Microparticles profiling in trauma patients: high level of microparticles induce activation of platelets in vitro

Trauma-induced coagulopathy (TIC) is recognised as an own clinical entity which includes all components of haemostasis following rapidly tissue injury, hypoperfusion and shock. Microparticles (MP) are known to be released in large quantities from different cell types after trauma. The present study aimed to perform a phenotypic MP profiling after major trauma and to elucidate potential procoagulative function of MP under simulated conditions of lethal triad.

For MP isolation, 20 trauma patients (median ISS 24) were included. To produce a Standard MP Phenotype Profile after trauma, samples were pooled, extracted and concentrated by using an ultracentrifuge protocol. Specific cell surface markers were measured by flow cytometry. Our Standard MP Phenotype Profile was subsequently added in high and low concentration to an in vitro lethal triad assay, simulating coagulopathy via induced hypothermia, dilution and acidosis. A comprehensive analysis of coagulation function was performed.

Within our Standard MP Phenotype Profile, PDMP (56%) were found as predominant phenotype followed by EDMP (33%) and MDMP (11%). EDMP characterized by CD144, CD62E and Annexin were determined most frequently but also EDMP expressing CD62P. In addition, tissue factor (TF) was expressed on all MP entities (EDMP 63%, PDMP 30%, MDMP 7%). Within our lethal triad simulation assay, the addition of low and high concentrated MP did not cause any significant alteration in standard coagulation assays, coagulation initiation, clot kinetics or stability. Addition of high concentrated MP increased platelet function and P-selectin expression significantly.

Our data confirm the assumption that there is a characteristic MP phenotype pattern in trauma, which may alter haemostatic capacity at least in part mediated via augmenting in primary haemostasis resulting in an improved contribution of platelets to clot formation. There are indications that expression of selectins on MP surface is involved in this activation process, but this pathway needs to be investigated in more detail.