Claudia Monaco

Background and Aims: Atherosclerotic plaques are the leading cause of cardiovascular events. Single-cell approaches have identified diverse human plaque cell phenotypes but their spatial distribution and interactions remain unclear. Here, intercellular communication patterns in human plaque microenvironments were mapped to reveal novel targets to prevent atherosclerotic events. Methods: Spatial transcriptomics (Visium, 10x) from 13 carotid plaques, and single-cell transcriptomics (cells = 51 981) were used to analyse cell phenotypes, cell trajectories, and intercellular communications. Cells contributing to plaque stability were explored using deconvolution of plaque bulk RNA-seq data (n = 78), histology, and survival analyses. Key cells and pathways were validated in apolipoprotein E (Apoe)−/− mice and in vitro. Genome-wide association study enrichment analyses were conducted using summary statistics of atherosclerotic diseases. LINCS L1000 data were used to explore drug repurposing. Results: A fibroblast-like vascular smooth muscle cell (VSMC) phenotype associated with extracellular matrix formation pathways (validated in Apoe−/− mice) emerged as a key regulator of intra-plaque ligand-receptor signalling, in particular in the cap region. A higher proportion of fibroblast-like VSMCs was found in asymptomatics, associated with stable plaque features and predicted a lower risk of future events. Genes specific to this VSMC phenotype were enriched in coronary artery disease and myocardial infarction. Finally, compounds, which could induce key marker genes were identified and validated in vitro. Conclusions: This study provides the first comprehensive spatial transcriptomics map of cell communication in human plaque microenvironments. A pivotal role of a fibroblast-like VSMC, orchestrating intraplaque cell signalling and contributing to plaque stability, was identified. Targeting these cells might present promising novel avenues for therapies.

Background: Bacterial DNA from the oral cavity, respiratory tract, gut, and skin has been detected in atherosclerotic plaques, suggesting a role in chronic inflammation linked to atherosclerosis. Chronic bacterial infections often form biofilms resistant to antibiotics and immune detection, giving rise to a new generation of virulent bacteria in suitable conditions. This study explores the role of the immune system in bacterial‐induced inflammation of atherosclerotic plaques. Methods: Coronary plaques from 121 sudden death victims and endarterectomy samples from 96 surgical patients were analyzed using bacterial real‐time quantitative polymerase chain reaction, immunohistochemistry, and genome‐wide expression analysis. TLR (toll‐like receptor) signaling was examined in bacterial‐activated TLR cell lines. Results: Of the bacteria detected, oral viridans group streptococcal DNA was the most common, being found in 42.1% of coronary plaques and 42.9% of endarterectomies. Immunopositivity for viridans streptococci correlated with severe atherosclerosis ( P P =0.021) or myocardial infarction ( P =0.042). Viridans streptococci colonized the core of the atheroma as a biofilm unrecognized by macrophages of the innate immune system. In contrast, immunopositive streptococci that appeared to have originated from the biofilm infiltrated the ruptured fibrous cap of the atheroma in endarterectomy samples and coronary plaques and were detected by pattern‐recognizing receptors and coexpressed with the adaptive immune response. Among the viridans streptococcal strains, TLR2 was the most activated bacterial‐signaling pathway. Genome‐wide expression analysis of endarterectomy samples showed upregulation of bacterial recognition pathways. Conclusions: Latent chronic bacterial inflammation evades immune detection and may contribute to the pathogenesis of complicated atherosclerotic plaques and fatal myocardial infarction.

Cardiovascular disease is the global #1 cause of mortality and morbidity. The majority of cardiovascular diseases is caused by atherosclerosis, a lipid-driven, inflammatory disease of the middle- and large-sized arteries. The disease is characterized by the formation of atherosclerotic plaques throughout the arterial tree. Over the years, insights into the pathogenesis of atherosclerosis have shifted from a ‘lipid-driven’ model to a ‘response-to-injury’ perspective, and more recently to a ‘lipid-driven inflammatory disease’ viewpoint. We are now aware that a network of multiple immune cell-types and -subsets of the innate and adaptive immune system inhabit our arteries. Intricate interactions between these immune cellsubsets, non-immune cells, and local environmental substances such as lipids, cell debris and calcium cause a fluidic balance of pro-inflammatory and regulatory responses. A dysregulation of this balance towards a pro-inflammatory milieu drives atherosclerotic disease progression. Although we have acknowledged that atherosclerosis is an inflammatory disease, state-of-theart treatments are still based on lipid lowering, anti-hypertensive and lifestyle-changing strategies. In the past decade, clinical phase I, II and III trials targeting the immune system revealed that patients tolerate immunotherapy, show decreased inflammation and/or had a reduction in cardiovascular endpoints. However, the search for novel immunotherapeutic targets and treatment regimens as well as stratification of patients who would benefit from such treatments to combat atherosclerotic cardiovascular disease is only just beginning. In this review article, we will highlight the newest insights on the different cell subsets and components of the immune system in atherosclerosis and elaborate on current and future immunotherapeutics to treat atherosclerotic cardiovascular disease.

Type 2 diabetes is associated with cardiovascular disease, possibly due to impaired vascular fibrous repair. Yet, the mechanisms are elusive. Here, we investigate alterations in the fibrous repair processes in type 2 diabetes atherosclerotic plaque extracellular matrix by combining multi-omics from the human Carotid Plaque Imaging Project cohort and functional studies. Plaques from type 2 diabetes patients have less collagen. Interestingly, lower levels of transforming growth factor-ß distinguish type 2 diabetes plaques and, in these patients, lower levels of fibrous repair markers are associated with cardiovascular events. Transforming growth factor-ß2 originates mostly from contractile vascular smooth muscle cells that interact with synthetic vascular smooth muscle cells in the cap, leading to collagen formation and vascular smooth muscle cell differentiation. This is regulated by free transforming growth factor-ß2 which is affected by hyperglycemia. Our findings underscore the importance of transforming growth factor-ß2-driven fibrous repair in type 2 diabetes as an area for future therapeutic strategies.

CCL17 is produced by conventional dendritic cells, signals through CCR4 on regulatory T (T_reg) cells and drives atherosclerosis by suppressing T_reg functions through yet undefined mechanisms. Here we show that conventional dendritic cells from CCL17-deficient mice display a pro-tolerogenic phenotype and transcriptome that is not phenocopied in mice lacking its cognate receptor CCR4. In the plasma of CCL17-deficient mice, CCL3 was the only decreased cytokine/chemokine. We found that CCL17 signaled through CCR8 as an alternate high-affinity receptor, which induced CCL3 expression and suppressed T_reg functions in the absence of CCR4. Genetic ablation of CCL3 and CCR8 in CD4⁺ T cells reduced CCL3 secretion, boosted FoxP3⁺ T_reg numbers and limited atherosclerosis. Conversely, CCL3 administration exacerbated atherosclerosis and restrained T_reg differentiation. In symptomatic versus asymptomatic human carotid atheroma, CCL3 expression was increased, whereas FoxP3 expression was reduced. Together, we identified a non-canonical chemokine pathway whereby CCL17 interacts with CCR8 to yield a CCL3-dependent suppression of atheroprotective T_reg cells.