While fish and other amphibians can regenerate heart muscle throughout their lives, for unclear reasons, mammals cannot. In fact, the human heart is the least regenerative organ in the body, which means that when someone has a heart attack, the portion of cardiac tissue that dies never regenerates, and this is what leads to heart failure. Dr. Charles E. Murray is a professor, cardiovascular pathologist, and director of the Center for Cardiovascular Biology at the University of Washington, and a solution to this problem is being created in his lab. Dr. Murray is using stem cells to grow beating, human heart muscle cells—unlimited amounts of them that can be used as seeding material for additional heart tissue regeneration. Once injected into the damaged portion of heart tissue, the cells begin dividing, connecting with each other, and connecting with the existing heart tissue, and before long, they begin beating in sync with the existing heart cells. On today’s episode, Dr. Murray discusses a range of fascinating topics including environmental and microbiome-dependent effects on the heart and provides an in-depth explanation of the science behind heart disease, damage, and repair.
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Richard Jacobs: Hello. This is Richard Jacobs with the future tech and future tech health podcast. I have Dr. Charles Murray, Chuck Murray. Dr. Murray is a cardiovascular pathologist. Clinical interest span: make heart disease, cardiac transplantation, Atherosclerosis heart failure, cardiomyopathy, the alveolar disease, Atherosclerotic vascular disease. Dr. Murray, thanks for coming. How are you doing today?
Dr. Charles E. Murray: I’m doing well. Thanks for having me.
Richard Jacobs: Tell me in addition to the normal heart doctor work what’s your research about? We’ll start with that.
Dr. Charles E. Murray: Yeah. So I’m a stem cell guy these days and we’re really quite interested in harnessing the power of stem cells to regenerate the human heart. And so my laboratory studies heart disease and various manifestations and we’re gearing towards clinical trials soon where we hope to be able to take some of the first shots on goal to actually grow back new human heart muscle, or as we call it, to re mascularize the heart.
Richard Jacobs: So this is a muscle that gets compromised during a heart attack?
Dr. Charles E. Murray: That’s right. So the heart is the least regenerative organ in the human body, maybe fighting for with the brain for that title. But so when a person loses heart muscle cells, like in a heart attack where you block off an artery and a chunk of the wall dies off, they never grow back. So instead what happens is you’re left with a scar tissue that doesn’t beat and people go on to get heart failure. So a heart failure in most cases is a classic disease and cellular deficiency. Our thought is, since we can now grow essentially unlimited amounts of human heart muscle from stem cells, let’s see if we can transplant these heart muscle cells back into the wall of the injured heart and re mascularize it.
Richard Jacobs: Any insights into why the heart will regrow when other tissues will?
Dr. Charles E. Murray: It’s such an interesting question. In lower vertebrates, like in amphibians, for example, fish, they can regenerate their hearts throughout their life. But in mammals, we can regenerate our heart for a little bit after birth, and then that’s fairly quickly lost. And it’s a big mystery why that is? An interesting paper just came out in Science magazine that suggested that evolutionarily we lost our ability to regenerate the heart about the time we, mammals became committed to regulating our own body temperatures and that the trigger for that was thyroid hormone. So, Huh. You know, let’s see how that holds up, but it’s a very interesting idea.
Richard Jacobs: Have you assumed, how have you tested this idea? You have, you tried like a heart in a dish that you’ve kept beating or a series of cells and is this, you’ve kept beating and you’ve cultured extra muscle cell and put it in the dish and see if it starts to beat and then beat in time with the existing cells?
Dr. Charles E. Murray: Yeah. Yeah. It’s stuff very much along with those mice. We are not, just to be clear to the listeners, we’re not trying to grow whole hearts in a dish. Some people are doing that. We’re shooting for things a little closer term where we, but it all starts with the stem cells. We grow them up in large quantities and then we trigger them to become more specialized or to differentiate and we can direct them down all kinds of faiths. But the one we’re particularly interested in is heart muscle. And so now we can grow dishes and dishes or even that and that of beating human heart muscle cells in the laboratory. And once you have those, that’s what we consider like seed material to replant into the wall of the injured heart. So that takes us then from the bench research into laboratory animals. And we’ve been working our way in learning the rules of how to grow new heart tissue in laboratory animals for some time. And getting to the point where we’re thinking it’s time to take a, a shot on goal, as I’ve said, for human patients.
