Background

Cells isolated from animal or human hearts by enzymatic dissociation have provided fundamental insights into the electrophysiology, contractile function, and transcriptional profiles of cardiomyocytes (Liu et al., 2021). However, cells cultured in 2D lack the native environment of the 3D myocardium, which includes intra- and intercellular interactions and syncytial properties that are determinant factors in studying cells, genes, and drug modulations in cardiac pathologies. It is also known that functional and structural preservation of native myocardial tissue ex vivo is dependent on the application of both mechanical preload and electrical stimulation (Brandenburger et al. 2012; Watson et al., 2017; Perbellini et al., 2018; Qiao et al., 2019). Recently, Fischer et al. (2019) established and commercialized a biomimetic ex vivo culture system taking these parameters into account to maintain intact native human myocardial slices in culture for up to four months (Fischer et al., 2019; www.invitrosys.com). This novel technology enables human disease modeling with high temporal and spatial resolution in assessing cellular behavior after pharmacologic or genetic interventions. A drawback of this method is that human tissue is not readily available, with samples generally originating from end-stage heart failure patients with a wide range of comorbidities. Moreover, the patients’ age, genetic background, and medication can be confounding factors during ex vivo analyses. To enable standardized investigational studies, we adapted this system to the culture of non-human primate (NHP) heart slices.

NHP hearts are an excellent surrogate to address basic research questions due to their genetic, metabolic, and physiologic similarities to humans and the ability to control diet, environment, and breeding (Cox et al. 2017). As described in the step-by-step protocol below, left ventricular transmural sections of native NHP hearts are cut into thin tissue slices (300 μm) that are subsequently subjected to physiological preload and electrical stimulation. Under biomimetic culture conditions, a continuous readout of contractile performance and electrophysiologic behavior such as excitability, force-frequency relationship, and effective refractory period can be reached for up to three weeks. Furthermore, as we recently reported, this system can be used as a platform to study critical steps of cardiac regeneration processes in single-cell resolution demonstrating that time- and resource-consuming in vivo studies in animals can be partially bridged (Poch et al. 2022).