Proximal deposition of collagen IV by fibroblasts contributes to basement membrane formation by colon epithelial cells in vitro.

The basement membrane (BM) underlying epithelial tissue is a thin layer of extracellular matrix that governs tissue integrity and function. Epithelial BMs are generally assembled using BM components secreted from two origins: epithelium and stroma. Although de novo BM formation involves self-assembly processes of large proteins, it remains unclear how stroma-derived macromolecules are transported and assembled, specifically in the BM region.