The role of endothelial cells in the retinal stem and progenitor cell niche within a 3D engineered hydrogel matrix.

Cell-cell interactions are critical to understanding functional tissues. A number of stem cell populations have been shown to receive key regulatory information from endothelial cells (ECs); however, the role of ECs in the retinal stem and progenitor cell (RSPC) niche has been largely unexplored. To gain greater insight into the role of ECs on RSPC fate, a three-dimensional (3D) co-culture model, incorporating cell-cell interactions, was designed by covalently-modifying agarose hydrogels with growth factors and cell-adhesive peptides in defined volumes. Therein ECs adopted tubular-like morphologies similar to those observed in vivo, but not observed in two-dimensional (2D) cultures. Unexpectedly, ECs inhibited proliferation and differentiation of RSPCs, revealing, for the first time, the possible role of ECs on RSPC fate. This 3D hydrogel scaffold provides a simple, reproducible and versatile method with which to answer biological questions related to the cellular microenvironment.