Circulating Microparticles in Patients with Symptomatic Carotid Disease Are Related to Embolic Plaque Activity and Recent Cerebral Ischaemia

Abstract

Background and purpose: In order to assess the association of microparticles derived from activated platelets (PMP) or endothelial cells (EMP) with risk markers for recurrent embolic events in patients with symptomatic carotid artery disease, we studied the associations between PMP/EMP and three risk markers: plaque haemorrhage (PH), micro-embolic signals and cerebral diffusion abnormalities.

Methods: Patients with recently symptomatic high-grade carotid artery stenosis (60-99%, 42 patients, 31 men; mean age 75 ± 8 years) and 30 healthy volunteers (HV, 11 men; mean age 56 ± 12 years) were prospectively recruited. Patients were characterised by carotid magnetic resonance imaging (presence of PH [MRI PH]), brain diffusion MRI (cerebral ischaemia [DWI+]) and transcranial Doppler ultrasound (micro-embolic signals [MES+]). PMP and EMP were classified by flow cytometry and expressed as log-transformed counts per microlitre.

Results: MES+ patients (n = 18) had elevated PMP (MES+ 9.61 ± 0.57) compared to HV (8.80 ± 0.73; p < 0.0001) and to MES- patients (8.55 ± 0.85; p < 0.0001). Stroke patients had elevated PMP (9.49 ± 0.64) and EMP (6.13 ± 1.0) compared to non-stroke patients (PMP 8.81 ± 0.73, p = 0.026, EMP 5.52 ± 0.65, p = 0.011) and HV (PMP 8.80 ± 0.73, p = 0.007, and EMP 5.44 ± 0.47, p = 0.006). DWI+ patients (n = 16) showed elevated PMP (DWI+ 9.53 ± 0.64; vs. HV, p = 0.002) and EMP (DWI+ 5.91 ± 0.99 vs. HV 5.44 ± 0.47; p = 0.037). Only PMP but not EMP were higher in DWI+ versus DWI- patients (8.67 ± 0.90; p = 0.002). No association was found between PMP and EMP with MRI PH.

Conclusions: PMP and EMP were associated with stroke and recent cerebrovascular events (DWI+) but only PMP were also associated with ongoing (MES+) thrombo-embolic activity suggesting a differential biomarker potential for EMP to index cerebral ischaemia while PMP may predict on-going thrombo-embolic activity.

Keywords: Amaurosis fugax; Brain diffusion magnetic resonance imaging; Cerebral ischaemia; Endothelial microparticles; Magnetic resonance imaging of carotid plaque haemorrhage; Micro-embolic signals; Platelet microparticles; Transcranial Doppler ultrasound.

Fig. 1

The detection of platelet-derived/endothelial microparticles (PMP/EMP) by flow cytometry. Counts calculated as PMP and EMP per microlitre using flow cytometry showing population data. #Eve, number of events; %Par, percent particles. a CD31 fluorescent conjugated antibodies were used to detect all MP (P1). b CD45 fluorescent conjugated antibodies were used to exclude lymphocytes (P2). c CD42a fluorescent conjugated antibodies were used to detect PMP which were excluded from P1 and P2, and the remaining MP were measured as EMP.