Many hematologic conditions present with red blood cells (RBCs) of altered deformability, which can be difficult to measure. A study published in the American Journal of Hematology demonstrated a new method to measure single cell RBC deformability.
The researchers used a microfluidic device made of polydimethylsiloxane that was fitted with a 64-channel microvasculature network. This network mimicked a capillary bed with channel dimensions of 5.89 µm mean width, 13.3 µm height, and 130 µm length. The microfluidic device was coupled to a computer running the UmUTracker particle detection program in MATLAB, which processed video footage of RBCs traveling through the network and tracked RBC sizes and velocities in transit.
The researchers extracted fresh blood from 6 healthy donors, 7 patients with sickle cell disease (SCD), and 1 patient with beta thalassemia major. These samples, samples of glutaraldehyde-stiffened blood, and stored, packed blood samples were all measured using the microfluidic device. Single cell deformability index (sDI) values were derived based on the average velocity in µm/s of each RBC traveling through the microvasculature network.
Over 6 independent experiments for each set of samples, RBCs from healthy donors showed a mean sDI of 183.5 ± 18.3 µm/s, while RBCs from patients with SCD treated with hydroxyurea showed a mean sDI of 120.5 ± 32.9 µm/s, reflecting poorer deformability in patients with SCD (P <.001). Glutaraldehyde-stiffened blood showed a mean sDI of 156.9 ± 10.6 µm/s.
Stored, packed blood lost deformability with time. While average sDIs for the patient with beta thalassemia varied only slightly, peak sDI shifted higher with each transfusion before drifting downward.
The authors noted that RBC deformability decreased exponentially over time. They suggested future studies are warranted to elucidate the optimal methods of blood storage and to examine clinical and biological associations with RBC deformability.
1. Guruprasad P, Mannino RG, Caruso C, et al. Integrated automated particle tracking microfluidic enables high-throughput cell deformability cytometry for red cell disorders [published online November 12, 2018]. Am J Hematol. doi: 10.1002/ajh.25345