CD38 deficient mice are not protected from atherosclerosis

CD38 is a multifunctional enzyme implicated in chemotaxis of myeloid cells and lymphocyte activation, but also expressed by resident cells such as endothelial and smooth muscle cells. CD38 is important for host defense against microbes. However, CD38's role in the pathogenesis of atherosclerosis is controversial with seemingly conflicting results reported so far. To clarify the discrepancy of current literature on the effect of CD38 ablation on atherosclerosis development, we implanted a shear stress modifier around the right carotid artery in CD38-/- and WT mice. Hypercholesterolemia was induced by human gain-of-function PCSK9 (D374Y), introduced using AAV vector (serotype 9), combined with an atherogenic diet for a total of 9 weeks. Atherosclerosis was assessed at the aortic root, aortic arch and the right carotid artery. The findings can be summarized as follows: i) CD38-/- and WT mice had a similar atherosclerotic burden in all three locations, ii) No significant differences in monocyte infiltration or macrophage content could be seen in the plaques, and iii) The amount of collagen deposition in the plaques were also similar between CD38-/- and WT mice. In conclusion, our data suggest that CD38-/- mice are neither protected against nor prone to atherosclerosis compared to WT mice.

SLAMF1-derived peptide exhibits cardio protection after permanent left anterior descending artery ligation in mice

Acute myocardial infarction (MI) results in tissue damage to affected areas of the myocardium. The initial inflammatory response is the most damaging for residual cardiac function, while at later stages inflammation is a prerequisite for proper healing and scar formation. Balancing the extent and duration of inflammation during various stages after MI is thus pivotal for preserving cardiac function. Recently, a signaling lymphocytic activation molecule 1 (SLAMF1)-derived peptide (P7) was shown to reduce the secretion of inflammatory cytokines and protected against acute lipopolysaccharide-induced death in mice. In the present study, we experimentally induced MI by permanent ligation of the left anterior descending artery (LAD) in mice and explored the beneficial effect of immediately administering P7, with the aim of dampening the initial inflammatory phase without compromising the healing and remodeling phase. Blood samples taken 9 h post-LAD surgery and P7 administration dampened the secretion of inflammatory cytokines, but this dampening effect of P7 was diminished after 3 days. Echocardiography revealed less deterioration of cardiac contraction in mice receiving P7. In line with this, less myocardial damage was observed histologically in P7-treated mice. In conclusion, the administration of a SLAMF1-derived peptide (P7) immediately after induction of MI reduces the initial myocardial inflammation, reduces infarct expansion, and leads to less deterioration of cardiac contraction.

Cholangiocytes Modulate CD100 Expression in the Liver and Facilitate Pathogenic T-Helper 17 Cell Differentiation

BACKGROUND & AIMS

Chronic inflammation surrounding bile ducts contributes to the disease pathogenesis of most cholangiopathies. Poor efficacy of immunosuppression in these conditions suggests biliary-specific pathologic principles. Here we performed biliary niche specific functional interpretation of a causal mutation (CD100 K849T) of primary sclerosing cholangitis (PSC) to understand related pathogenic mechanisms.

METHODS

Biopsy specimens of explanted livers and endoscopy-guided sampling were used to assess the CD100 expression by spatial transcriptomics, immune imaging, and high-dimensional flow cytometry. To model pathogenic cholangiocyte-immune cell interaction, splenocytes from mutation-specific mice were cocultured with cholangiocytes. Pathogenic pathways were pinpointed by RNA sequencing analysis of cocultured cells and cross-validated in patient materials.

RESULTS

CD100 is mainly expressed by immune cells in the liver and shows a unique pattern around PSC bile ducts with RNA-level colocalization but poor detection at the protein level. This appears to be due to CD100 cleavage as soluble CD100 is increased. Immunophenotyping suggests biliary-infiltrating T cells as the major source of soluble CD100, which is further supported by reduced surface CD100 on T cells and increased metalloproteinases in cholangiocytes after coculturing. Pathogenic T cells that adhered to cholangiocytes up-regulated genes in the T-helper 17 cell differentiation pathway, and the CD100 mutation boosted this process. Consistently, T-helper 17 cells dominate biliary-resident CD4 T cells in patients.

CONCLUSIONS

CD100 exerts its functional impact through cholangiocyte-immune cell cross talk and underscores an active, proinflammatory role of cholangiocytes that can be relevant to novel treatment approaches.

Modeling and simulation of underwater acoustic propagation through a random distribution of ice blocks

Acoustic propagation through a random distribution of 1 m ice cubes, from 100 to 1000 Hz, was simulated in a 3D finite element model. The effective sound speed and attenuation as functions of frequency were calculated from the simulated signals. Attempts were made to fit a number of models to the wave speed and attenuation, including single scattering, lossy water, and Biot approximations. An extended Biot model, developed for acoustic propagation in granular seabed sediments, was able to fit the simulation up to 300 Hz. Beyond this frequency, the simulation shows that multiple scattering dominates.

Radiographers use of social media - SoMe in a Nordic perspective

INTRODUCTION

Social media (SoMe) is widely used as a communication platform in everyday life. Also, healthcare professionals have embraced SoMe as a communication tool for both peers and patients. It is becoming an interactive tool for discussing professionals' issues and a place where learning and education occur. This study explores the specific patterns of SoMe use for radiographers' in the Nordic countries. The aim of this survey was to investigate radiographers use of social platforms in a professional setting.

METHODS

A 29-item survey was prepared, and pilot-tested. The survey was produced in Danish a language that all Nordic countries master. In general, most Nordic languages are very similar. The survey was distributed by online platforms such as Facebook, LinkedIn, Twitter/X, and also distributed by newsletters by the Norwegian and Danish national radiographers societies. All data was collected anonymously. An Ethical Research approval was obtained from the University of Southern Denmark.

RESULTS

A total of 242 respondents completed the survey (Denmark n = 183, Norway n = 48, Sweden n = 8, and n = 3 from other Scandinavian countries). The respondents included 186 females, 52 males and four were undisclosed. On average, the respondents spent approximately 2 h and 23 min daily on SoMe, with 27 min specifically dedicated to content relevant to radiographers. Facebook was the preferred platform with 93 % (n = 226). A total of 5.4 % (n = 13) respondents had experienced contact from patients and/or next of kin, while 92 % (n = 222) reported no such interactions and 2.9 % (n = 7) were undisclosed. A total of 52.8 % (n = 128) used SoMe in relation to courses, conferences, or online meetings. This shows that time spent on content relevant to radiographers imply that SoMe can be a relevant tool for reaching radiographers.

CONCLUSION

The survey demonstrates radiographers' use of SoMe for personal and professional interest, with Facebook as the preferred social media platform. SoMe were mostly used during courses, conferences, or online meetings with half of the respondent reported using SoMe platforms during working hours. These results underscore the untapped potential of SoMe in professional healthcare settings. Additionally, the study offers insight into current practices, facilitating comparisons to identify trends in SoMe usage within the radiographer community.

IMPLICATIONS FOR PRACTICE

The findings advocate for the strategic use of SoMe by radiographers', emphasizing professional networking and knowledge sharing. However, clear guidelines are necessary to ensure patient confidentiality and data security in these digital interactions.

