Impact of red blood cell rigidity on in vivo flow dynamics and lingering in bifurcations

Bifurcations are a crucial part of the mammalian microvasculature, as they establish the interface between blood and tissue. The flexibility of red blood cells (RBCs), the main cellular constituent of blood, is believed to strongly impact their partitioning, quantitative in vivo measurements have so far been elusive. This study investigates the effect of cell rigidity on the lateral movement after arteriole bifurcations and lingering by comparing the movement of artificially rigidified RBCs with that of healthy RBCs in vivo. Lingering describes a recently highlighted phenomenon in which RBCs reside in the bifurcation between two branches before entering either one. Our results show that increased RBC rigidity reduces lingering and, contrary to expectations, leaves healthy RBCs with a lower speed than rigidified RBCs in some areas of the microcirculation. We conclude that rigid RBCs show a different flow behavior leading to reduced wall contact potentially altering endothelial signaling and nutrient delivery and show a different partitioning at bifurcations.