Mural cell-derived chemokines provide a protective niche to safeguard vascular macrophages and limit chronic inflammation

Plasmacytoid dendritic cells control homeostasis of megakaryopoiesis

Platelet homeostasis is essential for vascular integrity and immune defence1,2. Although the process of platelet formation by fragmenting megakaryocytes (MKs; thrombopoiesis) has been extensively studied, the cellular and molecular mechanisms required to constantly replenish the pool of MKs by their progenitor cells (megakaryopoiesis) remains unclear3,4. Here we use intravital imaging to track the cellular dynamics of megakaryopoiesis over days. We identify plasmacytoid dendritic cells (pDCs) as homeostatic sensors that monitor the bone marrow for apoptotic MKs and deliver IFNα to the MK niche triggering local on-demand proliferation and maturation of MK progenitors. This pDC-dependent feedback loop is crucial for MK and platelet homeostasis at steady state and under stress. pDCs are best known for their ability to function as vigilant detectors of viral infection5. We show that virus-induced activation of pDCs interferes with their function as homeostatic sensors of megakaryopoiesis. Consequently, activation of pDCs by SARS-CoV-2 leads to excessive megakaryopoiesis. Together, we identify a pDC-dependent homeostatic circuit that involves innate immune sensing and demand-adapted release of inflammatory mediators to maintain homeostasis of the megakaryocytic lineage.

The cytoplasmic sensor, the AIM2 inflammasome: A precise therapeutic target in vascular and metabolic diseases

Cardio-cerebrovascular diseases encompass pathological changes in the heart, brain and vascular system, which pose a great threat to health and well-being worldwide. Moreover, metabolic diseases contribute to and exacerbate the impact of vascular diseases. Inflammation is a complex process that protects against noxious stimuli but is also dysregulated in numerous so-called inflammatory diseases, one of which is atherosclerosis. Inflammation involves multiple organ systems and a complex cascade of molecular and cellular events. Numerous studies have shown that inflammation plays a vital role in cardio-cerebrovascular diseases and metabolic diseases. The absent in melanoma 2 (AIM2) inflammasome detects and is subsequently activated by double-stranded DNA in damaged cells and pathogens. With the assistance of the mature effector molecule caspase-1, the AIM2 inflammasome performs crucial biological functions that underpin its involvement in cardio-cerebrovascular diseases and related metabolic diseases: The production of interleukin-1 beta (IL-1β), interleukin-18 (IL-18) and N-terminal pore-forming Gasdermin D fragment (GSDMD-N) mediates a series of inflammatory responses and programmed cell death (pyroptosis and PANoptosis). Currently, several agents have been reported to inhibit the activity of the AIM2 inflammasome and have the potential to be evaluated for use in clinical settings. In this review, we systemically elucidate the assembly, biological functions, regulation and mechanisms of the AIM2 inflammasome in cardio-cerebrovascular diseases and related metabolic diseases and outline the inhibitory agents of the AIM2 inflammasome as potential therapeutic drugs.

Multiomic analyses uncover immunological signatures in acute and chronic coronary syndromes

Acute and chronic coronary syndromes (ACS and CCS) are leading causes of mortality. Inflammation is considered a key pathogenic driver of these diseases, but the underlying immune states and their clinical implications remain poorly understood. Multiomic factor analysis (MOFA) allows unsupervised data exploration across multiple data types, identifying major axes of variation and associating these with underlying molecular processes. We hypothesized that applying MOFA to multiomic data obtained from blood might uncover hidden sources of variance and provide pathophysiological insights linked to clinical needs. Here we compile a longitudinal multiomic dataset of the systemic immune landscape in both ACS and CCS (n = 62 patients in total, n = 15 women and n = 47 men) and validate this in an external cohort (n = 55 patients in total, n = 11 women and n = 44 men). MOFA reveals multicellular immune signatures characterized by distinct monocyte, natural killer and T cell substates and immune-communication pathways that explain a large proportion of inter-patient variance. We also identify specific factors that reflect disease state or associate with treatment outcome in ACS as measured using left ventricular ejection fraction. Hence, this study provides proof-of-concept evidence for the ability of MOFA to uncover multicellular immune programs in cardiovascular disease, opening new directions for mechanistic, biomarker and therapeutic studies.

High-dimensional deconstruction of ovarian cancer at single-cell precision reveals HEBP2 that reshape the TIME and drive carboplatin resistance

BACKGROUND

Single-cell sequencing was employed to analyze the tumor immune microenvironment in ovarian cancer (OC) patients, exploring the evolutionary roles of various macrophage subgroups in OC progression and their correlation with fatty acid metabolism-related genes in contributing to drug resistance.

METHODS

This study aimed to decipher the mechanisms underlying OC chemoresistance (OC-CR) and carboplatin resistance by integrating and analyzing multiple single-cell RNA sequencing datasets from OC patients. The tumor immune microenvironment in OC-CR patients exhibited notable alterations in cellular interactions and the proportions of different immune cell populations, in contrast to the cohort sensitive to OC chemotherapy.

RESULTS

The study demonstrates that the fatty acid-associated gene HEBP2 not only accelerates OC progression but also modifies the immune landscape of OC, driving the polarization from M0_TAM to M2_TAM. This shift results in a diminished efficacy of chemotherapy in OC. Furthermore, both in vitro and in vivo experiments underscored HEBP2's role in boosting the proliferation of OC-resistant cell lines and suppressing apoptosis, thereby facilitating carboplatin resistance.

