Macrophages marc(o) the difference in liver inflammation?

Miyamoto et al. report that Marco expression demarcates a population of IL-10-expressing immunosuppressive Kupffer cells (KCs) that are preferentially peri-portally located in the mouse liver, and which limit bacterial dissemination and liver inflammation.

Spatial proteogenomics reveals distinct and evolutionarily conserved hepatic macrophage niches.

The liver is the largest solid organ in the body, yet it remains incompletely characterized. Here we present a spatial proteogenomic atlas of the healthy and obese human and murine liver combining single-cell CITE-seq, single-nuclei sequencing, spatial transcriptomics, and spatial proteomics. By integrating these multi-omic datasets, we provide validated strategies to reliably discriminate and localize all hepatic cells, including a population of lipid-associated macrophages (LAMs) at the bile ducts. We then align this atlas across seven species, revealing the conserved program of bona fide Kupffer cells and LAMs. We also uncover the respective spatially resolved cellular niches of these macrophages and the microenvironmental circuits driving their unique transcriptomic identities. We demonstrate that LAMs are induced by local lipid exposure, leading to their induction in steatotic regions of the murine and human liver, while Kupffer cell development crucially depends on their cross-talk with hepatic stellate cells via the evolutionarily conserved ALK1-BMP9/10 axis.

Hepatic Macrophage Responses in Inflammation, a Function of Plasticity, Heterogeneity or Both?

With the increasing availability and accessibility of single cell technologies, much attention has been given to delineating the specific populations of cells present in any given tissue. In recent years, hepatic macrophage heterogeneity has also begun to be examined using these strategies. While previously any macrophage in the liver was considered to be a Kupffer cell (KC), several studies have recently revealed the presence of distinct subsets of hepatic macrophages, including those distinct from KCs both under homeostatic and non-homeostatic conditions. This heterogeneity has brought the concept of macrophage plasticity into question. Are KCs really as plastic as once thought, being capable of responding efficiently and specifically to any given stimuli? Or are the differential responses observed from hepatic macrophages in distinct settings due to the presence of multiple subsets of these cells? With these questions in mind, here we examine what is currently understood regarding hepatic macrophage heterogeneity in mouse and human and examine the role of heterogeneity vs plasticity in regards to hepatic macrophage responses in settings of both pathogen-induced and sterile inflammation.

Germ-Free Mice Exhibit Mast Cells With Impaired Functionality and Gut Homing and Do Not Develop Food Allergy.

Background: Mucosal mast cells (MC) are key players in IgE-mediated food allergy (FA). The evidence on the interaction between gut microbiota, MC and susceptibility to FA is contradictory. Objective: We tested the hypothesis that commensal bacteria are essential for MC migration to the gut and their maturation impacting the susceptibility to FA. Methods: The development and severity of FA symptoms was studied in sensitized germ-free (GF), conventional (CV), and mice mono-colonized with L. plantarum WCFS1 or co-housed with CV mice. MC were phenotypically and functionally characterized. Results: Systemic sensitization and oral challenge of GF mice with ovalbumin led to increased levels of specific IgE in serum compared to CV mice. Remarkably, despite the high levels of sensitization, GF mice did not develop diarrhea or anaphylactic hypothermia, common symptoms of FA. In the gut, GF mice expressed low levels of the MC tissue-homing markers CXCL1 and CXCL2, and harbored fewer MC which exhibited lower levels of MC protease-1 after challenge. Additionally, MC in GF mice were less mature as confirmed by flow-cytometry and their functionality was impaired as shown by reduced edema formation after injection of degranulation-provoking compound 48/80. Co-housing of GF mice with CV mice fully restored their susceptibility to develop FA. However, this did not occur when mice were mono-colonized with L. plantarum. Conclusion: Our results demonstrate that microbiota-induced maturation and gut-homing of MC is a critical step for the development of symptoms of experimental FA. This new mechanistic insight into microbiota-MC-FA axis can be exploited in the prevention and treatment of FA in humans.

Toxoplasma gondii tachyzoite-extract acts as a potent immunomodulator against allergic sensitization and airway inflammation.

