Effects of cell culture techniques on gene expression and cholesterol efflux in primary bovine mammary epithelial cells derived from milk and tissue

Primary bovine mammary epithelial cells (pbMEC) are often used in cell culture to study metabolic and inflammatory processes in the udder of dairy cows. The most common source is udder tissue from biopsy or after slaughter. However, it is also possible to culture them from milk, which is non-invasive, repeatable and yields less contamination with fibroblasts. Generally, not much is known about the influence of cell origin and cell culture techniques such as cryopreservation on pbMEC functionality. Cells were extracted from milk and udder tissue to evaluate if milk-derived pbMEC are a suitable alternative to tissue-derived pbMEC and to test what influence cryopreservation has. The cells were cultivated for three passages and stored in liquid nitrogen. The relative gene expression of the five target genes kappa-casein, lingual antimicrobial peptide (LAP), lactoferrin, lysozyme (LYZ1) and the prolactin receptor normalised with keratin 8 showed a tendency to decrease in the tissue cultures, but not in the milk-derived cultures, suggesting a greater influence of the cultivation process on tissue-derived cells, freezing lowered expression levels in both cultures. Overall expression of LAP and LYZ1 tended to be higher in milk cells. Cholesterol efflux was measured to compare passages one to seven in milk-derived cells. Passage number did not alter the efflux rate (p ≤ 0.05). We showed for the first time that the extraction of pbMEC from milk can be a suitable alternative to tissue extraction.