October 2022 Discover Circ Res

This month on Episode 41 of Discover CircRes, host Cynthia St. Hilaire highlights four original research articles featured in the September 30 and October 14 issues of Circulation Research. This episode also features an interview with Dr Kory Lavine and Dr Chieh-Yu Lin from Washington University St. Louis, to discuss their study, Transcriptional and Immune Landscape of Cardiac Sarcoidosis.   Article highlights:   Tian, et al. EV-Mediated Heart Brain Communication in CHF   Wleklinski, et al.  Impaired Dynamic SR Ca Buffering Causes AD-CPVT2   Masson, et al. Orai1 Inhibition as a Treatment for PAH   Li, et al. F. Prausnitzii Ameliorates Chronic Kidney Disease   Cindy St. Hilaire:        Hi, and welcome to Discover Circ Res, the podcast of the American Heart Association's journal, Circulation Research. I'm your host, Dr Cynthia St. Hilaire from the Vascular Medicine Institute at the University of Pittsburgh, and today I'm going to highlight articles from our September 30th and October 14th issues of Circulation Research.                                           I'm also going to have a chat with Dr Kory Lavine and Dr Chieh-Yu Lin from Washington University St. Louis, and we're going to discuss their study Transcriptional and Immune Landscape of Cardiac Sarcoidosis. But before I get to the interview, I'm going to highlight a few articles.   Cindy St. Hilaire: The first article I'm going to share is Extracellular Vesicles Regulate Sympathoexcitation by Nrf2 in Heart Failure. The first author of this study is Changhai Tian, and the corresponding author is Irving Zucker, and they are at University of Nebraska. After a myocardial infarction, increased oxidative stress in the heart can contribute to adverse cardiac remodeling, and ultimately, heart failure. Nrf2 is a master activator of antioxidant genes, suggesting a protective role, but studies in rats have shown its expression to be suppressed after MI, likely due to upregulation of Nrf2-targeting microRNAs. These microRNAs can also be packaged into vesicles and released from stressed heart cells.   Now, this group has shown that rats and humans with chronic heart failure have an abundance of these microRNA-containing EVs in their blood. In the rats with chronic heart failure, these extracellular vesicles were found to be taken up by neurons of the rostral ventrolateral medulla, RVLM, wherein the microRNA suppressed Nrf2 expression. The RVLM is a brain region that controls the sympathetic nervous system, and in the presence of EVs, it is ramped up by sympathetic excitation. Because such elevated sympathetic activity can induce the fight or flight response, including increased heart rate and blood pressure, this would likely worsen heart failure progression. The team, however, found that inhibiting microRNAs in the extracellular vesicles prevented Nrf2 suppression in the RVLM and sympathetic activation, suggesting the pathway could be targeted therapeutically.   Cindy St. Hilaire:        The next article I want to highlight is titled, Impaired Dynamic Sarcoplasmic Reticulum Calcium Buffering in Autosomal Dominant CPVT2. The first author of this study is Matthew Wleklinski, and the corresponding author is Bjӧrn Knollmann, and they are at Vanderbilt University.   Exercise or emotional stress can prompt the release of catecholamine hormones, which induce a fast heart rate, increased blood pressure, and other features of the fight or flight response. For people with catecholaminergic polymorphic ventricular tachycardia, or CPVT, physical activity or stress can cause potentially lethal arrhythmias. Mutations of calsequestrin-2, or CASQ2, which is a sarcoplasmic reticulum calcium-binding protein, is a major cause of CPVT, and can be recessive or dominant in nature.   For many recessive mutations, disease occurs due to loss of CASQ2 protein. This group investigated a dominant lysine to arginine mutation in this protein, and found by contrast, protein levels remain normal. In mice carrying the mutation, not only was the level of CASQ2 comparable to that in control animals, but so, too, was the protein's subcellular localization. The mutation instead interfered with CASQ2's calcium binding or buffering capability within the sarcoplasmic reticulum. The result was that upon catecholamine injection or exercise, the unbound calcium released prematurely from the sarcoplasmic reticulum, triggering spontaneous cell contractions. In uncovering this novel molecular etiology of CPVT, the work provides a basis for studying the consequences of other dominant CASQ2 mutations.   