Preliminary classification criteria for the cryoglobulinaemic vasculitis

TLDR

RBC deformability depends on membrane viscoelasticity, cell contents, and SA:V ratio, but it is unclear which factor most determines passage through small capillaries. The authors used a microfluidic device to test traversal of various RBCs and developed a finite‑element model of the nonlinear mechanical behavior of the RBC membrane skeleton to explain the observations. They found that stiffening does not affect traversal, whereas a moderate reduction in SA:V ratio markedly limits the diameter of channels RBCs can pass, indicating SA:V ratio should be prioritized in RBC pathology studies.

Abstract

<h3>Summary</h3> The remarkable deformability of red blood cells (RBCs) depends on the viscoelasticity of the plasma membrane and cell contents and the surface area to volume (SA:V) ratio; however, it remains unclear which of these factors is the key determinant for passage through small capillaries. We used a microfluidic device to examine the traversal of normal, stiffened, swollen, parasitised and immature RBCs. We show that dramatic stiffening of RBCs had no measurable effect on their ability to traverse small channels. By contrast, a moderate decrease in the SA:V ratio had a marked effect on the equivalent cylinder diameter that is traversable by RBCs of similar stiffness. We developed a finite element model that provides a coherent rationale for the experimental observations, based on the nonlinear mechanical behaviour of the RBC membrane skeleton. We conclude that the SA:V ratio should be given more prominence in studies of RBC pathologies.