Basement membrane sets the timescale of tissue mechanical memory

The basement membrane (BM) is a specialised extracellular matrix tightly tethered to epithelial tissues. While the viscoelastic response of epithelial cells to external deformation has been widely studied, the dynamic mechanical role of its underlying BM remains poorly understood. This is mainly due to its thin, dense, non-fibrillar structure and limited number of model systems that allow live fluorescent imaging of the BM components. Using the Drosophila wing disc, we investigate the BM’s response to sustained deformation and find that the tissue retains memory of its shape for up to four hours, enabled by the BM’s initial elasticity. However, prolonged deformation leads to BM network rearrangement and loss of mechanical memory, resulting in permanent shape change. Our findings reveal that the BM sets the long-term viscoelastic timescale of epithelial tissues which plays a critical role in maintaining tissue architecture under mechanical stress.