Absences of Endothelial Microvesicle Changes in the Presence of the Endotheliopathy of Trauma

TRAUMA-DERIVED EXTRACELLULAR VESICLES ARE SUFFICIENT TO INDUCE ENDOTHELIAL DYSFUNCTION AND COAGULOPATHY

ABSTRACTINTRODUCTION

Although a number of studies have demonstrated increased release of extracellular vesicles (EVs) and changes in their origin differentials after trauma, the biologic significance of EVs is not well understood. We hypothesized that EVs released after trauma/hemorrhagic shock (HS) contribute to endotheliopathy and coagulopathy. To test this hypothesis, adoptive transfer experiments were performed to determine whether EVs derived from severely injured patients in shock were sufficient to induce endothelial dysfunction and coagulopathy. Methods: Total EVs were enriched from plasma of severely injured trauma/HS patients or minimally injured patients by ultracentrifugation and characterized for size and numbers. Under isoflurane anesthesia, noninjured naive C57BL/6J mice were administered EVs at varying concentrations and compared with mice receiving equal volume vehicle (phosphate-buffered saline (PBS)) or to mice receiving EVs from minimally injured patients. Thirty minutes after injection, mice were sacrificed, and blood was collected for thrombin generation (thrombin-antithrombin, thrombin-antithrombin complex [TAT] assay) and syndecan-1 by enzyme-linked immunoabsorbent assay (ELISA). Lungs were harvested for examination of histopathologic injury and costained with von Willebrand factor and fibrin to identify intravascular coagulation. Bronchial alveolar lavage fluid was aspirated from lungs for protein measurement as an indicator of the endothelial permeability. Data are presented as mean ± SD, P < 0.05 was considered significant, and t test was used. Results: An initial proof-of-concept experiment was performed in naive mice receiving EVs purified from severely injured trauma/HS patients (Injury Severity Score [ISS], 34 ± 7) at different concentrations (5 × 106 to 3.1 × 109/100 μL/mouse) and compared with PBS (control) mice. Neither TAT nor syndecan-1 levels were significantly different between groups at 30 minutes after EV infusion. However, lung vascular permeability and histopathologic injury were significantly higher in the EV group, and lung tissues demonstrated intravascular fibrin deposition. Based on these data, EVs from severely injured trauma/HS patients (ISS, 32 ± 6) or EVs from minimally injured patients (ISS, 8 ± 3) were administered to naive mice at higher concentrations (1 × 109 to 1 × 1010 EV/100 μL/mouse). Compared with mice receiving EVs from minimally injured patients, plasma TAT and syndecan-1 levels were significantly higher in the trauma/HS EV group. Similarly, bronchial alveolar lavage protein and lung histopathologic injury were higher in the trauma/HS EV group, and lung tissues demonstrated enhanced intravascular fibrin deposition. Conclusion: These data demonstrate that trauma/HS results in the systemic release of EVs, which are capable of inducing endotheliopathy as demonstrated by elevated syndecan-1 and increased permeability and coagulopathy as demonstrated by increased TAT and intravascular fibrin deposition. Targeting trauma-induced EVs may represent a novel therapeutic strategy.

Exploratory Investigation of the Plasma Proteome Associated with the Endotheliopathy of Trauma

BACKGROUND

The endotheliopathy of trauma (EoT) is associated with increased mortality following injury. Herein, we describe the plasma proteome related to EoT in order to provide insight into the role of the endothelium within the systemic response to trauma.

METHODS

99 subjects requiring the highest level of trauma activation were included in the study. Enzyme-linked immunosorbent assays of endothelial and catecholamine biomarkers were performed on admission plasma samples, as well as untargeted proteome quantification utilizing high-performance liquid chromatography and tandem mass spectrometry.

RESULTS

Plasma endothelial and catecholamine biomarker abundance was elevated in EoT. Patients with EoT (n = 62) had an increased incidence of death within 24 h at 21% compared to 3% for non-EoT (n = 37). Proteomic analysis revealed that 52 out of 290 proteins were differentially expressed between the EoT and non-EoT groups. These proteins are involved in endothelial activation, coagulation, inflammation, and oxidative stress, and include known damage-associated molecular patterns (DAMPs) and intracellular proteins specific to several organs.

CONCLUSIONS

We report a proteomic profile of EoT suggestive of a surge of DAMPs and inflammation driving nonspecific activation of the endothelial, coagulation, and complement systems with subsequent end-organ damage and poor clinical outcome. These findings support the utility of EoT as an index of cellular injury and delineate protein candidates for therapeutic intervention.

Human glycocalyx shedding: Systematic review and critical appraisal

BACKGROUND

The number of studies measuring breakdown products of the glycocalyx in plasma has increased rapidly during the past decade. The purpose of the present systematic review was to assess the current knowledge concerning the association between plasma concentrations of glycocalyx components and structural assessment of the endothelium.

METHODS

We performed a literature review of Pubmed to determine which glycocalyx components change in a wide variety of human diseases and conditions. We also searched for evidence of a relationship between plasma concentrations and the thickness of the endothelial glycocalyx layer as obtained by imaging methods.

RESULTS

Out of 3,454 publications, we identified 228 that met our inclusion criteria. The vast majority demonstrate an increase in plasma glycocalyx products. Sepsis and trauma are most frequently studied, and comprise approximately 40 publications. They usually report 3-4-foldt increased levels of glycocalyx degradation products, most commonly of syndecan-1. Surgery shows a variable picture. Cardiac surgery and transplantations are most likely to involve elevations of glycocalyx degradation products. Structural assessment using imaging methods show thinning of the endothelial glycocalyx layer in cardiovascular conditions and during major surgery, but thinning does not always correlate with the plasma concentrations of glycocalyx products. The few structural assessments performed do not currently support that capillary permeability is increased when the plasma levels of glycocalyx fragments in plasma are increased.

CONCLUSIONS

Shedding of glycocalyx components is a ubiquitous process that occurs during both acute and chronic inflammation with no sensitivity or specificity for a specific disease or condition.

A conceptual time window-based model for the early stratification of trauma patients

Progress in the testing of therapies targeting the immune response following trauma, a leading cause of morbidity and mortality worldwide, has been slow. We propose that the design of interventional trials in trauma would benefit from a scheme or platform that could support the identification and implementation of prognostic strategies for patient stratification. Here, we propose a stratification scheme based on defined time periods or windows following the traumatic event. This 'time-window' model allows for the incorporation of prognostic variables ranging from circulating biomarkers and clinical data to patient-specific information such as gene variants to predict adverse short- or long-term outcomes. A number of circulating biomarkers, including cell injury markers and damage-associated molecular patterns (DAMPs), and inflammatory mediators have been shown to correlate with adverse outcomes after trauma. Likewise, several single nucleotide polymorphisms (SNPs) associate with complications or death in trauma patients. This review summarizes the status of our understanding of the prognostic value of these classes of variables in predicting outcomes in trauma patients. Strategies for the incorporation of these prognostic variables into schemes designed to stratify trauma patients, such as our time-window model, are also discussed.