Identification of cell adhesion molecules for the maturation of engineered heart tissue

Abstract Background Engineered cardiac tissue (ECT) utilizing human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) is anticipated to function as a translational in vitro model. However, hiPSC-CMs display phenotypes indicative of immaturity, and the structural organization of ECT composed of hiPSC-CMs is insuficient when compared to that of mature adult hearts. Although the mechanisms for hiPSC-CMs maturation have been reported, little is known about the mechanisms regulating the formation of in vitro tissue such as ECT. Cell adhesion molecules play important roles in heart formation in vivo through cell-cell interactions. However, specific cell adhesion molecules responsible for tissue structure formation in in vitro tissue models, such as ECTs, have not been identified. We hypothesize that cell adhesion molecules, which regulate cell-cell attachment, are crucial for in vitro tissue formation. Purpose This study aims to identify the key cell adhesion molecules involved in cell-cell interaction and assess the effects of their expression on hiPSC-CMs and EHT functions. Methods and Results We developed a cell attachment assay to evaluate the attachment ability of hiPCS-CMs and discovered that hiPSC-CMs produced via embryoid body method (EB-hiPSC-CMs) exhibited a higher attachment ability than those produced by monolayer method (Mono-hiPSC-CMs). Further analysis revealed no significant difference in anoikis sensitivity between EB-hiPSC-CMs and Mono-hiPSC-CMs, suggesting that the observed difference in attachment ability were due to differencies in cell adhesion efficiency between hiPSC-CMs generated by two methods. Moreover, RNA-seq analysis identified nine cell adhesion molecule genes that were highly expressed in EB-hiPSC-CMs. We identified the cell adhesion molecules responsible for the attachment ability of hiPSC-CMs by knockdown and over-expression experiments. Moreover, over-expression experiments using adeno-associated virus (AAV) demonstrate that hiPSC-CMs with overexpression of a cell adhesion molecule improved calcium handling and increased propagation speed, and ECTs with overexpression of a cell adhesion molecule showed enhanced sarcomere alignment and sarcomere length compared to controls. Conclusion(s) We observed differences in attachment ability between hiPSC-CMs generated by two differentiation methods. Transcriptome analysis of these hiPSC-CMs identified key cell adhesion molecules that regulate cell-cell attachment ability of hiPSC-CMs. Furthermore, increment of attachment ability of hiPSC-CMs by overexpression of a cell adhesion molecule enhanced hiPSC-CMs and ECT functions.