AgResearch Ltd., Ruakura Research Centre, Private Bag 3123, Hamilton 3214, New Zealand.
AgResearch Ltd., Ruakura Research Centre, Private Bag 3123, Hamilton 3214, New Zealand; DairyNZ Ltd., Hamilton 3286, New Zealand.
J Dairy Sci. 2017 Sep;100(9):7669-7685. doi: 10.3168/jds.2017-12572. Epub 2017 Jul 12.
The aim of this study was to investigate heterogeneity in tissue morphology, milk protein and immune-related gene expression, and apoptosis of epithelial cells in the lactating and involuting mammary glands of the dairy cow. Mammary tissue from different regions of the gland (alveolar, cisternal, and peripheral) was collected postmortem from nonpregnant, pasture-fed, Holstein-Friesian primiparous cows in mid-lactation that were killed at different time points postmilking: 0, 6, 12, 18, 24, 36, and 72 h (n = 6 per time point). The CSN1NS1 and LALBA mRNA was decreased in alveolar, cisternal, and peripheral tissue by 12 to 36 h postmilking. In contrast, lactoferrin (LF) and mammary serum amyloid A3 (M-SAA3) mRNA was increased in these regions by 36 to 72 h. During lactation, more variability was present in gene expression in alveolar tissue between cows and between quarters within a cow, than within quarters. Histological analysis indicated the alveolar tissue from lactating cows was mostly uniform in structure; however, in situ hybridization indicated that although most of the alveolar tissue expressed milk proteins, the level of expression varied within and between alveoli. This heterogeneity became more pronounced with involution and with increasing regions of alveoli expressing lactoferrin, indicating that alveoli enter involution asynchronously. The peripheral and cisternal tissue had more variability in gene expression between cows compared with the alveolar tissue. The M-SAA3 signal was more intense in the cisternal tissue and less intense than the peripheral compartment compared with LF particularly in the earlier time points. In addition, between cows within the later time points, differences were observed in tissue morphology, the levels of milk protein and immune-related gene expression, and phosphorylated signal transducer and activator of transcription (STAT) 5-P and STAT3-P proteins, and degree of apoptosis, indicating that involution of the mammary gland occurs at different rates between cows. Understanding the mechanisms initiating the process of involution of the mammary gland provides an opportunity for enhancing milk production of the dairy cow.
本研究旨在探讨奶牛泌乳期和退化期乳腺组织形态、乳蛋白和免疫相关基因表达以及上皮细胞凋亡的异质性。从不同区域（腺泡、乳池和外周）采集死后的泌乳中期、非妊娠、放牧、荷斯坦弗里生初产奶牛的乳腺组织，在挤奶后不同时间点（0、6、12、18、24、36 和 72 h，n = 6/时间点）处死。CSN1NS1 和 LALBAmRNA 在挤奶后 12 至 36 小时在腺泡、乳池和外周组织中减少，而乳铁蛋白（LF）和乳血清淀粉样蛋白 A3（M-SAA3）mRNA 在这些区域在 36 至 72 小时增加。在泌乳期，奶牛之间和奶牛的不同乳区间的基因表达变化更大。组织学分析表明，泌乳奶牛的腺泡组织结构基本一致；然而，原位杂交表明，尽管大多数腺泡组织表达乳蛋白，但表达水平在腺泡内和腺泡间存在差异。这种异质性在退化期变得更加明显，并且随着乳池组织中乳铁蛋白表达的增加而变得更加明显，表明腺泡以不同的速度进入退化期。与腺泡组织相比，外周和乳池组织中奶牛间的基因表达变化更大。与 LF 相比，M-SAA3 信号在乳池组织中更强烈，在外周组织中较弱，特别是在早期时间点。此外，在较晚的时间点，不同奶牛之间观察到组织形态、乳蛋白和免疫相关基因表达水平、磷酸化信号转导和转录激活因子 5-P（STAT5-P）和 STAT3-P 蛋白以及凋亡程度的差异，表明奶牛的乳腺退化速度不同。了解启动乳腺退化过程的机制为提高奶牛产奶量提供了机会。
