24 June 2021
Over the last 150 years, our life expectancy has grown, from 40 years in 1850 to over 90 years today in some countries. This can be attributed to advances in medical science, improvements in public health, and equitable access to healthcare, especially for maternal and infant care.
What will the future hold for our world? Will we be overwhelmed by a ‘silver tsunami’ of retirees with poor health, or will we use the latest research findings to rejuvenate the elderly and extend their lifespan?
Our Longevity Futures is a show where I, Chris Curwen, speak to scientists, engineers, entrepreneurs, doctors, politicians, and community activists who are giving the world the hope that we can all live longer and better, and improve our health.
A few months ago, we had the opportunity to sit down with the husband and wife team of Professor Michael and Professor Irina Conboy.
Both are Professors at the University of California, Berkeley in the Department of Bioengineering. Their discovery of the rejuvenating effects of young blood through parabiosis in a seminal paper published in Nature in 2005 paved the way for a thriving field of rejuvenation biology.
The Conboy lab currently focuses on broad rejuvenation of tissue maintenance and repair, stem cell niche engineering, elucidating the mechanisms underlying muscle stem cell ageing and making CRISPR a therapeutic reality.
In today’s talk with Michael and Irina, we discussed their most recent paper “Diluting blood plasma rejuvenates tissue, reverses ageing in mice”.
Here are some of the highlights for my conversation with Michael and Irina:
Chris: Could you just give me an overview of what your 2005 parabiosis study was and what have we learned since then concerning the relationship between ageing and the blood?
Irina: Yes. So our 2005 study was really focused on hypothesis that ageing could be reversed in all mammals rather quickly, because before that people thought that once you have shortened to a mere separated DNA damage, genetic shift then it is a single destination train, which does not go back. So that was the hypothesis of the 2005 study Mike and I started exploring experimentally back in 2002.
And Michael’s had this idea that because we age synchronously in various parts of our body, the system that connects those parts is bloodstream or circulation, so therefore we wanted to look at the factors of circulation. The goal of the study never was to prove that young blood could work as a medicine, and to our opinion, that never was computed or conclusive from the outcome.
Chris: Could you tell me the results of your recent study?
Michael: Sure, so let me do a quick bridge between the parabiosis, right? So the parabiosis is like a Siamese twinning of the young and the old animal and they share blood.
But they also, because they’re connected for a very long time, I mean a relatively long time, they share the tissue and organ systems of the partner. So the young animal suffers half its mass, or more than half its mass, being old, and having old liver or kidneys, blah, blah, blah.
The old partner gets access to a young set of liver, and kidneys, and pancreas, and insulin regulation, and digestive system, and whatever. So we didn’t know for sure if it was the effects that we saw were because of the blood or because of the other systems that kind of communicate through the blood.
The next experiment we did was that it was a blood exchange. So we just took two animals and transfused blood back and forth back and forth between them. And then after several exchanges, you approach homogeneity between them -so there’s about 50/50 – and then disconnect them.
And because the only thing that was transferred was the blood we could rule out the effects of workings and re regulatory systems. So from that work, we found that the liver was improved in the old animal, the muscle regeneration was improved, the brain wasn’t really all that improved, and the young partner that got old blood, the muscle regeneration was a little worse.
The liver couldn’t really see much of a defect that the things that we looked at but their brains look like they got stupider. So then at the end of that, we said ‘Okay, now did this happen because the old animal got an infusion of young factors, young, pro-youth factors? Or, did it see improvement because it got rid of half of its old bad factors?’
And conversely, the young animal did it get worse because it got these old factors or because it got rid of half of its good factors? So what if we could do a blood exchange like we did between the young and the old animals, but with each of them have them exchange with something that was neutral.
