Heart-on-a-chip as biomimetic platform for cardiac physiology and drug toxicity testing

Abstract

[eng] The drug development process is marred by lengthy duration and high expense, primarily attributed to the substantial failure rates observed in clinical trials, accounting for about 90% of drug candidates. These failures impose a considerable financial burden, constituting 60% of total research and development (R&D) costs. Notably, cardiotoxicity, a prevalent side effect associated with many pharmacologically active drugs, stands as a major cause for drug withdrawals due to its potential to induce severe cardiovascular complications such as cardiomyopathy, arrhythmias, QT prolongation, pericarditis, and myocarditis. The treatment of these complications often involves lifelong medication or surgeries, significantly impacting the patients´ quality of life. Consequently, assessing the risk of drug-induced cardiotoxicity has become an integral aspect of standard preclinical evaluations for new chemical compounds. While recent strides in stem cell technology and tissue engineering have provided valuable tools for creating more relevant in vitro human cardiac models, achieving realistic results necessitates the replication of the dynamic physiological microenvironment—an intricate challenge with traditional 2D cultures. Despite their ability to recreate certain aspects of cardiac physiology, existing cardiac tissue models are hindered by large sizes (~1cm thickness) and less physiologically accurate drug administration methods, rendering them inefficient for drug toxicity testing. Consequently, there is an urgent need for the development of in vitro drug-testing platforms capable of accurately replicating the physiological and functional characteristics of the human heart.

Organ-on-a-chip technology is an emerging field that combines tissue engineering and microfluidic technologies to model functional organ units at a microscale level. The heart-on-a-chip (HOC) technology, specifically tailored to replicate vital biological and physiological parameters of cardiac tissue, has recently emerged as a promising approach for expediting drug toxicity testing.

In the frame of our work, we have established a HOC platform seamlessly integrating various cardiac cell types, including cardiomyocytes (CMs), cardiac fibroblasts (CFs), and endothelial cells (ECs), designed to mimic the anatomical structure of cardiac tissue. Our study successfully demonstrated the differentiation of all three cell types from the same human pluripotent stem cell line, laying the groundwork for the integration of multiple functional components. Each cell type was thoroughly characterized, confirming their suitability for integration into the platform. The resulting microtissue within the HOC presented a sufficient viability after 7 days of culture under perfusion.

To functionally assess the system, we applied isoproterenol through the bottom channel, where ECs were seeded to replicate the native route of drug delivery to CMs. Significantly, CMs responded in a physiological manner to the inotropic drug, exhibiting an increased beating rate. Furthermore, our study highlighted the crucial role of ECs in the system. When subjected to the well-known cardiotoxic drug doxorubicin, we demonstrated that ECs play a protective role for CMs. Additionally, co-culture conditions with ECs were found to enhance the maturation level of CMs, emphasizing the

intricate interplay between cell types. The outcomes of our research underscore the importance of incorporating a vascular layer in in vitro cardiac models for drug testing. The HOC platform presented its potential for cardiovascular drug evaluation, providing a more in vivo-like microenvironment. In summary, our study highlights the relevance of the established HOC system in advancing cardiac research and drug development.