Activated human valvular interstitial cells sustain interleukin-17 production to recruit neutrophils in infective endocarditis

Single-cell analysis reveals the loss of FABP4-positive proliferating valvular endothelial cells relates to functional mitral regurgitation

BACKGROUND

Functional mitral regurgitation (MR) is a common form of mitral valve dysfunction that often persists even after surgical intervention, requiring reoperation in some cases. To advance our understanding of the pathogenesis of functional MR, it is crucial to characterize the cellular composition of the mitral valve leaflet and identify molecular changes in each cell subtype within the mitral valves of MR patients. Therefore, we aimed to comprehensively examine the cellular and molecular components of mitral valves in patients with MR.

METHODS

We conducted a single-cell RNA sequencing (scRNA-seq) analysis of mitral valve leaflets extracted from six patients who underwent heart transplantation. The cohort comprised three individuals with moderate-to-severe functional MR (MR group) and three non-diseased controls (NC group). Bioinformatics was applied to identify cell types, delineate cell functions, and explore cellular developmental trajectories and interactions. Key findings from the scRNA-seq analysis were validated using pathological staining to visualize key markers in the mitral valve leaflets. Additionally, in vitro experiments with human primary valvular endothelial cells were conducted to further support our results.

RESULTS

Our study revealed that valve interstitial cells are critical for adaptive valve remodelling, as they secrete extracellular matrix proteins and promote fibrosis. We discovered an abnormal decrease in a subpopulation of FABP4 (fatty acid binding protein 4)-positive proliferating valvular endothelial cells. The trajectory analysis identifies this subcluster as the origin of VECs. Immunohistochemistry on the expanded cohort showed a reduction of FABP4-positive VECs in patients with functional MR. Intervention experiments with primary cells indicated that FABP4 promotes proliferation and migration in mitral valve VECs and enhances TGFβ-induced differentiation.

CONCLUSIONS

Our study presented a comprehensive assessment of the mitral valve cellular landscape of patients with MR and sheds light on the molecular changes occurring in human mitral valves during functional MR. We found a notable reduction in the proliferating endothelial cell subpopulation of valve leaflets, and FABP4 was identified as one of their markers. Therefore, FABP4 positive VECs served as proliferating endothelial cells relates to functional mitral regurgitation. These VECs exhibited high proliferative and differentiative properties. Their reduction was associated with the occurrence of functional MR.

Novel putative biomarkers for infective endocarditis by serum proteomic analysis: a comprehensive review of literature

Infective endocarditis (IE) is a challenging condition with high mortality. Prompt detection of IE has become essential for early and immediate management. The authors aimed to comprehensively review the existing literature on novel putative biomarkers for IE through serum proteomic analysis. The literature reveals high levels of N-terminal-pro-B-type natriuretic peptide (NT-proBNP) levels in IE with staphylococcal etiology, valvular lesions, and when combined with cardiac troponin I (cTnI), had a more significant value for risk stratification. A higher pro-ADM level, copeptin, NT-proBNP, and the monocyte-to-high-density lipoprotein cholesterol ratio (MHR) all impacted mortality during the hospital stay. The biomarker matrix metalloproteinase-9 was utilized to predict new-onset embolic events in patients, thus serving as a predictive marker. Procalcitonin was an important diagnostic marker in IE complicated with severe infection. Interleukin-6 (IL-6), Interleukin-8 (IL-8), Interferon-γ, cTnI, and NT-proBNP were also discovered to be useful as prognostic indicators. Early diagnosis and appropriate treatment are possible using antiphospholipid antibodies as a diagnostic test for definite IE. It is also concluded that antineutrophilic cytoplasmic antibody positive individuals with IE had a lengthier hospital stay. These noninvasive biomarkers can identify patients at risk and provide appropriate and early clinical management. NT-proBNP, Cystatin C, troponins, IL-6, IL-8, S100A11, and AQP9 are examples of possible markers that appear promising for further research. In conclusion, large-scale validation studies should study these biomarkers further to establish their use in clinical settings.

Profiling Genome-Wide DNA Methylation Patterns in Human Aortic and Mitral Valves

Cardiac valves exhibit highly complex structures and specialized functions that include dynamic interactions between cells, extracellular matrix (ECM) and their hemodynamic environment. Valvular gene expression is tightly regulated by a variety of mechanisms including epigenetic factors such as histone modifications, RNA-based mechanisms and DNA methylation. To date, methylation fingerprints of non-diseased human aortic and mitral valves have not been studied. In this work we analyzed the differential methylation profiles of 12 non-diseased aortic and mitral valve tissue samples (in matched pairs). Analysis of methylation data [reduced representation bisulfite sequencing (RRBS)] of 16,101 promoters genome-wide revealed 584 differentially methylated (DM) promoters, of which 13 were reported in endothelial mesenchymal trans-differentiation (EMT), 37 in aortic and mitral valve disease and 7 in ECM remodeling. Both functional classification as well as network analysis showed that the genes associated with the DM promoters were enriched for WNT-, Cadherin-, Endothelin-, PDGF-, HIF-1 and VEGF- signaling implicated in valvular physiology and pathophysiology. Additional enrichment was detected for TGFB-, NOTCH- and Integrin- signaling involved in EMT as well as ECM remodeling. This data provides the first insight into differential regulation of human aortic and mitral valve tissue and identifies candidate genes linked to DM promoters. Our work will improve the understanding of valve biology, valve tissue engineering approaches and contributes to the identification of relevant drug targets.

