Fig. 4

CD105^high stroma is a specialized microenvironment for branching morphogenesis of luminal breast epithelial cells. a Primary cultures of purified luminal breast epithelial cells plated at clonal density on confluent feeders of CD26^high (left column) or CD105^high (right column) fibroblasts: phase contrast micrographs of co-cultures twenty days after plating showing branching morphogenesis primarily on CD105^high fibroblasts (a’, b’); dual-color imaging of co-cultures stained with keratin K19 (red) and MUC1 (green). Note the correctly polarized staining pattern and the elaborate structures on CD105^high fibroblasts (c’, d’); low-magnification micrographs of co-cultures ten days after plating and immunoperoxidase staining for keratin K19 (e’, f’); digitalized images of keratin K19-stained epithelial structures (g’, h’). b Quantitative representation of K19-stained morphological structures in multiple recombinant cultures representing eight biopsies showing consistent growth advantage of luminal epithelial cells on CD105^high fibroblasts (red bars) as normalized in each set of samples to structures formed on CD26^high fibroblasts (blue bars) (scale bar = 50 μm (a’, b’); 100 μm (c’, d’); 500 μm (e’-h’))