Establishment and initial characterization of the ovine mammary epithelial cell line NISH

Analysis of the molecular mechanisms involved in the differentiation and formation of the characteristic three-dimensional structures of the developing mammary gland of the major milk-producing livestock (ducts, end buds, and alveoli) requires in vitro model cell cultures. The few cell lines that have been established from dairy animals do not fully reproduce the entire program of mammary differentiation. Here we present the initial characterization of a unique mammary epithelial cell line derived spontaneously from midpregnant sheep (NISH). These cells form in vitro functional structures resembling ducts, lateral buds, and alveoli that secrete beta-lactoglobulin (BLG) in an ECM (extracellular matrix)-dependent manner. Interestingly, the presence of growth hormone dramatically increased BLG secretion from NISH cells cultured on ECM. It appears that GH is required not only to establish the structural organization but also is continuously needed to maintain BLG expression. Stable transfection of NISH cells with BLG/Human Serum Albumin (HSA) hybrid gene constructs revealed that the relative level of expression was comparable to the in vivo secretion of HSA in transgenic mice carrying these gene sequences. No expression could be detected in cells transfected with hybrid genes carrying either HSA cDNA or the entire HSA gene, and HSA expression was dependent on the presence of intronic sequences. These results demonstrate that NISH cells may prove a useful tool for studying the differentiation and organogenesis of mammary epithelial cells under defined culture conditions. Furthermore, transfected NISH cells may be an alternative for the transgenic mouse model in evaluating the potential of gene constructs to be efficiently expressed in the mammary gland of transgenic farm animals.