Controlling Cardiomyocytes Contractility With Gradient Melt Electrowritten Scaffolds

Background The myocardium has a complex gradient tissue structure which is critical for its functionality. Replicating this remains a challenge for successful cardiac tissue engineering. Melt electrowriting (MEW) is an advanced 3D printing technology capable of fabricating highly precise fibrous scaffolds with complex architectures. Here we create gradient MEW scaffolds and investigate their ability to regulate cardiomyocyte contraction within a single scaffold. Methods Multi-directional gradient porosities were programmed using a custom g-code generator into three scaffold patterns (rectangles, diamonds, and serpentines) with three different gradient magnitudes. MEW was then used to fabricate these into 20x20 mm fibrous scaffolds from polycaprolactone, each with 5 layers. Scaffolds were tested under equibiaxial tension to characterise their tensile mechanical properties. Strain mapping quantified the effect of gradient architectures on the distribution of localised strains. Human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) were seeded on scaffolds for 2 weeks to quantify the effect of gradient scaffolds on sarcomere content and orientation (immunofluorescence for cardiac α-actinin), and cardiomyocyte contraction. Results Strain mapping revealed complex variations in the localised deformation of scaffolds under equibiaxial tension. Local strain magnitude and direction was controllable by varying the gradient type and magnitude. iPSC-CMs contraction magnitude and direction were also regulated by scaffold architecture, with larger contractions in regions of lower scaffold stiffness. Conclusion This work provides a powerful platform to control cardiomyocyte contraction using gradient MEW scaffolds, bringing a step closer the creation of functional myocardial tissue-engineered constructs.