Nørgaard J V, Theil P K, Sørensen M T, Sejrsen K
Department of Animal Health, Welfare and Nutrition, University of Aarhus, PO Box 50, DK-8830, Tjele, Denmark.
J Dairy Sci. 2008 Jun;91(6):2319-27. doi: 10.3168/jds.2007-0767.
The mechanisms involved in regulating mammary cell turnover during the pregnancy-lactation cycle in dairy cows are unclear. The objective of present experiment was to describe expression of genes encoding proteins known to be involved in pathways regulating mammary cell proliferation, apoptosis, differentiation, cell survival, and tissue remodeling. Mammary gland biopsies were taken 7 times during the pregnancy-lactation cycle of 10 dairy cows, and samples were analyzed by immunohistochemistry and real-time PCR. Cell proliferation was greatest during the dry period and apoptosis was high in early dry period and early lactation. Based on Fas (tumor necrosis factor receptor superfamily member 6), Fas ligand, and caspase-3, caspase-8, and caspase-9 gene expression, no indication was found of a stage-dependent shift between the extrinsic and intrinsic pathways leading to apoptosis. Gene expression of microsomal glutathione S-transferase (mGST) did not vary significantly, whereas B-cell leukemia/lymphoma 2 (Bcl-2) and BCL2-associated X protein (Bax) gene expression was greatest during the dry period and early lactation and coincided with high cell turnover. Gene expression of early response genes c-Fos, c-Jun, and c-Myc correlated to neither rate of cell proliferation nor plasma concentration of insulin-like growth factor (IGF)-I and insulin. Gene expression of nuclear factor of kappa light chain gene enhancer in B-cells (NFkappaB) and NFkappaB inhibitor alpha was greatest in the periparturient period, and NFkappaB gene expression coincided with an anticipated need for cell survival factors. Expression of transforming growth factor beta (TGF-beta) receptor 1 and 2 mRNA was greatest in early lactation, whereas TGF-beta1 did not vary significant during the pregnancy-lactation cycle. Even though our results on the TGF-beta system did not comply with other studies, the gene expression pattern of the TGF-beta receptors indicates a role in regulating apoptosis in early lactation. Signal transducer and activator of transcription 5 (STAT5) gene expression was high in the periparturient period, which suggests a role for STAT5 in regulation of mammary cell proliferation and differentiation in dairy cows. Expression of tissue-plasminogen activator, plasminogen activator inhibitor-1, and IGF binding protein 5 genes was greatest in early lactation, suggesting a role for IGF binding protein 5 in coordinating regulation of apoptosis and tissue remodeling.
奶牛妊娠 - 泌乳周期中调节乳腺细胞更新的机制尚不清楚。本实验的目的是描述已知参与调节乳腺细胞增殖、凋亡、分化、细胞存活和组织重塑途径的蛋白质编码基因的表达情况。在10头奶牛的妊娠 - 泌乳周期中进行了7次乳腺活检，并通过免疫组织化学和实时定量PCR对样本进行分析。细胞增殖在干奶期最大，凋亡在干奶初期和泌乳初期较高。基于Fas（肿瘤坏死因子受体超家族成员6）、Fas配体以及半胱天冬酶 - 3、半胱天冬酶 - 8和半胱天冬酶 - 9基因表达，未发现导致凋亡的外在和内在途径之间存在阶段依赖性转变的迹象。微粒体谷胱甘肽S - 转移酶（mGST）的基因表达没有显著变化，而B细胞淋巴瘤/白血病 - 2（Bcl - 2）和BCL2相关X蛋白（Bax）的基因表达在干奶期和泌乳初期最大，且与高细胞更新率一致。早期反应基因c - Fos、c - Jun和c - Myc的基因表达与细胞增殖率以及胰岛素样生长因子（IGF）-I和胰岛素的血浆浓度均无相关性。B细胞中κ轻链基因增强子的核因子（NFκB）和NFκB抑制剂α的基因表达在围产期最大，且NFκB基因表达与预期的细胞存活因子需求一致。转化生长因子β（TGF - β）受体1和2 mRNA的表达在泌乳初期最大，而TGF - β1在妊娠 - 泌乳周期中没有显著变化。尽管我们关于TGF - β系统的结果与其他研究不一致，但TGF - β受体的基因表达模式表明其在调节泌乳初期凋亡中起作用。信号转导和转录激活因子5（STAT5）的基因表达在围产期较高，这表明STAT5在奶牛乳腺细胞增殖和分化的调节中起作用。组织纤溶酶原激活物、纤溶酶原激活物抑制剂 - 1和IGF结合蛋白5基因的表达在泌乳初期最大，表明IGF结合蛋白5在协调凋亡和组织重塑的调节中起作用。
