Effects of extracellular S100A4 on branching morphogenesis in primary mouse mammary gland organoids grown in 3D matrigel cultures. (A) Brightfield images of representative organoids, 96 h after addition of 4 μg/ml S100A4 in combination with TGFα, to the culture medium, compared to TGFα alone. (B) Quantification of branching morphogenesis after treatment of the organoids with S100A4 protein in combination with TGFα. The frequency plots illustrate number of buds on the ten largest organoids in each well. Mean number of buds was significantly higher in S100A4 treated compared to control wells (15.1 vs. 11.6) (p<0.01). (C) S100A4 induced MMP-3 mRNA expression from primary mammary gland organoids. qPCR with mouse MMP-3 primers on total RNA from primary mammary gland organoid cultures treated with 4 μg/ml recombinant S100A4 protein for 96 h, compared to pro-GRP as control protein (a protein of same size, with the same his tag, and produced in the same manner as the recombinant S100A4 protein) and vehicle control (PBS). (D) A representative Western gel of medium from primary organoid cultures, stained with anti MMP-3 antibody. The ponceau staining is shown as a loading control. 15 μl from three parallel wells from one experiment was loaded on the gel.