39 replies to this topic

[Link]

http://www.news-medi...stem-cells.aspx

Researchers have shown they can reverse the aging process for human adult stem cells, which are responsible for helping old or damaged tissues regenerate. The findings could lead to medical treatments that may repair a host of ailments that occur because of tissue damage as people age. A research group led by the Buck Institute for Research on Aging and the Georgia Institute of Technology conducted the study in cell culture, which appears in the September 1, 2011 edition of the journal Cell Cycle.

The regenerative power of tissues and organs declines as we age. The modern day stem cell hypothesis of aging suggests that living organisms are as old as are its tissue specific or adult stem cells. Therefore, an understanding of the molecules and processes that enable human adult stem cells to initiate self-renewal and to divide, proliferate and then differentiate in order to rejuvenate damaged tissue might be the key to regenerative medicine and an eventual cure for many age-related diseases. A research group led by the Buck Institute for Research on Aging in collaboration with the Georgia Institute of Technology, conducted the study that pinpoints what is going wrong with the biological clock underlying the limited division of human adult stem cells as they age.

"We demonstrated that we were able to reverse the process of aging for human adult stem cells by intervening with the activity of non-protein coding RNAs originated from genomic regions once dismissed as non-functional 'genomic junk'," said Victoria Lunyak, associate professor at the Buck Institute for Research on Aging.

Adult stem cells are important because they help keep human tissues healthy by replacing cells that have gotten old or damaged. They're also multipotent, which means that an adult stem cell can grow and replace any number of body cells in the tissue or organ they belong to. However, just as the cells in the liver, or any other organ, can get damaged over time, adult stem cells undergo age-related damage. And when this happens, the body can't replace damaged tissue as well as it once could, leading to a host of diseases and conditions. But if scientists can find a way to keep these adult stem cells young, they could possibly use these cells to repair damaged heart tissue after a heart attack; heal wounds; correct metabolic syndromes; produce insulin for patients with type 1 diabetes; cure arthritis and osteoporosis and regenerate bone.

The team began by hypothesizing that DNA damage in the genome of adult stem cells would look very different from age-related damage occurring in regular body cells. They thought so because body cells are known to experience a shortening of the caps found at the ends of chromosomes, known as telomeres. But adult stem cells are known to maintain their telomeres. Much of the damage in aging is widely thought to be a result of losing telomeres. So there must be different mechanisms at play that are key to explaining how aging occurs in these adult stem cells, they thought.

Researchers used adult stem cells from humans and combined experimental techniques with computational approaches to study the changes in the genome associated with aging. They compared freshly isolated human adult stem cells from young individuals, which can self-renew, to cells from the same individuals that were subjected to prolonged passaging in culture. This accelerated model of adult stem cell aging exhausts the regenerative capacity of the adult stem cells. Researchers looked at the changes in genomic sites that accumulate DNA damage in both groups.

"We found the majority of DNA damage and associated chromatin changes that occurred with adult stem cell aging were due to parts of the genome known as retrotransposons," said King Jordan, associate professor in the School of Biology at Georgia Tech.

"Retroransposons were previously thought to be non-functional and were even labeled as 'junk DNA', but accumulating evidence indicates these elements play an important role in genome regulation," he added.
While the young adult stem cells were able to suppress transcriptional activity of these genomic elements and deal with the damage to the DNA, older adult stem cells were not able to scavenge this transcription. New discovery suggests that this event is deleterious for the regenerative ability of stem cells and triggers a process known as cellular senescence.

"By suppressing the accumulation of toxic transcripts from retrotransposons, we were able to reverse the process of human adult stem cell aging in culture," said Lunyak.

"Furthermore, by rewinding the cellular clock in this way, we were not only able to rejuvenate 'aged' human stem cells, but to our surprise we were able to reset them to an earlier developmental stage, by up-regulating the "pluripotency factors" - the proteins that are critically involved in the self-renewal of undifferentiated embryonic stem cells." she said.

Next the team plans to use further analysis to validate the extent to which the rejuvenated stem cells may be suitable for clinical tissue regenerative applications.

