A simple technique for the arrangement of multiple types of cells into three-dimensional (3D), tissue-like structures is reported in Nature Communications this week. The method, which employs hydrogel moulds, does not require sophisticated laboratory equipment and works even with ‘fragile’ cells, such as stem cells.

Artificially engineered tissues may be useful for regenerative therapies but their 3D architecture is difficult to control, yet crucial for maintaining tissue function. Sangeeta Bhatia and her team grow cells on a patterned surface, which they overlay with a hydrogel. The gel is then removed, exposing a relief that precisely mimics the structural features of the first cell population. A second cell layer, grown on the relief, can then be combined with the first one, yielding a 3D hydrogel that contains multiple micropatterned cellular compartments. The team use this technique, termed “Intaglio-Void/Embed-Relief Topographic (InVERT) molding”, to investigate how the function of stem-cell-derived liver cells is affected by the proximity of surrounding cells. They further show that these tissues can be transplanted and maintain basic functions in mice for several weeks.