Cardiac spheroids as a human model for inflammation induced cardiac dysfunction

Inflammatory signalling is a major contributor to cardiac dysfunction in diseases such as sepsis, myocarditis, and heart failure, yet existing<i>in vitro</i>models lack the multicellular complexity and physiological relevance needed to accurately recapitulate human cardiac pathology. In this study, we used human cardiac spheroids, three dimensional microtissues composed of cardiomyocytes, fibroblasts, and endothelial cells to study lipopolysaccharide (LPS) induced inflammation. High resolution confocal microscopy confirmed a radial distribution of cell types within the spheroids. Following 24 h LPS stimulation, the spheroids exhibited no significant increase in lactate dehydrogenase release, indicating preserved membrane integrity and absence of overt cytotoxicity. Nevertheless, a robust inflammatory response was observed at both transcriptional and protein levels, including significant upregulation and secretion of TLR2, IL6, TNF, CXCL8, and CCL2. Mitochondrial stress testing revealed significantly reduced basal respiration, ATP production, and maximal respiratory capacity. Functional analyses showed impaired contractility characterized by reduced beat rate, delayed time to peak contraction, and prolonged relaxation time. Together, these findings demonstrate that human cardiac spheroids mount a physiologically relevant, multicellular inflammatory response that compromises both mitochondrial metabolism and mechanical performance. The model offers a powerful platform for investigating innate immune activation and for screening therapeutic interventions targeting inflammation induced cardiac dysfunction.