Red blood cell adhesion to heme‐activated endothelial cells reflects clinical phenotype in sickle cell disease

Abstract

In sickle cell disease (SCD), 'disease severity' associates with increased RBC adhesion to quiescent endothelium, but the impact on activated endothelium is not known. Increased concentrations of free heme result from intravascular hemolysis in SCD. Heme is essential for aerobic metabolism, and plays an important role in numerous biological processes. Excess free heme induces reactive oxygen species generation and endothelial activation, which are associated with cardiovascular disorders including atherosclerosis, hypertension, and thrombosis. Here, we utilized an endothelialized microfluidic platform (Endothelium-on-a-chip) to assess adhesion of sickle hemoglobin-containing red blood cells (HbS RBCs), from adults with homozygous SCD, to heme-activated human endothelial cells (EC) in vitro. Confluent EC monolayers in microchannels were treated with pathophysiologically relevant levels of heme in order to simulate the highly hemolytic intravascular milieu seen in SCD. RBC adhesion to heme-activated ECs varied from subject to subject, and was associated with plasma markers of hemolysis (LDH) and reticulocytosis, thereby linking those RBCs that are most likely to adhere with those that are most likely to hemolyze. These results re-emphasize the critical contribution made by heterogeneous adhesive HbS RBCs to the pathophysiology of SCD. We found that adhesion of HbS RBCs to heme-activated ECs varied amongst individuals in the study population, and associated with biomarkers of hemolysis and inflammation, age, and a recent history of transfusion. Importantly, the microfluidic approach described herein holds promise as a clinically feasible Endothelium-on-a-chip platform with which to study complex heterocellular adhesive interactions in SCD. This article is protected by copyright. All rights reserved.

The Effect of Use of Individualized Pain Plans in Sickle Cell Patients Presenting to the Emergency Department

“…Perhaps patients with comorbid hypertension had increased hemolysis, leading to generation of reactive oxygen species and endothelial adhesion by free heme, making it also more likely to have higher clinical severity of pain. 7 Autonomic dysfunction could also explain the relationship between hypertension and vaso-occlusive crisis. Patients with SCD are more likely to have cardiac autonomic dysfunction with a propensity for sympathetic activation.…”

Whole blood viscosity and red blood cell adhesion: Potential biomarkers for targeted and curative therapies in sickle cell disease

“…Fabrication of microfluidic chips was performed as previously described. [49][50][51][52] Briefly, a double-sided adhesive (DSA) polyester film was placed in between a top polymethyl methacrylate (PMMA) cover, and a bottom glass microscope slide pre-coated with 3-aminopropyl triethoxysilane (APTES, Gold Seal Electron Microscopy Sciences, Hatfield, PA). The DSA film and PMMA top cover were laser micro-machined to define the microchannel walls as well as inlet and outlet ports.…”

End points for sickle cell disease clinical trials: patient-reported outcomes, pain, and the brain

“…Measuring only 1 aspect of rheology can be misleading, for example, the senicapoc trial, 150 dense cells were reduced but pain events increased, likely due to increases in whole-blood viscosity. A more global picture using a microfluidic system may provide multiple measures of blood rheology simultaneously: adhesion, deformability, and viscosity, 151,152 although there is no evidence as yet that microfluidic measurements are useful biomarkers.…”