Gestational age at birth influences protein and RNA content in human milk extracellular vesicles

Abstract

Human milk extracellular vesicles (HM EVs) are proposed to protect against disease development in infants. This protection could in part be facilitated by the bioactive EV cargo of proteins and RNA. Notably, mothers birth infants of different gestational ages with unique needs, wherein the EV cargo of HM may diverge. We collected HM from lactating mothers within two weeks of a term or preterm birth. Following purification of EVs, proteins and mRNA were extracted for proteomics and sequencing analyses, respectively. Over 2000 protein groups were identified, and over 8000 genes were quantified. The total number of proteins and mRNA did not differ significantly between the two conditions, while functional bioinformatics of differentially expressed cargo indicated enrichment in immunoregulatory cargo for preterm HM EVs. In term HM EVs, significantly upregulated cargo was enriched in metabolism‐related functions. Based on gene expression signatures from HM‐contained single cell sequencing data, we proposed that a larger portion of preterm HM EVs are secreted by immune cells, whereas term HM EVs contain more signatures of lactocyte epithelial cells. Proposed differences in EV cargo could indicate variation in mother's milk based on infants’ gestational age and provide basis for further functional characterisation.

Extracellular Vesicles: A Crucial Player in the Intestinal Microenvironment and Beyond

“…Recent studies have shown that there is no significant difference in the proteins and mRNA contained in EVs in the breast milk of premature and full-term infants, but the immunomodulatory substances carried by EVs are significantly different. It is speculated that premature milk EVs are secreted by immune cells, while those of full-term infants of breast milk EVs are more likely to come from mammary epithelial cells [ 59 ]. However, it is widely believed that breast milk harbors a diverse and abundant microbial community originating from the surface skin, infant oral contamination, and the gut-breast axis, inferring that milk EVs could also contain a certain number of microbiota-derived EVs, which are involved in neonatal intestinal immune formation and colonization of gut microbiota, and serve as receptors for bioactive molecules in host cells [ 60 ].…”