Source: Buck Institute for Research on Aging

Edited by Link, 27 September 2011 - 10:30 PM.

[Elus]

Wow, incredible! This may have far reaching implications if we can get these rejuvenated stem cells to work well in the old and frail.

[revenant]

Very interesting indeed. I will be looking to read that study (September 1, 2011 edition of the journal Cell Cycle)

[Link]

I'm glad you found it interesting, here is a link to the journal home page, i have pasted the abstract below:

http://www.landesbio.../article/17543/

Inhibition of activated pericentromeric SINE/Alu repeat transcription in senescent human adult stem cells reinstates self-renewal

Cellular aging is linked to deficiencies in efficient repair of DNA double strand breaks and authentic genome maintenance at the chromatin level. Aging poses a significant threat to adult stem cell function by triggering persistent DNA damage and ultimately cellular senescence. Senescence is often considered to be an irreversible process. Moreover, critical genomic regions engaged in persistent DNA damage accumulation are unknown. Here we report that 65% of naturally occurring repairable DNA damage in self-renewing adult stem cells occurs within transposable elements. Upregulation of Alu retrotransposon transcription upon ex vivo aging causes nuclear cytotoxicity associated with the formation of persistent DNA damage foci and loss of efficient DNA repair in pericentric chromatin. This occurs due to a failure to recruit of condensin I and cohesin complexes. Our results demonstrate that the cytotoxicity of induced Alu repeats is functionally relevant for the human adult stem cell aging. Stable suppression of Alu transcription can reverse the senescent phenotype, reinstating the cells’ self-renewing properties and increasing their plasticity by altering so-called “master” pluripotency regulators.

[revenant]

Ah ha.. found it clicky

This statement I like

Our results, in concert with previously published

data,also challenge the notion that cellular senescence and ultimately

cellular aging, is always an irreversible process.

Edited by revenant, 28 September 2011 - 11:16 PM.

[Marios Kyriazis]

The use of transposons (including retrotransposons) is very promising in achieving extreme longevity/biological immortality. See here (scroll down the page) http://www.elpistheory.info/page5.htm, also here for basic information:
http://www.thesleepi....info/page3.htm

[Link]

This is a study that i had meant to post a little while ago but it slipped my mind. Scientists found that by exposing old stem cells to a younger extra cellular matrix rather than an aged one, they were able to restore the regenerative properties of the stem cells. A link to an article from New Scientist explaining it below:

http://www.newscient...stem-cells.html
A youthful environment can rejuvenate old stem cells

Adult stem cells can be rejuvenated, simply by growing them in a youthful environment – at least in mice. The discovery boosts hopes that adult human stem cells could be used to grow replacement tissue without the need for embryonic stem cells or complicated cell reprogramming.

Mesenchymal stem cells (MSCs) are found in the bone marrow of adults, and have the potential to differentiate into a range of different cell types, including bone, muscle, liver and nerve cells. Although MSCs have recently been used to grow new trachea on artificial scaffolds, their widespread use in regenerative medicine has been limited.

"These cells have big potential for tissue regeneration, but generally their quality and quantity decreases with age," says Xiao-Dong Chen of the University of Texas Health Science Center in San Antonio.

Several recent studies have shown that the mechanical properties of the matrix in which MSCs are grown can affect the type of cell they turn into. So Chen reasoned that the cell's microenvironment might also influence its regenerative potential.

Chen's team took MSCs from the bone marrow of 3-month-old and 18-month-old mice, and grew these cells on an extracellular matrix (ECM) – the gelatinous scaffolding that makes up the majority of connective tissue – for seven days. Half the young cells were grown on an ECM taken from a 3-month-old mouse, and half on an ECM from a 18-month-old mouse. The same was true of the older cells.
Young vs old cells

Young and old cells showed a 16.1 and 17.1 fold expansion respectively when grown on an ECM from young mice, compared to a 4.1 fold and 3.8 fold expansion when grown on an ECM from old mice.

