Hydrogel microwell with pneumatic soft actuator for compression formation of three-dimensional cellular tissue

Three-dimensional cellular tissue reproduces the structure and function similar to the tissues in the body. So far, as a means for the formation and maturation of three-dimensional cellular tissues, various mechanical stimuli have been applied to cells. Compression by mechanical actuators is a popular method for applying mechanical stimulation to cells. However, the use of linear or rotary actuators limits the direction of compressive stimulation to one axis and requires the cell to be adhered to a scaffold for fixation. Here, we propose a method to form three-dimensional cellular tissue cultured by a hydrogel microwell in a pneumatic soft actuator as a hybrid soft actuator. The hydrogel microwell deformed by the pneumatic soft actuator envelopes and three-dimensionally compresses the cells in the hydrogel microwell even shortly after cell seeding due to no need to fix the cells on the scaffold. In this study, ATDC5 cells, which are a mouse chondrogenic progenitor cell line having high activity to compressive stimuli, were cultured to apply enveloping compressive stimulation to the cells. By applying compressive stimulation to the cells in the hydrogel microwell using the pneumatic soft actuator, the formation of cellular tissue was promoted at an early stage before the cells began to adhere to each other. Moreover, the cellular tissue compressed by the pneumatic soft actuator expressed Sox9 and collagen II as well as the control without compressive stimuli. This proposed culture with the pneumatic soft actuator is a promising three-dimensional culture method capable of compressing cells, which can be applied for regenerative medicine and drug screening.