Age Dependent Deformability Changes of RBCS Evaluated Using a Cyclically Reversing Shear Flow Generator

Abstract

In this study, using a cyclically reversing shear flow generator we studied deformability of blood cells separated into young and old RBCs. We investigated the relationships between aging of RBCs and its deformability sheared by a cyclically reversing flow.To study the effect of aging of cells on their mechanical properties, RBCs were separated by centrifugation according to their density. The sampled RBCs were then mixed with Dextran solution to prepare 0.15% Hematocrit RBC suspension.The RBC suspension was placed between the two parallel glass plates separated by a gap distance of 30μm under a microscope; with the bottom plate stationary, the upper plate made a reciprocal motion by cam-motor machinery (the amplitude and frequency of 1.25mm and 2, 4, and 6 Hz, respectively) creating a quasi-Couette flow of RBC suspension with the peak shear stress of 37.46 Pa. The images of RBCs were magnified by a ×40 objective lens combined with a×1.6 middle lens, and recorded by a high speed video camera. Subsequently, the RBCs images have gone through averaging, digitization, and then morphological analysis of their properties in terms of the major (L) and minor (W) axes of the projected two dimensional figures, yielding the deformation index of L/W.The L/W of both groups of RBCs followed closely the shear stress changes, exhibiting asymmetrical response patterns consisting of fast deformation or stretching and slow recovery phase. The mean L/W of young RBCs was 1.096±0.0079 times that of the old ones (p=0.0003).Our preliminary study indicated more rigid membrane properties in the old RBCs as compared with the young cells at three different shearing frequencies.