Development of small, engineered heart tissues and their acute response to implantation

Huethorst, Eline (2022) Development of small, engineered heart tissues and their acute response to implantation. PhD thesis, University of Glasgow.

Abstract

Introduction: Human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) are a great source of human cardiac cells and can be combined with biomaterials to form engineered heart tissues (EHTs). Implantation of EHTs into the myocardium after a myocardial infarction (MI) is a promising strategy to regenerate the scar area. However, the ongoing challenge is the lack of electrical and mechanical coupling of the graft to the host tissue. Moreover, to replace the number of lost cells after an MI, current EHTs are large (cm-scale) and consist of >107 cells, resulting in extremely high costs. Therefore, the aim of this study was to develop a cost-efficient platform based on the implantation of small EHTs (<50,000 hiPSC-CMs) grafted into the rabbit myocardium in vitro, and subsequently to assess the electrophysiological adaptations of the hiPSC-CMs to the surrounding myocardium using of fluorescent indicators. Methods: The EHTs (mm-scale) consisted of commercially available hiPSC-CMs (45.000 cells) seeded on top of a recombinant collagen-like peptide hydrogel (22 kPa; 6 mm diameter; 350 μm thick). Excitation-contraction coupling (ECC) properties of the EHTs were assessed in vitro. Adult male rabbits were euthanized and, subsequently, the heart was excised and placed on a Langendorff rig. EHTs were stained a fluorescent calcium indicator prior to implantation to track their activity. Calcium traces of the EHT and the ECG of the rabbit heart were compared during analysis. Results: Incorporation of fibronectin into the hydrogel improved cell adhesion and resulted in viable EHTs for at least 7 days. EHTs were not able to follow high pacing frequencies comparable to the intrinsic rate of the rabbit heart, most likely because of slower calcium handling. HiPSC-CMs seeded on the hydrogel showed an improved (“twitch”-like) contraction profile in comparison to cells seeded on rigid matrixes that showed a multi-phasic time-course. Once implanted, EHTs were viable for at least 90 min and calcium transients could be recorded for this time, however, there were no signs of electrical coupling during the experiment. Conclusion: With this work, a novel ex vivo platform has been developed to investigate functionality of implanted cells within the myocardium in the acute phase post-implantation. This platform can be used to investigate many factors that might affect the integration and survival of implanted cells during the acute phase in a cost-effective way and is therefore a good intermediate step between in vitro and in vivo experiments.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Cardiovascular & Metabolic Health
• Supervisor's Name: Smith, Prof. Godfrey and Gadegaard, Prof. Nikolaj
• Date of Award: 2022
• Depositing User: Theses Team
• Unique ID: glathesis:2022-82668
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 03 Feb 2022 14:41
• Last Modified: 08 Apr 2022 16:53
• Thesis DOI: 10.5525/gla.thesis.82668
• URI: https://theses.gla.ac.uk/id/eprint/82668

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