Fig. 1.

A self-generated and binary adhesive interaction directs cell positioning in the mammary epithelium. (A) Self-organization of two initially disordered populations of cells (Center) into spatially ordered tissues. In the mammary gland, the correct architecture (Right) can go on to polarize and form a lumen. (B) Self-organization of fourth-passage primary human mammary epithelial cells in agarose (Left) and Matrigel (Right) after 24 h. In Matrigel, the reconstituted microtissue can also polarize and form a lumen over an additional 72 h (MEP, red, keratin-14/K14; LEP, green, keratin-19/K19; blue, DAPI/nuclei). (C) Experiments as in B but with MEP and LEP stained before self-organization with CellTracker Red (CTR) and CellTracker Green (CTG), respectively. (Insets) Average intensity profiles under each condition (n = 30). (D) Frequency of indicated tissue architectures for experiments in C (n > 235). (E) Representative images and average intensity plots of CellTracker-labeled MEP and LEP self-organized in Col1-functionalized agarose (n = 30) and unfunctionalized PDMS microwells (n = 20). (F) Conceptual model for self-organization by a self-generated adhesive interaction at the tissue–ECM boundary. (Inset) An image of MEP on an unfunctionalized PDMS surface (dotted line, PDMS; yellow, fibronectin-1; red, actin; blue, nuclei). (G) Representative images of cell doublets and XZ sections of single cells after 4 h on Matrigel-coated substrate (green, CTG; red, CTR; purple, QD605). (H) Distribution of measured contact angles at all interfaces (n > 42). (I) Representative images of aggregates of homogeneous MEP and LEP after 12 h in agarose wells. (J) Aggregates prepared as in G but subsequently transferred to Matrigel-coated glass for 12 h (green, K19; red, K14). Error bars are SD. (Scale bars, 10 µm.)