Oct 21, 2021
This month on Episode 29 of Discover CircRes, host Cynthia St. Hilaire highlights four original research articles featured in the September 17th and October 1st issues of Circulation Research. This episode also features conversations with BCVS Outstanding Early Career Investigator Award finalists, Dr Jiangbin Wu from the University of Rochester, Dr Chen Gao from UCLA, and Dr Chris Toepfer from Oxford University.
Article highlights:
Raftrey, et al. Dach1 Extends Arteries and Is Cardioprotective
Zhang, et al. Blood Inflammatory Exosomes and Stroke Outcome
Joyce, et al. Cardiovascular Health and Epigenetic Age
Liu, et al. Wls Suppresses Fibrosis in Heart Regeneration
Cindy St. Hilaire: Hi,
and welcome to Discover CircRes, the podcast of the American Heart
Association's journal, Circulation Research. I'm your host, Dr
Cindy St. Hilaire from the Vascular Medicine Institute at the
University of Pittsburgh. And today, I'll be highlighting articles
presented in our September 17th and October 1st issues of
Circulation Research. I also am going to speak with the BCVS
Outstanding Early Career Investigator Award finalists, Dr Jiangbin
Wu from the University of Rochester, Dr Chen Gao from UCLA, and Dr
Chris Toepfer from Oxford University.
Cindy St. Hilaire: The first article I want to share is titled, Dach1 Extends Artery Networks and Protects Against Cardiac Injury. The first author is Brian Raftrey, and the corresponding author is Kristy Red-Horse from Stanford University. Coronary artery disease occurs when blood vessels supplying the heart develop atherosclerotic plaques that limit blood flow, which prevents oxygen and nutrients from reaching the cardiac tissue and often leads to a heart attack or cardiac arrest. The suggested strategy for treating coronary artery disease is to promote the growth of new blood vessels to compensate for the dysfunctional ones. Several factors are known to control coronary blood vessel development, including the transcription factor, DACH1. In mice lacking DACH1, embryonic coronary artery development is stunted. But whether increasing DACH1 protein levels boosts heart vessel development, and whether this would work in mirroring coronary arteries, were unanswered questions.
Cindy St. Hilaire: This group engineered inducible gain-of-function DACH1 mice and found that DACH1 over expression in the embryo boosted coronary artery development. The team then used the same model to induce DACH1 in adult mice for six weeks. While there was no apparent differences in the artery growth between the animals and the controls under normal conditions, after myocardial infarction, the mice over expressing DACH1 had better recovery and survival with increased artery growth and heart function. The results paved the way for studying the mechanisms of DACH1-mediated protection, and how they might be leveraged as potential coronary artery disease treatments.
Cindy St. Hilaire: The second article I want to share is titled Circulating Pro-Inflammatory Exosomes Worsen Stroke Outcomes in Aging. The first author is Hongxia Zhang, and the corresponding author is Kunlin Jin from University of North Texas Health Science Center. Aging is associated with declining tissue function and an assortment of health issues. But in rodents at least, certain factors, including the plasma of youthful animals and the exosomes of stem cells, can have rejuvenating effects on old animals. Exosomes are small membrane-bound particles containing cellular contents that circulate in the blood after they're released from cells. This group has shown that as rats age, the animals' serum exosomes accumulate pro-inflammatory mediators, such as C3a and C3b.
Cindy St. Hilaire: When these aged rats were subjected to stroke, and then injected with serum exosomes isolated from either old or young rats, those receiving youthful exosomes fared much better in terms of infarct size and sensory motor deficits, while those receiving aged exosomes fared worse. The team went on to show that injected exosomes accumulate at the site of stroke injury, but those from old donors caused more neuronal damage, as seen by reduced synaptic function. Preventing C3a activity on microglia reversed the effects of the old exosomes and improved stroke outcome, suggesting that such modulation of inflammatory molecules might be a treatment strategy for stroke.
Cindy St. Hilaire: The next article I want to share is titled Epigenetic Age Acceleration Reflects Long-Term Cardiovascular Health. The first author is Brian Joyce, and the corresponding author is Donald Lloyd-Jones. And they're from Northwestern University. DNA methylation is an epigenetic modification that regulates gene transcription. Studies of young and old individuals have shown that at certain locations in the genome, methylation status is highly correlated with age. These methylation patterns are also linked to measures of cardiovascular health, including blood pressure, cholesterol level and body mass index. This suggests that if a person has particularly good or particularly poor cardiovascular health, their DNA may appear younger or older than the individual's actual age.
