BACKGROUND: The complex process by which lactation is initiated upon neonate delivery remains incompletely understood. Microvesicles (MVs) can transmit microRNAs (miRNAs) into recipient cells to influence cell function, and recent studies have identified miRNAs essential for mammary gland development and lactation. This study aimed to investigate the expression of lactation-related miRNAs in MVs isolated from human umbilical cord blood immediately after delivery.

MATERIAL AND METHODS: Umbilical cord blood samples were collected from 70 healthy pregnant women, and MVs were isolated through differential centrifugation and characterized by transmission electron microscopy, Western blotting, and nanoparticle tracking analysis. Lactation-related miRNAs were screened using bioinformatics tools for miRNA target prediction, gene ontology, and signaling pathway analyses. miRNA PCR arrays were used for miRNA expression analysis, and the results were validated by real-time PCR. Upon exposure of HBL-100 human mammary epithelial cells to MVs, MV uptake was examined by fluorescence confocal microscopy and b-casein secretion was detected by ELISA.

RESULTS: Spherical MVs extracted from umbilical cord blood expressed CD63 and had an average diameter of 167.0±77.1 nm. We profiled 337 miRNAs in human umbilical cord blood MVs and found that 85 were related to lactation by bioinformatics analysis. The 25 most differentially expressed lactation-related miRNAs were validated by real-time PCR. MV uptake by HBL-100 cells was after 4 h in culture, and significantly increased secretion of β-casein was observed after 96 h from cells exposed to MVs (P<0.05).

CONCLUSIONS: Umbilical cord blood MVs contain many lactation-related miRNAs and can induce β-casein production by HBL-100 cells in vitro. Thus, umbilical cord blood MVs may mediate secretion of β-casein through miRNAs, thereby playing an important role in fetal-maternal crosstalk.

Keywords: Microvesicles, Lactation