cell replacement is, after all, that it should largely allow us to forget about about intracellular aging mechanisms, which is where the differences really are.
Perhaps when the technology is more mature, in the very early for-profit phase of life-extending treatments, a niche will open up to allow for a pet-rejuvenation market, but we can't really project that today.

engineering appropriate homing capabilities into these cells

You'll have to elaborate here. Have you discussed Blau's stuff?

Indeed, but that is once I begin to focus on a solid organ (see below). I'm working on it.

This could be controlled by keeping the respective genes under the control of an inducible promoter. Once the desired degree of cellular abundance is reached, the inducer would be withdrawn, arresting proliferation.

Hui. Can I hear the buzzword nano knocking at the door?

Not sure where you here "nano" here. Sounds to me like boring genetics.. It could be relevant because of the funding thingy, so please explain.

Tissue engineering of skin patches and repeated transplantations

Why is this even in there?

Heh, good question. Many of these things will drop out in the detailed version. I mentioned them here also to delineate the position of my work in the "grand scheme of things"...

Don't go for curing death in the first year of your PhD. I'd stick to one organ, (apart from blood)

Hmm... I don't think I should include any other organ, before having really good results with the hematopoietic system. There is heaps of work already with all those suicide genes and artificial chromosomes and stuff (the latter may be too difficult to get my hands on at all). But I'm not sure, I will comment on that again after a few weeks of literature work. (and your other points)

[John Schloendorn]

One issue I missed, sorry Jack:

One issue I see with your initial approach is that if you suddenly give the host a whole new immune system then it spots lots of old damaged cells and ablates them leading to a more rapid decline in the host.

I was indeed more concerned with the contrary. Abundant surface features of senescent, and indeed pre-malignant cells in very old hosts could participate in lymphocyte selection during maturation. Thus, lymphocyte tolerance might be induced against these features, leaving the host more prone to senescence and cancer.
But it is possible that the actual levels of such features are not suitable to induce tolerance and we might see the effect you predicted instead.

However, either type of effect might be reversed when massive cell therapy takes place simultaneously in most tissues. Then there would be very little senescence or malignancy markers available for lymphocyte selection, and the new immune system might become especially intolerant against them.
Destruction of senescent and pre-malignant cells by the immune system, of course would be compensated by direct replacement with young ones.

[Mondey]

For your other putative target tissue which is muscle... one of the main reasons that the muscle deteriorates is the ramping down of various hormones, So rather than fiddling around with Delta and Notch of the muscle cell why not replace the source of the problem the endocrine system, Of course the problem with this is that then you would end up causing increased incidence of cancer, so this would have to be heavily coupled with an anti-cancer therapy.

So how do you proof that it is all due to decreasing hormon levels ?? What is about time-depending modification of the extracellular matrix in the muscle or any other organ, this will influence cell activity. And when you claim it is due to the hromones, why do the hormon producing cells in the organ stop producing the right amount of hormones, maybe because the tissue stem cells of this organ are not functioning properly, because other orgnas are missing. I think it is in the moment to complicate to look at it this way. If you can manipulate the muscle stem cells by blocking numb expression of the cells sourrounding the satellite cells, it is fine. You get what you want, regeneration.

Alternatively there has been success in rejuvenating muscle tissue by extraction of muscle stem cells, clonally expanding them then injecting them back in to the target tissue, again though if this was done body wide cancer increase might be an issue (however I am hopeful that as long as the stem cells go through a rigorous selection process before they are returned to the cell this should be much reduced).

I am not so much worried about the cancer, induction of apoptosis is pritty well regulated in old stem cells, but more that your clonally expanded stem cells, will have so short telomeres, that they are worth nothink. They can only do a couple of cell cycles , before they will become either senescence or apoptotic, and as in vitro expansion oc stem cells induce a fast amount of damage I would opt for the second process. Cancer is more likely to be induced by stem cells, but we have stem cells everywhere in the body, some stem cells more, especially some young and functionable ones, will not increase cancer rate. And then, getting cancer is better tehn dyong of age, cancer can be cut out or ......

Greetings,
Mondey

[John Schloendorn]

but more that your clonally expanded stem cells, will have so short telomeres, that they are worth nothink

I'm sure some here like to say that this could be handled by hTERT gene or protein therapy, but but for some stem cells this does not seem to be as easy as for fibroblasts.

