Research Interests

-Role of hemorheological factors in hemodynamics

-Importance of red blood cell factors in aggregation

-Comparative hemorheology

-Hemorheological instrumentation
 

Intracellular signaling mechanisms in the regulation of red blood cell mechanical properties

Red blood cells (RBC) have long been considered as passive transporters of respiratory gases, owing to their extremely high hemoglobin concentration. Their mechanical properties are important in fulfilling this function, however these properties were also thought to be totally resulting from the special material properties of these simple cells. New experimental evidence gathered in the last few years started to change this opinion. This project is exploring the molecular signaling pathways within RBC that take part in the active regulation of the ability of these cells to change their shape (i.e., deformability). This property is known to be the determinant of blood flow under given hemodynamic conditions.
A unique mechanical response model is being used in investigating the contribution of various intracellular signaling cascades and target proteins contributing to this regulation. The model is based on the slight but reproducible increase in RBC deformability under constant shear stress in physiological range (1-10 Pascal). The figure on the right demonstrates the increase in EI under 5 Pascal shear stress.
The experimental work includes the investigation of mechanical response under the influence of various agents interfering with the proposed signaling mechanisms (see below) and proteomic approaches to identify the target molecular structures, in order to understand the details of the regulatory mechanisms. The previous research efforts to identify the role of nitric oxide in RBC physiology and related mechanisms are also be combined with the specific aims of this project. The project will be expanded to include the regulation of RBC aggregability (e.g., by modulation of phosphatidylserine exposure on cell surface) and oxygen affinity of hemoglobin by the same signaling mechanisms.

The special way of aggregation of erythrocytes (rouleaux formation) is an important factor affecting a variety of in vivo hemodynamic processes that influence blood flow and tissue perfusion. Despite the extensive research the basic mechanisms for this physiological phenomena are still not clearly understood.
The main experimental approach is based on the models of altered erythrocyte aggregability (i.e., the cellular properties determining the degree of aggregation). The surface penetration of aggregating macromolecules (i.e., high molecular weight dextran) and adhesive forces between adjacent erythrocytes. Treatment of human erythrocytes with very low concentrations of glutaraldehyde (GA) is an example for such models (see the figure on the right).
The project aims at investigating the surface phenomena that determine the adhesive forces holding RBC together in aggregates. Sophisticated techniques such as optical tweezers, optical trapping microrheology, fluorescent/quantum dot labeling, fluorescence resonance energy transfer and atomic force microscopy are being used in the project.