An adapted dorsal skinfold model used for 4D intravital followed by whole-mount imaging to reveal endothelial cell–pericyte association

Endothelial cells and pericytes are highly dynamic vascular cells and several subtypes, based on their spatiotemporal dynamics or molecular expression, are believed to exist. The interaction between endothelial cells and pericytes is of importance in many aspects ranging from basic development to diseases like cancer. Identification of spatiotemporal dynamics is particularly interesting and methods to studies these are in demand. Here we describe the technical details of a method combining the benefits of high resolution intravital imaging and whole-mount histology. With intravital imaging using an adapted light weight dorsal skinfold chamber we identified blood flow patterns and spatiotemporal subtypes of endothelial cells and pericytes in a 4D (XYZ, spatial+T, time dimension) manner as representative examples for this model. Thereafter the tissue was extracted and stained as a whole-mount, by which the position and volumetric space of endothelial cells as well as pericytes were maintained, to identify molecular subtypes. Integration of the two imaging methods enabled 4D dissection of endothelial cell–pericyte association at the molecular level.

Occult blood flow patterns distal to an occluded artery in acute ischemic stroke

Residual blood flow distal to an arterial occlusion in patients with acute ischemic stroke (AIS) is associated with favorable patient outcome. Both collateral flow and thrombus permeability may contribute to such residual flow. We propose a method for discriminating between these two mechanisms, based on determining the direction of flow in multiple branches distal to the occluding thrombus using dynamic Computed Tomography Angiography (dynamic CTA). We analyzed dynamic CTA data of 30 AIS patients and present patient-specific cases that identify typical blood flow patterns and velocities. We distinguished patterns with anterograde (N = 10), retrograde (N = 9), and both flow directions (N = 11), with a large variability in velocities for each flow pattern. The observed flow patterns reflect the interplay between permeability and collaterals. The presented method characterizes distal flow and provides a tool to study patient-specific distal tissue perfusion.

The Immune and Inflammatory Basis of Acquired Pediatric Cardiac Disease

Children with acquired heart disease face significant health challenges, including a lifetime of strict medical management, multiple cardiac surgeries, and a high mortality risk. Though the presentation of these conditions is diverse, a unifying factor is the role of immune and inflammatory responses in their development and/or progression. For example, infectious agents have been linked to pediatric cardiovascular disease, leading to a large health burden that disproportionately affects low-income areas. Other implicated mechanisms include antibody targeting of cardiac proteins, infection of cardiac cells, and inflammation-mediated damage to cardiac structures. These changes can alter blood flow patterns, change extracellular matrix composition, and induce cardiac remodeling. Therefore, understanding the relationship between the immune system and cardiovascular disease can inform targeted diagnostic and treatment approaches. In this review, we discuss the current understanding of pediatric immune-associated cardiac diseases, challenges in the field, and areas of research with potential for clinical benefit.

Shear-Regulated Extracellular Microenvironments and Endothelial Cell Surface Integrin Receptors Intertwine in Atherosclerosis

Mechanical forces imposed by blood flow shear stress directly modulate endothelial gene expression and functional phenotype. The production of extracellular matrix proteins and corresponding cell-surface integrin receptors in arterial endothelial cells is intricately regulated by blood flow patterns. Laminar blood flow promotes mature and atheroresistant endothelial phenotype, while disturbed flow induces dysfunctional and atheroprone endothelial responses. Here, we discuss how hemodynamic changes orchestrate the remodeling of extracellular microenvironments and the expression profile of the integrin receptors in endothelial cells leading to oxidative stress and inflammation. Targeting the interaction between matrix proteins and their corresponding integrins is a potential therapeutic approach for atherosclerosis.

4D flow magnetic resonance imaging to assess left atrial haemodynamics in healthy and hypertrophic subjects

Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): - University, research centre and hospital foundation grants for the contracting of new research staff (FI 2020) - Spanish Ministry of Economy and Competitiveness Retos investigacion project Introduction The assessment of the left atrium (LA) haemodynamics is key to better understand the development of LA-related pathological processes. In this regard 4D flow magnetic resonance imaging (MRI) can provide complementary information to standard Doppler echocardiographic studies and identify complex blood flow patterns. Yet, until recently, the left atrium (LA) has been largely left aside in 4D flow MRI studies. Purpose We aimed at assessing the LA haemodynamics of healthy and hypertrophic cardiomyopathy (HCM) subjects with a qualitative visualization of flow patterns and deriving quantitative indices related to ventricular dysfunction from pulmonary veins (PV) and mitral valve (MV) velocity profiles. Methods Segmentation was performed directly over 4D flow angiograms. A total of 20 cases were processed, 11 healthy and 9 HCM subjects. 4D velocity matrices were masked with the segmented mask to isolate LA haemodynamics. Velocity profiles were then obtained in the PV and MV and integrated over planes perpendicular to the lumen of the vessels to create velocity spectrograms. Fourier spectral analysis was applied to the velocity curves to highlight differences that might go unnoticed in the time domain. In addition, the Q-Criterion was computed for vortex identification, visually inspecting both cohorts across the whole cardiac cycle. Results Fourier spectral analysis of the velocity curves suggested that overall, healthy patients have higher dynamic range of the velocity curves. It can be observed in Figure 1, that the usual E/A MV velocity pattern is preserved in 10 of the 11 healthy subjects while 5 of the HCM patients present significant alterations of said curve. In fact, patients 4, 6, 7 and 8 seem to present a 3 peaked MV velocity curve. The vortex analysis identified 3 main types of vortices in healthy subjects: a ‘filling’ systolic vortex (10/11) arising near the most dominant PV (usually the left superior PV) as seen in Figure 2; a conduit phase vortex (7/11), similar in nature to the preceding systolic vortex; and an E-wave vortex (9/11) attached to the LA ostium. Four of the HCM patients (out of the five with altered MV velocity profile) also showed a systolic vortex, but with more complex blood flow patterns and emerging far from the PVs. One of such vortices is shown in Figure 2, composed of two distinct eddies near the MV. The E-wave vortex was also observed but was less predominant than in healthy subjects (3/9). Conclusions 4D Flow analysis of the LA is feasible and might hold promise in the understanding of the complex haemodynamics in ventricular dysfunction. Abstract Figure. Velocity Spectrograms and Vortices