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CRC for Innovative Dairy Products, Department of Zoology, University of Melbourne, Melbourne, Victoria 3010, Australia

(Correspondence should be addressed to A J Brennan; Email: a.brennan2{at}pgrad.unimelb.edu.au)

This research was supported with funding from the Cooperative Research Centre for Innovative Dairy Products. The author was supported with funding from a Melbourne University Research Scholarship. There is no conflict of interest that would prejudice the impartiality of the work presented.

Hormonal stimulation of mammary explants mimics many of the biochemical changes observed during lactogenesis. Previous studies using eutherian species conclude that mammary explants require addition of exogenous macromolecules to remain hormone responsive in culture. The present study examines the survival of mammary explants from the wallaby and mouse using milk protein gene expression as a functional marker of lactation and cell viability. Mammary explants from pregnant tammars and mice showed that milk protein gene expression was significantly elevated after 3 days of culture with lactogenic hormones. The subsequent removal of exogenous hormones from the media for 10 days resulted in the down-regulation of milk protein genes. Surprisingly, mammary explants remained hormone responsive and expression of milk protein genes was re-induced after a second challenge with lactogenic hormones. Furthermore, the alveolar architecture was maintained. Global functional microarray analysis showed that classic involution markers were not differentially expressed, although two stress-induced survival genes were significantly up-regulated. We report that a population of mammary epithelial cells have an intrinsic capacity to remain viable and hormone responsive for extended periods in chemically defined media without any exogenous macromolecules. We propose that the mammary explant culture model uncouples the first phase of involution, as milk accumulation that normally provides involution stimuli is absent in this culture model allowing a population of cells to survive.

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				A. J Brennan, J. A Sharp, C. M Lefevre, and K. R Nicholas Uncoupling the mechanisms that facilitate cell survival in hormone-deprived bovine mammary explants J. Mol. Endocrinol., September 1, 2008; 41(3): 103 - 116. [Abstract] [Full Text] [PDF]