title: Increased erythrocyte adhesion to VCAM-1 during pulsatile flow: Application of a microfluidic flow adhesion bioassay.
abstract: Sickle cell disease (SCD) is characterized by microvascular occlusion mediated by adhesive interactions of sickle erythrocytes (SSRBCs) to the endothelium. Most in vitro flow adhesion assays measure SSRBC adhesion during continuous flow, although in vivo SSRBC adhesive interactions occur during pulsatile flow. Using a well-plate microfluidic flow adhesion system, we demonstrate that isolated SSRBCs adhere to vascular cell adhesion molecule (VCAM-1) at greater levels during pulsatile versus continuous flow. A significant increase in adhesive interactions was observed between all pulse frequencies 1 Hz to 2 Hz (60-120 beats/min) when compared to non-pulsatile flow. Adhesion of isolated SSRBCs and whole blood during pulsatile flow was unaffected by protein kinase A (PKA) inhibition, and exposure of SSRBCs to pulsatile flow did not affect the intrinsic adhesive properties of SSRBCs. The cell type responsible for increased adhesion of whole blood varied from patient to patient. We conclude that low flow periods of the pulse cycle allow more adhesive interactions between sickle erythrocytes and VCAM-1, and sickle erythrocyte adhesion in the context of whole blood may better reflect physiologic cellular interactions. The microfluidic flow adhesion bioassay used in this study may have applications for clinical assessment of sickle erythrocyte adhesion during pulsatile flow.
authors.affiliation: Department of Pediatrics, Wayne State University School of Medicine, Detroit, MI, USA.
authors.forename: Jennell
authors.initials: J
authors.lastname: White
authors.affiliation: Division of Hematology/Oncology, Children's Hospital of Michigan, Detroit, MI, USA.
authors.forename: Moira
authors.initials: M
authors.lastname: Lancelot
authors.affiliation: Division of Hematology/Oncology, Children's Hospital of Michigan, Detroit, MI, USA.
authors.forename: Sharada
authors.initials: S
authors.lastname: Sarnaik
authors.affiliation: Department of Pediatrics, Wayne State University School of Medicine, Detroit, MI, USA.|Division of Critical Care Medicine, Children's Hospital of Michigan, Detroit, MI, USA.|Department of Physiology, Wayne State University School of Medicine, Detroit, MI, USA.
authors.forename: Patrick
authors.initials: P
authors.lastname: Hines
mesh_terms: D000293:Adolescent; D000755:Anemia, Sickle Cell / Q000097:blood*; D002448:Cell Adhesion; D002648:Child; D002675:Child, Preschool; D004730:Endothelium, Vascular / Q000166:cytology; D006801:Humans; D044085:Microfluidics / Q000379:methods*; D011673:Pulsatile Flow; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism*
chemical_list: D019010:Vascular Cell Adhesion Molecule-1
keywords: Pulsatile flow; VCAM-1; VLA-4; adhesion; erythrocyte; microfluidics; sickle cell disease; variable shear