Shape memory of human red blood cells

Area of Science:

• Biophysics
• Cell Biology
• Hematology

Background:

• Human red blood cells (RBCs) are highly deformable and return to their resting biconcave shape after external forces are removed.
• The concept of 'shape memory' in RBCs refers to the consistent reformation of the cell's rim from specific membrane regions.

Purpose of the Study:

• To investigate whether human red blood cells exhibit a memory of their biconcave shape.
• To determine the persistence and characteristics of RBC shape memory under various conditions.

Main Methods:

• The 'go-and-stop' experiment was employed to probe RBC shape memory.
• Latex spheres were used to mark specific locations on the red cell membrane.
• Shape excursions were induced using controlled shear flow, and the return to resting shape was observed.

Main Results:

• Virtually all tested red blood cells demonstrated a distinct shape memory.
• Following shear flow cessation, RBCs returned to their biconcave shape, with marked membrane regions repositioning.
• This shape memory persisted even after extensive deformation (up to 4 hours) at room temperature and 37°C.

Conclusions:

• Human red blood cells possess a robust shape memory, indicating a persistent structural characteristic.
• The characteristic time for stress relaxation in RBCs is estimated to be greater than 80 minutes.
• The findings suggest that red blood cells likely retain this shape memory in their natural in vivo environment.