Bacterial Brain Abscesses Expand Despite Effective Antibiotic Treatment: A Process Powered by Osmosis Due to Neutrophil Cell Death

BACKGROUND AND OBJECTIVES

A bacterial brain abscess is an emergency and should be drained of pus within 24 hours of diagnosis, as recently recommended. In this cross-sectional study, we investigated whether delaying pus drainage entails brain abscess expansion and what the underlying mechanism might be.

METHODS

Repeated brain MRI of 47 patients who did not undergo immediate pus drainage, pus osmolarity measurements, immunocytochemistry, proteomics, and 18F-fluorodeoxyglucose positron emission tomography.

RESULTS

Time from first to last MRI before neurosurgery was 1 to 14 days. Abscesses expanded in all but 2 patients: The median average increase was 23% per day (range 0%-176%). Abscesses expanded during antibiotic therapy and even if the pus did not contain viable bacteria. In a separate patient cohort, we found that brain abscess pus tended to be hyperosmolar (median value 360 mOsm; range 266-497; n = 14; normal cerebrospinal fluid osmolarity is ∼290 mOsm). Hyperosmolarity would draw water into the abscess cavity, causing abscess expansion in a ballooning manner through increased pressure in the abscess cavity. A mechanism likely underlying pus hyperosmolarity was the recruitment of neutrophils to the abscess cavity with ensuing neutrophil cell death and decomposition of neutrophil proteins and other macromolecules to osmolytes: Pus analysis showed the presence of neutrophil proteins (protein-arginine deiminases, citrullinated histone, myeloperoxidase, elastase, cathelicidin). Previous studies have shown very high levels of osmolytes (ammonia, amino acids) in brain abscess pus. 18F-fluorodeoxyglucose positron emission tomography showed focal neocortical hypometabolism 1 to 8 years after brain abscess, indicating long-lasting damage to brain tissue.

CONCLUSION

Brain abscesses expand despite effective antibiotic treatment. Furthermore, brain abscesses cause lasting damage to surrounding brain tissue. These findings support drainage of brain abscesses within 24 hours of diagnosis.

Plant size, latitude, and phylogeny explain within-population variability in herbivory

Interactions between plants and herbivores are central in most ecosystems, but their strength is highly variable. The amount of variability within a system is thought to influence most aspects of plant-herbivore biology, from ecological stability to plant defense evolution. Our understanding of what influences variability, however, is limited by sparse data. We collected standardized surveys of herbivory for 503 plant species at 790 sites across 116° of latitude. With these data, we show that within-population variability in herbivory increases with latitude, decreases with plant size, and is phylogenetically structured. Differences in the magnitude of variability are thus central to how plant-herbivore biology varies across macroscale gradients. We argue that increased focus on interaction variability will advance understanding of patterns of life on Earth.

Patient involvement and expectations during CT scans. Tinkering to involve patients and offer care in radiographic practice

INTRODUCTION

This study investigated how patients expected and experienced to be put first and cared for in diagnostic imaging settings and how putting the patient first was operationalized in practice.

METHODS

A qualitative field study was conducted in two Danish hospitals to investigate patients' expectations and experiences of care and involvement during CT examinations. Data collection methods included semi-structured interviews and participant observations of five examination cases. Three Computed Tomography (CT) guided lung biopsy intervention studies and two conventional CT studies of the chest of patients being investigated for lung cancer in Fast Track Cancer Referral Programs (FTCRP) were included.

RESULTS

Patients reported low expectations of receiving care and being involved during examinations. Perceptions of receiving care predominantly consisted of being received in a kind, personalized manner. Expectations of involvement in the procedure were reported in terms of readiness to do as they were told, complying with requests put to each patient. Concepts of care and involvement were challenged in their formal meanings and found to be entangled in complex interactions within sociotechnical boundaries.

CONCLUSION

Patient's expectations of receiving care and being involved in the diagnostic imaging procedures, were expressed in noncommittal terms, and were overshadowed by patients' focus on getting through the examination, in order to get an answer to their tentative diagnose. The concepts of care and patient involvement were negotiated and reconceptualized within the sociotechnical framework of the diagnostic imaging situation of the individual patient. The concept of "tinkering" is suggested as a means of understanding how patientcare is performed during diagnostic imaging procedures.

IMPLICATIONS FOR PRACTICE

Issues were identified that may help professionals to put "the patient first", thus, improving patient centered care.

MR Elastography Identifies Regions of Extracellular Matrix Reorganization Associated with Shorter Survival in Glioblastoma Patients

Background

Biomechanical tissue properties of glioblastoma tumors are heterogeneous, but the molecular mechanisms involved and the biological implications are poorly understood. Here, we combine magnetic resonance elastography (MRE) measurement of tissue stiffness with RNA sequencing of tissue biopsies to explore the molecular characteristics of the stiffness signal.

Methods

MRE was performed preoperatively in 13 patients with glioblastoma. Navigated biopsies were harvested during surgery and classified as ‘stiff’ or ‘soft’ according to MRE stiffness measurements (|G*|norm). Twenty-two biopsies from eight patients were analysed by RNA sequencing.

Results

The mean whole-tumor stiffness was lower than normal-appearing white matter. The surgeon’s stiffness evaluation did not correlate with the MRE measurements, which suggests that these measures assess different physiological properties. Pathway analysis of the differentially expressed genes between ‘stiff’ and ‘soft’ biopsies showed that genes involved in extracellular matrix reorganization and cellular adhesion were overexpressed in ‘stiff’ biopsies. Supervised dimensionality reduction identified a gene expression signal separating ‘stiff ‘and ‘soft’ biopsies. Using the NIH Genomic Data Portal, 265 glioblastoma patients were divided into those with (n=63) and without (n=202) this gene expression signal. The median survival time of patients with tumors expressing the gene signal associated with ‘stiff’ biopsies was 100 days shorter than that of patients not expressing it (360 versus 460 days, hazard ratio: 1.45, P<0.05).

Conclusion

MRE imaging of glioblastoma can provide non-invasive information on intratumoral heterogeneity. Regions of increased stiffness were associated with extracellular matrix reorganization. An expression signal associated with ‘stiff’ biopsies correlated with shorter survival of glioblastoma patients.

Wave equations for porous media described by the Biot model

Single-mode equivalent space-time representations of the acoustic wave propagating in a Biot poroelastic medium have previously been found only for asymptotic cases: In the low frequency regime, where the viscous skin depth is greater than the characteristic pore size, the time domain equivalent is represented with integer order temporal and spatial loss terms, whereas in the high frequency regime, it is represented with fractional order temporal and spatial loss terms. In the current work, a time domain representation in terms of a partial differential equation is proposed for all three wave solutions of the Biot model across all frequencies, and it is derived from the material response function of the Biot poroelastic medium with suitable approximations for the compressional modes and the dynamic permeability. The dynamic permeability in the time domain is represented by a fractional pseudo-differential operator. Optimal correction factors are introduced into the wave equation to compensate for the discrepancies in the compressional wave dispersion and attenuation. Additionally, the method for incorporating the squirt flow mechanism into the wave equation via the Extended Biot poroviscoelastic model is described. The proposed wave equation has a physical basis and satisfies the passivity criterion.