Epidemiological and experimental studies have shown an inverse relationship between infections with certain parasites and a reduced incidence of allergic diseases. We and others have shown that infection with Toxoplasma gondii prevents the development of allergy in mice. To establish whether this beneficial effect could be recapitulated by soluble products of this parasite, we tested an extract derived from T. gondii tachyzoites. Immunization of BALB/c mice with tachyzoites lysate antigen (TLA) elicited mixed Th1/Th2 responses. When TLA was applied together with the sensitizing ovalbumin (OVA), the development of allergic airway inflammation was reduced, with decreased airway hyperresponsiveness associated with reduced peribronchial and perivascular cellular infiltration, reduced production of OVA-specific Th2 cytokines in lungs and spleens and reduced levels of serum OVA-specific IgG1 as well as IgE-dependent basophil degranulation. Of note, TLA retained its immunomodulatory properties, inducing high levels of IL-6, TNFα, IL-10 and IL-12p70 in bone marrow-derived dendritic cells after heat-inactivation or proteinase K-treatment for disruption of proteins, but not after sodium metaperiodate-treatment that degrades carbohydrate structures, suggesting that carbohydrates may play a role in immunomodulatory properties of TLA. Here we show that extracts derived from parasites may replicate the benefits of parasitic infection, offering new therapies for immune-mediated disorders.

Detection of coronary artery disease in postmenopausal women: the significance of integrated stress imaging tests in a 4-year prognostic study.

BACKGROUND: The present prospective study investigated whether a combined approach integrating two different stress imaging modalities may improve the diagnostic accuracy and prognostic impact of non-invasive coronary artery disease (CAD) tests in postmenopausal women. In women non-invasive tests for detecting CAD are less accurate than in men, leading to a high proportion of unnecessary coronary angiographies (CAs). METHODS: 424 consecutive postmenopausal women (mean 61 ± 7 years, mean Reynolds Risk Score 13 ± 3 %) with symptoms suggestive of CAD were prospectively included and followed up for 4 ± 1 years. Each patient underwent CA, stress cardiovascular magnetic resonance (CMR) by adenosine, dobutamine stress echocardiography (DSE) and single-photon emission computed tomography (SPECT) within 7 ± 3 days. RESULTS: Anatomically obstructive coronary artery disease (≥50 % diameter stenosis) was present in 157 women (37 %). The combination of two stress imaging modalities significantly increased the positive predictive values (PPV) to 90 ± 3, 88 ± 3 and 87 ± 2 % for CMR/DSE, DSE/SPECT and CMR/SPECT, respectively. For patients with negative combined test results, the survival analysis showed a 4-year cumulative event-free survival rate of 96-97 % for all combinations. This new approach is cost effective due to the resulting reduction in unnecessary CAs (with potential side effects and corresponding therapies) as well as reducing hospitalization time. CONCLUSIONS: In symptomatic postmenopausal women, combination of two negative stress imaging results significantly increases the PPV for detection of CAD and excludes future cardiovascular events with high accuracy. This approach may be applied to improve the prognostic precision of non-invasive CAD tests and to avoid unnecessary CAs.

Glutathione-S-transferase: a minor allergen in birch pollen due to limited release from hydrated pollen.

BACKGROUND: Recently, a protein homologous to glutathione-S-transferases (GST) was detected in prominent amounts in birch pollen by proteomic profiling. As members of the GST family are relevant allergens in mites, cockroach and fungi we investigated the allergenic relevance of GST from birch (bGST). METHODOLOGY: bGST was expressed in Escherichia coli, purified and characterized by mass spectrometry. Sera from 217 birch pollen-allergic patients were tested for IgE-reactivity to bGST by ELISA. The mediator-releasing activity of bGST was analysed with IgE-loaded rat basophil leukaemia cells (RBL) expressing human FcεRI. BALB/c mice were immunized with bGST or Bet v 1. Antibody and T cell responses to either protein were assessed. IgE-cross-reactivity between bGST with GST from house dust mite, Der p 8, was studied with murine and human sera in ELISA. The release kinetics of bGST and Bet v 1 from birch pollen were assessed in water, simulated lung fluid, 0.9% NaCl and PBS. Eluted proteins were quantified by ELISA and analysed by immunoblotting. PRINCIPLE FINDINGS: Only 13% of 217 birch pollen-allergic patients showed IgE-reactivity to bGST. In RBL assays bGST induced mediator release. Immunization of mice with bGST induced specific IgE and a Th2-dominated cellular immune response comparably to immunization with Bet v 1. bGST did not cross-react with Der p 8. In contrast to Bet v 1, only low amounts of bGST were released from pollen grains upon incubation in water and the different physiological solutions. CONCLUSION/SIGNIFICANCE: Although bGST is abundant in birch pollen, immunogenic in mice and able to induce mediator release from effector cells passively loaded with specific IgE, it is a minor allergen for birch pollen-allergic patients. We refer this discrepancy to its limited release from hydrated pollen. Hence, bGST is an example demonstrating that allergenicity depends mainly on rapid elution from airborne particles.