Cindy St. Hilaire:        The next article I want to highlight is from our October 14th issue of Circulation Research, and the title of the article is ORAI1 Inhibitors as Potential Treatments for Pulmonary Arterial Hypertension. The first author is Bastien Masson, and the corresponding author is Fabrice Antigny, and they're from Inserm in France. In pulmonary arterial hypertension, the arteries of the lungs become progressively obstructed, making it harder for the heart to pump blood through them, ultimately leading to right ventricular hypertrophy and heart failure. A contributing factor in the molecular pathology of pulmonary arterial hypertension is abnormal calcium handling within the pulmonary artery smooth muscle cells. Indeed, excess calcium signaling causes these cells to proliferate, migrate, and become resistant to apoptotic death, thus leading to narrowing of the vessel.   This group now identified the calcium channel ORAI1 as a major culprit behind this excess signaling. Samples of lung tissue from pulmonary arterial hypertension patients and a pulmonary arterial hypertension rat model had significantly upregulated expression of this channel compared with controls. And in patient pulmonary arterial smooth muscle cells, the high ORAI1 levels resulted in heightened calcium influx, heightened proliferation, heightened migration and reduced apoptosis. Inhibition of ORAI1 reversed these effects. Furthermore, in pulmonary hypertension model rats, ORAI1 inhibition reduced right ventricle systolic pressure and attenuated right ventricle hypertrophy when compared with untreated controls. This study indicates that ORAI1 inhibitors could be a new potential target for treating this incurable condition.   Cindy St. Hilaire:        The last article I want to share is titled Faecalibacterium Prausnitzii Attenuates CKD via Butyrate-Renal GPR43 Axis. The first author of this study is Hong-Bao Li, and the corresponding author is Tao Yang, and they are from the University of Toledo.   Progressive renal inflammation and fibrosis accompanied by hypertension are hallmarks of chronic kidney disease, which is an incurable condition affecting a significant chunk of the world's population. Studies indicate that chronic kidney disease is linked to gut dysbiosis. Specifically, depletion of lactobacillus bifidobacterium and faecalibacterium, prompting investigations into the use of probiotics. While supplements including lactobacillus and bifidobacterium have shown little effectiveness in chronic kidney disease, supplementations with F. prausnitzii have not been investigated.   Now, this group has shown in a mouse model of chronic kidney disease that oral administration of F. prausnitzii has beneficial effects on renal function, reducing renal fibrosis and inflammation. This bacterial supplementation also produced the short chain fatty acid butyrate, which was found to be at unusually low levels in the blood samples from the CKD model mice and from chronic kidney disease patients. Oral supplementation with this bacterium boosted butyrate levels in the mice, and in fact, oral administration of butyrate itself mimicked the effects of the bacteria. These findings suggest that supplementation with F. prausnitzii or, indeed, butyrate could be worth investigating as a treatment for chronic kidney disease.   Cindy St. Hilaire:        Today I have with me Dr Kory Lavine and Dr Chieh-Yu Lin from Washington University St. Louis, and we're going to talk about their paper, Transcriptional and Immune Landscape of Cardiac Sarcoidosis. This is in our September 30th issue of Circulation Research. Welcome, and thank you for taking the time to speak with me today.   Chieh-Yu Lin:             Thank you for inviting us. It's a great honor to be here today.   Kory Lavine:               Thank you.   Cindy St. Hilaire:        Really great paper, ton of data, and hopefully, we can pick some of it apart. But before we get into it, I actually want to just talk about sarcoidosis generally. I know it's a systemic inflammatory disease that has this kind of aggregation of immune cells as its culprit, and it can happen in a bunch of different organs. It's mostly in the lung, but it's also, like you're studying, in the heart. Can you just give us a little bit of background? What is sarcoidosis, and how common is cardiac sarcoidosis?   Chieh-Yu Lin:             Well, this is actually a great question, and I'll try to answer it. You actually capture one of the most important kind of features for sarcoidosis. It happens in all kind of organ system, mostly commonly in lung, in lymph nodes, but also in heart, spleen, even in brain, or even orbit, like eyes. It's really a truly multisystemic disease that has been characterized by this aggregate of macrophages, or myeloid cells, with scattered multinucleated giant cells, as the name implies, have multiple nuclear big, chunky, cells that form an aggregate. That's kind of like a pathognomonic feature for sarcoidosis, whether it's happening in lung, in the heart. When any organ system, a lot of studies has been done, but as of now, a very clear pathogenesis or mechanism has been, I would say, still pretty elusive, or still remain quite unclear, despite all