Date of Award
Doctor of Philosophy (PhD)
Translation of novel therapies from bench to bedside is slow and often marred by catastrophic failures that cost lives. This shortcoming in therapy research is the results of the profound disparities between animal and human genetics and physiology, the current paradigm of testing individual therapies in isolation, and the lack of versatile human tissue model for trial and development. This dissertation aims to addresses these issues by developing technology and protocol for multi-parametric imaging and chronic studies of human tissue slices, as well as investigating mechanism of adrenergic influence on cardiac repolarization.
First study examined how arrhythmia is caused and sustained by drugs in presence of sympathetic nervous tone. An increase in QT interval, termed Long QT (LQT), is an arrhythmia causing disorder that can lead to sudden cardiac death, a leading cardiovascular cause of death. Delayed rectifier potassium channels, IKr and IKs, provide crucial repolarizing current in the heart, which when disrupted provide both trigger and substrate for sustained arrhythmia. Despite the majority of LQT is caused by genetic mutation in gene coding for IKs, it plays a minimal role in published data. I investigated the effect of adrenergic modulation on IKr and IKs in coronary perfused left ventricular wedge preparation from donor human hearts. This study elucidated some mechanisms of arrhythmogenesis in LQT patients. Previously paradoxical nature of IKs is also explained. Moreover, the dynamics between IKr and IKs is highlighted.
The ability to rapidly test for both acute and chronic therapy efficacy and cardiotoxicity in an in-vitro human model system would enable more rapid therapy development. I have developed a preclinical platform for validation of new therapies in human heart tissue using organotypic slices isolated from donor and end stage failing hearts. A major advantage of the slices when compared with human iPS-derived cardiomyocytes is that native tissue architecture and extracellular matrix are preserved, thereby allowing investigation of multi-cellular physiology in normal or diseased myocardium. I validated this model used optical mapping of transmembrane potential and calcium transients. Normal human electrophysiology is preserved in slice preparations when compared with intact hearts, including slices obtained from the region of the sinus node. Maintenance of slices during culture, enabling testing the acute and chronic effects of pharmacological, gene, cell, optogenetic, device, and other therapies. This new methodology in human research offers a powerful high-throughput platform for assessing the physiological response of the human heart to disease and novel putative therapies.
Jianmin Cui, Igor R. Efimov
Stacey Rentschler, Kristen Naegle, Richard Schuessler
Available for download on Tuesday, December 15, 2116