CCR6 Deficiency Increases Infarct Size after Murine Acute Myocardial Infarction

Ischemia-reperfusion injury after the reopening of an occluded coronary artery is a major cause of cardiac damage and inflammation after acute myocardial infarction. The chemokine axis CCL20-CCR6 is a key player in various inflammatory processes, including atherosclerosis; however, its role in ischemia-reperfusion injury has remained elusive. Therefore, to gain more insight into the role of the CCR6 in acute myocardial infarction, we have studied cardiac injury after transient ligation of the left anterior descending coronary artery followed by reperfusion in Ccr6-/- mice and their respective C57Bl/6 wild-type controls. Surprisingly, Ccr6-/- mice demonstrated significantly reduced cardiac function and increased infarct sizes after ischemia/reperfusion. This coincided with a significant increase in cardiac inflammation, characterized by an accumulation of neutrophils and inflammatory macrophage accumulation. Chimeras with a bone marrow deficiency of CCR6 mirrored this adverse Ccr6-/- phenotype, while cardiac injury was unchanged in chimeras with stromal CCR6 deficiency. This study demonstrates that CCR6-dependent (bone marrow) cells exert a protective role in myocardial infarction and subsequent ischemia-reperfusion injury, supporting the notion that augmenting CCR6-dependent immune mechanisms represents an interesting therapeutic target.

Neutrophil gelatinase-associated lipocalin: a potential predictor of embolic events in endocarditis

BACKGROUND

As the complication of infective endocarditis (IE), embolic events (EE) are associated with increased mortality and morbidity. However, there are no reliable indicators to predict embolism. The aim of this study was to evaluate neutrophil gelatinase-associated lipocalin (NGAL) as a biomarker to identify IE patients at high risk of embolism.

METHODS

We conducted a prospective observational study of IE patients from January 2018 to December 2020. Plasma NGAL levels were measured in 88 IE patients (37 patients with EE and 51 patients without EE), 91 noninfectious heart valve disease (HVD) patients, and 20 healthy blood donors by ELISA. Native valve tissue was obtained from 16 IE patients and 16 HVD patients. Western blot and immunohistochemical staining were performed to detect NGAL and matrix metalloproteinas-9 (MMP-9).

RESULTS

Higher levels of NGAL were observed in IE patients than HVD patients (P<0.001) or healthy blood donors (P<0.01). In addition, NGAL levels were higher in IE patients with EE compared to those without EE (P<0.001). Receiver operating characteristic analysis demonstrated that NGAL acted as a potential EE predictor with the cutoff value of 166.78 ng/ml. IE patients with higher NGAL levels were significantly related to more severe native valve morphologic changes. NGAL was co-localized with MMP-9, and their expression in the valves of IE patients was higher than those of HVD patients.

CONCLUSIONS

NGAL is a potential predictor of EE in IE. This may be attributed to its potency of increasing the proteolytic activity of MMP-9, which leads to valve morphologic impairment.

The Genetic Control of the Rheumatic Heart: Closing the Genotype-Phenotype Gap

Rheumatic heart disease (RHD) is a heritable inflammatory condition characterized by carditis, arthritis, and systemic disease. Although remaining neglected, the last 3 years has seen some promising advances in RHD research. Whilst it is clear that RHD can be triggered by recurrent group A streptococcal infections, the mechanisms driving clinical progression are still poorly understood. This review summarizes our current understanding of the genetics implicated in this process and the genetic determinants that predispose some people to RHD. The evidence demonstrating the importance of individual cell types and cellular states in delineating causal genetic variants is discussed, highlighting phenotype/genotype correlations where possible. Genetic fine mapping and functional studies in extreme phenotypes, together with large-scale omics studies including genomics, transcriptomics, epigenomics, and metabolomics, are expected to provide new information not only on RHD but also on the mechanisms of other autoimmune diseases and facilitate future clinical translation.

Neutrophil-Lymphocyte Ratio in Predicting Infective Endocarditis: A Case-Control Retrospective Study

Background

Infective endocarditis (IE) is a complex infectious disease with high morbidity and mortality. The inflammation mechanism of IE is a complex network including interactions of inflammatory cytokines and other components of host response. As an important inflammation marker, the prediction ability of neutrophil-to-lymphocyte ratio (NLR) in IE deserves further investigation.

Methods

NLR values were measured and compared between IE patients and healthy controls, good and bad clinical outcome groups. The receiver operating characteristic curves (ROCs) of NLR and cut-off values were measured in IE patients, pathogen-subgroups, and different clinical outcome groups.