NEIL3-deficient bone marrow displays decreased hematopoietic capacity and reduced telomere length

Deficiency of NEIL3, a DNA repair enzyme, has significant impact on mouse physiology, including vascular biology and gut health, processes related to aging. Leukocyte telomere length (LTL) is suggested as a marker of biological aging, and shortened LTL is associated with increased risk of cardiovascular disease. NEIL3 has been shown to repair DNA damage in telomere regions in vitro. Herein, we explored the role of NEIL3 in telomere maintenance in vivo by studying bone marrow cells from atherosclerosis-prone NEIL3-deficient mice. We found shortened telomeres and decreased activity of the telomerase enzyme in bone marrow cells derived from Apoe -/- Neil3 -/- as compared to Apoe -/- mice. Furthermore, Apoe -/- Neil3 -/- mice had decreased leukocyte levels as compared to Apoe -/- mice, both in bone marrow and in peripheral blood. Finally, RNA sequencing of bone marrow cells from Apoe -/- Neil3 -/- and Apoe -/- mice revealed different expression levels of genes involved in cell cycle regulation, cellular senescence and telomere protection. This study points to NEIL3 as a telomere-protecting protein in murine bone marrow in vivo.

Immune complexes, innate immunity, and NETosis in ChAdOx1 vaccine-induced thrombocytopenia

Aims

We recently reported five cases of vaccine-induced immune thrombotic thrombocytopenia (VITT) 7–10 days after receiving the first dose of the ChAdOx1 nCoV-19 adenoviral vector vaccine against corona virus disease 2019 (COVID-19). We aimed to investigate the pathogenic immunological responses operating in these patients.

Methods and results

We assessed circulating inflammatory markers by immune assays and immune cell phenotyping by flow cytometry analyses and performed immunoprecipitation with anti-platelet factor (PF)4 antibody in plasma samples followed by mass spectrometry from all five patients. A thrombus was retrieved from the sinus sagittal superior of one patient and analysed by immunohistochemistry and flow cytometry. Precipitated immune complexes revealed multiple innate immune pathway triggers for platelet and leucocyte activation. Plasma contained increased levels of innate immune response cytokines and markers of systemic inflammation, extensive degranulation of neutrophils, and tissue and endothelial damage. Blood analyses showed activation of neutrophils and increased levels of circulating H3Cit, dsDNA, and myeloperoxidase–DNA complex. The thrombus had extensive infiltration of neutrophils, formation of neutrophil extracellular traps (NETs), and IgG deposits.

Conclusions

The results show that anti-PF4/polyanion IgG-mediated thrombus formation in VITT patients is accompanied by a massive innate immune activation and particularly the fulminant activation of neutrophils including NETosis. These results provide novel data on the immune response in this rare adenoviral vector-induced VITT.

NEIL3-deficiency increases gut permeability and contributes to a pro-atherogenic metabolic phenotype

Atherosclerosis and its consequences cause considerable morbidity and mortality world-wide. We have previously shown that expression of the DNA glycosylase NEIL3 is regulated in human atherosclerotic plaques, and that NEIL3-deficiency enhances atherogenesis in Apoe-/- mice. Herein, we identified a time point prior to quantifiable differences in atherosclerosis between Apoe-/-Neil3-/- mice and Apoe-/- mice. Mice at this age were selected to explore the metabolic and pathophysiological processes preceding extensive atherogenesis in NEIL3-deficient mice. Untargeted metabolomic analysis of young Apoe-/-Neil3-/- mice revealed significant metabolic disturbances as compared to mice expressing NEIL3, particularly in metabolites dependent on the gut microbiota. 16S rRNA gene sequencing of fecal bacterial DNA indeed confirmed that the NEIL3-deficient mice had altered gut microbiota, as well as increased circulating levels of the bacterially derived molecule LPS. The mice were challenged with a FITC-conjugated dextran to explore gut permeability, which was significantly increased in the NEIL3-deficient mice. Further, immunohistochemistry showed increased levels of the proliferation marker Ki67 in the colonic epithelium of NEIL3-deficient mice, suggesting increased proliferation of intestinal cells and gut leakage. We suggest that these metabolic alterations serve as drivers of atherosclerosis in NEIL3-deficient mice.

Endonuclease V Regulates Atherosclerosis Through C-C Motif Chemokine Ligand 2-Mediated Monocyte Infiltration

Background

In cardiovascular diseases, atherosclerotic disorder are the most frequent and important with respect to morbidity and mortality. Inflammation mediated by immune cells is central in all parts of the atherosclerotic progress, and further understanding of the underlying mechanisms is needed. Growing evidence suggests that deamination of adenosine‐to‐inosine in RNA is crucial for a correct immune response; nevertheless, the role of adenosine‐to‐inosine RNA editing in atherogenesis has barely been studied. Several proteins have affinity for inosines in RNA, one being ENDOV (endonuclease V), which binds and cleaves RNA at inosines. Data on ENDOV in atherosclerosis are lacking.

Methods and Results

Quantitative polymerase chain reaction on ENDOV mRNA showed an increased level in human carotid atherosclerotic plaques compared with control veins. Inosine‐ribonuclease activity as measured by an enzyme activity assay is detected in immune cells relevant for the atherosclerotic process. Abolishing EndoV in atherogenic apolipoprotein E‐deficient (ApoE^−/−) mice reduces the atherosclerotic plaque burden, both in size and lipid content. In addition, in a brain stroke model, mice without ENDOV suffer less damage than control mice. Finally, lack of EndoV reduces the recruitment of monocytes to atherosclerotic lesions in atherogenic ApoE^−/− mice.

Conclusions

ENDOV is upregulated in human atherosclerotic lesions, and data from mice suggest that ENDOV promotes atherogenesis by enhancing the monocyte recruitment into the atherosclerotic lesion, potentially by increasing the effect of CCL2 activation on these cells.

OXR1A, a Coactivator of PRMT5 Regulating Histone Arginine Methylation

Oxidation resistance gene 1 (OXR1) protects cells against oxidative stress. We find that male mice with brain-specific isoform A knockout (Oxr1A^-/-) develop fatty liver. RNA sequencing of male Oxr1A^-/- liver indicates decreased growth hormone (GH) signaling, which is known to affect liver metabolism. Indeed, Gh expression is reduced in male mice Oxr1A^-/- pituitary gland and in rat Oxr1A^-/- pituitary adenoma cell-line GH3. Oxr1A^-/- male mice show reduced fasting-blood GH levels. Pull-down and proximity ligation assays reveal that OXR1A is associated with arginine methyl transferase PRMT5. OXR1A-depleted GH3 cells show reduced symmetrical dimethylation of histone H3 arginine 2 (H3R2me2s), a product of PRMT5 catalyzed methylation, and chromatin immunoprecipitation (ChIP) of H3R2me2s shows reduced Gh promoter enrichment. Finally, we demonstrate with purified proteins that OXR1A stimulates PRMT5/MEP50-catalyzed H3R2me2s. Our data suggest that OXR1A is a coactivator of PRMT5, regulating histone arginine methylation and thereby GH production within the pituitary gland.

Simple circuit equivalents for the constant phase element

The constant phase element (CPE) is a capacitive element with a frequency-independent negative phase between current and voltage which interpolates between a capacitor and a resistor. It is used extensively to model the complexity of the physics in e.g. the bioimpedance and electrochemistry fields. There is also a similar element with a positive phase angle, and both the capacitive and inductive CPEs are members of the family of fractional circuit elements or fractance. The physical meaning of the CPE is only partially understood and many consider it an idealized circuit element. The goal here is to provide alternative equivalent circuits, which may give rise to better interpretations of the fractance. Both the capacitive and the inductive CPEs can be interpreted in the time-domain, where the impulse and step responses are temporal power laws. Here we show that the current impulse responses of the capacitive CPE is the same as that of a simple time-varying series RL-circuit where the inductor’s value increases linearly with time. Similarly, the voltage response of the inductive CPE corresponds to that of a simple parallel RC circuit where the capacitor’s value increases linearly with time. We use the Micro-Cap circuit simulation program, which can handle time-varying circuits, for independent verification. The simulation corresponds exactly to the expected response from the proposed equivalents within 0.1% error. The realization with time-varying components correlates with known time-varying properties in applications, and may lead to a better understanding of the link between CPE and applications.

