title: Lactogenic hormones alter cellular and extracellular microRNA expression in bovine mammary epithelial cell culture.
abstract: BACKGROUND
  Bovine milk contains not only a variety of nutritional ingredients but also microRNAs (miRNAs) that are thought to be secreted by the bovine mammary epithelial cells (BMECs). The objective of this study was to elucidate the production of milk-related miRNAs in BMECs under the influence of lactogenic hormones.
  
  
  RESULTS
  According to a microarray result of milk exosomal miRNAs prior to cellular analyses, a total of 257 miRNAs were detected in a Holstein cow milk. Of these, 18 major miRNAs of interest in the milk were selected for an expression analysis in BMEC culture that was treated with or without dexamethasone, insulin, and prolactin (DIP) to induce a lactogenic differentiation. Quantitative polymerase chain reaction (qPCR) results showed that the expressions of miR-21-5p (P = 0.005), miR-26a (P = 0.016), and miR-320a (P = 0.011) were lower in the DIP-treated cells than in the untreated cells. In contrast, the expression of miR-339a (P = 0.017) in the cell culture medium were lower in the DIP-treated culture than in the untreated culture. Intriguingly, the miR-148a expression in cell culture medium was elevated by DIP treatment of BMEC culture (P = 0.018). The medium-to-cell expression ratios of miR-103 (P = 0.025), miR-148a (P < 0.001), and miR-223 (P = 0.013) were elevated in the DIP-treated BMECs, suggesting that the lactogenic differentiation-induced secretion of these three miRNAs in BMECs. A bioinformatic analysis showed that the miRNAs down-regulated in the BMECs were associated with the suppression of genes related to transcriptional regulation, protein phosphorylation, and tube development.
  
  
  CONCLUSIONS
  The results suggest that the miRNAs changed by lactogenic hormones are associated with milk protein synthesis, and mammary gland development and maturation. The elevated miR-148a level in DIP-treated BMECs may be associated with its increase in milk during the lactation period of cows.
authors.affiliation: Animal Products Research Division, NARO Institute of Livestock and Grassland Science, Tsukuba, Ibaraki 305-0901 Japan.
authors.forename: Susumu
authors.identifier: 0000-0002-2376-9352
authors.initials: S
authors.lastname: Muroya
authors.affiliation: Animal Products Research Division, NARO Institute of Livestock and Grassland Science, Tsukuba, Ibaraki 305-0901 Japan.
authors.forename: Tatsuro
authors.initials: T
authors.lastname: Hagi
authors.affiliation: Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki, Aomori Japan.
authors.forename: Ataru
authors.initials: A
authors.lastname: Kimura
authors.affiliation: International Education and Research Center for Food and Agricultural Immunology (CFAI), Graduate School of Agricultural Science, Tohoku University, Aoba Sendai, Japan.
authors.forename: Hisashi
authors.initials: H
authors.lastname: Aso
authors.affiliation: Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki, Aomori Japan.
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Matsuzaki
authors.affiliation: Animal Products Research Division, NARO Institute of Livestock and Grassland Science, Tsukuba, Ibaraki 305-0901 Japan.
authors.forename: Masaru
authors.initials: M
authors.lastname: Nomura
keywords: Bovine mammary epithelial cell; Lactogenic differentiation; Milk; Secretion; microRNA