Spatial patterning of endothelial cells and vascular network formation using ultrasound standing wave fields

The spatial organization of cells is essential for proper tissue assembly and organ function. Thus, successful engineering of complex tissues and organs requires methods to control cell organization in three dimensions. In particular, technologies that facilitate endothelial cell alignment and vascular network formation in three-dimensional tissue constructs would provide a means to supply essential oxygen and nutrients to newly forming tissue. Acoustic radiation forces associated with ultrasound standing wave fields can rapidly and non-invasively organize cells into distinct multicellular planar bands within three-dimensional collagen gels. Results presented herein demonstrate that the spatial pattern of endothelial cells within three-dimensional collagen gels can be controlled by design of acoustic parameters of the sound field. Different ultrasound standing wave field exposure parameters were used to organize endothelial cells into either loosely aggregated or densely packed planar bands. The rate of vessel formation and the morphology of the resulting endothelial cell networks were affected by the initial density of the ultrasound-induced planar bands of cells. Ultrasound standing wave fields provide a rapid, non-invasive approach to pattern cells in three-dimensions and direct vascular network formation and morphology within engineered tissue constructs.