From inserts to 3D spheroids: MAC-T and BME-UV1 co-culture models for in vitro reconstruction of the bovine mammary epithelial architecture.

Two bovine mammary epithelial cell lines, MAC-T and BME-UV1, were co-cultured either in Transwell® inserts or in 3D culture systems to comparatively investigate their potential to mimic the structure and function of a mammary alveolus. Using either Matrigel® or animal-friendly alternatives, i.e. rat collagen type I, a mixture of rat collagen type I and mouse laminin, Vitrogel® or matrix-free ultra-low attachment surfaces, both co-culture mammosphere development and tight junction formation were assessed. On Transwell® inserts, co-culture failed to establish a functional epithelial barrier. In contrast, varying patterns of cell-cell interaction and barrier organization emerged using the different 3D co-culture systems, providing new insights into the reconstruction of physiologically relevant and animal-friendly models of the bovine mammary gland.