Brennan Amelia J, Sharp Julie A, Lefèvre Christophe M, Nicholas Kevin R
CRC for Innovative Dairy Products, Department of Zoology, University of Melbourne, Gate 13 Royal Parade, Melbourne, Victoria 3010, Australia.
J Mol Endocrinol. 2008 Sep;41(3):103-16. doi: 10.1677/JME-08-0035. Epub 2008 Jun 5.
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 present study examines the 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 down-regulation 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 microarray analysis showed that differential expression of genes involved in energy production, immune responses, oxidative stress and apoptosis signalling 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 programmes to improve lactational persistency in dairy cows.
乳腺外植体可通过激素刺激来模拟泌乳发生过程中出现的生化变化。以往使用乳腺外植体的研究得出结论，乳腺上皮细胞要在培养中保持存活需要添加外源性大分子。本研究以牛奶蛋白基因表达作为泌乳和细胞活力的功能标志物，检测了奶牛乳腺外植体的存活情况。用怀孕后期奶牛培养的乳腺外植体模拟泌乳过程，在用泌乳激素培养3天后，牛奶蛋白基因表达显著升高。随后从培养基中去除外源性激素10天，导致牛奶蛋白基因下调。在此期间，乳腺外植体仍对激素有反应，腺泡结构得以维持，在用泌乳激素再次刺激后，牛奶蛋白基因的表达被重新诱导。我们报告称，一群牛乳腺上皮细胞具有在化学成分确定的培养基中长时间保持存活且对激素有反应的内在能力，无需任何外源性大分子。此外，我们发现乳腺外植体的活力依赖于从头合成蛋白质和RNA。全基因组功能微阵列分析表明，参与能量产生、免疫反应、氧化应激和凋亡信号传导的基因差异表达可能有助于细胞存活。由于奶牛泌乳高峰期后产奶量下降会导致相当大的经济损失，鉴定新的存活基因可作为育种计划的遗传标记，以提高奶牛的泌乳持续性。
