Morphological changes in erythrocytes of people with type 2 diabetes mellitus evaluated with atomic force microscopy: A brief review

Prevalence of type 2 diabetes mellitus (T2DM) has been increasing worldwide. Cardiovascular diseases are one of the main causes of death among people with T2DM. Morphological changes in erythrocytes have been associated with higher risk of cardiovascular diseases. Atomic force microscopy (AFM) is a new technique that allows non-invasive imaging of cells and the evaluation of changes in mechanical properties.

AIM

To evaluate by AFM the erythrocytes morphological changes of people with T2DM METHODS: Search was conducted from in PubMed, ScienceDirect, Scielo, and Lilacs. Erythrocyte, type 2 Diabetes Mellitus and, Microscopy, Atomic Force were the keywords used for the search. Papers included were cross-sectional studies performed in humans.

RESULTS

Five of seven articles fulfilled the inclusion criteria. Compared with healthy cells, the erythrocytes from individuals affected by T2DM had morphological changes such as a decreased concave depth, diameter, height and a deformation index, while axial ratio, stiffness, adhesive force, aggregation, and rigidity index were increased. The results regarding the erythrocyte roughness were inconclusive.

CONCLUSIONS

The AFM is an excellent instrument to study the altered erythrocytes of subjects affected by T2DM. Morphology changes in erythrocytes could lead to cardiovascular events, which are major complications in people living with this disease.

An Enhanced Spring-Particle Model for Red Blood Cell Structural Mechanics: Application to the Stomatocyte–Discocyte–Echinocyte Transformation

Red blood cells (RBCs) are the most abundant cellular element suspended in blood. Together with the usual biconcave-shaped RBCs, i.e., discocytes, unusual-shaped RBCs are also observed under physiological and experimental conditions, e.g., stomatocytes and echinocytes. Stomatocytes and echinocytes are formed from discocytes and in addition can revert back to being discocytes; this shape change is known as the stomatocyte–discocyte–echinocyte (SDE) transformation. To-date, limited research has been conducted on the numerical prediction of the full SDE transformation. Spring-particle RBC (SP-RBC) models are commonly used to numerically predict RBC mechanics and rheology. However, these models are incapable of predicting the full SDE transformation because the typically employed bending model always leads to numerical instability with severely deformed shapes. In this work, an enhanced SP-RBC model is proposed in order to extend the capability of this model type and so that the full SDE transformation can be reproduced. This is achieved through the leveraging of an advanced bending model. Transformed vesicle and RBC shapes are predicted for a range of reduced volume and reduced membrane area difference (MAD), and very good agreement is obtained in the comparison of predicted shapes with experimental observations. Through these predictions, vesicle and SDE transformation phase diagrams are developed and, importantly, in the SDE case, shape boundaries are proposed for the first time relating RBC shape categories to RBC reduced volume and reduced MAD.

Time-dependent surface adhesive force and morphology of RBC measured by AFM

Atomic force microscopy (AFM) is a rapidly developing tool recently introduced into the evaluation of the age of bloodstains, potentially providing legal medical experts useful information for forensic investigation. In this study, the time-dependent, morphological changes of red blood cells (RBC) under three different conditions (including controlled, room-temperature condition, uncontrolled, outdoor-environmental condition, and controlled, low-temperature condition) were observed by AFM, as well as the cellular viscoelasticity via force-vs-distance curve measurements. Firstly, the data indicate that substrate types have different effects on cellular morphology of RBC. RBC presented the typical biconcave shape on mica, whereas either the biconcave shape or flattened shape was evident on glass. The mean volume of RBCs on mica was significantly larger than that of cells on glass. Surprisingly, the adhesive property of RBC membrane surfaces was substrate type-independent (the adhesive forces were statistically similar on glass and mica). With time lapse, the changes in cell volume and adhesive force of RBC under the controlled room-temperature condition were similar to those under the uncontrolled outdoor-environmental condition. Under the controlled low-temperature condition, however, the changes in cell volume occurred mainly due to the collapse of RBCs, and the curves of adhesive force showed the dramatic alternations in viscoelasticity of RBC. Taken together, the AFM detections on the time-dependent, substrate type-dependent, environment (temperature/humidity)-dependent changes in morphology and surface viscoelasticity of RBC imply a potential application of AFM in forensic medicine or investigations, e.g., estimating age of bloodstain or death time.

An easy method to discover cell membrane antigen with atomic force microscopy

Atomic force microscopy (AFM) obtains a high resolution at nanometer. In the current study, we found that, before and after adding CD34, CD44 or CD29 antibodies, the AFM images of mouse adipose tissue derived mesenchymal stem cells (ADMSCs) had significant changes in both cell morphous (shape) and the average roughness of cell membrane. However, there was no significant difference in the cell shape and the average roughness of cell membrane, after adding CD45 or CD144 antibodies. Therefore, we could use the AFM to scan cell shape or to calculate the average roughness changes of cell membrane to analyze the existence of cell membrane antigen qualitatively.

Membrane deformation of unfixed erythrocytes in air with time lapse investigated by tapping mode atomic force microscopy

Estimation of the time of death is one of the most important problems for forensic medicine and law. Physical and chemical postmortem changes are evaluated together while estimating the time of death. The pattern analysis of antemortem and postmortem bloodstains is one of the important parameters for forensic science, and cellular changes of blood cells can be useful for the quantitative assessment of the time of death. In this study, by successively investigating erythrocytes exposed in air on mica for 5 days using tapping mode atomic force microscopy (TM-AFM), we observed deformation of whole cell and membrane surface of unfixed erythrocytes with time lapse. We found that the time-dependent cellular changes occurred after exposure of erythrocytes in air for several days. At 0.5 days of exposure, fissures and cell shrinkage were observed. At 2.5 days of exposure, the emergence of nanometer-scale protuberances were observed and these protuberances increased in number with increasing time. The changes of cell shape and cell membrane surface ultrastructure can be used to estimate the time of death. Futhermore, smear-induced abnormal erythrocytes and immunostained erythrocytes were observed here. The need for more precise research is indicated, such as the correlation of membrane changes to intervals of less than 0.5 day of air exposure, and use of various substrates in addition to mica, including glass, metals, fabrics, among others, on which the bloodstains appear in crime scenes. The results of this research demonstrate the efficacy of AFM as a potentially powerful analytical tool in forensic science.