Cell hierarchy and lineage commitment in the bovine mammary gland

• Published in: PloS one 2012-01, Vol.7 (1), p.e30113-e30113
• Main Authors: Rauner, Gat, Barash, Itamar
• Format: Article
• Language: English
• Subjects: Aldehyde Dehydrogenase - metabolism; Analysis; Animal sciences; Animals; Basal cells; Biology; Biomarkers; Biomarkers - metabolism; Breast cancer; Breastfeeding & lactation; Breasts; Cattle; CD24 Antigen - metabolism; Cell Aggregation; Cell Count; Cell culture; Cell Lineage; Cell number; Cell surface; Cells, Cultured; Clone Cells; Colonies; Colony-Forming Units Assay; Epithelial cells; Epithelial Cells - cytology; Epithelial Cells - enzymology; Extracellular matrix; Female; Fluorescent Antibody Technique; Gene expression; Gene Expression Regulation; Genes; Growth factors; Hormones; Humans; Integrin alpha6 - metabolism; Jagged1 protein; Localization; Mammals; Mammary gland; Mammary Glands, Animal - cytology; Mammary Glands, Animal - metabolism; Medicine; Models, Biological; Multipotent Stem Cells - cytology; Multipotent Stem Cells - metabolism; Notch1 protein; Population; Populations; Propagation; Rodents; Senescence; Stem cell transplantation; Stem cells; Surface markers; Veterinary Science; Zoology
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0030113

The bovine mammary gland is a favorable organ for studying mammary cell hierarchy due to its robust milk-production capabilities that reflect the adaptation of its cell populations to extensive expansion and differentiation. It also shares basic characteristics with the human breast, and identification of its cell composition may broaden our understanding of the diversity in cell hierarchy among mammals. Here, Lin⁻ epithelial cells were sorted according to expression of CD24 and CD49f into four populations: CD24(med)CD49f(pos) (putative stem cells, puStm), CD24(neg)CD49f(pos) (Basal), CD24(high)CD49f(neg) (putative progenitors, puPgt) and CD24(med)CD49f(neg) (luminal, Lum). These populations maintained differential gene expression of lineage markers and markers of stem cells and luminal progenitors. Of note was the high expression of Stat5a in the puPgt cells, and of Notch1, Delta1, Jagged1 and Hey1 in the puStm and Basal populations. Cultured puStm and Basal cells formed lineage-restricted basal or luminal clones and after re-sorting, colonies that preserved a duct-like alignment of epithelial layers. In contrast, puPgt and Lum cells generated only luminal clones and unorganized colonies. Under non-adherent culture conditions, the puPgt and puStm populations generated significantly more floating colonies. The increase in cell number during culture provides a measure of propagation potential, which was highest for the puStm cells. Taken together, these analyses position puStm cells at the top of the cell hierarchy and denote the presence of both bi-potent and luminally restricted progenitors. In addition, a population of differentiated luminal cells was marked. Finally, combining ALDH activity with cell-surface marker analyses defined a small subpopulation that is potentially stem cell-enriched.