This study attempted to establish a culture model to recreate the milk production pathway in bovine mammary epithelial cells (BMECs). BMECs were isolated from Holstein cows (nonlactating, nonpregnant, and parous) and were stored by cryopreservation. To separate the apical and basolateral compartments, BMECs were cultured on a cell culture insert with a collagen gel in the presence of bovine pituitary extract and dexamethasone to induce milk production and tight junction (TJ) formation. The culture model showed the secretion of the major milk components, such as β‐casein, lactose, and triglyceride, and formed less‐permeable TJs in BMECs. Moreover, the TJs were distinctly separated from the apical and basolateral membranes. Glucose transporter‐1, which transports glucose into the cytoplasm through the basolateral membrane, localized in the lateral membrane of BMECs. Toll‐like receptor‐4, which binds to lipopolysaccharide in the alveolar lumen in mastitis, localized in the apical membrane. Beta‐casein was mainly localized near the Golgi apparatus and the apical membrane. Moreover, milk components were almost secreted into the upper chamber of the cell culture insert. These findings indicate that this model has clear cell polarity as well as in vivo and is effective to study of milk production and the blood–milk barrier in lactating BMECs.

中文翻译：

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牛乳腺上皮细胞体外培养模型的建立以研究产奶量和血乳屏障。

本研究试图建立一种培养模型，以重建牛乳腺上皮细胞 (BMEC) 中的产奶途径。BMECs 是从荷斯坦奶牛（非哺乳期、非妊娠期和经产期）中分离出来的，并通过冷冻保存进行储存。为了分离顶端和基底外侧隔室，BMEC 在牛垂体提取物和地塞米松存在下用胶原凝胶在细胞培养插入物上培养，以诱导产奶和紧密连接 (TJ) 形成。培养模型显示主要乳成分的分泌，如 β-酪蛋白、乳糖和甘油三酯，并在 BMEC 中形成渗透性较低的 TJ。此外，TJ 与顶膜和基底外侧膜明显分离。葡萄糖转运蛋白-1，它通过基底外侧膜将葡萄糖转运到细胞质中，定位于 BMEC 的侧膜。Toll 样受体 4，在乳腺炎中与位于顶膜的肺泡腔中的脂多糖结合。β-酪蛋白主要位于高尔基体和顶膜附近。此外，乳成分几乎分泌到细胞培养插入物的上腔室中。这些发现表明该模型具有清晰的细胞极性以及体内模型，可有效研究泌乳 BMEC 的产奶量和血乳屏障。