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Growing mammary epithelial cells as organoids in a three-dimensional (3D) cell culture environment represents a more physiological model system than conventional 2D adherent cell culture systems for studying many different aspects of mammary epithelial cell biology. We have developed MammoCult™ Organoid Growth Medium (Mouse), a serum- and phenol red-free medium for the long-term propagation of organoids from mouse mammary tissue. To initiate the cultures, mouse mammary glands are resected and enzymatically dissociated sequentially in Gentle Collagenase/Hyaluronidase, trypsin, and dispase/DNase I to generate a single-cell suspension, and 4.5 x 103 of the liberated cells are then embedded in Corning® Matrigel® and maintained in MammoCult™ Organoid Growth Medium (Mouse). Alternatively, freshly dissociated mammary cells can be expanded in adherent culture in EpiCult™ Plus Medium prior to seeding into Matrigel®. Approximately 8.4 ± 0.6% (mean ± SEM; n=10) of the freshly dissociated cells seeded in the Corning® Matrigel® will proliferate and generate organoids that are typically > 200 µm in diameter and have a highly branched morphology, although organoids with a cystic morphology are also observed. Immunostaining of these branched organoids reveals that they are composed of a polarized epithelium made up of keratin (K) 8-expressing luminal cells and K5/14-expressing basal cells (n=7). Organoids upregulate transcripts for caseins (Csn1s1, Csn2), whey acidic protein (Wap), and lactoferrin (Ltf) upon stimulation with prolactin, hydrocortisone, and insulin (n=4). These multilineage organoids can be established from multiple inbred mouse strains, including C57Bl6/J, FVB, BALB/c, and CD-1. Organoids can be passaged every 10 - 14 days as small fragments at a 1:3 to 1:4 split ratio, and can be maintained for a minimum of 10 passages while still maintaining multilineage potential and a normal karyotype. These results demonstrate that MammoCult™ Organoid Growth Medium (Mouse) efficiently generates and expands mammary epithelial cell-derived organoids and offers researchers a novel tool for in vitro mammary studies. Citation Format: David Rowbotham, Samantha Rothwell, Allen C. Eaves, Sharon A. Louis, John Stingl. Expansion of mouse mammary epithelial stem cells in serum-free organoid growth medium [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6018. |