DNA glycosylase Neil3 regulates vascular smooth muscle cell biology during atherosclerosis development

BACKGROUND AND AIMS

Atherogenesis involves a complex interaction between immune cells and lipids, processes greatly influenced by the vascular smooth muscle cell (VSMC) phenotype. The DNA glycosylase NEIL3 has previously been shown to have a role in atherogenesis, though whether this is due to its ability to repair DNA damage or to other non-canonical functions is not yet clear. Hereby, we investigate the role of NEIL3 in atherogenesis, specifically in VSMC phenotypic modulation, which is critical in plaque formation and stability.

METHODS

Chow diet-fed atherosclerosis-prone Apoe^-/- mice deficient in Neil3, and NEIL3-abrogated human primary aortic VSMCs were characterized by qPCR, and immunohistochemical and enzymatic-based assays; moreover, single-cell RNA sequencing, mRNA sequencing, and proteomics were used to map the molecular effects of Neil3/NEIL3 deficiency in the aortic VSMC phenotype. Furthermore, BrdU-based proliferation assays and Western blot were performed to elucidate the involvement of the Akt signaling pathway in the transdifferentiation of aortic VSMCs lacking Neil3/NEIL3.

RESULTS

We show that Neil3 deficiency increases atherosclerotic plaque development without affecting systemic lipids. This observation was associated with a shift in VSMC phenotype towards a proliferating, lipid-accumulating and secretory macrophage-like cell phenotype, without changes in DNA damage. VSMC transdifferentiation in Neil3-deficient mice encompassed increased activity of the Akt signaling pathway, supported by cell experiments showing Akt-dependent proliferation in NEIL3-abrogated human primary aortic VSMCs.

CONCLUSIONS

Our findings show that Neil3 deficiency promotes atherosclerosis development through non-canonical mechanisms affecting VSMC phenotype involving activation of the Akt signaling pathway.

Robustness of MR Elastography in the Healthy Brain: Repeatability, Reliability, and Effect of Different Reconstruction Methods

BACKGROUND

Changes in brain stiffness can be an important biomarker for neurological disease. Magnetic resonance elastography (MRE) quantifies tissue stiffness, but the results vary between acquisition and reconstruction methods.

PURPOSE

To measure MRE repeatability and estimate the effect of different reconstruction methods and varying data quality on estimated brain stiffness.

STUDY TYPE

Prospective.

SUBJECTS

Fifteen healthy subjects.

FIELD STRENGTH/SEQUENCE

3T MRI, gradient-echo elastography sequence with a 50 Hz vibration frequency.

ASSESSMENT

Imaging was performed twice in each subject. Images were reconstructed using a curl-based and a finite-element-model (FEM)-based method. Stiffness was measured in the whole brain, in white matter, and in four cortical and four deep gray matter regions. Repeatability coefficients (RC), intraclass correlation coefficients (ICC), and coefficients of variation (CV) were calculated. MRE data quality was quantified by the ratio between shear waves and compressional waves.

STATISTICAL TESTS

Median values with range are presented. Reconstruction methods were compared using paired Wilcoxon signed-rank tests, and Spearman's rank correlation was calculated between MRE data quality and stiffness. Holm-Bonferroni corrections were employed to adjust for multiple comparisons.

RESULTS

In the whole brain, CV was 4.3% and 3.8% for the curl and the FEM reconstruction, respectively, with 4.0-12.8% for subregions. Whole-brain ICC was 0.60-0.74, ranging from 0.20 to 0.89 in different regions. RC for the whole brain was 0.14 kPa and 0.17 kPa for the curl and FEM methods, respectively. FEM reconstruction resulted in 39% higher stiffness than the curl reconstruction (P < 0.05). MRE data quality, defined as shear-compression wave ratio, was higher in peripheral regions than in central regions of the brain (P < 0.05). No significant correlations were observed between MRE data quality and stiffness estimates.

DATA CONCLUSION

MRE of the human brain is a robust technique in terms of repeatability. Caution is warranted when comparing stiffness values obtained with different techniques.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY STAGE: 1.

Transcatheter interventions of coarctation of the aorta (CoA): a multinational population-based registry – procedural complications

Background

Patients with a native or re CoA with an invasively meassured peak to peak gardient &gt;20 mmHg have a guideline indication for intervention. The decision regarding transcatheter versus surgical intervention depends on a variety of factors including location and complexity of CoA, patient/parent preference and availability of a team capable to perform the intevention with a low rate of complications. The aim of the present analysis was to describe factors associated with risk for procedural complications during transcatheter interventions in CoA. Separate anlysis was done for complications at intervention site and at access site.

Methods

All consecutive patients undergoing catheter interventions for CoA from 1st of January 2000 to 31st of December 2016 were identified by each of the particpating nine centers. The nine centers perform all catheter interventions for CoA for a complete population coverage of 25 millions inhabitants. A common protocol was filled out from medical records. Exclusion criteria were weight less than 20 kg at the time of intervention or Norwood surgery for hypoplastic left heart surgery. Complications at the intervention site included aneurysm formation, dissection of the aorta, extravasation of the aorta or neurological impairment. Complications at the access site was defined as any complication that prolonged the hospital stay.

Results

590 interventions were performed on 520 patients: two interventions n=76, three: n=11, four n=2 and one patient underwent five interventions. There was no mortality in relation to the procedure or during the hospitalisation. The age span of the patients was wide; 4–79 years old (median= 23). 51% had a native CoA, 42% post surgery re-CoA, 22% had had a previous catheter intervention. In 160 (27%) of the interventions balloon dilatation only was performed. Overall, procedural succes was 87%, n=513, 44 procedures (8%) were partially successful and 9 procedures (2%) were not successful. 512 (87%) had one day in hospital stay and 17 patients (6%) had a hospital stay longer than 3 days. In 11 procedures (1.9%) at least one complication occurred at the intervention site; (6 aneurysm formation, 3 neurological impairment, 3 dissection of aorta, 2 extra vasation of aorta), nine of them without prolonged hospital stay. In 25 procedures (4.2%) at least one complications at the access site was observed. Access site complications were associated with older age (mean 38 years (10–79))

Conclusions

In a large, multicenter registry with complete follow-up, complications at the intervention site occurred in 1.9% and at the access site in 4.2% of interventions. Transcatheter intervention of CoA can be performed with low risk of complications.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): ALF-LUA, Gothenburg Heart and Lung Foundation

N6-methyladenosine in RNA of atherosclerotic plaques: An epitranscriptomic signature of human carotid atherosclerosis

BACKGROUND

More than 170 post-transcriptional RNA modifications regulate the localization, processing and function of cellular RNAs, and aberrant RNA modifications have been linked to a range of human diseases. The RNA modification landscape in atherosclerosis, the main underlying cause of cardiovascular diseases, is still largely unknown.