Richard Jacobs: Have you tried to, so when you implant the cells, how do you assimilate them into the existing heart? Do you, you know, I’ve heard that there are patches, yeah. Essentially graphs like structures. How do you assimilate them?
Dr. Charles E. Murray: So we’ve tried about everything and what we’re going back to is what we started with, which is to just, it’s pretty simple. We take the cells in culture, we disperse them so that they’re mostly single cells, like a slurry of single cells. Use it in some cases and needle and syringe and just stick that into the region of injury and the tissue surrounding it and literally squirt a little clump of cells, kind of like planting on the garden bed and you put them in an array-like pattern and let them do their thing. And here’s where we get the break from mother nature because these cells are really smart. They’re smarter than I am, that’s for sure. And they are able, they know what to do in this environment. They start to divide, they reach out and connect to each other and they connect to the existing heart tissue on either side as you know, the normal regions around the injured zone. And they start to beat in synchrony after a little while and it’s really quite cool. So that’s the basis of it. We’ve tried patches, we’ve tried particles, we’ve tried this and that, but the thing that seems to work best right now is just injecting the cells into the wall of the heart. And then for our first clinical trials, we won’t do this with a needle and syringe. We’ll use a catheter that’s got a needle at the end of it so that we can just go into a standard cardiac catheterization lab to deliver the cells.
Richard Jacobs: What’s happened when you’ve tried to do patches and particles and things like that? What we’ll be able to happen?
Dr. Charles E. Murray: Well we were, we were quite big on this notion of the engineer. In this when you take it up into higher-order things where it’s not just cell therapy, if you will, that’s called tissue engineering. And so we built these pieces of the three-dimensional human heart muscle in the laboratory and they’re just fantastic to watch rich because you couldn’t, you can see these guys beating with your naked eye. You can hook them up a little force transducer and put them in the cardio gym and make them, you know, make them work and see how strong they get, that sort of thing and so we were really excited about it. And then we put them onto the surface of the heart. So putting it on the, if and people call this the patch approach, so you put it on the surface and you typically try to span all the way across the injury region. So it’s, it spans from one normal region to the other normal region. And under the microscope, it looks pretty good. You get this big chunk of the new human heart muscle that is, you know, equal to a large fraction of the volume that you lost. And so as a pathologist who looked through a microscope, it looks pretty good. The problem is when you start to look at its function, and what we found was that it doesn’t connect up with the rest of the heart muscle. When we do that, it’s separated by abandon scar tissue and it doesn’t get the electrical signal to beat. So it follows its own drummer instead. And in, in for example, in a rat heart that normally might be beating 300 or 350 beats a minute. The human heart muscle is sitting there and beating at 40 beats a minute, quite lazy, and it doesn’t have nearly the beneficial impact as when you put it into the wall where it can follow the pace and beat in six.
Richard Jacobs: Okay. A quick question, stepping back the stem cells. You’re using heart cells that you’ve induced pluripotency in and made them heart stem cells, are they skin cells that you’re inducing pluripotency in and taking them down the heart cell path?
Dr. Charles E. Murray: So these are cells that, we can do this two ways. We can take cells that are prepotent, to begin with, like embryonic stem cells or we can take cells that have, were like skin cells or blood cells, something like that, and have been reprogrammed to the most potent type of stem cells. And those are called the induced pluripotent stem cells. Either of those work quite well and we know the recipes now basically for making human heart muscle from them. So that’s quite efficient.
Richard Jacobs: Any difference in, you know, your choice of starting cell? Zeros of performance and integration?
Dr. Charles E. Murray: Yeah, I think that embryonic stem cell and a reprogrammed induced pluripotent stem cell are essential. You know, they’re like kissing cousins. They’re really almost the same thing. And, and so they, in turn, once you turn them into heart muscle, the effects are pretty much indistinguishable.
Richard Jacobs: Is there a heart having stem cells, you know, natural stem cells in it. And if so, what do they do? You know, where does it happen?
Dr. Charles E. Murray: What a great question that is. That’s been fairly controversial in our field for sure. Oh, the better part of 20 years now. I think it’s finally sorted. So I can just tell people the bottom line for this and the, and that is that there is not a muscle forming stem cell that lives in the heart. And that is part of the root. You know, the root cause for why the heart is so bad at regeneration. People thought there were for a long, for a long time, but then, the definitive studies have come out in the last few years and in the answers, clearly, no there, there isn’t done. There are stem cells in the heart that can give rise to any blood vessels, new connective tissue cells and things like that which is kind of like the heart’s infrastructure but in order. But in terms of replacing the muscle cell, which is the key population, nada.
