An extracellular matrix niche secreted by epithelial cells drives intestinal organoid formation.

Intestinal organoids have become an important model system in basic and translational research, but their culture typically relies on an ill-defined laminin-rich extracellular matrix (ECM). Using tunable and chemically defined 3D hydrogels, we systematically explored the role of the ECM during murine and human intestinal organoid development. We discovered that without exogenous laminin, stem cells developed into intestinal epithelia with a large proportion of regenerative cells. This population secreted a laminin-rich basement membrane that functioned as a de novo stem cell niche, promoting organoid formation independent of exogenous laminin. We identified ubiquitous expression of laminin chains Lama3, Lamb3, and Lamc2, but Lamb1 and Lamc1 were spatially restricted to the crypt domain. Epithelial-cell-secreted basement membranes extracted from organoids promoted the formation of patterned organoids. Our results highlight the utility of chemically defined matrices for studying ECM biology and pave the way for the replacement of animal-derived matrices in organoid culture.