Stiffening of Red Blood Cells Induced by Cytoskeleton Disorders: A Joint Theory-Experiment Study

Abstract

The functions and elasticities of the cell are largely related to the structures of the cytoskeletons underlying the lipid bilayer. Among various cell types, the red blood cell (RBC) possesses a relatively simple cytoskeletal structure. Underneath the membrane, the RBC cytoskeleton takes the form of a two-dimensional triangular network, consisting of nodes of actins (and other proteins) and edges of spectrins. Recent experiments focusing on the malaria-infected RBCs (iRBCs) show that there is a correlation between the elongation of spectrins in the cytoskeletal network and the stiffening of the iRBCs. Here we rationalize the correlation between these two observations by combining the wormlike chain model for single spectrins and the effective medium theory for the network elasticity. We specifically focus on how the disorders in the cytoskeletal network affect its macroscopic elasticity. Analytical and numerical solutions from our model reveal that the stiffness of the membrane increases with increasing end-to-end distances of spectrins, but has a nonmonotonic dependence on the variance of the end-to-end distance distributions. These predictions are verified quantitatively by our atomic force microscopy and micropipette aspiration measurements of iRBCs. The model may, from a molecular level, provide guidelines for future identification of new treatment methods for RBC-related diseases, such as malaria infection.

Tuning of Differential Lipid Order Between Submicrometric Domains and Surrounding Membrane Upon Erythrocyte Reshaping

“…This is exactly what we observed in RBCs of the patient suffering from spherocytosis included in this study, which exhibit an increased spectrin network density (unpublished; confocal and transmission electron microscopy). It remains to be determined how interactions with anchorage complexes are also affected in these spherocytotic RBCs, but theoretical studies show that the loss of the spectrin:membrane anchorage stiffens the cytoskeleton [40,55]. These spherocytotic RBCs also have a higher Cellular Physiology and Biochemistry Cellular Physiology and Biochemistry content of intracellular calcium, known to increase the connectivity of the RBC cytoskeleton [56], and resulting in higher membrane compression [57].…”

Investigation of red blood cell mechanical properties using AFM indentation and coarse-grained particle method

“…This allows investigation of the mechanical aspects that define RBC behaviour at a much smaller scale than is possible with experimentation, which becomes challenging and costly [ 22 ]. Studying elasticity of the RBC membrane at this level can provide insight on the state of the membrane and how structural changes and defects impact on physical characteristics of the cells [ 23 ]. Structural transformations within the membrane are known to occur naturally as RBCs age, also as a result of underlying conditions such as malaria, sickle cell trait and hereditary diseases [ 10 , 13 ], and even during the storage of RBCs before transfusion [ 24 ].…”

Aberrant Membrane Composition and Biophysical Properties Impair Erythrocyte Morphology and Functionality in Elliptocytosis

“…Moreover, reorganization of cytoskeleton:membrane anchorage complexes was revealed by the presence of areas of reduced density alternating with darker areas and by the decreased spatial dissociation between CD47 and glycophorin C, respectively enriched in the ankyrin- and 4.1R- based complexes. Although it remains to determine how altered interactions with anchorage complexes impair elasticity in pEl RBCs, theoretical studies show that the loss of the spectrin:membrane anchorage stiffens the cytoskeleton [ 46 , 47 ]. Hence, the decreased content of PS, a phospholipid normally retained in the inner leaflet and involved in the membrane:cytoskeleton interaction at the 4.1R complexes, and the increased membrane retention of hemoglobin could both contribute to cytoskeleton elasticity impairment.…”