the great effort has been made in this field. The other thing is that a lot of the studies actually focusing on pulmonary sarcoidosis for good reasons. Actually, that's one of the most common manifestations. For cardiac sarcoidosis, although it's only effect in probably, I would say depends on the data, 20% to 30% of the outpatient that with sarcoidosis, with or without lung involvement. It's actually carry a very significant clinical implications as of matter that the presentation of cardiac sarcoidosis can be devastating and sometimes actually fatal. Some of the study actually show that cardiac sarcoidosis actually higher, up to 80%, just because the first presentation's actually, unfortunately, sudden cardiac death. That's why Kory and I, we teamed up. I'm a cardiothoracic pathologist, so in my clinical practice I see specimens and samples from human body, from patient suffer from sarcoidosis, both in lung, lymph node, and heart. Kory is an outstanding heart failure, heart transplant cardiologist, see the other end, which is the patient care. This disease, specifically in heart, its presentation and its pathogens in heart, really attracts our attention.   Cindy St. Hilaire:        Do we know any or some of the potential causes? Why it would start, maybe in a different patient population, but also in the heart versus the lung? Do we know anything about that process?   Kory Lavine:              We know nothing about it. Sarcoid has no known etiology. There's been thoughts in the past that it may be driven by infection, the typical pathogens or autoimmune ideologies, but really, there's little data out there to support those possibilities. Right now, the field's wide open. The other challenge is we don't really have a good way to treat this disease, so a lot of the therapies available are things like steroids, which can have some effect on the disease but carry a lot of risk of complications. The other agents that we sometimes use to lower the doses of steroids, things like methotrexate and azathioprine, are only modestly effective.   These are really the motivation for Chieh-Yu and myself to pursue this. We don't really know what causes the disease, and we don't really have very good treatments. We really wanted to take the first step, that's to study the real disease, and understand what are the pathologic cell types that are present within the granuloma, which is these aggregation of immune cells that Chieh-Yu was speaking about.   Cindy St. Hilaire:        What is actually happening at the beginning of this disease? These granulomas form, and then what is the pathological progression in the heart? What goes on there?   Chieh-Yu Lin:             This is actually another great question that I will say there's not much that has been discovered because, especially in human tissue, every time we have a sample, it's actually a kind of time point. We cannot do a longitudinal study. But in general speaking, very little is known about how it's initiated because it will need to accumulate to a certain disease burden for this to have a clinical symptom sign and be manifested, and then being clinically studied. We do know that in both heart and lung after treatment of progressions, it's usually in, a general speaking, going through a phase from a more proliferative means that it's creating more granulomas, more  inflammatory cell aggregate, to a more fibrotic phase. Means that sometimes you actually see the granuloma start to disappear or dissipate, and then showing this kind of dense collagen and fibrosis. That has been commonly documented in both lung and heart sarcoidosis. The other things is that very difficult to study this disease that we do not have a great animal model, so we cannot use animal model to try to approximate or really study the disease pathogenesis. There are several animal models they try to use microbacteria or infectious agents, and these infectious agents can create morphologically similar granuloma, per se, but just like in human body. For instance, patients suffer from TB in their lung, biopsy will show this. But clinically, these are two very distinct disease entities, even though they look alike. Even in the heart, one of the conditions that we study in our paper is giant cell myocarditis, as the name implying having multinucleated giant cells granuloma. It looks really alike under microscopy for pathologists like me, but their clinical course in response to treatment is drastically different. This type of barriers and in the current limitations of our study tool makes, as Kory just said, this is really a wide open. We just know so little despite all the effort.   