Afterload promotes maturation of human induced pluripotent stem cell derived cardiomyocytes in engineered heart tissues. (May 2018)

• Record Type: Journal Article
• Authors: Leonard, Andrea; Bertero, Alessandro; Powers, Joseph D.; Beussman, Kevin M.; Bhandari, Shiv; Regnier, Michael; Murry, Charles E.; Sniadecki, Nathan J.
• Is Part Of: Journal of molecular and cellular cardiology. Volume 118(2018)
• Page Start: 147
• Page End: 158
• Publication Date: 2018-05
• Subjects: Human induced pluripotent stem cell-derived cardiomyocytes -- Cardiac maturation -- Engineered heart tissue -- Afterload -- Hypertrophy; hiPSC-CM human induced pluripotent stem cell-derived cardiomyocyte -- EHT engineered heart tissue -- PDMS polydimethylsiloxane -- PLA polylactic acid -- RT-qPCR real time quantitative reverse transcription polymerase chain reaction; Cardiology -- Periodicals; Heart Diseases -- Periodicals; Molecular Biology -- Periodicals; Cardiologie -- Périodiques; Cardiology; Electronic journals; Periodicals; 616.12
• DOI: 10.1016/j.yjmcc.2018.03.016
• Languages: English
• ISSNs: 0022-2828

Abstract

Abstract: Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) grown in engineered heart tissue (EHT) can be used for drug screening, disease modeling, and heart repair. However, the immaturity of hiPSC-CMs currently limits their use. Because mechanical loading increases during development and facilitates cardiac maturation, we hypothesized that afterload would promote maturation of EHTs. To test this we developed a system in which EHTs are suspended between a rigid post and a flexible one, whose resistance to contraction can be modulated by applying braces of varying length. These braces allow us to adjust afterload conditions over two orders of magnitude by increasing the flexible post resistance from 0.09 up to 9.2 μN/μm. After three weeks in culture, optical tracking of post deflections revealed that auxotonic twitch forces increased in correlation with the degree of afterload, whereas twitch velocities decreased with afterload. Consequently, the power and work of the EHTs were maximal under intermediate afterloads. When studied isometrically, the inotropy of EHTs increased with afterload up to an intermediate resistance (0.45 μN/μm) and then plateaued. Applied afterload increased sarcomere length, cardiomyocyte area and elongation, which are hallmarks of maturation. Furthermore, progressively increasing the level of afterload led to improved calcium handling, increased expression of several key markers of cardiac maturation, including a shift from fetal to adult ventricular myosin heavy chain isoforms. However, at the highest afterload condition, markers of pathological hypertrophy and fibrosis were also upregulated, although the bulk tissue stiffness remained the same for all levels of applied afterload tested. Together, our results indicate that application of moderate afterloads can substantially improve the maturation of hiPSC-CMs in EHTs, while high afterload conditions may mimic certain aspects of human cardiac pathology resulting from elevated mechanical overload. Graphical abstract: Highlights: Developed an adjustable afterload platform for human engineered heart tissues (EHTs). Auxotonic contractile force of EHTs increases with degree of afterload. Increasing afterload enhances functional maturation of EHTs. Increasing afterload increases expression of cardiac maturation genes.