Basement Membrane Components Define the Microenvironment of Aggregated Fibroblasts in the Skin and Support Their Aggregation In Vitro

The study investigates the role of the basement membrane (BM)-like extracellular matrix (ECM) in the aggregation and function of dermal papilla (DP) cells, which are crucial for hair follicle development and regeneration. The researchers found that DP cells are embedded in a BM-like ECM, characterized by a diffuse, mesh-like structure with minimal cell-cell adhesion, rather than in a conventional interstitial fibrillar ECM like collagen I. This BM-like ECM supports DP cell aggregation through interactions with specific laminin isoforms via integrin α7β1, resulting in weak adhesiveness. In vitro experiments demonstrated that a BM extract-based matrix, Matrigel, supports the formation and maintenance of DP aggregates and enhances DP-marker gene expression, whereas collagen I gel leads to their dispersion. These findings suggest that a BM-like ECM niche is essential for maintaining DP cohesion.