Cindy St. Hilaire:        Yeah. I'm guessing based on this granuloma information, to start with, the obvious question you went after is going after the immune cell populations that possibly contribute to sarcoidosis. To do this, because you have the human tissue, you went for single cell transcriptional profiling, which is a great use of the technology. But what biological sources did you use, and how did you go about choosing patient? Because the great thing about single cell is you can do just that, you can look at however many thousands of cells in one patient. But how do you make sure or check that that is broadly seen versus just a co-founding observation in that patient?   Kory Lavine:               We use explanted hearts and heart tissue from patients that underwent either heart transplantation or implementation of LVADs. It's a pretty big hunk of myocardium, and we're lucky to work with outstanding pathologists both at WashU, JU, as well as our collaborators at Duke. Between the two institutions, we're able to pull together a collection of tissues where we knew there were granulomas within that piece of tissue we analyzed. You bring up an important challenge. You need to make sure the disease and cause of the disease is present in the tissue that you're analyzing, otherwise you'll not come up with the data that really is informative.   Chieh-Yu Lin:             Kory beautifully answered the question, but I just wanted to add one little thing, and that's also why we use various different modalities. Some of them is more inside you, like the NanoString Technologies' spatial transcriptomic. You can visualize and confirm that we are studying the phenomenon that has been described for sarcoidosis, and then using multichannel immunofluorescence to validate our sequencing data, to complement such limitations of certain technology.   Cindy St. Hilaire:        Especially, I feel like with this diseased tissue that it's such a large tissue, there's so much information, it's really hard to dig in and figure out where the signal is. This was a wonderful paper for kind of highlighting, integrating all these new technologies with also just classical staining. Makes for great pictures as well. How does this cellular landscape of cardiac sarcoidosis compare to a normal heart? What'd you find?   Chieh-Yu Lin:             This is a great question. Compared to normal heart, we have been talking about this accumulation of macrophages with scattered multinucleated giant cells. For the similar landscape, first and foremost, you do not see those type of accumulations in brain microscopy or by myeloid markers in the heart. Although, indeed, in even normal heart tissue we have rest and macrophages. It just doesn't form such morphological alterations. But then we dive deep into it, and then we found that from a different cell type perspective, we realized that the granuloma is composed by several different type of inflammatory cells, with most of the T cells and NKT cells kind of adding periphery. The myeloid cells, including the multinucleated giant cells also, are kind of in the center of the granuloma of the sarcoidosis. Then, we further dive in and realize that there are at least six different subtype of myeloid cells that is contributing to the formation of this very eye-catching distinctive granular malformations, and to just never feel first off and foremost, of course, is those multinucleated giant cells that is really distinct, even on the line microscopy] routine change stand.   And then we have a typical monocyte that's more like a precursor being recently recruited to the heart, and we finally sent the other four different type of myeloid cell that carry different markers, and then improving the resident macrophages. Especially for me as a pathologist, I'm using my eye and looking at stand every day, is actually these six type of cells, myeloid cells, actually form a very beautiful special kind of distribution with the connections or special arrangement with all different type, kind of like multinucleated giant cell in the middle, flanked by HLA-DR positive epithelioid macrophages, kind of scatter, and then with dendritic cells and a typical monocyte at the peripheral, and then resident macrophage kind of like in the mix of the seas of granuloma information. All these are distinct from normal heart tissues that does carry a certain amount of macrophages, but just don't form this orchestrated architectural distinct structure that's composed of this very complicated landscape.   Cindy St. Hilaire:        Those images, I think it was figure six, it's just gorgeous to look at, the model you made. One of the questions I was thinking is there must be a significance between these cells that are on the periphery and those that are in the center of this granuloma. Do you have an idea or can we speculate as to are some more cause and some more consequence of the granuloma? Were you able to capture any more information about maybe the initiating steps of these from your study?   