Cardiac spheroids consisting of hiPSC-derived Cardiomyocytes, Endothelial cells, Cardiac fibroblasts and Monocytes for the modulation of systolic and diastolic dysfunctions in vitro

Abstract

Diastolic dysfunctions, like heart failure with preserved ejection fraction (HFpEF), are becoming increasingly prevalent worldwide, which is only expected to increase in the coming decades. During HFpEF, comorbidities such as obesity, hypertension and type 2 diabetes result in a metabolic shift paired with an increase in systemic inflammation, ultimately leading to impaired heart relaxation and diastolic dysfunction. Currently, there are no effective treatments for diastolic dysfunctions, and a lack of suitable model systems greatly hampers the generation of novel treatment options. The generation of 3D cardiac spheroids generated from human induced pluripotent stem cells (hiPSCs) allows disease modelling and patient specific drug screening in vitro, showing great potential in the search for diastolic dysfunction treatments. However, all established 3D model systems exclude immune cells like monocytes (MCs) and macrophages, which play important roles in the onset and progression of HFpEF. In this report, I present a novel in vitro model for diastolic dysfunction using cardiac spheroids generated from isogenic hiPSC-derived cardiomyocytes (CMs), cardiac fibroblasts (CFs), endothelial cells (ECs) and MCs. These cardiac spheroids can be generated in a time-efficient manner and are easily upscalable. A diastolic dysfunction model was then created via treatment with TNF-α, glucose or a combination of the two, mimicking systemic inflammation and hyperglycaemia. Additionally, a systolic dysfunction model was created where myocardial infarction (MI) was mimicked by culturing the cardiac spheroids under hypoxic conditions for 6 hours followed by reperfusion. Video analyses of the cardiac spheroids before and after treatment revealed that treatment with TNF-α + glucose resulted in a decrease in contraction amplitude and relaxation time (diastole) in the 4CT cardiac spheroids, but not in the 3CT spheroids, while the contraction time (systole) remained stable, whereas no distinct differences could be distinguished in the systolic dysfunction model. These observations suggest that the 4CT spheroids, where the MCs are present, are more suitable for the in vitro modelling of diastolic dysfunction compared to 3CT spheroids.