Cindy St. Hilaire: This group tested the hypothesis that people with poor cardiovascular health exhibit methylation changes more commonly found in elderly individuals than those with good cardiovascular health. And if so, DNA methylation patterns might be useful for predicting future cardiovascular risk.
Cindy St. Hilaire: The team examined DNA methylation of over a thousand individuals enrolled in a prospective heart health cohort, testing them around age 40 and then again at around age 45. Changes in methylation status were then compared to individuals' cardiovascular health scores over a longer period. Sure enough, faster epigenetic changes did correlate with poor cardiovascular health later in life. Data from the second cohort of individuals supported the initial findings. This study indicates that DNA methylation status may be an early biomarker that signals cardiovascular issues, and may therefore allow for prompt implementation of treatment and prevention strategies.
Cindy St. Hilaire: The last article I want to share is titled, Yap Promotes Noncanonical Wnt Signaling from Cardiomyocytes for Heart Regeneration. The first author is Shijie Liu, and the corresponding author is James Martin. And they're from Baylor College of Medicine. After a heart attack, cardiomyocytes are destroyed and replaced with a fibrotic scar that interferes with the contractile function of the heart. While adult mouse and human hearts are similar in this regard, the hearts of newborn mice possess greater regenerative capacity, and this regeneration capacity persists for approximately one week. The transcription factor YAP is known to regulate regenerative processes in neonatal hearts of mice. And its deletion eliminates regeneration, and its over-activation in adult cardiomyocytes reduces fibrosis.
Cindy St. Hilaire: These experiments suggest cardiomyocytes transmit signals to cardiac fibroblasts. Wntless protein regulates the release of Wnt signaling molecules and also is a target of YAP. Mice that lack Wntless in their cardiomyocytes appear to have normal heart development and function. However, their neonatal regenerative capacity was impaired. In the weeks after heart injury, the mice that lack Wntless had reduced heart function, increased scar size and increased numbers of activated cardiac fibroblasts compared with that seen in controls. The study indicates that Wntless is critical to the regeneration of cardiac tissue, and may perhaps be leveraged to minimize scarring after heart attacks.
Cindy St. Hilaire: I'm really excited to have with me today the three finalists of the BCVS Outstanding Early Career Investigator Award. The first person I'm going to be speaking with is Jiangbin Wu, who is a research assistant professor at the Aab Cardiovascular Research Institute at the University of Rochester. Thank you so much for joining me today.
Jiangbin Wu: Thank you.
Cindy St. Hilaire: And congratulations, actually. I know this is a highly competitive award that gets a lot of applications, so congrats on becoming a finalist. Before we get to your abstract, which is related to mitochondria and calcium influx in cardiomyocytes, I was wondering if you could share a bit about yourself. Maybe what your research path was, and what brought you to study cardiomyocytes and the mitochondria that are within them?
Jiangbin Wu: Yeah. Right now, I'm an assitant professor at Cardiovascular Research Institute of University of Rochester. Previous, I was actually studying in the cancer field and also some kind of mitochondria work in some cancer cells. Although when I came to the University of Rochester and I switched to cardiovascular and then we are working on a kind of microRNA[at the initial. The way we screen for these is just by doing the RNA-Seq is target the microRNA. and then we start to study the function of these genes, and found that it's a mitochondria calcium channel regulator.
Cindy St. Hilaire: The title of your abstract is FAM210A Maintains Cardiac Mitochondrial Homeostasis Through Regulating LETM1-Dependent Calcium Efflux. So before we unpack what all those words in the abstract title mean, could you tell me how you ended up focusing on FAM210A? What does this protein do, and why'd you focus on it?
Jiangbin Wu: Yeah. As I mentioned that we just gathered this protein actually is by some kind of chance as a microRNA target. And this protein full name is family with similarity 210 A, actually is a family of proteins. This is just one of them. And the way discover is localized in mitochondria in the membrane. And also, there is some other people's report is in mitochondria. And we want to sort out its function inside the mitochondria and in the cardiac background. So we do some kind of omics or mass spec to get its interlocking interacting proteins. And then we found LETM1. It's a calcium channel inside the mitochondria in the membrane. So we figured out is, this FAM210 protein regulate LETM1 function in calcium, pump calcium is part of the mitochondria matrix. And I think this is a very important, because calcium overload is always happening in the very heart of the cardiomyocytes.
