Investigation on the suitability of milk-derived primary bovine mammary epithelial cells grown on permeable membrane supports as an in vitro model for lactation

This study aimed to establish an in vitro model for lipid synthesis in primary bovine mammary epithelial cells (pbMECs) extracted from milk and cultured on Transwell permeable supports (TW culture). The suitability of these cells as a functional model for lactation was assessed by measuring kappa-casein (CSN3) and diacylglycerol acyl transferase 1 (DGAT1) gene expression, the presence of intracellular lipid droplets, and the concentration of triacylglycerol in the cell lysates. The functionality of the milk-derived pbMECs cultured under lactogenic conditions, with and without oleic acid supplementation, was evaluated by comparing the cells grown on Transwell supports to cells grown on an extracellular matrix (ECM) gel (3D culture) or a plastic surface (2D culture). Furthermore, the functionality of milk-derived cells was compared to pbMECs obtained from bovine mammary tissue. Here, we show that in both tissue and milk-derived pbMECs, 3D culture offered the most suitable in vitro environment and led to increased levels of CSN3 and DGAT1 gene expression along with increased intracellular triacylglycerol content. The TW culture conditions also resulted in increased DGAT1 gene expression compared to the 2D conditions and milk-derived pbMECs cultured on TW inserts showed the highest viability compared to cells grown under 2D or 3D treatments. However, this was not observed for tissue-derived pbMECs, suggesting that TW culture may offer a beneficial environment specifically for milk-derived cells. We suggest that with further optimization of the culture conditions, TW culture may present a suitable model for the study of milk lipid synthesis in pbMECs.