METHODS

We used mass spectrometry to analyse a selection of RNA-modifying enzymes and the N6-methyladenosine (m⁶A) in carotid atherosclerotic lesion samples representing early and advanced stages of atherosclerosis as compared to non-atherosclerotic arteries from healthy controls.

FINDINGS

(i) the detection of different levels of several enzymes involved in methylations occurring in rRNA and mRNA; (ii) these findings included changes in the levels of methyltransferases ('writers'), binding proteins ('readers') and demethylases ('erasers') during atherosclerosis as compared to non-atherosclerotic control arteries, with generally the most prominent differences in samples from early atherosclerotic lesions; and (iii) these changes were accompanied by a marked downregulation of m⁶A in rRNA, the most abundant and well-studied modification in mRNA with a wide range of effects on cell biology.

INTERPRETATION

We show for the first time that RNA-modifying enzymes and the well-studied RNA modification m⁶A are differentially regulated in atherosclerotic lesions, which potentially could help creating new prognostic and treatment strategies.

YKL-40 (Chitinase-3-Like Protein 1) Serum Levels in Aortic Stenosis

BACKGROUND

Identification of novel biomarkers could provide prognostic information and improve risk stratification in patients with aortic stenosis (AS). YKL-40 (chitinase-3-like protein 1), a protein involved in atherogenesis, is upregulated in human calcific aortic valves. We hypothesized that circulating YKL-40 would be elevated and associated with the degree of AS severity and outcome in patients with symptomatic AS.

METHODS

Plasma YKL-40 was analyzed in 2 AS populations, one severe AS (n=572) with outcome measures and one with mixed severity (n=67). YKL-40 expression in calcified valves and in an experimental pressure overload model was assessed.

RESULTS

We found (1) patients with AS had upregulated circulating YKL-40 compared with healthy controls (median 109 versus 34 ng/mL, P<0.001), but levels were not related to the degree of AS severity. (2) High YKL-40 levels (quartile 4) were associated with long-term (median follow-up 4.7 years) all-cause mortality (adjusted hazard ratio, 1.93 [95% CI, 1.37-2.73], P<0.001). (3) YKL-40 protein expression in human calcific valves co-localized with its putative receptor IL-13rα2 in close proximity to valve interstitial cells. (4) Myocardial YKL-40 increased in experimental pressure overload (6-fold in decompensated versus sham mice).

CONCLUSIONS

YKL-40 levels were elevated in AS and associated with mortality but not with other metrics of disease severity including the degree of AS severity. Despite scientific rationale for its role in AS, the clinical utility of circulating YKL-40 as a biomarker is limited. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT01794832.

Cholesterol crystals use complement to increase NLRP3 signaling pathways in coronary and carotid atherosclerosis

BACKGROUND

During atherogenesis, cholesterol precipitates into cholesterol crystals (CC) in the vessel wall, which trigger plaque inflammation by activating the NACHT, LRR and PYD domains-containing protein 3 (NLRP3) inflammasome. We investigated the relationship between CC, complement and NLRP3 in patients with cardiovascular disease.

METHODS

We analysed plasma, peripheral blood mononuclear cells (PBMC) and carotid plaques from patients with advanced atherosclerosis applying ELISAs, multiplex cytokine assay, qPCR, immunohistochemistry, and gene profiling.

FINDINGS

Transcripts of interleukin (IL)-1beta(β) and NLRP3 were increased and correlated in PBMC from patients with acute coronary syndrome (ACS). Priming of these cells with complement factor 5a (C5a) and tumour necrosis factor (TNF) before incubation with CC resulted in increased IL-1β protein when compared to healthy controls. As opposed to healthy controls, systemic complement was significantly increased in patients with stable angina pectoris or ACS. In carotid plaques, complement C1q and C5b-9 complex accumulated around CC-clefts, and complement receptors C5aR1, C5aR2 and C3aR1 were higher in carotid plaques compared to control arteries. Priming human carotid plaques with C5a followed by CC incubation resulted in pronounced release of IL-1β, IL-18 and IL-1α. Additionally, mRNA profiling demonstrated that C5a and TNF priming followed by CC incubation upregulated plaque expression of NLRP3 inflammasome components.

INTERPRETATION

We demonstrate that CC are important local- and systemic complement activators, and we reveal that the interaction between CC and complement could exert its effect by activating the NLRP3 inflammasome, thus promoting the progression of atherosclerosis.

Strengthening core competences of medical and public health students for public health emergencies

Background

The importance of public health capacity development with a focus on public health emergencies and humanitarian assistance is continuously increasing at the global scale. In the time of Public Health Emergencies of International Concern is crucial to provide basic training in core public health competences to all health professionals, including students. Faculty of Medicine & Dentistry, Palacký University Olomouc, Czech Republic (full ASPHER member), implemented in medical as well as public health curricula new topics focused on core competences of health professionals in the area of public health emergencies and humanitarian assistance.

Objectives

To strengthen competences and skills of medical as well as public health students to prepare them better for public health emergencies and humanitarian assistance in the time of increasing risk of global public health emergencies. New modules were proposed and tested in all education programmes at our Faculty of Medicine & Dentistry, Palacký University Olomouc (CZ): General Medicine (Czech and English programmes), Dentistry (Czech and English programmes) and Public Health (Czech programme).

Results

New modules on Public Health Emergencies, including preparedness, responses, risk management and risk communication were successfully tested in all education programmes during the academic year 2018/19 and fully implemented for the academic year 2019/20. New module has blended learning structure based on combination of face-to-face seminars and exercises with e-learning parts, including self-assessment. New module is presented in details.

Conclusions

This new education module fully supports international recommendations to strengthen public health competences and skills of medical as well as public health students to be ready for any unexpected public health emergencies at all levels, in particular at the local community level. COVID-19 pandemic confirmed.

Supported by university project CZ.02.69/0.0/16_015/0002337

Key messages

Medical and public health students with competences and skills on public health emergencies and humanitarian assistance will be an asset for any public health emergency of international concern.

New education module on public health emergencies will support both medical and public health students to be prepared for risk communication, advocacy and action if needed and called to action.

Review of pandemic plans, varying international approaches focusing on medical students’ contribution

A review of pandemic plans and international approaches to pandemics focusing on the responsibilities of medical students should they be called to help in times of need. Are there specific guidelines or competencies in place with respect to medical students? Are medical students being utilised to their maximal capability when compared across different nations on an international basis? These questions were kept in mind during the evaluation and analysis of publicly available pandemic plans and other international systems concerning the approach to pandemics. The main differences, strengths and weaknesses of these responses will be highlighted. The presentation will conclude with proposals of the specific role medical students could play in the pandemic response and the importance of their contribution on an international level.

Future visions for medical education, the importance of public health themes in education and beyond

Steps for the future improvement of competencies evaluation and fulfilment were studied, with the eventual goal of the unification of guidelines internationally to ensure the standardisation and uniformity of the quality of medical education. The future vision for the integration of public health into medical education curriculums, highlighting the importance of public health in medical education and its application in a wide variety of situations across medical education and beyond in practise as a medical professional in a range of specialities. The need for ways to increase engagement of medical students within public health issues will also be discussed.

Personal experiences of medical school education: methods to evaluate competency and ways to improve

Personal experiences of medical school education and the manner in which it is delivered will be discussed. Examples of approaches used for student evaluation of different competencies and the methods to track their progress and development were identified. They were appraised, with their strengths and weaknesses discussed. Ideas to improve the approaches for competencies assessment in medical students were also explored.

