ИСТИНА

Blood microbiology is essentially determined by the properties of blood plasma and the interaction between blood cells, i.e., the aggregation of red blood cells (RBCs), the interaction between different blood cells and endothelium, etc. Endothelial cells do not only act as an insulating layer between blood and tissues, but also play an important role in controlling the blood flow and influence blood cell properties, e.g., RBCs aggregation. RBCs can reversibly interact with each other under low shear stress forces forming linear and more complex structures. RBCs aggregation is mainly responsible for the non-Newtonian behavior of blood and regulates the microcirculation of blood in human body. Blood microrheology and its microcirculation are determined by the composition of blood plasma, deformability and interaction of blood cells, in particular, aggregation of RBCs and interaction between blood cells and endothelium. Endothelial cells (EC) covering the walls of blood vessels play an important role in regulating blood flow and also affect the properties of blood cells through the signaling molecules of gas transmitters secreted by them, in particular, nitric oxide (NO). The aim of the work is to measure the force of interaction between single RBC and EC at different concentrations of gas transmitter NO, as well as aggregation of RBCs in whole blood in microchannels covered by endothelium cells. In the work, the ability of RBCs to aggregate in microchannels was measured using the laser aggregometry technique. The laser beam falls on a cuvette filled with whole blood, in the microchannel of which a flow is created. The intensity of backscattered light is detected. The smaller the size of the scattering particles (RBCs aggregates) and their number, the higher the detected signal. The pressure difference between the ends of the cuvette microchannel decreases monotonically over the measurement time (1-2 minutes), and at a certain point in time, a dynamic equilibrium is observed between the processes of aggregation and disaggregation of RBCs. The shear stress in the cuvette, calculated for this moment, is called the critical shear stress. This parameter characterizes the hydrodynamic strength of the RBCs aggregates. In the work, the laser tweezers were used, allowing manipulation of individual cells without mechanical contact, as well as measuring the interaction forces of RBCs and EC in vitro. ECs were obtained from the human umbilical vein (HUVEC) and grown at 37 degrees Celsius in a carbon dioxide environment on round glass slides to form a monolayer of cells. To stimulate NO production, EC were incubated with a solution of L-arginine in various concentrations of 0 - 1000 μM. We demonstrated that hydrodynamic strength of erythrocyte aggregates (CSS) in whole blood of patients with arterial hypertension and in norm measured by laser aggregometry technique is lower in case of microfluidic channels covered by endothelial cells. This demonstrates the effect of the endothelial cells on the aggregation of RBCs. Also, it was shown that incubation of endothelial cells with L-arginine leads to a decrease in the forces of RBC aggregation at L-arginine concentrations up to 100 μM and its growth with a subsequent increase in concentration. The laser tweezers and laser aggregometry technique can be used to assess the interaction of RBCs and endothelial cells, as well as the aggregation properties of RBCs in microchannels with the endothelium. The presented results are important for understanding the influence of vascular endothelium on microrheology and blood microcirculation. This research was funded by the Russian Science Foundation Grant No. 23-45-00027.