Harnessing cellular-derived forces in self-assembled microtissues to control the synthesis and alignment of ECM.

The alignment and blend of extracellular matrix (ECM) proteins give a tissue its specific mechanical properties as well as its physiological function. Various tissue engineering methods have taken purified ECM proteins and aligned them into gels, sponges and threads. Although, each of these methods has created aligned ECM, they have had many limitations including loss of hierarchal collagen structure and poor mechanical performance. Here, we have developed a new method to control ECM synthesis using self-assembled cells. Cells were seeded into custom designed, scaffold-free, micro-molds with fixed obstacles that harnessed and directed cell-mediated stresses. Cells within the microtissue reacted to self-generated tension by aligning, elongating, and synthesizing an ECM whose organization was dictated by the strain field that was set by our micro-mold design. We have shown that through cell selection, we can create tissues with aligned collagen II or aligned elastin. We have also demonstrated that these self-assembled microtissues have mechanical properties in the range of natural tissues and that mold design can be used to further tailor these mechanical properties.