And we tried to figure out what age of mouse could be neutral, but it’s difficult to point to a particular age. So we said what if we just hypothesized say, okay it’s, let’s say it’s not the red blood cells and it’s not the white blood cells and that leaves plasma. So what if we had some blood that we throw out the plasma and replace it with purified saline and purified albumin, which is like the major ingredient in plasma, but it doesn’t have any factors in it, so it’s just devoid of factors – doesn’t have any old factors doesn’t have young factors – and do the exchange with that. Would the old animal look a little younger and would the young animal look a little older? So that was the basis for the experiment that we did. We took old mouse blood and pelleted the red blood cells and the white blood cells and threw away the platelet rich plasma.
So it’s got albumin in there, it’s got antibodies in there, it’s got platelets for clotting, and it’s got all the old factors that would be in old blood. And replace that with saline mixed in with the major purified component of blood, this albumin.
And then did the exchange with the old mouse with that, and we did some with young mice too, so that at the end the old animal has all its red blood cells, and has all its white blood cells and has half of its platelets, and it has its plasma diluted in half by this purified plasma, basically.
So that technically what the experiment is and then what we found was rather surprising. I didn’t expect the old animal to be really all that much improved. I figured some things might change, but in other ways it would get worse, but it didn’t seem to get worse and pretty much everything we looked at.
Chris: So, as you said in this study, half the plasma of the mouse is replaced. Can you explain how this is actually done and what kind of controls you had set up and how this might be scaled up to humans potentially in the future?
Michael: Yeah, so it’s almost easier to work from humans back, right?
If you’ve ever given blood: stick a line in your arm needle, in a major vein and blood comes out and flows into this bag, and the bags full, they unplug you, and you’re done. Sometimes they say “Hey, come back. We’ll do a phoresis and we’ll collect platelets. Or they’ll say we’ll get a double batch of red blood cells. For that, what they do is they put two lines in and the blood comes out and goes into this machine that separates the blood. So you get the red blood cells going one direction and the white blood cells going another direction, the platelets going in a third direction, and the plasma going to the fourth direction. And then they can recombine all that on the other end to come back in to give you back three out of the four. Or they can also infuse stuff in. So when you’re donating platelets, the platelets go off into one bag and everything else, the red blood cells, the white blood cells, the plasma, comes back into you. And that way they can take a lot more platelets than they could from just one unit volume of blood.
And this has been around for decades, right? And they also use the same technology for people that have, let’s say an auto-immune disease, right? So they’re their blood is full of an antibody that’s autoreactive against some of their own tissue and they’re gonna die from that.
So they run the blood through this type of technology. And then they do the same thing, they pull out the plasma that has the antibodies in it and throw it away, and replace it with a saline solution that has albumin in right. Some people have a organ transplant, and they’re gonna reject the organ, so they do a similar kind of thing. They pull out the parts of the antibodies. There’s other parts of the immune system too, that will react against the against the donors tissue. So they can pull that stuff out and and separate it, but give the patient back their own red blood cells, their own white blood cells, because you’re not really getting anything foreign from somebody, it’s just some salt solution and purified protein.
Your own body’s immune system doesn’t usually react to it. So that’s easy enough to do with people. With mice, you can’t access like some vein on their arm because it’s super, super tight. Their veins start like where our capillaries end. Not really, cause everything’s governed by the size of red blood cells, but they’re very small.
So technically what we have to do is we have to access the biggest vein we can find, which is the mouse’s jugular vein, and you stick a tube in there, and then from that tube, then you can pump in and out small amounts of fluid or blood or whatever. So that’s technically how it was done. And so we had our old mice that got exchanged with other old mice, that’s a control, in old mice that get exchanged with this neutral age blood made from purified, albumin and saline.
And then we also did as control young mice that were exchanged with other young mice. Of course, in previous work, we had done those controls and then young mice and that was change with old mice.
Chris: So you say in your paper that the results do not exclude the possibility of beneficial factors in young blood, having a rejuvenating effect. Is it theoretically easier remove or neutralise harmful factors than to identify and introduce beneficial ones? And does this research bring us closer to an effective plasma therapies in humans?
Michael: Identifying factors, whether they’re good young factors or bad old factors, I think is equally difficult. But to get if you’re old and you want to get your young factors by getting units of young blood or young plasma that has problems.
