Skip to main content
. Author manuscript; available in PMC: 2014 Sep 5.
Published in final edited form as: Cell Stem Cell. 2013 Jul 18;13(3):300–313. doi: 10.1016/j.stem.2013.06.005

Figure 7. MECs from MMP3 Null Mice have Reduced MaSC Capacity.

Figure 7

(A) MaSC populations were examined in primary mammary epithelial preparations from 7-week-old MMP3-sufficient and deficient mice as Lin-negative CD24-positive and CD49f–high cells by flow cytometry analysis. The ratio of basal/MaSCs (CD24+/CD49fhi; blue) versus luminal (CD24+/CD49flo; green) cells was significantly decreased in MMP3-null mice; data are represented as mean ± SEM. n=4; *p<0.05.

(B) MECs from MMP3-null mice have a reduced ability to form mammospheres. Representative DIC images are shown; scale bar represents 100 µm. Bar graph depicts the average number of spheres per well seeded with 1,000 MECs; results from 3 independent experiments are shown. Data is shown as mean ± SEM. *p<0.05.

(C–D) MECs from WT and MMP3-null mice (5,000 cells per well) were subjected to the mammosphere assay. Addition of Wnt3a (100 ng/ml) to MMP3-null MECs increased sphere forming potential to the level of WT MECs (C). Similarly, knockdown of Wnt5b (SH1 and SH2) significantly rescued mammosphere formation of MMP3-null MECs compared to Scramble control (D). Data are pooled from two independent experiments. *p<0.05.

(E) Mammary gland reconstituting activity of WT and MMP3-null MECs was determined by limiting dilution transplants (10,000/1,000/100 cells). Cut-off for positive reconstitution was 20% of mammary fat pad filling. Reconstitution efficiencies and calculated stem cell frequencies of MECs from WT and MMP3−/− mice are listed in the table. Data are pooled from 2 independent experiments.

(F) Model of MMP3 as a stroma and basal cell-derived modulator of epithelial homeostasis in the MG. Basal stem cells are stimulated by canonical Wnt ligands such as Wnt1 or Wnt2. Wnt5b functions as an inhibitor of canonical Wnt signaling and interferes with mammary epithelial outgrowth. MMP3 produced in the vicinity of mammary epithelial ducts binds and inactivates Wnt5b leading to increased canonical Wnt signaling and expansion of basal/stem-like epithelial cells.

Also see Figure S6.