Altered fibrin clot structure and dysregulated fibrinolysis contribute to thrombosis risk in severe COVID-19

Abstract

The high incidence of thrombotic events suggests a possible role of the contact system pathway in COVID-19 pathology. In this study, we determined the altered levels of factor XII (FXII) and its activation products in critically ill patients with COVID-19 in comparison with patients with severe acute respiratory distress syndrome related to the influenza virus (acute respiratory distress syndrome [ARDS]-influenza). Compatible with those data, we found rapid consumption of FXII in COVID-19 but not in ARDS-influenza plasma. Interestingly, the lag phase in fibrin formation, triggered by the FXII activator kaolin, was not prolonged in COVID-19, as opposed to that in ARDS-influenza. Confocal and electron microscopy showed that increased FXII activation rate, in conjunction with elevated fibrinogen levels, triggered formation of fibrinolysis-resistant, compact clots with thin fibers and small pores in COVID-19. Accordingly, clot lysis was markedly impaired in COVID-19 as opposed to that in ARDS-influenza. Dysregulated fibrinolytic system, as evidenced by elevated levels of thrombin-activatable fibrinolysis inhibitor, tissue-plasminogen activator, and plasminogen activator inhibitor-1 in COVID-19 potentiated this effect. Analysis of lung tissue sections revealed widespread extra- and intravascular compact fibrin deposits in patients with COVID-19. A compact fibrin network structure and dysregulated fibrinolysis may collectively contribute to a high incidence of thrombotic events in COVID-19.

SciScore for 10.1101/2021.09.17.460777: (What is this?)

Please note, not all rigor criteria are appropriate for all manuscripts.

Table 1: Rigor

Ethics	IRB: All investigations were approved by the local ethics committees (Hanover samples: SEPSIS/ARDS Registry, ethic votum no.: 8146_BO_K_2018; Berlin samples: ethic votum no.: EA2/066/20) and written informed consent was obtained from all participants or their next-of-kin. Consent: All investigations were approved by the local ethics committees (Hanover samples: SEPSIS/ARDS Registry, ethic votum no.: 8146_BO_K_2018; Berlin samples: ethic votum no.: EA2/066/20) and written informed consent was obtained from all participants or their next-of-kin.
Sex as a biological variable	not detected.
Randomization	not detected.
Blinding	not detected.
Power Analysis	not detected.

Table 2: Resources

Antibodies
Sentences	R…

SciScore for 10.1101/2021.09.17.460777: (What is this?)

Please note, not all rigor criteria are appropriate for all manuscripts.

Table 1: Rigor

Ethics	IRB: All investigations were approved by the local ethics committees (Hanover samples: SEPSIS/ARDS Registry, ethic votum no.: 8146_BO_K_2018; Berlin samples: ethic votum no.: EA2/066/20) and written informed consent was obtained from all participants or their next-of-kin. Consent: All investigations were approved by the local ethics committees (Hanover samples: SEPSIS/ARDS Registry, ethic votum no.: 8146_BO_K_2018; Berlin samples: ethic votum no.: EA2/066/20) and written informed consent was obtained from all participants or their next-of-kin.
Sex as a biological variable	not detected.
Randomization	not detected.
Blinding	not detected.
Power Analysis	not detected.

Table 2: Resources

Antibodies
Sentences	Resources
) or rabbit-anti high molecular weight kininogen (HK; cat. no.: ab35105; Abcam, Cambridge, UK) antibody.	rabbit-anti high molecular weight kininogen suggested: None
As loading control, albumin was detected with a rabbit anti-albumin antibody (cat. no.: A001; Dako).	anti-albumin suggested: None
FXII decay in plasma: Endogenous FXII was depleted from plasma using a goat anti-FXII antibody (cat. no.: 206-0056; Zytomed Systems) covalently attached to magnetic beads (Thermo-Fisher Scientific).	anti-FXII suggested: None
Next, clots were incubated with a rabbit anti-fibrinogen/fibrin (cat. no.: A 0082; Dako) antibody overnight at 4°C.	anti-fibrinogen/fibrin suggested: None
Software and Algorithms
Sentences	Resources
Western blots were developed using a ChemiDocTM Touch (BioRad Laboratories, Inc., Hercules, CA), and densitometric analysis was conducted by the ImageLabTM, Version 6.0.1 (Bio-Rad Laboratories).	Bio-Rad Laboratories suggested: (Bio-Rad Laboratories, RRID:SCR_008426)
ImageJ was used to determine fiber density, by counting the number of fibers crossing lines of 250 µm placed in the image using the plug-in-grid.	ImageJ suggested: (ImageJ, RRID:SCR_003070)

Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

Results from LimitationRecognizer: An explicit section about the limitations of the techniques employed in this study was not found. We encourage authors to address study limitations.

Results from TrialIdentifier: No clinical trial numbers were referenced.

Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

Results from JetFighter: We did not find any issues relating to colormaps.

Results from rtransparent:

Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
No protocol registration statement was detected.

Results from scite Reference Check: We found no unreliable references.

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Altered fibrin clot structure and dysregulated fibrinolysis contribute to thrombosis risk in severe COVID-19

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