And that the problem is that the host’s immune system can react against the graft, the donor blood, and vice versa, that donor blood can react against the host. And once this reaction happens and everybody’s immune system starts participating and and it can go to hell in a hand basket pretty quickly.
I’m not an MD and I’m not a necessarily expert on this, but little bit of reading I’ve done makes me think that the risks, the serious risks that you get from receiving a unit of blood product, whether it’s plasma or whole blood, is on the order of about a percent per unit.
So if you’re getting a litre, that’s four units, if you’re getting two liters, that’s eight units. So we’re getting close to about 10% risk for some of the, some people that are getting a lot of this young blood product. Whereas if you take your old blood and you run it through one of these apheresis machines, the risk for a full replay of plasma is altogether on the order of a percent or less, right? So the risks are much, much less to not get someone else’s potentially reactive blood, but to try to clean up the blood that you have. And, but like you said, I ultimately, I think it’s going to come down to identifying the factors, right?
What are the factors that are in old blood that we need to neutralise? And what are the factors that are young blood that we can add back, in which case then the risks probably dropped even lower than that.
Chris: And how does your study compare to say Dr. Harold catcher’s recent publication about the plasma fractions causing significant rejuvenation in middle-aged rats?
Michael: I’m going to make it a point not to comment too much on of course appears to be a pre-print or a manuscript.
That’s just released for comment because it hasn’t really gone through the peer review process. Generally I could say that that there’s, there’s not, it’s not just him. There’s other people that have looked at young blood and we’ve looked at factors that are in young blood or old blood – like oxytocin – for a long time others had looked at fibroblast growth factors.
Irina: So are numerous approaches published by others. They’ve demonstrated multiple tissue rejuvenation, oxytocin the published in nature communications, it’s cited, I think, a hundred times or more, 200 times. There is factors that are produced by human embryonic stem cells which were published, I think four papers and there is Biotech called Juvena, I’m on scientific advisory board and I’m a stakeholder, so I would like to disclose. We’ve published on specific factors so there are of course numerous proteins that could work in a limited fashion to rejuvenate tissues.
Chris: So obviously with some of the ageing studies they use epigenetic clocks to determine the aging of the subjects. Is this something that you’ve looked at, or I was just wondering what your thoughts were on that as a biomarker of ageing.
Irina: So of course again we looked numerously at changes in epigenetics which is, or you may know, is not something in adults that is programming or reprogramming.
They’re not programmed or reprogrammed once they are adults, otherwise it would be in trouble. So for example, in our work, in most recent work, we show comparison in 500 or 300 proteins and how the levels change. That of course means that the proteins are elevated as we see them. For example, youthful factor becomes now higher after neutral blood exchange or therapeutic plasma exchange.
It means that the gene expression is reset to a different level as a model, in figure 6. And there is more transcription, that is a more openness of the epigenetic locus for the gene, which is again, as a textbook information. It does not either not known or something that, we discovered. When we look specifically at some rejuvenative treatments, for example, we published on stem cells in 2015, if you look specifically at tri-methylated histonase 3, K4 versus K 27, we do see a restating to younger state. I’ve learned with the, not look at what is called cloak. So we do not look at those specific loci, which people implicate in chronological age. We are establishing collaborations to do that. But if you simply are asking, is epigenetic status rejuvenative, of course it is. You don’t have to look at the time. We know that if RNA polymerase 2 is bounced to gene promoter, then methyl binding proteins cannot bind, DNMT cannot bind, and then the locus wouldn’t remain open.
If there is less transcriptional factor, some call them pioneer transcriptional factors, then there is less RNA polymerase 2, and then of course, all of the methylation promoter changes take place. So it is textbook biochemistry.
Michael: Anytime we have a change in tissue, state, or cell gene expression state, you get an epigenetic change. So just the process of seeing a rejuvenation of a particular tissue, you’re going to have an epigenetic change.
