Bioengineering an electro-mechanically functional miniature ventricular heart chamber from human pluripotent stem cells

Abstract

Tissue engineers and stem cell biologists have made exciting progress toward creating simplified models of human heart muscles or aligned monolayers to help bridge a longstanding gap between experimental animals and clinical trials. However, no existing human in vitro systems provide the direct measures of cardiac performance as a pump. Here, we developed a next-generation in vitro biomimetic model of pumping human heart chamber, and demonstrated its capability for pharmaceutical testing. From human pluripotent stem cell (hPSC)-derived ventricular cardiomyocytes (hvCM) embedded in collagen-based extracellular matrix hydrogel, we engineered a three-dimensional (3D) electro-mechanically coupled, fluid-ejecting miniature human ventricle-like cardiac organoid chamber (hvCOC). Structural characterization showed organized sarcomeres with myofibrillar microstructures. Transcript and RNA-seq analyses revealed upregulation of key Ca-handling, ion channel, and cardiac-specific proteins in hvCOC compared to lower-order 2D and 3D cultures of the same constituent cells. Clinically-important, physiologically complex contractile parameters such as ejection fraction, developed pressure, and stroke work, as well as electrophysiological properties including action potential and conduction velocity were measured: hvCOC displayed key molecular and physiological characteristics of the native ventricle, and showed expected mechanical and electrophysiological responses to a range of pharmacological interventions (including positive and negative inotropes). We conclude that such "human-heart-in-a-jar" technology could facilitate the drug discovery process by providing human-specific preclinical data during early stage drug development.

Human Cardiac Ventricular‐Like Organoid Chambers and Tissue Strips From Pluripotent Stem Cells as a Two‐Tiered Assay for Inotropic Responses

“…This is likely due to the immature contractile machinery in the human embryonic stem cell‐derived cardiomyocytes (hESC‐CMs) that were used to fabricate the hvCTS, although stronger contractile function and more advanced maturation have been demonstrated more recently in some studies, highlighting the rapid advances in the field. Interestingly, we have recently demonstrated that higher order 3‐D engineered tissues in the form of hvCOC exhibit advanced maturity in terms of their mechanical function and transcriptome . Indeed, when tested with the beta‐agonist isoproterenol, hvCOC showed a more robust increase in response (up to 181% of baseline in hvCOC stroke work vs. 116% in hvCTS‐developed force), approaching the relative increases observed in native healthy human myocardium ( Table S4).…”

“…Moreover, a number of similar screening platforms have been reported to display weak or null inotropic responses, particularly to agonists of the beta‐adrenergic system due to an immature beta‐adrenergic/3',5'‐cyclic adenosine monophosphate system . By contrast, we recently reported that fluid‐ejecting 3‐D human ventricular‐like cardiac organoid chambers (hvCOC), which recapitulate physiologically complex behaviors such as pressure‐volume relationships, stroke work, and cardiac output, also exert pro maturation signals that were accompanied by enhanced positive inotropy …”

“…This was further accompanied by a leftward shift of the concentration‐response curve indicating an enhanced sensitivity primarily due to its calcium‐sensitizing effect rather than its inhibitory effect on phosphodiesterase 3 suggested in some reports, as phosphodiesterase 3, which regulates cardiac contractility, is expressed in low levels in the hvCOC as revealed from our RNA‐seq data ( Figure S5). This agrees with our finding that the non specific phosphodiesterase inhibitor caffeine exerted a positive inotropic effect in hvCTS but not hvCOC (data not shown). In addition to estimated drug potency values that are closer to published clinical values, contractile parameters such as cardiac output, ejection fraction, developed pressure, and stroke work can be uniquely recorded only with the hvCOC assay, allowing the relative changes of these important parameters that are familiar to physiologists and clinicians to be interpreted more directly.…”

“…While these simpler models offer improvements as a first level of screening, they cannot capture physiologically complex multi cellular or tissue‐level phenomena. For instance, single‐cell electrical defects such as action potential prolongation do not necessarily degenerate into life‐threatening arrhythmic reentrant events, which are by definition multi cellular in nature; as for contractility, shortening of individual cells does not directly translate to cardiac muscle force and pressure generation. Furthermore, three‐dimensional (3‐D) milieus that carry key pro maturation signals are not recapitulated with single cells or disorganized clusters …”

Stem Cell Therapy in Heart Diseases – Cell Types, Mechanisms and Improvement Strategies

“…Although designing whole human hearts for transplantation still remains a long way off, there are various immidiate applications for engineered 3-dimensional cardiac tissues. In particular, they can be used for pharmaceutical drug testing and screening or as a model system to better understand the processes regulating cardiac development [451,457,458]. Moreover, the possibility to generate individual iPSC lines promotes the establishment of patient-specific disease models to recapitulate the underlying pathophysiological mechanisms.…”