Richard Jacobs: When someone has a heart attack, can we looked at the morphology of the hard tissue that dies? Does it tend to take certain shapes and they have certain with some, does it goes through the whole muscle itself or does it sit on the outer surface of the muscle, the inner surface? Is there anything interesting that you learned there?
Dr. Charles E. Murray: Yeah. And so this is something that we know the answer to really well because it’s been very well studied in experimental animals and in human beings. There are several things that determine the size and the shape of the tissue when that’s lost during a heart attack. The first thing is just that the anatomy of the coronary vasculature and wherever the blood clot happens to form in terms of the tree branch structure. And so the bigger the amount of tissue that was sped by that vessel where wherever it becomes occluded, the greater the amount of heart muscle you’re going to lose. So that’s number one. And that’s sort of is the lateral or the circumferential extent of the heart attack and the next thing is time. The longer the artery stays occluded, the longer, the more depth of heart muscle that happens. So time is heart muscle. And this is why we always want to get people to come in as quickly as possible after they have chest pain because we can open their artery back up and save the muscle. Now that the muscle doesn’t die off just Willy Nellie, there’s a very systematic progression and the in a wavefront manner. So it starts at the innermost layers of the heart muscle and with time marches its way out through the wall, towards the outside border. And so the lateral boundaries are vascular and what we call Trans mural or across the wall boundaries are time-dependent.
Richard Jacobs: Hm. Interesting. Um, anything about the nature of the muscle death, you know, once it’s dead, it’s dead or is there anything you’ve observed about as you said, it’s a, it kind of happens in a way you from inside out. Any peculiar or interesting things you’ve noticed when you looked at, you know, a dead region?
Dr. Charles E. Murray: Well, one of the interesting things is it doesn’t stay dead for very long. People always think about a heart attack as being a region of dead tissue, but the dead muscle is only there for a matter of weeks to maybe a month and what happens is there’s a big wound healing response. And so your white blood cells come in and there’s a special class of white blood cell that’s called the macrophage. And they literally gobble up the dead heart muscle. And then new tissue grows in to take its place and it has a lot of blood vessels and a lot of connective tissue cells. And the problem is its default pattern is just going on and form scar tissue. So we see this really dynamic waves of the injury followed by inflammation followed by repair. That, unfortunately, ends up like scar tissue. And so part of what we’re doing is we tinker around with heart attacks is can we change this default pattern is it possible to reeducate the cells so that we end up with something that would be more useful, like growing back new muscle for example.
Richard Jacobs: What do you think is the reason for scar tissue? The bodies are revealing the old dead tissue, but it’s just the scar tissue. Is there any particular more followed you to the scar tissue? Is it doing it to keep the structural integrity of the area or is there, do you see if there’s any other possible reason to have it? May it be like a backup system? I don’t know. That brings more vascularity in case something happens again to an area, I don’t know.
Dr. Charles E. Murray: Yeah, it’s really good questions. And sometimes, you know, the why questions are among the hardest ones to answer. The scar serves a function as a bridge between the healthy regions. And so it holds the heart together while the rest of, you know, the surviving tissue does the extra increased work. And so it, it, you know, we know that if you stop scar tissue formation experimentally, for example, the drugs or do various genetic tricks and that sort of thing, it’s disastrous because the dead tissue never gets eaten and then it breaks down in tears and the heart ruptures. And so the scar tissue, certainly we’re better off with it than without it. What if that’s our only two choices, the question we’re asking is really, can we be smarter than that and improve on nature’s pathway, which isn’t that great, especially when you see how beautifully hearts regenerate in news, for example.
Richard Jacobs: So what happens when you’re seeding the heart with these new stem cells, you seed all throughout the dead area. You seeded the edges slowly and then move in where it’s like, and at what point do you do it? Do you do it after the scar tissue has been formed or before it’s the dead tissue?
