Beginning in 2014 our laboratory began exploring the harvest of mammary stem cells from cow’s milk. Potential practical applications of these cells in the future would be in biotechnology, using these secretory cells as miniature “factories†to produce valuable biologic materials such as protein-based pharmaceuticals. Therefore in this study we report cultures of primary cells derived from milk samples and maintained for up to a year in 2D monolayers. During that period, the initially harvested stem cells developed into mature monolayers of differentiated ductal cells which display at least three distinct phenotypes reflective of normal tissue components. These include squamous ductal epithelial cells, lipid-filled mammocytes and myoepithelial cells displaying significant stress fibers. These monolayers also presented with tissue-like regions of specialization containing uniquely one cell type or another. In addition, following approximately 6 months of uninterrupted culture, monolayers displayed organization into 3D structures that presented all the structural features of actual in-vivo ducts and alveolar sacs. A unique multinucleate phenotype that has been described in the literature as functioning to organize development was also observed in these cultures. Such cells eventually became the predominant cell type present in older cultures. This cell type is multinucleated or syncytial containing from 2 to 8 nuclei, but generally focused around 2 nuclei each. Continuing studies are focused on testing various stem cell media formulations to optimize culture conditions.
