82 - Oral Communication
Feb. 26, 2021, 1:45 p.m. - 3:15 p.m., Rome


Platelet activation and apoptosis in COVID-19 infection: data from an observational study
K. Althaus, I. Marini, J. Zlamal, L. Pelzl, H. Häberle, M. Mehrländer, S. Hammer, M. Bitzer, N. Malek, D. Rath, H. Bösmüller, M. Gawaz, P. Rosenberger, T. Bakchoul, Presenter: K. Althaus (Tübingen)

Background and Objective
Accumulating evidence indicates an association between SARS-CoV2 pneumonia (COVID-19) and thromboembolic complications. The pathophysiology of the COVID-19 associated-thromboembolic events seem to be complex and multifactorial, involving interplay between cellular and plasmatic elements of the hemostatic system. In this study, we hypothesized that thrombus formation in COVID-19 is accompanied by platelet activation and apoptosis with subsequent alteration of the coagulation system.
21 COVID-19 positive patients who were admitted to the intensive care unit (ICU) were included. Blood samples were analyzed for platelet activation and apoptosis markers, respectively. Flow cytometer (FC) was used to investigate expression of P-selectin, activated glycoprotein (GP) IIb/IIIa, depolarization of mitochondrial inner transmembrane potential (ΔΨm), intracellular calcium (Ca2+) concentration and phosphatidylserine (PS) externalization.
Platelets from COVID-19 positive ICU patients (n=21) showed significantly higher expression of P-selectin (2.27±0.45 vs. 1.27±0.55, p= 0.0279) compared to healthy donors. In addition, higher ΔΨm depolarization (1.39±0.07 vs. 0.99±0.06, p=0.0005), Ca2+ concentration (2.73±0.31 vs. 1.00±0.05, p<0.0001) and PS externalization (2.05±0.48 vs. 0.86±0.11, p=0.0236) were observed. Most importantly, PS exposure was associated with the SOFA score (sequential organ failure assessment, r=0.5635, p=0.0078) and plasma levels of D-Dimer (r=0.4473, p=0.0420). Finally, patients with thromboembolic events had higher PS externalization compared to those with no thrombosis (2.85±0.75 vs. 0.99±0.20, p=0.0340).
Our study shows that COVID-19 positive ICU patients had increased platelet activation and signs of apoptosis. The strong correlations between platelet apoptosis and D-Dimer as well as the incidence of thromboembolic complications may indicate that platelet apoptosis potentially contributes to sustained increased thromboembolic risk in COVID-19 positive ICU patients.
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