CONCLUSION

In conclusion, the immune microenvironments of OC-CR significantly differ from those sensitive to chemotherapy, underscoring HEBP2's role in fostering OC resistance. This establishes HEBP2 as a promising prognostic marker and a novel target for therapeutic strategies against OC resistance.

Advances in Clinical Imaging of Vascular Inflammation: A State-of-the-Art Review

Vascular inflammation is a major contributor to cardiovascular disease, particularly atherosclerotic disease, and early detection of vascular inflammation may be key to the ultimate reduction of residual cardiovascular morbidity and mortality. This review paper discusses the progress toward the clinical utility of noninvasive imaging techniques for assessing vascular inflammation, with a focus on coronary atherosclerosis. A discussion of multiple modalities is included: computed tomography (CT) imaging (the major focus of the review), cardiac magnetic resonance, ultrasound, and positron emission tomography imaging. The review covers recent progress in new technologies such as the novel CT biomarkers of coronary inflammation (eg, the perivascular fat attenuation index), new inflammation-specific tracers for positron emission tomography-CT imaging, and others. The strengths and limitations of each modality are explored, highlighting the potential for multi-modality imaging and the use of artificial intelligence image interpretation to improve both diagnostic and prognostic potential for common conditions such as coronary artery disease.

ptx3a+ fibroblast/epicardial cells provide a transient macrophage niche to promote heart regeneration

Macrophages conduct critical roles in heart repair, but the niche required to nurture and anchor them is poorly studied. Here, we investigated the macrophage niche in the regenerating heart. We analyzed cell-cell interactions through published single-cell RNA sequencing datasets and identified a strong interaction between fibroblast/epicardial (Fb/Epi) cells and macrophages. We further visualized the association of macrophages with Fb/Epi cells and the blockage of macrophage response without Fb/Epi cells in the regenerating zebrafish heart. Moreover, we found that ptx3a+ epicardial cells associate with reparative macrophages, and their depletion resulted in fewer reparative macrophages. Further, we identified csf1a expression in ptx3a+ cells and determined that pharmacological inhibition of the csf1a pathway or csf1a knockout blocked the reparative macrophage response. Moreover, we found that genetic overexpression of csf1a enhanced the reparative macrophage response with or without heart injury. Altogether, our studies illuminate a cardiac Fb/Epi niche, which mediates a beneficial macrophage response after heart injury.

Pericyte signaling via soluble guanylate cyclase shapes the vascular niche and microenvironment of tumors

Pericytes and endothelial cells (ECs) constitute the fundamental components of blood vessels. While the role of ECs in tumor angiogenesis and the tumor microenvironment is well appreciated, pericyte function in tumors remains underexplored. In this study, we used pericyte-specific deletion of the nitric oxide (NO) receptor, soluble guanylate cyclase (sGC), to investigate via single-cell RNA sequencing how pericytes influence the vascular niche and the tumor microenvironment. Our findings demonstrate that pericyte sGC deletion disrupts EC-pericyte interactions, impairing Notch-mediated intercellular communication and triggering extensive transcriptomic reprogramming in both pericytes and ECs. These changes further extended their influence to neighboring cancer-associated fibroblasts (CAFs) and tumor-associated macrophages (TAMs) through paracrine signaling, collectively suppressing tumor growth. Inhibition of pericyte sGC has minimal impact on quiescent vessels but significantly increases the vulnerability of angiogenic tumor vessels to conventional anti-angiogenic therapy. In conclusion, our findings elucidate the role of pericytes in shaping the tumor vascular niche and tumor microenvironment and support pericyte sGC targeting as a promising strategy for improving anti-angiogenic therapy for cancer treatment.

Conditional deletion of Ccl2 in smooth muscle cells does not reduce early atherosclerosis in mice

Background and aims

C-C motif chemokine ligand 2 (CCL2) is a pro-inflammatory chemokine important for monocyte recruitment to the arterial wall and atherosclerotic plaques. Global knockout of Ccl2 reduces plaque formation and macrophage content in mice, but the importance of different plaque cell types in mediating this effect has not been resolved. Smooth muscle cells (SMCs) can adopt a potentially pro-inflammatory function with expression of CCL2. The present study aimed to test the hypothesis that SMC-secreted CCL2 is involved in early atherogenesis in mice.

Methods

SMC-restricted Cre recombinase was activated at 6 weeks of age in mice with homozygous floxed or wildtype Ccl2 alleles. Separate experiments in mice lacking the Cre recombinase transgene were conducted to control for genetic background effects. Hypercholesterolemia and atherosclerosis were induced by a tail vein injection of recombinant adeno-associated virus (rAAV) encoding proprotein convertase subtilisin/kexin type 9 (PCSK9) and a high-fat diet for 12 weeks.

Results

Unexpectedly, mice with SMC-specific Ccl2 deletion developed higher levels of plasma cholesterol and larger atherosclerotic plaques with more macrophages compared with wild-type littermates. When total cholesterol levels were incorporated into the statistical analysis, none of the effects on plaque development between groups remained significant. Importantly, changes in plasma cholesterol and atherosclerosis remained in mice lacking Cre recombinase indicating that they were not caused by SMC-specific CCL2 deletion but by effects of the floxed allele or passenger genes.

Conclusions

SMC-specific deficiency of Ccl2 does not significantly affect early plaque development in hypercholesterolemic mice.