Cindy St. Hilaire: That's a perfect segue, because my next question was really what is the gap in knowledge that your study was trying to address? Were you really focused on just the function of this one protein, or what was the greater goal of this study?
Jiangbin Wu: Actually, the function this protein is the initial step. Our final aim is to use this protein, to over expression this protein in the heart failure patient or in some kind of heart failure models to do the, sort of do the work in some heart failure patients.
Cindy St. Hilaire: Maybe a gene therapy approach, or if there's a pharmacological way to up regulate this protein?
Jiangbin Wu: Yeah, because we've proposed that the self expression of this proteins will reduce the calcium overloading cardiomyocytes, which is a major cause for the cardiomyocytes death in heart failure process. So over expression will reduce this kind of process. And then it will make the cardiomyocytes survival in the failure heart.
Cindy St. Hilaire: That is interesting. I mean, obviously you were using a mouse knockout model, so you know what's driving the expression down in that case. But in humans, what do we know about the regulation of this protein? Is anything known, or any known causes that cause its reduction in expression?
Jiangbin Wu: Actually, we do. Its expression in heart failure is slightly increased in heart failure. So we feel it's a kind of some kind of compensating effect to try to save the heart from failing.
Cindy St. Hilaire: Interesting. It's just not turned on early enough, in that case then.
Jiangbin Wu: Yeah. And for the regulating protein for this one, I think we find microRNA can suppress its expression, but not too many other influences on these regulator proteins.
Cindy St. Hilaire: That is so interesting. So what's next? What are you going to do next on this project?
Jiangbin Wu: Yeah. I think currently, we are just at the start to do some kind of therapeutic effect that use to these proteins. I think we will do more deep in the therapeutic effects for over expression of these genes in... Currently, we are working on mouse models. Maybe in different heart failure models to prove that it's very benefiting to the heart failure patients.
Cindy St. Hilaire: Wonderful. Well, congratulations on an excellent study. Really looking forward to your presentation, which is coming up shortly, and really looking forward to your future research in this field.
Jiangbin Wu: Okay, thank you.
Cindy St. Hilaire: So I also have with me, Dr Chris Toepfer, who's another finalist for the BCVBS outstanding early career investigator award. He's a principal investigator from the University of Oxford, and his abstract is titled, Defining Diverse Disease Pathway Mechanisms Across Thick And Thin Filament, Hypertrophic Cardiomyopathy Variance. So congratulations, Chris, and thank you for joining me today.
Chris Toepfer: Thank you very much. It's great to be here.
Cindy St. Hilaire: Before we start to discuss your abstract, I was wondering if you could just share a little bit about yourself. Maybe your career path, and how you came to study hypertrophic cardiomyopathy?
Chris Toepfer: Yeah, sure. I guess this story gets longer and longer every time somebody asks it,right, in your career?
Cindy St. Hilaire: That's a good thing.
Chris Toepfer: Yeah. I started out as an undergraduate in London, and actually during the second year of my undergraduate degree, I fell into a lab kind of out of interest. It was starting to study cardiac muscle mechanics. And that was the lab of Professor Michael Ferenczy. And ended up, after I finished my undergraduate degree, I joined him for a PhD. I had a PhD program that also took me overseas to the NIH to work with Dr James Sellers, who was a muscle motor protein biochemist. And we really, I sort of really fell in love, with the idea of studying disease of multiple levels, and understanding how the heart would function from the basic molecule up to the entire organ and looking at different systems in between.
Chris Toepfer: And that's what led me to then, so my postdoctoral position to seek out a completely different direction in some ways, but something that could also extend how we could look at the heart. And that's where I moved to Boston to work with Christine and Jonathan Seidman. I'm looking at more of the genetic basis then of hypertrophic cardiomyopathy rather than just, sort of more diffusely the mechanisms underlying cardiac muscle contraction. And then two years ago, I moved back to the UK to Oxford to sets up my own group, which has been fun during the pandemic as you can imagine.
