Endothelial Cell Lineage Analysis Does Not Provide Evidence for EMT in Adult Valve Homeostasis and Disease

LncRNA-SERB promotes vasculogenic mimicry (VM) formation and tumor metastasis in renal cell carcinoma

A growing body of evidence shows that vasculogenic mimicry (VM) is closely related to the invasion and metastasis of many tumor cells. Although the estrogen receptor (ER) can promote initiation and progression of renal cell carcinoma (RCC), how the downstream biomolecules are involved, and the detailed mechanisms of how ER expression is elevated in RCC remain to be further elucidated. Here, we discovered that long noncoding RNA (LncRNA)-SERB is highly expressed in tumor cells of RCC patients. We used multiple RCC cells and an in vivo mouse model for our study, and results indicated that LncRNA-SERB could boost RCC VM formation and cell invasion in vitro and in vivo. Although a previous report showed that ERβ can affect the VM formation in RCC, it is unclear which factor could upregulate ERβ. This is the first study to show LncRNA-SERB can be the upstream regulator of ERβ to control RCC progression. Mechanistically, LncRNA-SERB may increase ERβ via binding to the promoter area, and ERβ functions through transcriptional regulation of zinc finger E-box binding homeobox 1 (ZEB1) to regulate VM formation. These results suggest that LncRNA-SERB promotes RCC cell VM formation and invasion by upregulating the ERβ/ZEB1 axis and that therapeutic targeting of this newly identified pathway may better inhibit RCC progression.

Lineage Tracing Identifies Dynamic Contribution of Endothelial Cells to Cardiac Valve Mesenchyme During Development

Heart valve disease is an important cause of morbidity and mortality among cardiac patients worldwide. However, the pathogenesis of heart valve disease is not clear, and a growing body of evidence hints at the importance of the genetic basis and developmental origins of heart valve disease. Therefore, understanding the developmental mechanisms that underlie the formation of heart valves has important implications for the diagnosis, prevention, and treatment of congenital heart disease. Endothelial to mesenchymal transition is a key step in initiating cardiac valve development. The dynamic changes in the relative localization and proportion of different cell sources in the heart valve mesenchymal population are still not fully understood. Here, we used the Cdh5-CreER;R26R-tdTomato mouse line to trace endocardial cushion-derived endothelial cells to explore the dynamic contribution of these cells to each layer of the valve during valve development. This is beneficial for elaborating on the role of endocardial cells in the process of valve remodeling from a precise angle.

Temporal Progression of Aortic Valve Pathogenesis in a Mouse Model of Osteogenesis Imperfecta

Organization of extracellular matrix (ECM) components, including collagens, proteoglycans, and elastin, is essential for maintaining the structure and function of heart valves throughout life. Mutations in ECM genes cause connective tissue disorders, including Osteogenesis Imperfecta (OI), and progressive debilitating heart valve dysfunction is common in these patients. Despite this, effective treatment options are limited to end-stage interventions. Mice with a homozygous frameshift mutation in col1a2 serve as a murine model of OI (oim/oim), and therefore, they were used in this study to examine the pathobiology of aortic valve (AoV) disease in this patient population at structural, functional, and molecular levels. Temporal echocardiography of oim/oim mice revealed AoV dysfunction by the late stages of disease in 12-month-old mice. However, structural and proteomic changes were apparent much earlier, at 3 months of age, and were associated with disturbances in ECM homeostasis primarily related to collagen and proteoglycan abnormalities and disorganization. Together, findings from this study provide insights into the underpinnings of late onset AoV dysfunction in connective tissue disease patients that can be used for the development of mechanistic-based therapies administered early to halt progression, thereby avoiding late-stage surgical intervention.

