Research Paper Volume 8, Issue 11 pp 2754—2776

Figure 1. Mammary epithelial cell population and stem/progenitor cell frequency change during aging. (a) Cells with high levels of CD49f are MaSC-enriched basal cells, and cells with high levels of CD24 are luminal progenitor-enriched luminal cells. Representative flow cytometry analysis of mammary epithelial cells from young (3 mo) and old (26 mo) virgin C57BL6/J mice. (b-d) Mammary epithelial cell population changes during aging. Percent basal cells (CD24^loCD49f^hi) (b), percent luminal cells (CD24^hiCD49f^lo) (c), and luminal-to-basal cell ratio (d) of Lin- mammary epithelial cells isolated from young and old virgin C57BL/6 (age, 2-4 mo vs. 25-32 mo; n = 15 vs. 9) and BALB/c mice (age, 2-4 mo vs. 17 mo; n = 8 vs. 5). (e-f) Stem/progenitor cell frequency changes during aging. Average frequencies of MaSC (e) expressed as % sphere formation and differentiation-initiating cells from basal cells (SFD-IC_b), luminal progenitor cells (f) expressed as % sphere formation and differentiation-initiating cells from luminal cells (SFD-IC_l), and luminal progenitor cells (g) expressed as % colony forming cell (CFC) from luminal cells in young and old virgin C57BL/6 (age, 2-3 mo vs. 25-26 mo; n = 6) and BALB/c mice (age, 2-4 mo vs. 17 mo; n = 8 vs. 5). (h-k) Representative examples of whole mount carmine alum staining of mammary glands collected from young (h) and old (i-k) virgin C57BL6/J mice. Scale bars, 1 mm.