Myocardial deformation imaging by two-dimensional speckle-tracking echocardiography for prediction of global and segmental functional changes after acute myocardial infarction: a comparison with late gadolinium enhancement cardiac magnetic resonance.

BACKGROUND: Myocardial deformation analysis by speckle-tracking echocardiography (STE) has been shown to accurately predict viability in patients with chronic ischemic left ventricular (LV) dysfunction. The aim of this study was to evaluate two-dimensional STE for the prediction of global and segmental LV functional changes after acute myocardial infarction (AMI) in comparison with late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR). METHODS: In 93 patients (mean age, 60 ± 11 years) with first AMIs (55 with ST-segment elevation myocardial infarctions and 38 with non-ST-segment elevation myocardial infarctions) treated with acute percutaneous coronary intervention, global peak longitudinal strain was determined to describe global function by STE, and peak systolic circumferential and longitudinal strain was determined for segmental function analysis. LGE CMR was performed to define the amounts of global and segmental myocardial scar. STE and LGE CMR were performed within 48 hours of AMI. At 6-month follow-up, transthoracic echocardiography was repeated to determine global und segmental LV recovery and adverse LV remodeling (increase in end-systolic volume > 15%). RESULTS: Accuracy to predict global functional improvement as well as LV remodeling at 6-month follow-up after AMI was similar for STE and LGE CMR (areas under the curve, 0.715 vs 0.729 [P = .8830] and 0.806 vs 0.824 [P = .7141], respectively). Peak systolic circumferential strain < -14.2% had sensitivity of 71.6% and specificity of 58.1% to predict segmental functional improvement. Compared with LGE CMR, the predictive accuracy of transmural STE for segmental functional improvement at 6-month follow-up was lower (area under the curve, 0.788 vs 0.668; P = .0001). Predictive accuracy for segmental functional improvement could be improved by analysis of endocardial circumferential strain (area under the curve, 0.700 vs 0.668 for transmural speckle-tracking echocardiographic analysis; P = .0023). CONCLUSIONS: Two-dimensional STE allows the prediction of global functional recovery as well as LV remodeling after AMI with accuracy comparable with that of LGE CMR. Accuracy to predict segmental functional recovery using transmural deformation analysis by two-dimensional STE is inferior compared with LGE CMR but can be improved by a layer-specific analysis of endocardial deformation.

Layer-specific analysis of myocardial deformation for assessment of infarct transmurality: comparison of strain-encoded cardiovascular magnetic resonance with 2D speckle tracking echocardiography.

AIMS: Separate analysis of endocardial and epicardial myocardial layer deformation has become possible using strain-encoded cardiovascular magnetic resonance (SENC) and 2D-dimensional speckle tracking echocardiography (Echo). This study evaluated and compared both modalities for the assessment of infarct transmurality as defined by late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR). METHODS AND RESULTS: In 29 patients (age 62.4 ± 11.7 years, 23 male) with ischaemic cardiomyopathy, SENC using 1.5 T CMR and Echo were performed. Peak circumferential systolic strain of the endocardial and the epicardial layer of 304 myocardial segments was assessed by SENC and by Echo. The segmental transmurality of myocardial infarction was determined as relative amount of LGE (0%: no infarction; 1-50%: non-transmural infarction; 51-100%: transmural infarction). Endocardial and epicardial strain defined by SENC and by Echo differed significantly between segments of different infarct transmurality determined by CMR. Endocardial layer circumferential strain analysis by Echo and by SENC allowed distinction of segments with non-transmural infarction from non-infarcted segments with similar accuracy [area under the curve (AUC) 0.699 vs. 0.649, respectively, P = 0.239]. Epicardial layer circumferential strain analysis by Echo and by SENC allowed distinction of transmural from non-transmural myocardial infarction defined by LGE CMR with similar accuracy (AUC 0.721 vs. 0.664, respectively, P = 0.401). Endocardial strain by SENC correlated moderately with endocardial strain by Echo (r = 0.50; standard error of estimate = 5.2%). CONCLUSION: Layer-specific analysis of myocardial deformation by Echo and by SENC allows discrimination between different transmurality categories of myocardial infarction with similar accuracy. However, accuracy of both methods is non-optimal, indicating that further tools for improvement should be evaluated in the future.

