Optical techniques for assessing blood microrheology: red blood cells deformability, aggregation and their interrelation

Abstract

The state of human organism largely depends on blood microcirculation that, in turn, depends on the microrheologic properties of red blood cells (RBCs), in particular, the RBC intrinsic properties of deformability and aggregation that are supposed to be interdependent [1]. The RBCs have the ability to reversibly deform in the blood flow. Usually they elongate in the direction of the flow but, also, they can change their shape dramatically in the vessels that are smaller than the size of the RBCs, for example, capillaries with diameters from 3 to 5 μm [2]. A considerable contribution to the deformability comes from the elasticity of the cell membrane, as well as from the viscosity of hemoglobin solution inside the cell [3]. RBC deformability plays a significant role in the blood circulation. In particular, RBC filtering in narrow circulatory pathways in the human spleen is based on their impaired deformability. Another important process that influences the blood flow is the aggregation of RBCs [4]. It is a reversible process of formation of linear and more complex structures of RBCs. The aggregation happens predominantly inside large vessels. However, the aggregates can become quite large, and if not their ability to disaggregate to single cells due to shear stress, the blood flow would be impaired.
Socially significant diseases such as arterial hypertension, diabetes mellitus and others are associated with serious changes in the RBC deformability [4-6]. At the same time a significant change in the aggregation parameters may happen [4]. For example, RBC aggregates in the blood of patients suffering from arterial hypertension are stronger and form faster than in the blood of healthy people [6]. Moreover, these pathologies are accompanied by an alteration in the number of RBC involved in the process of spontaneous aggregation. This can be caused by many reasons: a change in the protein composition of plasma, cell membrane changes, different rigidity and age of the cells, as well as the average patient age and their medication, etc. [4].
The aim of this work is to identify the relationship between the deformability of RBCs and their aggregation properties, both of which are the key factors for the blood flow. Laser diffractometry, diffuse light scattering and laser tweezers were implemented for in vitro measurements.
Different osmolarities of plasma (150–500 mOsm/l) and concentrations of glutaraldehyde (GA) (up to 0.004%) were used to change the deformability of the RBCs in vitro. The measurements were performed at 37 °C. The study was conducted on the blood of 2 healthy donors. The values of AI, DI and the forces of RBC interaction were measured 5 times for the same sample. The results were then averaged and the standard deviations from the mean values were calculated.
The method of laser diffractometry confirmed that with the addition of glutaraldehyde and with a large change in the osmolarity of the solution, RBCs become more rigid. Secondly, the methods of laser aggregometry and laser tweezers gave consistent results: with the decreased ability of RBCs to deform the formation of aggregates becomes impaired. However, the critical shear stress and the disaggregation force measured with laser tweezers remain mostly unchanged. This means that the RBC aggregate formation is dependent on the deformability of the membrane, while the connection to disaggregation is less pronounced and more complicated in nature.

Acknowledgement: This work was supported by the Russian Foundation for Basic Research grant #19-52-51015.

[1] V. Leftov, S. Regirer, and N. Shadrina, Blood Rheology, Meditsina, Moscow, 1982 [in Russian].
[2] V. V. Tuchin (Ed.), Handbook of Optical Biomedical Diagnostics, Vol. 1. Chapter 2, Optics of Blood, SPIE Press, Bellingham, Washington, USA, 2016.
[3] N. Firsov, A. Priezzhev, N. Klimova, and A. Tyurina, Fundamental laws of the deformational behavior of erythrocytes in shear flow, J. of Engineering Physics and Thermophysics 79(1), 118–124, 2006.
[4] O. Baskurt, B. Neu, and H. Meiselman, Red Blood Cell Aggregation, CRC Press, 2012.
[5] A. Lugovtsov, Y. I. Gurfinkel, P. B. Ermolinskiy, A. I. Maslyanitsina, L. I. Dyachuk, and A. V. Priezzhev, Optical assessment of alterations of microrheologic and microcirculation parameters in cardiovascular diseases, Biomedical Optics Express 10(8), 3974–3986, 2019.
[6] P. Ermolinskiy, A. Lugovtsov, A. Maslyanitsina, A. Semenov, L. Dyachuk, and A. Priezzhev, Interaction of erythrocytes in the process of pair aggregation in blood samples from patients with arterial hypertension and healthy donors: measurements with laser tweezers, Journal of Biomedical Photonics & Engineering 4(3), 030303, 2018.

Speaker

Andrei Lugovtsov
Physics Department and International Laser Center, Lomonosov Moscow State University
Russia

Discussion

Ask question