Dr. Charles E. Murray: More really good questions are very pragmatic. But let’s talk about where first and then we’ll come to the, when. The where are we right now we sort of do it like a little garden bed where we plant and we give little injections of saying a hundred microliters each, just squirt, squirt, squirt, squirt, and alignment. Then move over in another little line and that sort of thing. And then, and we always go, not only in the injured region but into the border zones as well because we find that that’s really dynamic and it’s keeping a happy, healthy border zone is quite important. So that’s the where and then the when is, um, is not completely we’d nailed down for in terms of, how best to treat human beings. What we find in experimental animals is that it’s, we get more bang for our buck if we go in say a couple of weeks after a heart attack before the heart has all scarred up and changed its shape and that sort of thing. That’s when we have the most benefit to a pump function. For patients, we probably won’t start that soon after a heart attack just because we’ll probably start in patients with advanced heart failure just from a safety standpoint. Those are the patients, you know, we’re also worried about potential side effects and things like that. And so we want to start in the patients in whom we think we can do the least harm and then work toward the patients where we think we could do the greatest benefit.
Richard Jacobs: Well, it sounds like you need time for the rubber should be cleared away for the jug material to be naturally taken away by the body.
Dr. Charles E. Murray: That’s right. That’s a great observation, if you put it into the, if we put the cells into the dead tissue when all that inflammation is going on, most of them are killed as bystanders.
Richard Jacobs: Yeah. And then before the story happens, that’s when the seed spot is to put in the stem cells. Hmm. Interesting and again if you have an area, I’m just going to make it up like around one-centimeter area that’s, you know, that was dead and is now cleared away. What’s there before the scar tissue warms, you said there’s inflammation, and there’ll be removal, the dead stuff. Have you observed what’s there right before the scar tissue forms? Is it just an out of undifferentiated cells that are sitting there and then they differentiate the scar tissue? Or what’s the intermediate stage look like?
Dr. Charles E. Murray: That’s also really an interesting question. There is this tissue that is an intermediate tissue of wound repair and the apologists call it granulation tissue and it’s this very vigorously proliferating if cells are dividing as fast as in a malignant tumor for example. So it’s really crazy and some, because the average heart attack kills off maybe a billion heart muscle cells. And so there’s a lot of cell division that has to take place in order to just repopulate this defect. And some you, you see a lot of cell division, you see the growth of things with blood vessel cells. You see the connective tissue cells, fiberglass, they’re proliferating like crazy as well. And what happens is that gradually then starts to undergo waves of self-depths so that, uh, the Oh, many of the cells just start to die off. And you’re left with much more of a plain old connective tissue, which is really what scar tissue is, is that the collapsed connective tissue scaffold of what used to be tissue. And so it isn’t, these aren’t bright lights and boundaries. Its sort of a stayed in and stayed out phenomenon.
Richard Jacobs: Would you, so you’ve seen that cells proliferated in the area, but do they die or they just then become their final state of scar tissue? Is it still living the whole time?
Dr. Charles E. Murray: So they proliferate, they migrate like crazy. They crawl in from the outside and crawl in to repopulate the injured zone. And then after doing that for a month or so they start to die and about 75% of the cells in the front from the, what I call the granulation tissue stage, which is the height of wound repair. From there, if you compare cell content to the content of a scar, it’s, it’s lost about 75% of the cells and that’s just always been nature’s way of wound healing that anytime we form a scar anywhere in the body, it kind of goes through the same dynamics.
Richard Jacobs: How long does it take for the initial cleaning of the dead cells to happen? On average, how long does it take for the proliferation stage and then the final know scar tissue scarring stage?
Dr. Charles E. Murray: Yeah. Well, the whole process start to finish takes about two months. Any human being, the bigger the heart, the longer it takes. So a mouse can heal much faster than a human being as you might imagine. But then what we find is in the mouse, there are these discrete ways cause it’s this tiny little bit of tissue. So first it’s all dead and inflamed and then it’s all in this granulation tape, tissue stage and then it goes very quickly to scar, just bang bang back. In big hearts, what we find is that these windows overlap and so that we can have scares that are, you know, the mature scar that’s formed on the outside. But on the inside of the wound, they’re still dead muscle that hasn’t been eaten yet. And so it’s these areas of dead tissue heal sort of from the outside in. And so in human beings, you see all the stages of wound repair simultaneously.
Richard Jacobs: What about the clearing of dead tissue? So it sounds like the yes happens inside out. The repair happens outside in.
Dr. Charles E. Murray: That’s an important way to look at it. Yeah. I’m sorry I interrupted you. Go ahead with your question, please.
Richard Jacobs: The scarification happens outside in, but what about the removal of the dead tissue? Is that directional?
Dr. Charles E. Murray: That is outside again as well.
Richard Jacobs: Hmm.
