Submitted to: Joint Abstracts of the American Dairy Science and Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: February 17, 2006
Publication Date: July 9, 2006
Citation: Capuco, A.V. 2006. Identification of putative bovine mammary stem cells by their retention of labeled DNA strands [abstract]. Journal of Dairy Science. 89(Suppl 1):147.
Stem cells characteristically retain labeled DNA for extended periods due to their selective segregation of template DNA strands during mitosis. In this study, proliferating cells in the prepubertal bovine mammary gland were labeled using five daily injection of 5-bromo-2-deoxyuridine (BrdU). Five weeks later, BrdU-labeled mammary epithelial cells were still evident. The percentage of BrdU-labeled epithelial cells was greatest in basal regions of the mammary gland and decreased toward the periphery of the parenchymal region, where the ducts were invading the mammary fat pad. Increased numbers of BrdU-labeled epithelial cells in basal regions of the gland are likely a consequence of decreased proliferation rates and increased cell cycle arrest in this area. In peripheral regions of mammary parenchyma, the percentage of heavily labeled epithelial cells averaged 0.24%, a number that is consistent with estimates of the frequency of stem cells in mouse mammary gland. Epithelial, label-retaining cells represent a slowly proliferating population, as 5.4% were positive for the nuclear proliferation antigen, Ki67. Furthermore these putative stem cells can likely respond directly to mitogenic stimulation by estrogen, as 57% of the BrdU-labeled epithelial cells were estrogen receptor-positive. Continuing studies will address the usefulness of this technique to identify bovine mammary stem cells and facilitate studies of stem cell biology.