Cindy St. Hilaire: It's hard enough starting up a lab under normal times. I can't imagine doing it during a pandemic.
Chris Toepfer: And we are now completely focused on stem cell models and CRISPR CAS engineering, and trying to understand hypertrophic cardiomyopathy in a dish.
Cindy St. Hilaire: That's wonderful. And actually I looked at your CV. We actually overlapped a little bit. I was doing my postdoc at NIH in the NHLBI while you were there for your graduate school. So I too fell in love with kind of the starting with the human as the model path of research. So maybe you can kind of fill in all the listeners in who aren't cardiomyopathy experts. So what is, I guess, in a nutshell, hypertrophic cardiomyopathy, and what gap in knowledge was your study specifically addressing?
Chris Toepfer: So in general, about one in 500 people have hypertrophic cardiomyopathy. And for those that are genetically linked, a lot of them are in the key contractile proteins of the heart, the drive muscle contraction. And what you often see in those people is they have thickened hearts. And what happens is actually the heart begins to be too hard, and it actually relaxes very poorly in between beats.
Chris Toepfer: So what we are really trying to understand in this disease and with this abstract was how are different forms of hypertrophic cardiomyopathy created? Because it can be a couple of different forms. There are different proteins involved that have very vastly different functional mechanisms within the cell. So would this, we went away, we generated some stem cell models where we could then differentiate into cardiomyocytes. Model the disease in a dish. And we made kind of a group of good methods to go and look at what was happening inside the cells. And then we could screen drugs against what's happening inside those cells, so that was kind of the idea of what we were looking at, at the time. And what's fallen out of all of that is a drug now called Melacamptin that's starting to get to the clinic, which addresses some of these underlying mechanisms we were beginning to study. So that's what I'll talk about a bit later on in our session today.
Cindy St. Hilaire: It's great. One of the things you focused on in the abstract is comparing these thick and thin filament variants. What are the implications of those, I guess, in the human disease state, but also in how you could design or use your stem cells as a model, and were any of the results that you found surprising?
Chris Toepfer: So I think what was the really key finding that we saw was that the thick filament variants seemed to be switching myosin, which is a molecular motor that drives cardiac muscle contraction very much to arm”ON”. And my sort of analogy to that is they're all very sort of bodybuilder like. Myosin switched on, ready to go to work causing way too much contraction. And the compound that we were using at the time Myocamptin, we could turn those off and resolve the disease. Whereas with the thin filament variants, they were operating through a completely different mechanism. And when we tried to treat them with the same compound, they wouldn't always salvage disease. So though the face of it, they look the same in the dish, in that they contracted too much, relaxed very poorly. You're clearly doing it via complete different mechanism. And that's what we're starting to dig into now. And that's what we'll be talking about.
Cindy St. Hilaire: Yeah. And that's actually kind of the question I was going to finish up with you. What are the, I guess translational implications? No, yes. You're using this drug. Is that only good for thick filament-like variants? And are you going to be able to screen patients to tell which variant they have, and therefore if this or that drug might be useful?
Chris Toepfer: So we're in a real golden age now for genomics where I guess patients can come into the clinic and they can be sequenced and you could maybe tell them now what might be the underlying cause of their disease. I am not a clinician, but what we, as a basic scientist can say is, well, we can go away and try and understand whether this variant you may have in your genome is causative of disease. And if it is what mechanism that may fall under, what may be causing them to have this phenotype?
Chris Toepfer: And I think what we can do is we can try and then bin the subpopulations of variants, and try and find novel drugs or novel pathways that we could try and find drugs for to treat the disease, and to differentiate them from each other. So I think it's too early to say whether Mylocamptin will be able to sort this for everybody, I guess we will find out in the next years. But I think already we can start thinking about, well, what would be the next step after this? We can bring precision medicine even further. And that's, I think the goal where we're heading towards.
Cindy St. Hilaire: Well, that's wonderful, and this is a wonderful abstract. I'm really looking forward to seeing the full study and your presentation later on. And thank you so much for joining.
Chris Toepfer: No. Yeah. Thank you for having me. I'm really looking forward to it later on.
Cindy St. Hilaire: Great. Dr Chen Gaol is the third finalist for the BCBS Outstanding Early Career Investigator Award. She's an assistant researcher at UCLA, and her abstract is titled, Functional Impact of RBFox1C in Cardiac, Pathological Remodeling through Targeted MRNA Stability Regulation. So congratulations, and thank you so much for joining me today.