Genetics and pathophysiology of mitral valve prolapse

Mitral valve prolapse (MVP) is a common condition affecting 2-3% of the general population, and the most complex form of valve pathology, with a complication rate up to 10-15% per year in advanced stages. Complications include mitral regurgitation which can lead to heart failure and atrial fibrillation, but also life-threatening ventricular arrhythmia and cardiovascular death. Sudden death has been recently brought to the forefront of MVP disease, increasing the complexity of management and suggesting that MVP condition is not properly understood. MVP can occur as part of syndromic conditions such as Marfan syndrome, but the most common form is non-syndromic, isolated or familial. Although a specific X-linked form of MVP was initially identified, autosomal dominant inheritance appears to be the primary mode of transmission. MVP can be stratified into myxomatous degeneration (Barlow), fibroelastic deficiency, and Filamin A-related MVP. While FED is still considered a degenerative disease associated with aging, myxomatous MVP and FlnA-MVP are recognized as familial pathologies. Deciphering genetic defects associated to MVP is still a work in progress; although FLNA, DCHS1, and DZIP1 have been identified as causative genes in myxomatous forms of MVP thanks to familial approaches, they explain only a small proportion of MVP. In addition, genome-wide association studies have revealed the important role of common variants in the development of MVP, in agreement with the high prevalence of this condition in the population. Furthermore, a potential genetic link between MVP and ventricular arrhythmia or a specific type of cardiomyopathy is considered. Animal models that allow to advance in the genetic and pathophysiological knowledge of MVP, and in particular those that can be easily manipulated to express a genetic defect identified in humans are detailed. Corroborated by genetic data and animal models, the main pathophysiological pathways of MVP are briefly addressed. Finally, genetic counseling is considered in the context of MVP.

Protective Role of Endothelial Fibulin-4 in Valvulo-Arterial Integrity

Background Homeostasis of the vessel wall is cooperatively maintained by endothelial cells (ECs), smooth muscle cells, and adventitial fibroblasts. The genetic deletion of fibulin-4 (Fbln4) in smooth muscle cells (SMKO) leads to the formation of thoracic aortic aneurysms with the disruption of elastic fibers. Although Fbln4 is expressed in the entire vessel wall, its function in ECs and relevance to the maintenance of valvulo-arterial integrity are not fully understood. Methods and Results Gene silencing of FBLN4 was conducted on human aortic ECs to evaluate morphological changes and gene expression profile. Fbln4 double knockout (DKO) mice in ECs and smooth muscle cells were generated and subjected to histological analysis, echocardiography, Western blotting, RNA sequencing, and immunostaining. An evaluation of the thoracic aortic aneurysm phenotype and screening of altered signaling pathways were performed. Knockdown of FBLN4 in human aortic ECs induced mesenchymal cell-like changes with the upregulation of mesenchymal genes, including TAGLN and MYL9. DKO mice showed the exacerbation of thoracic aortic aneurysms when compared with those of SMKO and upregulated Thbs1, a mechanical stress-responsive molecule, throughout the aorta. DKO mice also showed progressive aortic valve thickening with collagen deposition from postnatal day 14, as well as turbulent flow in the ascending aorta. Furthermore, RNA sequencing and immunostaining of the aortic valve revealed the upregulation of genes involved in endothelial-to-mesenchymal transition, inflammatory response, and tissue fibrosis in DKO valves and the presence of activated valve interstitial cells. Conclusions The current study uncovers the pivotal role of endothelial fibulin-4 in the maintenance of valvulo-arterial integrity, which influences thoracic aortic aneurysm progression.

Multimodality imaging and transciptomics to phenotype mitral valve dystrophy in a unique knock-in Filamin-A rat model

AIMS

Degenerative mitral valve dystrophy (MVD) leading to mitral valve prolapse is the most frequent form of MV disease, and there is currently no pharmacological treatment available. The limited understanding of the pathophysiological mechanisms leading to MVD limits our ability to identify therapeutic targets. This study aimed to reveal the main pathophysiological pathways involved in MVD via the multimodality imaging and transcriptomic analysis of the new and unique Knock-In (KI) rat model for the FlnA-P637Q mutation associated-MVD.

METHODS AND RESULTS

WT and KI rats were evaluated morphologically, functionally, and histologically between 3-week-old and 3-to-6-month-old based on Doppler echocardiography, 3D micro-computed tomography (microCT), and standard histology. RNA-sequencing and Assay for Transposase-Accessible Chromatin (ATAC-seq) were performed on 3-week-old WT and KI mitral valves and valvular cells, respectively, to highlight the main signaling pathways associated with MVD. Echocardiographic exploration confirmed MV elongation (2.0 ± 0.1  mm versus 1.8 ± 0.1, p = 0.001), as well as MV thickening and prolapse in KI animals compared to WT at 3 weeks. 3D MV volume quantified by microCT was significantly increased in KI animals (+58% versus WT, p = 0.02). Histological analyses revealed a myxomatous remodeling in KI MV characterized by proteoglycans accumulation. A persistent phenotype was observed in adult KI rats. Signaling pathways related to extracellular matrix homeostasis, response to molecular stress, epithelial cell migration, endothelial to mesenchymal transition, chemotaxis and immune cell migration, were identified based on RNA-seq analysis. ATAC-seq analysis points to the critical role of TGF-β and inflammation in the disease.