Mondy, I wish I could share your optimism on cancer. I'm in general advocating the use of getting our cells fresh from the germ-line not only to avoid increasing cancer rates, but also to actually decrease them. It's so amazing what people can do with ESC lately. Those who predicted the differentiation of a great variety of functional cell types in the late 90s were, surprisingly, right!

[jwb1234567890]

For your other putative target tissue which is muscle... one of the main reasons that the muscle deteriorates is the ramping down of various hormones, So rather than fiddling around with Delta and Notch of the muscle cell why not replace the source of the problem the endocrine system, Of course the problem with this is that then you would end up causing increased incidence of cancer, so this would have to be heavily coupled with an anti-cancer therapy.

So how do you proof that it is all due to decreasing hormon levels ?? What is about time-depending modification of the extracellular matrix in the muscle or any other organ, this will influence cell activity. And when you claim it is due to the hromones, why do the hormon producing cells in the organ stop producing the right amount of hormones, maybe because the tissue stem cells of this organ are not functioning properly, because other orgnas are missing. I think it is in the moment to complicate to look at it this way. If you can manipulate the muscle stem cells by blocking numb expression of the cells sourrounding the satellite cells, it is fine. You get what you want, regeneration.

Alternatively there has been success in rejuvenating muscle tissue by extraction of muscle stem cells, clonally expanding them then injecting them back in to the target tissue, again though if this was done body wide cancer increase might be an issue (however I am hopeful that as long as the stem cells go through a rigorous selection process before they are returned to the cell this should be much reduced).

I am not so much worried about the cancer, induction of apoptosis is pritty well regulated in old stem cells, but more that your clonally expanded stem cells, will have so short telomeres, that they are worth nothink. They can only do a couple of cell cycles , before they will become either senescence or apoptotic, and as in vitro expansion oc stem cells induce a fast amount of damage I would opt for the second process. Cancer is more likely to be induced by stem cells, but we have stem cells everywhere in the body, some stem cells more, especially some young and functionable ones, will not increase cancer rate. And then, getting cancer is better tehn dyong of age, cancer can be cut out or ......

Greetings,
Mondey

Hi Mondey,
Well I am sure that it is not all due to decreasing hormonal levels. However I would say that the hormonal changes are a very significant reason for sarcopenia. Look at link below for evidence of the effect of hormone therapy on muscle mass.
http://www.gen.cam.a...ppts/Harman.ppt
Also note the putative fix for the hormone imbalance 'Selective Destruction and Regrowth of Leydig Cells in Young and Old Rats' slide.

Of course its also heavily coupled with exercise.
And your genetic makup has an effect:
http://www1.wfubmc.e...?Articleid=1499
And I am sure that mitochondrial dysfunction is also a part of the problem.

I think that the reason that hormone producing cells in the organs stop producing the right amount is because if they did not then cancer incidence would increase in the elderly and cancer kills faster than sarcopenia.

You should be worried about cancer, every year that you get older your risk of getting cancer increases, cancer will end up being the number one killer at the rate we are stopping people from dying from heart attacks. Its not true that most are curable. Some are it entirely depends on which type of cancer you get, if you get a benign one your ok and they can cut it out if not you have a death sentence. Note the wonder anti cancer drug Avastin extends life span by only 2 months, thats the best we can do currently in adults.

Any putative therapy that increases the regenerative capability of the body must deal with cancer as this sort of therapy is inherently increasing the risk of it occuring.

Jack

[marcus]

This is a very interesting project you propose. My first thoughts are it would be nice to get in touch with the doctors in Korea and have a cloned ES cell from the patient to manipulate from the beginning. Then you could engineer a tailor-made hematopoietic system with any genetic modifications you want via Artificial Chromosomes or ex-vivo gene therapy thus spiking the genome of the hematopietic system for ultimate health. A new, young, genomically optimized, blood stem cell system would have to not only offer health benefits on it's own, but could be a potential system for delivering repairs to other tissues and organs via a blood stem cell pathway.

Obviously, we're not at the above vision, yet. However, coercing embryonic stem cells down the path of development toward specific differentiation is a technique that is being refined by several labs. And what the Korean doctors accomplished with the cloning and harvesting of stem cells in a relatively high yield manner was a HUGE accomplishment. And manipulating genomes of cells via ex-vivo gene therapy or artificial chromosome is becoming increasingly easier. So we may not be too far away from something like this.

Like your self, I'm still studying all this and learning...but I can tell by your proposal that we think alike as into what specific kinds of experiments we can begin planning RIGHT NOW that could help pave the way for the development of SENS-like therapies.

Mark