Dr. Charles E. Murray: A lot of them, the window have to crawl in from the outside where the blood vessels are healthy and they can get out of them and then they start gobbling up the dead muscle, but more typically from the outside.
Richard Jacobs: So when you’re poking in these cells, you’d want to poke and go to the deepest depths first and seed from the bottom up. Or do you seed from the top down?
Dr. Charles E. Murray: You know, we’re not that sophisticated yet to know that it’s, it’s interesting that your future tech is already talking futuristically. So we are just glad to sort of distribute them broadly. What, one of the things we find is a lot of the cells that, you know, they’ve not evolved to be injected and that sort of thing like this. And so we end up losing a lot of them. And so there’s a big chunk that had the die-off and then they grow back afterward to some extent. So they partly repopulate the numbers that are lost and we’d love to be able to get rid of this problem of cell death because we think we could get better re masculinization and we wouldn’t have to grow so many cells, to begin with, either. That would be, you know, so it would really reduce the cost of goods once we get into the clinic.
Richard Jacobs: What happens to the cells that you try to implant and you poke in, that don’t successfully take, what did they become? Are they cleared away? Do they become scar tissue? Then what happens?
Dr. Charles E. Murray: Well, another good question. For the most part, they die off and then the white blood cells just gobble them up. Like, you know, just as though they were regular cells from the heart attack itself. So they get eaten by these specialized white blood cells. One of the things that we’re concerned about is when we get these cell from the catheter, um, are they going to be distributed elsewhere in the body? and we people have looked at this and if you look short term, like within an hour or two afterward, they do go to other places, particularly the lungs where, cause some of them sneak out through the bloodstream and then they’re filtered at the lungs, which is, you know, once they go into the veins of the heart, the next filter bed is the lung. And, but fortunately, we don’t end up with beating lungs. The cells seem unhappy there and they simply die off.
Richard Jacobs: Yeah. I mean you wouldn’t want him to competing orchestras, the different parts of the body.
Dr. Charles E. Murray: There’s like your heart’s growing in your lungs, you know, whatever. No. So we, this is something we’re definitely keeping an eye out for, but so this is another area where it seems like we’re getting a break from nature but the cells just don’t like being anywhere but in the heart.
Richard Jacobs: What about studying self-Estella’s signaling? There must be a lot of very specific signaling that goes on and the existing heart tissue that tells the new cells, all right, grow, don’t grow, go here, don’t go here. Now start beating in times of the master signal. Have you been able to isolate any of these signals? Maybe there, I don’t know, given off by exosomes from the existing cells or mechanical, you know, mechanically there vibrating the membranes of the new cells in a certain way. I mean, have you figured out anything there?
Dr. Charles E. Murray: That’s a hot area, that’s a very actively being researched in the lab right now. One of the, to just take a step back and then I’ll round up back to this. One of the really holy grills in stem cell science right now is how to get our stem cell derivatives to mature, to be more like adult cells. So what happens with, we can make most of the cells in the human body now, but they’re basically at early fetal stages when they in the dish. So the trick is, and of course, as you can imagine, the cells change a lot in our bodies from the time when we were developing in the uterus to the time when we’re adults for example. And that’s a mystery of developmental biology that nobody has ever really studied. But when we transplant the cells into the heart, they mature to be a beautiful adult-like cell. And so there’s, it tells us there’s some secret sauce about being in their normal environment that is driving this maturation. So we’re trying to systematically take this apart and figure out what it is. It’s making it work. The first thing seems to be electricity when the cells, you know, the heart is, of course, an electric organ and when you transplant the cells in and they start to connect, the grafted cells start to connect with the surviving cells from the host heart. One of the first things they do is make these specialized junctions for electricity flow from one cell to the next. And so we think the electrical pacing and that sort of thing is a big part of growing up. Another thing is the mechanical environment because the heart is obviously very mechanically active organ. And the more mechanical strain they’re just put on these cells as it’s kind of like going to the gym and they start to work out, they start to train and they start to build the muscle-up. The third thing I’ll say, and I won’t just blather on and on, but it’s very interesting that their diet changes when they’re in cell culture, they are principally eating sugar. Just like the fetal heart is inside the uterus. And so that mostly is a carbohydrate-based diet. But when you, we were once born, of course, we switched to nursing and it’s principally fat in breast milk. That becomes the fuel. So for the rest of its life, the heart likes to eat mostly fat. And so in your heart and my heart, it’s burning about 80% of what it’s burning right now is fat and we’ve found that changing the cells diet makes a huge difference. And so a diet and then some of the hormones that regulate metabolism, like thyroid hormone and Cortisol and things like that turn out to be really important communications as well. So some of the signals are local in the heart itself and some of the signals are systemic and they come through the bloodstream.