CONCLUSION

The KI FlnA-P637Q rat model mimics human myxomatous mitral valve dystrophy, offering a unique opportunity to decipher pathophysiological mechanisms related to this disease. Extracellular matrix organization, epithelial cell migration, response to mechanical stress, and a central contribution of immune cells are highlighted as the main signaling pathways leading to myxomatous mitral valve dystrophy. Our findings pave the road to decipher underlying molecular mechanisms and the specific role of distinct cell populations in this context.

The Role of Transforming Growth Factor-β Signaling in Myxomatous Mitral Valve Degeneration

Mitral valve prolapse (MVP) due to myxomatous degeneration is one of the most important chronic degenerative cardiovascular diseases in people and dogs. It is a common cause of heart failure leading to significant morbidity and mortality in both species. Human MVP is usually classified into primary or non-syndromic, including Barlow’s Disease (BD), fibro-elastic deficiency (FED) and Filamin-A mutation, and secondary or syndromic forms (typically familial), such as Marfan syndrome (MFS), Ehlers-Danlos syndrome, and Loeys–Dietz syndrome. Despite different etiologies the diseased valves share pathological features consistent with myxomatous degeneration. To reflect this common pathology the condition is often called myxomatous mitral valve degeneration (disease) (MMVD) and this term is universally used to describe the analogous condition in the dog. MMVD in both species is characterized by leaflet thickening and deformity, disorganized extracellular matrix, increased transformation of the quiescent valve interstitial cell (qVICs) to an activated state (aVICs), also known as activated myofibroblasts. Significant alterations in these cellular activities contribute to the initiation and progression of MMVD due to the increased expression of transforming growth factor-β (TGF-β) superfamily cytokines and the dysregulation of the TGF-β signaling pathways. Further understanding the molecular mechanisms of MMVD is needed to identify pharmacological manipulation strategies of the signaling pathway that might regulate VIC differentiation and so control the disease onset and development. This review briefly summarizes current understanding of the histopathology, cellular activities, molecular mechanisms and pathogenesis of MMVD in dogs and humans, and in more detail reviews the evidence for the role of TGF-β.

Seamless Genetic Recording of Transiently Activated Mesenchymal Gene Expression in Endothelial Cells During Cardiac Fibrosis

Background: Cardiac fibrosis is a lethal outcome of excessive formation of myofibroblasts that are scar-forming cells accumulated after heart injury. It has been reported that cardiac endothelial cells (ECs) contribute to a substantial portion of myofibroblasts through EndoMT. Recent lineage tracing studies demonstrate that myofibroblasts are derived from expansion of resident fibroblasts rather than from transdifferentiation of ECs. However, it remains unknown whether ECs can transdifferentiate into myofibroblasts reversibly or EndoMT genes were just transiently activated in ECs during cardiac fibrosis. Methods: By using the dual recombination technology based on Cre-loxP and Dre-rox, we generated a genetic lineage tracing system for tracking EndoMT in cardiac ECs. We used it to examine if there is transiently activated mesenchymal gene expression in ECs during cardiac fibrosis. Activation of the broadly used marker gene in myofibroblasts, αSMA, and the transcription factor that induces epithelial to mesenchymal transition (EMT), Zeb1, was examined. Results: The genetic system enables continuous tracing of transcriptional activity of targeted genes in vivo. Our genetic fate mapping results revealed that a subset of cardiac ECs transiently expressed αSMA and Zeb1 during embryonic valve formation and transdifferentiated into mesenchymal cells through EndoMT. Nonetheless, they did not contribute to myofibroblasts; nor transiently expressed αSMA or Zeb1 after heart injury. Instead, expression of αSMA was activated in resident fibroblasts during cardiac fibrosis. Conclusions: Mesenchymal gene expression is activated in cardiac ECs through EndoMT in the developing heart; but ECs do not transdifferentiate into myofibroblasts, nor transiently express some known mesenchymal genes during homeostasis and fibrosis in the adult heart. Resident fibroblasts that are converted to myofibroblasts by activating mesenchymal gene expression are the major contributors to cardiac fibrosis.

