INRA, UMR1313 Unité Génétique Animale et Biologie Intégrative, équipe «Lait, Génome & Santé», F-78350 Jouy-en-Josas, France.
Vet Res. 2014 Feb 12;45(1):16. doi: 10.1186/1297-9716-45-16.
To differentiate between the contribution of mammary epithelial cells (MEC) and infiltrating immune cells to gene expression profiles of mammary tissue during early stage mastitis, we investigated in goats the in vivo transcriptional response of MEC to an experimental intra mammary infection (IMI) with Staphylococcus aureus, using a non-invasive RNA sampling method from milk fat globules (MFG). Microarrays were used to record gene expression patterns during the first 24 hours post-infection (hpi). This approach was combined with laser capture microdissection of MEC from frozen slides of mammary tissue to analyze some relevant genes at 30 hpi. During the early stages post-inoculation, MEC play an important role in the recruitment and activation of inflammatory cells through the IL-8 signalling pathway and initiate a sharp induction of innate immune genes predominantly associated with the pro-inflammatory response. At 30 hpi, MEC express genes encoding different acute phase proteins, including SAA3, SERPINA1 and PTX3 and factors, such as S100A12, that contribute directly to fighting the infection. No significant change in the expression of genes encoding caseins was observed until 24 hpi, thus validating our experimental model to study early stages of infection before the occurrence of tissue damage, since the milk synthesis function is still operative. This is to our knowledge the first report showing in vivo, in goats, how MEC orchestrate the innate immune response to an IMI challenge with S. aureus. Moreover, the non-invasive sampling method of mammary representative RNA from MFG provides a valuable tool to easily follow the dynamics of gene expression in MEC to search for sensitive biomarkers in milk for early detection of mastitis and therefore, to successfully improve the treatment and thus animal welfare.
为了区分乳腺炎早期乳腺上皮细胞（MEC）和浸润免疫细胞对乳腺组织基因表达谱的贡献，我们在山羊中采用非侵入性的从乳脂肪球（MFG）中提取 RNA 的方法，研究了 MEC 对金黄色葡萄球菌的实验性乳腺内感染（IMI）的体内转录反应。使用微阵列记录了感染后 24 小时内（hpi）的基因表达模式。该方法与冷冻乳腺组织切片上的 MEC 激光捕获显微解剖相结合，以在 30 hpi 时分析一些相关基因。在接种后早期，MEC 通过 IL-8 信号通路在招募和激活炎症细胞方面发挥重要作用，并引发与促炎反应相关的固有免疫基因的急剧诱导。在 30 hpi 时，MEC 表达编码不同急性期蛋白的基因，包括 SAA3、SERPINA1 和 PTX3 以及直接有助于对抗感染的因子，如 S100A12。直到 24 hpi 时，编码酪蛋白的基因表达才观察到明显变化，从而验证了我们的实验模型可在发生组织损伤之前研究感染的早期阶段，因为此时牛奶合成功能仍然有效。据我们所知，这是首次在山羊体内报道 MEC 如何协调对金黄色葡萄球菌 IMI 挑战的固有免疫反应。此外，从 MFG 中提取乳腺代表性 RNA 的非侵入性采样方法为研究 MEC 中基因表达的动态提供了一种有价值的工具，以寻找牛奶中的敏感生物标志物，用于早期检测乳腺炎，从而成功改善治疗效果并提高动物福利。