Richard Jacobs: Wow. That’s really interesting.
Dr. Charles E. Murray: Isn’t it interesting? And there are all kinds of exosomes as you mentioned. Yep. I’m sure that’s going on. We haven’t drilled into that yet, but it, they seem all kinds of cells are talking to each other through these little membrane-bound bits that they pass from one cell to the next little information packets. And I’m sure that’s going on also. It’s just trying, you know, trying to get a few things done rather than distract yourself like a kid in a candy store.
Richard Jacobs: That’s crazy.
Dr. Charles E. Murray: Oh, that’s right. I mean, we’re, you know, we’re learning so many things and there are all these tools that are available to us to explore cells in ways you never imagined.
Richard Jacobs: Yeah, no, that’s amazing. Any evidence of microbes or viruses or fungi or any microbiome type things in the heart, in or around it? Any observations there?
Dr. Charles E. Murray: Well, so there are two ways to look at that. The one that we were most worried about in terms of developing a therapy is how you make sure that your cells are clean enough to be transplantable. And for that, there are standardized assays that commercial laboratories will conduct and they look for every virus under the sun. All we do, all kinds of culture for bacteria and fungi and that sort of thing. And we’d just gotten back results from a huge panel of viruses that we’re looking at what we’ve tested for. I spent $150,000 to get this done and our cells came back clean. We were biting our nails a little bit the fall, but while that testing was out. So we’re, you know, check, check, check and all those boxes. There’s another conversation that’s going on all the time in our bodies, which is from the microbiome. You know we live commensurately with lots of other organisms on and in us and our gut is having all kinds of influences on what, you know, how our food is processed and what gets into our bloodstream and that certain thing. And we’re just beginning to understand how that works. We know for example though that in terms of the upstream cause of heart disease, which is blood vessel disease or Atherosclerosis, the microbiome seems to play a big role in promoting that. And so it would hardly be a surprise to find that there were microbiome dependent effects that were happening as well. And so I think it goes both ways. We’re going to try and make sure we don’t have an effect on the host. We don’t want a transplant in new microorganisms, but I think our hosts will probably have an influence on the cells after we put them in.
Richard Jacobs: Okay. Well natively do you think, and has anyone observed that there is a micro-biome on the heart, you know, that’s just the gut, but is there a localized native microbiome you think of the heart as it is, even any indications to season it?
Dr. Charles E. Murray: The heart, like most internal organs we think of as a sterile environment. So we don’t know of any microorganisms that are living in the heart, the brain, the kidneys, you know, outside the, outside the inside or outside the Lumen of the intestine. Right. So our intestines are sort of like the outside world in a way, just like our skin is because they’re just like an inside out tube. But once you get past that, I don’t think there is a big micro-biome for heart or truly internal organs.
Richard Jacobs: Okay. And that was a weird question.
Dr. Charles E. Murray: I think it was an interesting question, but I mean there are so many things where we do have them in our, so in our gastrointestinal tract, of course in our urogenital tract and our reproductive tract, all those kinds of things which ultimately are connected to the outside world, we’re learning all of those things. You have microbiomes and that’s a very important part of human health. But things for truly internal organs so far, we don’t know about the microbiome is associated with them, but you know what, stay tuned. Right.
Richard Jacobs: And I was also thinking about the heart, you know, it’s an interesting organ because of its filters so much blood over its life. What did you notice about the blood facing cells in the heart versus the ones that just compose the structure of the heart? I would bet that there are a lot of differences there. You know, the inside of the chambers, inside surface versus the rest of the heart structure.