Chen Gal: Absolutely, thank you for having me.
Cindy St. Hilaire: Before we jump into your abstract, could you share with us a little bit about your career path, and how you came to study the role of RNA binding proteins, I guess specifically in pathological cardiac remodeling?
Chen Gal: Yes, I think my research over the years has been into the very basic questions, which is I'm interested in looking at how the RNA is being regulated. For example, how the RNA is being spliced, is being ideated, and how the RNA is being degraded if it's ever been translated into protein. And the second half of my research is of course, physiological driven, because I'm interested in different type of cardiac disease, starting from the traditional heart attack to the now more emerging medical need, which is the cardiometabolic disease. So I was trained as a molecular biologist. I started in molecular biology Institute at UCLA. My PhD supervisor is Dr Yibin Wang, who first introduced me to understand there is actually a whole new world of R regulation at a post-transcription level.
Chen Gal: So at that time we basically utilized the R sequencing. Just look for the easiest to heart, and try to understand how these RNA are differentially spliced in the heart. And I was so interested in understanding more about a cardiology. So I decided, even if I move out to my postdoc research I still want to continue working in the heart, although at a totally different angle. And that is when I started to really try to understand different aspects of RNA regulation. So now I am starting to be a junior faculty, establishing my own lab. And I really wanted to understand more how different steps of our metabolism is regulated.
Cindy St. Hilaire: Really timely research. And I really like how you are doing a great job combining extremely basic biochemical processes with advanced disease states. An extra, that's why this abstract made it as a finalist. So congrats on that. So your study was focused on the RNA binding protein, RB Fox one, which has several isoforms. And so can you tell us which isoform you were looking at, and why you were interested in that particular isoform?
Chen Gal: Yes, actually I've studied about ISO form of RPFox1. It itself, is actually subject to alternative splicing, while generating one nuclear, and another simosolic isoform. Where I was a PhD student, I was very simple minded, just trying to screen for the R binding protein that actually is expressed in the diseased heart. So RBFox1 is at least at a transcriptional level, the only one that we identify to be to decreased in the fatal heart. The nuclear function, the nucelo ISO form of RPFox1 is mainly regulating alternative splicing. But it is when I was studying this nuclear function of the RBFox1, I identified there is actually another isoform where she is in the set ourselves based on the different of c terminal domains of the RFox1. So I was just wondering, apparently you shouldn't be regulating and splicing anymore. I just move on to another layer of RA regulation. And then what I found most interesting is these RBFox1 is regulating the R stability, which is something that we'll talking about later today.
Cindy St. Hilaire: That's great. So to do this study, you actually created a new knockout mouse model where you specifically deleted this one C isoform. What was kind of the baseline and maybe the disease state phenotypes that you saw in that mouse?
Chen Gal: The result and phenotype so far is very striking. We utilize the CAS nine CRISPR technology simply because for, we were lucky the settle the Fox warehouse, one extra axon. So that does allow us to coach the lox P side, just blanking in that particular AXA. And in theory we could across it with different CRE, and to generate either cardiac or different tissue, specifically knock out. Even at a baseline we see a decreased cardiac function when we inactivate this isoform in the adult heart. And when we look at the gene expression profile is, I call mind-blowing type of experience, because turns out this gene not only is regulating some of the inflammatory genes, but also is helping involve protein translation and delivery metabolism, which I hope in the future will set us on the path to really understand the role of this RP Fox1. Not only into HFpEF, but also in the cardiometabolic disorder.
Cindy St. Hilaire: Yeah, that's great. It's so rewarding when you do this one really big kind of risky experiment, and it turns into not just one interesting path to study, but multiple. One of the things that you mentioned in the abstract is clip seek. I was wondering if you could tell us a little bit about this technology, and how you used it in your study?
