Chronological changes of serum exosome in preterm infants: A prospective study.

BACKGROUND Exosomes, which are observed in all human fluid, including serum, are nanosized extracellular vesicles with a mechanism of intercellular communication. Potential clinical applications of exosomes involving neonatal diseases have recently been discussed. However, the state of exosomes in serum during early infancy is unclear. METHODS We evaluated the chronological changes in the concentration of serum-derived exosomes in preterm infants after birth. In this prospective study, we measured the concentration of serum-derived exosomes of 20 infants for 12 months after birth. RESULTS The average concentration of serum-derived exosomes was 4.6×1010 particles/ml at birth and increased significantly until 48 weeks old. There was a moderate correlation between the gestational age and the concentration of serum-derived exosomes both at birth (r=0.54, p=0.01), and during 8 weeks after birth (r=0.48, p<0.001). A multivariable analysis showed that the gestational age at birth was associated with the concentration of serum-derived exosomes at birth (partial regression coefficient, 0.86; 95% CI, 0.37-1.37; p=0.002). CONCLUSIONS The concentration of serum-derived exosomes in preterm infants increased both chronologically and gestational age-dependently after births. These basic data may help for further understanding of exosomes' physiology of preterm infants.