Dr. Charles E. Murray: Yeah. Well, the internal lining of the heart is actually not even made up of muscles. I mean we think of the heart as just a big, big thing of muscle, but it’s really got extra parts in it as well. And so the inside lining of the heart is much more like a blood vessel so that it’s got a specialized cell that lines, it’s called the endothelium, which is the same kind of cell basically that lines the inside of our blood vessels all over the body and endothelium is specialized to help promote blood flow, to not clot and to be able to do specific things in response to injury and that sort of thing. So the inside of the heart, it’s got only one cell layer thick, but it’s absolutely pivotal in terms of its function. And then as you move across the heart, the cells that are on the innermost layer are pretty different from the cells that are on the outer most layer, just going across the muscle layer and their electrical properties are different and their mechanical properties are different. For example, the electrical activity goes, it depolarizes from the inside to the out. But then it repolarizes from the outside to in. And so that’s very interesting. And the cells that are on the innermost layer of the heart are actually stronger than the cells on the outer layer of the heart because they’re dealing with the highest pressure. Cause there’s a big, there’s a lot of pressure inside the heart or the pump is running. But outside through the outermost layers of pressure is not much different than it is in the longer anything else in the chest. And so as you go from inside to out the cells go from stronger to weaker as well. So lots of differences across the wall.
Richard Jacobs: It is maybe a silly question, but the heart probably has its own vascularization that completely separates from the blood that flows through it. It wouldn’t be dependent upon the blood flows through it.
Dr. Charles E. Murray: There is nothing wrong with that question. That’s an insightful question. And absolutely the heart has a, a very rich circulation that is that it doesn’t get from its own chamber. It gets from its own arterial supply and those are the coronary arteries. So the first branch of the, they are the big blood vessel, right? That comes out of the heart and distributes the blood to the rest of the body. The first thing to get fed is the heart. So the heart beats itself first and then goes on to feed the rest of the body and those first branches are called the coronary arteries because they make a crown-like structure over the surface of the heart. And it’s a problem organ in the body as well. Incredible capillary density.
Richard Jacobs: Hmm. So the coronary arteries would have probably the highest pressure. The richest blood?
Dr. Charles E. Murray: Well not so much high pressure because the pressure is pretty much the same throughout the arterial tree, but it’s the first thing to get highly oxygenated. And the heart is really good at it. It extracts like every last molecule off of hemoglobin. It’s one of the most efficient organs in the entire human body at pulling oxygen. So its extraction is really very efficient.
Richard Jacobs: Hmm. So in terms of a vascularization, you know, we talked about how the new tissue that you’d, the new cells that you’d plant, how they hook up with the rest of the heart. What about the vascularization? What does that look like in scarred tissue versus once the tissue regrowth’s properly?
Dr. Charles E. Murray: Yeah, that’s also a very key question. So when a person has a heart attack, it doesn’t just kill the muscle cells, it kills the infrastructure of the tissue as well. And so it kills the blood vessels and it kills the connective tissue as well. They’re not as sensitive to it as the heart muscle cells are, but they do die off as well. And so not only one of the mantras we have in the laboratory is that we need to revascularize in order to re-mascularize that we’re never going to get good functioning heart muscle if we don’t get good blood soft. And so we were paying a lot of attention to how these blood vessels form in our graphs right now. And then we’re trying to find ways to enhance the response of what’s really the coronary circulation to make sure that we grow better capital areas and that sort of thing. One of the challenges at the moment it’s pretty easy to grow the little vessels, the capillaries, and the big vessels are the ones that we really need to get now. Those of what we call the large conducting vessels. Because you could imagine if you had a big bottleneck, let’s say on an interstate. The city Department of Transportation responded by building a bunch of more surface streets that would not make any sense. What you really need to do is widen the artery, right? And so that’s, in the body is very good at making these capillaries. It’s not very good at making new arteries. And so that’s one of the challenges that we’re having these sort of like a 2.0, 3.0 improvements to regeneration is not just putting back new muscle cells but actually improving the vascular infrastructure as well. Because I think we’ll get a lot more bang for our buck that way.
Richard Jacobs: Hmm. Well, is this complicated? I know you know better than me.
Dr. Charles E. Murray: It is complicated. And yet, you know, we look at it as job security, that it’s kind of like, you know, it’s kind of like making developmental biology happen all over again in an adult organism but doing it in a way that could be medically tremendously useful. I mean, this is, you know, we’re talking about what’s the number one cause of death in the whole world, right? So heart failure, has for a couple of decades been the biggest cause of death and not in just the developed world, but really worldwide now. So including India and China and things like that and so it’s complicated but it’s also time to really start doing this. And, well, you know how these things go. Ritual will screw some things up at first. We’ll have the right ideas and we’ll do them in the wrong order and we’ll just have some of the wrong ideas as well. And we’re learning as we go, but I think what we have in the middle of right now, is kind of a slow revolution in the practice of medicine where we’re going to start to see cells actually being used as medicines themselves where they’re able to rebuild the human body.
