From the Journals

NETs a possible therapeutic target for COVID-19 thrombosis?


Researchers in Madrid may have found a clue to the pathogenesis of ST-segment elevation myocardial infarction (STEMI) in patients with COVID-19; it might also offer a therapeutic target to counter the hypercoagulability seen with COVID-19.

In a case series of five patients with COVID-19 who had an STEMI, neutrophil extracellular traps (NETs) were detected in coronary thrombi of all five patients. The median density was 66%, which is significantly higher than that seen in a historical series of patients with STEMI. In that series, NETs were found in only two-thirds of patients; in that series, the median density was 19%.

In the patients with COVID-19 and STEMI and in the patients reported in the prepandemic historical series from 2015, intracoronary aspirates were obtained during percutaneous coronary intervention using a thrombus aspiration device.

Histologically, findings in the patients from 2015 differed from those of patients with COVID-19. In the patients with COVID, thrombi were composed mostly of fibrin and polymorphonuclear cells. None showed fragments of atherosclerotic plaque or iron deposits indicative of previous episodes of plaque rupture. In contrast, 65% of thrombi from the 2015 series contained plaque fragments.

Ana Blasco, MD, PhD, Hospital Universitario Puerta de Hierro-Majadahonda, Madrid, and colleagues report their findings in an article published online Dec. 29 in JAMA Cardiology.

Commenting on the findings in an interview, Irene Lang, MD, from the Medical University of Vienna said, “This is really a very small series, purely observational, and suffering from the problem that acute STEMI is uncommon in COVID-19, but it does serve to demonstrate once more the abundance of NETs in acute myocardial infarction.”

“NETs are very much at the cutting edge of thrombosis research, and NET formation provides yet another link between inflammation and clot formation,” added Peter Libby, MD, from Harvard Medical School and Brigham and Women’s Hospital, Boston.

“Multiple observations have shown thrombosis of arteries large and small, microvessels, and veins in COVID-19. The observations of Blasco et al. add to the growing literature about NETs as contributors to the havoc wrought in multiple organs in advanced COVID-19,” he added in an email exchange with this news organization.

Neither Dr. Lang nor Dr. Libby were involved in this research; both have been actively studying NETs and their contribution to cardiothrombotic disease in recent years.

NETs are newly recognized contributors to venous and arterial thrombosis. These weblike DNA strands are extruded by activated or dying neutrophils and have protein mediators that ensnare pathogens while minimizing damage to the host cell.

First described in 2004, exaggerated NET formation has also been linked to the initiation and accretion of inflammation and thrombosis.

“NETs thus furnish a previously unsuspected link between inflammation, innate immunity, thrombosis, oxidative stress, and cardiovascular diseases,” Dr. Libby and his coauthors wrote in an article on the topic published in Circulation Research earlier this year.

Limiting NET formation or “dissolving” existing NETs could provide a therapeutic avenue not just for patients with COVID-19 but for all patients with thrombotic disease.

“The concept of NETs as a therapeutic target is appealing, in and out of COVID times,” said Dr. Lang.

“I personally believe that the work helps to raise awareness for the potential use of deoxyribonuclease (DNase), an enzyme that acts to clear NETs by dissolving the DNA strands, in the acute treatment of STEMI. Rapid injection of engineered recombinant DNases could potentially wipe away coronary obstructions, ideally before they may cause damage to the myocardium,” she added.

Dr. Blasco and colleagues and Dr. Lang have disclosed no relevant financial relationships. Dr. Libby is an unpaid consultant or member of the advisory board for a number of companies.

A version of this article first appeared on

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