Apolipoprotein C3 and Necrotic Core Volume Are Correlated but Also Associated With Future Cardiovascular Events

We aimed to clarify the relationship between apolipoprotein C3 (apo-C3) and vascular composition of lesion plaque in stable coronary disease (SCD) before percutaneous coronary intervention (PCI) and to investigate major adverse cardiovascular events (MACEs) within 4 years. Data of 98 consecutive patients with SCD who underwent PCI between November 1, 2012, and March 10, 2015, were analyzed. Laboratory evaluation and virtual histology-intravascular ultrasound (VH-IVUS) examination of culprit lesions were conducted before PCI. Patients were divided according to the median apo-C3 value into low apo-C3 (≤8.5 mg/dL) and high apo-C3 (>8.5 mg/dL) groups. VH-IVUS data indicated that the percentage of necrotic core volume (%NC) was significantly higher in the high apo-C3 group than in the low apo-C3 group. Moreover, the %NC significantly correlated with the apo-C3 level (R=0.2109, P=0.037). Kaplan–Meier curve analysis revealed that freedom from MACEs decreased more in the high apo-C3 group than in the low apo-C3 group and in the high %NC group than in the low %NC group. Multivariate Cox hazards analysis showed that the %NC and high apo-C3 were independent predictors of 4-year MACEs. Apo-C3 may be a useful marker for future MACEs in patients with SCD after PCI and contribute to %NC growth.

Penumbra in acute ischemic stroke

Acute ischemic stroke is one of the leading causes of disability and death worldwide. The brain tissue adjacent to the central necrotic core was first defined as ischemic penumbra characterized by reduced cerebral blood flow (CBF) with electrical failure but maintained ionic homeostasis and transmembrane electrical potentials. Since then, the evolving concepts of the ischemic penumbra have been proposed based on energy metabolism, CBF thresholds and protein synthesis, which provide insight for the diagnosis and treatment of acute ischemic stroke. This paper summarizes the recent advances in the understanding of ischemic penumbra, from its discovery to the diagnosis methods based on imaging techniques and biomarkers, finally some of the treatments developed. In addition, we discussed future perspectives on therapeutic targets beyond ischemic penumbra to develop a treatment for acute ischemic stroke.

The cellular biology of atherosclerosis with atherosclerotic lesion classification and biomarkers

Background Atherosclerosis is a chronic lipid-driven inflammatory disease with infiltration of low-density lipoprotein and is considered as the pivotal step in plaque formation. The aim of the review is to get into the fine details of pathophysiologic mechanisms responsible for atherosclerosis with atherosclerotic lesion classification. It also provides a summary of current biomarkers other than the traditional risk factors so that new treatment modalities can emerge and reduce the morbidity and mortality associated with atherosclerosis. Main body In the classification of atherosclerosis made by American Heart Association (AHA), AHA Type I lesion is the earliest vascular change described microscopically. AHA Type II lesion is primarily composed of abundant macrophages. AHA Type III lesion is the earliest of progressive lesions, while AHA Type IV lesion consists of an acellular necrotic core. Various biomarkers are implicated in different stages of the pathophysiological mechanism of plaque formation and evolution. C Reactive Protein plays a direct role in promoting the inflammatory component of atherosclerosis. Fibrinogen was demonstrated to be elevated among patients with acute thrombosis. Higher leukocyte count is associated with a greater cardiovascular risk. Cytokines have been implicated in atheroma formation and complications. High rates of protease activated receptor expression are also induced by interleukin-6 secretion in atherosclerotic lesions and areas of vascular tissue injury. Cluster of differentiation 40 receptor and its ligand have been also detected in atherosclerotic plaques. Osteopontin, acidic phosphoprotein, and osteoprotegerin have emerged as novel markers of atherosclerotic plaque composition. There are also overproductions of matrix metalloproteinases in the rupture-prone regions and promote lipid-necrotic core formation in the atherosclerotic plaque. Myeloperoxidase has been proposed as a marker of plaque instability. Oxidized low-density lipoprotein receptor 1 provides a route of entry for oxidized low-density lipoprotein into the endothelium. A human atherosclerotic lesion also expresses lipoprotein-associated phospholipase A2. Short conclusion Atherosclerotic plaques are the battlefield between an unbalanced immune response and lipid accumulation in the intima of arteries. Most of the biomarkers associated with atherosclerosis are indicators of inflammatory response and will also be used for medical purposes.