Comparing European guidelines for medical student education focusing on emergency preparedness

A review of a variety of European guidelines for the assessment of medical students and their education, progression and preparedness for practise post-medical school. The various approaches were compared and contrasted with the advantages and disadvantages of each being evaluated. Their approaches towards emergency situation preparedness, or lack thereof, were also assessed.

Deletion of Endonuclease V suppresses chemically induced hepatocellular carcinoma

Endonuclease V (EndoV) is a conserved inosine-specific ribonuclease with unknown biological function. Here, we present the first mouse model lacking EndoV, which is viable without visible abnormalities. We show that endogenous murine EndoV cleaves inosine-containing RNA in vitro, nevertheless a series of experiments fails to link an in vivo function to processing of such transcripts. As inosine levels and adenosine-to-inosine editing often are dysregulated in hepatocellular carcinoma (HCC), we chemically induced HCC in mice. All mice developed liver cancer, however, EndoV^−/− tumors were significantly fewer and smaller than wild type tumors. Opposed to human HCC, adenosine deaminase mRNA expression and site-specific editing were unaltered in our model. Loss of EndoV did not affect editing levels in liver tumors, however mRNA expression of a selection of cancer related genes were reduced. Inosines are also found in certain tRNAs and tRNAs are cleaved during stress to produce signaling entities. tRNA fragmentation was dysregulated in EndoV^−/− livers and apparently, inosine-independent. We speculate that the inosine-ribonuclease activity of EndoV is disabled in vivo, but RNA binding allowed to promote stabilization of transcripts or recruitment of proteins to fine-tune gene expression. The EndoV^−/− tumor suppressive phenotype calls for related studies in human HCC.

Time Domain Characterization of the Cole-Cole Dielectric Model

The Cole-Cole model for a dielectric is a generalization of the Debye relaxation model. The most familiar form is in the frequency domain and this manifests itself in a frequency dependent impedance. Dielectrics may also be characterized in the time domain by means of the current and charge responses to a voltage step, called response and relaxation functions respectively. For the Debye model they are both exponentials while in the Cole-Cole model they are expressed by a generalization of the exponential, the Mittag-Leffler function. Its asymptotes are just as interesting and correspond to the Curie-von Schweidler current response which is known from real-life capacitors and the Kohlrausch stretched exponential charge response.

Legumain is upregulated in acute cardiovascular events and associated with improved outcome - potentially related to anti-inflammatory effects on macrophages

BACKGROUND AND AIMS

We have previously found increased levels of the cysteine protease legumain in plasma and plaques from patients with carotid atherosclerosis. This study further investigated legumain during acute cardiovascular events.

METHODS

Circulating levels of legumain from patients and legumain released from platelets were assessed by enzyme-linked-immunosorbent assay. Quantitative PCR and immunoblotting were used to study expression, while localization was visualized by immunohistochemistry.

RESULTS

In the SUMMIT Malmö cohort (n = 339 with or without type 2 diabetes and/or cardiovascular disease [CVD], and 64 healthy controls), the levels of circulating legumain were associated with the presence of CVD in non-diabetics, with no relation to outcome. In symptomatic carotid plaques and in samples from both coronary and intracerebral thrombi obtained during acute cardiovascular events, legumain was co-localized with macrophages in the same regions as platelets. In vitro, legumain was shown to be present in and released from platelets upon activation. In addition, THP-1 macrophages exposed to releasate from activated platelets showed increased legumain expression. Interestingly, primary peripheral blood mononuclear cells stimulated with recombinant legumain promoted anti-inflammatory responses. Finally, in a STEMI population (POSTEMI; n = 272), patients had significantly higher circulating legumain before and immediately after percutaneous coronary intervention compared with healthy controls (n = 67), and high levels were associated with improved outcome.

CONCLUSIONS

Our data demonstrate for the first time that legumain is upregulated during acute cardiovascular events and is associated with improved outcome.

ASPHER V4 Working Group supports the road map for professionalising the public health workforce

Background

The ASPHER V4 Working Group (WG) was established in 2016 and officially launched during the 9th European Public Health Conference in Vienna. One of the key objectives of the WG is to strengthen public health capacity development in V4 countries. The WG supports the implementation of the recently reviewed European Action Plan for Strengthening Public Health Capacities (EAP). The EAP’s review highlighted the need to focus further action on four enabling Essential Public Health Functions (EPHOs) including human resources for public health. This is why the WG is heavily involved in the recent development of a new Road map for professionalising the public health workforce, one of the products of the recently established Coalition of Partners (CoP) that was convened by the WHO Regional Office for Europe in close cooperation with ASPHER and Maastricht University.

Objectives

Supporting the WHO CoP with a focus on development and further implementation of a new Road map for professionalising public health workforce in V4 countries. Using a new rapid assessment tool to evaluate the state of the public health profession in the Czech Republic. Sharing the report on the current state of public health professions in the Czech Republic with the WG and using it as a comparison of the current state in all V4 countries.

Results

Key strengths and weaknesses of the first rapid assessment of the current state of the public health profession in the Czech Republic are presented. Key actions are proposed for the WG: a) Preparation of a grant proposal to the International V4 Fund and b) Continuing active involvement in CoP activities.

Conclusions

The rapid assessment tool for evaluating the state of the public health profession was successfully implemented in the Czech Republic with the close cooperation of academia, researchers, policy makers and practitioners. The summary confirms that further work on the professionalization of the public health workforce is needed.

Key messages

ASPHER V4 WG is strongly involved in the development of a new road map for professionalising the public health workforce, coordinated by the WHO CoP, ASPHER and Maastricht University. Summary of the first rapid assessment of the current state of the public health profession in the Czech Republic confirms the importance of further action in this area of work.

Towards a consensus on rheological models for elastography in soft tissues

A rising wave of technologies and instruments are enabling more labs and clinics to make a variety of measurements related to tissue viscoelastic properties. These instruments include elastography imaging scanners, rheological shear viscometers, and a variety of calibrated stress-strain analyzers. From these many sources of disparate data, a common step in analyzing results is to fit the measurements of tissue response to some viscoelastic model. In the best scenario, this places the measurements within a theoretical framework and enables meaningful comparisons of the parameters against other types of tissues. However, there is a large set of established rheological models, even within the class of linear, causal, viscoelastic solid models, so which of these should be chosen? Is it simply a matter of best fit to a minimum mean squared error of the model to several data points? We argue that the long history of biomechanics, including the concept of the extended relaxation spectrum, along with data collected from viscoelastic soft tissues over an extended range of times and frequencies, and the theoretical framework of multiple relaxation models which model the multi-scale nature of physical tissues, all lead to the conclusion that fractional derivative models represent the most succinct and meaningful models of soft tissue viscoelastic behavior. These arguments are presented with the goal of clarifying some distinctions between, and consequences of, some of the most commonly used models, and with the longer term goal of reaching a consensus among different sub-fields in acoustics, biomechanics, and elastography that have common interests in comparing tissue measurements.