Kory Lavine:              That's a great question, and a question the field has had for a long time. Now, we know there's different populations of cells. The single cell data allows us to understand what are the transcriptional differences and distinctions between them to gain some insights. One thing that we do know from the field is that disease activity correlates with mTOR activity within these granulomas. We took advantage of phospho-S6 kinase staining as a downstream marker of mTOR activity, and Ki-67 is a marker of self proliferation.   Which of these populations within the granuloma might be most active with respect to mTOR and respect to proliferation? If you ask most people in the field, they would jump up and say, "It's the giant cell in the middle." We found that that's not actually the case at all. It's the macrophages that surround the giant cell, the ones that are HLA-DR positive, the epithelioid macrophages, and the ones that are SYLT-3 positive that are scattered around them. That's really interesting and could make a lot of sense, and leads to hypothesis that perhaps activation mTOR signaling within certain parts of the granuloma might be sufficient to set up the rest of the architecture. That's something that we can explore in animal models, and are doing so to try to create a cause and effect relationship. Cindy St. Hilaire:        Yeah, and I was actually thinking about this, too, in relation to kind of the resident macrophages versus infiltrating macrophages or even just infiltrating immune cells. Do you know the original source of the cells that make up the granuloma? Is it mostly resident immune, or are they recruited in?   Kory Lavine:               We can make predictions from the single cell data where you can use trajectory analysis to make strong predictions about what the origin of different populations might be. What those analyses predicted is that the giant cells and the cells that surround the giant cells, the HLA-DR positive and SYLT-3 positive macrophages, come from monocytes. That's the prediction, and, of course, resident macrophages do not. However, that prediction has to be tested, and that's the beauty and importance of developing animal models. The wonderful thing today is we now have genetic tools to do that. We can ask that question.   Cindy St. Hilaire:        I don't know. Maybe you don't want to spoil the lead of the next paper, but what kind of mouse model are you thinking about trying?   Kory Lavine:               Yeah. First of all, let me talk about the tools that are available, because they're published in Circulation Research, of course. We have a nice tool to specifically mark, track and delete in tissue resident macrophages using a CX3CR1 ERT pre-mouse, and taking advantage of the concept that tissue macrophages don't turn over from monocytes and turn over from themselves. We can give tamoxifen to label all monocytes macrophages in Dcs with that CRE, and then wait a period of time where only the resident macrophages remain labeled. We can use that trick to modulate mTOR signaling as a first step, and ask whether mTOR signaling is required in that population. We've now developed a new genetic tool to do the same thing in just recruited macrophages.   Cindy St. Hilaire:        What was the most challenging aspect of this study? There's a lot of moving parts. I'm sure probably the data analysis alone is challenging, but what would you say is the most challenging?   Kory Lavine:               I think you alluded to this early on, but the most challenging thing is collecting the right tissues to analyze, and that's not a small feat or a small effort here. All the technologies are a lot of fun, and everything works so well today compared to many years ago when we trained, so it's an exciting time to do science. The most challenging and time-consuming component was assembling a group of tissues that we could do single-cell sequencing on between our group and our colleagues at Duke, and then creating validation cohorts that we did across several different institutions, including our own as well as Stanford. That team effort in building that team is the most important, challenging, and honestly, enjoyable part of this.   Chieh-Yu Lin:             I cannot agree more what Kory just said. I think that that's the challenging and the fun part, and that we're very fortunate to really have a great team to tackle this questions in multiple from multiple institute. I just want to add one more thing that, particularly for me as a cardiopathologist, one of the hardest things is I've known how to look or diagnose sarcoidosis for years, but seeing the data emerging that is so complicated and then beyond my reliable eyes in understanding, it's kind of mentally very challenging but very fun to really open and broaden the vision. It's not just how it looks like just giant cells in macrophages.   