Endothelial-Mesenchymal Transition in Cardiovascular Disease

Endothelial-to-mesenchymal transition is a dynamic process in which endothelial cells suppress constituent endothelial properties and take on mesenchymal cell behaviors. To begin the process, endothelial cells loosen their cell-cell junctions, degrade the basement membrane, and migrate out into the perivascular surroundings. These initial endothelial behaviors reflect a transient modulation of cellular phenotype, that is, a phenotypic modulation, that is sometimes referred to as partial endothelial-to-mesenchymal transition. Loosening of endothelial junctions and migration are also seen in inflammatory and angiogenic settings such that endothelial cells initiating endothelial-to-mesenchymal transition have overlapping behaviors and gene expression with endothelial cells responding to inflammatory signals or sprouting to form new blood vessels. Reduced endothelial junctions increase permeability, which facilitates leukocyte trafficking, whereas endothelial migration precedes angiogenic sprouting and neovascularization; both endothelial barriers and quiescence are restored as inflammatory and angiogenic stimuli subside. Complete endothelial-to-mesenchymal transition proceeds beyond phenotypic modulation such that mesenchymal characteristics become prominent and endothelial functions diminish. In proadaptive, regenerative settings the new mesenchymal cells produce extracellular matrix and contribute to tissue integrity whereas in maladaptive, pathologic settings the new mesenchymal cells become fibrotic, overproducing matrix to cause tissue stiffness, which eventually impacts function. Here we will review what is known about how TGF (transforming growth factor) β influences this continuum from junctional loosening to cellular migration and its relevance to cardiovascular diseases.

Heterotopic ossification in mice overexpressing Bmp2 in Tie2+ lineages

Bone morphogenetic protein (Bmp) signaling is critical for organismal development and homeostasis. To elucidate Bmp2 function in the vascular/hematopoietic lineages we generated a new transgenic mouse line in which ectopic Bmp2 expression is controlled by the Tie2 promoter. Tie2CRE/+;Bmp2tg/tg mice develop aortic valve dysfunction postnatally, accompanied by pre-calcific lesion formation in valve leaflets. Remarkably, Tie2CRE/+;Bmp2tg/tg mice develop extensive soft tissue bone formation typical of acquired forms of heterotopic ossification (HO) and genetic bone disorders, such as Fibrodysplasia Ossificans Progressiva (FOP). Ectopic ossification in Tie2CRE/+;Bmp2tg/tg transgenic animals is accompanied by increased bone marrow hematopoietic, fibroblast and osteoblast precursors and circulating pro-inflammatory cells. Transplanting wild-type bone marrow hematopoietic stem cells into lethally irradiated Tie2CRE/+;Bmp2tg/tg mice significantly delays HO onset but does not prevent it. Moreover, transplanting Bmp2-transgenic bone marrow into wild-type recipients does not result in HO, but hematopoietic progenitors contribute to inflammation and ectopic bone marrow colonization rather than to endochondral ossification. Conversely, aberrant Bmp2 signaling activity is associated with fibroblast accumulation, skeletal muscle fiber damage, and expansion of a Tie2+ fibro-adipogenic precursor cell population, suggesting that ectopic bone derives from a skeletal muscle resident osteoprogenitor cell origin. Thus, Tie2CRE/+;Bmp2tg/tg mice recapitulate HO pathophysiology, and might represent a useful model to investigate therapies seeking to mitigate disorders associated with aberrant extra-skeletal bone formation.

Inflammatory and Biomechanical Drivers of Endothelial-Interstitial Interactions in Calcific Aortic Valve Disease

Calcific aortic valve disease is dramatically increasing in global burden, yet no therapy exists outside of prosthetic replacement. The increasing proportion of younger and more active patients mandates alternative therapies. Studies suggest a window of opportunity for biologically based diagnostics and therapeutics to alleviate or delay calcific aortic valve disease progression. Advancement, however, has been hampered by limited understanding of the complex mechanisms driving calcific aortic valve disease initiation and progression towards clinically relevant interventions.