Irina: Now what is the surprising to me that people tried to separate them and say “Oh, you see rejuvenation and proteome rejuvenation” but this is also actual rejuvenation. If you look at any diagram in cell and molecular biology textbook, those are just different levels of regulation of gene expression. They are not separate from each other.
Michael: The scientific shock would be someone who sees a change at rejuvenation or a change in tissue state, and doesn’t see the epigenome change. That would be novel!
Irina: Let’s put that point there because it’s not really our discover. It is something that is textbook. Undergraduate students learnt it in BIO 1A in first year at Berkeley when they’re 17 or 18 years old.
And so it is important that we do not forget that point. As Mike said, it would be surprising that if you observe the reduction of fibrosis inflammation, reduction of SASP, senescence associated secretatory phenotype, you do not see corresponding epigenetic change. Yeah. And it is important perhaps to remind people.
Michael: As a diagnostic tool, or an investigative tool looking at the epigenome, may not be a bad idea. There’s a, we look at a transcriptome and then often compare that to the proteome. So you can see what genes are turned on and do they make proteins and does that accumulate, right?
Yeah. Having yet another tool looking at the epigenetic marks on the chromatin is certainly valuable. And in some cases, maybe it will be easier to get different information or better information than you would from the other methods. Yeah. We’re working on that.
Chris: So it seems to be that the elevated factors in old blood is maybe more of the culprit to aging. What is dumping these factors into the blood? Like where are they coming from?
Michael: To link it to another, I think it’s still very viable theory of ageing, is a they call this inflammaging, right? So you have more inflammation in the body. And a lot of these inflammatory molecules they’re not just used by the immune system, a lot of them are influence other tissues, too. The immune system uses them to differentiate the immune cells into their final activated, and infection fighting state.
But other tissues will use the same molecules, or very similar molecules, and same sibling pathways to differentiate their respective tissues. And see that in muscle, we see that in neural tissue, and so on and so forth. So those factors tend to accumulate with age. And there’s a lot of overlap I think, between what we found elevated in the old blood, and what seems to be reduced or signal to be reduced, after a round of this neutral blood exchange or therapeutic plasma exchange. So in a short statement, I guess that would be the kind of the running model that we’re working on.
Chris: And just finally, one last question. So we often have people that want to experiment on themselves that, sometimes called the bio-hackers. If they’ve read your paper and they looked into it, what would you suggest to people who will try to self-experiment to make themselves younger by your method?
Would you warn them against it or say, wait a bit.
Michael: Technically, this isn’t as easy as just drawing a unit of blood. Technically you need, not just the equipment, you need the high quality reagents replacement fluid. We’ve seen a facility that does this and one of our collaborator Kiprov was has been doing this for decades.
It takes it takes some serious skill, right? A lot of the, a lot of the risks for them. They’re not graft versus host, they’re not immune auto-reactive kind of stuff, but they’re often I guess like thrombotic, someone throws a clot or the line is clogged, or, some technical thing like that, that that you don’t want an amateur being responsible about.
I guess for the biohackers, I would say wait, right? If you have a medical condition, you have access to a doctor and you want to, and they agree to do this, it’s FDA approved, but we know that doctors that do this, know the risks, should know the risks. And I guess they could discuss it with them. That was the whole point of linking it to something that’s FDA approved is that it’s not necessarily that it’s a shorter path to actually may turn this into a therapy.
Yeah for biohackers, I’d say, wait on this a little bit, whatever. People can give blood, they can give a unit of blood or, or give some platelets or something like that or whatever, and donate some plasma. We know the blood banks know what the risks are and how often too much donation is too much. They monitor your hematocrit and whatever, that kind of stuff. Yeah, go ahead and do that. That’s fine. You get some cookies, right?
Don’t overdo it. They have limits on that. But you’ll probably feel better.
You’ll definitely feel better about yourself and you get a cookie out of it. So you help somebody. It’s a win win.
We really appreciate both Michael and Irina taking the time out of their day to come and talk to us. A massive thank you from Chris and everyone on the Gowing life team. You can keep up-to-date with all that the Conboys and their labs are doing here.
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