Cindy St. Hilaire:        What do you think about in terms of diagnostics or even potential therapies? How do you think this data that you have now can be leveraged towards those objectives, whether it's screening for new cell types that are really key to this granuloma formation versus therapeutically targeting them?   Kory Lavine:              This study opens new doors, and right now, diagnosis of sarcoids islimited by trying to biopsy, which, in the heart, is limited by sample bias. You certainly can biopsy the wrong area because you don't know whether a granuloma is in the area or not. We do do some cardiac and other imaging studies like FDG-PET scans, which are helpful but are not perfect, and each of them has their individual limitations. One of the beauties of our study is it identifies new markers of macrophage populations that live within the granuloma, many of which are unique to this disease.   That suggests that there's maybe an opportunity to develop imaging tracers that can identify those populations more specifically than our current PET imaging studies do, which rely simply on glucose uptake. It also opens up the possibility that we may able to take blood samples and identify some of these cell types within the blood, and have more simple testing for our patients. I think in terms of therapy, you alluded to it earlier, these concepts about mTOR signaling, that could be a new therapeutic avenue that needs to be rigorously explored in preclinical models. We're lucky already to have very good mTOR inhibitors available in clinical practice today.   Cindy St. Hilaire:        Obviously, opening new doors is amazing because it's more information, but often a good study leads to even more questions to be asked. What question, or maybe what questions, are you guys going to go after next?   Chieh-Yu Lin:             Well, that list is very long, and then that's actually the exciting thing about doing this research. There's no bad questions, in some sense. All the way from diagnosis, management, monitoring, therapeutic, how we predict where the patient can respond, that's the whole clinical side. Even the basic science side, we still haven't really answered the question, although our data suggests where that multinucleated giant cells coming from. It's very eye catching. How do they form, even though our data suggests it's from the recruited macrophages. But that's still a long way from the recruited macrophage,  monocyte to that gigantic bag of nuclei in the very fluffy cytoplasm.   And then, how the granuloma, as we discussed earlier in this discussion, really initially from a relatively normal background myocardium to form this disease process. There are just so many questions that we can ask. There are, of course, several fronts that we would like to focus on. Kory already nicely listed some of them. First and foremost is actually to establish animal model to enable us to do more details in mechanistic studies, because human tissue, as good as it is, it's kind of like a snapshot, just one time point, and it really limits our ability to test our hypothesis. Animal model, certainly, is one of the major directions that we are going forward, but also the other side, like more clinical science also to develop novel noninvasive methodologies to diagnose and to hopefully monitor this patient population in a better way.       Cindy St. Hilaire:        Well, it's beautiful work. I was actually reading this paper this weekend at a brunch place just next door to my house, and the guy sitting next to me happened to see over my shoulder the title and said that his father had passed away from it. This is hopefully going to help lots of people in the future, and really help to make the models that we need to ask, "What's happening in this disease?" Thank you so much for taking the time to speak with me, and congratulations on what seems to be a landmark study in understanding what's going on in this disease.   Chieh-Yu Lin:             Thank you so much. It's a pleasure.   Cindy St. Hilaire:        That's it for our highlights from the September 30th and October 14th issues of Circulation Research. Thank you so much for listening. Please check out the Circ Res Facebook page, and follow us on Twitter and Instagram with the handle @CircRes, and hashtag Discover Circ Res. Thank you so much to our guests, Dr Kory Lavine and Dr Chieh-Yu Lin from Washington University St. Louis. This podcast is produced by Ashara Retniyaka, edited by Melissa Stoner, and supported by the editorial team of Circulation Research. Some of the copy texts for highlighted articles was provided by Ruth Williams. I'm your host, Dr Cynthia St. Hilaire, and this is Discover Circ Res, your on-the-go source for the most exciting discoveries in basic cardiovascular research. This program is copyright of the American Heart Association, 2022. The opinions expressed by speakers in this podcast are their own, and not necessarily those of the editors of the American Heart Association. For more information, please visit ahajournals.org.