Biology and Biomechanics of the Heart Valve Extracellular Matrix

Heart valves are dynamic structures that, in the average human, open and close over 100,000 times per day, and 3 × 10⁹ times per lifetime to maintain unidirectional blood flow. Efficient, coordinated movement of the valve structures during the cardiac cycle is mediated by the intricate and sophisticated network of extracellular matrix (ECM) components that provide the necessary biomechanical properties to meet these mechanical demands. Organized in layers that accommodate passive functional movements of the valve leaflets, heart valve ECM is synthesized during embryonic development, and remodeled and maintained by resident cells throughout life. The failure of ECM organization compromises biomechanical function, and may lead to obstruction or leaking, which if left untreated can lead to heart failure. At present, effective treatment for heart valve dysfunction is limited and frequently ends with surgical repair or replacement, which comes with insuperable complications for many high-risk patients including aged and pediatric populations. Therefore, there is a critical need to fully appreciate the pathobiology of biomechanical valve failure in order to develop better, alternative therapies. To date, the majority of studies have focused on delineating valve disease mechanisms at the cellular level, namely the interstitial and endothelial lineages. However, less focus has been on the ECM, shown previously in other systems, to be a promising mechanism-inspired therapeutic target. Here, we highlight and review the biology and biomechanical contributions of key components of the heart valve ECM. Furthermore, we discuss how human diseases, including connective tissue disorders lead to aberrations in the abundance, organization and quality of these matrix proteins, resulting in instability of the valve infrastructure and gross functional impairment.

The Endocardium and Heart Valves

Endocardial cells are specialized endothelial cells that, during embryogenesis, form a lining on the inside of the developing heart, which is maintained throughout life. Endocardial cells are an essential source for several lineages of the cardiovascular system including coronary endothelium, endocardial cushion mesenchyme, cardiomyocytes, mural cells, fibroblasts, liver vasculature, adipocytes, and hematopoietic cells. Alterations in the differentiation programs that give rise to these lineages has detrimental effects, including premature lethality or significant structural malformations present at birth. Here, we will review the literature pertaining to the contribution of endocardial cells to valvular, and nonvalvular lineages and highlight critical pathways required for these processes. The lineage differentiation potential of embryonic, and possibly adult, endocardial cells has therapeutic potential in the regeneration of damaged cardiac tissue or treatment of cardiovascular diseases.

Smooth Muscle α-Actin Expression in Mitral Valve Interstitial Cells is Important for Mediating Extracellular Matrix Remodeling

Background: Mitral valve prolapse (MVP) affects 3–6% of the total population including those with connective tissue disorders. Treatment is limited, and patients commonly require surgery which can be impermanent and insuperable. Abnormal prolapse of mitral valve leaflets into the left atria is caused by disturbances to the composition and organization of the extracellular matrix (ECM), that weaken biomechanics. This process, known as myxomatous degeneration is characterized by an abnormal accumulation of proteoglycans, in addition to collagen fiber disruption and elastic fiber fragmentation. The underlying mechanisms that promote myxomatous degeneration to the point of biomechanical failure are unknown, but previous histological studies of end-stage diseased tissue have reported abnormal α-smooth muscle actin (SMA) in a subset of heart valve interstitial cells (VICs); however, the contribution of these abnormal cells to MVP pathogenesis has not been extensively examined. Methods: In vivo and in vitro approaches were used. Mice harboring a Fbn1^C1039G mutation mimic human Marfan Syndrome and develop MVP. Using these mice, temporal and spatial changes in SMA expression relative to myxomatous degeneration were examined using histological techniques. In parallel in vitro experiments, SMA expression was downregulated in primary porcine mitral VICs directly using siRNA, and indirectly using the actin depolymerizing agent Latrunculin A. In addition, the regulation of SMA in VICs by mechanical stiffness was explored relative to ECM remodeling. Results: We show, in mitral valves from Fbn1^C1039G/+ mice, that abnormal increases in SMA expression in VICs are evident during early postnatal stages of disease, prior to significant myxomatous degeneration as indicated at later stages by increased proteoglycans and collagen type I (Col1a1). Furthermore, abnormal SMA expression continues to increase during the course of pathogenesis and is localized to the mid belly region of the mitral valve leaflets from 10 weeks. Using an in vitro approach, we demonstrate that reduced SMA function by direct siRNA or indirect Latrunculin A treatment attenuates proteoglycan and Col1a1 expression in porcine mitral VICs. While upstream, we provide insights to show that SMA is regulated by mechanical tension in VICs to promote changes in ECM homeostasis. Conclusions: Together, our data show that in VICs, SMA, an actin binding protein, is important for mediating ECM remodeling associated with phenotypes observed in myxomatous degeneration, and its expression is regulated by mechanical tension. These novel insights could inform the development of future non-surgical therapeutics to halt the progression of mitral valve degeneration thereby avoiding end-stage prolapse.