Chen's group then implanted artificial scaffolds seeded with MSCs of both ages that had been grown on young or old ECM under the skin of mice and left them to grow for eight weeks. When these scaffolds were removed, they found that old cells that had been grown on a young ECM produced just as much bone as young cells, while old cells grown on an old ECM produced no bone.

The results were presented at the Strategies for Engineered Negligible Senescence meeting in Cambridge, UK, this week.

While it's not yet clear why ECM from younger animals is better than old ECM, it is possible that mechanical properties like elasticity play an important role, says Chen.

The finding opens up the possibility of taking MSCs from older people and growing them on a young ECM before using them to produce replacement bone or organs. It might also be possible to inject rejuvenated cells into the bloodstream where they may in turn rejuvenate a person's ECM and promote healing more generally, Chen adds.

Chen's group is now attempting to repeat the experiments using cells from human donors.


This is the original abstract on pubmed:

http://www.ncbi.nlm....pubmed/21248241

Abstract

This study aimed to determine whether aging negatively affects MSC replication and osteogenesis and whether these features could be altered by exposure to an extracellular matrix (ECM) generated by marrow cells from young or old mice. A cell-free ECM was prepared from cultured femoral marrow cells from either 3- or 18-mo-old C57BL/6 mice (young-ECM or old-ECM, respectively). The replication and osteogenesis of young or old MSCs maintained on young-ECM vs. old-ECM as well as plastic were examined in vitro and in vivo. We found that the frequency of MSCs in marrow from old mice, measured by colony-forming cells, was only marginally lower than that of young mice. In contrast, defects in the self-renewal and bone formation capacity of old MSCs were remarkable. These defects were corrected by provision of a young-ECM but not old-ECM. In parallel cultures maintained on a young-ECM, the intracellular levels of reactive oxygen species from both old and young mice were reduced 30-50% compared to those maintained on old-ECM or plastic. We concluded that aging negatively affects the formation of an ECM that normally preserves MSC function, and aged MSCs can be rejuvenated by culture on a young-ECM.

[nowayout]

"By suppressing the accumulation of toxic transcripts from retrotransposons, we were able to reverse the process of human adult stem cell aging in culture," said Lunyak.

I don't understand this. Are they preventing aging as it is happening (which the bolded part seems to indicate) or are they reversing aging that already occurred? If the latter, are they really reversing entropy (impossible) or are they just removing toxins with a continuously needed intervention? What happens when they stop removing these toxins? Does the cell immediately behave old again?

Edited by viveutvivas, 29 September 2011 - 02:54 PM.

[VidX]

All this is getting very very interesting.

Edited by VidX, 29 September 2011 - 04:21 PM.

[VidX]

"By suppressing the accumulation of toxic transcripts from retrotransposons, we were able to reverse the process of human adult stem cell aging in culture," said Lunyak.

I don't understand this. Are they preventing aging as it is happening (which the bolded part seems to indicate) or are they reversing aging that already occurred? If the latter, are they really reversing entropy (impossible) or are they just removing toxins with a continuously needed intervention? What happens when they stop removing these toxins? Does the cell immediately behave old again?

I still need to read that study, but my impression is that they suppress "wrong" signalling (I may be wrong, but key word here is - "transcripts", not some "general garbage") in these cells and the "right" one starts working again. Kind of like removing "white noise" from the Tv signal - the crisp full-hd view returns. Once again - I've yet just skimmed all this, so I may be off the track.

Edited by VidX, 29 September 2011 - 04:29 PM.

[revenant]

Thanks for the links.

This is exciting work

The finding opens up the possibility of taking MSCs from older people and growing them on a young ECM before using them to produce replacement bone or organs. It might also be possible to inject rejuvenated cells into the bloodstream where they may in turn rejuvenate a person's ECM and promote healing more generally,

[nowayout]

Aha, I read the paper and have seen the light:

This is a very important paper.

In a few words (as far as my admittedly limited understanding goes), they have found senescense in stem cells to be largely associated with increased expression of RNA of a specific kind of common "junk" sequences in the genome called Alu sequences. These Alu sequences amplify themselves in the genome by making copies of themselves that get reincorporated in the genome as the cell ages (via reverse transcription). In a way, they are like endogenous retroviruses.

