Hydrogel polymer density and RGD adhesive ligand regulate epithelial morphogenesis in Caco-2 cells. Fluorescence microscopy images of Caco-2 cells grown within PEG-4MAL hydrogels for 10 d. Bar, 100 µm. Cysts were labeled with rhodamine phalloidin (filamentous actin) and Hoechst 3342 (DNA). Cyst formation, lumen formation, and polarization required RGD adhesive peptide. Hydrogel polymer density influences the size of the resulting epithelial cyst.