Living myocardial slices: walking the path towards standardization

Cardiovascular disease remains a persistent global health burden, underscoring the necessity for effective therapeutic strategies. Despite significant advances, the ability to mechanistically study human disease and predict clinical outcomes remains limited, especially in complex diseases such as heart failure. This limitation is evident through the continuous high attrition rates in drug development pipelines. To address these challenges and contribute to improved preclinical studies, there is a need for platforms that more accurately recapitulate the human heart. This need increased the interest in living myocardial slices (LMS) - thin sections of the heart of approximately 100-400 μm. LMS retain the native multicellular architecture of the heart and enable extended ex vivo culture. However, as their utilization grows, so does variability in preparation methodologies and readouts. This review provides an overview of differences in sample selection, interspecies variations, intra-cardiac differences, and potential confounding factors. Additionally, we examine culture methods, addressing electrical and mechanical stimulation differences, and medium compositions. Our review concludes by highlighting the current limitations of LMS research and offers guidelines for standardization and future applications. The ultimate aim of this review is to serve as a resource for researchers working with LMS and for those entering this field. By presenting the landscape of methodological considerations, we aim to facilitate informed decision-making in study design and execution. We advocate for accurate reporting of methodologies to promote reproducibility and comparability across studies, advancing LMS research and strengthening its role as a valuable addition to the current drug development toolbox and basic cardiovascular research.