Circulating extracellular vesicles as a noninvasive biomarker of rejection in heart transplant

ABSTRACT Aims : Circulating extracellular vesicles (EV) are raising considerable interest as a non-invasive diagnostic tool as they are easily detectable in biological fluids and contain specific set of nucleic acids, proteins, and lipids reflecting pathophysiological conditions. We aimed to investigate differences in plasma-derived EV surface-protein profile as biomarker to be used in combination with endomyocardial biopsies (EMB) for the diagnosis of allograft rejection. Methods and results : Plasma was collected from 90 patients (53 training cohort, 37 validation cohort) prior to EMB. EV concentration was assessed by nanoparticle tracking analysis. EV surface antigens were measured using a multiplex flow cytometry assay comprising 37 fluorescently labelled capture bead populations coated with specific antibodies directed against respective EV surface epitopes. The concentration of EV was significantly increased and their diameter decreased in patients undergoing rejection as compared to negative ones. The trend was highly significant for both antibody-mediated rejection (AMR), and acute cellular rejection (P Conclusions : Circulating EV are highly promising as new tool to characterize cardiac allograft rejection and to be complementary to EMB monitoring. Narrative Abstract : Our study describes a method for detecting and characterising circulating extracellular vesicles (EV) as a minimally invasive, liquid biopsy for the diagnosis of cardiac allograft rejection, and as a complementary tool to EMB monitoring. EV obtained from peripheral blood were profiled to identify rejection and its types in cardiac transplant recipients. A standardized and rapid tool was established using a fluorescent bead-based multiplex assay. We built a diagnostic model based on machine learning algorithms to identify non-rejecting patients who potentially do not require EMBs. EV profiling could represent a tool for non-invasive monitoring of allograft rejection in cardiac transplant recipients.