Spherization of red blood cells and platelets margination in COPD patients

Abstract

Rationale: There are important interactions between Red Blood Cells (RBCs) and platelets in the bloodstream. These interactions lead to a phenomenon called margination. RBCs in pathological situations undergo biochemical and conformational changes leading to alterations in blood rheology. Aim: RBCs shape in volunteers (21), stable (42) and exacerbated (31) COPD patients was analyzed. We studied the effect of the RBCs spherization on the platelets transport experimentally, in vitro, and by using numerical simulations. Methods: RBC shape was estimated by the second moment of Pearson obtained through flow cytometry on fsc histogram. In vitro experiments were performed to analyze the effect of RBC shape on platelets adhesion/aggregation in dynamic conditions. Neuraminidase treatment was used to induce RBCs spherization. Numerical simulation were performed to determine the effect of RBCs spherization on platelets mean square displacement (MSD) to provide a physical explanation. Results: Significant increase of RBC sphericity was observed in COPD patients compared to volunteers (Kruskal-Wallis: p<0.0001). In vitro experiments, at shear rate of 100 s-1, we observed that RBCs treated with neuraminidase mainly affect the number of platelet aggregates (p = 0.004). There was no change in the aggregates size. At a shear rate of 400 sec-1 neuraminidase treatment changes both the size of the aggregates (p = 0.009) and the number of platelet aggregates (p = 0.008). Numerical simulations indicated that RBCs spherization induces an increase of MSD and the effect was more pronounced when the shear rate increased. Conclusion: Our results show that the RBCs of COPD patients are more spherical than those of healthy volunteers. Experimentally we observe that the RBCs spherization induces an increase platelet transport to the wall. Additional studies are needed to better understand the possible association between the RBCs effect on the platelets transport and the increased cardiovascular events observed in COPD patients.

Anomalous Platelet Transport & Fat-Tailed Distributions

“…As for the RBCs, the normal biconcave shape is used in the majority of the experiments, while in few of them we introduced spherised RBCs emulating pathological conditions [28], e.g. diabetes, chronic obstructive pulmonary disease.…”