Fig. 1

Extracellular matrix (ECM) hydrogels enable self-organization and hormone responsiveness of human breast organoids. a Schematic representation of hydrogel assembly. Fibronectin, FBN; laminin, LM; high molecular weight hyaluronan, HA(hMW); low molecular weight hyaluronan, HA(lMW); epidermal growth factor, EGF. b Comparative morphology of human breast tissue in vivo and ex vivo. Representative bright-field images of ex vivo organoid growths after 10 days in Matrigel, polymerized collagen, or ECM hydrogels next to representative bright-field whole-mount images of carmine-stained human breast tissue. c Quantification of outgrowths in Matrigel, collagen, or ECM hydrogels. Frequency of seeded tissue fragments expanding (Freq. Formation) and frequency of expanded outgrowths exhibiting TDLU architecture (Freq. Maturation) from a patient. d Bright-field images of organoid growth after 3 weeks with or without estrogen and progesterone (+EP) treatment. Maturation of ducts and lobules is evident by hollowed lumens (red arrowheads). e Experimental design and representative bright-field images of organoid outgrowths in ECM hydrogels in response to pituitary hormones and recombinant human prolactin (Prl). Bovine pituitary extract was added at seeding (D0) and prolactin at day 14 (D14) (n = 4, 7, and 14, 1 resp). Bottom left images (D13) show representative morphology before treatment with prolactin (D21). f Quantification of lobular volume (arbitrary units, AU) with or without prolactin treatment described in (e). Error bars represent standard error of the mean. Scale bars represent 200 μm. *p < 0.01