Biomimetic Cultivation of Atrial Tissue Slices: a Novel Platform for In-Vitro Atrial Arrhythmia Studies

Abstract

Living myocardial slices (LMS) are beating sections of intact human myocardium that maintain 3D microarchitecture and multicellularity, thereby overcoming most limitations of conventional myocardial cell cultures. We introduce a novel method to produce LMS from human atria and apply pacing modalities to bridge the gap between in-vitro and in-vivo atrial arrhythmia studies. Human atrial biopsies from 14 patients undergoing cardiac surgery were dissected to tissue blocks of ~ 1 cm2 and cut to 300 µm thin LMS with a precision-cutting vibratome. LMS were placed in a biomimetic culture chamber, filled with standard cell culture medium, under diastolic preload (1 mN) and continuous electrical stimulation (1000 ms cycle length (CL)), resulting in 60 beating LMS. Atrial LMS refractory period was determined at 192 ± 26 ms. Fixed rate pacing with a CL of 333 ms was applied as atrial tachyarrhythmia (AT) model. This novel state-of-the-art platform for AT research can be used to investigate arrhythmia mechanisms and test novel therapies.

Living myocardial slices: Advancing arrhythmia research

“…The vibratome then produces slices with a thickness of 150-400 µm coming from different layers within the myocardium. In general, vibratome speed should be lowered for atrial tissues in comparison with ventricular tissues, as atrial tissue is more fragile and therefore at higher risk for rupturing on the vibratome (Kang et al, 2016;Amesz et al, 2022). In addition, slices infiltrated with large amounts of fibrous and adipose tissue often show separation of myocardial bundles and are therefore not routinely selected for culture.…”

“…Hence, cardiomyocytes in LMS are wellaligned in a striated fashion and linked by gap junctions, and membrane bound connexins are preserved (Habeler et al, 2009). To date, LMS have been predominantly produced from ventricular specimens, but can also be produced from atrial tissue (Girmatsion et al, 2009;Biliczki et al, 2019;Amesz et al, 2022). In addition, Kang et al (2016) produced slices from the sinoatrial node region and observed automaticity in these LMS.…”

“…For example, mechanical overload can be induced by the application of extra stretch on myocardial tissue, leading to a fibrotic remodelling response (Nunez-Toldra et al, 2022;Pitoulis et al, 2022) associated with cardiac arrhythmias. At the same time, application of programmed electrical stimulation protocols in the cultivation chambers allows for mimicking arrhythmias, e.g., with programmed rapid electrical stimulation or frequent extrasystoles (Figure 2) (Amesz et al, 2022). Furthermore, viral transduction can be established in LMS (Ferrera et al, 2005;Kang et al, 2016;Thomas et al, 2016) for cardiac disease induction and gene therapy (Liu et al, 2020).…”

“…Fischer et al (2019) developed a cultivation chamber with real-time measurement of contractile forces, without having to place the LMS on external force transducers. Such a platform can be used for continuous evaluation of contractile responses to different culture conditions, including tachypacing and induction of arrhythmias (Amesz et al, 2022). Moreover, structural and molecular analyses of LMS further supplement electrophysiological and mechanical assessments of LMS.…”