CFD analysis on blood flow inside a symmetric stenosed artery: Physiology of a coronary artery disease

Impact of hematocrit on pulsatile blood flow in stenosed arteries: a computational study in healthy, diabetic, and anemic models

In this study, researchers aim to enhance the realism of circulatory system simulations, focusing on factors affecting flow variations, particularly in stenotic arteries of individuals with altered hematocrit levels. Through extensive data collection and varied conditions, the goal is to attain more precise and valid results. The study conducts approximate simulations to comprehensively describe the dynamic motion of pulsatile flow. Different values of inlet velocity (UDF) are introduced, considering potential arterial distortion or occlusion due to plaque deposition, along with variations in hematocrit (Hct) levels commonly observed in patients. Three distinct types of pulsatile blood flow, corresponding to diabetes (Hct 65%), healthy (Hct 45%), and anemia (Hct 25%), are studied and compared. The research illuminates that stenosis in arteries with varying hematocrit levels significantly impacts hydrodynamic features, potentially predisposing individuals to cardiovascular diseases. Through meticulous analysis, several conclusions about hemodynamic characteristics are drawn. It is observed that both velocity and wall shear stress exhibit variation along the affected artery, influenced by stenosis and changes in hematocrit levels. Notably, the highest influence on velocity and wall shear stress is observed with Hct 65%, compared to Hct 45% and Hct 25% at the moment of stenosis. These findings hold substantial practical implications for the field of cardiovascular health, providing valuable insights into blood flow behavior in stenotic arteries with diverse hematocrit levels. Ultimately, this research contributes to more effective clinical interventions.

HSPA12A acts as a scaffolding protein to inhibit cardiac fibroblast activation and cardiac fibrosis

INTRODUCTION

Cardiac fibrosis is the main driver for adverse remodeling and progressive functional decline in nearly all types of heart disease including myocardial infarction (MI). The activation of cardiac fibroblasts (CF) into myofibroblasts is responsible for cardiac fibrosis. Unfortunately, no ideal approach for controlling CF activation currently exists.

OBJECTIVES

This study investigated the role of Heat shock protein A12A (HSPA12A), an atypical member of the HSP70 family, in CF activation and MI-induced cardiac fibrosis.

METHODS

Primary CF and Hspa12a knockout mice were used in the experiments. CF activation was indicated by the upregulation of myofibroblast characters including alpha-Smooth muscle actin (αSMA), Collagen, and Fibronectin. Cardiac fibrosis was illustrated by Masson's trichrome and picrosirius staining. Cardiac function was examined using echocardiography. Glycolytic activity was indicated by levels of extracellular lactate and the related protein expression. Protein stability was examined following cycloheximide and MG132 treatment. Protein-protein interaction was examined by immunoprecipitation-immunoblotting analysis.

RESULTS

HSPA12A displayed a high expression level in quiescent CF but showed a decreased expression in activated CF, while ablation of HSPA12A in mice promoted CF activation and cardiac fibrosis following MI. HSPA12A overexpression inhibited the activation of primary CF through inhibiting glycolysis, while HSPA12A knockdown showed the opposite effects. Moreover, HSPA12A upregulated the protein expression of transcription factor p53, by which mediated the HSPA12A-induced inhibition of glycolysis and CF activation. Mechanistically, this action of HSPA12A was achieved by acting as a scaffolding protein to bind p53 and ubiquitin specific protease 10 (USP10), thereby promoting the USP10-mediated p53 protein stability and the p53-medicated glycolysis inhibition.

CONCLUSION

The present study provided clear evidence that HSPA12A is a novel endogenous inhibitor of CF activation and cardiac fibrosis. Targeting HSPA12A in CF could represent a promising strategy for the management of cardiac fibrosis in patients.

Effect of turbulence and viscosity models on wall shear stress derived biomarkers for aorta simulations

Ascending aorta simulations provide insight into patient-specific hemodynamic conditions. Numerous studies have assessed fluid biomarkers which show a potential to aid clinicians in the diagnosis process. Unfortunately, there exists a large disparity in the computational methodology used to model turbulence and viscosity. Recognizing this disparity, some authors focused on analysing the influence of either the turbulence or viscosity models on the biomarkers in order to quantify the importance of these model choices. However, no analysis has yet been done on their combined effect. In order to fully understand and quantify the effect of the computational methodology, an assessment of the combined effect of turbulence and viscosity model choice was performed. Our results show that (1) non-Newtonian viscosity has greater impact (2.9-5.0%) on wall shear stress than Large Eddy Simulation turbulence modelling (0.1-1.4%), (2) the contribution of non-Newtonian viscosity is amplified when combined with a subgrid-scale turbulence model, (3) wall shear stress is underestimated when considering Newtonian viscosity by 2.9-5.0% and (4) cycle-to-cycle variability can impact the results as much as the numerical model if insufficient cycles are performed. These results demonstrate that, when assessing the effect of computational methodologies, the resultant combined effect of the different modelling assumptions differs from the aggregated effect of the isolated modifications. Accurate aortic flow modelling requires non-Newtonian viscosity and Large Eddy Simulation turbulence modelling.