Rahmi Oklu MD, PhD, Presenter: Nothing to Disclose

Hassan Albadawi MD, Abstract Co-Author: Nothing to Disclose

Stephan Wicky MD, Abstract Co-Author: Royalties, Amirsys, Inc

Martin H. Sillesen MD, PhD, Abstract Co-Author: Nothing to Disclose

Michael T. Watkins, Abstract Co-Author: Nothing to Disclose

The purpose of this study was to demonstrate the presence of neutrophil extracellular traps (NETs) in human thrombi ex vivo, assess the effect of nuclease treatment on clot morphology and determine whether lipopolysaccharide (LPS), histone-3 and histone-4 (known inducers of NETS) could modulate the mechanical strength of thrombi.

Immunohistochemistry for NETs was performed on ex vivo sections from 5 acute and 5 chronic thrombus samples using an antibody specific for histone-DNA complex (H2A/H2B/DNA). The thrombi sections were further evaluated by immunostaining for fibrinogen, von Willebrand factor, neutrophils and monocytes. To evaluate degradation of NETs within the extracellular matrix of human thrombi, 10 units of deoxyribonuclease I enzyme (DNase I) was incubated with each sample. To assess a role for NETs in providing tensile strength to an acute thrombus, human blood samples were treated either with LPS, histone-3 or histone-4; the mechanical strength in treated and untreated blood was compared using thromboelastography.

Extensive levels of NETs were identified in the extracellular matrix of human thrombi ex vivo. Detection of NETs correlated with positive immunostaining for neutrophils and monocytes. NETs were detected uniformly throughout the acute thrombi; in contrast, NETs were present only in regions of high cell density near the lumen in chronic thrombi. Acute thrombi contained minimal collagen, however, chronic thrombi were comprised of significant levels of collagen, consistent with prior reports. NETS were successfully degraded from acute human thrombi ex vivo following treatment with DNase I. Producers of NETs, i.e. LPS, H3 and H4, created a substantially stronger clot as compared to control untreated human samples.

NETs are important components of the human thrombus, which may play a role in enhancing the tensile strength of thrombi. These ex vivo studies indicate that DNase treatment can modulate thrombolysis in human thrombi.

A novel DNA matrix in the human thrombus may lead to new therapies to enhance thrombolysis and new anticoagulation strategies.

Oklu, R, Albadawi, H, Wicky, S, Sillesen, M, Watkins, M, Extracellular Genomic DNA in Human Thrombus: Implications for the Use of Deoxyribonuclease Enzymes in Thrombolysis.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12033555.html