Non-lipid-rich low attenuation plaque with intraplaque haemorrhage assessed by multimodality imaging: a case report

Background The lipid-rich necrotic core is a major pathological hallmark of acute coronary syndrome. Low attenuation plaque (LAP) on coronary computed tomography angiography (CCTA), defined as plaque CT attenuation of <30 Hounsfield units, is commonly believed to correspond to the lipid component. This report presents a non-lipid-rich LAP with intraplaque haemorrhage of the left main coronary artery (LM), as assessed by CCTA, near-infrared spectroscopy (NIRS), and non-contrast magnetic resonance imaging (MRI) using coronary atherosclerosis T1-weighted characterisation with integrated anatomical reference technique, recently developed by our group. Case Summary A 75-year-old woman presented with chest discomfort on exertion. CCTA revealed severe stenosis of the mid-left circumflex coronary artery and minimal stenosis with a large eccentric LM plaque. The LM lesion had an LAP, with a minimum plaque attenuation of 25 Hounsfield units. On non-contrast T1-weighted MRI, a high-intensity plaque with a plaque-to-myocardium signal intensity ratio of 3.02 was observed within the vessel wall, indicating intraplaque haemorrhage. NIRS categorised the lesion as non-lipid-rich, with a maximum lipid core burden index in 4 mm of 169. Discussion Intraplaque haemorrhage is a key feature of plaque instability, which is different from the lipid-rich necrotic core. Non-contrast T1-weighted MRI is ideal for detecting intraplaque haemorrhage with short T1 values. The imaging findings suggest that LAP on CCTA may represent not only lipid-rich plaques but also intraplaque haemorrhage. MRI provides a unique insight into plaque vulnerability from a different perspective than lipid assessment. Multimodality imaging, including MRI, facilitates the understanding complicated plaque morphologies.

Macrophage LRP1 (Low-Density Lipoprotein Receptor-Related Protein 1) Is Required for the Effect of CD47 Blockade on Efferocytosis and Atherogenesis

Objective: Antibody blockade of the do not eat me signal CD47 enhances efferocytosis and reduces lesion size and necrotic core formation in murine atherosclerosis. TNF (Tumor necrosis factor)-α expression directly enhances CD47 expression, and elevated TNF-α is observed in the absence of the proefferocytosis receptor LRP1 (low-density lipoprotein receptor-related protein 1), a regulator of atherogenesis and inflammation. Thus, we tested the hypothesis that CD47 blockade requires the presence of macrophage LRP1 to enhance efferocytosis, temper TNF-α-dependent inflammation, and limit atherosclerosis. Approach and Results: Mice lacking systemic apoE (apoE −/− ), alone or in combination with the loss of macrophage LRP1 (double knockout), were fed a Western-type diet for 12 weeks while receiving anti-CD47 antibody (anti-CD47) or IgG every other day. In apoE −/− mice, treatment with anti-CD47 reduced lesion size by 25.4%, decreased necrotic core area by 34.5%, and decreased the ratio of free:macrophage-associated apoptotic bodies by 47.6% compared with IgG controls ( P <0.05), confirming previous reports. Double knockout mice treated with anti-CD47 showed no differences in lesion size, necrotic core area, or the ratio of free:macrophage-associated apoptotic bodies compared with IgG controls. In vitro efferocytosis was 30% higher when apoE −/− phagocytes were incubated with anti-CD47 compared with IgG controls ( P <0.05); however, anti-CD47 had no effect on efferocytosis in double knockout phagocytes. Analyses of mRNA and protein showed increased CD47 expression in anti-inflammatory IL (interleukin)-4 treated LRP1 −/− macrophages compared with wild type, but no differences were observed in inflammatory lipopolysaccharide-treated macrophages. Conclusions: The proefferocytosis receptor LRP1 in macrophages is necessary for anti-CD47 blockade to enhance efferocytosis, limit atherogenesis, and decrease necrotic core formation in the apoE −/− model of atherosclerosis.