Quantitative analysis of endocardial and epicardial left ventricular myocardial deformation-comparison of strain-encoded cardiac magnetic resonance imaging with two-dimensional speckle-tracking echocardiography.

BACKGROUND: Quantitative analysis of segmental myocardial deformation of different myocardial layers has become possible using strain-encoded cardiac magnetic resonance imaging (SENC) and speckle-tracking echocardiography (STE). We evaluated and compared the quantitative analysis of myocardial deformation using SENC and STE. METHODS: In 44 patients (age 61 ± 13 years, 34 men), SENC by cardiac magnetic resonance imaging using a 1.5-Tesla whole-body scanner and two-dimensional STE were performed prospectively. Quantitative layer-specific analysis of segmental left ventricular function was performed to determine the peak circumferential and peak longitudinal systolic strain values using SENC and STE of an endocardial and epicardial myocardial layer. In addition, segmental function was defined as normokinetic, hypokinetic, or akinetic by visual analysis of the magnetic resonance imaging cine sequences. RESULTS: The endocardial and epicardial strain defined by SENC or STE differed significantly between the visually defined segmental function states. The correlation of the peak circumferential endocardial strain by SENC versus STE (intraclass correlation coefficient [ICC] 0.493, 95% CI 0.358-0.597) tended to be better than the correlation of the circumferential epicardial strain using both methods (ICC 0.321, 95% CI 0.238-0.399). The correlation of the peak longitudinal endocardial strain by SENC and STE was similar (ICC 0.472, 95% CI 0.398-0.541), in contrast to the longitudinal epicardial strain analysis by both techniques (ICC 0.554, 95% CI 0.417-0.655). Circumferential strain analysis by STE allowed better distinction of the hypokinetic or akinetic segments from the normokinetic segments than did the circumferential strain analysis by SENC of the endocardial layer (area under the receiver operating characteristic curve [AUC ROC] 0.946 vs 0.884; P < .001) or epicardial layer (AUC ROC 0.884 vs 0.782; P < .001). Longitudinal strain analysis using STE and SENC of the endocardial layer (AUC ROC 0.851 vs 0.839; P = .5838) and epicardial layer (AUC ROC 0.849 vs 0.833; P = .4321) had similar diagnostic value for identifying the presence of hypokinetic and akinetic segments. CONCLUSIONS: Quantitative analysis of segmental deformation by SENC and STE allowed accurate distinction of myocardial segments with different functional states. Circumferential endocardial strain analysis by STE allowed the best distinction of segments with impaired function from the normokinetic segments.

Dependency of cardiac resynchronization therapy on myocardial viability at the LV lead position.

OBJECTIVES: This study sought to analyze the effectiveness of cardiac resynchronization therapy (CRT) related to the viability in the segment of left ventricular (LV) lead position defined by myocardial deformation imaging. BACKGROUND: Echocardiographic myocardial deformation analysis allows determination of LV lead position as well as extent of myocardial viability. METHODS: Myocardial deformation imaging based on tracking of acoustic markers within 2-dimensional echo images (GE Ultrasound, GE Healthcare, Horton, Norway) was performed in 65 heart failure patients (54 ± 6 years of age, 41 men) before and 12 months after CRT implantation. In a 16-segment model, the LV lead position was defined based on the segmental strain curve with earliest peak strain, whereas the CRT system was programmed to pure LV pacing. Nonviability of a segment (transmural scar formation) was assumed if the peak systolic circumferential strain was >-11.1%. RESULTS: In 47 patients, the LV lead was placed in a viable segment, and in 18 patients, it was placed in a nonviable segment. At 12-month follow-up there was greater decrease of LV end-diastolic volumes (58 ± 13 ml vs. 44 ± 12 ml, p = 0.0388) and greater increase of LV ejection fraction (11 ± 4% vs. 5 ± 4%, p = 0.0343) and peak oxygen consumption (2.5 ± 0.9 ml/kg/min vs. 1.7 ± 1.1 ml/kg/min, p = 0.0465) in the viable compared with the nonviable group. The change in LV ejection fraction and the reduction in LV end-diastolic volumes at follow-up correlated to an increasing peak systolic circumferential strain in the segment of the LV pacing lead (r = 0.61, p = 0.0274 and r = 0.64, p = 0.0412, respectively). Considering only patients with ischemic heart disease, differences between viable and nonviable LV lead position group were even greater. CONCLUSIONS: Preserved viability in the segment of the CRT LV lead position results in greater LV reverse remodeling and functional benefit at 12-month follow-up. Deformation imaging allows analysis of viability in the LV lead segment.