title: The role of non-myocytes in drug-induced cardiovascular toxicity
Creators: name: Ravenscroft, Stephanie
Publisher: name: University of Liverpool Repository
Year: 2015

description: Cardiovascular toxicity is a leading cause of drug attrition at the preclinical and clinical stages of drug development. The specific mechanisms of drug-induced cardiovascular toxicities, however, are not well understood and can occur via direct interactions of the drug with cardiomyocytes or indirectly through interactions with other components of the cardiovascular system. Indirect drug effects can target non-cardiomyocyte cells such as fibroblasts, macrophages, vascular smooth muscle cells and endothelial cells. Evidence suggests interactions between these cell types are essential to the metabolism, growth, contractile performance and rhythmicity of the myocardium (Brutsaert, 2003). Preclinical and clinical drug safety tests primarily focus on cardiomyocytes, ignoring the other cellular components of the myocardium. High content biology in combination with ATP content as a measure of cytotoxicity was used to assess the sensitivities of endothelial and fibroblast cells from different vascular beds to known structural cardiotoxins. This assay principle has previously been successful in the detection of structural cardiotoxicity in human embryonic stem cell derived cardiomyocytes (hESC-CM’s) (Pointon et al., 2013). The endothelial cells displayed no significant difference in their compound responses, while the fibroblasts showed variation; imatinib was more potent in the cardiac fibroblasts and lapatinib more potent in the dermal fibroblasts. When the sensitivities of the cells from the myocardium (human cardiac fibroblasts (hCFs), human cardiac microvascular endothelial cells (hCMECs) and hESC-CMs) were globally compared the non-myocytes were sensitive to structural cardiotoxicity at the acute time point of 6 hour (h), whereas the hESC-CMs display toxicity only after 72 h. The conclusions from this work are that non-myocyte cells play a role in drug-induced cardiovascular toxicity since early sensitivity is displayed, however current in vitro models lack the complexity required to investigate the translation of this in vivo. Multiple types of cardiac microtissue models were developed and their responses to reference structural cardiotoxins and inotropes evaluated using ATP content and video-based edge monitoring of contractility, respectively. Compound responses highlighted the promotion of maturity in the cardiac tri-cultured microtissue. Further investigations into gene expression and calcium (Ca2+) handling suggested SR function and Ca2+ handling maturity had been promoted and that the ca2+ handling protein S100A1 plays a critical role in this maturity. These findings show adult cardiac non-myocyte cells can be used to promote contractile maturity of hESC-CM’s in vitro when co-cultured as a three dimensional (3D) microtissue. The induction of maturity was very much multi-parameter dependent requiring a) both non-myocyte cell types, b) cells of cardiac origin and c) a 3D culture environment. More advanced human relevant in vitro models that better reconstitute the in vivo cellular physiology of the heart could allow improved in vitro to in vivo correlation in future drug safety screens.