Abstract

We demonstrate that erythrocyte deformations, specifically of a type as occur in splenic flow (Zhu et al., 2017), and of the type that promote vesiculation can be caused by simple, yet tailored, oscillatory shear flow. We show that such oscillatory shear flow provides an ideal environment to explore a wide variety of metabolic and biochemical effects that promote erythrocyte vesiculation. Deformation details, typical of splenic flow, such as in-folding and implications for membrane/skeleton interaction are demonstrated and quantitatively analyzed. We introduce a theoretical, essentially analytical, vesiculation model that directly couples to our more complex numerical, multilevel, model that clearly delineates various fundamental elements, i.e., sub-processes, that are involved and mediate the vesiculation process. This analytical model highlights particulary important vesiculation precursors such as areas of membrane/skeleton disruptions that trigger the vesiculation process. We demonstrate, using flow cytometry, that the deformations we experimentally induce on cells, and numerically simulate, do not induce lethal forms of cell damage but do induce vesiculation as theoretically forecasted. This, we demonstrate, provides a direct link to cell membrane/skeletal damage such as is associated with metabolic and aging damage. An additional noteworthy feature of this approach is the avoidance of artificial devices, e.g., micro-fluidic chambers, in which deformations and their time scales are often unrepresentative of physiological processes such as splenic flow.

Highlights

  • AND BACKGROUNDWithout a nucleus, a mature erythrocyte contains a cytosol enclosed within a highly flexible cell membrane

  • The basic picture is that of a skeleton created from junctional complexes (JCs) bound to each other via head-tohead associations of spectrin (Sp), which is anchored to the fluidic lipid bilayer at linkage sites (Mohandas and Evans, 1994; Mohandas and Gallager, 2008; Lux, 2015)

  • With the numerology used here we find that predominantly vesicles are expected in the size range 100nm hv 200nm; vesicles as small as hv ∼ 40 − 50nm are possible if sufficient driving energy, ǫ0 is available

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Summary

Introduction

AND BACKGROUNDWithout a nucleus, a mature erythrocyte (or RBC) contains a cytosol enclosed within a highly flexible cell membrane. As the trans-membrane attachment proteins have finite (but documented) mobility, the process of changing skeletal density has its own time scale that operates within the deformation’s time scale; this too was predicted (see Zhu et al, 2017 and its discussion of the results of Peng et al, 2010, 2011; Peng and Zhu, 2013) In this we find that deformation processes in splenic flow, such as what we have dubbed in-folding, produce a “tension” (dubbed negative pressure in Zhu et al, 2017) between the skeleton and membrane that can promote separation that leads to vesiculation (Zhu et al, 2017). Since areal density reduction of attachments does not occur in time during splenic flow deformation restructuring, it must occur by metabolically induced disruption of anchorage points

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