Circulating Biomarkers of COVID-19-Triggered Endotheliopathy: From Conjecture to Certainty

Background: Clinical and analytical data on patients suffering from coronavirus disease-2019 (COVID-19) indicate that endothelial damage plays a key role in the pathophysiology of the disease and is responsible for the pulmonary complications and the thrombotic microangiopathy affecting multiple organs, which contribute directly to mortality (Ackerman et al. N Engl J Med 2020). Detection of biomarkers of endothelial injury in circulating blood may provide critical diagnostic and prognostic information on the disease course (Goshua et al. Lancet Haematology 2020). Endothelial injury is also a cornerstone of pathobiology in other septic and potentially life-threatening inflammatory syndromes. Objectives: To identify circulating markers of endothelial damage in COVID-19 patients, and compare their levels with those observed in other septic syndromes. Methods: Plasma samples from non-critically ill patients with confirmed COVID-19 pneumonia (positive nasopharyngeal swab and confirmatory radiological chest imaging) requiring admission (n=42) were collected during the first 36h of hospitalization. Endothelial damage was evaluated by measuring in plasma: i) markers of endothelial function and activation (sVCAM-1, VWF, ADAMTS-13 activity, Protein C and α2-antiplasmin as a marker of fibrinolysis); ii) heparan sulfate (HS) levels, as indicators of endothelial glycocalyx degradation and loss of endothelial barrier function; and iii) C5b9 deposits on endothelial cells in culture, and soluble C5b9 (sC5b9) levels, to measure complement activation. Circulating dsDNA was analyzed as an indicator of the presence of neutrophil extracellular traps (NETs). ELISA tests were used for sVCAM-1, Protein C, HS, and sC5b9 levels. ADAMTS-13 activity was evaluated by FRETS. VWF, Protein C, and α2-antiplasmin were measured at the Atellica COAG 360 (Siemens Healthineers). C5b9 deposits were assessed by immunofluorescence and dsDNA levels by Quant-iT PicoGreen assay kit. Results were compared with those obtained in healthy donors (controls, n=45), and patients with non-infectious systemic inflammatory response syndrome (NI-SIRS, n=8) and septic shock (SS, n=8). Results: Levels of sVCAM-1 were significantly higher in COVID-19 patients vs. controls, NI-SIRS and SS (159±12 vs. 79±4, 57±8 and 80±10 ng/mL, respectively, p Conclusions: Our data clearly demonstrate the presence of endothelial stress products in the circulating blood of non-critically ill COVID-19 patients. These biomarkers of endothelial injury are suggestive indicators of different aspects of the disease: specifically, release of acute phase reactants, degradation of the endothelial cell glycocalyx, and activation of the complement system. Furthermore, this profile of biomarkers in COVID-19 appears specific, with a differential behavior in comparison with septic shock, in which endothelial damage is also known to be critical. Additional studies are needed to validate these biomarkers as diagnostic and prognostic tools of the endothelial complications in COVID-19 patients, both in early disease and later, as well as supporting specific forms of therapeutic intervention. Download : Download high-res image (164KB) Download : Download full-size image Figure . Disclosures Carreras: Jazz Pharmaceuticals: Research Funding, Speakers Bureau; German Jose´ Carreras Leukaemia Foundation: Research Funding. Carlo-Stella: Boehringer Ingelheim and Sanofi: Consultancy; ADC Therapeutics and Rhizen Pharmaceuticals: Research Funding; Bristol-Myers Squibb, Merck Sharp & Dohme, Janssen Oncology, AstraZeneca: Honoraria; Servier, Novartis, Genenta Science srl, ADC Therapeutics, F. Hoffmann-La Roche, Karyopharm, Jazz Pharmaceuticals: Membership on an entity’s Board of Directors or advisory committees. Moraleda: Sandoz: Consultancy, Other: Travel Expenses; Novartis: Consultancy, Other: Travel Expenses; Gilead: Consultancy, Other: Travel Expenses; Jazz Pharmaceuticals: Consultancy, Research Funding; Takeda: Consultancy, Other: Travel Expenses. Richardson: Celgene/BMS, Oncopeptides, Takeda, Karyopharm: Research Funding. Diaz-Ricart: German Jose Carreras Leukaemia Foundation: Research Funding; Jazz Pharmaceuticals: Honoraria, Research Funding.