Effects of fluid–cell–vessel interactions on the membrane tensions of circulating tumor cells in capillary blood flows

The membrane tensions of suspended nucleated cells moving in blood flows in capillary networks are quite different from those of spreading cells, a fact that is crucial to many pathological processes, such as the metastasis of cancers via circulating tumor cells (CTCs). However, a few studies have examined membrane tensions in suspended cells, especially when interacting with other cells of different stiffnesses in low-Reynolds number flows at the cellular level. Taking CTCs as an example, we use the immersed boundary method to analyze the relationship between membrane tensions and their motional behaviors under the influence of fluid–cell–vessel interactions. The effects of vessel diameter and hematocrit on the shear tension and average isotropic tension are also analyzed. The results suggest that the confinement of the vessel wall determines membrane tensions on CTCs until the ratio of the vessel diameter to cell size becomes slightly larger than unity, at which point cell–cell interactions become the crucial factor. The increase in interactions between red blood cells and CTCs with the increase in the hematocrit in larger vessels promotes membrane tensions not only through the migration of CTCs to the vessel wall but also through a reduction in the translational motion and rotation of CTCs. The present study provides support rooted in biofluid mechanics for mechanobiological research on the metastasis and apoptosis of CTCs in microvessels.