Richard Jacobs: Okay. I can hear you are very excited about it, which is great. So what are some of the important milestones you’ve hit recently and what are some milestones you’re going for the next couple of years that would make you super happy if you had them?
Dr. Charles E. Murray: So the biggest thing that we hit recently was what we call efficacy, preclinical efficacy. What do I mean by that? And we spent a lot of time demonstrating that we could grow new heart muscle and looking at it under the microscope, that sort of thing. But more recently we drill down deeply on a function that, you know, you could call it the, so what question? Yeah, you can make muscles that look good under the microscope. So what, and what we found is that this new muscle will beat in synchrony with the surrounding muscles. So it hooked up and it’s going at the same time when that was a prerequisite for really regenerative healing. And then when we looked at the impact on the overall ability of the heart pump, we just had our socks blown off. We looked at this thing called ejection fraction, which is how much does the heart squeeze out of the chamber with each bead. And normally if it’s, say 65% and we gave these animals experimental heart attacks and that dropped that to 40%. So they were well on their way to heart failure. And if you don’t intervene, it stays pretty much at 40% for the rest of the animal’s life or it gets worse. In the animals that we put human heart muscle in, we were able to get their ejection fractions back up into the 60s again. And I’ve never seen, you know, I’ve been in heart research since 84 and I have never seen anything that has had a disability to restore mechanical function to the heart. So that was a big breakthrough in terms of demonstrating the, it proves the concept that you know, and if we can do this with human cells, say in a mocap monkey, we should surely be able to do this putting human cells into a human. In terms of what lies ahead now, what are the milestones that we need to make, there are several, we’ve got to be able to produce ourselves at pharmaceutical quality reproducibly, in a manner that was, that will assuage concerns in the food and Drug Administration or European regulatory agencies or wherever it is that we want to market this. So we’re close on that. I think we’ll get there this year. The other thing is that we haven’t talked about this yet, but the cells have unexpected toxicity that when we put them in, they make the heartbeat irregular for several weeks afterward. It can make the heart race really fast. And that turns out to be sort of a power struggle between our adolescent cells and the adult’s heart muscle. And so we’re trying to learn, you know, why is it that it, it makes the heart race so rapidly. And so over the next 12 months, probably the biggest thing I’ll be working on is how in the heck do we keep this from happening? and I think it really relates to the fact that the cells are immature and if we can get them to grow up a little in the dish before we put them in someone’s mother, I think their chances are going to be, the chances of something going wrong will be significantly reduced.
Richard Jacobs: Is there a critical mass of cells that you put in with the struggle happens or if you put in just a few, that does not happen?
Dr. Charles E. Murray: That’s a good question. There is a dose-dependency to it. I mean, almost every phenomenon in biology has what we call a dose-response curve and at the moment we’re trying to see if there is a sort of a goldilocks sweet spot where we can put in few enough cells that they still are benefiting function but enough cells, excuse me, I said that backward. Enough cells that they’re benefiting function but few enough that they don’t cause rhythm disturbances and that’s active investigation right now.
Richard Jacobs: Hmm. Yeah. Very interesting. Okay. What’s the best way for listeners, time to time, to find out more, maybe read papers you put out, look at the lab, see, you know, interact, ask questions.
Dr. Charles E. Murray: Yeah. There’s, I mean for people who are experts in the field, of course, I’m going to look at our scientific papers and seeing what are most recent ones are, is probably the best way to get a census of the state of the art. And we’ve written a couple of recent review articles that summarize this for people who are interested in the sort of the more patient-centered aspects of a couple of resources. I gave a recent Tedx talk on this and so there’s a 15 minutes or a summary of what our, you know, what my personal scientific trajectory has been in this crazy field and so if somebody has got 15 minutes of their life to waste, they could go check that out on the Ted website. The international society for stem cell research has a very good site for patients. It’s called a closer look at stem cells. And I would suggest people check that out as well because we’ve got sort of one-page white papers on various different diseases that include heart disease, but it also includes Parkinson’s and Alzheimer’s and arthritis and diabetes and lots of other diseases as well that people are interested in. And people could take a look at that. And those have nice summaries written at the level of the patient, about what the current state of the art is in cell replacement therapies for all these different diseases.
Richard Jacobs: Okay. Well, very good. This has been the awesome call. Very interesting.
Dr. Charles E. Murray: You have terrific questions.
Richard Jacobs: Well, thank you.
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