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Published on: February 8, 2013
Cell proliferation in bovine mammary epithelium: identification of the primary proliferative cell population
1Gene Evaluation and Mapping Laboratory, USDA Agricultural Research Center, Building 200, BARC-East, 20705, Beltsville, MD 20705, USA. acapuco@anri.barc.usda.gov
Insights
Lightly staining mammary cells in heifers are the primary source of cell proliferation, suggesting they function as mammary stem cells. This research identifies key cell populations involved in mammary gland development.
Area of Science:
- Veterinary Science
- Cell Biology
- Mammary Gland Biology
Background:
- Mammary stem cells are crucial for mammary gland development and function.
- Previous histologic analyses suggested a lightly staining cell population might serve as mammary stem cells.
Purpose of the Study:
- To investigate the hypothesis that lightly staining mammary parenchymal cells function as mammary stem cells.
- To analyze mammary epithelial cell proliferation in prepubertal Holstein heifers.
Main Methods:
- Histologic analysis of mammary parenchyma in prepubertal Holstein heifers.
- Bromodeoxyuridine (BrdU) injection to label proliferating cells.
- Staining with basic fuschin and azure II to differentiate cell populations (light, intermediate, dark).
Main Results:
- Lightly staining cells, comprising 10% of the population, accounted for 50% of cell proliferation.
- Intermediate cells (60% of population) showed 43% proliferation, while dark cells (30% of population) showed only 7% proliferation.
- BrdU+ cell distribution correlated with parenchymal layers, but basal layer mitosis was lower than expected, suggesting cell cycle arrest or migration.
Conclusions:
- Results strongly support the role of lightly staining mammary parenchymal cells as the primary proliferative cell population.
- These findings indicate that lightly staining cells are likely the mammary stem cells responsible for mammary gland growth.
Abstract:
Histologic analyses indicate that a lightly staining cell population present in mammary parenchyma may function as mammary stem cells. We performed an analysis of mammary epithelial cell proliferation in prepubertal bromodeoxyuridine (BrdU)-injected Holstein heifers to investigate this hypothesis. We observed light, dark, and intermediate staining cells in histologic sections stained with basic fuschin and azure II. Light cells comprised 10% of the total parenchymal cell population but accounted for 50% of the cell proliferation. Intermediate cells comprised 60% of the cell population and 43% of proliferating cells. Dark cells comprised 30% of the parenchymal cell population but only 7% of proliferating cells. The distribution of BrdU+ cells across basal, embedded, and lumenal parenchymal cell layers was correlated with the fraction of total parenchymal cells present in each layer (r=0.99). However, the proportion of mitotic cells observed in the basal cell layer was only half of what would be predicted by the BrdU-labeling data. This observation suggests that some basal cells either arrest in G(2) or migrate into the suprabasal epithelial layers before undergoing mitosis. These results strongly support the concept that lightly staining mammary parenchymal cells are the primary proliferative cell population.
