Cardiac Tissues with Complex, Controlled Anisotropy

Can we create cardiac tissues that faithfully mimic the architecture of the myocardium? The Soft Robotics lab is on a mission to build cardiac tissue that features controllable cellular alignment to effectively integrate in the heart.

Filamented Light Biofabrication with Cardiomyocytes — Aligned and contractile cardiac tissues are fabricated at a physiological cell density using ﬁlamented light biofabrication. A) Schematic illus- tration showing cardiac tissue biofabrication, cell culture, and electrical stimulation. B) Schematic illustration of ﬁlamented light biofabrication showing cell-induced light scattering, cell alignment, microstructure formation, and cardiomyocyte (red) and ﬁbroblast (yellow) alignment. Hydrogel microstruc- tures form when the laser speckle pattern is nonlinearly ampliﬁed (self-focussing) due to photoink crosslinking, resulting in microscopic waveguides. C) Immunoﬂuorescence staining of cells in a biomimetic tri-layered myocardium tissue (multidirectional light) and unidirectionally irradiated tissue (directional light). D) Optical ﬂow contractility analysis on a tissue created with multidirectional ﬁlamented light biofabrication.

Introduction

Creating three-dimensional cardiac tissues that closely resemble native myocardium is a key objective in cardiac tissue engineering. The ultimate aim is to replicate the intricate structure and function of the native myocardium, which comprises three aligned layers of cardiac muscle. These layers transition from a helical orientation in the endocardium to the epicardium, resulting in efficient torsional contraction. Thus, a primary objective in cardiac tissue engineering is controlling the cardiomyocyte alignment, which in turns affect cardiomyocyte maturity. Successfully aligning cardiomyocytes in 3D is necessary to create more functional tissues for cardiac repair.

Our solution

We used multidirectional filamented light projection to create 3D cardiac constructs that feature controlled, multidirectional cellular alignment and contractile orientations, including unidirectional and twisting movements. This technique allows us high-density cellular constructs with uniaxial contractility and high degree of tissue maturity as indicated by enhanced intercellular communication. Moreover, by partially mitigating cell-induced light absorption, we managed to produce larger tissues displaying multidirectional cellular alignment, such as multiple-layered myocardium-like tissue and constructs exhibiting torsional contraction.

Applications

With this work, we showed that it is possible to generate cell-aligning microfilaments into high-cell density, optically tuned hydrogels. Our product was contractile cardiac tissues with controlled and complex cellular alignment, which showcases a novel, rapid strategy to fabricate aligned cardiac tissues with applications in regenerative medicine and biohybrid robotics. The proposed method can however find applications in other areas of tissue engineering where controlling tissue anisotropy is important.