Chen Gal: Yeah. I think one of the rewarding parts for me focusing on the R metabolism is really driving different accounting and sequencing tools, and utilize that in the heart. So cardiomyocyte has been traditionally viewed now to be very easy to work with type of model comparing helo cells, right? And I think in the field, we are still so short of knowledge, what type of the cutting-edge tools that we can use in the heart. My research involved clip seek, which is to use UV crosslinking the RNA with the R binding protein. So that will allow us to understand which are the RNA targets that are directly interacting with the RNA binding protein. I'm also using great seek, which is to find dynamically label the recency size to RNA. And that will allow us to look forward to RA degradation profile at a global level in the baseline or under disease. So I thought those are really cool technologies, and that's something that makes me excited about my work on a daily basis.
Cindy St. Hilaire: Yeah, that's wonderful. So what's next? What are you going to do after this initial study? What's the next question you're going to go after?
Chen Gal: Yeah, like I mentioned, I'm interested in, honestly, different type of heart disease, not just the stress induced heart failure, but also the recent years, I started to branch out a little bit to understand more of the biology of HFpEF. For example, how the R binding protein that we are studying right now is playing a role in the development of HFpEF. Or we actually understand very little about them, the micromechanism for HFpEF development, right. What are the RNA splicing profile in the cardio metabolic disorder on account? We also find differential regulation of R stability in the HfPEF compared to the HFpEF compared to the HFrEF. So I thought those are really interesting questions that I would like to pursue in the future.
Cindy St. Hilaire: That's great and best of luck in those future studies.
Chen Gal: Thank you.
Cindy St. Hilaire: Before we leave, I was wondering if you could share with us any advice that you would give to a trainee, maybe something that you wish you knew ahead of time in this kind of early career stage.
Chen Gal: I consider myself a really, really lucky person. And if I have one word to give to the younger people, younger than me, is to find great mentors for your career. And luckily our field has a lot of good mentors who are ready to help us every single step of our career. For example, my PhD supervisor, Dr Wang. And I have met a lot of good mentors inside and outside of UCLA. I'm pretty sure this is the same thing for Chris, who is trained by Dr Seidman, and everybody know how great a mentor she is. So I think having a great mentor will help you every step of your career development to making sure you're always on the right track. And that, that is also something that you will do when we have our own lab, because we want to be great mentors for our trainees as well.
Cindy St. Hilaire: I know. That's something I strive for too, is to emulate my amazing mentors that I've had. What do you think is a good quality for a good mentor? Like what's one of the, I guess key features that you look for in someone that you would like to be your mentor?
Chen Gal: For me, I think my mentors are all cheerleaders. They never try to push me to move out one career path versus the other. They are good listeners, and they are also my role models.
Cindy St. Hilaire: That's wonderful. Chris, what's a piece of advice that you would like to share with trainees that your former self wish you knew of?
Chris Toepfer: I think it's very important to echo the message of a good mentorship, and a good lab environment that allows you to flourish and really helps you to grow yourself to the future. And also helps you understand the bits of you that you could actually grow as well, a little bit better. So you become a more rounded scientist. I think something that's really important or something that I've always found very infectious is to find mentorship and mentors that are also incredibly enthusiastic about you as an individual, as well as the science. I think that that can really drive you. And I think that's also an important thing to have in yourself, to have, to find that question for yourself that really drives you and you can be really enthusiastic about.
Cindy St. Hilaire: I totally agree. Well, thank you again for joining me today. Congratulations on being a finalist, and I wish everyone the best of luck in their presentations later on at BCBS.
Chen Gal: Thank you so much.
Jiangbin Wu: Thank you.
Chris Toepfer: Thank you very much.
Cindy St. Hilaire: That's it for the highlights from the September 17th and October 1st issues of Circulation Research. Thank you for listening. Please check out the CircRes Facebook page, and follow us on Twitter and Instagram with the handle @CircRes and #Discover CircRes. Thank you to our guests, BCBS Outstanding Early Career Investigator Award Finalists, Dr Jaobing Wu, Dr Chen Gal, and Dr Chris Toepfer. And a special congratulations to Dr Toepfer who won this year's competition. This podcast is produced by Asahara Ratnayaka, edited by Melissa Stoner, and supported by the editorial team of circulation research. Some of the copy texts for highlighted articles is provided by Ruth Williams. I'm your host, Dr Cindy St. Hilaire. And this is Discover CircRes, you're on the go source for the most exciting discoveries in basic cardiovascular research. This program is copyright of the American heart association, 2021. The opinions expressed by speakers in this podcast are their own and not necessarily those of the editors or of the American heart association. For more information, please visit AHAjournals.org