Different Circulating Endothelial Microvesicle Subtype Signature in Subacute and Chronic Spinal Cord Injury

The aim of this study was to determine whether circulating concentrations of activation- and apoptosis-derived endothelial cell-derived microvesicles (EMVs) differ between adults after subacute (time since injury ≤6 months) and chronic (time since injury >12 months) spinal cord injury (SCI).

Peripheral blood was collected from 43 adults (age range 18-71 years): 12 non-injured adults (9 male/3 female), 16 adults with subacute cervical and high thoracic (C2-T3) motor complete injuries (13 male/3 female; time since injury 1-3 months), and 15 adults with chronic cervical and high thoracic (C1-T2) motor complete injuries (14 male/1 female; time since injury 12-52 months). EMVs were defined by markers of endothelial origin either by activation (CD62e⁺) or apoptosis (CD31⁺/CD42b^-) by flow cytometry. Activation-derived but not apoptosis-derived EMVs were significantly higher (P < .05) in adults with chronic SCI (median [IQR], 139 [83-181] EMVs/μL) compared with adults with subacute SCI (median [IQR], 99 [83-104] EMVs/μL) and non-injured adults (median [IQR], 74 [51-104] EMVs/μL). In contrast, apoptosis-derived but not activation-derived EMVs were significantly higher (P < .05) in adults with subacute SCI (mean ± SD, 77 ± 17 EMVs/μL) compared with adults with chronic SCI (mean ± SD, 55 ± 19 EMVs/μL) and non-injured adults (mean ± SD, 52 ± 25 EMVs/μL). Differential expression of circulating EMVs in adults with SCI during the subacute and chronic phase of injury may represent a biomarker of the vascular environment associated with each condition. Our findings suggest that the vascular phenotype is markedly different in subacute compared with the chronic SCI and provide insight into endothelial function after SCI.