Spatial relationships of intra-lesion heterogeneity in Mycobacterium tuberculosis microenvironment, replication status, and drug efficacy

A hallmark of Mycobacterium tuberculosis (Mtb) infection with critical impact on disease development and outcome is the marked heterogeneity that exists, spanning differences in lesion types to changes in microenvironment as the infection progresses1-7. A mechanistic understanding of how this heterogeneity affects Mtb growth and treatment efficacy necessitates single bacterium-level studies in the context of intact host tissue architecture; however, such an evaluation has been technically challenging. Here, we exploit fluorescent reporter Mtb strains and the C3HeB/FeJ murine model in an integrated imaging approach to study microenvironment heterogeneity within a single lesion in situ, and analyze how these differences relate to non-uniformity in Mtb replication state, activity, and drug efficacy. We show that the pH and chloride environments differ spatially in a caseous necrotic lesion, with increased acidity and chloride levels in the lesion cuff versus the necrotic core. Conversely, a higher percentage of Mtb in the necrotic core versus the lesion cuff were in an actively replicating state, and correspondingly active in transcription and translation. Finally, examination of three first-line anti-tubercular drugs showed that efficacy of isoniazid was strikingly poor against bacteria in the lesion cuff. Our study reveals spatial relationships of intra-lesion heterogeneity, sheds light on important considerations in the development of anti-tubercular treatment strategies, and establishes a foundational framework for Mtb infection heterogeneity analysis at the single cell level in situ.

NIMG-12. MR SUSCEPTIBILITY IMAGING FOR DETECTION OF TUMOR-ASSOCIATED MACROPHAGES IN GLIOBLASTOMA

BACKGROUND Tumor-associated macrophages (TAMs) are a key component of glioblastoma (GBM) tumor microenvironment. Considering the differential role of different TAM phenotypes in iron metabolism with the M1 phenotype storing intracellular iron, and M2 phenotype releasing iron in the tumor microenvironment, here we investigated non-invasive quantitative susceptibility mapping (QSM) and T2* MRI relaxometry to quantify iron as imaging biomarkers for TAMs in adult patients with GBM. METHODS In this prospective study, 21 adult patients with GBM were enrolled between 2016 to 2019. Patients underwent a 3D single echo gradient echo sequence in addition to standard anatomical sequences on a 3 Tesla MRI. QSM images were reconstructed using the morphology-enabled dipole inversion (MEDI) algorithm. In 3 subjects, ex vivo imaging of surgical specimens was performed on a Bruker 9.4 Tesla 8.9 cm vertical bore MR using 3D multi-echo GRE scans, and R2* (1/T2*) maps were generated by a pixel-wise monoexponential fitting. Each specimen was stained with hematoxylin and eosin, as well as with CD68, CD86, CD206, and L-Ferritin. RESULTS Significant positive correlation was observed between mean susceptibility for the tumor enhancing zone and the L-ferritin positivity percent (r =0.56, p=0.018) and the combination of tumor’s enhancing zone and necrotic core and the L-Ferritin positivity percent (r=0.72; p=0.001). Moreover, the mean susceptibility significantly correlated with positivity percent for CD68 (ρ=0.52, p=0.034) and CD86 (r=0.7 p=0.001), but not for CD206 (ρ=0.09; p=0.7). There was a positive correlation between mean R2* values and CD68 positive cell counts (r =0.6, p=0.016). Similarly, mean R2* values significantly correlated with CD86 (r=0.54, p=0.03) but not with CD206 (r=0.15, p=0.5). High mean susceptibility in the necrotic core was associated with inferior PFS (hazard ratio,4.5, p=0.016). CONCLUSION MR Susceptibility Imaging can quantify the iron content of GBM and provide a non-invasive method for TAM quantification and phenotyping.

