Fig. 1: Schematic of experimental procedures.

a, b Different cell seeding densities were used to generate macro-pellets or micro-pellets of specific size in deep-well plates or Microwell-mesh plates, respectively. Micro-pellets were retained in discrete microwells by the nylon mesh bonded over the microwell openings (see Supplementary Movie 1). Retention by the mesh enabled long-term micro-pellet culture, including multiple medium exchanges. c Diffusion gradients are reduced in smaller diameter micro-pellets relative to larger diameter macro-pellets16,17. d Cultures were carried out for 21 days total, with blue lines representing culture days with TGF-β1 in the medium, and gray lines representing culture days without TGF-β1 in the medium.