Changes in Red Blood Cell Membrane Structure in Type 2 Diabetes

A Scanning Electron and Atomic Force Microscopy Study

Antoinette V Buys; Mia-Jean Van Rooy; Prashilla Soma; Dirk Van Papendorp; Boguslaw Lipinski; Etheresia Pretorius

Disclosures

Cardiovasc Diabetol. 2013;12(25) 

In This Article

Abstract and Introduction

Abstract

Red blood cells (RBCs) are highly deformable and possess a robust membrane that can withstand shear force. Previous research showed that in diabetic patients, there is a changed RBC ultrastructure, where these cells are elongated and twist around spontaneously formed fibrin fibers. These changes may impact erythrocyte function. Ultrastructural analysis of RBCs in inflammatory and degenerative diseases can no longer be ignored and should form a fundamental research tool in clinical studies. Consequently, we investigated the membrane roughness and ultrastructural changes in type 2 diabetes. Atomic force microscopy (AFM) was used to study membrane roughness and we correlate this with scanning electron microscopy (SEM) to compare results of both the techniques with the RBCs of healthy individuals. We show that the combined AFM and SEM analyses of RBCs give valuable information about the disease status of patients with diabetes. Effectiveness of treatment regimes on the integrity, cell shape and roughness of RBCs may be tracked, as this cell's health status is crucial to the overall wellness of the diabetic patient.

Introduction

The erythrocyte is a unique anuclear cell, with a cytoplasm consisting of 95% hemoglobin, the protein responsible for oxygen transfer from the lungs to the rest of the body. For the erythrocyte to transport haemoglobin and subsequently oxygen to all cells, it must travel through the circulatory system, including the microcirculation, where it encounters small capillary spaces and high shear stresses. In order for the cell to be able to survive this, a highly deformable yet robust membrane is required. The erythrocyte membrane consists of an overlaying asymmetric phospholipid bilayer membrane, supported by an underlying spectrin-actin cytoskeletal complex which is interconnected by junctional complexes resulting in a simple hexagonal geometric matrix. The plasma membrane is anchored to the spectrin network mainly by proteins ankyrin and the transmembrane protein band 3 and 4.1.[1,2]

It is generally believed that the plasma membrane together with its cytoskeletal support is responsible for the maintenance of the shape and stability of the cell and also for allowing extensive deformations when needed.[3] Furthermore, the roughness of the cell membrane is a very interesting indicator of cell's health state.[4] Modifications of the lipid composition and the asymmetry of the bilayer have been shown to affect the overall shape of the erythrocyte and also the cell's deformability. Alterations of the cytoskeletal proteins that connect the bilayer and the spectrin network, impact on particularly the erythrocyte membrane integrity, when encountering shear stresses.[5] Changes in the shape, mechanical characteristics or the integrity of the erythrocyte has severe implications on the functionality of the cell, as can be seen in several dysfunctional states of the erythrocyte, whether it is environmentally induced, due to hereditary defects or diseased states.[3] More specifically, researchers have suggested that the cell-membrane skeleton integrity measured as surface roughness is well correlated to the functional status of the cell, with a decrease of the membrane roughness seen in cells from diseased individuals.[2,3] Artificially induced injury to erythrocytes, shows a relationship between cytoskeleton integrity and membrane roughness. Other types of blood cells also show changes in membrane roughness during disease; for example, cell membranes of T-lymphocytes in thyroid associated ophthalmopathy.[6]

Previous research by our team showed that in diabetic (Type 2) patients, there is a changed RBC ultrastructure, suggested to be caused by iron overload and subsequent non-enzymatic fibrinogen polymerization.[7] These changes are specifically due to inflammation in this condition, which is associated with thrombotic events.[8,9] Furthermore, diabetes is associated with disturbed erythrocyte membrane architecture and functions of erythrocytes at molecular scale may be compromised.[10] Previously, we have shown that in these patients, the RBCs are elongated and twist around spontaneously formed fibrin fibers when a RBC smear is studied. These fibrin fibers may become thickened matted fibrin masses and may be the cause of the thrombotic events[11] and we also noted that the RBCs intertwine with the fibrin and they have a changed membrane ultrastructure.

Due to this observation, the current study investigates the membrane roughness and changes in diabetes using atomic force microscopy (AFM). We correlate this with scanning electron microscopy (SEM) results and compare results from both the techniques with the RBCs of healthy individuals.

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