Using AFM to study erythrocytes’ biophysical properties on Stroke and Amyotrophic Lateral Sclerosis

Stroke is the most common cause of death worldwide. It is associated with high fibrinogen levels in plasma. Fibrinogen promotes clot formation, which in some situations can promote venous thromboembolism. Amyotrophic Lateral Sclerosis (ALS) is a devastating and fatal neurodegenerative disease, leading to severe respiratory insufficiency and hypoxia. The main goals of this study were: (i) to study the influence of fibrinogen on erythrocytes adhesion in stroke patients; and, (ii) to evaluate morphological and elasticity changes on erythrocytes from ALS patients. Human blood samples from stroke and ALS patients were analysed and compared with healthy donors (control). Samples were analysed by Atomic Force Microscopy (AFM) and through haemorheological parameters. AFM was used to measure fibrinogen-erythrocyte and erythrocyte-erythrocyte interactions, as well as erythrocyte stiffness and morphology. Erythrocyte membrane fluidity and zeta-potential were also assessed on ALS. Erythrocytes from stroke patients are less deformable and have more propensity to aggregate. Fibrinogen-erythrocytes interactions on stroke are stronger than for the control group. They also have an increased concentration of ´ fibrinogen variant. These changes could be associated with high risk of cardiovascular events and a worst prognostic of the disease. Erythrocytes from ALS patients are more capable to deform and present morphological changes. Changes in erythrocytes physical-chemical and electrical properties and on their membrane organization were also observed. These findings could help to consider the fibrinogen-erythrocyte binding as a new cardiovascular risk factor for stroke disease. Understanding the role of fibrinogen on erythrocyte aggregation may be relevant for potential future drug interventions to reduce aggregation and enhance microcirculatory flow conditions. Fibrinogen in ALS disease could promote venous thrombotic events. In the future, finding a molecular biomarker of early respiratory dysfunction in ALS disease that could comprise prognostic value will be essential