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

Abstract

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.

Bottom-up assembly of salivary gland microtissues for assessing myoepithelial cell function

“…With the two types of cells in hand, a flexible, high-throughput 3D culture platform is desirable for the organization of the respective cell types in a well-defined spatial manner. [15] Finally, the complex assemblies should be encapsulated in a permissive and instructive hydrogel matrix that approximates the properties of the connective tissue mesenchyme surrounding the salivary gland. In such heterocellular organoid models, hSMECs should enable the exchange of paracrine and juxtacrine signals, contributing to the proper function of the salivary gland.…”

3D culture models of tissues under tension

“…As a consequence, the cells and the matrix align according to the direction of the principal stresses, which are dictated by the geometry of the tissue (Schell et al, 2016). In other words, cells and matrix are highly uniaxially aligned in tissues anchored to two pillars and randomly organized in equibiaxial hexagonal tissues (Obbink-Huizer et al, 2014;Schell et al, 2016).…”

“…As a consequence, the cells and the matrix align according to the direction of the principal stresses, which are dictated by the geometry of the tissue (Schell et al, 2016). In other words, cells and matrix are highly uniaxially aligned in tissues anchored to two pillars and randomly organized in equibiaxial hexagonal tissues (Obbink-Huizer et al, 2014;Schell et al, 2016). Given that fibroblasts can bind and apply forces to different ECM molecules, fiber alignment is not restricted to the exogenous collagen matrix alone, but also applies to other ECM proteins, such as tenascin-C, collagen type II and fibronectin Schell et al, 2016).…”

“…In other words, cells and matrix are highly uniaxially aligned in tissues anchored to two pillars and randomly organized in equibiaxial hexagonal tissues (Obbink-Huizer et al, 2014;Schell et al, 2016). Given that fibroblasts can bind and apply forces to different ECM molecules, fiber alignment is not restricted to the exogenous collagen matrix alone, but also applies to other ECM proteins, such as tenascin-C, collagen type II and fibronectin Schell et al, 2016). Epithelial cell-cell contact is initiated by engagement of E-cadherin adhesion proteins.…”

Perfused Organ Cell‐Dense Macrotissues Assembled from Prefabricated Living Microtissues

“…Here, we describe the Bio‐Pick, Place, and Perfuse (Bio‐P3), an integrated biofabrication‐bioreactor technology that semiautomatically constructs perfusable macrotissues with 100 million cells at physiological cell density within 2 h. Our approach makes use of prefabricated, modular, scaffold‐free microtissue building parts in customizable geometries with precisely placed holes that act as lumens . The Bio‐P3 grips, aligns, and stacks microtissues vertically onto a perfusable build‐platform.…”