They do not reverse these changes on the level of the genome.

What they do is infect the aged cells with a retrovirus that is incorporated in the genome. This retrovirus then causes the machinery of the cell to continuously produce short sequences of RNA that silence expression of the senescence-associated Alu elements via RNA interference.

This does not fix the cell at the level of the genotype - the deleterious copies of the Alu elements are still there in the genome. However, it silences them, and the cell is found to revert to youthful phenotype.

Edited by viveutvivas, 29 September 2011 - 08:23 PM.

[VidX]

That's what I assumed initially ^^
Very interesting. It basically demonstrates that - force cells to express the genetic pattern of the "youth phenotype" and they will become young again. Changes in epigenome as a main culprit once again (chromatin modifications/shifts)..

[niner]

Aha, I read the paper and have seen the light:

This is a very important paper.

I couldn't agree more, and your description of the situation was excellent! Thanks for that. I wonder if Alu sequences could be prevented from reproducing through the use of a small molecule inhibitor or some other strategy?

[GhostBuster]

This is my .02 cents of speculation

There is evidence that hanging around with young people somehow helps an older person to stay younger.

Could it be that the visual feedback gives a person a signal that "I am young" or "these people are an example how I should manifest myself" and then on a molecular level his/her body starts to imitate the younger gene expression profile etc.

I got an impression from the study that the older body "intensionally" makes it old (?). It doesnt make much sense unless taken into consideration the above mentioned point.

Edited by GhostBuster, 30 September 2011 - 12:27 PM.

[niner]

There is evidence that hanging around with young people somehow helps an older person to stay younger.

Could it be that the visual feedback gives a person a signal that "I am young" or "these people are an example how I should manifest myself" and then on a molecular level his/her body starts to imitate the younger gene expression profile etc.

I got an impression from the study that the older body "intensionally" makes it old (?). It doesnt make much sense unless taken into consideration the above mentioned point.

I don't think so. This phenomenon of retrotransposons replicating themselves is ultimately just physics. There isn't any 'intention' about it. That would be like saying that the apple falls to earth because it wants to. Hanging around with younger people will keep you on your toes and keep you stimulated, and these things will ultimately play out in your health for various reasons, but I don't think that Alu sequences are involved in it.

[nowayout]

I couldn't agree more, and your description of the situation was excellent! Thanks for that. I wonder if Alu sequences could be prevented from reproducing through the use of a small molecule inhibitor or some other strategy?

Reverse transcriptase inhibitors perhaps?

If so, this experiment has been in progress for decades already, albeit with a huge confounder, in the HIV patient population. (My personal observation is that healthy HIV positive guys often look phenomenal for their age.) Since these drugs are now starting to be given to uninfected people at risk, we'll see what happens.

[Marios Kyriazis]

I don't think so. This phenomenon of retrotransposons replicating themselves is ultimately just physics. There isn't any 'intention' about it. That would be like saying that the apple falls to earth because it wants to.

I think you are wrong here. Many conventional scientists believe that there is 'intention' in Nature, which goes beyond physics. Check out the terms 'Action Ontology' and 'Intentional Stance'. I mention this because it is important in antiaging - if retrotransposons 'try' to replicate themselves, there must be a reason deeper than just Physics.

[nowayout]

I think you are wrong here. Many conventional scientists believe that there is 'intention' in Nature,

No they don't.

[niner]

I wonder if Alu sequences could be prevented from reproducing through the use of a small molecule inhibitor or some other strategy?

Reverse transcriptase inhibitors perhaps?

If so, this experiment has been in progress for decades already, albeit with a huge confounder, in the HIV patient population. (My personal observation is that healthy HIV positive guys often look phenomenal for their age.) Since these drugs are now starting to be given to uninfected people at risk, we'll see what happens.