Chronic inflammation in psoriasis promotes visceral adipose tissue association with lipid-rich necrotic core through atherogenic myeloid score

Background/Introduction Psoriasis is a chronic inflammatory condition associated with adipose dysfunction and high-risk coronary artery disease features, including non-calcified coronary burden (NCB) and lipid-rich necrotic core (LRNC). Visceral adipose tissue (VAT) is a metabolically-active depot that secretes inflammatory and proatherogenic factors, and is associated with increased NCB. Additionally, an atherogenic myeloid score (AMS) comprised of classical monocytes, low-density granulocytes, and platelets was shown to associate with psoriasis severity and NCB. Purpose To investigate the relationship between VAT and high-risk plaque features and test whether this relationship was potentially mediated by myeloid cells. Methods A cohort of 131 psoriasis patients were included in this study. Atherogenic myeloid score components were calculated using complete blood count data (platelets) and by flow cytometry (monocytes, LDGs). Coronary NCB and LRNC were quantified using QAngio and vascuCAP respectively. VAT was defined as intra-abdominal fat and was quantified using an automated contouring software with abdominal CT scans. Statistical analyses were performed using STATA 12. Results The cohort was middle-aged 50 (42–61) (median (IQR)), and predominantly male (61%). High VAT vs low VAT groups differed significantly in their NCB ((0.910±0.279) vs (1.431±0.517)); p&lt;0.001), (mean ± SD). After adjustment for cardiovascular risk factors, VAT associated with the atherogenic myeloid score (β=0.221, p=0.044), with LRNC (β=0.128, p=0.047), and atherogenic myeloid score associated with LRNC (β=0.161, p=0.003). The relationship of VAT to LRNC was partially mediated by atherogenic myeloid score (25.14%, p=0.029) (Figure 1). Conclusions VAT associated with LRNC, and this relationship was partially mediated by the atherogenic myeloid score. These findings suggest that bioactive VAT may impart risk on coronary artery disease in part through myeloid cells. FUNDunding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Heart, Lung, and Blood Institute Intramural Research Program in Bethesda, Maryland Figure 1. Log-transformed atherogenic myeloid score partially mediates the relationship between VAT and log-transformed LRNC. Adjusted by Framingham Risk Score, PASI score, biologic therapy, statin therapy, type 2 diabetes, hyperlipidemia, and subcutaneous adipose tissue volume. Red arrow: represents indirect effect; Beta: standard regression coefficient.

Macrophages in Atherosclerosis, First or Second Row Players?

Macrophages represent a cell type that has been widely described in the context of atherosclerosis since the earliest studies in the 17th century. Their role has long been considered to be preponderant in the onset and aggravation of atherosclerosis, in particular by participating in the establishment of a chronic inflammatory state by the release of pro-inflammatory cytokines and by uncontrolled engorgement of lipids resulting in the formation of foam cells and later of the necrotic core. However, recent evidence from mouse models using an elegant technique of tracing vascular smooth muscle cells (VSMCs) during plaque development revealed that resident VSMCs display impressive plastic properties in response to an arterial injury, allowing them to switch into different cell types within the plaque, including mesenchymal-like cells, macrophage-like cells and osteochondrogenic-like cells. In this review, we oppose the arguments in favor or against the influence of macrophages versus VSMCs in all stages of atherosclerosis including pre-atherosclerosis, formation of lipid-rich foam cells, development of the necrotic core and the fibrous cap as well as calcification and rupture of the plaque. We also analyze the relevance of animal models for the investigation of the pathophysiological mechanisms of atherosclerosis in humans, and discuss potential therapeutic strategies targeting either VSMCs or macrophage to prevent the development of cardiovascular events. Overall, although major findings have been made from animal models, efforts are still needed to better understand and therefore prevent the development of atherosclerotic plaques in humans.