A multiple relaxation interpretation of the extended Biot model

The biphasic extended Biot poroviscoelastic model takes into account the squirt flow in grain-grain contacts and introduces the bulk and shear relaxation modes associated with it. This model has been criticized for its empirical approach, but here the constitutive equations and the time domain wave equations of the model are derived. This also makes it possible to find single phase viscoelastic equivalents for all three wave solutions of the extended Biot model. Particularly, the viscoelastic equivalents for shear wave propagation can be obtained with considerably fewer parameters than the original model. These equivalents are linear viscoelastic models with springs and dampers for the low frequencies and contain half-order spring-pots for high frequencies. For high frequencies, the non-physicality of the shear relaxation mode is highlighted. The relaxation modes of the extended Biot model are interpreted in the framework of multiple relaxation mechanisms showing that the P- and S-wave modes of the model are not much more complex than that for seawater. The model's near linear frequency dependent attenuation in the intermediate frequency range is the result of weighting each relaxation mechanism appropriately.

Levels of Lipoprotein (a) in patients with coronary artery disease with and without inflammatory rheumatic disease: a cross-sectional study

OBJECTIVES

Patients with various inflammatory rheumatic diseases (IRDs) have increased risk of atherothrombotic disease. Lipoprotein (a) (Lp(a)) is a risk factor for atherosclerosis but its role in IRD with accompanying coronary artery disease (CAD) is still unclear. We aimed to examine if serum Lp(a) levels differed between CAD patients with and without accompanying IRD.

DESIGN

A cross-sectional observational, patient-based cohort study.

SETTING

Referred centre for coronary artery bypass grafting in the South Eastern part of Norway.

PARTICIPANTS

67 CAD patients with IRD (CAD/IRD) and 52 CAD patients without IRD (CAD/non-IRD). All patients were Caucasians, aged >18 years, without any clinically significant infection or malignancy.

METHODS

Lp(a) levels in serum were analysed by particle enhanced immunoturbidimetric assay, and Lp(a) levels were related to clinical and biochemical characteristics of the patient population.

RESULTS

We found no differences in serum levels of Lp(a) between CAD patients with and without IRD. In general, we found that Lp(a) correlated poorly with clinical and biochemical parameters including C reactive protein with the same pattern in the CAD/non-IRD and CAD/IRD groups.

CONCLUSIONS

Our data do not support a link between inflammation and Lp(a) levels in CAD and in general Lp(a) levels were not correlated with other risk factors for cardiovascular disease.

Exploiting Ballou's rule for better tissue classification

Ultrasound tissue characterization based on the coefficient of nonlinearity, β_n = 1 + B/2A, has been demonstrated to produce added diagnostic value due to its large variation and sensitivity to tissue structure. However, the parameter has been observed to be significantly correlated to the speed of sound and density. These relationships are analyzed empirically as well as theoretically by developing a pressure-density relation based on a thermodynamic model and the Mie intermolecular potential. The results indicate that for many soft tissues, the coefficient of nonlinearity is largely determined by the isentropic compressibility, κ_s. Consequently, for tissue characterization, estimating the nonlinear response of the medium, given by β_p = β_nκ_s, appears to be beneficial due to correlated quantities.

Imaging localized neuronal activity at fast time scales through biomechanics

Mapping neuronal activity noninvasively is a key requirement for in vivo human neuroscience. Traditional functional magnetic resonance (MR) imaging, with a temporal response of seconds, cannot measure high-level cognitive processes evolving in tens of milliseconds. To advance neuroscience, imaging of fast neuronal processes is required. Here, we show in vivo imaging of fast neuronal processes at 100-ms time scales by quantifying brain biomechanics noninvasively with MR elastography. We show brain stiffness changes of ~10% in response to repetitive electric stimulation of a mouse hind paw over two orders of frequency from 0.1 to 10 Hz. We demonstrate in mice that regional patterns of stiffness modulation are synchronous with stimulus switching and evolve with frequency. For very fast stimuli (100 ms), mechanical changes are mainly located in the thalamus, the relay location for afferent cortical input. Our results demonstrate a new methodology for noninvasively tracking brain functional activity at high speed.

Utility of the Tympanic Membrane Pressure Waveform for Non-invasive Estimation of The Intracranial Pressure Waveform

Time domain analysis of the intracranial pressure (ICP) waveform provides important information about the intracranial pressure-volume reserve capacity. The aim here was to explore whether the tympanic membrane pressure (TMP) waveform can be used to non-invasively estimate the ICP waveform. Simultaneous invasive ICP and non-invasive TMP signals were measured in a total of 28 individuals who underwent invasive ICP measurements as a part of their clinical work up (surveillance after subarachnoid hemorrhage in 9 individuals and diagnostic for CSF circulation disorders in 19 individuals). For each individual, a transfer function estimate between the invasive ICP and non-invasive TMP signals was established in order to explore the potential of the method. To validate the results, ICP waveform parameters including the mean wave amplitude (MWA) were computed in the time domain for both the ICP estimates and the invasively measured ICP. The patient-specific non-invasive ICP signals predicted MWA rather satisfactorily in 4/28 individuals (14%). In these four patients the differences between original and estimated MWA were <1.0 mmHg in more than 50% of observations, and <0.5 mmHg in more than 20% of observations. The study further disclosed that the cochlear aqueduct worked as a physical lowpass filter.

Rheological determinants for simultaneous staging of hepatic fibrosis and inflammation in patients with chronic liver disease

The purpose of this study is to investigate the use of fundamental rheological parameters as quantified by MR elastography (MRE) to measure liver fibrosis and inflammation simultaneously in humans. MRE was performed on 45 patients at 3 T using a vibration frequency of 56 Hz. Fibrosis and inflammation scores were obtained from liver biopsies. Biomechanical properties were quantified in terms of complex shear modulus G* as well as shear wave phase velocity c and shear wave attenuation α. A rheological fractional derivative order model was used to investigate the linear dependence of the free model parameters (dispersion slope y, intrinsic speed c0 , and intrinsic relaxation time τ) on histopathology. Leave-one-out cross-validation was then utilized to demonstrate the effectiveness of the model. The intrinsic speed c0 increases with hepatic fibrosis, while an increased relaxation time τ is reflective of more inflammation of the liver parenchyma. The dispersion slope y does not depend either on fibrosis or on inflammation. The proposed rheological model, given this specific parameterization, establishes the functional dependences of biomechanical parameters on histological fibrosis and inflammation. The leave-one-out cross-validation demonstrates that the model allows identification, from the MRE measurements, of the histology scores when grouped into low-/high-grade fibrosis and low-/high-grade inflammation with significance levels of P = 0.0004 (fibrosis) and P = 0.035 (inflammation). The functional dependences of intrinsic speed and relaxation time on fibrosis and inflammation, respectively, shed new light onto the impact hepatic pathological changes on liver tissue biomechanics in humans. The dispersion slope y appears to represent a structural parameter of liver parenchyma not impacted by the severity of fibrosis/inflammation present in this patient cohort. This specific parametrization of the well-established rheological fractional order model is valuable for the clinical assessment of both fibrosis and inflammation scores, going beyond the capability of the plain shear modulus measurement commonly used for MRE.

