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INTRODUCTIONExtracellular vesicle signalling has been recognised to play a key role in cellularinteraction both in neurogenesis and neuroregeneration. Exosomes are releasedvia the endosomal pathway from a variety of cells contributing to intercellularcommunication and are crucial for maintaining neuronal integrity.METHODSCerebrospinal fluid (CSF) was taken from infants with evolving post-haemorrhagic hydrocephalus (Ethics:NHS-REC:15-YH-0251). Concentration ofEVs was determined using a NanoSight NS300 NTA. EVs were isolated usingdifferential ultracentrifugation, and characterised using transmission electronmicroscopy (TEM) and gold immunolabelling. Candidate microRNA expressionwere analysed from lysed EVs (miR-9,-17,-26a,-124,-1911).RESULTSNTA analysis (n=11) from 3 infants, 26-42 weeks corrected gestational age,consistently demonstrated particles in the exosomal fraction (30-100nm)(1.48–1.59x10^10particles/mL; Figure 1A). The size of these particles increasedwith age (R^2=0.74, p=0.027) while particle concentration declined over timefollowing haemorrhage.
TEM demonstrated multiple spheroids with lipid bilayers meeting the size andexpected morphology of exosomes (Figure 1B). Immunogold stainingdemonstrated these EVs express exosomal markers (CD63 and CD81).microRNAs were successfully detected by qPCR in all samples. Relativeconcentration of serum-exosome miRNA reduced with time followinghaemorrhage. Brain and CSF-exosome miRNAs could be detected in all samplessuggesting the central nervous system as the origin of these EVs.CONCLUSIONSThis is the first reported characterisation of exosomes from the CSF of preterminfants. Our results describe a time course of microRNA expression and supportthe hypothesis that exosome signalling is involved in early brain development.Such exosomes may represent ideal sources of biomarkers for injury andneurodevelopment.