Hmm.. There's this:

BMC Biochem. 2011 May 5;12:18.
Effect of reverse transcriptase inhibitors on LINE-1 and Ty1 reverse transcriptase activities and on LINE-1 retrotransposition.
Dai L, Huang Q, Boeke JD.

Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
BACKGROUND:

LINE-1s (L1, Long Interspersed Element-1) are the most abundant autonomous non-LTR retrotransposons in the human genome and replicate by reverse transcription of an RNA intermediate. Full-length L1 encodes two open reading frames (ORF1, ORF2) and ORF2 has reverse transcriptase activity.
RESULTS:

Here we expressed human L1 RT in E. coli and the purified protein displayed the same RT activity as that of ORF2p expressed in insect cells. We tested the effect of different reverse transcriptase inhibitors on L1 RT and found that all four tested nucleoside inhibitors efficiently inhibited L1 RT activity competitively. The Ki values of NRTIs were calculated (AZTTP, 16.4 ± 4.21 nM; d4TTP, 0.73 ± 0.22 nM; ddCTP, 0.72 ± 0.16 nM; 3TCTP, 12.9 ± 2.07 nM). L1 RT was less sensitive to non-nucleoside reverse transcriptase inhibitors, among these nevirapine had no effect, even at concentrations up to 500 μM. We also examined the effect of RT inhibitors on L1 retrotransposition efficiency in vivo using a cell-based retrotransposition assay. Similarly, all analog inhibitors decreased L1 retrotransposition frequency with different potencies whereas nevirapine had little or no effect on L1 retrotransposition. For comparison, we also tested the same inhibitors to highly purified RT of an LTR-retrotransposon (Ty1) and found it was less sensitive to NRTIs than L1 RT and has the same inhibition profile as L1 RT to NNRTIs.
CONCLUSIONS:

These data indicate that bacterially expressed L1 RT is an active reverse transcriptase sensitive to nucleoside RT inhibitors but not to non-nucleoside inhibitors.

PMID:21545744
PMCID: PMC3103432 Free PMC Article

That's LINE-1, not Alu, but the Wikipedia page on Alu notes: "Alu elements do not encode for protein products and depend on LINE retrotransposons for their replication.", referencing http://www.ncbi.nlm....pubmed/16344113 . It might be possible to design a non-nucleoside inhibitor that was specific for the LINE-1 functionality that's responsible for Alu incorporation.

[VidX]

My personal observation is that healthy HIV positive guys often look phenomenal for their age

I'll try to make a search on public figures in this context. Just out of curiosity.

[Elus]

I wonder if Alu sequences could be prevented from reproducing through the use of a small molecule inhibitor or some other strategy?

It seems like they've successfully prevented the deleterious effects by suppressing the Alu sequences. At that point, the Alu sequence replication may not matter. RNAi is known to be effective system wide, which is why I say that it may not be a problem.

Also, does anyone know whether or not such suppression of Alu sequences hurt or help differentiated cells in the human body? I know that allowing cells greater replicative ability may lead to things like cancer (Which is why the Alu sequences might be there in the first place: to prevent the old cells which have accumulated damage in tumor suppressor protein-encoding regions from going beserk and becoming full blown cancer).

However, imagine that you could give immune cells which are senescent such a virus, and allow them to replicate once more so they can undergo clonal expansion to fight off intruders that an aging immune system might not be able to fight off normally.

This is a great example of research published in 1998, a little more than a decade back for which RNA interference was recognized by a nobel prize, being applied to incredible research like this which could lead to positive clinical outcomes in the real world.

Edited by Elus, 11 October 2011 - 09:57 PM.

[nowayout]

Also, does anyone know whether or not such suppression of Alu sequences hurt or help differentiated cells in the human body? I know that allowing cells greater replicative ability may lead to things like cancer (Which is why the Alu sequences might be there in the first place: to prevent the old cells which have accumulated damage in tumor suppressor protein-encoding regions from going beserk and becoming full blown cancer).

Actually Alu elements are associated with several human diseases and cancers (http://en.wikipedia....iki/Alu_element). Since Alu elements cause disordered mutations by polluting the genome with copies of themselves, they seem to be an unlikely mechanism for preventing cancer.