Results

There were 678 IE patients and 2520 healthy controls enrolled in our study. The number of good and bad clinical outcome patients was 537 and 141, respectively. The value of NLR was significantly higher in IE patients than healthy controls (6.29 ± 9.36 vs. 1.87 ± 0.34, p < 0.001), and the area under the ROC (AUC) was 0.817 (95% CI (0.794, 0.839), p < 0.001). The critical value of NLR for diagnosis of IE was 2.68, with a sensitivity of 69%, and a specificity of 88%. The value of NLR was significantly higher in bad clinical outcome patients than in good clinical outcome patients (5.8 ± 6.02 vs. 3.62 ± 2.61, p < 0.001). The critical value of NLR to predict the outcome of IE was 5.557, with a sensitivity of 39.0% and a specificity of 85.3%.

Conclusions

NLR is a predictive marker for IE patients, especially in Gram-negative bacteria and Gram-positive bacteria-infected IE patients. NLR also can predict the outcome of IE. Early detecting NLR upon admission may assist in early diagnosis and risk stratification of patients with IE.

IL-21 promotes osteoblastic differentiation of human valvular interstitial cells through the JAK3/STAT3 pathway

Objectives: This study amied to whether IL-21 promotes osteoblast transdifferentiation of cultured human Valvular interstitial cells (VICs). Methods: We first confirmed that IL-21 alters gene expression between CAVD aortic valve tissue and normal samples by immunohistochemistry, qPCR, and western blotting. VICs were cultured and treated with IL-21. Gene and protein expression levels of the osteoblastic markers ALP and Runx2, which can be blocked by specific JAK3 inhibitors and/or siRNA of STAT3, were measured. Results: IL-21 expression was upregulated in calcified aortic valves and promotes osteogenic differentiation of human VICs. IL-21 accelerated VIC calcification through the JAK3/STAT3 pathway. Conclusion: Our data suggest that IL-21 is a key factor in valve calcification and a promising candidate for targeted therapeutics for CAVD.

Adjunctive dabigatran therapy improves outcome of experimental left-sided Staphylococcus aureus endocarditis

Background

Staphylococcus aureus is the most frequent and fatal cause of left-sided infective endocarditis (IE). New treatment strategies are needed to improve the outcome. S. aureus coagulase promotes clot and fibrin formation. We hypothesized that dabigatran, could reduce valve vegetations and inflammation in S. aureus IE.

Methods

We used a rat model of severe aortic valve S. aureus IE. All infected animals were randomized to receive adjunctive dabigatran (10 mg/kg b.i.d., n = 12) or saline (controls, n = 11) in combination with gentamicin. Valve vegetation size, bacterial load, cytokine, cell integrins expression and peripheral platelets and neutrophils were assessed 3 days post-infection.

Results

Adjunctive dabigatran treatment significantly reduced valve vegetation size compared to controls (p< 0.0001). A significant reduction of the bacterial load in aortic valves was seen in dabigatran group compared to controls (p = 0.02), as well as expression of key pro-inflammatory markers keratinocyte-derived chemokine, IL-6, ICAM-1, TIMP-1, L-selectin (p< 0.04). Moreover, the dabigatran group had a 2.5-fold increase of circulating platelets compared to controls and a higher expression of functional and activated platelets (CD62p⁺) unbound to neutrophils.

Conclusion

Adjunctive dabigatran reduced the vegetation size, bacterial load, and inflammation in experimental S. aureus IE.

Low efficacy of tobramycin in experimental Staphylococcus aureus endocarditis

The empiric treatment of infective endocarditis (IE) varies widely and, in some places, a regimen of penicillin in combination with an aminoglycoside is administered. The increasing incidence of Staphylococcus aureus IE, poor tissue penetration by aminoglycosides and low frequency of penicillin-susceptible S. aureus may potentially lead to functional tobramycin monotherapy. Therefore, this study aimed to evaluate tobramycin monotherapy in an experimental S. aureus IE rat model. Catheter-induced IE at the aortic valves were established with S. aureus (NCTC 8325-4) and rats were randomised into untreated (n = 22) or tobramycin-treated (n = 13) groups. The treatment group received tobramycin once-daily. Animals were evaluated at 1 day post infection (DPI), 2 DPI or 3 DPI. Quantitative bacteriology and cytokine expression were measured for valves, myocardium and serum. A decrease of bacterial load was observed in valves and the spleens of the treated (n = 6) compared to the untreated group at 2 DPI (n = 8) (p ≤ 0.02 and p ≤ 0.01, respectively), but not at 3 DPI (n = 7). Quantitative bacteriology in the myocardium was not different between the groups. Keratinocyte-derived chemokine (KC) in the aortic valves was significantly reduced at 2 DPI in the tobramycin-treated group (p ≤ 0.03). However, the expression of interleukin (IL)-1b, IL-6 and granulocyte-colony stimulating factor (G-CSF) in the valves was not different between the two groups. In the myocardium, a significant reduction in IL-1b was observed at 2 DPI (p ≤ 0.001) but not at 3 DPI. Tobramycin as functional monotherapy only reduced bacterial load and inflammation transiently, and was insufficient in most cases of S. aureus IE.