Development of Biomimetic Materials for Enhanced Maturation of Engineered Cardiac Tissue

Abstract

The creation of cardiac tissue constructs holds potential in the development of clinical and diagnostic platforms, including the creation of novel treatments for patients with heart disease and cost-effective platforms for drug discovery. Many materials and techniques have been investigated for use in creating engineered cardiac tissue; however, formation of engineered myocardium in vitro, particularly when derived from pluripotent cell sources, often results in the creation of cardiac tissue or cardiomyocytes with functional properties that are markedly different from the native adult myocardium. The use of biomimetic materials, those materials that emulate one or more properties of native tissue, may be necessary for obtaining cardiac tissue demonstrating physiologically-relevant electrophysiological properties. In this document, the ability of biomimetic materials to drive pluripotent stem cell derived cardiac tissue maturation has been investigated. This document first introduces the overall challenges associated with heart disease and drug discovery, which emphasizes the need for biomimetic material-based solutions. A review on current biomaterial-based methods for treating heart disease, as well as background on work utilizing biomimetic materials for cardiac regeneration is presented, as well as current methods for evaluating functional maturity (with an emphasis on quantifying electrophysiology) of cardiomyocytes and cardiac tissue. Next, the design and implementation of an optical mapping platform for assessing calcium wave velocity and calcium transient duration is presented. This combined macroscopic and microscopic imaging system was capable of capturing optical mapping data from samples ranging 21 to 0.5 mm in size at rates in excess of 500 frames per second. After, a study utilizing biomimetic nitric oxide donor S-nitrosocysteine (CysNO) to direct maturation of stem cell derived cardiomyocytes (SC-CMs) is discussed. Differentiating embryoid bodies treated with CysNO developed greater numbers of faster contracting cardiomyocytes in comparison to controls; dissociated SC-CMs treated with CysNO demonstrated improvement in calcium handling via faster calcium transient velocities and shorter calcium transient durations. Next, a study utilizing the conductive polymer polypyrrole (PPy) is presented which evaluated cardiomyocyte survival and development when grown on the novel material. HL-1 cardiomyocytes cultured on PPy-polycaprolactone (PPy-PCL) films demonstrated greater numbers of connexin-43 positive cells in conjunction with faster calcium transient velocities and shorter calcium transient durations in comparison to cells grown on PCL alone. Finally, the response of SC-CMs differentiated on the surface of the novel PPy-PCL material is reported; PPy-PCL supported the growth and viability of dissociated SC-CMs at a comparable number to PCL alone. Together, these studies provide insight into how novel biomimetic materials can be implemented in the creation of functionally-mature cardiac tissue. Additionally, this work demonstrates how a custom optical mapping apparatus can be adapted to assess cardiac maturation among a gamut of different platforms. The ability to direct and evaluate maturity of differentiating cardiomyocytes contributes to the development of clinical and research platforms for improving treatment of heart disease.