Sublethal Supraphysiological Shear Stress Alters Erythrocyte Dynamics in Subsequent Low-Shear Flows

Area of Science:

• Biophysics
• Hematology
• Fluid Mechanics

Background:

• Blood's non-Newtonian, shear-thinning behavior is primarily due to red blood cell (RBC) properties.
• RBCs deform, disaggregate, and orient with flow under increased shear, enhancing blood fluidity.
• Previous studies suggested supraphysiological shear exposure paradoxically increases RBC deformability under low shear, possibly due to artifacts.

Purpose of the Study:

• To investigate the mechanical responses of RBCs to shear flow after prior shear exposure (PSE).
• To differentiate true changes in RBC mechanics from potential methodological artifacts.
• To elucidate the impact of shear stress history on RBC behavior.

Main Methods:

• Utilized purpose-built laser diffractometry combined with direct optical visualization.
• Exposed fresh RBCs to a standardized prior shear exposure (PSE) of 100 Pa × 300 s.
• Analyzed RBC deformability and orientation under stepwise shear stress (0.3–5.0 Pa) in a custom slit-flow chamber.

Main Results:

• PSE RBCs exhibited significantly decreased deformability (visualized and laser-derived) at shear stresses ≥1 Pa.
• Demonstrated increased heterogeneity in RBC orientation with the flow vector for PSE cells across all shear levels.
• Observed potential increased vorticity and instability in PSE RBCs at 5 Pa shear stress.

Conclusions:

• Prior shear exposure significantly impairs RBC deformability and alters cell orientation dynamics.
• Shear stress history impacts subsequent RBC behavior, particularly in low-shear environments.
• Findings offer insights into microvascular disorders associated with mechanical circulatory support and hematological diseases.