Spring-damper equivalents of the fractional, poroelastic, and poroviscoelastic models for elastography

In MR elastography, it is common to use an elastic model for the tissue's response in order to interpret the results properly. More complex models, such as viscoelastic, fractional viscoelastic, poroelastic, or poroviscoelastic ones, are also used. These models appear at first sight to be very different, but here it is shown that they may all be expressed in terms of elementary viscoelastic models. For a medium expressed with fractional models, many elementary spring-damper combinations are added, each of them weighted according to a long-tailed distribution of time constants or relaxation frequencies. This may open up a more physical interpretation of fractional models. The shear-wave component of the poroelastic model is shown to be modeled exactly by a three-component Zener model. The extended poroviscoelastic model is found to be equivalent to what is called a non-standard four-parameter model. Accordingly, the large number of parameters in the porous models can be reduced to the same number as in their viscoelastic equivalents. While the individual displacements from the solid and fluid parts cannot be measured individually, the main use of the poro(visco)elastic models is therefore as a physics-based method for determining parameters in a viscoelastic model.

Publisher's Note: Linking the fractional derivative and the Lomnitz creep law to non-Newtonian time-varying viscosity [Phys. Rev. E 94, 032606 (2016)]

This corrects the article DOI: 10.1103/PhysRevE.94.032606.

Increased Levels of Lectin-Like Oxidized Low-Density Lipoprotein Receptor-1 in Ischemic Stroke and Transient Ischemic Attack

Background

Soluble lectin‐like oxidized low‐density lipoprotein receptor‐1 (sLOX‐1) has been shown to be increased in patients with acute ischemic stroke. Here, we evaluated plasma sLOX‐1 levels and vascular carotid plaque LOX‐1 (ie, OLR1) gene expression in patients with ischemic stroke and transient ischemic attack (TIA) with particular focus on their relation to time since symptom onset.

Methods and Results

Plasma sLOX‐1 (n=232) and carotid plaque OLR1 gene expression (n=146) were evaluated in patients who were referred to evaluation for carotid endarterectomy, as well as in healthy control plasma (n=81). Patients were categorized according to presence of acute ischemic stroke or transient ischemic attack (n=35) ≤7 days, >7 days ≤3 months (n=90), >3 months (n=40), or no reported symptoms before study inclusion (n=67). Our major findings were the following: (1) Patients with carotid atherosclerosis had increased plasma sLOX‐1 levels as compared with controls. (2) Plaque OLR1 mRNA levels were increased in carotid plaques (n=146) compared with nonatherosclerotic vessels (ie, common iliac arteries of organ donors, n=10). (3) There were no differences in sLOX plasma levels or OLR1 gene expression when analyzed according to the time since relevant cerebral ischemic symptoms. (4) Also patients with severe carotid atherosclerosis without any previous ischemic events had raised sLOX‐1 levels. (5) Immunostaining showed colocalization between LOX‐1 and macrophages within the carotid plaques. (6) Also patients with acute stroke (within 7 days) caused by atrial fibrillation (n=22) had comparable raised sLOX‐1 levels.

Conclusions

sLOX‐1 levels are elevated in patients with ischemic stroke and transient ischemic attack independent of cause and time since the ischemic event.

Intradiscal pressure in the degenerated porcine intervertebral disc

Measuring intradiscal pressure is one way of mechanically assessing the discs degenerative state. In this study, the load-bearing capacity of degenerated and their adjacent lumbar intervertebral discs was evaluated using two different injury models. Seventeen adolescent pigs were divided into two groups, an annulus injury group and an endplate injury group. The annulus injury group was subjected to a stab incision in the L3-L4 disc, whereas the endplate injury group received a cranial endplate perforation of the L4 vertebral body. Both groups were biomechanically evaluated three months later using a miniaturized servohydraulic testing machine across L2-L4 and with two pressure needles inserted into the nucleus pulposus of the L2-L3 and L3-L4 discs. Linear relationships between the intradiscal pressure and the applied load were determined within the load range studied. When comparing the ratio of the injured to the adjacent disc pressure, the endplate injury was lower (mean value 0.31) than the annulus injury (mean value 0.51). The pressures in the discs adjacent to the degenerated level were found to be slightly higher. This increase can be expected due to a redistribution in mobility demands in segments adjacent to those with increased stiffness, i.e. degenerated intervertebral discs.

Reactive changes in the adolescent porcine spine with disc degeneration due to endplate injury

Degenerative and reactive structural alterations occurring after experimentally-induced disc degeneration were evaluated using a porcine model. A cranial perforation was made through the L4 vertebral endplate into the nucleus pulposus. Three months later, the lumbar intervertebral disc and adjacent vertebrae were dissected, fixed in formalin and further processed for histopathological analyses. The results showed that there were nucleus pulposus fragments, rather than a distinct border between the nucleus and annulus fibrosus. The central lamellae were distorted and delamination of the outer anterior layers was observed. Blood vessels emerged from the adjacent tissue, penetrated the annulus and branched into the residues of the nucleus. Nerve fibres accompanying the blood vessels could be recognized in the disc within the connective scar tissue. The epiphyseal cartilage plates in the vertebrae were hypertrophic in several areas and there was bone formation directed towards the centre of the vertebral body and the disc. Hypertrophic hyaline cartilage, newly formed bone and scar tissue filled the injury canal. A slight chronic inflammatory reaction was evident along vascular buds. The reactive changes dominated over the degenerated features in the operated disc. Physiological loading enhanced the infiltration of various tissue types characterizing immature cartilage formation. Prominent neovascularisation of the central parts of the disc is likely to be of key importance in turning the degenerative features of the remaining tissue into reactive healthy structures.

Interleukin 27 is increased in carotid atherosclerosis and promotes NLRP3 inflammasome activation

Aim

Interleukin-27 (IL-27) is involved in different inflammatory diseases; however, its role in atherosclerosis is unclear. In this study we investigated the expression of IL-27 and its receptor in patients with carotid atherosclerosis and if IL-27 could modulate the inflammatory effects of the NLRP3 inflammasome in vitro.

Methods

Plasma IL-27 was measured by enzyme immunoassay in patients with carotid stenosis (n = 140) and in healthy controls (n = 19). Expression of IL-27 and IL-27R was analyzed by quantitative PCR and immunohistochemistry in plaques from patients and in non-atherosclerotic vessels. THP-1 monocytes, primary monocytes and peripheral blood mononuclear cells (PBMCs) were used to study effects of IL-27 in vitro.

Results

Our main findings were: (i) Plasma levels of IL-27 were significantly elevated in patients with carotid atherosclerotic disease compared to healthy controls. (ii) Gene expression of IL-27 and IL-27R was significantly elevated in plaques compared to control vessels, and co-localized to macrophages. (iii) In vitro, IL-27 increased NLRP3 inflammasome activation in monocytes with enhanced release of IL-1 β.

Conclusions

We demonstrate increased levels of IL-27 and IL-27R in patients with carotid atherosclerosis. Our in vitro findings suggest an inflammatory role for IL-27, which can possibly be linked to atherosclerotic disease development.

Restrictions on wave equations for passive media

Most derivations of acoustic wave equations involve ensuring that causality is satisfied. Here, the consequences of also requiring that the medium should be passive are explored. This is a stricter criterion than causality for a linear system and implies that there are restrictions on the relaxation modulus and its first few derivatives. The viscous and relaxation models of acoustics satisfy passivity and have restrictions on not only a few, but all derivatives of the relaxation modulus. These models are described as a system of springs and dampers with positive parameters and belong to the important class of completely monotone systems. It is shown here that the attenuation as a function of frequency for such media has to increase slower than a linear function. Likewise, the phase velocity has to increase monotonically. This gives criteria on which one may judge whether a proposed wave equation is passive or not, as illustrated by comparing two different versions of the viscous wave equation.