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This Article Accepted manuscript (PDF) All Versions of this Article: JME-08-0035v1 JME-08-0035v2 41/3/103    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Brennan, A. Articles by Nicholas, K. Search for Related Content PubMed PubMed Citation Articles by Brennan, A. Articles by Nicholas, K.

A Brennan, Zoology, University of Melbourne, Parkville, 3010, Australia
J Sharp, Zoology, University of Melbourne, Parkville, Australia
C Lefevre, Zoology, University of Melbourne, Parkville, Australia
K Nicholas, Zoology, University of Melbourne, Parkville, Australia

Correspondence: Amelia Brennan, Email: a.brennan2{at}pgrad.unimelb.edu.au

Abstract

Mammary explants can be hormonally stimulated to mimic the biochemical changes that occur during lactogenesis. Previous studies using mammary explants concluded that the addition of exogenous macromolecules were required for mammary epithelial cells to remain viable in culture. The current study examines survival of mammary explants from the dairy cow using milk protein gene expression as a functional marker of lactation and cell viability. Mammary explants cultured from late-pregnant cows mimicked lactogenesis and showed significantly elevated milk protein gene expression after 3 days of culture with lactogenic hormones. The subsequent removal of exogenous hormones from the media for 10 days resulted in the downregulation of milk protein genes. During this time the mammary explants remained hormone responsive, the alveolar architecture was maintained, and the expression of milk protein genes was re-induced after a second challenge with lactogenic hormones. We report that a population of bovine mammary epithelial cells have an intrinsic capacity to remain viable and hormone responsive for extended periods in chemically defined media without any exogenous macromolecules. In addition, we found mammary explant viability was dependent on de novo protein and RNA synthesis. Global functional micorarray analysis showed that differential expression of genes involved with energy production, immune responses, oxidative stress and apoptosis signaling might contribute to cell survival. As the decline in milk production in dairy cattle after peak lactation results in considerable economic loss, the identification of novel survival genes may be used as genetic markers for breeding programs to improve lactational persistency in dairy cows.