Epithelial tissues respond to mechanical stimulation. This feature plays a part in their role of protecting underlying tissues/organs, shaping them during development, and restoring confluency during regeneration. Accumulating evidence in epithelial systems show dynamic patterns of cellular contraction and expansion in response to mechanical stimuli. However, the mechanisms involved in mechano-sensation and leading to actuation are not fully understood. In addition, the interplay between the variable response types (stiffening and even contracting, softening and yield, remodeling, and growth) is currently unknown. A key strategy to map and study these trigger-responses is to expose epithelia to controlled mechanical stimulation, and measure the developing internal stresses.

The main experimental challenge is to perturb the tissue with physiologically-relevant force, length, and time scales, while allowing the physiologically-relevant dynamic response to be seen (considering time delays, boundary conditions, and the variability of possible responses). 

Some exciting techniques have been developed to address these challenges for different systems, in vitro and in vivo. These include force application using direct contact to a tissue or substrate (e.g. via indenters, aspiration, AFM, rheometers), using light (optical tweezers), magnetic fields (extra/intra cellular magnetic beads/particles), or growth confinement. Strain-measurement and force-inference tools may include: TFM, laser ablation, birefringence, FRET, “passive cells” (droplets or soft beads) integrated and strained in the tissue, and force-inference from cell shapes. 

In this collection, we will bring a scope of techniques in the field, that can be used to investigate the role of mechanics in epithelium function, from molecular, to cellular, and to tissue levels.