Extracellular vesicles characterization in patients with hypertrophic cardiomyopathy

Background: Hypertrophic cardiomyopathy (HCM) is diagnosed according to the presence of morphological and functional traits of the heart, often in the presence of genetic mutations. A specific biomarker assessing the aetiopathology of this condition is lacking. Extracellular vesicles (EVs), small particles released by all cells into biological fluids, hold promise as diagnostic and prognostic tools for cardiac diseases. We aim at characterising plasma-derived EVs isolated from 18 consecutive HCM patients and 13 healthy volunteers (CTR). Methods: HCM underwent echocardiographic assessment and genetic testing evaluating 200 genes (NGS). EVs were isolated via ultracentrifugation from platelet-free plasma. Quantitative and qualitative assessments of EVs were performed by nanoparticle tracking analysis and transmission electron microscopy. FACS analysis was used to characterize EV subpopulations. Data are expressed as median and interquartile ranges. Results: Most patients were male (70.8% HCM and 54% CTR) with a median age of 61 (52.5-71) years (HCM) and 47 (44-52) (CTR). Missense mutations in the MYH7 gene were the most found in HCM. The median maximum wall thickness in HCM was 16 mm (15-19) vs 8 mm (7-9) in CTR. No differences were found in EV concentrations between HCM and CTR, respectively, 3.6*109 EV/ml/cell count (2*109-5*109) and 5*10⁹ EV/ml/cell count (4*109-6*109). However, EV concentration was positively associated with the sudden cardiac death risk score in HCM (r= 0.63). Among the EVs positive for CFSE (a specific dye for EVs), those released from platelets, progenitor endothelial cells and neutrophils were increased in HCM patients vs CTR, respectively, by 1.7-, 1.5- and 1.1-fold. A strong negative association (r= -0.74) was found between progenitor endothelial cell-derived EVs and the E/E’ ratio of diastolic function, a strong predictor of first cardiac events. Conclusions: HCM patients present a peculiar phenotypic pattern of EVs that associates which diastolic function and sudden cardiac death.