I believe they are considered at this point in our knowledge to be nothing more than selfish gene parasites. Simply another runaway degenerative pathology that natural selection has not eliminated because it affects the host too late in life. Alu elements occur only in primates and its origin seems to have been a replication error in a common ancestor:

The fact that Alu sequences are only found in primates, however, probably means that even if we could eliminate their effect, it is still unlikely that we would eliminate senility, which after all doesn't only occur in primates. On the other hand, since they are the most abundant retrotransposon in the primate genome, and other species have their own retrotransposons, perhaps the lesson is that retrotransposons in general may be a major cause of senility across vertebrates.

It would be interesting to see whether similar retrotransposons are less common or less active in animal species with negligible senility. It would also be interesting to determine if rodents have an analogous retrotransposon involved with stem cell senility - a rodent model would be really interesting to play with.

Edited by viveutvivas, 12 October 2011 - 06:29 AM.

[AgeVivo]

The fact that Alu sequences are only found in primates, however, probably means that even if we could eliminate their effect, it is still unlikely that we would eliminate senility, which after all doesn't only occur in primates. On the other hand, since they are the most abundant retrotransposon in the primate genome, and other species have their own retrotransposons, perhaps the lesson is that retrotransposons in general may be a major cause of senility across vertebrates.

It would be interesting to see whether similar retrotransposons are less common or less active in animal species with negligible senility. It would also be interesting to determine if rodents have an analogous retrotransposon involved with stem cell senility - a rodent model would be really interesting to play with.

this indeed seems a great piste against ageing. i haven't read the paper *yet* but ask some obvious questions:

- How strange to tackle a massive cellular ageing mechanism in humans that mice do not have! Is that "rejuvenation" really due to the Alu sequences? or could it be that the technique also tackles smthg larger/else than Alu sequences?
- would their technique work for a whole organism? (eg injected in blood)
- where can we find which transposons are mostly found in mice and in humans?

[revenant]

Could silencing alu sequences have deleterious implications? I have not located the full text.

• Nucleic Acids Research
• Volume34, Issue19
• Pp. 5491-5497
  
  http://nar.oxfordjou...4/19/5491.short
  
  

  Alu elements should therefore be considered as a large reservoir of potential regulatory functions that have been actively participating in primate evolution.

Edited by revenant, 25 October 2011 - 01:38 AM.

[okok]

Could silencing alu sequences have deleterious implications? I have not located the full text.

• Nucleic Acids Research
• Volume34, Issue19
• Pp. 5491-5497
  
  http://nar.oxfordjou...4/19/5491.short
  
  

  Alu elements should therefore be considered as a large reservoir of potential regulatory functions that have been actively participating in primate evolution.

http://nar.oxfordjou...2f-6f393679c417

[revenant]

ty

Edited by revenant, 23 November 2011 - 04:56 AM.

[ihatesnow]

Could silencing alu sequences have deleterious implications? I have not located the full text.

• Nucleic Acids Research
• Volume34, Issue19
• Pp. 5491-5497
  
  http://nar.oxfordjou...4/19/5491.short
  
  

  Alu elements should therefore be considered as a large reservoir of potential regulatory functions that have been actively participating in primate evolution.

http://nar.oxfordjou...2f-6f393679c417

http://www.scienceda...11123190408.htm

[revenant]

I wonder if simply taking ALA could be of some benefit in preventing Alu sequence copies. It is apparently an effective RT inhibitor.

http://www.ncbi.nlm..../pubmed/1724477

"An over 90% reduction of reverse transcriptase activity could be achieved with 70 micrograms alpha-lipoic acid/ml,"

[nowayout]

I wonder if simply taking ALA could be of some benefit in preventing Alu sequence copies. It is apparently an effective RT inhibitor.

http://www.ncbi.nlm..../pubmed/1724477

"An over 90% reduction of reverse transcriptase activity could be achieved with 70 micrograms alpha-lipoic acid/ml,"

If this is the case, why is ALA not an effective HIV therapy?