Investigating Nanoparticle Distribution and Tissue Architecture in Male and Female Human Cardiac Organoids

Nanoparticles (NPs) are increasingly recognized as vital tools in targeted cardiac therapies, diagnostics, and tissue regeneration. Despite notable advancements, a comprehensive understanding of NP interactions within cardiac tissue as a whole remains limited. In this study, we employ human cardiac organoids derived from induced pluripotent stem cells to investigate NP distribution and colocalization by cardiomyocytes (CMs) and epicardial cells. We also examine the influence of organoid sex on structural organization, biomechanics, and whether such variations impact NP biodistribution and cellular internalization. Using fluorescent polystyrene NPs combined with cryo-electron, confocal, and super-resolution microscopy, RNA sequencing, and atomic force microscopy (AFM), we compare male and female organoids across multiple parameters. Our findings reveal that NPs preferentially accumulate in regions rich in CMs and extracellular matrix, with CMs showing significantly higher colocalization with NPs than epicardial cells. While super-resolution microscopy and AFM analyses demonstrate substantial architectural and mechanical differences between male and female organoids, no significant sex-based differences in NP distribution or colocalization/proximity were observed. Overall, our findings suggest two key points: (i) CMs play a pivotal role in NP-mediated cardiac therapies, and (ii) the development of cardiac organoids should incorporate additional features, such as immune system components, to better mimic native heart tissue. Such advancements would enhance the utility of organoids as robust models for studying drug and NP interactions.