The State of Cardiovascular Developmental Biology is Strong - Honoring Dr. Roger Markwald and his Seminal Contributions to the Field

In August 2017, the Cardiovascular Developmental Biology Center (CDBC), together with the "Department of Regenerative Medicine and Cell Biology (RMCB) at the Medical University of South Carolina (MUSC), organized their 13th Annual CDBC Symposium. During this special event, which was organized in collaboration with The Anatomical Record, the unique and important contributions of Dr. Roger Markwald (known to all of us as Roger) to the field of cardiovascular research were celebrated. Fifteen leading investigators in the field presented their ideas and reported results of their studies to an audience that included many familiar faces from Roger's past and present. This group consisted of established investigators from around the world as well as young and upcoming scientists from local institutions. In their presentations, the platform speakers emphasized the significance of Roger's scientific contributions and advice to their professional development and career. In this Special Issue of The Anatomical Record, we assembled a collection of invited papers written by several attendees of the symposium. The issue also contains a number of articles written by colleagues who, for one reason or the other, were not able to attend the meeting, but expressed their desire to contribute to this special "festschrift" of The Anatomical Record in honor and recognition of Roger's amazing career. Anat Rec, 302:14-18, 2019. © 2018 Wiley Periodicals, Inc.

Macrophage lineages in heart valve development and disease

Heterogeneous macrophage lineages are present in the aortic and mitral valves of the heart during development and disease. These populations include resident macrophages of embryonic origins and recruited monocyte-derived macrophages prevalent in disease. Soon after birth, macrophages from haematopoietic lineages are recruited to the heart valves, and bone marrow transplantation studies in mice demonstrate that haematopoietic-derived macrophages continue to invest adult valves. During myxomatous heart valve disease, monocyte-derived macrophages are recruited to the heart valves and they contribute to valve degeneration in a mouse model of Marfan syndrome. Here, we review recent studies of macrophage lineages in heart valve development and disease with discussion of clinical significance and therapeutic applications.

Deficiency of Circulating Monocytes Ameliorates the Progression of Myxomatous Valve Degeneration in Marfan Syndrome

BACKGROUND

Myxomatous valve degeneration (MVD) involves the progressive thickening and degeneration of the heart valves, leading to valve prolapse, regurgitant blood flow, and impaired cardiac function. Leukocytes composed primarily of macrophages have recently been detected in myxomatous valves, but the timing of the presence and the contributions of these cells in MVD progression are not known.

METHODS

We examined MVD progression, macrophages, and the valve microenvironment in the context of Marfan syndrome (MFS) using mitral valves from MFS mice (Fbn1^C1039G/+), gene-edited MFS pigs (FBN1^{Glu433AsnfsX98/+}), and patients with MFS. Additional histological and transcriptomic evaluation was performed by using nonsyndromic human and canine myxomatous valves, respectively. Macrophage ontogeny was determined using MFS mice transplanted with mTomato+ bone marrow or MFS mice harboring RFP (red fluorescent protein)-tagged C-C chemokine receptor type 2 (CCR2) monocytes. Mice deficient in recruited macrophages (Fbn1^C1039G/+;Ccr2^RFP/RFP) were generated to determine the requirements of recruited macrophages to MVD progression.

RESULTS

MFS mice recapitulated histopathological features of myxomatous valve disease by 2 months of age, including mitral valve thickening, increased leaflet cellularity, and extracellular matrix abnormalities characterized by proteoglycan accumulation and collagen fragmentation. Diseased mitral valves of MFS mice concurrently exhibited a marked increase of infiltrating (MHCII+, CCR2+) and resident macrophages (CD206+, CCR2-), along with increased chemokine activity and inflammatory extracellular matrix modification. Likewise, mitral valve specimens obtained from gene-edited MFS pigs and human patients with MFS exhibited increased monocytes and macrophages (CD14+, CD64+, CD68+, CD163+) detected by immunofluorescence. In addition, comparative transcriptomic evaluation of both genetic (MFS mice) and acquired forms of MVD (humans and dogs) unveiled a shared upregulated inflammatory response in diseased valves. Remarkably, the deficiency of monocytes was protective against MVD progression, resulting in a significant reduction of MHCII macrophages, minimal leaflet thickening, and preserved mitral valve integrity.

CONCLUSIONS

All together, our results suggest sterile inflammation as a novel paradigm to disease progression, and we identify, for the first time, monocytes as a viable candidate for targeted therapy in MVD.