Lactation-Related microRNA Expression Profiles of Porcine Breast Milk Exosomes

Breast milk is the primary source of nutrition for newborns, and rich in immunological components. microRNAs (miRNAs), a well-defined group of non-coding small RNAs, are present in various body fluids (such as breast milk), which are selectively packaged inside the exosomes, a type of membrane vesicles, secreted by most cell types. These exosomal miRNAs could be actively delivered into recipient cells, and regulate target gene expression and recipient cell function. We present the lactation-related miRNA expression profiles in porcine milk exosomes across entire lactation period in pig industry (newborn to 28 days after birth) using deep sequencing technology. We found that the immune-related miRNAs are presented and enriched in breast milk exosomes, and generally resistant to relatively harsh conditions. Notably, these exosomal miRNAs exhibited the higher abundances in the colostrum (newborn to 3 days after birth) than that in the mature milk (7 to 28 days after birth), as well as in the serum of colostrum-feeding piglets compared with the only mature milk-feeding piglets. These immune-related miRNAs-loaded exosomes in breast milk may be transferred into the infant body via the digestive tract. These observations are prelude to the in-depth investigations of the essential roles of the breast milk in the development of the infant's immune system. Overall design: Eight small RNA libraries in porcine breast milk exosomes of six lactigenous stages (0, 3, 7, 14, 21 and 28 days after birth) from three female pigs were sequenced.