Melt Electrowriting Allows Tailored Microstructural and Mechanical Design of Scaffolds to Advance Functional Human Myocardial Tissue Formation

Engineering native-like myocardial muscle, recapitulating its fibrillar organization and mechanical behavior is still a challenge. This study reports the rational design and fabrication of ultrastretchable microfiber scaffolds with controlled hexagonal microstructures via melt electrowriting (MEW). The resulting structures exhibit large biaxial deformations, up to 40% strain, and an unprecedented compliance, delivering up to 40 times more elastic energy than rudimentary MEW fiber scaffolds. Importantly, when human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CM) are encapsulated in a collagen-based hydrogel and seeded on these microstructured and mechanically tailored fiber scaffolds, they show an increase in beating rate (1.5-fold), enhanced cell alignment, sarcomere content and organization as well as an increase in cardiac maturation-related marker expression (Cx43 1.8-fold, cardiac Actin 1.5-fold, SERCA2a 2.5-fold, KCNJ2 1.5-fold, and PPARGC1a 3.6-fold), indicative of enhanced iPSC-CM maturation, as compared to rudimentary fiber scaffolds. By combining these novel fiber scaffolds with clinically relevant human iPSC-CMs, a heart patch that allows further maturation of contractile myocytes for cardiac tissue engineering is generated. Moreover, the designed scaffold allows successful shape recovery after epicardial delivery on a beating porcine heart, without negative effects on the engineered construct and iPSC-CM viability.